A Specialist Periodical Report
Organophosphorus Chemistry Volume 8
A Review of the Literature published between July ...
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A Specialist Periodical Report
Organophosphorus Chemistry Volume 8
A Review of the Literature published between July 1975 and June 1976
Senior Reporter S. Trippett, Department of Chemistry, University of Leicester Reporters D. W. Allen, Shefield Polytechnic R. S. Davidson, University of Leicester R. S. Edmundson, University of Bradford J. B. Hobbs, Max Planck lnstitut fiir Experimenfelle Medizin, Gottingen, W, Germany D. W. Hutchinson, University of Warwick R. Keat, University of Glasgow J. A. Miller, University of Dundee D. J. H. Smith, University of Leicester J. C. T e b by, North Stafordshire Polytechnic, Stoke-on- Trent B. J. Walker, Queen’s University of Belfast
0 Copyright 1977
The Chemical Society Burlington House, London, WIV OBN
ISBN : 0 85186 076 1
ISSN : 0306-0713 Library of Congress Catalog Card
No. 73-268317
Printed in Great Britain by Adlard & Son, Ltd. Bartholornew Press, Dorking
Foreword
The volume of published work in organophosphorus chemistry has again increased, and several Reporters have had great difficulty in keeping within their allotted space. Much, but not all, of the research has been of a routine and predictable nature. The stimulus provided by the discovery of phosphonomycin is still being felt. It would be interesting to know just how many research projects and proposals have been linked, however tenuously, to this phosphorus-containing antibiotic. Six-co-ordinate species are being identified more frequentIy. Some are remarkably stable and have been isolated, whereas the intermediacy of others in reactions has been inferred from kinetic data. Clearly, much more will be heard of these. Finally, on the instrumental front, Fourier-transform 31Pn.m.r. spectroscopy is proving to be a very powerful tool for the detection and study of unstable intermediates, for example in Arbusov reactions, and one can look forward to the solution of many long-standing problems in organophosphorus chemistry using this technique. We hope to report on some of these in Volume 9. S.Trippett
Contents
Chapter 1 Phosphines and Phosphonium Salts By D, W. Allen
1
1 Phosphines Preparation From Halogenophosphine and Organometallic Reagents From Metallated Phosphines By Addition of P-H to Unsaturated Compounds By Reduction Miscellaneous Reactions Nucleophilic Attack at Carbon Carbonyls Miscellaneous Nucleophilic Attack at Halogen Nucleophilic Attack at Other Atoms Miscellaneous
1 1 1 2 5 6 8 10
2 Phosphonium Salts Preparation Reactions Alkaline Hydrolysis Additions to Vinylphosphonium Salts Miscellaneous
18 18 21 21 23 25
3 Phospholes
27
4 Phosphorins
29
Chapter 2 Quinquecovalent Phosphorus Compounds By S. Trippetf
10 10 11 12 15 17
31
1 Introduction
31
2 Structure and Bonding
32
3 Acyclic Systems
33
vi
Contents
4 Four-membered Rings
35
5 Five-membered Rings Phospholens 1,2-Oxaphospholans 1,3,2-Dioxaphospholans 1,3,2-Dioxaphospholens 1,3,2-Oxazaphospholidines Miscellaneous
36 36 37 37 39 41 44
6 Six-membered Rings
46
7 Six-co-ordinate Species
46
Chapter 3 Halogenophosphines and Related Compounds By J. A. Miller
50
1 Halogenophosphines Physical and Structural Aspects Preparation Reactions with Simple Alkenes and Aromatic Compounds Reactions in which Phosphorus is Electrophilic Biphilic Reactions Miscellaneous Reactions Silyl- and Related Phosphines
50 50 51 52 53 54 58 59
2 Halogenophosphoranes Physical and Structural Aspects Preparation of Phosphoranes from Phosphorus(rI1) Compounds Preparation of Phosphoranes by Exchange Methods Reactions of Phosphoranes Synthetic Uses of Phosphine-Halogenocarbon Reactions Miscellaneous
61 61
Chapter 4 Phosphine Oxides and Sulphides By J. A. Miller
62 64 65 68 70
71
1 Preparative Aspects
71
2 Addition Reactions of R,P(X)H
76
3 Reactions involving P-C Bond Cleavage
78
4 Reactioirs at X in the P=X Group
79
vii
Contents
5 Reactions of the Side-chain
80
6 Miscellaneous Physical and Structural Aspects
a2
Chapter 5 Tervalent Phosphorus Acids By B. J. Walker
84
1 Introduction
84
2 Phosphorous Acid and its Derivatives Nucleophilic Reactions Attack on Saturated Carbon Attack on Unsaturated Carbon Attack on Nitrogen Attack on Oxygen Attack on Halogen Electrophilic Reactions Rearrangements Cyclic Esters of Phosphorous Acid Miscellaneous Reactions
84 84 84 86 91 92 93 95 97 98 99
3 Phosphonous and Phosphinous Acids and their Derivatives
Chapter 6 Quinquevalent Phosphorus Acids By R. S. Edmundson 1 Synthetic Methods
General Phosphoric Acid and its Derivatives Phosphonic and Phosphinic Acids and their Derivatives
100
102
102 102 104 109
2 Reactions General Reactions of Phosphoric Acid and its Derivatives Reactions of Phosphonic and Phosphinic Acid Derivatives
114 114 117 124
3 Structure
131
Chapter 7 Phosphates and Phosphonates of Biochemical Interest 133 By D. W, Hutchinson 1 Introduction
133
Contents
viii 2 Coenzymes and Cofactors Nicotinamide Nucleotides Flavin Coenzymes Pyridoxal Phosphate Thiamine Phosphates
134 134 135 135 137
3 Sugar Phosphates
137
4 Phospholipids
141
5 Phosphonates
142
6 Oxidative Phosphorylation
143
7 Enzymology Enzyme Mechanisms Miscellaneous Enzymes Phosphoproteins
144 144 146 147
8 Other Compounds of Biochemical Interest
147
Chapter 8 Nucleotides and Nucleic Acids By J. B. Hobbs
151
1 Introduction
151
2 Mononucleotides Chemical Synthesis Cyclic Nucleotides Affinity Chromatography
151 151 158 159
3 Nucleoside Polyphosphates Chemical Synthesis Affinity Labelling Prebiotic Models
1 60 160 165 167
4 OIigo- and Poly-nucleotides Chemical Synthesis Enzymatic Synthesis Sequencing
168 168 171 173
5 Analytical Techniques and Physical Methods Separation and Quantitation Structure Probes
174 1 74 176
Contents
ix
Chapter 9 Ylides and Related Compounds By 0.J. H.Smith
177
1 Methylenephosphoranes Preparation Structure Reactions Aldehydes Ketones Other Carbonyl Compounds Organometallics Miscellaneous
177 177 179 179 179 181 183 184 186
2 Phosphoranes of Special Interest
187
3 Selected Applications of Ylides in Synthesis Heterocycles Pheromones Prostaglandins Carbohydrates Carotenoids Non-Benzenoid Aromatic Compounds
190
4 Selected Applications of Phosphonate Carbanions General Natural Products
199 199 202
Chapter 10 Phosphazenes By R. Keat
190 193 194 195 196 198
204
1 Introduction
204
2 Synthesis of Acyclic Phosphazenes From Amines and Phosphorus(v) Halides From Azides and Phosphorus(n1) Compounds Other Methods
204 204 206 208
3 Properties of Acyclic Phosphazenes Halogeno-derivatives Amino-, Alkyl, and Aryl derivatives
213 213 214
4 Synthesis of Cyclic Phosphazenes
219
Contents
X
5 Properties of Cyclic Phosphazenes Halogeno-derivatives Amino-derivatives Alkoxy- and Aryloxy-derivatives Alkyl and Aryl derivatives
220 220 221 223 227
6 Polymeric Phosphazenes
227
7 Phosphazenes as Fire Retardants
229
8 Molecular Structures of Phosphazenes Determined by X-Ray Diffraction Methods
230
Chapter 11 Photochemical, Radical, and Deoxygenation Reactions 232 By R. S. Davidson 1 Photochemical Reactions
232
2 Phosphinidenes and Related Species
233
3 Radical Reactions
234
4 Deoxygenation and Desulphurization Reactions
240
5 Deselenation Reactions
247
Chapter 12 Physical Methods By J. C,Tebby 1 Nuclear Magnetic Resonance Spectroscopy Biological Applications Chemical Shifts and Shielding Effects Phosphorus-31 8p of PI compounds SP of PI11 compounds 8p of PIv compounds SP of P V and PVI compounds Carbon-13 Hydrogen-1 Studies of Equilibria and Shift Reagents Pseudorotation Non-equivalence,Inversion, and Medium Effects
248
248 248 249 249 249 250 250 252 252 253 253 254 255
xi
Contents
Spin-Spin Coupling JPPand JPM JPC
JPC,H JPNH
JPXCH N.Q.R. Studies
255 256 257 258 259 259 259
2 Electron Spin Resonance Spectroscopy
260
3 Vibrational Spectroscopy Band Assignment and Structure Elucidation StereochemicalAspects Studies of Bonding
262 262 263 264
4 Microwave Spectroscopy
264
5 Electronic Spectroscopy Absorption Photoelectron
264 264 265
6 Rotation
266
7 Diffraction X-Ray Electron
266 266 269
8 Dipole Moments, Permittivity, and Polarography
269
9 Mass Spectrometry
271
10 pKa and Thermochemical Studies
272
11 Chromatography and Surface Properties G.1.c. T.1.c. Paper Chromatography Column Chromatography
274 274 274 214 274
Author Index
276
Abbreviations
ADP AIBN AMP ATP CMP DBN DBU DCC DMF DMSO FAD GDP g.1.c. HMPT HMT NAD NADP NBS NMN n.q.r. PPi TCNE TDAP TFAA THF t.1.c. TMPT UDPGal UDPGlc
adenosine 5’-pyrophosphate bisazoisobutyronitrile adenosine 5’-phosphate adenosine 5’-triphosphate cytidine 5’-phosphate
1,5-diazabicyclo[4,3,O]non-5-ene 1,5-diazabicyclo[5,4,O]undec-5-ene dicyclohexylcarbodi-imide NN-dimethylformamide dimethyl sulphoxide flavin-adenine dinucleotide guanosine 5‘-pyrophosphate gas-liqu id chromatography hexamethylphosphoric triamide hexamethylenetetramine nicotinamideadenine dinucleotide nicot inamideadenine dinucleotide phosphate N-bromosuccinimide nicotinamide mononucleotide nuclear quadrupole resonance inorganic pyrophosphate tetracyanoethylene tris(dimethy1amino)phosphine trifluoroacetic acid tetr ahydrofuran thin-layer chromatography trimethylphosphoric triamide uridine 5’-pyrophosphate galactose uridine 5’-pyrophosphate glucose
t BY D. W. ALLEN
1 Phosphines Preparation.-From Halogenophosphine and Organometallic Reagents. The cyclopentadienylphosphines (1) have been obtained from the reaction of cyclopentadienylthallium with chlorophosphines in ether.l Diphenyl(4-pyridy1)phosphine (2) is prepared from 4-pyridyl-lithium and chlorodiphenylphosphine,2and an improved procedure for the synthesisof tri-(2-pyridyl)phosphine (3) from 2-pyridyl-lithium and phosphorus trichloride has been reported.a
PlpR3-n NSPPh,
(1) R = MeorPh; n = 1 or2
(3)
Treatment of phosphorus trichloride with an excess of the Grignard reagent (4) leads to the sterically hindered phosphine (5).4 A sample of 14C-labelledtriethylphosphine has been synthesized from 14C-labelledethylmagnesium iodide and phosphorus trichloride.6 The reaction of chlarodiphenylphosphine with the Grignard
reagent derived from 2,2’-dibromobibenzyl in THF solution leads to the diphosphine (6),which is dehydrogenated by various rhodium complexes to form trans-2,2’diphenylphosphinostilbene (7).6 1 3 4
5 6
F. Mathey and J.-P. Lampin, Tetrahedron, 1975,31,2685. M. A. Weiner and P. Schwartz, Inorg. Chem., 1975,14, 1714. R. K. Boggess and D. A. Zatko, J. Coordination Chem., 1975,4,217. B. I. Stepanov, A. I. Bokanov, A. B. Kudryavtsev, and Yu. G. Plyashkevich, J. Gen. Chem. (U.S.S.R.), 1975,44, 2312. M. Kanska and S. Drabarek, Nukleonika, 1974, 19,977 (Chem. Abs., 1975,83, 10270). M. A. Bennett, and P. W. Clark, J. Organometallic Chem., 1976,110, 367.
1
Organophosphorus Chemistry
2
.(i) RhI complexes (ii) NaCN ' ~
The reaction of halogenophosphines with esters of trialkylstannylacetic acids gives grouping. Diphosphinoacetic acid esters (8) can be prepared from the monophosphino-esters by treatment with sodium and dialkylchlorophosphines.*
a general route to compounds containing the -P(CH,CO,R)n
From Metallated Phosphines. The synthesis of polymeric tertiary phosphines based on the reaction of lithium diphenylphosphide with chloromethylated polystyrenes continues to attract interest. lo Considerable breakdown of the carbon-carbon back-bone of PVC occurs on reaction with lithium diphenylphosphide in THF, and only oligomers of low molecular weight resulf.ll The potassium salt (9) reacts with chloromethylated polystyrene to form the polymeric diphosphine (lO).la g3
CH,PPh,
/
The cu-chloroalkyldiphenylphosphines(1 1) have been prepared by the reaction of equimolar quantities of sodium diphenylphosphide with ao-dichloroalkanes, Whereas the phosphine (11 ;n = 3) can be converted into the Grignard reagent (12), which reacts with dimethylchlorophosphine to form the unsymmetrical diphosphine (1 3), the Grignard reagent (14) undergoes a B-elimination reaction to regenerate diphenylphosphide i011.l~ M. A. Kakli, G. M. Gray, E. G. Delmar, and R. C. Taylor, Synth. React. Inorg. Metal-Org. Chem., 1975,5, 357. 8 Z . S . Novikova, S. Ya. Skorobogatova, and 1. F. Lutsenko, Russ, P. 497307 (Chem. Abs., 1976, 84, 122038). 9 E. Bayer and V. Schurig, Angew. Chem. Internat. Edn., 1975, 14, 493. lo J. Basset, R. Mutin, G. Descotes, and D. Sinou, Compt. rend., 1975, 280, C , 1181. 11 K. A. Abdulla, N. P. Allen, A. H. Badran, R. P. Burns, J. Dwyer, C. A. McAuliffe, and N. D. A. Toma, Chem. and Ind., 1976, 273. 19 I. Tkatchenko, Compt. rend., 1976,282, C , 229. S. 0. Grim and R. C. Barth, J . Organometnllic Chem., 1975, 94, 327. 7
Phosphines and Phosphonium Salts
3
(11) II = 1-3
n
Yh,P~CHH,-CH,-MgC1
--+
Ph,@ + C,H,
+
[MgCl]’
(14)
Similarly, the chloroalkylarsine(1 5 ) (obtained from lithium diphenylarsenide and 1,Zdichloroethane) reacts with lithium diphenylphosphide to form the mixed phosphine-arsine (16).14 Ph,AsCH2CII,C1
Ph,PLi
*
(15)
Ph, AsCH,CH,PPh,
(16)
Organosilylphosphines are conveniently prepared by cleavage of alkyldiarylphosphines with lithium in THF, followed by treatment with chlorotrimethylsilane,15 and tris(trimethylsily1)phosphine has been prepared from the reaction of chlorotrimethylsilanewith a mixture of sodium and potassium phosphides.ls The product of the reaction between lithium diphenylphosphide (or trimethylsilyldiphenylphosphine)and dimethyl 2,3-dichloromaleate has been shown to be the fumarate (17) l7 and not (as previously supposed)l 8 the expected maleate (1 8).
(17)
(18)
Nucleophilic displacement of halide ion from a saturated carbon atom by alkalimetal diphenylphosphide reagents occurs with inversion of configuration at carbon, as is found in normal sN2 displacements.lBThus menthyl chloride or bromide gives the neo-menthyldiphenylphosphine (1 9). An improved procedure has been reported for the synthesis of the C-functionalized tertiary phosphine (20), based on the reaction of potassium diphenylphosphidewith ethyl chloroacetate.20 K. K. Chow and C. A. McAuliffe, Inorg. Chim. Acta, 1975, 14, 5. R. Appel and K. Geisler, J. Organometallic Chem., 1976, 112, 61. 16 G. Becker and W. Hoelderich, Chem. Ber., 1975,108,2484. 1 7 D. Fenske and J. Lons, Chem. Ber., 1975,108,3091. 18 H. J. Becher, D. Fenske, and E. Langer, Chem. Ber., 1973, 106, 177. 19 A. M. Aguiar, C. J. Morrow, J. D. Morrison, R. E. Burnett, W. F. Masler, and N. S. Bhacca, J, Org. Chem., 1976,41, 1545. 80 T. Jarolim and J. Podlahova, J. Znorg. Nuclear Chern., 1976, 38, 125. 14
15
Organophosphorus Chemistry
4
ClCH,CO,Et
Ph,PK
Ph,PCH,CO,Et
(i) OH-
Ph,PCH,CO,II
(20)
Two reports of the hitherto little documented attack of organophosphide anions on halogen have appeared. Addition of 1,Zdibromoalkenes to lithium diphenylphosphide in THF gives an acetylene and tetraphenyldiphosphine21 (Scheme 1).
- fBr-C=C-Br 'u p&P-+
I 1 R R
0 -+ R C E C R + Ph,PBr
PhzF
Ph,PPPh,
(R = H or Ph) Scheme 1
In the corresponding reactions of o-dihalogenobenzenes, attack on halogen, leading to the generation of benzyne, competes with attack at carbon, leading to the a-halogenophenyldiphenylphosphine (21). Further attack of phosphide on the halogen of the latter gives the anion (22), which on treatment with D,O gives the ortho-deuterated phosphine (23) (Scheme 2). Lithium diphenylphosphidereacts with the benzynefuran adduct (24) to give, after dehydration, a mixture of 1- and 2diphenylphosphinonaphthalenes.22
attackon +
(21) Reagents: i, PhaP-; ii, furan; iii, DaO
Scheme 2 a1 22
D. G. Gillespie and B. J. Walker, Tetrahedron Letters, 1975, 4709. D. G. Gillespie, B. J. Walker, D. Stevens, and C. A. McAuliffe, TetrahedronLetters, 1976, 1905.
Phosphines and Phosphonium Salts
5
By Addition ofP-H to Unsaturated Compounds.This route continues to be exploited for the synthesis of polydentate tertiary phosphine ligands. Thus base-catalysed addition of diphenylvinylphosphine to the secondary phosphine (25) affords (26).23 Neopentylpolytertiaryphosphines, e.g. (27), have been similarly prepared 24 by addition of primary or secondary phosphines to vinylphosphines (or the related phosphine sulphides, followed by a desulphurization step). Me,PCH,CH,P(H) Ph
+
Ph,PCH=CH,
--+
Me,PCII,CH,P(Ph) CH,CH,l’l’h,
(25)
(26) S
11 ,CH=CH,
(Me3CC€1,),PH + Me3CCH,P,
(3 KOBut (ij) Na f.
CH=CH,
/
CH2CH2P(C€1,CMe3),
Me3CCH2P
\CH,CH,I’(CH,CMe,
!,
(27)
Free-radical-catalysed additions have also been reported, and provide a genuine alternative to the more familiar base-catalysed addition routes. Thus the secondary diphosphine (28) readily adds to diphenylvinylphosphinein the presence of AIBN to give (29).2sSimilarly, addition of di(pentafluoropheny1)phosphine to diphenylvinylphosphine affords26 the diphosphine (30). Sequential addition of silanes and secondary phosphines to terminal cto-dienes under the influence of U.V. light affords the silylalkylphosphines (31), which may be anchored via silicon to the surface of inorganic oxides and used as polymeric catalysts.27 PhP(H) (CHz)3P(€~) Ph
+ Ph,PCH=CH,
(28)
AIBN
.
+.
Ph,PCH,CH,P(Ph) (CH,),P(Ph) CII,CH,PPh, (29)
Ph,PCH,CH,P(C, F5)2 (30)
(31) n = 1-4
Addition of P-H bonds to unsaturated systems also continues to be used as a route to heterocyclic systems. Thus base-catalysed cyclization of the phosphine (32) [prepared by the addition of methyl methacrylate (2 moles) to phenylphosphine], followed by subsequent hydrolysis and decarboxylation, affords the phosphorinanone (33). The phosphorinanone system is also directly accessible by the addition of phenylphosphine to divinyl ketones.28 The radical-initiated addition of phenylphosphine to dialkynyl systems (34) gives the heterocyclohexadienes (35).”9 30 The stereochemistry of the addition of phenylphosphine to cyclo-octa-2,7-dienoneto give 23 24
26
26
27
29
3O
R. B. King, J. A. Zinich, and J. C.Cloyd, jun., Inarg. Chem., 1975,14,1554. R. B. King, J. C. Cloyd, jun., and R. H. Reimann, J. Org. Chem., 1976,41,972. D. L. Dubois, W. H. Meyers, and D. W. Meek, J.C.S. Dalton, 1975, 1011. I. Macleod, L. Manojlovid-Muir, D. Millington, K. W. Muir, D . W. A. Sharp, and R. Walker, J. Organometallic Chem., 1975,97, C7. A. A. Oswald, L. L. Murrel, and L. J. Boucher, Preprints Div. Petrol. Chem., Amer. Chem. SOC., 1974,19,155, 162 (Chem. Abs., 1975,83,198225, 1976,84,105 685). I. N . Azerbaev, B. M. Butin, and Y.G. Bosyakov, J. Gen. Chem. (U.S.S.R.),1975,45, 1696. H.0.Berger and H. Noeth, Z . Naturforsch., 1975,30b, 641. G. Markl, D. Matthes, A. Donaubauer, and H. Baier, Tetrahedron Letters, 1975, 3171.
Organophosphorus Chemistry
6 Me0,C
9
C0,Me
I MeCH
CHMe
C0,Me
Me&
KONa+
(i) hydrolysis (ii) -CO,
Me
+
Ph
(33)
R2 R' M
/c-cR2
PhPH:
/-=I
R'M
PPh
both synthe phosphinone (36) has been studied.31Contrary to an earlier and anti-isomers are formed. By Reduction. The first known compounds containing a tervalent phosphorus function and an epoxide ring [(37) and (38)] have been prepared by reduction with phenylsilane of the corresponding phosphine oxides; they are quite stable, showing no
(37) (38) tendency to undergo oxygen transfer to phosphorus, and can be distilled in V ~ C U O The phosphinylacetonitriles (39) undergo selective reduction to the Corresponding phosphinoacetonitriles (40) on treatment with diphenyl~ilane.~~ 0 R,POEt
CICH,CN
+.
II
R,PCH,CN
Ph,SiH2
+ RzPCH,CN (40)
(39)
(K = Et, Pr', But, or Ph)
The isomeric bicyclic phosphines (41) have been obtained by reduction with trichlorosilaneof the related isomeric phosphine oxides, the reaction proceeding with
(41a) 31 32 33 34
(4 1b)
J. R. Wiseman and H. 0. Krabbenhoft, J. Org. Chem., 1976,41, 589. Y. Kashman and E. Benary, Tetrahedron, 1972,28, 4091. C. Symmes,jun. and L. D. Quin, Tetrahedron Letters, 1976, 1853. 0. Dahl and F. K. Jensen, Acta Chem. Scand. ( B ) , 1975,29, 863.
. ~ ~
Phosphines and Phosphonium Salts
7
retention of onf figuration.^^ In contrast, reduction with trichlorosilane of the pure cis- or trans-diazaphospholine oxides (42) gives mixtures of the cis- and transphosphines (43). The lack of stereospecificity is attributed to pseudorotation of phosphorane intermediate^.^^
The A3-phospholen sulphides (44), bearing reactive functional groups, may be reduced to the phosphine using nickelocene in the presence of ally1 iodide.37The intermediate nickel complex is decomposed with cyanide to free the functionalized A3-phospholen (45).
ex
Me
Me Me
Me
Cp,Ni CH,=CHCH,I
~
/ Ph
(44)
/"t
I
PR,
0kh
(45)
-
[X = PhCH(OH), COPh, or C02Et]
A cautionary note has appeared concerning the use of sodium bis(2-methoxyethoxy)aluminium hydride as a reducing agent in phosphorus chemistry. The use of this reagent is severely limited by the enhanced alkylating ability of the ether groups. Thus the reduction of chlorodiphenylphosphine gives a mixture of diphenylphosphine, methyldiphenylphosphine, and 2-hydroxyethyldiphenylpho~phine.~~ Lithium aluminium hydride has been employed in the reduction of the a-phosphinylalkyldiorganostannanes (46) to the phosphines (47), which are useful precursors for the synthesis of heterocyclic compounds containing both tin and phosphorus as ring members.39
(46) (R' = Et or Bu; R2 = EtO or Ph; n = 2or3; X = C l o r B r ) s5
s6 37
38 39
(47) (R' = Et or Ph; R2 = H or Ph; n = 2 or 3)
C. Symmes, jun. and L. D. Quin, J. Org. Chem., 1976, 41, 238. G. Baccolini and P. E. Todesco, J. Org. Chem., 1975, 40,2318. F. Mathey and G. Sennyey, J. Organometallic Chem., 1976,105,13. M. J. Gallagher and G. Pollard, Phosphorus, 1975, 6, 61. H. Weichmann and A. Tzschach, J. Organometallic Chem., 1975, 99, 61.
8
Organophosphorus Chemistry
Miscellaneous. A number of reports of the synthesis of unusual heterocyclic phosphines have appeared. Improved procedures for the synthesis of 1,3,5-triaza-7phospha-adamantane (48) have been r e p ~ r t e d41, ~and ~ ~ the triazaphosphahomoadamantane (49) has also been prepared.42Routes to the large ring phosphacycloalkanes (50) have been described,43and the bicyclic diphosphine (51) has been isolated from the reaction of white phosphorus with o-dichlorobenzene in the presence of transition-metal halidesag4
6;n
N+N
(50)
(R = Ph or PhCH,; n = 3 or 4)
(51)
The heterocyclic acylphosphines (52)and (53) have been prepared by the reaction of phenylbis(trimethylsily1)phosphine with the acid chlorides derived from phthalic and diphenic acids. The reaction of 2,3-dichloromaleic anhydride or thioanhydride with phenylbis(trimethylsily1)phosphine gives derivatives of the 1,4-dihydro-pdiphosphorin system (54).46
0 (5 2)
Ph (5 3)
0 (54)
Ph
0
(X = 0 or S)
&Addition of alkyl cuprate reagents to alkynyl-phosphines occurs to give the vinylphosphines (55).48 40 41 *2 43
44 45
D. J. Daigle and A. B. Pepperman, jun., J. Heterocyclic Chem., 1975, 12, 579. E. Fluck and J. E. Foerster, Chem.-Ztg., 1975, 99, 246 (Chem. Abs., 1975, 83, 97dfi77). D. J. Daigle and A. B. Pepperman, jun., J. Chem. and Eng. Data, 1975, 20, 448. L. Horner, H. Kunz, and P. Walach, Phosphorus, 1975, 6, 63. K. G. Weinberg, J. Org. Chem., 1975, 40,3586. D. Fenske, E. Langer, M. Heymann, and H. J. Becher, Chem. Ber., 1976,109, 35 J. Meijer, H. Westmijze, and P. Vermeer, Rec. Trav. chim., 1976, 95, 102.
.
9
Phosphines and Phosphonium Salts R' R'C
CPPh,
\
(i) R:CuMgX or R'CuBrMgX
(ii) ti+
R' = H o r Me; Rz = Me, Et, Pri, or But The alkynylphosphine (56)reacts with Wilkinson's catalyst to give an intermediate rhodium complex, which, when treated with diphenylacetylene followed by cyanide ion, yields the diphosphine (57), of interest as a rigid chelating ligand of fixed ge~rnetry.~
ti) (Ph,P),RhCl (ii) P h C 3 C P h (iii) CN-
Convenient routes to several new sterically crowded chelating diphosphines have been d e s ~ r i b e d . ~ *Thus, - ~ ~ e.g., rn-xylylene dibromide, on treatment with di-tbutylphosphine,affords a bisphosphonium salt, which on treatment with a weak base affords the diphosphine (58).48 CH,$(H)
Bd Br-
CH,PBU:
acetone
CII,$(H) B< Br-
NaoAc*
CH,PBI~
Rhodium and iridium complexes effect the dehydrogenationof the alkane chain in 1,6-bisdiphenylphosphinohexane to form (after treatment with cyanide ion) 1,6(bisdiphenylphosphino)-trans-hex-3-ene.s1 A new route to compounds claimed to contain the phosphyl P-C linkage has been d e s ~ r i b e dThus, . ~ ~ e.g., cyanogen bromide reacts with phosphine to give (59), which on treatment with isoamyl nitrite gives (60). BrCEN
47 48 49
2 1 -2 2 "C
*
H,N C
PHBr
- A~NO,
5
BrC-P
W. Winter, Angew. Chem. Internat. Edn., 1976, 15, 241. C. J. Moulton and B. L. Shaw, J.C.S. Dalton, 1976, 1020. C. J. Moulton and B. L. Shaw, J.C.S. Chem. Comm., 1976, 365.
so R. Mason, G. Scollary, B. Moyle, K. I. Hardcastle, B. L. Shaw, and C. J. Moulton, J. Organo61 62
metallic Chem., 1976,113,C49. P. W. Clark, J. Organometallic Chem., 1976,110, C13. I. S . Matveev, Khim. Tekhnol. (Kiev), 1974, 49 (Chem. Abs., 1975, 83, 97470).
Organophosphorus Chemistry
10
Reactions.-Nucleophilic Attack at Carbon. (i) Carbonyls. Methyl arylglyoxylates react with trisdimethylaminophosphine(TDAP) to form cis-ccg-dimethoxycarbonylstilbene oxidess3 The initially formed zwitterion (61) reacts with a second molecule of the ester to form a trans-diphenyl-l,4,2-dioxaphospholan intermediate, which undergoes a concerted symmetry-allowed retrograde n2s n4s cycloaddition to give a carbonyl ylide, conrotatory cyclization of which leads to the cis-oxirans (62) (Scheme 3).
+
0-
ArC(0) C0,Me
Me0,C'
I -$ Ar -C-
$(NMe,),
I C0,Me
NMe, Me2N Me,NJP-O Ar CO,hfe Me0,C' 'Ar
I +!, )-
+ (Me,N),PO
0 CO,Me
(62) Reagents: i, (MezN)3P; ii, ArC(0)COaMe
Scheme 3
The 'K-region'-oxirans (63) and (64), of interest in studies of chemical carcinogenesis, have been prepared by cyclization with TDAP of the dialdehydes obtained by oxidative cleavage of the parent hydrocarbon~.~~
The reaction of the phospholen (65) with aromatic acid chlorides in the presence of triethylamine, followed by addition of D20, gives a ready route to aromatic [1-2H]aldehydes with 100% incorporation of d e u t e r i ~ m . ~ ~
53 54 55
G. W. Griffin, D. M. Gibson, and K. Ishikawa, J.C.S. Cliem. Comm., 1975, 595. R . G. Harvey, Swee Hock Goh, and C . Cortez, J. Amer. Chem. SOC.,1975,97, 3468. C . A. Scott, D. G . Smith, and D. J. H. Smith, Synrh. Comm., 1976, 6 , 135.
Phosphines and Phosphonium Salts
11
(ii) Miscellaneous. Nucleophilic attack of dimethylphosphine (or tetramethyldiphosphine) occurs at the terminal olefinic carbon of hexafluoropropene to give a mixture of cis-and trans-dimethylpentafluoropropenylphosphines(66) in proportions which depend on the reaction conditions.s6The products do not arise by dehydrofluorination of a 1:1 adduct.
Further evidence of anchimeric assistance between the oxygen 2p orbitals of the o-methoxyphenyl group and the 3d orbitals of the developing phosphonium centre has been obtained in studies of the rate of quaternization of the phosphine (67). However, the presence at phosphorus of ferrocenyl substituents which are capable of conjugative stabilization of the developing phosphonium centre does not lead to a marked increase in the rate of quaternization of tertiary phosphines [e.g. (68)], supporting the concept that the transition state for the s N 2 reaction of a tertiary phosphine with an alkyl halide lies closer to the reactants rather than to the products in the energy profile diagram.67 Ring opening of diphenylthiiren 1,l-dioxide58 and diphenylcyclopropenonesD occurs on reaction with tertiary phosphines to form the betaines (69) and the keten phosphoranes (70),respectively. Tertiary phosphines react with the thione (71) to form mainly the betaine (72).60 + R,P,
so;
/
Ph/c=c\
Ph
R,P=C(Ph)
-C(Ph)=C=O (70)
(69)
58 57 58 59
6o
P. Cooper, R. Fields, and R. N. Haszeldine, J.C.S. Perkin I, 1975, 702. W. E. McEwen, J. E. Fountaine, D. N. Schulz, and W.4. Shiau, J. Org. Chem., 1976,41, 1684. B. B. Jarvis, W. P. Tong, and H. L. Ammon, J. Org. Chem., 1975, 40, 3189. A. Hamada and T. Takizawa, Chem. and Pharm. Bull. (Japan), 1975,23, 2933. M. G. Miles, J. S. Wager, and J. D. Wilson, J. Org. Chem., 1975, 40, 2577.
12
Organophosphorus Chemistry
Nucleophilic Attack at Halogen. The reactions of tertiary phosphines, in particular triphenylphosphine and TDAP, with tetrahalogenomet hanes continue to attract much interest. Recent progress in understanding the course of the reactions occurring between triphenylphosphine,carbon tetrachloride, and a substrate, and the preparative applications of tertiary phosphine-carbon tetrachloride ‘reagents’, have been reviewed.s1 In reactions employing these reagents, the reactions of the substrate compete with the ‘internal’ reactions of the two-component system, so that the overall course is much more complex than previously assumed. The first isolable product in the reaction of triphenylphosphineand carbon tetrachloride is the salt (73), which reacts rapidly with further phosphine to give the stable phosphorane (74).62In contrast, tris-t-butylphosphinereacts with germanium and tin tetrahalides to form the salts (75);6s compounds of the latter type have long been postulated as arising from the reactions of phosphines with carbon tetrahalides but so far have defied detection. Ph,kCl, C1-
(7 3)
Ph,P
+
Ph,F’=CCCI, + I’h,PCI, J
*I
I’h,P
[But, ;XI MX; (75)
X = Cl or Br M = G e or Sn
[ I’llJ P =c =-PYll,]+ C1
c1-
(74)
Two routes for the reaction of substrate with the triphenylphosphine-carbon tetrachloride reagent are now 62* 64 Direct interaction (76) of the substrate with the initially formed dipolar associate leads to the formation of chloroform and the intermediate phosphonium salt (77).
Direct chlorination of the substrate by the dichlorotriphenylphosphorane present in the reaction mixture competes with the above route. The HCl liberated is taken up by the dichloromethylenetriphenylphosphorane also present to form dichloromethyltriphenylphosphonium chloride (78), which reacts further with triphenylphosphine with the eventual formation of chloromethyltriphenylphosphonium 61 62
R. Appel, Angew. Chem. Internat. Edn., 1975, 14, 801. R. Appel, F. Knoll, W. Michel, W. Morbach, H.-D. Wihler, and H. Veltmann, Chem. Ber., 1976, 109, 58.
63 64
W.-W. du Mont, B. Neudert, and H. Schumann, Angew. Chem. Internat. Edn., 1976,15, 308. 1. Tomoskozi, L. Gruber, and L. Radics, Tetrahedron Letters, 1975, 2473.
13
Phosphines and Phosphonium Salts
J
Ph, P=CM C1 \iii
1[Ph3kH,CI] C1(79) Reagents: i, PhsP; ii, PhsP=CC12; iii, HC1 Scheme 4
chloride (79) (Scheme 4). This route, which does not lead to the formation of chloroform appears to be followed to the extent of 95% in the reactions of enolizable ketones with the triphenylphosphine-carbon tetrachloride reagent.s4 The phosphonium salts (78) and (79) precipitate from the reaction mixtures. Such precipitates observed earlier in other reactions have been referred to as triphenylphosphine oxide and/or triphenylyhosphine hydrochloride without characterization.s6 In spite of the above complexity, exploitation of these reagents in synthesis continues. Thus the triphenylphosphinecarbon tetrachloride combination has been employed as a condensing agent in peptide 6 7 and the TDAP-carbon tetrachloride combination for the synthesis of halogenated and sulphonated carboh y d r a t e ~ .69 ~ ~Other , reactions reported include the use of triphenylphosphinecarbon tetrachloride to chlorinate polyfiydroxyethyl methacrylate) and poly(2hydroxypropyl metha~rylate),~ O and to convert 5‘-alkylthiocarbamates or dithiocarbamates into N-phenylchlorothioformimidates.71Arylhydroxylamines are converted by the triphenylphosphine-carbon tetrachloride reagent into a mixture of the azobenzene and corresponding az~xybenzene.’~ A full report of the reactions of the TDAP-carbon tetrachloride reagent with vicinal diols, to give either trans-epoxides or spirophosphoranes, has appeared.73 The reactions of cro-diols with TDAPcarbon tetrachloride have also been studied 74 and conditions defined for the exclusive formation of monoalkoxyphosphoniumsalts (80), which may then be subjected to a 65
s6 67
69 70
71 72
73 74
N. S. Isaacs and D. Kirkpatrick, J.C.S. Chem. Comm., 1972,443; E. Yamato and S. Sugasawa, Tetrahedron Letters, 1970, 4383; J. B. Lee and T. J. Nolan, Tetrahedron, 1967, 23, 2789. R. Appel, G. Baumer, and W. Striiver, Chem. Ber., 1975,108,2680. R. Appel, G. Baumer, and W. Striiver, Chem. Ber., 1976,109, 801. B. Castro, Y. Chaplew, and B. Gross, Bull. SOC.chim. France, 1975, 875. R.-A. Boigegrain, B. Castro, and B. Gross, Tetrahedron Letters, 1975, 3947. H. I. Cohen, J. Polymer Sci., Polymer Chem. Edn., 1975, 13, 1499. R. Appel and K. Giesen, Chem. Ber., 1976, 109, 810. T. Ohashi and R. Appel, Bull. Chem. SOC.Japan, 1975,48, 1667. R.-A. Boigegrain and B. Castro, Tetrahedron, 1976,32, 1283. R.-A. Boigegrain, B. Castro, and C. Selve, Tetrahedron Letters, 1975, 2529.
14
Organophosphorus Chemistry
range of nucleophilic displacement reactions. Alkylphosphinates (8 1) are formed in good yield by the simultaneous action of alcohols and carbon tetrachloride on chlorophosphines in the presence of an auxiliary base. 75
(80)
iI
= 4-11
(81) R',
R2,K3 = nlkyl
(82)
Applications of the combination of polymer-supported triarylphosphines (82) with carbon tetrachloride for the synthesis of peptides 7 6 and acid ~ h l o r i d e s , ~ ~ involving a simple filtration and evaporation process for product isolation, have been reported. The reactions between PP-diphosphines, carbon tetrachloride, and primary or secondary amines have been studied. In general, diaminophosphonium salts (83) are formed, except for reactions involving sterically hindered aniines, when chloromethylphosphonium salts [e.g. (84)] or methylenebisphosphonium salts [e.g. (85)l
,
[Rii' (N R2R3
1 C1-
*/ Ph,P
(83) R' = Me, Et, PIn, Bun, or 1% R2 = 11, Me, or Et R3 = Et, P r n , Pri, But, or Ph
N(Me) But
+
Me,P -CH2-
el-
\CH,Cl
1
N(Me) Ph
(84)
+
PMe,
I N(Me) Ph
2Cl'
(85)
result. The corresponding reactions of the cyclic diphosphine (86) occur either with ring opening to give (87) or with ring expansion to give (88), depending on the nature of the amine.78 The reactions of cyclopolyphosphines with carbon tetrachloride and with amine-carbon tetrachloride combinations have also been inve~tigated.~~ The rates of dehalogenation of a-bromo- and a-iodo-m-cyanobenzylphenylsulphones (89) by a number of sterically hindered phosphines in aqueous DMF have
2c1-
75
78 77 78
79
R. Appel and U. Warning, Chem. Ber., 1976,109, 805. R. Appel, W. Striiver, and L. Willms, Tetrahedron Letters, 1976, 905. P. Hodge and G. Richardson, J.C.S. Chem. Comm., 1975, 622. R. Appel and R. Milker, Chem. Ber., 1975,108, 2349. R. Appel and R. Milker, 2. anorg. Chem., 1975, 417, 161.
2c1-
Phosphines and Phosphonium Salts
2::s
R,P t X-CHS0,Ph
I
O
C
15 CH,SO,Ph + R,PO + HX
I
O
N
C
N
(89) (X = Br 0x1)
been studied. Variation in the rate data for tri-o-tolylphosphine and tri-o-anisylphosphine is best explained in terms of a steric effect rather than a special electronic effect arising from interactions of the methoxy-group with the phosphonium centre (cf: ref. 57). The use of diphosphines (e.g. 1 ,2-bisdiphenylphosphinoethane),in which a second phosphorus atom might assist in the transition state, produces no special effects. * Nucleophilic Attack at Other Atoms. The adduct (90) from triphenylphosphine and diethyl azodicarboxylate(DAD) catalyses transesterification under neutral and mild conditions (Scheme 5). C0,Et
I
C0,Et
I
.+
/co2Et CH
PhPClz > PhzPCl PCls > EtPClz < EtzPCl
In Scheme 5 the suggested pathway is shown for the conversion of phosphorus trichloride and (48) into the main product, the phosphonate (49). PCl,
+ MeCH(OEt), =+= EtOPCl, + MeCH(C1)OEt (48)
(EtO),PCl
f
MeCH(C1)OEt
0
II
(EtO),PCH(OE t) Me
t
(E tO),P + MeCH(C1) OEt
(49) Reagent: i, (48).
Scheme 5
The iodo-phosphine (50) decomposes at temperatures above -50 "C to give the phosphorane (51).42 Phosphorus trichloride is oxidized by the sulphenyl chloride (52).45 Aryl- and alkyl-dichlorophosphineshave been converted into the phosphor3PhOP1, (50)
-
(PhO),PI, (51) 54%
PCl,
79% S
0
II + CISP(OR),
+ P,J,
pocl,
I1
+ ClP(OR),
(52) 39 40
41 42
43
B. A. Arbusov, N. I. Rizpolozhenskii, A. 0. Vizel, K. I. Ivanovskaya, F. S. Mukhametov, and E. I. Gol'dfarb, Izvest. Akad. Nauk S.S.S.R., Ser. khim., 1971, 117. J. A. Miller and M. J. Nunn, J.C.S. Perkin I, 1976, 535. M. B. Gazizov, D. B. Sultanova, A. I. Razumov, T. V. Zykova, N. A. Anoshina, and R. A. Salakhutdinov, J. Gen. Chem. (U.S.S.R.), 1975, 45, 1670. N. G . Feshchenko and V. G. Kostina, J . Gen. Chem. (U.S.S.R.), 1975,45, 269. N. I. Gusar and M. P. Chaus, J. Gen. Chem. (U.S.S.R.), 1975, 45, 2384.
Organophosphorus Chemistry
58 RPCI, -% RPF,H
R = alkyl or aryl
(53)
anes (53) by an unusual exchange-addition pathway.44Several difluorophosphoranes (54) have been prepared by the reaction of difluorophosphines with hexafluoroacetone.46Details of these reactions appear in Section 2 of this chapter. Tetraiododiphosphine(9) has been used to remove hydroxy-groups from 1,4diols, Yields of 75 % have been obtained as shown in the preparations of (55)15 and in the conversion of chloro-phosphinesinto phosphinates (57), by treatment with an alcohol-base mixture in carbon tetra~hloride.~' OH
OH I
Ph-b.-C=C-&--Ph
I
I
I
PY
(9)
pyridine
*
PY
Ph(py)C-C=C=C(py)Ph (55)
OH
/R
OH 0
RiPC1 + R'OH
-I-CCl,
base
II
+ R:POR2 + HCC1, + R2c1 + HQ
Miscellaneous Reactions.-The reaction of phosphorus trichloride with toluene in the presence of oxygen is known to yield the hydrocarbon (58) and benzylphosphonic dichloride (59).48 The product ratio is now found to be greatly dependent upon the partial pressure of oxygen,"O and earlier views on the relation between the products have been altered. 44 46 46
*7 48 49
R. Appel and A. Gilak, Chem. Ber., 1975, 108, 2693. J . A. Gibson, G.-V.Roschenthaler, and R. Schmutzler, J.C.S. Dalton, 1975, 918. T. Manafusa, S. Imai, K. Ghkata, H. Suzuki, and Y . Suzuki, J.C.S. Chem. Comrn., 1974, 73. R. Appel and U. Warnung, Chem. Ber., 1976,109,805. T . Okada, Y.Okamoto, and H. Sakurai, Bull. Chem. Soc. Japan, 1974,47,2251. Y . Okamoto and H. Sakurai, Bull. Chem. SOC.Japan, 1975, 48, 3407.
Halogenophosphines and Related Compounds
59
0 -
ii
PhMe + PCl, + 0, + PhCH,PC1,
+
PhCH,Ph(Me)
(59)
(5 8)
(60)
A range of reactions of 2-chlorocyclohexyl(dichloro)phosphine (60)with alcohols and epoxides has been described, largely with a view to the synthesis of polymer intermediates and flame-retardant~.~~ The copolymerization of dichloro(pheny1)phosphine with styrene and vinyl butyl ether in the presence of maleic anhydride has been st~died.~' Silyl- and Related Phosphines.-A new preparation of tris(trimethylsily1)phosphine (61) from white phosphorus has been reported.sa Lithium derivatives of (61) may be prepared by cleavage with butyl-lithi~rn,~~ using glyme as solvent. P(white) + Me,SiCl
(Me,Si),P
Na-K
i;g
:CMe,Si),PLi
(61)
A number of exchange reactions of di-t-butyl(trimethylsily1)phosphine (62) have been described.sp-5 They generally involve cleavage of the silicon-phosphorus bond of (62), and a selection is outlined in Scheme 6. Buf,PCl
Me,Sn(PBu',),
+ Me,SiCf
Buf2PSiMe,
Buf,PMCI3 t. Me,SiCI
(62)
But,PGe(C1) Me,
Me,Sn (PBd, ),
Reagents: i, SnC14 (ref. 54); ii, GeCh or SIC14 (ref. 54); iii, MeeSnCl2 (ref. 55); iv, MezGeCh (ref. 56); v, MezSn(C1)PBu'n (ref. 57). Scheme 6 50 51
62 68
54 55 56
57
Ya. A. Levin, M. M. Gilyazov, and E. I. Babkina, J. Gen. Chem. (U.S.S.R.),1975,44,2586. N. D. Kazakova, L. B. Triskina, and S . R. Fafikov, Izuest. Akud. Nuuk Kuzukh. S.S.R., Ser. khim., 1975,25,56. G. Becker and W. Holderich, Chem. Ber., 1975,108,2484. G. Fritz and W. Holderich, 2.anorg. Chem., 1976,422,104. W.-W. Du Mont and H. Schumann, Angew. Chem. Znternat. Edn., 1975,14,368. H.Schumann and W.-W. Du Mont, 2.Nuturforsch., 1976,31b,90. H.Schumann and W.-W. Du Mont, Chem. Ber., 1975,108,2261. H.Schumann, W.-W. Du Mont, and B. Wobke, Chem. Ber., 1976,109, 1017.
Organophosphorus Chemistry
60
Dimethyl(trimethylsilyl)phosphine (63) reacts with aluminium chlorides with cleavage of the silicon-phosphorus bond,68as shown for aluminium trichloride. The same phosphine (63) reacts with the cobalt derivative (64)as shown.6s AICI,
+ Me,SiPMe,
--+
adduct -% (ChAlPMe,),
(63)
I".";;;(coh
(MqSi),$Me,
co(CO),
Diacylphosphines may be prepared by treatment of bis(trimethylsilyl)phenylphosphine (65) with acid chlorides.6oA diphosphine derivative (66) is formed with benzoyl chloride.6O A series of complex reactions occurs between nitrobenzenes and diphenyl(trimethylsily1)phosphine (67).61 The oxides noted below were the only isolable products, and the yields were not high.ll
I
PkP(SiMe,), + 2RCOCl
(PhCOPPh),
(66)
--w
PhP(COR),
+ 2Me,SiCI
(65)
R = H 01 4-Cl
R = 2-(3
Carbonyl-addition reactions continue to be the speciality of the French group interested in germylphosphines. Thus the germaphospholan (68) adds to aldehydes to give diastereomeric products (69).62Steric factors are believed to control the mode
3
Me,Ge Ph
+ RCHO
* O-CHR
of 1,4-addition of various Group IV phosphines to orp-unsaturated carbonyl compounds, while hard-soft interactions are suggested to determine the balance between 1,2- and 1,4-additi0n.~~ 59 6o
61 62
63
G. Fritz and R. Emul, 2. anorg. Chem., 1975,416, 19. H. Schafer and A. G. MacDiarmid, Znorg. Chem., 1976,15, 848. D. Fenske, E. Langer, M. Heymann, and H. J. Becher, Chem. Ber., 1976,109, 359. D. Fenske, H. Teichert, and H. J. Becher, Chem. Ber., 1976, 109, 363. C. Couret, J. Escudie, J. Satge, and G . Redoules, J. Organometallic Chem., 1975,94, C35. C. Couret, J. Escudie, J. Satge, N. T. Anh, and G . Soussan, J. Organometallic Chem., 1975,91, 11.
Halogenophosphinesand Related Compounds
61
Addition reactions of silylphosphinesto imines have been reportedYs4 as illustrated for diethyl(trimethylsily1)phosphine (70). Organic azides react with germylphosphines by an insertion pathwayYB5 as shown for various phenyl(trimethy1germyl)phosphines (71). The initial products (72) isomerize to phosphine imines on heating.65
\
M%SiPEt, + C=NR (70) / Me,GeP(R‘)Me
(71)
+ RaN,
-
1
Me,SiN(R)CPEt,
I
Me,GeN(Ra)P(R’)Me
6 Me,GeP(R’) Me
ll
(72)
NR’
2 Halogenophosphoranes Physical and Structural Aspects.-Fluorophosphoranes (73) feature prominently in an extensive ab initio SCF study of the bonding in fluoro-derivatives of Group V elements.66Using different basis sets, the authors have demonstrated, yet again, the energetic benefits of including d-orbitals.66A somewhat different application of MO methods has been reported by Howell,67 who has used extended Huckel and CNDO/2 calculations to probe the structural changes in phosphorus pentafluoride (73; n = 0) as the fluorine nuclei are replaced by hydrogen or by methyl groups. In particular, the relatively greater stretching of axial P-F bonds (relative to equatorial P-F) experimentally observed for a number of substituted fluorophosphoranes has been ascribed to a repulsive interaction between the equatorial a-bonds and the axial lone pair of fluorine.67 The question of the energetics of trigonal-bipyramidal (TBP) as against squarepyramidal (SP)structures has been analysed for phosphoranes in which phosphorus is incorporated into a five-membered (or smaller) ring.68Holmes has discussed the importance of the difference between axial and equatorial bond lengths to phosphorus, in a TBP structure, and shown that this induces significant ( 3 - 4 kcal mol-l) strain when the phosphorane possesses an unsaturated five-membered ring bonded by electronegative elements to the phosphorus.68This effect is likely to be enhanced
(74) R = F (75) R = Me 6* 65 66 67 68
Br (76)
C. Couret, F. Couret, J. Satge, and J. Escudie, Helu. Chim. Acta, 1975, 58, 1316. J. Escudie, C. Couret, and J. Satge, Compt. rend., 1975, 280, C, 783. F. Keil and W. Kutzelnigg, J. Amer. Chem. SOC.,1975, 97, 3623. J. M. Howell, J. Amer. Chem. SOC.,1975, 97, 3930. R. R. Holmes, J. Amer. Chem. SOC.,1975,97, 5379.
62
Organophosphorus Chemistry
for four-membered rings, and for bicyclic structures, and is thus in accord with recent observationsQ0 of square-pyramidalgeometry for the structures (74), (75), and (76). Gas electron-diffractionstudieson the phosphoranes(77)and (78)have revealed that the former has a regular TBP structure with axial CFI groups, while the latter has a distorted TBP
(CF,), PC1 -,
Cl,PCH=C(Mc)
N,=C=O
(79)
(77) n = 2 (78) n = 3
Stability calculationson the phosphoranes (79)have appeared.71Various potential functions for phosphorus pentafluoride (73; It = 0) have been r e ~ o r t e d An .~~~~~ e.s.r. study of y-irradiated phosphorus pentachloride has been published.74 New thermochemical data on phosphorus pentabromide have appeared.75 Preparation of Phosphoranes from Phosphorus(II1) Compounds.-Benzoylphosphoranes have been made from xenon difluoride, as shown for (80).76The barrier to rotation of the benzoyl group in (80)is found to be below 8 kcal mol-l, although 0
IIIt PhCPMe, + XeF,
F _t
F
evidence was obtained that at - 100 "C the benzoyl group preferred to be in the equatorial plane. Spirophosphoranes bearing a benzoyl group at phosphorus have been prepared as shown for (81), and an n.m.r. method has been used to estimate the barrier to axial placement of the benzoyl The value of AGS (20.9 kcal 6g
70
71 79
73
'*
75
76
For a recent discussion see R. R. Holmes, J. Amer. Chem. Suc., 1974, 96,4143. H. Oberhammer and I. Grobe, 2. Nuturfursch., 1975, 30b,506. A. A. Kisilenko, Yu. P. Egorov, E. A. Stukalo, and L. N. Markovskii, J. Gen. Chem. (U.S.S.R.), 1975,45, 1688. L. S. Bernstein, J. J. Kim, K. S. Pitzer, S. Abramowitz, and I. W. Levin, J. Chem. Phys., 1975, 62, 3671. L. S. Bernstein, S. Abramowitz, and I. W.Levin, J. Chem. Phys., 1976, 64, 3228. S. P. Mishra and M. C. R. Symons,J.C.S. Dalton, 1976, 139. A. Finch, P. J. Gardner, P. N. Gates, A. Hameed, C. P. McDermott, K. K. Sengupta, and M. Stephens, J.C.S. Dalton, 1975, 967. S. Trippett and P. J. Whittle, J.C.S. Perkin I, 1975, 1220.
Halogenophosphines and Related Compounds
63
mol-l) suggests that the benzoyl group has an apicophilicity comparable to that of the phenoxy-group. Details 77 have appeared of the synthesis of fluorophosphoranes containing fourmembered rings,78 and extensive variable-temperature n.m.r. studies have been described. Thus, for the phosphorane (82), the most stable conformations are (83) and (84), which inconvert to a minor conformer (85), via the intermediate (86).77
This work provides further evidence that axial placement of phenyl accompanied by equatorial placement of fluorine is costly in energy, while diequatorial siting of a fourmembered ring containing only carbon and phosphorus is considerably easier.7 7 Preparative details and extensive Lr., n.m.r., and mass spectra have been described for the phosphoranes (87)?6 These phosphoranes have a TBP structure, and for (87a)-(87c) their n.m.r. spectra are temperature-independent, and indicate that the fluorines bonded to phosphorus are equivalent. The authors have suggested an explanation based on rapid intramolecular isomerization, and discussed the possibility that a facile TR pathway exists for this process.46Octahedral adduct formation between (87) and fluoride ion or trimethylphosphine has also been de~cribed,*~ as shown in (88).
(87) a; R Me b; R = But
c;R=F%
-
d; R = F e; R NEt, f ; R = N(SiMe3),
(88)
Allyltrifluorophosphorane(89) may be prepared as shown, and the n.m.r. spectrum of (89) indicates a TBP structure.21A similar route has been used to prepare the analogous arylphosphoranes (go), which have been found to be quite stable, and
RPBr, + 3HF
*
“-J-R FI‘
F
(89) R = ally1 77 78
RPCL,
+ 3HF
RP(F,)H (90) R = aryl or alkyl
N. J. De’ath, D. B. Denney, D. Z. Denney, and Y.F. Hsu, J. Amer. Chem. SOC.,1976,98,768. N. J. De’ath, D. Z . Denney, D. B. Denney, and C. D. Hall, Phosphorus, 1974,3 205.
64
Organophosphorus Chemistry
isolable in good yields.44The novel di-iodophosphorane (51) has been isolated; see Section 1. Addition of chlorine to tris(amin0)phosphines has been used to prepare the dichlorophosphoranes (91), although the corresponding reaction of dialkylaminoAnalytical data, but no (dipheny1)phosphines (92) gave less stable spectra, have been described for (91).79
Preparation of Phosphoranes by Exchange Methods.-A convenient procedure has been developed for the one-step synthesis of chlorotetrafluorophosphorane(93).** The phosphorane (94) has been prepared as shown.s1Ring opening of the disilacyclobutane (95) by phosphorus pentafluoride affords the bisphosphorane (96), characterized by its spectra.82
Details have been published of the synthesis and spectra of a wide range of monoalkoxyphosphoranes (97), prepared by the silane-exchange method as The 19Fn.m.r. compilation on these phosphoranes is very impressive, and their structures
F MePF,
+ ROSiMe,
M e .. _+
I
Ro'T-F F (97)
79
8o
81 82
83
R*OP(R) F,
Bu*PF,
Et(Ph)PF,
(98) R* = chiralalkyl
(99)
(100)
A. M. Pinchuk, A. P. Marchenko, I. N. Zhmurova, and A. P. Martynyuk, J. Gen. Chem. (U.S.S.R.), 1975, 45, 1002. R. H. Neilson and A. H. Cowley, Znorg. Chem., 1975,14,2019. H. B. Stegmann, H. V. Dumm, and K. B. Ulmschneider, Tetrahedron Letters, 1976, 2007. W. Althoff, M. Fild, H. Koop, and R. Schmutzler, J.C.S. Chem. Comm., 1975,463. J. G. Riess and D. U. Robert, Bull, SOC.chim. France, 1975, 425.
Halogenophosplzines and Related Compounds
65
have been discussed in terms of TBP geometry for structures undergoing BPR isornerizati~n.~~ The same group have provided further n.m.r. data on a large number of alkoxyfluorophosphoranes(98), in which the fluorines are non-equivalent due to a chiral centre in the alkyl group of (98).84The phosphoranes (99) and (100) have been prepared for the first time.84 Reactions of Phosphoranes.-The reactions of phosphorus pentachloride (101) with simple organic molecules continue to attract attention, notably in the Russian literature. For example, the preparative uses of alkene-addition reactions of (101) have been examined for a-methylstyrene (102), as outlined in Scheme 7.85
a y p M” e>CHp
pcZ + PhC(Me)=CH,
&
-% Me\/C=CHPC1,
cl P(mHaCWV,
Ph (101)
-P(OR),
(102)
-
Reagents: i, mix reactants; ii, PCb-Sb; iii, /-\;iv, 2 ‘ O / ; v, ROH-base.
Scheme 7
Kinetic studies of alkenephosphorus pentachloride reactions in benzene show the effects of substituents when the double bond is terminal.86When the alkene is conjugated, the standard work-up conditions (using sulphur dioxide) produce alk-lenylphosphonyl dichlorides (103), instead of 2-chloroalkylphosphonyl dichlorides (104). 0
0
RCH=CH,
+ pcz
wo~:up
(101)
+
II RCH-CHPCL, (103)
R = arylor
ll
or RCHC~CH~FQ (104)
R = -1
alkenyl
Me
I &COH
+ pcZ (101)
(1W 84 85 86
-+
a 0 I II
&CCHPc1, (18%) (105)
(retained confguration)
D. U. Robert, D. J. Costa, and J. G. Riess, Org. Magn. Resonance, 1975, 7 , 291. V. V. Konnachev, L. V. Krylov, and V. A. Kukhtin, J. Gen. Chem. (U.S.S.R.), 1975,45,2327. V. G. Rozinov. V. V. Rybkina, E. F. Grechkin, and A. V. Kalabina, J. Gen. Chem. (U.S.S.R.), 1975,45, 1609.
V. G. Rozinov, V. V. Rybkina, E. F. Grechkin, and A. V. Kalabina, J . Gen. Chem. (U.S.S.R.), 1975,45, 1610.
Organophosphorus Chemistry
66
The formation of 2-chloroalkylphosphonyldichlorides (105) from tertiary alcohols and (101) has been ascribed to the intermediate formation of alkenes, as showmas Tertiary alcohols are chlorinated by (101), in a mild, efficient procedure which usually occurs with retention of config~ration,~~ as for (106). The reaction between benzyl cyanide (107) and phosphorus pentachloride (101) has been shown to be dependent on both solvent and t e m ~ e r a t u r e .This ~ ~ allows a rationalization of the century-old result of C l a i ~ e nwho , ~ ~isolated the gem-dichloride (108) from this system, while later workers O2 obtained the phosphorimidic derivative (109) instead. The present studyg0describes the isolation of (110), an intermediate in the formation of (109), and distinguishes conditions leading to (110) from those producing (108).
Several papers have been devoted to the subject of reactions of phosphoranes with carboxylic acids and their derivatives. Thus triphenylphosphine dibromide (1 11) in acetonitrile cleaves lactones,03 while the corresponding dichloride (1 12) converts esters into acid chlorides.94 The reactions of esters with phosphorus pentachloride (101) have been studied further,95and the influence of structural changes on the yields of products (1 13) and (1 14) has resulted in minor modifications to the mechanism previously 96 outlined. Ph,PBr2
(111)
+
0
0
:
("' C0,Me
Phosphorus pentachloride (101) chlorinates amides, and the products (1 15) can be reductively dehalogenated with sodium borohydride, thus providing a two-step V. V. Moskva, L. A. Bashirova, A. I. Razumov, T. V. Zykova, and R. A. Salakhutdinov. J. Gen. Chem. (U.S.S.R.), 1974, 44, 2573. 8 9 R. M. Carman and I. M. Shaw, Austral. J. Chem., 1976, 29, 133. N. D. Bodnarchuk and V. I. Kal'chenko, J. Gen. Chem. (U.S.S.R.),1975,45, 1007. 91 L. Claisen, Ber., 1879,12, 626. 92 E. Fluck and W. Steck, Phosphorus, 1972, 1, 283. 93 E. E. Smissman, H. M. Alkaysi, and M. W. Creese, J. Org. Chem., 1975, 40, 1640. 94 D. J. Burton and W. M. Koppes, J. Org. Chem., 1975,40, 3026. 95 V. V. Moskva, V. M. Ismailov, S. A. Novruzov, A. I. Razumov, T. V. Zykova, Sh. T. Akhmedov, and R. A. Salakhutdinov, J. Gen. Chem. (U.S.S.R.),1974, 44, 2574. g6 V. V. Moskva, V. M. Ismailov, S. A. NOVNZOV, A. I. Razumov, T. V. Zykova, Sh. T. Akhmedov, and R. A. Salakhutdinov, J. Gen. Chem. (U.S.S.R.),1973, 43, 2071. 88
Halogenophosphinesand Related Compounds
67
conversion of amides into amines.97 The stepwise chlorination of N-cyclohexylacetamide (116) by phosphorus pentachloride (101) has been studied as a model for acetamido-s~gars.~~ Phosphorus pentachloride (101) and tfiethylamine cyclize the amide (117).O@ 0
II
RTH,CNR:
('01) :
R'CH=C(CI)NR;
NaBH,
RICH,C&NR~
OEt PCI,
NHCOPh
+ Et,N
EtOH
+ HCIL
Cyclic 1,3-diketones have been converted into p-halogeno-ketones (1 18) by triphenylphosphine dihalides in benzene or acetonitrile,lOO although this paper adds little to previous work lol in this field. The reactions of phosphorus pentachloride with acetals have been extended to mixed acetals, such as (119).loaOnly one product
(118) X = C1,91%
,OEt MeCH 'OPI'
(i) PCI, (101) (ii) SO,
0 i~
II
PCH=CHOP~~ 82%
(119) A. Rahman, A. Basha, N. Waheed, and S. Ahmed, Tetrahedron Letters, 1976, 219. A. M. Dempsey and L. Hough, Carbohydrate Res., 1975,41, 63. gs B. S. Drach and 0. P. Lobanov, J. Gen. Chem. (U.S.S.R.),1974,44,2730. looE. Piers and I. Nagakura, Synth. Comm., 1975, 5, 193. 101 J. A. Miller in 'Organophosphorus Chemistry', ed. S. Trippett, (Specialist Periodical Reports), The Chemical Society, London, 1973, Vol. 4, pp. 65, 66. 102 V. V. Moskva, T. Sh. Sitdikova, A. I. Razumov, T. V. Zykova, R. A. Salakhutdinov, and G. F. Nazvanova, J. Gen. Chem. (U.S.S.R.),1975,45, 1462. 97
98
Organophosphorus Chemistry
68
is obtained in this reaction, in good enough yield to suggest that this type of transformation may yet be of general synthetic utility. Synthetic Uses of Phosphine-Halogenocarbon Reactions.-This is a field which has attracted an increasing amount of effort in recent years, largely due to the extensive studies by Appel and his colleagues. Much of this work is summarized in a review lo3 which covers the principles and synthetic applications of reactions involving a tertiary phosphine and carbon tetrachloride. Despite the interest generated by this work, little is known about the mechanistic aspects of these reactions, although one might not appreciate this from some of the current papers in the area. This year has witnessed three independent attempt^^^^-^^^ to rectify this situation, and overall a fair measure of agreement can be seen in the conclusions. The first paperlo4is devoted to a study of the intermediates formed in reactions of triphenylphosphinecarbon tetrachloride with compounds possessing acidic hydrogens. Thus the initial interaction of triphenylphosphine (120) with carbon tetrachloride yields the ylide (121) and the phosphorane (112), which, in the presence of protic species (such as ROH in Scheme 8), react further to give the salt (122) and triphenylphosphine oxide. A recycling sequence then converts (122) into the dehalogenated salts (123) and (124), respectively,lo4as shown in Scheme 8. 0 2Ph,P + CCl, --+
(120)
II
Ph,P + Ph3$CHC1, Cl- + RC1
Ph,PCl, + Ph,P=CCl,
(1 12)
(121)
(122)
0
(122) + Ph,P
_.)
II f
A Ph,P
Ph,PCl, + Ph,P=CHCl (112)
Ph,kH,ClCl-
+
RC1
(123)
0
(123)
+
II
Ph,P -k ROH -+ Ph,P + Ph,kH,
a + RCl
(124) Reagent: i, ROH.
Scheme 8
Of these steps, the last is often not observed in practice, although the authors have demonstrated its efficiency by treating triphenylphosphine (120) and the salt (123) with cyclohexan01,1~~ to give the products indicated in Scheme 8. A related studylo5 using dibromodifluoromethane (125) gave similar results, although the authors concentrated on demonstrating the equilibrium between the salt (126) and the derived ylide. The species involved in this equilibriumlo5were either isolated or trapped, as shown by the dotted arrows. R. Appel, Angew. Chem. Internat. Edn., 1975, 14, 801. I. Tomoskozi, L. Gruber, and L. Radics, Tetrahedron Letters, 1975, 2473. lo5 D. G. Naae, H. S. Kesling, and D. J. Burton, Tetrahedron Letters, 1975, 3789. l 0 6 R. Appel, F. Knoll, W. Michel, W. Morbach, H.-D. Wihler, and H. Veltmann, Chem. Ber., 1976,109, 58. 1°3
lo4
69
Halogenophosphines and Related Compounds 2Ph,P + CF,Br,
T Ph,kBrF, + Ph,P -xel+ salt (85%)
Br-
(125)
The third paper in this group106is concerned with the isolated triphenylphosphinecarbon tetrachloride system, and the authors show how these compounds react only in the presence of small amounts of polar impurities, to produce initially the salt (127), which is rapidly converted into (121), as shown in Scheme 8. In the absence of protic material, the ylide (121) reacts further,loSas shown.
Ph,hC(Cl) =PPh,
C1'
Preparative applications of these reactions have included work on peptide synthesis from amino-acids (suitably protected) using triphenylphosphine(120) lo8 or a polymer-bound aryldiphenylphosphine (128).lo9Coupling is generally very efficient,lo7but racemization problems occur in some reactions.1o8,logA typical coupling reaction using (128) is outlined in Scheme 9.
R2
R' polymer
...ArPPh,
I
+ ZHNCHC0,H + HzNd€IC.O2R3,HX
(128)
R'
I
R2
I
ZHNCHCONHCHC02R3
(70-76s) Reagent : i, CC14-EbN.
Scheme 9 R. Appel, G. Baumer, and W. Struver, Chem. Ber., 1975, 108, 2680. R. Appel, G. Baumer, and W. Struver, Chem. Ber., 1976, 109, 801. lo* R. Appel, W. Struver, and L. Willms, Tetrahedron Letters, 1976, 905. 1°7
70
Organophosphorus Chemistry
Other 110-114 synthetic uses of these reactions are summarized in Scheme 10. 0
0
R,POH
(&P)zO
II
I1
ref. 110
(PhP), + CCI, -+ PhP(Cl)CC13
ref. .111
70%
(RP),
+
cct
--
R -- cyclohesyl
R~PPR: + 3 c c 4 + SR:NH
~
RP(Cl)P(CCl,) R
R$(NR;),cI-
ref. 111 ref. 112 ref. 113
X X = lonepairandx = 0 Ph,P + HXPh & Ph,$XPh Cl'(97%)
ref. 114
X = OorS Reagents: i, Ph3P-CCLP-Et3N; ii, CCL-EtaN.
Scheme 10
Miscellaneous.-Hydridofluorophosphates have been prepared for the first time, and the anion (129) has been found to have an octahedral structure, with hydrogens trans.l15 Phosphorus pentafluoride forms an adduct with biscyclopentadienyl titanium difluoride.lleThe phosphorane (1 30) has been prepared as ~h0wn.l~'
Mi
110
113 114 115 116 117
R. Appel and H. Einig, Z . anorg. Chem., 1975, 414, 236. R. Appel and R. Milker, 2. anorg. Chem., 1975,417, 161. R. Appel and R. Milker, Chem. Ber., 1975, 108, 2349. T. Ohashi and R. Appel, Bull. Chem. SOC.Japan, 1975,48, 1667. R. Appel, K. Warnung, and K.-D. Ziehn, Annalen, 1975,406. K. 0. Christe, C. J. Schack, and E. C. Curtis, Inorg. Chem., 1976, 15, 843. H. C. Clark and A. Shaver, J. Coordination Chem., 1975,4, 243. E. S. KOZIOV, S. N. Gaidamaka, and L. I. Samarai, J. Gen. Chem. (U.S.S.R.),1975, 45, 458.
4 Phosphine Oxides and Sulphides BY J. A. MILLER
1 Preparative Aspects Reviews have appeared on synthetic uses of a-diazoalkylphosphoryl compounds,1 and on the synthesis and complexing properties of alkylenediphosphine dioxides2 The diversity of the reactions of a-diazoalkylphosphineoxides is further demonstrated by work from Regitz's Treatment of diazomethyldiphenylphosphine oxide with aldehydes yields the oxides (l), which have been converted into a range of other oxides3as shown. 0
0
II
I1 PbPC(N,) CH(0H)R
RCHO 7
0
=- PbPCHR CHO
0
ll Ph,PCH$OR
I1
WPC-CR
0
II
Compounds possessing a 'PH
/
part-structure undergo a general condensation
reaction, leading to a-aminoalkylphosphorylproducts (2), with amines and carbonyl compounds. A critical analysis of previous mechanistic interpretation of this reaction has a ~ p e a r e dEarly . ~ study of such systems has suggested6that a-hydroxyalkylphosphoryl intermediates were involved (path a), although an attractive alternative view was that a-amino-alcohols were involved (path b), as shown in Scheme 1. The present work4 confirms that path b holds for R = CH,Ph or OBun. Although the first step of path a is fast for R = CH2Ph, it is easily reversed as the temperature is increased, and path b is still the predominant route to (2). 1 2
5 6
M. Regitz, Angew. Chem. Internat. Edn., 1975, 14, 222. T. Ya. Medved, Yu. M. Polikardov, L. E. Bertha, V. G. Kossykh, K. S. Yudina, and M. I. Kabachnik, Rum. Chem. Rev., 1975,44,468. W. Disteldorf and M. Regitz, Chem. Ber., 1976, 109, 546. K. A. Petrov, V. A. Chauzov, and T. S. Erokhina, J. Gen. Chem. (U.S.S.R.),1975,45, 727. M. 1. Kabachnik and T. Ya. Medved, Doklady Akad. Nauk S.S.S.R., 1952,83,689; 1952,84, 717. E. K. Fields, J. Amer. Chem. SOC.,1952,74, 1528.
71
72
Organophosphorus Chernistry 0
II I I
R;P -COH P a t h y
R'
\II PH + \C=O /
R'.
+
/
R2NH,
\
path h
OH
0
II
\I C-NRZ ' I H
I I
GP-CNHR~ (2 1
0
I1
Reagents: i, R2NH2; ii, RiPH
Scheme 1
Ferrocenylphosphines and their oxides (3) have been prepared by standard routes,' and the properties of diferrocenylphosphine oxide (3; n = 2) reported.8 Derivatives of diphenyl(ferrocenylmethy1)phosphine oxide (4) have been prepared by a metallation-alkylation ~equence,~ as shown for the oxide (5). 0
(i) BuLi X 2 (ii) BrCH,CH,Br
II PhzPCH2Fc
0
(4 1
(3) F c = ferrocenyl
Fc (5 1
MePC1,
(i) (ii) MeOH b
Q
+
/ \ Me 0
Q
/ \ Me
0
Synthetic studies of various cyclic phosphine oxides continue to be published. Thus a methanolic work-up leads to an 88% yield of 1-methylphospholen 1-oxides (6) from dichIoro(methyl)phosphine, and detailed slP n.m.r. and mass spectra have been described.l O The oxides (7)and (8) have been prepared l1 as shown. Structural
*
A. N. Nesmeyanov, V. D. Vil'chevskaya, A. I. Krylova, Yu. S. Nekrasov, and V. S. Tolkunova, Bull. Acad. Sci., U.S.S.R.,1975, 706. A. N . Nesmeyanov, V. D. Vil'chevskaya, A. 1. Krylova, and V. S. Tolkunova, Bull. Acad. Sci.,
U.S.S.R.,1975, 1710. G. Marr, B. J. Wakefield, and T. M. White, J. Organometallic Chem., 1975,88, 357. lo K. Moedritzer, Synth. React. Inorg. MetaLOrg. Chem., 1975, 5, 299. l1 F. Mathey and D. Thavard, Compt. rend., 1975,281, C , 243.
73
Phosphine Oxides and Sulphides
studies have appeared on the products (9) formed by cycloaddition of phenylphosphine to the dienone (10).l2Recent years have seen a number of preparations of A2-phospholenl-oxide (11) based on enone additions, and this type of reaction has now been directed towards the synthesis of heterocyclic ~ter0ids.l~
Ph
-0
+
*
PhPH,
+ epimer
0
d
0
‘Rl
(11)
Polyphosphoric acid (PPA) (115 %) has been used in a very convenient preparation of phosphindoline l-oxides and phosphinoline l-oxides by cyclization of various alkenylphosphine oxides (12).14 Isophosphindole oxide (13) has been preMe
1
Ph,PR (12)
R = 180°C 115% PPA
(
ally1
\
R = crotyl or R = but3-eny1
Me I
J. R. Wiseman and H. 0. Krabbenhoft, J. Org. Chem., 1976,41, 589. R. Bodalski, K. M. Pietrusiewicz, and J. Koszuk, Tetrahedron, 1975, 31, 1907. l4 M. El-Deek, G. D. Macdonell, S. D. Venkataramu, and K. D. Berlin, J. Org. Chem., 1976,41, la
1403.
Organophosphorus Chemistry
74
Ph
H
Reagents:. i, NBS; ii, base; iii, MeO,CC=CCO,Me;
iv,
0
; v,
-
Scheme 2
pared as shown in Scheme 2, and Diels-Alder adducts have been obtained with a number of dienophiles.ls Epoxidation of 1-methyl-As-phospholen 1-oxide (6b) yields essentially one isomer (Scheme 3), whose stereochemistry has been confirmed by 13Cn.m.r. studies.16
u -0
/ \Me 0
perocid
~
//
0
’\\
Me
(6b) Scheme 3
Various &substituted vinylphosphine oxides (14) have been made by the Wittig route, and found to be trans-isomers.’? The geometry of these oxides is believed to be 0
0
0
ll II Ph,PCH,P(OPh), + RChO
Wittig k
It
Ph,PCH=CHR
determined by steric effects operating in the transition state for the cyclization step.17 Polyene formation by Wittig reactions of the oxide (15) has been described (Scheme 4).18 l5 l*
l8
T. H. Chan and K. T. Nwe,Tetrahedron, 1975, 31,2537. C. Symmes and L. D. Quin, Tetrahedron Letters, 1976, 1853. D. Gloyna, K. G. Bernot, H. Koeppel, and H. G. Henning, J. prakt. Chem., 1976,318,327. B. Lythgoe, T. A. Moran, M. E. N. Nambudiry, S. Ruston, J. Tideswell, and P. W. Wright, Tetrahedron Letters, 1975, 3863.
75
Phosphine Oxides and Sulphides
Reagents: i, C l d C O C l ; ii, Ph,PLi; iii, H,O,;, iv, Wittig reaction '
Scheme 4
Perfluoroalkylphosphine oxides have been reported to show some interesting surface-active properties. Examples of the synthesis of such oxides are given for (16) and (17).la The oxides (18)*O and (19)21have been prepared by standard routes.
R
0
I1
Me,PH + CH,=CHR,
Me,PCH(Me)R,
*IBN*
RF = perfluoroalkyl Ph,kH=CHCOMe
+' (16)
(17)
:;$+
Ph,PCH(Ph) CH,COMe (18)
Ph,POEt + CH,-CHCH,Br \
/
_j.
(19) 25%
' 0 '
Details have appeared of the conversion of chiral phosphine sulphides (20) into the corresponding inverted oxides, and a rationalization of the stereochemistry has been
S
11
Ph,PSR (22)
(i) BuLi (ii) MeI+
S
11 Pb,PMe
+ RSBu
Ph,PPPh,
(21)
(i) R ~ M Q (ii) S,
*
S
II
PbPC(R)Me, (23) R = CN (24) R = C0,Me
Is
M. Demarcq and J. Sleziona, J. Fluorine Chem., 1975, 6, 129.
20
M. M. Shevchuk, S. T. Shpak, and A. V. Dombrovskii, J. Gen. Chem. (U.S.S.R.),1975, 45, 2 109. A. P. Rakov, E. A. Kosterin, and G . F. Andreev, J. Gen. Chem. (U.S,S,R.), 1975, 45, 1726.
2l
76
Organophosphorus Chemistry
suggested.22An unusual preparation of phosphine sulphides (21) from the phosphinodithioates (22) has been d e s ~ r i b e d The . ~ ~ authors provide evidence that the metal alkyl attacks the ester (22) at sulphur, and that the formation of (21) is the result of a subsequent a l k y l a t i ~ n .The ~ ~ sulphides (23) have been prepared from tetraphenyldiphosphine (24).24 2 Addition Reactions of R,P(X)H The confusing subject of a-keto-phosphine oxides has entered the literature again. Thus the group which originally misassigned the structure of the product formed by trifluoroacetic acid and chlorodiphenylphosphine (25) has now agreed 2s with the revised structure (26) suggested last year.26The key step in the formation of (26) is believed to involve addition of diphenylphosphine oxide (27) to trifluoroacetylphosphine oxide (28), to give (29), although the authors do not rule out the possibility of direct formation of (26).25However, an independent study 27 of the oxidation of trifluoroacetylphosphine(30) shows how the 2: 1 adduct (29) is formed initially [by addition of (27)?], and how contact with glass causes rapid isomerization to (26). Once again, the reversible formation of (29) remains an unanswered aspect of the pathway to (26). 0 CF3C0,H + Ph,PCl
II
Ph,PCOCF,
A further illustration has appeared28of the reactivity of simple a-keto-alkyldiphenylphosphine oxides (31) towards addition reactions, as outlined in Scheme 5. In the same paper, alkylation of chloro(di-t-buty1)phosphine (32) by alkyl benzoates is described see Chapter 3 for details. A similar acylation reaction of tetramethyldiphosphine disulphide (33) has been described, although the acetylphosphine sulphide (34)was not 22
23 24 25 26 27
28 29
R. Luckenbach and M. Kern, Chem. Ber., 1975, 108, 3533. K. Goda, R. Okazaki, K. Akiba, and N. Inamoto, Tetrahedron Letters, 1976, 181. R. Okazaki, Y.Hirabayashi, K. Tamura, and N. Inamoto, J.C.S. Perkin I, 1976, 1034. P. Sartori and R. H. Hochleitner, Z. Naturforsch., 1976, 31b. 76. D. J. H. Smith and S. Trippett, J.C.S. Perkin I, 1975, 963. E. Lindner, H.-D. Ebert, and H. Lesiecki, Angew. Chern. Internat. Edn., 1976, 15, 41. N. J. De’ath, S.T. McNeilly, and J. A. Miller, J.C.S. Perkin I , 1976, 741. A. N. Pudovik, G. V. Romanov, A. A. Lapin, and E. 1. Gol’dfarb, J. Gen. Chem. (U.S.S.R.), 1975,45, 1857.
-
Phosphine Oxides and Sulphides Ph,POMe
+ RCOCl
0
77
+ MeCl
Ph,P(O)COR (31)
0
0
I1 II Ph,PC(R)OPPh,
ll
+
I XI
(Ph;P),C
R = AcorH
0
0
ll + RPBut2
S
1
+
R = Me or benzyl
I1 (Me,P),
R,PBwt R = benzyl S
S
f
MeCOC1
\
\OR
R = MeorPh, X = H R = Ph, X = COPh Scheme 5
Bu',PCk + PhC0,R
/Me
:ty*.*
II Me,PCOMe
(33)
II
+ Me,PCl
(34)
0
II Bu,PH
0
I/ + MeCCN
0 ._)
0
ll Ph,PH
II
Bu,POCH(Me)CN
78%
0
+ R'N=NC0,R2
ll
Ph,PNR'NHC0,R2
(36)
Addition reactions of secondary phosphine oxides to acetyl cyanide (35),30 and to azo-esters (36),81have been described. Complexes of dimethylphosphine sulphide (37) with manganese pentacarbonyl derivatives, in which the new ligand is bonded through sulphur, have been isomerized to complexes in which phosphorus is bonded to the 30
T. M. Sudakova, E. Kh. Ofitserova, and A. N. Pudovik, J. Gen. Chem. (U.S.S.R.),1975, 45. 25 12.
31 32
K.-H. Linke and W. Brand, Angew. Chem. Internat. Edn., 1975, 14, 643. E. Lindner and H. Dreher, Angew. Chem. Internat. Edn., 1975, 14,416.
78
Organophosphorus Chemistry
3 Reactions involving P-C Bond Cleavage The phosphine oxide (38) is known to undergo nucleophilic substitution reactions with cleavage of either a phosphorus-phenyl bond, or one of the heterocyclic 0 N - H H*
pJL-?
Ph
+PhH
phosphorus-rbon bonds.ss These processes have now been suggested to depend upon the apicophilicity of the incoming nucleophile (N), as shown for hydride and hydroxide nucleophiles.33 Primary amines react with benzylbis(a-hydroxybenzy1)phosphine oxide (39) to give a-aminoalkylphosphine oxides (40) and (41),34 and the reaction has been 0
It PhCH,P(CHOHPh),
0
II
PhCH,PCH(OH)Ph
bag*
H
I-
(39)
+ PhCHO bNH*
PhCH=NR
'II /
CH(0H)Ph
PhCH,P(CH(NHR) Ph), +repe'
--
PhCH,P
\
CH(Ph) NHR
(40) 88 84
I. Granoth, Y. Segall, and H. Leader, J.C.S. Chem. Comm., 1976, 74. A. B. Pepperman and T. H. Siddall, J. Org. Chem., 1975,40, 1373.
79
Phosphine Oxides and Sulphides
shown34,36to involve release of benzaldehyde from (39), and subsequent addition of the secondary phosphhe oxide to benzalimine. A similar reaction forms the basis of the explanation proposed for the production of (42) from (39).36 Details of various routes to allylphosphineoxides (43) have been reported, and the subsequent synthesis of lY3-dieneshas been illustrated by many examples.37Also described are stereochemical aspects of these diene syntheses and of subsequent Diels-Alder cycloaddition reaction^.^' High regioselectivity is observed in migrations of the diphenylphosphinoyl group from unsymmetrical sites, as in (44),in that both products have a double bond exocyclic to the cyclohexane ring.38 0
I/
Ph2P--c/
‘c=o \ +/
CE;CO,H
\R
P h P ally1
Wittig
dienes
0
I1
Ph,PCl + RMgX
*OH (44)
PPh,
II 0
PPh,
II
0
4 Reactions of X in the P=X Group Migration of sulphur from one phosphorus to another has been when the sulphide (45) is heated. The intermediates(46) and (47) have been detected. Debenzylation of the phosphine sulphide (48) has been shown to be accompanied by a desulphuration, which is believed to result from the interaction of (49) with alkaline DMS0.40 s6 36 87
s8 s8 40
A. B. Pepperman and T. H. Siddall, J. Org. Chem., 1975,40, 2053. A. B. Pepperman, G. J. Boudreaux, and T. H. Siddall, J. Org. Chem., 1975,40,2056. A. H. Davidson and S. Warren, J.C.S. Perkin I , 1976, 639. A. H. Davidson and S. Warren, J.C.S. Chem. Comm., 1976, 181. S. 0. Grim and J. D. Mitchell, J.C.S. Chem. Comm., 1975, 634. R. Luckenbach, Tetrahedron Letters, 1976, 2015.
Organophosphorus Chemistry
80 Ph2PCH,PMe, S
S
(46)
II Ph,FCH,PMe,
+ s
(45)
I1
Ph,PCH,PMe,
--+
s
II ll Ph,PCH,PMe,
Further examples of deoxygenation of epoxides by phosphine sulphides or selenides have appeared,4l as shown in Scheme 6 for simple epoxides (50). Incorporation of phosphorus into a five-membered ring appears to be responsible for the relatively rapid deoxygenations by the phosphole and A3-phospholen derivatives.4l
X = S orSe Reagents: i,
Melr-JMe /
PI1
;
X = Sor Se
(50)
.. Me[-=Me
11,
x/
\
Ph
Scheme 6
Several examples have been reported of rearrangements of arsine oxides (51) to esters, initiated by alkyl 43 Reactions of tertiary arsine oxides with thiols (52) cause de~xygenation.~~ 0
II Ph,AsR’
.O
+ R’X
--+
Ph,AsOR2 + R’X
II
R ~ A s+ R’SH
R2SSR2 + R:As
+
H,O
5 Reactions of the Side-chain Further bisalkynylphosphine oxide (53) cyclizations have been applied to heterocyclic synthesis.46The phosphine oxide (54) has been prepared as shown, and found to undergo Diels-Alder addition by an intramolecular pathway, to give (55).46 41
42 43 44
45
4G
F. Mathey and G . Muller, Compt. rend., 1975, 281, C, 881. Yu. F. Gatilov, B. E. Abalonin, and Z . M. Izmailova, J. Gen. Chern. (U.S.S.R.), 1975, 45, 42. Yu. F. Gatilov, B. E. Abalonin, and Z . M. Izmailova,J. Gen. Chem. (U.S.S.R.),1975,45,2145. N. A. Chadaeva, K. A. Mamakov, and T. V. Arsent’eva, Bull. Acad. Sci., U.S.S.R.,1975,1715. A. Naaktgeboren, J. Meijer, P. Vermeer, and L. Brandsma, REC.Trav. chim., 1975, 94, 92. 0. Schaffer and K. Dimroth, Angew. Chern. Znternat. Edn., 1975, 14, 112.
81
Phosphine Oxides and Sulphides
A0
(5 3)
R'
X = 0,S,or NEt Ph. ,H,CH=CD, 110°C
I
Ph
/ \OCDaCH=CHL
Me
/A \0
Me
p
31
D
CD
Me (55)
Ph
Me '0 (54)
Aromatic substituent effects due to phosphorus groups have been studied for a number of reactions.47Thus ester hydrolysis and fluoride-displacement rates, for (56) and (57) respectively, are enhanced by phosphorus substituents (X = 0 or :), while the rate of hydrolysis of the halide (58) is enhanced for X = :, but slowed for X = 0.47 A perturbation M.O. analysis of these observations has been p r e ~ e n t e d . ~ ~
(56) R = C0,Me (57) R = F
(59) n = 0 or n = 1
(58) R = CHClMe
(60)
Nitration of various p h e n ~ l - *and ~ benzyl-phosphineS0 oxides (59) has been described, and the P=O group found to be meta-dire~ting~~ in the former case. Pyrolysis of the acyl azide (60)61takes the course shown.
50
B. Klabuhn, H. Goetz, P. Steirl, and D. Alscher, Tetrahedron, 1976, 32, 603. B. Klabuhn, Tetrahedron, 1976,32, 609. E. Malinski, A. Piekos, and T. A. Modro, Canad. J. Chem., 1975,53, 1468. V. V. Kormachev, T. V. Vasil'eva, B. 1. Ionin, and V. A. Kukhtin, J. Gen. Chem. (U.S.S.R.),
51
V. A. Shokol, V. V. Doroshenko, and G . I. Derkach, J. Gen. Chem. (U.S.S.R.), 1975,45, 1680.
47 48 49
1975, 45, 293.
82
Organophosphorus Chemistry
6 Miscellaneous Physical and Structural Aspects Extensive 13Cand slP n.m.r. studies have been reported for phosphine oxides and selenides, and the inversion-recovery technique has been used to establish 2J and *J values for 1sG31Pcoupling.62Shift reagents have been used to establish alkene geometry in the oxides (61).53Coupling and shift data have been published for the arylphosphine derivatives (62).64 0
X
ll
Ar,P
(62) Ar = 4-chlorophenyl or 3-chlor ophen yl x = - , 0, S, or Se
X
X
II Me,P
II
Ar,P
(63) a; X = 0 b; X =
-+, S,
or Se
(64) a; X = S or Se b ; X = 0,
Torsional barriers for trimethylphosphine derivatives (63) have been obtained from Raman spectra.66Vibrational spectra for the uranyl nitrate complex of (63a) have been published.66Complexes of triarylphosphine derivatives (64) with iodine,67 and of (64b) with metal halidesYs8 have been the subject of therrnodynami~~~ and spectroscopicti 7, 68 study. X-Ray data have been published for Ah"-phospholenl-oxide (65),60tri-o-tolylphosphine derivatives (66),*O and various halogeno-alkylphosphine oxides.61
(66).X= 0, S, or Se (65)
Further study has been made of the ionization of the phosphinoyl-substituted acids (67), and the substituent at phosphorus has been found to be important in influencing acidity.62Evidence for cyclic solvates was found for (67;n = 1).62 The T. A. Albright, W. J. Freeman, and E. E. Schweizer, J. Org. Chem., 1975,40,3437. H.Koeppel, U. Lachmann, and K. D. Schleinitz, J. prakt. Chem., 1975,317,425. 54 R. F. De Ketelaere and G. P. van der Kelen, J. Mol. Structure, 1975,27, 25. 55 H.Rojhantalab, J. W. Nibler, and C. J. Wilkins, Spectrochim. Acta, 1976,32A,519. 56 Y. B. Kirillov, E. P. Buchikhin, K. I. Petrov, and T. V. Zagorskaya, Zhur. priklad. Spectroskopii, 1975,23,514. 57 F. Lux, R. Paetzold, J. Danel, and L. Sobczyk, J.C.S. Faraday 1 1, 1975,71, 1610. 5 8 E. G.Amarskii, A. A. Shvets, and 0. A. Osipov, J. Gen. Chem. (U.S.S.R.), 1975,45, 881. 59 D. van der Helm, D. M. Washecheck, J. E. Burks, and S . E. Ealick, Acta Cryst., 1976,B32,659. 60 T. S. Cameron and B. Dahlen, J.C.S. Perkin 11, 1975, 1737. 61 V. V. Saatsasov, T. L. Khotsyanova, and S. I. Kuznetsov, Bull. Acad. Sci., U.S.S.R.,1975,839. 62 E. N.Tsvetkov, R. A. Malevannaya, and M. I. Kabachnik, J. Gen. Chem. (U.S.S.R.), 1975,45, 706.
S2
53
83
Pliosphine Oxides and Sulphides
(67)
(68)
(69)
carbon acidity in diglyme or DMSO of phosphine oxides with general formula (68) has been evaluated by a transmetallation method.64A change of about eight pKa units results from introduction of the phosphinoyl group onto a hydrocarbon site.63 Substituent effects in the benzyl ring of (69) have been observed to influence acidity in the oxides (69),and a good correlation with 0- has been ~ b t a i n e d . ~ ~ The ability of phosphine oxides to enter into intermolecular hydrogen bonding has Since the dipole values of simple oxides been measured by i.r. and dipole (70a), (70b) fit a vector-addition model, the authors suggest that H-bonding is controlled by electrostatic interaction (and not by chargetransfer effects).66 On a related theme, the extracting powers of the oxide (70b) towards thiocyanic acids6 and of the oxide (70a) towards cationss7p68have been measured. The oxides (71) form cyclic complexes with titanium tetrahalides.6B 0 R,P=O (70) a; R = Me b; R = Bun c; R = n-octyl
0
II
(n-alkyl) PMe,
n-Alkyl(dimethy1)phosphine oxides (72) form micelles readily, and a study of the (unexpected) increase in entropy associated with micellization has been made.7b Acetoxymethylphosphine oxides have been investigated as starters in the synthesis of phosphorus-containing polyesters.71 The synthesis of azo dyestuffs containing phosphine oxide groups, as in (73), has been 63 64
s5 86
s7 68
70
72
S. P. Mesyats, E. N. Tsvetkov, E. S. Petrov, M. I. Terekhova, A. I. Shatenshtein, and M. I. Kabachnik, Bull. Acad. Sci., U.S.S.R., 1974,2399. S . P. Mesyats, E. N. Tsvetkov, E. S. Petrov, N. N. Shelganova, T. M. Shcherbina, A. I. Shatenshtein, and M. I. Kabachnik, Bull. Acad. Sci., U.S.S.R., 1974, 2406. Yu. Ya. Borovikov, Yu. P. Egorov, and A. A. Matei, J. Gen. Chem. (U.S.S.R.), 1975,45,2563. M. Zakharieva, Khim. i Znd., 1975,47, 66. J. W. Mitchell and J. E. Riley, Radiochem. Radioanalyt. Letters, 1975, 21, 41. M. Mojski and C. Poitrenaud, J. Radioanalyt. Chem., 1976, 29, 89. A. A. Shvets, 0. A. Osipov, 0. A. Moiseeva, and E. L. Korol, J. Gen. Chem. (U.S.S.R.), 1975 45, 1251. J. H. Clint and T. Walker, J.C.S. Faraday I, 1975, 71, 946. G. Borisov, S. G. Verbanov, E. N. Tsvetkov, and M. I. Kabachnik, Vysokomol. Soedineniya, Ser. A, 1975, 17, 1065. V. V. Kormachev, S. N. Chalykh, E. A. Chalykh, A. A. Sazanova, and V. A. Kukhtin, J. Gen. Chem. (U.S.S.R.), 1975,44,2575.
5 Tervalent Phosphorus Acids BY 8.J. WALKER
1 Introduction Although this chapter is somewhat shorter than last year's, it is encouraging to note that several papers have appeared which deal with the synthesis and chemistry of p,-bonded phosphorus compounds. 2 Phosphorous Acid and its Derivatives Nucleophilic Reactions.-At tack on Saturated Carbon. Selected examples of the Arbusov reaction include phosphorylation of the chloroacetophenones (1) to give phosphonates, which cyclized to (2) in the presence of acid chlorides,l formation of the azodiphosphonate (3) from 2,2'-dichloro-2,2'-azopropane,2and the reaction of 2-chloro-3,4-dihydro-3-oxo-2H1,4-benzothiazine (4) with triethyl phosphite to give the 2-phosphonate (9, which is used as an o l e h synthon? Bis(trimethylsily1) trimethylsiloxymethylphosphonite(6) has been synthesized by silylation of hydroxymethylphosphonous acid, and, as expected, undergoes a normal Arbusov reaction with alkyl halides to give the phosphonates (7).4 This series of reactions, followed by 0
I1
PhCOCHClNHCOR'
II
EtOPR:
ph
I
(1 1
- PRi
n
PhCWHNHCOR'
0\2
K'
0
0
ll ll (E t O),PCMe,N=NCMe,P( OEt), (4)
(3)
x
= c1
0
/I
( 5 ) X = P(OEt),
2
B. S. Drach, I. Yu.Dolgushina, and A. D. Sinitsa, Zhur. obshchei Khim., 1975,45,1251 (Chem. Abs., 1975, 83, 131 688). E.g. Ya. A. Levin, I. P. Gosman, A. G. Abul'kanov, and B. E. Ivanov, Izoest. Akad. Narrk S.S.S.R.,Ser. khim., 1975, 983 (Chem. Abs., 1975, 83, 97469). J. W. Worley, K. W. Ratts, and K. L. Commack, J. Org. Chem., 1975, 40, 1731. A. F. Rosenthal, A. Gringauz, and L. A. Vargas, J.C.S. Chem. Comm., 1976, 384.
84
Tervalent Phosphorus Acids 0
(Me,SiO),PCH,OSiMe,
RCW'
t
ll RCH,PCH,OSiMe,
---
85
0
HO
II
RCH,PCH,OH
I
I
OSiMe,
OH
(7)
hydrolysis, provides a method for introducing the hydroxymethylphosphinate group. The Michaelis-Arbusov alkoxyphosphonium salt intermediate (8) has been isolated from a low-temperaturereaction of 2-chlorotetrahydropyran with trimethyl phosphite and antimony pentachloride.s The corresponding trifluoromethyl sulphonate (9) can be prepared independently by trapping the oxocarbenium ion (10) with trimethyl phosphite (Scheme 1). Mild dealkylation of (8) or (9) with hydroxide
+ (10)
1
y
(11)
+oi.CoMe), CF,S03(9 1
Reagents: i, (Me0)3P-SbC15, -78 "C; ii, OH-; iii, Me30+ SbCL-; iv, CFsS03H; v, (MeO)aP, -78 "C.
Scheme 1
ion provides the phosphonate (1 l), which can be re-converted into (8) by alkylation with trimethyloxonium hexachloroantimonate. A kinetic study of the Arbusov contribution in the reactions of triethyl phosphite and aryl-substituted a-bromoacetophenones gives a Hammett p value of -0.22.6 This suggests that the ketophosphonate product is formed via substitution at carbon and that attack on bromine is unlikely. The reaction of phosphites with trialkyloxonium salts in acetonitrile generally gives the corresponding alkyltrialkoxyphosphonium salt (12). However, under the same conditions, the bicyclic phosphite (13) accepts a proton, rather than an alkyl group, to give (14).' Surprisingly, X-ray diffraction shows (14) to possess a trigonalbipyramidal tricyclic structure with phosphorus co-ordinated to nitrogen. N-
ti
7
J. Thiem, M. Gunther, and H. Paulsen, Chem. Ber., 1975, 108, 2279. E. M. Gaydou and J.-P. Bianchini, J.C.S. Cliem. Comm., 1975, 541. J. C. Clardy, D. S. Milbrath, J. P. Springer, and J. G. Verkade, J. Amer. Chem. SOC.,1976, 98, 624.
4
86
Organoyhosphori~sChemistry
Silylated iminophosphines (15) react with alkyl halides to give the iminophosphoranes (16).8 Similar reactions with Main-group IV and VII halides give the heterocycles (17) via the intermediate 1,2-addition products (1 S), which can be isolated in the case of germanium. Attack on Unsaturated Carbon. The annual addition of phosphites to every variety of activated double bond continues. These include nitro-alkenes, ab-unsaturated The carboxylic acid derivatives,lO maleimides,ll fulvenes,12and pyridinium ~a1ts.l~ reaction of diethyl phosphite with keten 0 , N - ,S,N-, and N,N-acetals has been used to prepare the enamine phosphonates (19).14 The ag-unsaturated thioketone (20) undergoes Michael addition of trimethyl phosphite to give (21), which cyclizes to (22).15A similar addition of benzylalkyl (or
*
E. Niecke and W. Bitter, Chem. Ber., 1976, 109, 415. R. D. Gareev, E. E. Borisova, and I. M. Shermergorn, Zhur. obshchei Khirn., 1975, 45, 944 (Chem. Abs., 1975,83,28 337); E. E. Borisova, R. D. Gareev, T. A. Guseva, and I. M. Shermergorn, ibid., p. 943 (Chem. Abs., 1975,83, 43451). lo A. N. Pudovik, E. S. Batyeva, A. S. Selivanova, V. D. Nesterenko, and V. P. Finnik, Zhur. obshchei Khim., 1975, 45, 1692 (Chem. Abs., 1976, 84, 5064); C.-G. Shin, Y. Yonezawa, Y. Sekine, and J. Yoshimura, Bull. Chem. SOC.Japan, 1975,48, 1321. l1 A. N. Pudovik, E. S. Batyeva, and G. U. Zamaletdinova, Zhur. obshchei Khim., 1975, 45, 940 (Chem. Abs., 1975, 83, 43450); A. N. Pudovik, E. S. Batyeva, Yu. N. Girfanova, and V. Z. Kondranina, Zhur. obshchei Khim., 1975, 45, 2618 (Chem. Abs., 1976, 84, 105689). l2 N. R. Vladimirskaya, V. I. Koshutin, and V. A. Smirnov, Izvest. Sev.-Kavk. Nauchn. Tsentra Vyssh. Shk., Ser. Estestv. h'auk, 1975, 3, 24 (Chem. Abs., 1976, 84, 17505). l3 D. A. Predvoditelev, T. G. Chukbar, and E. E. Nifant'ev, Khim. geterotsikl. Soedinenii, 1975, 377 (Chem. Abs., 1975, 83,43447). l4 M. Fukuda, K. Kan, Y. Okamoto, and H. Sakurai, Bull. Chem. SOC.Japan, 1975, 48, 2103. l5 B. A. Arbusov, N. A. Polezhaeva, and V. V. Smirnov, Izvest. Akad. Nauk S.S.S.R., Ser. ktiim., 1975, 688 (Chem. Abs., 1975, 83,43446).
Tervalent Phosphorlrs Acids 0
R'CH=CR2NMe,
I1 + (EtO),PH
R2 = OMe, SEt, or NMe,
-
0
ll
(El-R'CH=C(NMe,)P(OEt), (19)
S
II MeC--C=CHMe I CO,E t
87
Me
+ (MeO),P
--+
0
II
hkS-- C=CCI-IMeP(OMe), CO,E t
aryl) phosphinites to ag-unsaturated ketones has been used to prepare A2-phospholen 1-oxides (23),le The reaction of 2-phenyl-l,3,2-dioxaphospholan with acrylic acid and acrylamide provides the first synthesis of cyclic acyloxy-(24) and amido-(25) phosphoranes.l7 + CH,=CHCOXH
Ph()
4
P 3
0 (24) X = 0 (25) X = NH
(28) R = Me l7
R. Bodalski, K . M. Pietrusiewics, and J. Koszuk, Tetrahedron, 1975, 31, 1907. T. Saegusa, S. Kobayashi, and Y. Kimura, J.C.S. Chem. Comm., 1976, 443.
Organophosphorus Chemistry
88 Ph p h b O Ph
+
R,P
I
R,P=-C--C=C=O
I
Ph (29)
Further studies of the reactions of secondary and tertiary phosphites with cyclopentadienones have included the keto-cyclone (26), which gives the phosphonates (27) and (28), respectively.18 Ketenphosphoranes (29) have been prepared by the reaction of diphenylcyclopropenone with a variety of tervalent phosphorus compound~.~~ Recently reported additions of dibutyl phosphinite2O and tetra-alkoxydiphosphines21to alkenes are probably of free-radical nature, although the reactions only take place with alkenes possessing electron-withdrawing groups. The usual flood of reports concerning the addition of phosphites to imines has appeared. These include the reaction of hypophosphites to give cc-aminoalkylphosphinic acid salts possessing antibacterial activity22and the synthesis of A4-1,4,2A5-oxazaphospholines(30) from phosphites and carbo~amides.~~ The addition of
Ph (31)
dimethyl phosphite to the Schiff base (31) involves attack on nitrogen rather than carbon, presumably because of the aromatic nature of (32).24 Similar additions to 18
l9 2o
21 22 23
24
A. V. Fuzhenkova, A. P. Zinkovskii, and Yu. I. Khramtsov, Zhur. obshchei Khim., 1976, 46, 285 (Chem. Abs., 1976, 84, 164944). A. Hamada and T. Takizawa, Chem. and Phnrm. Bull. (Japan), 1975, 23, 2933. K. Issleib, W. Kitzrow, and I. F. Lutzenko, Phosphorus, 1975, 5, 281. I. F. Lutsenko, M. V. Proskurnina, and A. L. Chekhun, Zhur. obshchci Khim., 1976, 46, 568 (Chem. Abs., 1976, 84, 180349). V. I. Yudelevich, L. B. Sokolov, B. I. Ionin, and L. G . Myasnikova, Zlzur. obshchei Khim.,1975, 45, 1554 (Chem. Abs., 1976, 84, 44278). J. Albanbauer, K. Burger, E. Burgis, D . Marquarding, L. Schabl, and I. Ugi, Annalen, 1976,36. B. A. Arbusov, E. N. Dianova, A. V. Fuzhenkova, and A. F. Lisin, Izoest. Akad. Nauk S.S.S.R., Ser. khim., 1975, 1825 (Chem. Abs., 1975, 83, 206385).
89
Tervalent Phosphorus Acids
azines give the expected product through attack on carbon,26and this reaction, followed by hydrolysis, has been used to prepare or-aminophosphinic acids.26 Diethyl dl-1-aminobenzylphosphonatehas been prepared by a Mannich reaction of diethyl phosphite, benzaldehyde, and ammonia, resolved as its D-mandelate salt, and hydrolysed to give ( )-1-aminobenzylphosphonic acid.27While the tetraethyldiamide (33) reacts with benzaldehyde to give the expected phosphonic diamide (34), the corresponding tetramethyl-diamide reacts, with migration of the dimethylamino-group, to give (35).2*
+
0
(33) 0
(34)
II
A/OH (Me,N),PH + PhCHO --+ Me,NP, CHPhNMe, (35)
cis-a/?-Dimethoxycarbonylstilbeneoxides have been prepared by the reaction of hexamethylphosphorous triamide with aryl glyo~ylates.~@ Electronic and steric effects should favour the formation of the trans-l,4,2-dioxaphospholan(36), and a concerted (allowed) retrograde ,2s + ,48 cycloaddition of (36) followed by conrotatory cyclization of (37) would give the cis-stilbene. The reactions of phosphites and phosphines with the ketone (38) and thioketone (39) are complex, and tetrathiafulvalenes (a), betaines (41), and phosphonates may be formed, depending on the condition^.^ *
I C0,Me
(36) Ar
Me0,C
C0,Me
CO,Me (37)
27
E. E. Nifant’ev, N. V. Zyk, and M. P. Koroteev, Zhiir. obshchei Khim., 1975, 45, 1455 (Chem. Abs., 1975, 83, 179218). J. Rachon and C. Wasielewski, Roczniki Chem., 1975,49, 397 (Chem. Abs., 1975, 83, 10294); E. E. Nifant’ev, N. V. Zyk, M. P. Koroteev, and V. N. Abramov, Zhur. obshchei Khim., 1975, 45, 2162 (Chem. A h . , 1976, 84, 59657). M. K. Rho and Y . J. Kim, Taehan Hwahak Hoechi, 1975, 19, 434 (Chem. Abs., 1976, 84,
28
E. E. Nifant’ev and I. V. Shilov, Zhur. obshchei Khim., 1975, 45, 1264 (Chem. Abs., 1975, 83,
29
147 546). G. W. Griffin, D. M. Gibson, and K. Ishikawa, J.C.S. Chem. Comm., 1975, 595. M. G. Miles, J . S. Wager, J. D. Wilson, and A. R. Siedle, J. Org. Chem., 1975, 40,2577.
25 26
150 703).
3O
90
Organophosphorus Chemistry
(44) R1 = OAlkyl (45) R’ = Alkyl
The isochromanylphosphonate(42) has been prepared by the reaction of triethyl phosphite with 2-(2’-bromoethyl)ben~aldehyde.~~ A related reaction is the one-step synthesis of phosphomycin derivatives from the base-catalysedreaction of secondary phosphites with or-halogenoketonesreported by Haake.32N.m.r. evidence was obtained for a phosphonate halohydrin intermediate (43).by-Epoxyalkyl-phosphonates (44)and -phosphines (45) have also been prepared from epibrorn~hydrin~~ and from ap-epoxy-ketone~.~~ Several unexceptional examples of the Perkow reaction have been reported, including the reaction of trimethylsilyl dimethyl phosphite with diethyl trichloroacetylphosphonate to give (46)35 and of triethyl phosphite with the halogenomethyl heterocyclic ketones (47) to give mixtures of enol- and ketophosph~nates.~~ Insecticidal enol-phosphonates (48) have been prepared from aryl 31 32 33 34
35 36
€1. Gross and I. Keitel, Tetrahedron Letters, 1976, 915. B. Springs and P. Haake, J. Org. Chem., 1976, 41, 1165. A. P. Rakov, E. A. Kosterin, and G. F. Andreev, Zhur. obshchei Khim., 1975,45, 1760 (Chem. Ahs., 1975, 83, 206381). A. N. Pudovik, M. G. Zimin, and A. A. Sobanov, Zhrir. obshchei Khim., 1975,4§, 1232 (Chern. Abs., 1975, 83, 131 686). I. V. Konovalova, L. A. Burnaeva, and A. N. Pudovik, Zlirw. obshchei Khim., 1975, 45, 2567 (Chem. Abs., 1976, 84,44258). A. Arcoria, S. Fisichella, E. Maccarone, and G. Scarlata, J. Heterocyclic Chem., 1975, 17, 215.
Tervalerit Phosphorits Acids
91 0
0 It
Me,SiOP(OEt), + CI,CCOP(OEt)2
--+-
0
It I/ (EtO)?POC----I”(OEt)2 II CCI, (46)
halogenoalkyl ketones, and the effect of the reaction conditions on their stereochemistry has been thoroughly in~estigated.~’ Surprisingly, the Perkow reaction of chloroacetyl chloride proceeds normally to give the enol-phosphonate (49) as the major product,5*although on the basis of the accepted mechanism for the Perkow reaction, other products should be preferred. The reactions of dimethyl phenylphosphonite with acid chlorides, cc-halogenoketones, and N-(bromomethy1)phthalimide have been used to prepare acyl phosphinates, P-keto-alkylphosphinates, and phthalimidomethylphosphinates as intermediates in the synthesis of a-diazophosphinic a-Amino-phosphonateshave also been prepared by the addition of secondary phosphites to nitriles40 and to i~ocyanides.~~ Attack on Nitrogen. A variety of cyclic derivatives of phosphorous acid have been converted into spirophosphoranes (51), using diethyl azodicarboxylate as the condensing probably by initial addition to nitrogen to give (50). Several 37 38 38 40
*l 42
R. Malinowski and M. Mikelajczyk, Pr. Inst. Przem. Org., 1974, 6, 95 (Clzcm. Abs., 1976, 84, 164 949). 0. E. Nasakin, V. V. Kormachev, and V. A. Kukhtin, Zhur. obshchei Khim., 1975, 45, 2374 (Chem. Abs., 1976, 84, 59668). U. Felcht and M. Regitz, Chem. Ber., 1975, 108, 2040. V. V. Orlovskii and B. A. Vovski, Zhur. obshchei Khim., 1976, 46, 297 (Chem. Abs., 1976, 84, 164 946). A. N. Pudovik, V. I. Nikitina, M. G. Zimin, and N. L. Vostretsova, Zliur. obshckei Khim.,1975, 45, 1450 (Chem. Abs., 1975, 84, 179217). S. A. Bone and S. Trippett, J.C.S. Perkin I , 1976, 156.
92
Organophosphorus Chentistry
Me,SiOP(OMe),
f
PhN,
--+
(MeO),&--N=N-NPh
I
OSiMe,
0
0
II
It (MeO),P-N=N-NI1Ph
,SiMe,
(Me0)2P-N=N--N
( 5 3)
P' h (5 2)
reports have appeared on the reaction of phosphites with azides to give the corresponding phosphite imine~,"~ while the addition of dimethyl trimethylsilyl phosphite to phenyl azide gave (52), which on hydrolysis gave the stable phosphonate (53).44 Attack on Oxygen. Nitrones have been deoxygenated to the parent imine with trimethyl phosphite under vigorous conditions.46Virtually quantitative yields of the enol-phosphates (54) and (55) were obtained from the reaction of tris(trimethylsily1) phosphite with or-diketones and p-benzoq~inone.~~ 0
II
,/P(OSiMe.J,
'
0
II
Me,SiOCR=CROP (OSilfeJ, (54)
*x-
:1
(Me,SiO),P O-+ OSiMe,
(5 5 ) 43 44 45
46
E.g. D. E. Arrington, J.C.S. Dalton, 1975, 1221. R. D. Gareev, Zhur. obshchei Khim., 1975, 45, 2557 (Chem. Abs., 1976, 84, 44257). B. A. Arbusov, E. N. Dianova, V. S. Vinogradova, and A. F. Lisin, Izuest. Akad. Nauk S.S.S.R., Ser. khini., 1975, 695 (Chem. Abs., 1975, 83, 28335).
T. Hata, M. Sekine, and N. Ishikawa, Chern. Letters, 1975, 645.
93
Tervalent Phosphorus Acids
Attack on Halogen. Predictably, the 3-bromo-3-cyano-imides (56) and (57) form quasiphosphoniumsalts (58) with aryl phosphites, phosphonites, and ph~sphinites.~' In the case of (56) these salts cyclize to the oxazaphosphorane (59), which is in equilibrium with the iminophosphorane (a), depending on the phosphorus ester used.
(56) n = 1 (57) n = 2
Br
0 Me
Me
In a continuation of his phosphine-carbon tetrachloride reactions, Appel has reported a convenient synthesis of alkyl phosphinates from chlorophosphines, alcohols, carbon tetrachloride, and base.48The reaction presumably takes place via the alkoxyphosphonium salt (61) and an Arbusov reaction. The reaction of nucleophiles with monoalkoxyphosphonium salts (62), obtained from the reaction of glycols with tris(dimethy1amino)phosphine-carbon tetrachloride, provides a highyield route to monofunctionalized alcohols.49The tris(dimethy1amino)phosphinecarbon tetrachloride reagent converts vicinal diols into trans-epoxides or spirophosphoranes, depending on the diol sub~tituents.~ O The proposed mechanism is shown in Scheme 2, and the relative rates of rotation and y-elimination in the intermediate (63) control the products formed. Secondary phosphites react in a similar way with carbon tetrachloride, and further reaction with trimethyl sulphoxonium ylide gives a high yield of the phosphonylsulphoxonium ylide (64).5l 47
48 49
50
51
M. F. Pommeret-Chasle, A. Foucaud, M. Leduc, and M. Hassairi, Tetrahedron, 1975,31,2775. R. Appel and U. Warning, Chem. Ber., 1976, 109, 805. R. Boigegrain, B. Castro, and C. Selve, Tetrahedron Letters, 1975, 2529. R. Boigegrain and B. Castro, Tetrahedron Letters, 1975, 3459; R. Boigegrain and B. Castro, Tetrahedron, 1976,37, 1283; R. Boigegrain, B. Castro, and B. Gross, Tetrahedron Letters, 1975, 3947. V. P. Lysenko, I. E. Boldesskul, Y. G. Cololobov, and R. A. Loktionova, Zhur. org. Khim., 1975,11, 2440 (Chern. A h . , 1976,84,44283).
94
0rganophosphorus Chemistry
Reagents : i, (Me2N)$CI; ii, Cch-; iii, HO(CH&OH.
Scheme 2 0
II (E t O),PH
0
C(1,
0
II II -+ (EtO),PCH=SMe,
II II
(64)
M e,S =CH,
c1 ClPWMe,),
(651
ArCH Oif
Bt,,,
: ArCII,OP(NMe,),
PhCCI,
*
I
ArCH,O~(NMe,), PhCCI,
(66)
A r C E C P h +-
JArCH,CCl$h
B
+ (Me,N),PCII
A new synthesis of diarylacetylenes in moderate yield has been r e p ~ r t e d The .~~ reaction of a benzyl alcohol with the phosphorochloridite (65) gives the phosphorodiamidite (66), which reacts with benzotrichloride to give a 1,1 -dichlorodibenzyI. Finally, dehydrohalogenation gives an arylphenylacetylene. The phosphoruselimination step probably involves an Arbusov-type reaction, and this suggestion is supported by kinetic data. 31P N.m.r. spectroscopy of the Arbusov reaction of halogens or benzenesulphonyl chloride with cyclic phosphites is said to provide the first direct evidence for a five-co-ordinated intermediate in the reaction.53 52
53
J. H. Hargis and W. D. Alley, J.C.S. Chem. Conzm., 1975, 612. A. Skowroska, J. Mikolajczak, and J. Michalski, J.C.S. Chem. Comm., 1975, 791,
TerualentPhosphorus Acids
95
Electrophilic Reactions.-A high-yield conversion of optically active alcohols into the corresponding halides, using a modified phosphorus trichloride reaction, has been The crucial conditions appear to be a low-temperature (-25 "C)initial reaction, followed by prolonged stirring at 4 "C to allow complete cleavage of the intermediate phosphite esters before distillation. Oxetans undergo ring-opening with
R2 = CHJHMe, CHMeCHMe, or CN,CH,CH, (RO),PCl
Me,SiN
f
--+ (Ro),P-Np~
. b N
(69)
the phosphorous acid bromides (67) to give (68), which isomerize to cyclic phosphonates on heating.55 Phosphorous acid chlorides have been used to prepare phosphorous diester triazolides (69), which are excellent condensing agents for peptide synthesis.5 A number of inorganic ring systems containing phosphorus have been synthesized by the reaction of chlorophosphines with silylated amines. These include disilaphospha(m)diazacyclopentanes (70),5 adamantane analogues (71), and four-, six-, and eight-membered rings containing silicon, nitrogen, and p h o s p h o r u ~A . ~variety ~ of new bicyclic hydrazinebis(phosp1iines)(72) has been prepared by the reaction of 3,6-dichloro-l,2,4,5-tetramethylperhydro-l,2,4,5-tetra-aza-3,6-diphosphorine with Me,Si-%Me,
\
. / RN,
,NR
P Me
Me (71)
(70)
Me Me ,N-N CIP Me Me
N-N Me Me (72) X = RN-NR,RN,O,orS
54
55
57
58
R. 0. Hutchins, D. Masilamani, and C. A. Maryanoff, J. Org. Chem., 1976, 41, 1071. B. A. Arbusov, L. Z. Nikonova, 0. N. Nuretdinova, and N. P. Anoshina, Izoest. Akad. Nacrk S.S.S.R., Ser. khim., 1975, 473 (Chem. Abs., 1975, 83, 10288). H. R. Kricheldorf, M. Fehrle, and J. Kaschig, Angew. Chem. Znternat. E d ? . , 1976, 15, 305. U. Wannagat and H. Autzen, 2.anorg. Chem., 1976, 420, 132; ibid., p. 139. U. Wannagat and H. Autzen, Z . anorg. Chem., 1976,420, 119.
96 Li
I
Me2NNSiMe, + (73)
Me,%,
,N---PC1,
-
Organophosphorus Chemistry
Me,N-N-P
I SiMe,
"NCMe,
(74)
Li I
hydrazines and disila~ines.~~ One of several reports of multiply bonded tervalent phosphorus concerns the first synthesis of a phosphatetrazene (74) by the reaction of the lithiated hydrazine (73) with NN-(t-butyltrimethylsilyl)aminodichlorophosphine.60Attempts to prepare the isomer (75) by an analogous method gave only the dimer, presumably due to the lack of the steric effects present in (74). The formation of phosphanylium salts (77) in the reaction of phosphorus trichloride with methylhydrazones, presumably uia the intermediate chlorophosphine (76), may be assisted by aromatic stabilization of the product.g1
J
L (76)
Orthophosphoric and benzylphosphonic acids have been selectively alkylated with triethyl phosphite in a new synthesis of mono-, di-, and triethyl phosphates and of mono- and di-methyl phosphonates.62 N-Methylol carboxamides and sulphonamides react with trialkyl phosphites to give the phosphonate derivatives (78) and (80), respecti~ely.~~ However, the mechanism appears to be quite different in each case; while the carboamides react by a transesterification-rearrangement pathway, the sulphonamides undergo elimination-addition via the imine (79). 59 60
61 62
63
H. Noth and R. Ullmann, Chem. Ber., 1976,109, 1942. 0. J. Scherer and W. Glaebel, Angew. Chem. Znternat. Edn., 1975, 14, 629. J. Luber and A. Schmidpeter, Angew. Chem. Znternat. Edn., 1976, 15, 1 1 1 . A. Markowska, J. Olejnik, and J. Michalski, Chem. Ber., 1975, 108, 2589. D. J. Scharf, J. Org. Chem., 1976, 41, 28.
Tervalent Phosphorirs Acids R'CONHCH,OH 4-
(R20),P
-
97 0
R'CONHCH,OP(ORz), + W'OH
--+
II
R'CONHCH,P(ORZ), (7 8)
R'SO,NHCH,OH
__f
+ R'OH
[R'SO,N=-CH,1 (79)
0
p ) , P
I/
R'SO,NHCH, P(OR2),
t
R'SO,NCH,~(ORz),
(80)
The phosphoranes (81),64 (82),65 and (83),6a each containing a hydrogen ligand, have been prepared by the now standard procedure from amino-phosphines and amino-alcohols.A similar reaction of the amino-alcohol (84) gave oxazaphospholidine derivatives (85).s7 R R'P(NR:), + (HOCHK3CH,)2NH
3 H y \R' f
y
+
uNHz (81)
PhP(NMe,), +
MeCN
OH
H
€1
(82)
-
ArNHCH,CH,OH + PhPX, x = NMe, or c1 (84)
php, (85)
Rearrangements.-Vinyl phosphites (86) undergo catalysed thermal rearrangement to the corresponding phosphonites (87).68 64 65
67 68
D. Houalla, T. Mouheich, M. Sanchez, and R. Wolf, Phosphorus, 1975, 5, 229. C. Malavaud and J. Barrans, Tetrahedron Letters, 1975, 3077. S. A. Terent'eva, M.A. Pudovik, A. N. Pudovik, and Kh. E. Kharlampidi, Zhur. obshchei Khim., 1975, 45, 2559 (Chem. Abs., 1976, 84, 59673). T. T. Dustmukhamedov, M. M. Yusupov, N. K. Rozhkova, and S. R. Tulyaganov, Zhur. obshchei Khim., 1976, 46, 300 (Chem. Abs., 1976, 84, 164947). 2. S. Novikova, S. N. Zdorova, S. Ya. Skorobogatova, and I. F. Lutsenko, Zhur. obshchei Khirn., 1975, 45, 2384 (Chem. Abs., 1976, 84, 74361).
0rganophosp horirs Chemisfry
98
Cyclic Esters of Phosphorous Acid.-A large number of 2-substituted-4-methyl-1,3,2dioxaphospholans (88) have been prepared and their stereochemistry and conformations investigated by lH and 31Pr ~ . m . r .Unlike ~~ the corresponding 1,3dioxans, the trans-isomer (88a) is favoured in all cases, and each isomer is best described in terms of two rapidly equilibrating half-chair conformers with the 4-alkyl group pseudo-axial or pseudo-equatorial. H
Hudson and Verkade have offered an explanation for the conformational preference of phosphorus substituents in both dioxaphosphorinans (89) and their oxides (90).'O In the case of (89) the interactions involved are oxygen-phosphorus lone-pair repulsion, oxygen lone-pair repulsion of electrons in the P-X bond, and a hyperconjugative attraction involving the antibonding orbital of the P-X bond. In some cases, interactions with lone pairs of electrons on the phosphorus substituent also contribute. The variable conformational preference of amino-groups in 1,3,2dioxaphosphorins has been investigated by Stec and his co-workers. While tb~tylarnino-~l and anilino-groups72 are largely axial at equilibrium, the dimethyl-
C1
PhNH 10
90
a
I
Ph NH
(92) O9
7* 7l 72
W. G . Bentrude and H. W. Tan, J. Amer. Cheni. SOC., 1976, 98, 1850. R. F. Hudson and J. G . Verkade, Tetrahedron Letters, 1975, 3231. T. J. Bartczak, A. Christensen, R. Kinas, and W. J. Stec, Tetrahedron Letters, 1975, 3243. W. J. Stec and A. Okruszek, J.C.S. Perkin I , 1975, 1828.
TerunEent Phosphorus Acids
99
I
c1 amino-group72 prefers the equatorial orientation. The results are attributed to varying steric effects. The stereochemistry of (91), prepared from 2-chloro-4-methyl1,3,2-dioxaphosphorin(92), was determined by stereospecific oxidation to the correA similar reaction sponding 2-oxides, the stereochemistry of which is with t-butylamine gave a mixture (26:74 by 31P and 13C n.m.r.) of cis- and trans-2-t-butylamino-4-methyl-1,3,2-dioxaphosphorin (93) which did not change on distillation. Treatment of this mixture with selenium gave the corresponding cis- and trans-selenides (30 :70 by n.m.r.).?l The stereochemistry of the seven-membered cyclic phosphites (94),(99, and (96), prepared from the base-catalysed reaction of triphenyl phosphite and the correThe results suggest sponding diol, has been investigated by lH, 13C,and 31Pr~.m.r.?~ that each of the three heterocycles adopts a different conformation in solution.
Miscellaneous Reactions.-A full report has appeared of the reactions of carbon dioxide and carbon disulphide with tervalent phosphorus aryl esters and amines; the products are ureas and thioureas, respectively.'* The suggested mechanism, previously invoked for similar reactions of carboxylic acids, involves the N-phosphonium salt (97). 0
II
(PhO),PH
+
PfiNH,
+
-
PhNHCONHPh
I I1 H-P-X-C-NHPh
PhNH,
+
PhOH
/o
+
PhOP-H
-0"oPh (97)
I
OH
2,3,4,5-Tetraphenylcyclopent-3-enoneand dimethyl phosphonate are the major products from the base-catalysed reaction of methyl phosphonate with tetracyclone.75 A mechanism involving initial hydride transfer from dimethyl phosphinate anion to the ketone followed by kinetically controlled protonation to give (98) is suggested. 73 74
75
A. C. Guimaraes and J. B. Robert, Tetrahedron Letters, 1976, 473. N. Yamazaki, I. Iguchi, and F. Higashi, Tetrahedron, 1975, 31, 3031. C. J. R. Fookes and M. J. Gallagher, J.C.S. Perkin I, 1975, 1876.
Organophosphorus Chemistry
100 [MeO%]-
+ H
\ MeOP-0
0
+
An unusual rearrangement with elimination of acetonitrile to give (100) occurs on heating the silylated amide (99).7s
(RO),P-N
/
\
SiMe,
COMe
-
(RO),P -0-SiMe, (100)
(99)
The dimer (101) is slowly formed from bis(trimethylsilyl)aminotrimethylsilyliminophosphine on standing at room temperature. The stereochemistry of (101) appears to be fixed, due to a very high (AG;, > 27 kcal mol-l) P-N rotational barrier. 3 Phosphonous and Phosphinous Acids and their Derivatives Gallagher has reported a convenient synthesis of functionalized phosphorinans (102) by Michael addition of methyl hypophosphite to methyl acrylate, followed by baseinduced cyclization.7 8 The secondary phosphine oxide (104) has been reported as an intermediate in the reaction of benzylbis(cc-hydroxybenzy1)phosphine oxide (103) with amines to give (105).7DThe same authors now report the results of direct reaction of (103) with imines * O to give (105) and the reaction of (103) with aldehydes to give acetals (106). M. A. Pudovik, L. K. Kibardina, T. A. Pestova, and M. D. Medvedeva, Zhur. obshchei Khim., 1975,45,2568 (Chem. Abs., 1976, 84,44259). W. Niecke, W. Flick, and S. Pohl, Angew. Chem. Internat. Edn., 1976, 15, 309. 78 M. J. Gallagher and J. Sussman, Phosphorus, 1975, 5, 91. 7 9 A. B. Pepperman and T. H. Siddall, J . Org. Chem., 1975,40, 1373. so A. B. Pepperman and T. H. Siddall, J. Org. Chem., 1975, 40, 2053. A. B. Pepperman, T. H. Siddall, and G . J. Boudreaux, J. Qrg. Chem., 1975, 40, 2056; S. A. Buckler, J. Arner. Chem. SOC.,1960, 80, 4215. 76
77
Tervalent Phosphorus Acids
-
0
11 MeOPH,
+ CH,=CHCO,Me
101 0
It
MeOPCH,CH,CO,Me H lCH,=
C0,Me
r(
0
II PhCH,P(CHOHPh),
CHC0,Me
0
II
+-
-
MeOP(CH,CH,CO,Me),
0
IIH,
PhCH P ’ ‘CH(0H)Ph
CHPhNHR I I/ PhCH P
’ ‘CHOHPh
+ PhCHO
PhCH-NR
In the presence of two moles of reagent, the oxide (103) can act as a source of primary phosphine oxide through loss of both hydroxybenzyl groups.
B u‘,
Optically active phenyl-t-butylphosphine oxide with the same sign of rotation has been prepared by the reaction of Raney nickel with the (+)-selenide (107) and the (+)-sulphide which suggests that the latter compounds have the same sign of rotation for the same absolute configuration. The absolute configuration of (-)phenyl-t-butylphosphine oxide was apparently established by conversion into ( - )methylphenyl-t-butylphosphineoxide, but no details have been given. 82
J. Michalski and Z. Skrzypzynski, J. Organometallic Chem., 1975, 97, C31.
6 Quinquevalent Phosphorus Acids ~
~~
BY R. S . EDMUNDSON
An increase in the output of papers dealing with derivatives of phosphoric, phosphonic, and phosphinic acids during the period under review has required even greater selectivity in the final choice to be included here; about half the published papers are not covered by the present Report. Marked activity has been evident in the general areas of phosphorylation and assignment of configuration in phosphoruscontaining ring systems, but application of these ring compounds to the study of mechanisms of reactions at phosphorus, and in the synthesis of chiral phosphorus compounds, continues to be of particular interest. The final volume of ‘OrganophosphorusCompounds’, edited by Kosolapoff and Maier, contains chapters on phosphonic acids and their derivativesla and organic derivatives of thio- (seleno-, telluro-)phosphoricacids.lb The stereochemistry of optically active phosphorus thio-acids has been reviewed and published lectures have covered such topics as phosphate and phosphonate compounds based on adamantaneS and NN-dihalogeno-amides of phosphoric acids.4
1 Synthetic Methods General.-Triethyl phosphite has been used to achieve stepwise 0-ethylation of phosphoric and benzylphosphonic acids.5 The disulphide linkage in bis(phosphiny1) disulphides is cleaved by ammonia in a suitable solvent to yield the phosphinylsulphenamides (1).
The reaction between phosphorus dichlorides and a-hydroxyiminocarboxylic acids
6
‘OrganophosphorusCompounds’, ed. G. M. Kosolapoff and L. Maier, Wiley, New York, 1976, Vol. 7, (a) Chapter 18, by K. H. Worms and M. Schmidt-Dunker, (b) Chapter 19, by D. E. Ailman and R. J. Magee. M. Mikolajczyk and M. Leitloff, Rum. Chem. Rev., 1975, 44, 670. E. S. Shepeleava, D. M. Oleinik, E. I. Bagri, and P.I. Sanin, Khim. Primen. Fosfororg. Soedin., Tr. Konf., 5th, 1972 (publ. 1974), p. 369 (Chem. A h . , 1975, 83, 147524). A. M. Pinchuk, L. N. Markovskii, T. V. Kovalevskaya, G . S. Fedyuk, T. N. Dubinina, S. I. Zhila, and A. V. Kirsanov, Khim. Primen. Fosfororg. Soedin., Tr. Konf., 5th, 1972, (publ. 1974), p. 51 (Chem. Abs., 1975, 83, 114514). A. Markowska, J. Olejnik, and J. Michalski, Chem. Ber., 1975, 108, 2589. U.S.S.R. P. 483401/1975 (Chem. A h . , 1976, 84, 59738).
102
Qrriiiquevalent Phosphorus Acids
103
or esters yields 1,3,2-0xazaphospholines(2) (see also ref. 49).' Stereoselectivity in the formation of 1,3,2-0xazaphospholidines from phosphorus dichlorides and propanolamines is evidently dependent upon the substituent on nitrogen : a mixture of diastereoisomers of (3) results when R1 = Me but homogeneous isomers are obtained when R1 = Ph.8 ,OR'
Me,,OII
The optically active thiones (4), readily obtainable from ( - )-ephedrine, undergo P-N bond fission, with inversion of configuration at phosphorus, when treated with ethanolic HCl ;this provides a highly recommendable method for the preparation of valuable amounts of optically active acyclic compounds (9,isolable as the S-methyl esters (6).9
E tOII- HCI I'
E'
R"
\
OEt
'H (4)
(6)
not isolated (5)
R*is =S; R2 = Me, or O-alkyl and compounds epimeric at P New, stereospecific syntheses of (+)-(R)- and (-)-(S)-ethyl isopropyl methyl phosphate, (+ )-(R)-0-ethyl 0,s-dimethyl phosphorothioate, and (+)-(R)-ethyl Me
/I$*
0
Em-.
EtO,,
,,Me
MeOIT-IICI
~
c
Me0
0//P\MeNK'
Eta--, ,Me 'P Me0/ \o
Me0 I OMe
(7) 7
U.S.S.R.P. 498313/1976 (Chem. Abs., 1976, 84, 105766).
8
M. A. Pudovik, M. D. Medvedeva, and A. N. Pudovik, Zhur. obshchei Khim., 1975,45, 1390 (Chem. Abs., 1975,83, 131 691). D. B. Cooper, C. R. Hall, and T. D. Inch, J.C.S. Chem. Comm., 1975, 721.
104
Organophosphorus Chemistry
K
R2,R3 = Pri, Et
R1 =
R20, ,OR' "P OH ' h e i ; H,O-H+ ii; MeI(X = S , Rz = PI', R3 = Et)
Me0 OMe
methyl methylphosphonate, starting from the bicyclic compounds (7) and (8) based on D-glucopyranose, have been described.1° Ring opening of the N-methylated 1,3,2-0xaza- and 1,3,2-diaza-phospholidine rings with phosphoric and phosphonic acids yields 2-aminoethyl derivatives of pyrophosphoric and pyrophosphonic acids (9) ; 2-dimethylamino-l,3,2-dioxa-
(9)
X = 0 ox NMe; R = PhO or PI1
phospholans and acyclic dimethylamino-compounds, on the other hand, appear to react very slowly in this manner.ll The interaction of 1,2-dicarbonylcompounds and dihydrazides in 1:1 ratio yields 3,4-dihydro-2H-1,2,4,5,3-tetra-azaphosphepine 3-sulphides (10).l2
R'P(S)(NHNH,),
R?COCORZI (10 )
Phosphoric Acid and its Derivatives.-Triacetyl phosphate l3 and diammonium monoacetyl phosphate14have been obtained by acetylation of phosphoric acid with keten at - 10 to - 15 "Cin diethyl ether and ethyl acetate, respectively; the reaction can be controlled to give 90% yields of either product. Long-chain monoalkyl C. R. Hall, T. D. Inch, G. J. Lewis, and R. A. Chittenden, J.C.S. Chem. Comm., 1975, 720. P. Chabrier and Nguyen Thanh Thuong, Comp -.,rend., 1975, 281, C, 397. l 2 A. F. Grapov, 0. B. Mikhailova, and N. N. Mel'nikov, Zhur. obshchei Khim., 1975, 45, 1392 (Chem. Abs., 1975,83, 131692). l3 A. Ungureanu and C. Liteanu, Rev. Roumaine Chim., 1975,20,721 (Chem. Abs., 1975,83,96367). l4 G. M. Whitesides, M. Siegel, and P. Garrett, J. Org. Chem., 1975, 40, 2516. lo
l1
Quiriquevalent Phosphorus Acids
105
phosphates are obtainable by direct reaction between the alcohol and phosphoric acid at temperatures below 130 "C; at higher temperatures the dehydration of the alcohol becomes more important.ls The phosphoramidic chloride (11) has been employed to phosphorylate phenols and alcohols, including carbohydrates.ls Other activity in phosphorylation chemistry has been mostly concentrated in two main areas. In the first of these, Japanese workers have continued their studies on the use of 2-substituted-4-nitrophenylphosphoric acids. The N-protonated form of the 2-dimethylamino-compound (1 2 ; R = Me) is a better phosphorylating agent than the corresponding 2-diethylaminocompound. The reaction of (12) with hydroxy-amines results in selective O-phos-
phorylation, and with hydroxythiols the S-hydroxyalkyl phosphorothioate is the main product.17Primary hydroxy-groups are selectivelyphosphorylated by the same compounds.ls The pyridinium phenyl phosphate (13) phosphorylates alcohols in pyridine in the presence of triethylamine, but inorganic polyphosphates are formed in the absence of the latter.l* In the second area of interest, the high reactivity of compounds that stems from inherent ring strain in fivemembered ring systems has been exploited in the synthesis of mixed diesters of phosphoric acid. These, for example (15), may be obtained by
cleavage of the corresponding 2-hydroxyphenyl triesters (in turn obtainable from cyclic catechol esters) by lead tetra-acetate or by hydrogenolysis.20Hydrolysis of the benzoxazaphospholines (16; R = alkyl), obtained by transesterification between the corresponding phenoxy-compound and ROH, gives the phosphoramidic acids shown.a1 W. Jasinski and S. Ropuszynski,Przemysl. Chem., 1975,54509 (Chem. Abs., 1975,83,177763). W. S. Zelinski and Z. Lesnikowski, Synthesis, 1976, 185. Y. Taguchi and Y. Mushika, J. Org. Chem., 1975, 40, 2310. la Y. Taguchi and Y. Mushika, Chem. and Pharm. Bull. (Japan), 1975, 23, 1586. l9 Y. Taguchi, Y. Mushika, and N. Yoneda, Bull. Chem. SOC.Japan, 1975,48, 1524. 1o J. Calderon and J. A. Medrano, Anales de Quim., 1975,71,618 (Chem. Abs., 1975,83,178208). 21 T. Koizumi, Y. Yoshida, Y. Watanate, and E. Yoshii, Chem. and Pharm. Bull. (Japan), 1975, l5
l6 l7
23, 1381.
Organophosphoriw Chemistry
106
/
OR OH
H
Ramirez et al. have successfully employed 4,5-dimethyl-1,3,2-dioxaphospholen compounds in their work, summarized in Scheme 1.22 The key intermediate is the
HOCH,
P P OH
o ---P(O) AH
011
"j 0€1
(25) Reagents: i, R1OH-collidine; ii, RCOH; iii, imidazole; iv, dry HCl; v, RZOH-EtsN; vi, COClz; vii, pyridine (R1= Me); viii, MeCN-aq. NazCOs
Scheme 1 22
F. Ramirez and J. F. Marecek, J. Org. Chem., 1975,49,2849; F. Ramirez, J. F. Marecek, and I. Ugi, J. Amer. Chem. SOC.,1975,97, 3809; F. Ramirez, J. F. Marecek, and H. Okazaki, ibid., p. 7181; F. Ramirez, J. F. Marecek, and I. Ugi, Synthesis, 1975, 99; F. Ramirez, H. Okazaki, and J. F. Marecek, ibid., p. 637.
Quinquevalent Phosphorus Acids
107
cyclic R1ester (20), which has normally been obtained by careful hydrolysis of the adduct from biacetyl and the ester (R10)3P,although a better method of preparation of (20) from the same adduct is now available (see ‘Organophosphorus Chemistry’, Vol. 7, p. 106). The same intermediate may be obtained directly from the pyrophosphate (17) and RlOH, or indirectly from the imidazolide (18) or the phosphorochloridate (19). Treatment of (20) with the alcohol R20Hyields the acyclic ester (21), a reaction apparently catalysed by Et,N for primary alcohols but not so for secondary alcohols. Hydrolysis of (21) then yields the desired diester (22). In spite of the ability of all the compounds (17)-(20) to react with primary, secondary, and tertiary alcohols, some selectivity can be achieved. Thus, (17) will phosphorylate (23) and the resultant ester (20) will then react preferentially with the primary hydroxy-group of (24) to give (25). Compound (19) is useful for the phosphorylation of sensitive and (or) poorly nucleophilic alcohols. A new and reliable procedure for the synthesis of 0,s-dialkyl hydrogen phosphorothioates (27) involves the trifluoroacetolysis of the t-butyl esters (26); the method is facilitated by the lack of need to isolate (26).23
The preparation of phosphoramidates from dialkyl phosphites, using the ToddAtherton procedure, has been carried out in two-phase systems containing a phasetransfer agent, for example benzyltriethylammoniumchloride, at 5 mole % concentrati~n.~~ The reaction between dialkyl phosphorocyanatidite and acyl cyanides in dichloromethane at 0 “C parallels that between the same phosphite and 1,Zdicarbonyl compounds, and is probably initiated by attack of tervalent phosphorus on the carbonyl group; the formation of 0-and N-alkyl products, (30) and (29), is an indication of the probable nature (28) of an intermediate.26The extension of the reaction (see ‘Organophosphorus Chemistry’, Vol. 7, pp. 108, 126) to include ethyl phosphorodicyanatidite and 1-keto-estersprovides a route to the 5-phosphabicyclo[3,2,0]heptanes(31) in high yields.28 The reaction between benzoylhydrazineand ethyl or phenyl phosphorodichloridate 5-(2-benzoylhydrazino)-5,6-dihydro-2,8-diphenyl-4~1,3,4,6,7,5-0xatetrayields azaphosphocine 5-oxide (32).27
23 24 25 26
27
A. Zwierzak, Synthesis, 1975, 270. A. Zwierzak, Synthesis, 1975, 507. I. V. Konovalova, L. A. Burnaeva, G. S. Temnikova, and A. N. Pudovik, Zhur. obshchei Khim., 1975, 45, 1003 (Chem. Abs., 1975, 83, 58123). I. V. Konovalova, L. A. Burnaeva, and A. N. Pudovik, Zhur. obshchei Khim., 1975,45, 2558 (Chem. Abs., 1976, 84, 59322). A. F. Grapov, 0. B. Mikailova, and N. N. Mel’nikov, Zhur. obshchei Khim., 1975, 45, 2570 (Chem. Abs., 1976, 84, 59419).
108
Organophosphorus Chemistry 0
I1
R20-PHN
Rz
Me R’ = CN
MeCoR’
(29) ~
4-
m P N C O
Me
CN
R’OP(NCO),
Dialkyl phosphoramidates react with sulphonyl di-isocyanate to give the phosphorylated thiatriazine dioxide derivatives (33),a8 while TMPT and formaldehyde together afford 1,5-dioxo-2,4,6,8,9,11-hexakis(methylamino)-1,5-diphosphabicyclo[3,3,3Jundecane(34) .2
New derivatives and analogues of cyclophosphamide (35; R = H) have been reported so and the diastereoisomeric N-1-phenylethyl derivatives (35 ;
2* 29
3”
Z. Arnold and B. Fiszer, Roczniki Chem., 1975,49, 285 (Chem. Abs., 1975,83, 79203). U.S. P. 3925467/1975 (Chenz. A h . , 1976, 84, 105671). P. B. Farmer and P. J. Cox, J. Medicin. Chem., 1975, 18, 1106.
Quinqiieualent Phosphorus Acids
109
R = PhCHMe) have been prepared and distinguished by n.m.r. spectroscopy.31 Attempts to prepare N-aryl derivatives of cyclophosphamide by cyclization of the phosphoramides (36) proved unsuccessfu1.32 Although this type of reaction has proved to be of great value in the preparation of perhydro-l,3,2-oxazaphosphorines and 1,3,2-oxazaphospholidines when NaOEt, NaOH, or NaH are employed as reagent, in this instance the bis(chloroethy1)amide side-chain presents a further possible reaction site. However, steric effects, also considered as an explanation for instances of failure of the reaction (see ‘Organophosphorus Chemistry’, Vol. 7, p. 111) may be operating adversely. Phosphonic and Phosphinic Acids and their Derivatives.-Further fundamental information on important reactions for preparing phosphonic acid derivatives has
(37)
appeared. The formation of 2,4-dimethyl-l,3,2-dioxaphosphorinan 2-oxide (38) from the sodium salt of the cyclic hydrogen phosphonate (37)and Me1 proceeds stereospecifically, with preservation of configuration of the starting material.33 A recent Russian report discloses that oxidative chlorophosphonation of saturated hydrocarbons may be initiated by hydroperoxides present in the hydrocarb~n.~* Some doubts regarding the relative importance of compounds (39)and (41) uis a uis the carbocation (40) in the phosphorylation of terminal alkenes by PCl, have been resolved, at least partially. Although compounds of types (39) and (41) (after treatRCHClC&P(O)CL, --+ [R6HCH2P(0)CI,] (39)
(40)
--+ RCH=CHP(O)CJ
(41)
ment of the intermediate RCH2CH2k13PCI,complex with SO,) are very often found together as products of this reaction (although there may be a distinct bias towards one or the other), it has not been determined whether (39) and (41) are formed independently or whether (41) is produced via (40)from (39). The rate of phosphorylation appears to be controlled to some extent by the ability of R to conjugate. Electron release by R (R = aryl, alkoxy, or aryloxy) increases the stability of (40)and thus favours the formation of (41).When R = alkyl, elimination of a proton is aided by electron withdrawal by P=O. The initially formed complex RCHClCH2hC13PC&, produced by competing chlorination, must lose HCl more readily than (39), so that (39), which is stable at room temperature, may correspond to (40),that is unstable under the same condition^.^^ 31 32 33 34 35
G. Zon, Tetrahedron Letters, 1975, 3139; R. Kinas, K. Pankiewicz, and W. Stec, Bull. ,4cad. polon. Sci., Skr. Sci. chim., 1975, 23, 981 (Chem. Abs., 1976, 84, 180177). H. Hamacher, Arch. Pharm., 1975, 308, 290. K. Lesiak, B. Uznanski, and W. Stec, Phosphorus, 1975, 6 , 65. T. M. Mal’kovskaya and N. M. Lebedeva, Nefepererab. Nefekhim. (Kazan), 1974, 2 , 42 (Chem. Abs., 1976, 84, 150039). V. G. Rozinov, V. V. Rybkina, E. F. Grechkin, and A. V. Kalabina, Zhur. obshchei Khim., 1975, 45, 1643 (Chem. Abs., 1975, 83, 113490), 1644 (Chern. Abs., 1975, 83, 205443).
110
Organophosphorirs Chemistry
PCI, (followed by SOz) converts ethyl thioethers into alkylthiovinylphosphonic dichlorides (42) 36 and acetals into alkoxy(ary1oxy)vinylphosphonic dichlorides (43).37With the same reagents, t-butyl alcohol yields the phosphonic dichloride (44).3*
Me2CClCH, P(0) cl,
RXCH=CHP(O)Cl,
X =S
(42)
x
(43)
(44).
= 0
Other phosphonic dichlorides (43, (46) have been obtained from phosphorodichloridites and chlorinated dimethyl MeOCHClP(0) Cl,
C1,CHOMe
(ClCH,),O
ROW2
f
*
C I C ~ O c ~ P (cl, 0) (46)
(45)
The reaction between phenylphosphonic dichloride and 2-naphthol in the presence of pyridine to give, ultimately, 2-naphthyl phenylphosphonic acid has been shown to be usefully influenced when DMF is added before the naphthoL40 Amongst the reported syntheses of phosphonic esters, one of cyclohexylphosphonic esters depends on treatment of cyclohexanthione with trialkyl phosphites followed by desulphurization of the intermediate esters (47) with Raney nickel.4L
os
(RO),P_
~
~
~
(
o
R Raney )Nip 2
0; (OR)'
(47)
Improved yields of epoxyphosphonates of type (48) are reported for a developmentof existing synthetic methods, involvingmixing of stoicheiometric amounts of hydrogen phosphonate, m-halogeno-ketone, and a l k ~ x i d e . ~ ~ Bicyclic compounds possessing fused 1,3,2-0xathiaphospholan and tetrahydrothiophen rings are obtainable by reaction between a suitable halohydrin (49) and the anhydride (50), followed by cyclization of the intermediate (51) to give (52).43
37 38 39 40
41 42
43
K. A. Petrov, M. A. Raksha, and Le Dong Khai, Zhur. obshchei Khim., 1975,45, 1503 (Chem. Abs., 1975, 83, 164302). V. V. Moskva, T. Sh. Sitdikova, A. I. Razumov, T. V. Zykova, R. A. Salakhutdinov, and G. F. Namanova, Zhur. obshchei Khim., 1975,45, 1494 (Chem. Abs., 1975,83, 179222). L. Maier, Phosphorus, 1975, 5, 223. T. F. Kozlova, A. F. Grapov, and N. N. Mel'nikov, Zhur. obshchei Khim., 1975, 45, 1392 (Chem. Abs., 1975, 83, 114 562). W. R. Purdum, K. D. Berlin, S. Kelly, and L. G. Butler, J. Org. Chem., 1976, 41, 1 1 60. 2. Yoshida, S. Yoneda, andT. Kawase, Chem. Letters, 1975,279 (Chem. Abs., 1975,83, 10284). B. Springs and P. Haake, J. Org. Chem., 1976, 41, 1165. 0. N. Grishina, L. A. Mukhamedova, N. A. Andreev, and M . A. Nechaeva, Zhur. obshchei Khim., 1975, 45, 731 (Chem. Abs., 1975, 83, 58943).
111
Quiriquevalent Phosphorus Acids S
€IS
II
(49)
A convenient synthesis of ‘half-derivatives’of thiophosphonic acids starts from the corresponding phosphonic dichloride, with isolation of the trimeric thiophosphonic anhydride (53)44a and subsequent reaction of this with amines and alcohol~.~~b S
Treatment of diphenacylphosphinic acid with P,O, in hot toluene leads to 4-hydroxy-2,G-diphenyl-4H-1,4-oxaphosphorin 4-oxide (54) rather than to the phosphinic acid anhydride.45 0
ll
O = P /OYP 70)
Ph (PhCOCH,),P(O) OH
Y*O,\
/-=-7PO,H
Q
0
P-0
Ph
0
w (54)
)P=O
II
(55)
The full dehydration of methylenediphosphonic acid by DCC yields the cage compound (55).46 A useful review of the chemistry of a-aminophosphonicacids has been published.47 Treatment of a-aminomethylphosphonic mono-esters with bromoacetyl halides 44 45
46 47
(a)0. N. Grishina, N. A. Andreev, and E. E. Sidorova, Zliur. obshchei Khiin., 1975, 45, 2344 (Chem. Abs., 1976, 84, 59662); (b) L. Maier, Phosphorus, 1975, 5, 253. L. S. Moskalevskaya and G . K. Fedorova, Zhur. obshchei Khim., 1975,45, 950 (Chem. Abs.,
1975, 83, 43454). T. Glonek, J. R. van Wazer, and T. C. Myers, Inorg. Chem., 1975, 14, 1597. K. Prajar and J. Rachon, Z . Chem., 1975, 15, 209.
112
Organophosphorus Chemistry
yields perhydro-l,4,2-oxazaphosphorin-5-ones(56).48 2-0xo-5,6-dihydro-1,3,2oxazaphosphorines (57) have been prepared as indicated.49
HOC,H,C
P"
RO
CN),
Ph,kHR'[CH2InCOg -%
/I 0
(32) 0
Reagents: i, Ph3P=CHR1; ii, heat.
Scheme 8
Formate esters behave as typical carbonyl compounds in reactions with a number of ylides, eliminating phosphine oxide and forming vinyl ethers, e.g. (33).36Stabilized phosphoranes are able to condense with the carbonyl group of cyclic thioanhydrides (34).3sQuinoline derivatives, e.g. (35), are obtained from the condensation of dicarboalkoxy-ylides with i~ocyanates.~~ Benzoyl isothiocyanates and keto-phosphoranes give quantitative yields of (36), which are unreactive in Wittig reactions but can be readily oxidized by selenous The products obtained from reactions (Scheme 9) with the triazolinedione (37) depend upon the stability of the ylide 33 34 35
36
37 38 39
J. P. Schmid, M. Piraux, and J. F. Pilette, J. Org. Chem., 1975, 40, 1586. K. Kise, Y. Arase, S. Shiraishi, M. Seno, and T. Asahara, J.C.S. Chem. Comm., 1976, 299. V. Subramanyam, E. H. Silver, and A. H. Soloway, J. Org. Chenz., 1976, 41, 1272. W. Flitsch, J. Schwiezer, and U. Strunk, Annalen, 1975, 1967. H. Wittmann and D. Sobhi, 2. Naturforsch., 1975, 30b, 766 (Chem. Abs., 1976, 84, 4834). A. F. Tolochko, I. U. Megera, L. V. Zykova, and M. I. Shevchuk, J . Gen. Chem. (U.S.S.R.), 1975,45,2116. W. Lwowski and B. J. Walker, J.C.S. Perkin I , 1975, 1309.
Organophosphorus Chemistry
184 Ph,P=CHCO,Et
f
HC0,Et --+ EtOCH=CHC02Et
(3 3) CH,CO,Et S
Ph,P=CHCOAr
f
+ F%,P=CHCO,Et
SCNCOPh
_+
+
Ph,P=CCOAr
ArCOCOCSNHCQPh
HzSeo3
I S=CNHCOPh (36)
Ph,P=yCONHNMe, Ph,P=CHR
+
7
Me$-N
*&x, But
I
C0,Et
Ph,P=CCONHBut
1
(37)
COPh Scheme 9
Organometallics. Methylenetriphenylphosphoranes form stable 2 :1 complexes (38)"O and 1 : 1 complexes (39)*l when treated with copper(1) o r silver(1) chlorides. Stable adducts (40) can also be obtained from the reaction of methylenetrimethylphosphorane and metal t r i a l k y l ~ . ~ ~ Ph,PCHMCHPPh,
I t R R
Ph,PCH-MCl
[
i,,
(38)
(39)
I.
M = CuorAg Me,P=CH,
+
MR, --+ M&&MR, (40)
M = Ga,In,orTl R = Meor Et 40 41 42
Y . Yamamoto and H. Schmidbaur, J. Organometallic Chem., 1975, 96, 133. Y. Yamamoto and H. Schmidbaur, J. Organornetallic Chem., 1975, 97, 479. H. Schmidbaur, H. J. Fuller, and F. H. Kohler, J. Organometallic Chem., 1975, 99, 353.
185
Ylides and Related Compounds R,P=CHz
+
__t_
[
]
?5
Me,Si-SiMe,
Me
---+ R,P=CHSiCH$iMe, Me (41)
Me, Si=)Sih4e2
R = MeorEt Me,MCH=C=O
+ Ph,P=CHCO,Me
-+ Me,MCH=C=CHCO,Me
(43)
Silylated ylides (41) are produced from alkylidenetrialkylphosphoranes and 1,3disilacyclobutanes.43These reactions are thought to proceed via penta-alkylphosphorane intermediates since cleavage of 1,l-dimethylsilacyclobutanegave only (42). Penta-alkylphosphorane intermediates are also inferred from the products of the reaction of these ylides with silacyclobutane, from which hydrogen is eliminated.44 However, the cyclobutanering is left intact when the reaction is carried out with more bulky ylides (Scheme Silicon- and germanium-substituted allenes have been prepared by the reaction of monometallated ketens with stable ylides, e.g. (43).46 R,P=CH,
+ H,Si
3
"=Y (Me,CH),P=C'
'si3 H'
MeSi
H Scheme 10 43
44 45 46
H. Schmidbaur and W. Wolf, Chem. Ber., 1975,108,2834. H. Schmidbaur and W. Wolf, Chem. Ber., 1975,108,2842. H. Schmidbaur and W. Wolf, Chem. Ber., 1975,108,2851. V. Y.Orlos, S. A. Lebedev, S. V. Ponomarev, and I. F. Lutsenko, J . Gen. Chem. (U.S.S.R.), 1975, 45, 696.
186
Organophosphorus Chemistry
Miscellaneous. An interesting synthesis of 1,l-difluoro-1-alkenes from ylides and chlorodifluoromethane has been described?' The ylide acts both as a carbene generator and trapping agent (Scheme 11). Ph,P=CR1R2
+ HCF,Cl
ph,P=CR'Rz
+
Ph3kHR1RZ+ [:CF,]
-+
Ph,P
[:CF,]
+ F2C=CR1R2 88-100%
Scheme 11
A rather complex mixture of products is obtained from the reaction of benzylidenetriphenylphosphorane and CS2.48The major product from the reaction of diphenyl disulphide with methylenetriphenylphosphorane is tris(pheny1thio)methane (44) and only a trace of the insertion product bis(pheny1thio)methane is isolated.4vPresumably the salt (45) is deprotonated before it can react with the phenylthioate anion (Scheme 12). a-Thiocarbonyl-stabilizedylides (46) are obtained O from the reaction of ylides with S-alkyl thiolcarboxylate~.~ Ph,P=CH,
PhS- + PhSCH2$Ph,
* (PhS),CH,
(45)
(PhS),CH
t--
PhS-
+ (PhS),CH$Ph,
(44) Reagents: i, (PhS)z; ii, Ph3P=CHz.
PhSCH=PPh,
Scheme 12
Alkylidenetriphenylphosphoranes are oxidized by phosphite-ozone ad duct^.^^ Ylides of the general structure (47) afford alkenes (R1or R2 = H) or ketones (R1or R2 # H). N.m.r. evidence suggests that the former reaction proceeds via a quinquecovalent phosphorus intermediate (Scheme 13). The mechanism of hydrolysis of benzylidenetriphenylphosphorane is similar to It is proposed that the low polarities that of the corresponding phosphonium of the solutions in which ylides are usually hydrolysed increase the equilibrium 4' 48 49
50
5l 52
G . A. Wheaton and D. J. Burton, Tetrahedron Letters, 1976, 895. G. Purrello and P. Fiadaca, J.C.S. Perkin I , 1976, 692. L. Field and C. H. Banks, J. Org. Chem., 1975, 40,2774. H. Yoshida, H. Matsuura, T. Ogata, and S. Inokawa, Bull. Chem. SOC.Japan, 1975,48,2907. H. J. Bestman, L. Kisielowski, and W. Distler, Angew. Chem. Znternat. Edn., 1976, 15, 298. A. Schnell, J. G. Dawber, and J. C. Tebby, J.C.S. Perkin If, 1976, 633.
187
Ylides and Related Compounds
R’
/
R’,R2 # 11
R’ ‘C=PPh,
R”
+
A.
+ (PhO),P=O
‘C=O
+ %,Po
R2/
‘2
(Ph0)P
(47)
(PhO),P=O
+ Ph,PO + R2CH0
J
R*HC=PPh,
H R2 ‘\
+-
R2CH=CHR2
P P h ,
R2 Scheme 13
concentration of the hydroxyphosphorane at the expense of the phosphonium hydroxide (Scheme 14). Rate increases of more than lo6 were obtained by reduction of the water content in the medium. P h , k H , Ph Br- \t,
Ph,kH,Ph OHPh,P=CHPh
f
H,O
&
T/i
% Ph,PCH,Ph A
Ph,PO
P
OH I
-ICIi,Ph
Reagents: i, NaOH; ii, OH-.
Scheme 14
2 Phosphoranes of Special Interest The ylide anion (48) reacts with a variety of electrophiles at the terminal carbanion site to form p-keto-ylides, e.g. (49). 63,64 The reaction between the ylide derived from cyclobutyltriphenylphosphonium bromide and cyclobutanone gave a reasonable yield of bicyclobutylidene (50).66 53 54
55
E. A. Sancaktar, J. D. Taylor, J. V. Hay, and J. F. Wolfe, J . Org. Chem., 1976,41, 509. M. Schwarz, J. E. Oliver, and P. E. Sonnet, J. Org. Chem., 1975,40, 2410. L. K. Bee, J. Beeby, J. W. Everett, and P. J. Garratt, J. Org. Chern., 1975, 40, 2212.
188 Ph;P=CHCOCH3
Organophosphorus Chemistry BuLi
*
PIi,P===CHCOCH2-
C'13CH0 t
PII,P=CIICOCH,CI-IOHCI-I, (49)
(48)
(SO) 31% An acid- and base-sensitivesiloxycarboxylicacid was treated with NN'-carbonyldiimidazole and the resulting imidazolide (51) transformed into the desired ylide using one equivalent of salt-free methylenetriphenylphosphorane in benzene, rather than two equivalents as usually recommended. Coupling, under neutral conditions, with two equivalents of aldehyde (52) gave a mixture of diastereomeric epoxythiolates (Scheme 15).66 0
II
ph3P=CHCY
0
Scheme 15
a-Oxo-y-enaminomethylenephosphoranes (53) can be obtained from readily available isoxazole derivative^.^' These ylides show a reactivity comparable to that of those stabilized by a single carbonyl group, reacting with aromatic aldehydes to give compounds (54) which can be hydrolysed by aqueous HCl to the tricarbonyl-substituted alkenes (Scheme 16). Michael additions occur between (diethoxyviny1idene)triphenylphosphoraneand carbonyl compounds which have an a-CHz. The initial products eliminate EtOH to 56
S. Masamune, H. Yamamoto, S. Kamata, and A. Fukazawa, J . Amer. Chem. Soc., 1975, 97,
57
P. Bravo and C. Ticozzi, Chem. and Ind., 1975, 1018.
3513.
189
Ylides and Related Compounds
RT=O
R,C+O R'H *H=cHAr ,N
il I II
0
RCCHCCH=CHAr
0 0 Reagents: i,
H2,Raney
(54) Ni; ii, BuLi-THF; iii, ArCHO; iv, dil. HCI.
Scheme 16
give the ylides ( 5 3 , which with aldehydes give en01 ethers (Scheme 17).68When the a-positions are blocked, allenes may be formed, e.g. (56).6s OEt
Ph,P=C=C(OEt),
f
R'CH,CR2
ll
r
I I II OEt 0
Ph,P=CHCCH@CR*
0
J-E~OH
YEt R3CH=CHd=CR1COR2
204 cyclophosphazenes impart flame resistance. 8 Molecular Structures of PhosphazenesDetermined by X-Ray Diffraction Methods Compound
Comments
Plane containing C-N=P coplanar with triazene ring, P=N 1.622(5) A, C-N-P angle 121O Pph,]' [R~,,(co),H,]-' No data on P-N-P skeleton in preliminary publication Layer structure in crystal with extensive N -H * N hydrogen-bonding. Mean P-N(endo) 1.565 A, P-"(exo) 1.601 A Free base of hydrochloride where N,P,C&(NHPri), structure reported previously. Distorted (geminal) boat-shaped ring; protonation does not Naffect geometry of C12Py fragment \N=
[Ph3P=N-
195 196 197 198 199 200 201 202
203 2 04 205 206 207 208
209
Ref.
205
206 207
208
Earlier assignment corrected; irregular puckered ring, mean P -N(exo) 1.633 8,
209
Centrosymmetric, with phosphazene rings in slight boat conformation, with mean P-N 1.599(2) A, P-P 2.210(2) A
139
M. Fukuhara and S . Ozawa, Japan. Kokai 74 132398 (Chem. Abs., 1975, 82, 172556). M. Fukuhara, Japan. Kokai 75 142900 (Chem. Abs., 1976, 84, 107027). M, Fukuhara and S . Ozawa, Japan. Kokai 74 133470 (Chem. Abs., 1975, 83, 29808). K. Nagai, H. Okada, I. Takeuchi, and Y. Okutani, Japan. Kokai 75 139096 (Chem. Abs., 1976, 84, 61 116). V. Frank, E. W. Lard, and E. E. Stahly, U.S.P. 3867344 (Chem. Abs., 1975, 83, 29 151). V. A. Bykov, A. A. Volodin, G. I. Kurochkina, and L. M. Romanov, Russ. P. 455982 (Chem. Abs., 1975, 83, 60681). R. M. Murch and E. E. Stahly, U.S.P. 3933738 (Chem. Abs., 1976, 84, 136659). E. 0. Hook, G. R. Berbeco, and A. S. Obermayer, U.S.P. 3867186 (Chem. Abs., 1975, 82, 157 786). I. Masuda, T. Midorikawa, R. Kawamura, Y. Goto, and H. Kawano, Japan. Kokai 74 124323 (Chem. Abs., 1975, 82, 172465). M. Mizuno, K. Igi, and T. Akasawa, Japan. Kokai 75 48055 (Chem. Abs., 1975,83, 133205). T. S . Cameron, Kh. Mannan, M. Biddlestone, and R. A. Shaw, 2. Nuturforsch., 1975, 30b, 973. V. G. Albano, A. Ceriotti, P. Chini, G. Ciani, S. Martinengo, and W. M. Anker, J.C.S.Chem. Comm., 1975, 859. S . Pohl and B. Krebs, Chem. Ber., 1975, 108,2934. W. Polder and A. J. Wagner, Cryst. Struct. Comm., 1976, 5 , 253. T. T. Bamgboye, M. J. Begley, and D. B. Sowerby, J.C.S. Dalton, 1975, 2617.
Phosp hazenes Compound
210
211 212
23 1 Comments
Ref.
Bicyclic structure with mean phosphazene ring P-N 1.602(8) A. Pyramidal P-NEt-P nitrogen atom with P-N 1.772, 1.693 A
114
Centrosymmetric chair conformation with P-N 1.665(6) and 1.572(7) A
210
Centrosymmetric, with conformation like that of NsPs(0Me)ls. Mean P-N(endo) 1.548(9)A, one very large P-N-P angle 170.2’
21 1
Determined at - 140 “C. Ring has boat conformation with P=NP 1.574(4) A, P=NS 1.606(3) A
212
H. P. Calhoun, R. T. Oakley, N. L. Paddock, and J. Trotter, Canad. J . Chern., 1975,53,2413. H. P. Calhoun, N. L. Paddock, and J. Trotter, J.C.S. Dalton, 1976, 38. F. Van Bolhuis and J. C. Van de Grampel, Acta Cryst., 1976, B32, 1192.
11 Photochemical, Radical, and Deoxygenation Reactions BY R. S. DAVIDSON
1 Photochemical Reactions Further studies have been made of the quenching of excited singlet states by triphenylphosphine1*2and triphenyl phosphite.2 Rate constants were determined for the quenching of the fluorescence of a variety of 9-mono- and 9,lO-di-substituted anthracenes by the ph0sphine.l The constants approached the diffusion-controlled limit when electron-withdrawing substituents were present. The constants were markedly lower for anthracenes containing electron-donating substituents. It was proposed that high rate constants were obtained when quenching occurred by a predominantly electron-transfer process and that the lower rate constants reflected a change in the quenching mechanism to one in which an intermediate complex was formed where binding energy was mainly due to exciton resonance. However, it should be pointed out that the experimentally determined rate constants (k,) are composite rate constants i.e. ArH*(Sl)
k, k, + Ph3P + [ArHPh3P]* +ArH(S0) + PhsP(S0)
k-I
and lower than diffusion-controlled values are often obtained because of the increasing efficiency of the reverse process, i.e. inc~eases.~ Thus, before any real conclusions can be reached about the mechanism of the quenching process, the effect of temperature upon the quenching constants (k,) will have to be determined. Triphenylphosphine and triphenyl phosphite both quench the fluorescence of fluorenone (k, = 4.5 x logand 2.1 x lo81 mol-1 s-l in benzene solution).2 Since the quenching efficiency is insensitive to solvent polarity, it was concluded that the quenching complex had little charge-transfer character. The lower reactivity of the phosphite compared with phosphine and the lack of quenching by triphenylphosphine oxide demonstrated that the efficiencyof quenching was dependent on the availability of the lone pair on phosphorus. There has been the very interesting report that dialkyl(hydroxymethy1)phosphines rearrange to dialkylmethylphosphine oxides on irradiation with U.V. light.4 No mechanistic details are available. Irradiation of the phosphine (1) causes a molecular rearrangement, and it was proposed that the primary chemical reaction is C-P bond cleavage.6 a
5
M. E. R. Marcondes, V. G. Toscano, and R. G. Weiss, J. Amer. Chem. SOC.,1975, 97, 4485. R. H. Lema and J. C. Scaiano, Tetrahedron Letters, 1975, 4361. F. D. Lewis and C. E. Hoyle, J . Amer. Chem. SOC.,1975,97, 5950. B. Lippsmeier and K. Hestermann, Ger. Offen. 2 407460 (Chem. A h . , 1976, 84, 17557). W. Winter, Tetrahedron Letters, 1975, 3913.
232
Photochemical, Radical, and Deoxygenation Reactions
233
I
Ph
Irradiation of dianisyl alkyl phosphates gives alkyl phosphates and 4,4'-dimethoxybiphenyl in yields exceeding 90%.6 As stated by the authors, this type of reaction appears to have promise for the synthesis of nucleotides. The phosphonium compounds (2) normally give the phosphonates (3) quite readily on heating. However, when R = Ph the salts are thermally stable but will rearrange under the influence of U.V. radiation.'
Addition of tristearyl phosphite to polyethylene containing ferric acetylacetonate has been shown to decrease the stability of the polymer towards photo-oxidation.* 2 Phosphinidenes and Related Species A comprehensive review of the chemistry of phosphinidenes has been published,g and topics such as their preparation, spectroscopic properties, and reactions used to trap such species are dealt with. The chemistry of phosphinidene oxides and sulphides is also reviewed. Several reactions, e.g. of (4) (Scheme 1),lo (5),11 and (6),12 have been reported in which phosphinidene oxides are probably produced, although there is no conclusive evidence for the generation of such species. R. A. Finnegan and J. A. Matson, J.C.S. Chem. Comm., 1975, 928. C. Shin, Y. Yonezawa, Y. Sekine, and J. Yoshimura, Bull. Chem. SOC.Japan, 1975,48, 1321. * T. T. Sat0 and D. Hideo, Kobunshi Ronbunshu, 1975, 32, 598 (Chem. Abs., 1976, 84, 44898). U. Schmidt, Angew. Chem. Znternat. Edn., 1975, 14, 523. lo T.H.Chan and K. T. Nwe, Tetrahedron, 1975,31, 2537. l1 A. J. Fry and L.-I,. Chung, Tetrahedron Letters, 1976, 645. l2 C. J. R. Fookes and M. J. Gallagher, J.C.S. Perkin I , 1975, 1876.
Organophosphorus Chemistry
234
Reagents: i, Et3N; ii, R1C-CR2; iii, A.
R' Br
\i/ I
Rz
*
MeO-P=O
A
Scheme 1
MeO--Y-0
d
-
R'RZC=CR'R2
RL Br R2
+
MeOP=O
2Me OPH,
11
0 (6)
MeOP=O
+ H,P-0
+ MeO-+ BH
The reaction of cis- and trans-stilbene oxides with phenylphosphonothioic dichloride in the presence of magnesium gives cis- and trans-stilbene and (7).13 Phenylphosphinidene sulphide is postulated as being an intermediate. The zwitterion (8) bears a remarkable similarity to the controversial perepoxides which are thought to be intermediates in the reaction of singlet oxygen with alkenes.
3 Radical Reactions Several radical anions such as (9) have been prepared and their e.s.r. spectra recorded.'* It was found, from calculations, that dn-pn interactions are of much greater significance than pn-pn interactions. The previous report l5 that U.V. irradiation of phosphine in krypton gives PH, has been criticized.16The e.s.r. spectrum, previously interpreted as being due to PH, radicals, has been re-interpreted as being due to (H,PPH,)+= radicals. The calculated spectrum of this radical is in good agreement with the one obtained experimentally, and also there is a very close resemblance between this and the spectrum of radical (10). The phosphoranyl radical Me,PH has l3 l4
l5
S. Nakayama, M. Yoshifuji, R. Okazaki, and N. Inamoto, Bull. Chem. SOC.Japan, 1975, 48, 3733. A. G. Evans, J. C . Evans, and D . Sheppard, J.C.S. Perkin II, 1976, 492. C. A. McDowell, K. A. R. Mitchell, and P. Raghunathan, J . Chem. Phys., 1972, 57, 1699. T. A. Claxton, B. W. Fullam, E. Platt, and M. C. R. Symons, J.C.S. Dalton, 1975, 1395.
235
Photochemical, Radical, and Deoxygenation Reactions PhP(S) Cl,
+ Mg
+ Ph,,
- *XPh Ph
.H O-FPh
Ph,
(7) (Mixture of isomers)
.H
H WO+P h
I Ph (8)
M~,LPM~,
I I
s- sbeen prepared by y-irradiation of triinethylphosphine at - 196 O C . 1 7 The radical (Me,PPMe,)+* was also formed in this system. It was noted that the replacement of apical groups by groups less electronegative than RO in phosphoranyl radicals PX., leads to a transfer of spin density from the central atom to the o-orbitals, leading to a destabilization of the radical. Thus, as spin density in the apical bonds is increased, the tendency for phosphoranyl radicals to undergo an a-scission reaction is increased. There is good experimental evidence to support the view that a-scission occurs preferentially from apical positions.18 The kinetics of the a-scission reactions of R1R2P(OBut), have been examined by e.s.r. spectroscopy. In none of the cases examined could the reactivity of the radicals be explained solely on the ease of C-P bond fission, and therefore the conclusion was reached that it is the relative stabilities of the permutational isomers of the phosphoranyl radicals which are of prime importance. Thus in the case of (lla) and (llb), it is the less stable (lla) which undergoes the a-scission reaction. Just the opposite view has been put forwardxgto explain the reactivity of (12) towards the thiyl radicals (13a-c). From the fact that substitution is favoured over oxidation for the series (1 3c) > (13b) > (13a) it was concluded that the relative strengths of the C-P and C-S bonds controlled the outcome of these reactions. From a study of the products of the light-catalysed 17
1s 19
K. Nishikida and F. Williams, J. Amer. Chem. SOC.,1975, 97, 5462. J. W. Cooper and B. P. Roberts, J.C.S. Perkin II, 1976, 808. W. G. Bentrude and P. E. Rogers, J. Amer. Chem. SOC.,1976, 98, 1674.
236
OrganophosphorusChemistry
PhCH,P(OEt), +
(12)
_ . f
KP(OEt),
Oxidation
(13) a: R = Pri b: R = But c: R = 4-MeC,H4CCI, RSP(OEt), Substitution
II
S
addition of thiols to diphenylvinylphosphine(14) it appears that the addition of thiyl radicals to phosphines may well be reversible.20When R = Et, Prn, Bun, or Ph product (15) is exclusively obtained, whereas when R = But or PhCH2, (16) is the Ph,PeHCH,SR
Rp
Ph,KH=CH2 (14)
RSH
*
Ph,PCH,CH,R (15)
Ph,kH=CH,
I
SR
--+ Ph,PCH=CH,
II
sole product. Thermodynamic parameters for pseudorotation of several fluorinecontaining phosphoranyl radicals, e.g. EtOPF3and (EtO),PF,, have been obtained.21 y-Irradiation of trimethyl phosphite, trimethyl and tripropyl phosphorotrithioite, di-isopropylphosphinyl chloride, diphenylphosphinyl chloride, and diethylphosphorochloridodithioite has been shown to give radicals which appear to be derived uia phosphoranyl radicals generated by electron addition to the tervalent phosphorus compounds.22The reactions of these spectroscopically undetected phosphoranyl radicals are shown in Scheme 2. Other reactions observed included the formation of
R
R' + OPL,
II
X = OorS
S
Scheme 2
21 22
D. H. Brown, R. J. Cross, and D. Millington, Inorg. Nuclear Chem. Letters, 1975, 11, 7 8 3 ; J.C.S. Dalton, 1976, 334. I. H. Elson, M. J. Parrott, and B. P. Roberts, J.C.S. Chem. Comm., 1975, 586. B. W. Fullam and M. C. R. Symons, J.C.S. Dalton, 1975, 861.
237
Photochemical, Radical, and Deoxygenation Reactioris +.
species such as L,PPL, and L3P-PL3. The e.s.r. spectra of the radicals derived by photolysis of triethyl phosphite2, have been reinterpreted in the light of these results, and the radicals identified as (EtO),P and EtP(OEt),.,, The observed products of reactions can be easily interpreted as being produced via these radicals. It has been proposed that the radicals derived by y-irradiation of phosphites, phosphates, chlorophosphites, and chlorophosphates, and which have been detected by e.s.r spectroscopy, are radicals derived by an electron-capture reaction, e.g. formation of (17) and (18).24 ?-Irradiation of fluorophosphines in sulphur hexafluoride gives
Me'
+ (MeO),POH
Me'
f
d
o\P/H Me0
No
(MeO),PO
-
f
MeH
(1 7 )
MeH + MeOP(: 0)0(1 8)
fluorine-containing phosphoranyl radicals.26 When phosphorus pentahalides are y-irradiated, phosphoranyl radicals are obtained in addition to -*PCls and 2-'Pc16 radicals.26y-Irradiation of phosphorus oxyhalides2 7 and alkyl and aryl phosphorodichloridates28 at 77 K gives phosphoranyl radicals by an electron-attachment reaction. When polar solvents are used the phosphoranyl radicals can break up either by loss of halide ion or by formation of phosphino radicals.28The radicals obtained by y-irradiation of phenylphosphinic and phenylphosphonic acids have been examined by e.s.r. At room temperature, phenylphosphinic acid gave PhP( :O)OH and cyclohexadienyl radicals having the partial structures (19) and (20). In contrast, irradiation at 77 K gave radical (21). Annealing of the matrix led to the observation of radicals (22). The proton in this radical was shown by
deuterium labelling to have been originally bound to phosphorus. Cyclohexadienyl radicals of the type (19) and (20) were also obtained from phenylphosphonic acid and diphenylphosphinic acid. Attempts have been made to demonstrate that the formation of radicals such as (24) involves prior formation of phosphoranyl radicals such 23 24
25 26 27 28 29
K. Terauchi and H. Sakurai, Bull. Chem. SOC.Japan, 1969, 41, 1736. C. M. L. Kerr, K. Webster, and F. Williams, J. Phys. Chem., 1975, 79, 2650, 2663. A. J. Colussi, J. R. Morton, and K. F. Preston, J. Phys. Chem., 1975, 79, 1855. S. P. Mishra and M. C. R. Symons, J.C.S. Dalton, 1976, 139. A. R. Boate, J. R. Morton, and K. F. Preston, J . Phys. Chem., 1976, 80, 409. D. J. Nelson and M. C. R. Symons, J.C.S. Dalton, 1975, 1164. S. P. Mishra and M. C. R. Symons, J.C.S. Perkin ZI, 1976, 21.
Organophosphorus Chemistry
238
as (23).30Examination of the radicals produced by y-irradiation of dimethyl phenylphosphonous acid in a propan-2-01 matrix gave indications that the sequence (23)+(24) does operate. Radical (25) was also detected. Radicals having a similar
RO + PhP(OMe),
--+--P
OR ,OMe
I
I
\.4r OMe
-
I_f
+ , O R
&-P-OMe ‘ 0 hfe
OMe OMe
structure have been produced by electrochemical oxidation of phosphines in solution31 Well-resolved e.s.r. spectra were obtained. By the use of open-shell CNDO$ calculations, the geometries of a variety of phosphoranyl radicals have been determined.32The validity of using this type of calculation is attested to by the fact that the calculated hyperfine coupling constants for the radicals are in close agreement with the experimentally determined ones. The anion of di-isopropyl phosphorothiolothionic acid (26) reduces hydroxyl radicals, and the radical (27) so produced is detectable by e . ~ . rAttempts .~~ to observe these radicals by photolysis of the free acid were unsuccessful. However, the use of a spin trap (e.g. N-methylene-t-butylamineN-oxide) enabled radicals in this system and other closely related systems [e.g.with (28)] to be observed by e.s.r. spectroscopy.
Photolysis of peroxydisulphate anions in aqueous solution produces the SO,-= sulphate radical. This radical reacts with phosphoric acid and its anions to generate phosphorus-containing radicals which can be trapped by such compounds as fumaric 30
31 32 33 34
M. C. R. Symons, Mol. Phys., 1975, 30, 1921. W. B. Gara and B. P. Roberts, J.C.S. Chem. Comm., 1975, 949. J. M. F. van Dijk, J. F. M. Perrings, and H. M. Buck, J. Amer. Chem. SOC., 1975, 97, 4836. 6. Brunton, B. C. Gilbert, and R. J. Mawby, J.C.S. Perkin I I , 1976, 650. 0. P. Chawla and R. W. Fessenden, J. Phys. Chem., 1975,79, 2693.
239
Photochemical, Radical, and Deoxygenation Reactions
Electron attachment to dinucleoside phosphates leads to the formation of radical ions in which the electron has added to the more easily reduced heterocyclic base.35 Several examples have been reported of the formation of phosphorus-containing persistent radicals, e.g. (29) and (30).36Addition of a variety of radicals to 2,4,6-tri-tbutylphosphorin produces persistent radicals of the type (31). The e.s.r. spectrum of (32) indicates that its preferred conformation is the one in which the half-filled
,But
+ Se-c 'But
(EtO),E;=o
---+
B u y 8 Bu'/,-Se
II
,P(OEt),
(32)
p-orbital eclipses the Se-P bond.37Phosphorins such as (33) react with diazonium salts in methanol to give products (34) and (35).38
bBUt ArN,X
MeOH
*
qAr
But
(3.3)
Several very stable radicals (e.g.those derived from AIBN) react with tetraphenylbiphosphine in a homolytic displacement reaction.39Phosphoranyl radicals, e.g. (36), were postulated as being intermediates. The reaction of the triplet state of olefin (37) is thought to occur via a similar mechanism. In the presence of cuprous chloride, trichloromethylphosphonic dichloride (38) adds to a variety of alkenes and dienes via a free-radical process.4oThere have been 35
36 37 38 4o
M. D. Sevilla, R. Failor, C. Clark, R. A. Holroyd, and M. Pettei, J. Phys. Chem., 1976,80,353. D. Griller, K. Dimroth, T. M. Fyles, and K. U. Ingold, J. Amer. Chem. SOC.,1975, 97, 5526. J. C. Scaiano and K. U. Ingold, J.C.S. Chem. Comm., 1976,205. 0 . Schaffer and K. Dimroth, Chem. Ber., 1975, 108, 3281. R. Okazaki, Y.Hirabayashi, K. Tamura, and N. Inamoto, J.C.S. Perkin I , 1976, 1034. H. Rosin and H. Asscher, J. Org. Chem., 1975, 40, 3298.
240
Organophosphorus Chemistry Ph,PPPh,
A
-t
Me,C-N-N-CMe,
Ph,iPPh,
l
Ph,PCMe, + Ph,P
Me,CCO,Me
I
I
C0,Me
---+
C0,Me
(36)
C0,Me
Ph,C=CH2m
Ph,P-PPh,
Ph,PPI’h,
cuc1,
CUCl
+ CI,CPOCl, (38)
-
+ Cl,CPOCI,
MeCHCH,
*
c1 MeCHCH,L--PCI,
I ll
c1 0
I
CUQ, %
MeCHCH2C-PC1,
I
c1
I II
Cl 0
further investigations of the reaction of phosphorus trichloride with toluene in the presence of oxygen in an attempt to find a satisfactory mechanism to account for the formation of 4-methylphenylphenylmethane.41Other studies include the hydrogenand the electrochemical reduction of abstraction reactions of recoil 32P phosphacyanine dyes.43
4 Deoxygenation and Desulphurization Reactions A review has been published which describes the use of deoxygenation reactions in synthesis.44There have been some interesting uses of the deoxygenation of 1,4endoperoxides, prepared by the addition of singlet oxygen to cyclohexa-l,4-dienes. Epoxide (39)45and the benzene diepoxide (40)4shave been synthesized in this way. Pyrazine (41) reacts with singlet oxygen to give a 1,4-endoperoxide which is reduced by triphenylphosphine to (42).47 The chemistry of arene oxides is of particular interest because of the possible role of these compounds in chemical carcinogenesis. Deoxygenation reactions have been successfully used in the synthesis of these compounds, e.g. (43),4* (44),49 and (45).50 Another application of deoxygenation reactions has been to the polemical problem as to the mechanism of ozonolysis of olefins. An ozonide was allowed to react61awith acetaldehyde labelled at oxygen to give a molozonide, which was deoxygenated by triphenylphosphine. Examination of the products showed that the label was located at the ether oxygen, which once again makes the refined Criegee mechanism51bthe favourite. There is a valuable discussion 41 42 43
44 45 46
*7 48
49
50
51
Y. Okamoto and H. Sakurai, Bull. Chem. SOC.Japan, 1975, 48, 3407. 0. F. Zeck, G. P. Gennaro, and Y.-N. Tang, J . Amer. Cliem. SOC.,1975, 97, 4498. H. Oehling, F. Baer, and K. Dimroth, Tetrahedron Letters, 1976, 1329. T. Mukaiyama, Angew. Chem. Internat. Edn., 1976, 15, 94. M. Oda, M. Oda, and Y. Kitahara, Tetrahedron Letters, 1976, 839. C. H. Foster and G . A. Berchtold, J . Org. Chem., 1975, 40, 3743. J. L. Markham and P. G . Sammes, J.C.S. Chem. Comm., 1976,417. G. W. Griffin, S. K. Satra, N. E. Brightwell, K. Ishikawa, andN. S. Bhacca, Tetrahedron Letters, 1976, 1239. R. M. Moriarty, P. Dansette, and D. M. Jerina, Tetrahedron Letters, 1975, 2557. S. C. Agarwal and B. L. Van Duuren, J . Org. Chem., 1975, 40,2307. (a) K . L. Gallaher and R. L. Kuczkowski, J. Org. Chem., 1976, 41, 892; (b) N. L. Bauld, J. A. Thompson, C. E. Hudson, and P. S. Bailey, J . Anzer. Clzem. SOC.,1968, 90, 1822.
Photochemical, Radical, and Deoxygenation Reactions
241
Ph,P
(Me,N),P
CHO
of the use of labelling techniques in examining the chemistry of ozonides. The ozonide of triphenyl phosphite has found use in the synthesis of alkenes via the oxidation of ylides.62 52
H. J. Bestmann, L. Kisielowski, and W.Distler, Artgew. Chern. Internat. Edn., 1976, 15, 298.
242
Organophosphorus Chemistry
The deoxygenation of some penicillin and cephalosporin sulphoxides has been accomplished by the use of phosphorus p e n t a ~ u l p h i d e .The ~ ~ ~reactive species responsible for deoxygenation was not identified. A particularly mild method for reducing sulphoxides to sulphides involves the reaction of the sulphoxide with 2-chloro-l,3,2-benzodioxaphosphole at room f e m p e r a t ~ r e . ~ Yields ~ in excess of 80 % were reported. Acyl-nitroso-compounds are deoxygenated by triphenylphosphine to give isocyanates, and reaction via the zwitterion (46) was po~tulated.~*
The reaction of several derivatives of N-nitrosoanilines with tervalent phosphorus compounds has been shown to give diazo-benzenes, which in some cases give benzynes in low yield.55A kinetic study has been made of the deoxygenation of 2-nitrobenzylidenederivatives of substituted anilines by several tervalent phosphorus esters and a m i d e ~The . ~ ~reaction is very sensitive to the nature of the deoxygenating agent, and the order of reactivity observed was (Me,N),P > (EtO),PMe z EtOPPh, > EtOP(NEt 2)2 z (Et0)2PNC5Hlo> (MeO)3Pz(EtO),P z (PriO)3P. Tervalent phosphorus compounds having the phosphorus atom contained in a five-membered ring are relatively unreactive. This is attributed to the fact that ring strain in the tetragonal intermediate produced by attack upon the nitro-group is much greater than in the starting phosphorus compound. There has been a series of papers on the deoxygenation of 2-nitrophenyl phenyl ethers and sulphides. Of particular interest has been the role of pentacovalent intermediates (47) in these reactions. These are certainly not the primary intermediates in the reactions but are of great importance in determining the course of the reaction. Their genesis is thought to be that shown in Scheme 3.57 A number of pentacovalent compounds of the type (47) have been isolated from reactions of ether^.^'-^^ The structures of the compounds were established by n.m.r. spectroscopy and X-ray ~rystallography.~~~ 5 9 The stability of these intermediates 53 54
55 S6
57
59
59
(a)R. G . Micetich, Tetrahedron Letters, 1976,971 ;(b) D. W. Chasar and T. M. Pratt, Synthesis, 1976,262. J. E. T. Corrie, G . W. Kirby, and R. P. Sharma, J.C.S. Chem. Comm., 1975, 915. J. I. G . Cadogan, A. G. Rowley, J. T. Sharp, B. Sledzinski, and N. H. Wilson, J.C.S. Perkin I , 1975, 1072. M.-A. Armour, J. I. G . Cadogan, and D. S. B. Grace, J.C.S. Perkin l I , 1975, 1185. J. I. G . Cadogan, D. S. B. Grace, P. K. K. Lim, and B. S. Tait, J.C.S. Perkin I , 1975, 2376. J. I. G . Cadogan, D. S. B. Grace, and B. S. Tait, J.C.S. Perkin I , 1975, 2386. J. I. G . Cadogan, R. 0. Gould, S. E. B. Gould, P. A. Sadler, S. J. Swire, and B. S. Tait, J.C.S. Perlcin I , 1975, 2392.
Photochemical, Radical, and Deoxygenation Reactions - Nitrene
-
Zwitterionic products
X = OorS
243
-+ I.
0
Z
Q
R
3
R'
i
(47)
Scheme 3
accounts for the fact that these reactions failed to give phenoxazenes. The intermediates are photochemically labile, and carbazoles, e.g. (48), have been successfully synthesized by employing this reaction.so Deoxygenation of 2-nitrophenyl phenyl sulphides gives phosphoramidates (49) via
(47)
X T S R' = R2 = Me R3 = OH
R4 = Et Rs = OKt
7
+ a t N-P(OEt),
MeoMe I
OH
(49) J. I. G. Cadogan, B. S. Tait, and N. J. Tweddle, J.C.S. Chem. Comm., 1975, 847.
244
Organophosphorus Cheniistry
intermediates such as (47).61a2 * When the ortho-positions in the ring attacked by the intermediate derived from the nitro-group are free, phenothiazines are produced. Normally the thiazaphosphoranes (47; X = S) rearrange so rapidly that they cannot be isolated."lb However, their intermediacy can be detected by 31Pn.m.r. spectroscopy.61uFurthermore, if the tervalent phosphorus reagent has its phosphorus atom contained in a five-membered ring, stable thiazaphosphoranes can be isolated.61aTheir structures have been verified by X-ray crystallography. Once again, the deoxygenation of nitro-compounds has found use in the synthesis of heterocyclic c o r n p ~ u n d s . ~Several ~ - ~ ~ 2-nitrophenyl-substitutedindoles, e.g. (50) and (51), are deoxygenated on reaction with triethyl phosphite.62The reaction of H
+
\
Me
S-chloro-phosphinothiolateswith phosphorus trichloride leads to desulphurization.65 The reaction of sulphenates with phosphines leads to deoxygenation,66and not (as previously reported) to desulphurization. Even when the ion pair (52; R1 = R2 = Me, RS = Bun) was generated from the sulphide (53), the reaction still led to R'SOR' + R3P --+ R10-PR3,
I SR2
+ I
R'SR2 +
R10$R33 t
SR2
R10$R3,
I
SR2 (52)
R' OR2
+
R3,B (5 3)
61 62
63
65 G6
(a) J. I. G . Cadogan, R. 0. Gould, and N. J. Tweddle, J.C.S. Chem. Comm., 1975, 773; (b) J. I. G. Cadogan and B. S. Tait, J.C.S. Perkin I , 1975, 2396. A. H. Jackson, D. N. Johnston, and P. V. R. Shannon, J.C.S. Chem. Comm., 1975, 911. I. M. McRobbie, 0. Meth-Cohn, and H. Suscliitzky, Tetrahedron Letters, 1976, 925. T. Kametani, Y. Fujimoto, and M. Mizushima, Heterocycles, 1975, 3, 619. J. Omelanczuk, P. Kielbasinski, J. Michalski, J. Mikolajczak, M. Mikolajczyk, and A. Skowronska, Tetrahedron, 1975, 31, 2809. D. H. R. Barton, D. P. Manly, and D. A. Widdowson, J.C.S. Perkin I , 1975, 1568.
245
Photochemical, Radical, and Deoxygenation Reactions
deoxygenation. By means of suitable labelling, it was shown that the disulphides (54) and (55) are desulphurized by triphenylphosphine by different me~hanisms.~? Presumably the ion pair (56b) can collapse to give the phosphine sulphide more readily than can (56a) because of the steric effect of the diphenylmethyl group. PhCH2SS*Ac
Ph3P F
PhCH,S*Ac + Ph,PS
S* = %
(54)
P&CHSS*Ac
W3P
: ph,PS*
+ PhCHSAc
(55)
Ph$HS$Ph, 'SAC (56d
AcSSPh, kHPh,
(56b)
Further use has been made of the reaction of disulphides with tervalent phosphorus compounds in phosphorylation reactions, e.g. in the synthesis of (57).68 S
II
+ Ph,P
0
+ ROCSPPh,
SCOR
II
S
OH
Desulphurization of compounds such as (58) has again attracted attention.6QIn the case of (58), complete desulphurization gives (60), and the reaction was shown by trapping experiments to occur via the zwitterion (59). The desulphurization of disulphides by tervalent phosphorus compounds has been the subject of a review.'O The light-induced desulphurization of benzylic sulphides by phosphites has found further use in the synthesis of cyclophanes which exhibit the formation of intramolecular charge-transfer complexes, e.g. (61) and (62).71 67 68
6Q 70
S. Kawamura, A. Sato, T. Nakabayashi, and M. Hamada, Chem. Letters, 1975, 1231. H. Takaku, M. Yamana, and Y. Enoki, J. Org. Chem., 1976,41, 1261. T. Sat0 and T. Hino, Tetrahedron, 1976, 32, 507. E. J. Griffith and M. Grayson, 'Topics in Phosphorus Chemistry', J. Wiley, New York, 1975, Vol. 8. H. Tatemitsu, T. Otsubo, Y. Sakata, and S. Misumi, Tetrahedron Letters, 1975, 3059.
9
246
Organophosphorus Chemistry
/
.1
EtOCH=CII,
(59)
(63) X = 0 , S, or Se
Another synthesis of olefins has been described in which the desulphurization of thiirans by triphenylphosphine is featured.72There have been many reports of the synthesis of compounds of the type (63). These form charge-transfer complexes with acceptors such as tetracyanoquinodimethane which have metallic properties. The
72
A. 1. Meyers and M. E. Ford, Tetrahedron Letters, 1975, 2861.
Photochemical, Radical, and Deoxygenation Reactions
247
desulphurization of (64), which yields (63; X = 0, R = CN), has been the subject of an intensive ~tudy.7~ Compounds (65) and (66) are proposed intermediates whereas (67) and (68) are compounds which have been isolated from the reaction mixture. 5 Deselenation Reactions The three papers in this section are all concerned with the preparation of compounds such as (63). Compounds (69),74(70a),74(70b),75and (71) 76 were usually converted
(70) a: X = S ; Y = CH, b: X = Se; Y = S
MeSe
(Me01, P f
(63; X = Se, R = MeSe)
MeSe (71)
into derivatives of (63) in quite high yields by reaction with phosphites. Synthesis of these compounds by desulphurization of the correspondingthiocarbonyl compounds often afforded disappointingly low yields of the olefins (63).74
73 74
M. G. Miles, J. S. Wager, J. D. Wilson, and A. R. Siedle, J. Org. Chem., 1975, 40, 2577. H. K. Spencer, M. V. Lakshmikantham, M. P. Cava, and A. F. Garito, J.C.S. Chem. Comm., 1975, 867.
75
76
C. Berg, K. Bechgaard, J. R. Andersen, and C. S. Jacobsen, Tetrahedron Letters, 1976, 1719. E. M. Engler, D. C. Green, and J. Q. Chambers, J.C.S.Chem. Comm.,1976, 148.
I2 Physical Methods BY J. C. TEBBY
The abbreviations PIII, PIV, and PV refer to the co-ordination number of phosphorus and the compounds in each subsection are usually dealt with in this order. A number of relevant theoretical and inorganic studies are included in this chapter. In the formulae the letter R represents hydrogen, alkyl, or aryl, X represents electronegative substituents, Ch represents the chalcogenides (usually oxygen and sulphur), and Y and Z are used to indicate a wide variety of substituents. 1 Nuclear Magnetic Resonance Spectroscopy The very high accuracy which may be obtained by the pulsed Fourier transform method has been demonstrated using o-phenylene phosphorochloridite.l Biological Applications.-Following the extensive n.m.r. studies of the stereochemistry of nucleotides2attention is now being turned to linking the n.m.r. results with circular dichroismS, and other proper tie^.^ Phosphorus n.m.r. spectroscopy has been used to assist oligonucleotide synthesis6and has been applied to model and biological membrane systems.*Procedures have been described for the measurement of an order parameter for the phosphate head group in phospholipid bilayen6 Structural and dynamical studies of mixed chlorophyll-phosphatidylcholinebilayers have been reported. Phosphonium phosphatidylcholine has been prepared from phosphonium choline (1) in which the nitrogen atom of choline is replaced by a
phosphorus atom. It gives a unique and sharp phosphorus-31 signal which is distinct from the phosphate resonances and also sensitive to shift reagents.8There appears to be minimal perturbation of the membranes9 and the derivatives exhibit similar 1 2
3 4
5 6
7 8 Q
L. Ernst and D. N. Lincoln, J. Mugn. Resonance, 1974, 16, 190. C. R. Lee, Diss. Abs. Internnt. ( B ) , 1976, 36, 3928; R. H. Sarma and R. J. Mynott, Jerusalem Symp. Quantum Chem. Biochem., 1973, 5, 591. G. Reitz and W. Pfleiderer, Chem. Ber., 1975, 108, 2895. A. V. Azhaev, A. A. Kraevskii, and V. L. Florent’ev, Nucleic Acids Res., 1975,2, 1433. D. G. Knorre, A. S. Levina, and T. N. Shubina, Izuest. sibirsk. Otdel. Akad. Nuuk, Ser. khim. Nauk, 1975, 118. A. C. McLaughlin, P. R. Cullis, M. A. Hemming, D. I. Hoult, G. K. Radda, G. Ritchie, P. J. Seeley, and R. E. Richaras, F.E.B.S. Letters, 1975, 57, 213. F. Podo, J. E. Cain, and J. K. Blasie, Biochim. Biophys. Actu, 1976, 419, 19. E. Sim, P. R. Cullis, and R. E. Richards, Biochem. J., 1975,151, 555. E. Sim and A. Pasternak, Biochem. J., 1976, 154, 105.
248
Physical Methods
249
temperature-dependent spectra to phosphatidylcholine.* Studies of 5’-guanosine monophosphate,1° tubercidin 5’-phosphate,11 and the hydration of phosphatidylethanolamine12have also appeared. Use of very high magnetic fields, which may be obtained from super-conducting magnets, permits the chemical shielding anisotropy to dominate dipolar broadening. In this way, order parameters have been estimated for lipid phosphates.13 Proton decoupling has been used to remove PH dipolar broadening so as to reveal the tensorial information contained in the chemical shielding anisotropy of rigid or slowly moving phospholipid molecules.14In addition the principal values and orientation of the shielding tensor were determined from the 31Pspectrum of a single crystal of phosphorylethanolamine.The broader 31P signals of t-RNA at high field (65 kG) are attributed to chemical shift anisotropy.16 The 31Pn.m.r. spectra of developing tadpoles showed that the main phosphorus component was yolk phosphoprotein.ls Inorganic phosphate (ca. 30 mmol/embryo) was detected at the swimming tadpole stage. It appeared that the phosphate groups of the nucleotide triphosphates were bound in uiuo to a divalent cation. The middle phosphate groups of polyphosphates have been detected in the 145.7 MHz 31P spectra of intact yeast ce1ls.l’ A preliminary report of high-resolution 31P n.m.r. spectroscopy of normal and malignant tissues discusses the possible use of n.m.r. in cancer therapy.ls Phosphorus n.m.r. has also been used to determine the pKa values of myo-inositol hexaph~sphatel~ and the interactions of phosphates with haemoglobin.2o Chemical Shifts and Shielding Effects.-Phosphorus-3I. The positive shifts ( 8 ~ ) which are reported in this chapter are upfield from 85 % phosphoric acid. 8p of PI Compounds. Methylidynephosphine (2) has dp +32.0 p.p.m.,21 which is approximately 35 p.p.m. upfield of protonated derivatives of this compound.22a Thus the chemical shifts are similar to ordinary phosphines and their salts.
10 11
la 18 14
15 16 17
T. J. Pinnavaia, H. Miles, and E. D. Becker, J. Amer. Chem. Soc., 1975,97,7198. F. E. Evans and R. H. Sarma, Cancer Res., 1975,35, 1458. R. P. Taylor, Arch. Biochem. Biophys., 1976,173, 596. B. De Kruyff, P. R. Cullis, G. K. Radda, and R. E. Richards, Biochim. Biophys. Actu, 1976, 419,411; P. R. Cullis, B. De Kruyff, and R. E. Richards, ibid., 1976,426, 433. S. J. Kohler and M. P. Klein, Biochemistry, 1976, 15, 967. M. Gueron and R. G. Shulman, Proc. Nat. Acad. Sci. U.S.A., 1975,72, 3482. A. Colman and D. G . Gadian, European J. Biochem., 1976,61, 387.
J. M. Salhany, T. Yamane, R. G. Shulman, and S. Ogawa, Proc. Nut. Acad. Sci. U.S.A., 1975, 72, 4966.
l8 19 20
21
K. Zaner and R. Damadian, Physiol. Chem. Phys., 1975, 7 , 437. A. J. R. Costello, T. Glonek, and T. C. Myers, Carbohydrate Res., 1976, 46, 159. C. Ho, Ann. New York Acad. Sci., 1974,241 ;A. J. R. Costello, W. E. Marshall, A. Omachi, and T. 0. Henderson, Biochim. Biophys. Acta, 1976,427, 481. S. P. Anderson, H. Goldwhite, D. KO,A. Letsou, and F. Esparza, J.C.S. Chem. Comm., 1975,
744. 22
‘Organophosphorus Chemistry’, ed. S. Trippett (Specialist Periodical Reports), The Chemical Society, London, (a) 1975, Vol. 7 , Chap. 12; (b) 1970, Vol. 1, Chap. 11; (c) 1973, Vol. 5, Chap. 11.
250
Organophosphorus Chemistry
8~ ofPII1 Compounds. The chemical shifts of the phospholans (3) allow the estimation of the relative configurations in these The cis-2,3-diphenylphospholans, e.g. (3; R = Ph, X = 0),resonate at lower field than the trans-isomers. For other substituents the reverse generally applies. The stereochemistry of the dioxaphosphorinans (4), which has been rationalized in terms of lone-pair interaction^,^^ also manifests itself in stereo-dependent chemical shifts.26The strong dependence of 8~ on the steric disposition of the phosphorus groups on a cyclohexane ring has enabled the determination of conformational free-energy differences between (5) and (6).2s The Me I
PH, and PMe, groups follow the trend for methyl groups, with the axial group appearing more upfield. The opposite is true for the PCI, and four-co-ordinate groups. The reversal of the effect for the PCl, group is most striking (ASP 14.3 p.p.m.), showing that steric compression does not always produce shielding. By lowering the temperature, the individual conformers were observed directly, and AG * values calculated from Tc were in good agreement with those calculated from the averaged chemical shifts. It was evident that replacement of the 4-methyl group by the t-butyl group had only a small effect on 6~ of the equatorial phosphorus groups. The disappearance of the 31Psignal for (5 and 6; R = Me) near Tc occurred as a consequence of the very large difference in 8~ (axial) and 8~ (equatorial). 6~ of PIv Compounds. The reactions of alkyl-lithium reagents with methylphosphonium salts give lithium salt adducts (7) and not pure methylenephosphoranes (8). This accounts for the similarity of the chemical shifts of ylides and corresponding salts which has been observed in several cases. Other salts such as the ethyl and isopropyl compounds give the ylides if the solution of salt and organolithium reagent is stirred for at least 2 h. CND0/2 Calculations indicate that the lithium ion does not significantly alter the electron density or conformation about the methylene group except that the phosphorus atom loses electron density.27The subject of d-orbital
26
A. Zschunke, H. Meyer, and K. Issleib, Org. Magn. Resonance, 1975, 7 , 470. R. F. Hudson and J. G. Verkade, Tetrahedron Letters, 1975, 3231. T. J. Bartczak, A. Christensen, R. Kinas, and W. J. Stec, Tetrahedron Letters, 1975, 37, 3243. M. D. Gordon and L. D. Quin, J. Amer. Chem. SOC.,1976,98,15; J.C.S. Chem. Comm., 1975,
27
T. A. Albright and E. E. Schweizer, J. Org. Chem., 1976, 41, 1168.
23 24 25
35.
Physical Methods
25 1
participation continues to attract much attention.28SCF MO calculations on ylides show that coulombic attraction can account, on its own, for the short C-P bond.29 The trimethylfluorophosphonium ion (9; R = Me) resonates well downfield ( 8 ~ - 142.7 p.p.m.) of the triphenyl analogue (9; R = Ph; 8~ -93.7 ~.p.m.).~O This follows the trend of quaternary salts and phosphine oxides. The pronounced 10 p.p.m. upfield shift upon replacing the ,!?-methylgroup of the phospholen (10; Y = Me; BP -76.0 p.p.m.) by a ,&rnethoxy-group is attributed to a resonance interaction by the methoxy-group in (10; Y = MeO) with the phosphorus atom through the double bond.31The resultant increase in dn-p,, bonding could replace the loss of dn--pnbonding which is thought to be the cause of the downfield shift for cyclic phosphine oxides compared to acyclic oxides. The deviation from a plot of YP-o against 8p for the ethyl esters (11) when the group Y is ethoxy, diethylamino, and acetyl has also been attributed to dn-p, c ~ n j u g a t i o nIn . ~error, ~ it was reported in the previous volume22a that some mixed chalcogenide anhydrides showed unusual shielding. The shifts were downfield, as is usual for mixed ligands and shown also by the thio-esters (12) and the corresponding alkylated derivatives (1 3).33 In the latter work the shifts were rationalized in terms of the electronegativitiesof the ligands. The methyl thiophosphonates (14) have also been The position of the selenide 0
0
II
YP(OEt),
S
I1
(EtO),-,PEt
SEt
I
(EtO), -.P'Et X-
I(/SR MeP, OR
atom in the selenopyrophosphates has a large influence on BP. Thus the symmetrical pyrophosphate (15) has d~ -0.6 whereas for (16) 8p(se) is -43.6 ~ . p . m The . ~ ~cisgeometry of the phosphorocyanates (17) causes the phosphorus atom to resonate 4-5 p.p.m. upfield of the trans-isomer for both the oxides and the ~ e l e n i d e sThe .~~ nitrile group exhibits its usual shielding effect in all the isomers.
28
W. I. Shiau, Diss. Abs. Internat. ( B ) , 1975,36,2817; N. Inamoto, Kagaku No Ryoiki, 1975,29, 254; R. I. Yurchenko, 0. M. Voitsekhovskaya, and I. N. Zhmurova, J. Gen. Chem. (U.S.S.R.),
29
M.-H. Whangbo, S. Wolfe, and F. Bernardi, Canad. J. Chem., 1975, 53, 3040. F. See1 and H. J. Bassler, 2. anorg. Chem., 1975, 418, 263. S. G. Borleske and L. D. Quin, Phosphorus, 1975, 5, 173. V. E. Bel'skii, R. F. Bakeeva, L. A. Kudryavtseva, A. M. Karguzova, and B. E. vanov, Bull. Acad. Sci. U.S.S.R., 1975, 24, 1511. R. Radeglia, J. Schulze, and H. Teichmann, Z . Chem., 1975, 15, 357. A. A. Abduvakhabov, A. A. Sadykov, Kh. A. Aslanov, N. N. Godovikov, and A S. Sadykov, Doklady Akad. Nauk Uzbek. S.S.R., 1974,31, 30. D. S. Rycroft and R. F. M. White, J.C.S. Chem. Comm., 1974, 444. B. Uznanski and W. J. Stec, Synthesis, 1975, 11, 735.
1975,45, 1927. 30 31 32 33 34
35
36
252
Organophosphorus Chemistry
6~ of Pv and PVI Compounds. The chemical shifts of a number of derivatives of the
monocyclic oxyphosphorane (18) have been rec~rded.~' The chemical shifts of the spirophosphoranes (19) varied little (43.7 to 45.0p.p.m.) as R was varied from methyl through a series of aryl substituent~.~~ The resonances at - 19 p.p.m. which appear when DMF or pyridine are mixed with phenylphosphonyl dichloride have been attributed to the complexes (20);39resonances at + 1 and - 1 p.p.m. were assigned to the dissociated molecules. Five-co-ordinate Arbuzov intermediates (21 ;
= OEt) have been detected in the reactions of halogen with a cyclic p h o ~ p h i t e ; ~ ~ the reaction with chlorine gave a resonance at 6~ + 35 and bromine gave a resonance at BP 195 p.p.m. The latter is at higher field than the tribromo-compound (21 ; X = Y = Br; 6~ 189 p.p.m.) and the chlorodibromo-compound (21 ;X = Br, Y = C1; BP 131 p.p.m.). Formation of six-co-ordinate compounds from spirooxyphosphoranes has been reported.41The chemical shifts are to high field of the corresponding oxyphosphoranes. Carbon-13. Steric compression by axial P substituents produces a 'so-called' y-effect by their interaction with the two axial protons on the same side of the ring, and there is a resultant upfield shift of the carbon atoms bearing the axial protons. This effect has been noted for a number of dioxaphosphorinans (22)42143 as well as for phosphorinans.22aA small but significant shift of the C-4 resonance occurs when the
Y
+
+
+
OH (24) phosphorinanone (23) is converted into its PIv derivative^.^^ The effect is observed for the phosphorinanols and phosphorinans, and it is therefore independent of both the hybridization of the C-4 atom and the presence of substituents at C-4. It is also 37
38
39 40
41
42 43
44
C. Malavaud and J. Barrans, Tetrahedron Letters, 1975, 3077. D. Houalla, T. Mouheigh, M. Sanchez, and R. Wolf, Phosphorus, 1975,5, 229. W. R. Purdum, K. D. Berlin, S. J. Kelly, and L. G. Butler, J. Org. Chem., 1976, 41, 1160. A. Skowronska, J. Mikolajczak, and J. Michalski, J.C.S. Chem. Comm., 1975, 791. A. Munoz, G. Gence, M. Koenig, and R. Wolf, Bull. SOC.chim. France, 1975,909; A. Munoz, G. Gence, M. Koenig, and R. Wolf, Compt. rend., 1975,280, C, 485; A. Munoz, M. Sanchez, M. Koenig, and R. Wolf, Bull. SOC.chim. France, 1974, 2193. W. J. Stec and A. Okruszek, J.C.S. Perkin I, 1975, 1828. W. G. Bentrude and H. W. Tan,J. Amer. Chem. SOC.,1972,94,8222; 1973,95,4666. J. J. Breen, S. 0. Lee, and L. D. Quin, J. Org. Chem., 1975,40,2245.
Physical Methods
253
independent of the size of the phosphorus substituent and the position of the conformational equilibrium. The 13Cn.m.r. spectrum of the P I V derivatives of (23) in aqueous solutions indicated that the ketone is in equilibrium with substantial amounts of the diol. In fact, solutions of the oxides at 10 "C were completely in the diol form (24). Several bicyclic phosphorinans such as (25) have been prepared.46 When the P-substituent is an axial phenyl group, as in (25), the y-effect, discussed above, is cancelled and there is a net deshielding effect of the starred carbon atoms. The shielding of the C-1 atom of the vinylphosphonium salts (26) increased with Ph
I
H
Y
PO(OMe),
increased electron-donor power of Y .46 The correspondingslight but definite decrease in the shielding of the C-1 phenyl carbons together with changes in coupling constants supported increased dn-pn conjugation. The chemical shift of the C-1 atom of the phosphonium ylide (8; R = Ph) ( 6 0.4p.p.m.) ~ is at higher field than that previously reported, which was the chemical shift of the lithium adduct (7; R = Ph).27The stereochemical dependence of 6c in phosphonates has been investigated, using models such as (27); the gauche-y shift of the PO(OMe), group was found to be ca. 2 ~ . p . m . ~ ~ Hydrogen-I. The HA signal of the cyclic phosphonates (28) moved upfield to 6 6.2 p.p.m. when the N-aryl ring possessed two ortho-methyl groups.48The shielding effect is even larger for the phosphorane (29), and HA appeared at 6 5.9 p.p.m.
Studies of Equilibria and Shift Reagents.-N.m.r. studies of the exchange of halogen in boron trihalide adducts of trimethylphosphine, its oxide, and ~ u l p h i d e and ,~~ exchange of chloro- and methoxy-groups between methylphosphino and methyl-silyl or -germyl moieties,6ohave been reported. The rates of ionization of phosphoranes 45 46
47 48
49 50
J. R. Wiseman and H. 0. Krabbenhoft, J. Org. Chem., 1976,41, 589. T. A. Albright, S. V. Devoe, W. J. Freeman, and E. E. Schweizer, J. Org. Chem., 1975,40,1650 G . W. Buchanan and C. Benezra, Canad. J. Chem., 1976,54,231. J. I. G. Cadogan, D. S. B. Grace, and B. S. Tait, J.C.S. Perkin Z, 1975, 2386. M. J. Bula and J. S. Hartman, Canad. J . Chem., 1975, 53, 326. K. M. Abraham and J. R. Van Wazer, J . Znorg. Nuclear Chem., 1975, 37, 541.
0rganophosphor us Chemistry
254
such as (30) cannot be determined directly since the salt (31; X = PhO) is not observed in the n.m.r. However, lineshape analysis of the spectrum of a 1 :1 mixture of (30) and (31 ; X = S03CF3)allowed the equilibrium rates to be calculated over a range of temperatures. It was also shown that very fast or-proton +/
MeP(OPh),
MeG(OPh), X-
CH,P-OPh \Y
I’h,$NH ArO-
exchange via ylide intermediates (32) was also occurring. Similar intramolecular A general computer reactions of imino-compounds (33) have also been program has been developed for n.m.r. lineshape analysis of intermolecular exchange in non-first-order multi-spin The program gives detailed mechanistic information. Equilibrium mixtures of condensed phosphates have been studied.54 Shift reagents have been used for the configurational and conformational analysis of cyclic phosphites (34).55 The reagent Eu(fod), moved HA of the vinylphosphine oxide (35) twice as far downfield as the corresponding proton in the spectrum of the
Z - i ~ o m e rThe . ~ ~isomers of the cyclic phosphonate (36) were assigned from the effect of Eu(dpm), on the methyl signal.57Shifts of the butyl signals of tributyl phosphate by europium chloride have also been recorded.58 Pseudorotation.-A number of spirocyclic phosphoranes possess square-pyramidal structures rather than the trigonal-bipyramidal structures previously assumed, and this could have important consequences on the interpretation of their variabletemperature spectra. There is, as yet, no evidence that acyclic or monocyclic phosphoranes favour the square-pyramidal geometry, and the variable-temperature lH 51 52 53
54
55 56
57 58
D. I. Phillips, I. Szde, and F. H. Westheimer, J. Amer. Chem. Sac., 1976, 98, 184. H. €3. Stegmann, G. Bauer, E. Breitmaier, E. Herrmann, and K. Schemer, Phosphorus, 1975,5, 207. A. D. English, P. Meakin, and J. P. Jesson, J. Amer. Chem. SOC.,1976, 98, 414, 422. M. Watanabe, Chubu Kogyo Daigaku Kiyo, 1973,9, 73; W. E. Morgan, T. Glonek, and J. R. Van Wazer, Znorg. Chem., 1974, 13, 1832; A. J. R. Costello, T. Glonek, T. C. Myers, and J. R. Van Wazer, ibid., p. 1225. Yu. Yu. Samitov, A. A. Musina, L. I. Gurarii, E. T. Mukmenev, and B. A. Arbuzov, Bull. Acad. Sci. U.S.S.R., 1975, 24, 1407. H. Koeppel, U. Lachmann, and K. D. Schleinitz, J. prakt. Chem., 1975, 317, 425. M. V. Sigalov, V. A. Pestunovich, V. 1. Glukhikh, M. Ya. Khil’ko, V. M. Nikitin, M. F. Larin, and B. A. Trofimov, Bull. Acad. Sci. U.S.S.R., 1975, 24, 1645. V. Yastrebov, 0. V. Galaktionova, E. N . Lebedeva, and S. S. Korovin, Zhur. neorg. Khim., 1974, 19, 1252.
Physical Methods
255
and 19Fn.m.r. spectra of difluorophosphoranes such as (37), which contain fourmembered rings, indicate that the pseudorotation processes are between t .b.p. structure^.^^ The lH, I3C,and l91F n.m.r. spectra of the metliyltrifluorophosphoranes (38) also indicated that the molecules have t.b.p. structures, but in this case there was
no evidence for pseudorotation below 100 0C.60 Steric effects had an important influence on the pseudorotational barriers of the oxyphosphoranes (29; Y = Me, Ph, or OR), and substitution of the N-phenyl group by N-mesityl increased AG* by 7 to 11 kJ rn01-l.~~The stereoisomerism and pseudorotation of some spirophosphoranes (39) have also been studied.6f Non-equivalence, Inversion, and Medium Effects.-The n.m.r. spectra of the phosphonates (40; Y = CHRCOX) have been investigated in isotropic and anisotropic solvents, and diastereoisomeric anisochronism has been detected.62Low barriers to inversion were found for the diphospholan (41) and diphosphorinans (42) when the bridging group E was changed from carbon to germanium, silicon, or tin.63Dipolar couplings were obtained from the n.m.r. spectra of sodium methylphosphonate (43)
dissolved in a lyotropic liquid crystal; the molecular orientation and bond lengths were estimated.64Similar studies have been carried out on phosphorus oxytriSpin-Spin Coupling.-The relative roles of different coupling mechanisms in organophosphorus compounds have been studied theoretically.6 6 The spin-spin interaction constants for methylphosphine have been calculated by the MO-LCAO method.67Unresolved isotropic coupling to boron caused broadening of the vinyl 59
6o 61 62 63 64
65 66
67
N. J. De’Ath, D. B. Denney, D. Z. Denney, and Y. F. Hsu, J. Amer. Chem. Soc., 1976,98,768 K. I. The and R. G. Cavell, J.C.S. Chem. Cornm., 1975, 716. B. A. Arbuzov, Yu. Yu. Samitov, Yu. M. Mareev, and V. S. Vinogradova, Doklady Akad. Nauk. S.S.S.R., 1972, 205, 1370. M. I. Kabachnik, E. I. Fedin, L. L. Morozov, A. E. Shipov, M. S. Vaisberg, P. V. Petrovskii, and T. A. Mastryukova, Bull. Acad. Sci. U.S.S.R., 1975, 24, 1418. A. Hauser, A. Zschunke, K. Issleib, and W. Bottcher, Phosphorus, 1975, 5, 261. R. C. Long, jun. and J. H. Goldstein, MoZ. Phys., 1975, 30, 681. P. K. Bhattacharyya and B. P. Dailey, MoZ. Phys., 1974, 28, 209. R. Kh. Safiullin, Yu. Yu. Samitov, and R. M. Aminova, Sbornik Aspirantsk. Rabot., Kazan. Un-T. Tochn Nauki Fiz., 1974, 175 (Chern. Abs., 1976, 84, 3962). R. Kh. Safiullin, R. M. Aminova, and Yu. Yu. Samitov, Zhur. strukf. Khinz., 1974, 15, 907.
Organophosphorus Chemistry
256
proton resonances of the trivinylborane-trimethylphosphine adduct rather than quadrupole relaxation effects.6 8 The PH dipolar splitting of solid potassium dihydrogen phosphate has been resolved by a multiple-pulse m e t h ~ d .The ~ sterochemistry of the cyclicphosphite (34) and analogous compoundshas been investigated,using the Overhauser effect,55and 13C hydrogen-satellite spectra were used to determine the structure of the vinylphosphine (44).70
JPPand JPM.Replacement of methyl by t-butyl in tetra-alkyldiphosphines (45) leads to very large negative increments in ~JPP, i.e. from - 179.7 Hz for (45; R = Me) to
-45 1 Hz for (45 ;R = But), which is due to rehybridization rather than a change in conformational populations.71 The changes are rationalized by increases in the bond angles, which reduce the s-character in the hybrid orbitals used to form the n-bond between the two phosphorus atoms. The catenated phosphorus dianions such as the disodium and dipotassium tetraphenylphosphines (46) give spectra with positive and temperature-dependent P-P coupling constants in accordance with the cyclic structures shown.72The direct P1I1-PIV coupling constant for the phosphinophosphinimines (47) was found to increase with decreasing basicity of the N Y As with the diphosphines above, t-butyl groups also greatly increase the magnitude of ~JPP in the disulphides (48).22c* 74 The mixed chalcogenides (49a; R = C,Hll) and (49a; R = But) had lJpp values of 175 and 149.5 Hz re~pectively.~~ The spectra of 0
R
I
R,,P-P=NY
I
R (47)
s s
II II &P -PK, (48)
s o
II II
R,P -P(OMe), (494
(49b)
0
phosphinomethylphosphine sulphides have been studied 76 and 3 J for ~ the ~ ethylene derivatives (49b) has been estimated from linewidths.7 7 Further examples of larger one-bond coupling to equatorial atoms compared to axially orientated atoms have 68 69 '0
71 72
73
74 75 76
77
L. W. Hall, J. D. Odom, and P. D. Ellis, J . Organometallic Chem., 1975, 97, 145. U. Burghoff, H. Rosenberger, R. Zeiss, R. Mueller, and L. N. Rashkovich, Phys. Status Solidi (A), 1974,26, K171. M. L. Sheer, Org. Magn. Resonance, 1974, 6, 85. H. C. E. McFarlane and W. McFarlane, J.C.S. Chem. Comm., 1975, 582. P. R. Hoffman and K. G. Caulton, J. Amer. Chem. SOC.,1975,97, 6370. H. Rossknecht, W. P. Lehmann, and A. Schmidpeter, Phosphorus, 1975,5, 195. Note that ~ J Pof P (40; R = Me) is misquoted on p. 261 of ref. 2212; the correct value is 18.7 Hz. K. M. Abraham and J. R. Van Wazer, Phosphorus, 1975,6, 23. J. D. Mitchell, Dim. Abs. Internat. (B), 1975, 36, 2212. Yu. Yu. Samitov, E. A. Berdnikov, F. R. Tantasheva, B. Ya. Margulis, and E. G. Katatv, J. Gen. Chem. (U.S.S.R.), 1975,45, 2097.
Physical Methods
257
appeared,lJpsebeing 909 Hz for (50), but 883 Hz for the alternative stereoisomer with an axial selenium atom.78 JPC. The selenide (50) and the cyclic phosphonate (51) show larger ~ J P values C to the 79 equatorial carbon atoms than to the axial carbon atoms in the other thus the coupling is 145.0 Hz for (51) but only 132.8 Hz when the methyl group is
axial. It is deduced from the P-C coupling constants from the low-temperature spectra of tetra-alkyldiphosphines (45) that NPC(i.e. ~ J P+ C*JPc)is large when the P--C bond is trans to the phosphorus lone-pair of electrons, as shown in (52), and small when the P--C bond is gauche to the lone pair of electrons, as shown in (53).80 For the diphosphine (45; R = But) it is deduced that NPCis 45.5 Hz for the bond in the tramorientation and 1 Hz for the bond in the gauche-orientation. It is interesting to note that the geminal PCC coupling constant of dichloro-t-butylphosphine (54), measured at - 140 "C, is at a minimum (0 Hz) when the C-C bond is trans to the phosphorus lone-pair of electrons and at a maximum (31.5 Hz) when the C-C bond is gauche to the lone-pair of electrons.81The appearance of averaged coupling constants for isopropyldichlorophosphine (55; R = Me, JPC= 17.5 Hz) and
ethyldichlorophosphine (55; R = H, a J p ~= 13.6 Hz) indicates that the conformers with a methyl group trans to the lone-pair of electrons predominate in a rapidly interconverting conformational equilibrium. The signs and magnitudes of the one-, two-, and three-bond P-C couplings for a series of acetylenic phosphines (56) and some PIV derivatives (57) have been described.82In contrast to the PIV derivatives, orbital coupling and/or spin dipolar mechanisms are probably dominant for the phosphines, due to the negligible s-character in the P - C bonds. The vicinal POCC coupling constants for the phosphite (58; Y = SMe)85and the amino-compound (58; Y = N H B u ~ )in , ~the ~ cis configurations shown, are over double those when the group Y is axial. The similarity of the PC coupling constants (50-65 Hz) of certain methylphosphonium halides and the reagents produced by the action of organolithium 78
79 80
81 88
8s
W. J. Stec, K. Lesiak, D. Mielczarek, and B. Stec, Z . Naturforsch., 1975,30b, 710. K. Lesiak, B. Uznanski, and W. J. Stec, Phosphorus, 1975,6, 65. R. K. Harris, E. M. McVicker, and M. Fild, J.C.S. Chem. Comm., 1975, 886. J. P. Dutasta and J. B. Robert, J.C.S. Chem. Comm., 1975, 747. R. M. Lequan, M. J. Pouet, and M. P. Simonnin, Org. Magn. Resonance, 1975,7, 392. A. Okruszek and W. J. Stec, 2.Naturforsch., 1975,30b, 430.
258
OrganophosphorusChemistry
compounds is attributed to the formation of lithium adducts (7) rather than ylides (8). Methylene ylides prepared by other methods give ~ J P values C in the region of 90-100 H z . ~ The ' P-C couplings through 1-5 bonds of model phosphonates such as (59) and (27) show that the vicinal coupling constants are at a maximum when the bonds are orientated at 180"and severely attenuated by OH substitution, especially when the hydroxy-group is trans-coplanar to the C-terminus of the coupling path. When a cyclopropyl group is part of the CCCP pathway, the coupling constants are much less than those predicted on the basis of dihedral angle. A highly asymmetric dihedral dependence of the vicinal couplings has been suggested. Some long-range C-P couplings through saturated bonds have been found which do not follow a W path.47 JPC,H.The geminal PCH coupling constants of the phosphinoacetonitriles (60) decrease with an increase of the bulk of the alkyl groups; thus 2 J is 5.1 ~ Hz~ for ~ (60; R = Et) and 2.1 Hz for (60; R = But).84The corresponding oxides have
larger coupling constants, 14.2 and 12.6 Hz respectively, the trend in magnitude being the same as in the phosphines. MO-LCAO calculations on the oxides (61) indicate that JPCH is dependent on the orientation of the HCPO bonds. The calculated values varied from 10 to 16 Hz for (61 ;Y = Me) and a remarkable 3 to 31 Hz for (61; Y = Cl).85The CNDO-CP method gave coupling constants closer to a normal Karplus relationship than those deduced experimentally from rigid molecules, whereas the reverse applied when the Pople-Sanky approximation was used. The n.m.r. parameters of thiocarbonyl-stabilized ylides (62; JPCH25-30 H z ) , ~ ~ acrylylphosphonates (63 ; JPCH 14.8-17.5 H z ) , ~propenylphosphonates ~ (64; JPCH
84
85 86
87
0. Dahl and F. K. Jensen, Acta Chem. Scand. ( B ) , 1975,29, 863. Yu. Yu. Samitov, R. Kh. Safiullin, R. M. Aminova, N. D. Chuvylkin, and G . M. Zhidomirov, Phosphorus, 1975, 5, 151. H. Yoshida, H. Matsuura, and T. Ogata, Bull. Chem. Soc. Japan, 1975,48, 2907. F. H. Meppelder and H. C. Beck, Rec. Trav. chim., 1975, 94, 149.
Physical Methods
259
~ ~the cycliccompound (65;JPCH 12 Hz) have been reported. Four-bond 17 H Z ) ,and couplings of 1 and 3 Hz are reported for the propenylphosphonates (64).88 JPNH. The magnitude of geminal PNH coupling constants can vary extensively: e.g. 6 Hz for the phosphonamide (66)yg09-12 Hz for secondary amides and phosphoroamidates, and 29-33 Hz for the phosphorylhydrazides (67).91
JPXGH.The POCH coupling constants of a variety of phosphites and thiophosphatesg2 and cyclic phosphatesg3have been reported. The use of these coupling constants for conformational analysiscontinues,and reports on derivatives of oxazaphospholan (68),04 dioxaphosphorinans (69),06 1,4,2-oxazaphosphorinans (70),06 and the first representatives of dithia- and diaza-phosphorinans (71;X = S or NH) have been published. Long-range PCNCH coupling constants of 1.46 and 1.80Hz have been recorded for (70;Y = OPri; R = Ph).O6
R
I
‘P’
Y
I
NO*
Y
1
H
Nuclear Quadrupole Resonance Studies.-The 3sCl atoms of the chlorotriphenylphosphonium ion (72)have been assigned to the n.q.r. resonance at 31.15 MHz.07At 77 K the trichlorophosphinimines(73)give multiplets which reflect non-equivalence The 36Clfrequency arising from a small barrier to rotation about the P-N of the acid chlorides (74) and (75) rises about 1 MHz as the atomic weight of the L. Maier, Phosphorus, 1975, 5, 223. T. A. Mastryukova, Kh. A. Suerbaev, P. V. Petrovzkii, E. I. Fedin, and M. I. Kabachnik, J. Gen. Chem. (U.S.S.R.), 1974, 44, 2359. 90 M. J. P. Harger, J.C.S. Perkin I, 1974, 2604. 9 1 R. J. Cremlyn, J. David, and N. Kishore, Phosphorus, 1975, 5, 203. 92 R. Burgada, L. Lafaille, and F. Mathis, Bull. SUC.chim. France, 1974, 341. 93 F. Ramirez, S. L. Glaser, P. Stern, I. Ugi, and P. Lemmen, Tetrahedron, 1973, 29, 3741. 94 J. Devillers, M. Cornus, and J. Navech, Org. Magn. Resonance, 1974, 6 , 211. 95 B. A. Arbuzov, R. P. Arshinova, T. A. Guseva, T. A. Zyablikova, L. M. Kozlov, and I. M. Shermergorn, J. Gen. Chem. (U.S.S.R.), 1975, 45, 1403. 96 Yu. Yu. Samitov, M. A. Pudovik, L. K. Kibardina, and A. N. Pudovik, J. Gen. Chem.
88 89
(U.S.S.R.),1975, 45, 2102. 97
98
E. E. Nifant’ev, A. A. Borisenko, A. I. Zavalishina, and S. F. Sorokina, Doklady Akad. Nauk S.S.S.R., 1974, 219, 881 ; K. B. Dillon, R. J. Lynch, R. N. Reeve, and T. C. Waddington, J. Znorg. Nuclear Chem., 1974, 36, 815. I. A. Kyuntsel, V. A. Mokeeva, G. B. Soifer, E. S. Koslov, and M. I. Povolotskii, J. Gen. Chem.
(U.S.S.R.),1975,45, 1954.
260
Organophosphorus Chemistry CN I
chalcogenide atom increases through oxygen and sulphur to selenium and also upon changing the structure from the monochlorides (74) to the dichlorides (75).@OThe effect of changing the nature of the group Y is basically inductive. A frequencytemperature equation has been developed for the n.q.r. spectra of the phosphadiazines (76) at 77-390 K.lo0
2 Electron Spin Resonance Spectroscopy The e.s.r. spectra of phosphorus compounds have been reviewed.lo1 The phosphorus hyperfine splitting ( a p 33.5 G )of the radical anion (77) is within the 25-36 G range of phosphorin radical anions.lo2 The cis- and trans-isomers of 1,Zbisdiphenylphosphinoethylene gave the same radical anion (78). The unpaired electron is coupled to all the protons in the molecule as well as to the two phosphorus atoms, and shows that the electron is completely delocalized. Only when caesium was used as the gegenion in THF could a metal interaction be detected. The spectrum in this case corresponded to the association of two caesium ions with the radical anion, the third
metal ion being separated.lo3The isotropic 31Phyperfine splittings of &substituted alkyl radicals (79) are in the order expected for hyperconjugative spin transmission for both PII1 and PIv compounds. The magnitude and temperature dependence of ~ Z H Sindicate that the conformation shown in (80) is the most stable.lo4The geometry of the alkylphosphine radical cations (81) is related to the electronegativity of the alkyl groups as in other trigonal radicals. Both the 31Phyperfine coupling constants and the ratios of the calculatedp- and s-spin densities correlated with SP of the respective neutral The triphenylphosphinium radical cation (81 ; R = Ph), generated by the X-irradiation of triphenylphosphine-trihalogenoborane 99
I. A. Nuretdinov, D. Ya. Osokin, and I. A. Safin, Bull. Acad. Sci. U.S.S.R.,1975,24, 263.
looE. A. Romanenko, Teor. ieksp. Khim., 1975,11, 705. 101 ‘Topics in Phosphorus Chemistry’, ed. E. J. Griffith and M. Grayson, Wiley, New York, 1975. 102 C. Jongsma, H. Vermeer, F. Bickelhaupt, W. Schafer, and A. Schweig, Tetrahedron, 1975,31,
293 1. 103
A. G. Evans, J. C. Evans, and D. Sheppard, J.C.S. Perkin 11, 1975, 643.
104
I. G. Neil and B. P. Roberts, J. Organometallic Chem., 1975, 102, C17. M. Iwaizumi, T. Kishi, and T. Isobe, J.C.S. Faraday 11, 1976, 72, 113.
105
PhyJical Methods
261
u R
K,P’
F
I4 0
adducts, has the odd electron mainly localized on the phosphorus atom.1°6 The mechanism of the reaction of t-butoxy radicals with dialkyl phosphites was studied by e.s.r. ~ p e c t r o ~ c o pThe y . ~ cc-proton ~~ hyperfine splittings (absent from deuteriated compounds) of the alkylphosphine dimeric radicals (82) indicated completely restricted rotation of the alkyl groups. The very large (58 G ) P-H isotropic constant observed in the spectrum of (83) has been attributed to the interaction of the unpaired electron with the antibonding a*-orbital of the P-P bond.lo8 The high temperature dependence of the 31Pcoupling constants of iminophosphorane radicals (84)is probably due to restricted rotation about the P-N bond; the splitting is described by a supposition of 226 and hyperconjugative interactions with the free According to the e.s.r. spectra of the radicals (85) and (86), the phosphorus ligands are non-equivalent ;calculations suggest that this is due to a distorted t.b.p. structure with the unpaired electron in a radial orientation. UHF and CND0/2 calculations indicate that the barriers to pseudorotation are very much higher for phosphoranyl radicals than for phosphoranes, e.g. 25.2 kcal mol-l for (87), 26.3 kcal mol-1 for (88), cf. 3.6 kcal mol-1 estimated for phosphorus pentafluoride. The high barriers appear to arise from a high p-character of the radial bonds, which leads to increased rigidity of these bonds. The calculations indicate that for electronegative ligands the orbital of the odd electron has a large contribution from the phosphorus s and p z electrons, but that for ligands of low electronegativity the s spin density decreases and the px density increases.11o The e.s.r. spectra of y-irradiated diethyl phosphate and its salts have been studiedlll and the structuresof the phosphonates(89) 112 and somenucleoside phosphates113have been studied from the e.s.r. spectra of the nitroxide spin-labelled compounds. An e.s.r. study of electron transfer in dinucleoside phosphate anions indicates preferenlo6 T.
Berclaz and M. Geoffroy, Mol. Phys., 1975, 30, 549. G. Brunton and K. U. Ingold, Org. Magn. Resonance, 1975, 7 , 527. lo8 M. Iwaizumi, T.Kishi, F. Watari, and T. Isobe, Bull. Chem. SOC.Japan, 1975, 48, 3483. log K. Scheffler, S. Hieke, R. Haller, and H. B. Stegmann, Z . Naturforsch., 1975, 30a, 1175. Yu. I. Gorlov and V. V. Penkovsky, Chem. Phys. Letters, 1975, 35,25; V. V. Penkovsky and Yu. I. Gorlov, V. Sb., Kuant. Khimiya, 1975,191 (Ref. Zhur., Khim., 1975, Abstr. No. 23B73). ll1 F. S. Ezra, Nuclear Sci. Abs., 1974, 29, 20688. 112 A. V. Il’yasov, Ya. A. Levin, A. Sh. Mukhtarov, and M. S. Skorobogatova, Teor. i eksp. Khim., 1975, 11, 612. 113 A. I. Petrov and B. I. Sukhorukov, Biofizika, 1975, 20, 965.
lo’
10
262
Organophosphorus Chemistry
tial protonation of thiamine in the DMP anions.114y-Radiolysis of deoxythymidine monophosphate gave very complex spectra, requiring computer-assisted ana1~sis.l~~ Phosphate deposits in liver mitochondria have been analysed with the aid of e.s.r.ll* and the spectra of some dihalogenophosphinidine radicals have been ana1y~ed.l~’ 3 Vibrational Spectroscopy Band Assignment and Structural Elucidation.-The infrared and Raman spectra of dimethylphosphine and its deuterium analogue (90) were determined in all phases. The PH stretching and bending regions gave some evidence of weak hydrogen bonding, and torsional modes gave barriers of 2.14 and 2.30 kcal mol-1 for the hydrogen and deuterium compounds respectively.l18 The PN stretching frequency around 900 cm-l for the phosphoramidates (91 ;Y = H, C1, or Me) was identified by 15N isotopic substitution; it was found that the F=O and P-N bond orders varied in a manner similar to the corresponding bonds in carboxamides, which was interpreted in terms of substantial p,-d, bonding.llg The i.r. spectra of carbamoyltriphenylphosphoranes (92; R = H, D, or Me) show bands at 1183i-4 cm-1 which are
assigned to YPN. The carbonyl group has an insulating effect, for the band position varies far less than it does in the phosphinimines (93; R = H, Me, or Ph).120 The i.r. band intensities of the phosphonium cobaltates (94; X = CoHal,) are five times greater than those of the corresponding phosphonium halides.121The structures of 1,3-thiaphosphetans(95) 122 and the cyclic phosphonic anhydride (96) 123 have been studied. The spectra of dichloromethylphosphonic acid (97), and its salts, in water
M. D. Sevilla, R. Failor, C. Clark, R. A. Holroyd, and M. Pettei, J. Phys. Chem., 1976,80,353. S . Gregoli, M. Olast, and A. Bertinchamps, Radiation Res., 1976, 65, 202. 116 K. Ostrowski, A. Dziedzic-Goclawska, A. Sliwowski, L. Wojtczak, J. Michalik, and W. Stachowicz, F.E.B.S. Letters, 1975, 60,410. 1 1 7 A. J. Colussi, J. R. Morton, K. F. Preston, and R. W. Fessenden, J. Chem. Phys., 1974, 61, 1247. 118 J. R. Durig and J. E. Saunders, J. Raman Spectroscopy, 1975, 4, 121. 119 Yu. P. Egorov, Yu. Ya. Borovikov, E. P. Kreshchenko, A. M. Pinchuk, and T. V. Kovalevskaya, J. Gen. Chem. (U.S.S.R.), 1975, 45, 1683. 120 W. Buder and A. Schmidt, Spectrochim. Acta (A), 1975,31, 1813. 1 2 1 M. A. A. Beg, Q. M. Samiuzzaman, and M. Jamal, Proc. Pakistan Acad. Sci., 1974, 11, 57. l Z 2R. R. Shagidullin and I. Kh. Shakirov, Spectroskopiya i Ee Primenenie V. Geojizike i Khimii, 1975, 231 (Chem. A h . , 1976, 84, 43129); I. Kh. Shakirov and R. R. Shagidullin, Doklady Akad. Nauk S.S.S.R., 1974, 219, 917. lZ3L. Maier, Phosphorus, 1975, 5, 253. 114
115
Physical Methods
263
and deuterium oxide have been assigned, and the force constants ~a1culated.l~~ It has been shown that laser Raman spectroscopy provides a far simpler method than tritium labelling for determining the rate constant of C-8-proton exchange in purine nucleotides. It also makes feasible the study of comparative rates of exchange in different nucleic acids to reveal differences in secondary Reduction of trimethyl phosphiteborane is believed to give a new type of diphosphorane (98), possessing YPP 437 cm-1.126 Stereochemical Aspects.-The i.r. and Raman spectra of ethylphosphine and its deuteriated analogue (99) indicate that the fluid phases contain gauche- and transconformers, but the solid phase contains the trans-conformer only. The methyl
II
YJ’ CH,CD,PH,
\
/I1
/C=YOLt
11
S
II
C1,POMe
rotational barrier is estimated to be 3.74 kcal m ~ l - ~The . ~ ~doublet ’ nature of YC=C in the spectra of vinyl-phosphonic and -phosphonous acids (100) has been attributed to rotational isomerism around the =C-0 bond.128The calculated band frequencies for the gauche- and trans-conformers of methyl ester (101) were close to the experimental ~ a 1 u e s .Conformational l~~ analysis of dialkyl and diary1 phosphites (1 02) by the combined i.r. and dipole-moment method has been reported. It was also deduced that P--He .O=P hydrogen bonding was absent.130 The ratio of tgg and ggg conformers of trialkyl selenophosphates (103) in hexane and acetonitrile solutions has been determined131and the dichloride (104) shown to exist mainly in the gaucheconformation when dissolved in non-polar media.132
124 125 126
127 128
129 130 131 132
B. J. Van der Veken and M. A. Herman, J. Mol. Structure, 1975,28, 371. J. Livramento and G. J. Thomas, jun., J . Amer. Chem. SOC.,1974,96, 6529. L. A. Peacock and R. A. Geanangel, Inorg. Chem., 1976,15, 244. J. R. Durig and A. W. Cox, jun., J. Chem. Phys., 1975, 63, 2303. A. V. Chernova, G . M. Dorozhkina, R. R. Shagidullin, V. V. Maskova, and G. F. Nazvanova, Bull. Acad. Sci. U.S.S.R., 1975, 24, 1871. R. R. Shagidullin, 0. A. Raevskii, and I. I. Vandyukova, Bull. Acad. Sci. U.S.S.R., 1975,24, 71. 0. A. Raevskii, Yu. A. Donskaya, F. G . Khalitov, E. L. Vorkunova, and Ya. A. Levin, Phosphorus, 1975, 5, 241.
R. R. Shagidullin, I. I. Vandyukova, I. A. Nuretdinov, and Kh. Kh. Davletshina, Doklady Akad. Nauk S.S.S.R., 1975,225, 886. R. R. Shagidullin, I. A. Vandyukova, and 0. A. Raevskii, Bull. Acad. Sci. U.S.S.R.,1975,24, 1414.
264
Organophosphorus Cheniistry
Studies of Bonding.-Hydrogen bonding of phenol or t-butyl alcohol to the phosphonates (105) has been studied. The hydrogen bond remained with the phosphonyl group when the group R contained nitrile or carboxylic ester groups. The AH values correlated with the Taft constants better than with d ~ and , this was attributed to d, bonding influencing BP where this was p0ssib1e.l~~ The YOH bands of a-hydroxy compounds such as the phosphonamide (106) have been analysed in terms of intermolecular hydrogen-bonded A ring-chain tautomeric equilibrium
between the Pv spirophosphoranes (107) and the PIII open-chain form (108) has been established and phosphorus-hydrogen bonding studied.1351.r. studies indicate that the stability of the iminophosphorane (109) over its methylenephosphorane tautomer (1 10) increases as the electron-withdrawing properties of the group R are Calculations on the tautomerism of the cyanoacetic ester derivatives (1 11) indicated that the inductive effect of the R groups had a dominating
plit RN-P-CII
013
,C02Et
I
RNH--P=C
/Co2E1
(K'O), I'C H
4 Microwave Spectroscopy The microwave spectra of ethylphosphine and its deuteriated analogues (1 12) and (113) show the presence of gauche- and trans-conformers in a ratio of 45 :55. Dipole moments, bond lengths, bond angles, and dihedral angles have been calculated for each conformer.138
5 Electronic Spectroscopy Absorption.-U.v, spectroscopy has been used to study the structure of the orange dianions (114). Plots of B against l/(rc 2) for each cation gave straight lines at 20 and
+
133 134 135 l36 137 13*
V. E.Bel'ski, R. F. Bakeeva, L. A. Kudryavtseva, A. M. Kurguzova, and €3. E. Ivanov, J. Geiz. Chem. (U.S.S.R.), 1975, 43, 2568. R. R. Shagidullin and E. P. Trutneva, Bull. Acad. Sci. U.S.S.R., 1975, 24, 1637. R. Mathis, M. Rarthelat, Y . Charbonnel, and J. Barrans, Compt. rend., 1975, 280, C , 809. 0.I. Kolodyazhnyi, J. Gen. Chem. (U.S.S.R.), 1975, 45, 539. M.Kirilov, G.Petrov, N. Tyutyulkov, and Y. Yotov, Munatsh., 1975, 106, 1533. J. R. Durig and A. W. Cox, jun., J, Chem. Pirys., 1976, 64, 1930.
265
Physical Methods
1 0 0 "C, showing that the anions and cations exist as contact ion pairs.1o3The possibility of p , d , conjugation in arylphosphines has been discussed in terms of overlap integrals and the energies of planar and pyramidal forms.139 Free-electron MO calculations have been applied to the absorption frequencies of unsymmetrical phosphocyanines derived from cyclopentadienylidenetriphenylphosphorane (1 1 5).140 Ar
A study of the influence of the Y substituents on the U.V. spectra of the phosphonium ylides (1 16) and the phosphinimines (1 17) indicated that the transmission factor of the group C,H4P=CH is less than half that of C6H4P=N,which itself is 10-20 times lower than C6H4.141Varying the nature of Z in the phosphinimine (118) had an irregular effect on the anionic chromophore, and a linear relationship between Ymax and Ed is not The effect of varying the nature of the phosphorus substituents Y in the vinyl compounds (100) has been described. It is interesting to note that although the PIv groups are probably the best electron-withdrawing groups to place opposite the donating ethoxy-group, the PII1dichloride (1 19) possesses the best chromophoric propert ies.12* Photoelectron.-n-Orbital energies appear to be unsuitable to discern the aromatic nature of phospholes (120) due to combined nn* and n, interactions. It is concluded that It,* conjugative and P-C,* hyperconjugative interactions stabilize the phosphole system relative to the interrupted cis-butadiene and phosphorus subunits, and that the p.e. spectrum can be interpreted in favour of an aromatic phosphole ring.143 Other workers have and reviewed 145 this aromaticity problem, and there has been a quantum-chemical study of the aromatic nature of phosphorus heteroc y c l e ~ The . ~ ~p.e. ~ spectrum of the ylide (121) contains peaks at 6.19, 8.32, and 139 140
141 142 143 144 145 146
E. N. Tsvetkov, J . Gen. Chem. (U.S.S.R.),1975,45,489. M.K.Rout and L. N. Patnaik, 2.phys. Chem. (Leipzig), 1975,256,785. R. I. Yurchenko, 0. M. Voitsekhovskaya, I. N. Zhmurova, and N. N. Lysova, J . Gen. Chem. (U.S.S.R.), 1975,45, 1700. I. N. Zhmurova and V. G . Yurchenko, J. Gen. Chem. (U.S.S.R.), 1975,45,1924. W.Schaefer, A. Schweig, and F. Mathey, J. Amer. Chem. Soc., 1975,98,407. G.V. Bakulina, Yu. S. Mardashev, and E. V. Borisov, Primenenie Konformatsion. Analiza V Sinteze Novykh Organ. Veshchestv., 1975,66 (Ref. Zhur. Khim., 1975,Abs. No. 20ZH45). A. N. Hughes and D. Kleemola, J. Heterocyclic Chem., 1976,13, 1. E. D. Lavrinenko-Ometsinskaya, V. V. Pen'kovskii, V. V. Strelko, T. L. Krasnova, E. F. Bugarenko, and E. A. Chernyshev, Koant. Khimiya, 1975 L-147 ( R e 5 Zhur., Khitn., 1975, Abs. No.22B60).
Organophosphorirs Chemistry
266
8.90 eV; the inductive effect of the carbanion shifts the nas band of benzene (which has its nodal plane passing through the substituent site) from 9.24 to 8.32 eV whilst the other two bands originate from the interaction of the ZC- carbanion orbital [which is at 6.81 eV for the methylene ylide (122)] with the nsorbital of benzene. The ns + nc- band, which would normally appear at a higher value than 9.24 eV, is also influenced by a strong inductive effect and appears at 8.90 eV. Similar effects occur for the corresponding iminophosphorane, but all three bands appear at higher eV va1~es.l~’ 6 Rotation The optical purity of the phosphonate (123)148and the absolute configuration of the phosphonium bromide (124) 149 have been established. Optical rotatory dispersion and circular dichroism have been used in stereochemical studies of phospholipids 150 and adeno~ine-5’-triphosphate.~~~ 0
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