5 Terva I en t Phosphor us Acids

BY B. J. WALKER

1 Introduction During the past ten years, new mechanistic information has made the allocation of certain types of reaction within the original headings in this Chapter incorrect or uncertain. In the present volume these allocations have been re-assessed; in deference to our seasoned readers, changes have been made only in the light of positive mechanistic information.

2 Phosphorous Acid and its Derivatives Nucleophilic Reactions.-Attack on Saturated Carbon. The usual reports of the Arbusov reaction have appeared, including intramolecular examples to give (l),l

0 II

RN-pOEt ClCH,CH,NRP(OEt), -+ fi

examples where competition between ring-opening and ring-retention is finely balanced (Scheme 1),2 and a general synthesis of N-substituted aminoalkyl-

OR' I

O/"O + R W H , X

Me Me Me Me X

Scheme 1

phosphonic acids (Scheme 2).3 The Arbusov reaction, initiated by methyl iodide, has been used to polymerize 2,2-dimethyltrimethylenephenylphosphinate (2). *

1 E. S . Gubnitskaya, Z. T. Semashko, and A. V. Kirsanov, Zh. Obshch. Khim., 1978, 48, 2624 (Chem. Abs., 1979,90, 104 070).

2 L. N. Krutskii, L. V. Krutskaya, N. M. Rozina, M. A. Subbotina, N. A. Veretel'nikova, T. V. Zykova, R. A. Salakhutdinov, and V. S . Tsivunin, Zh. Obshch. Khim., 1978,48,2206 (Chem, A h . , 1979, 90, 72 280).

3 D. Brigot, N. Collignon, and P. Savignac, Tetrahedron, 1979, 35, 1345. 4 G. Singh, J . Org. Chem., 1979, 44, 1060.

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84 Organophosphorus Chemistry

0 0 0

(E t O),PNHCHR' (CH) B r 6 (E t O),PNHCH R' (CH) P(0 R), I I ll I1

1-i"

0

'OH Reagents: i, (R0)3P; ii, BuLi; iii, R2X; iv, H30'.

Scheme 2

The reaction of heteroaromatic cations with trialkyl phosphite in the presence of sodium iodide has been used to prepare (1,3-dithiolyl)phosphonate (3),5 (2-acyl-l,2-dihydroquinoline)phosphonates (4),6 and the anthracene analogues (9.'

'0

( 5 ) X = 0, S, or NR

Preferential alkylation at phosphorus allows the preparation of alkylphenyl- phosphinic acids from the dianion (6), which is conveniently obtained from the commercially available phenylphosphonous acid (see Scheme 3).

0 I1

PhPOH A H

0

* PhPOH I

Reagents: i, 2BuLi, THF, at 0 "C; ii, RCHzX; iii, H a .

Scheme 3

5 K. Akiba, K. Ishikawa, and N. Inamoto, Bull. Chem. SOC. Jpn., 1978, 51, 2674. 6 K. Akiba, Y. Negishi, and N. Inamoto, Synthesis, 1979, 55. 7 K. Ishikawa, K. Akiba, and N. Inamoto, Bull. Chem. SOC. Jpn., 1978, 51, 2684. 8 M. E. Garst, Synth. Commun., 1979, 9, 261.

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Tervalent Phosphorus Acids 85

Attack on Unsaturated Carbon. The addition reactions of tervalent phosphorus esters with unsaturated systems have been re~iewed.~ Further investigations lo

of the reaction of trialkyl phosphites with nitro-alkenes show that the products obtained depend on the conditions (Scheme 4), although in most cases the initial attack is at unsaturated carbon. In view of earlier reports,ll it is somewhat surprising to read that l-bromonitroalkenes and tertiary phosphites initially give the addition product (7), which then forms the phosphonate (8) with retention of the nitro-gL’oup.12

0 I t

(RO),PC=CH, + RON0 + RNO, Ph

/ ; I (MeO),PCPhCH=NOH ii ~ PhCH=CHNO,

I \ OMe iii

0 0 I1 II

(RO),PCHPhCH,NO, + (RO),PH + (RO),PC=CH, Ph

\ a Reagents : i, (R0)3P, 1 ,Zdimethoxyethane; ii, (MeO)sP, ButOH ; iii, (R0)3P, 1,2-dirnethoxy-

Scheme 4 ethane, HzO.

0 0 11

I --+ (MeO),P’ ‘NO --+ (MeO),PC=CHNO,

CHMe,

(8) Br

Me,CH H (7)

The addition of dialkyl bis(ethoxycarbony1)methyIphosphonites to afl- unsaturated esters gives alkoxyphosphonium ylides (9) rather than the Arbusov product,13 presumably because of the low nucleophilicity of the carbanion.

CH,CHRCO$e /

(EtO),PCH(CO,Et), + H,C=CRCO$e - (Et0)Q

\\C(CO&t),

(9) 9 A. N. Pudovik and I. V. Konovalova, Synthesis, 1979, 81. 10 W. E. Krueger, M. B. McLean, A. Rizwaniuk, J. R. Maloney, G. L. Behelfer, and B. E.

11 B. J. Walker, in ‘Organophosphorus Chemistry’, ed. S. Trippett (Specialist Periodical

12 R. D. Gareev, G. M. Loginova, I. N. Zykov, and A. N. Pudovik, Zh. Obshch. Khim., 1979,

l a D. M. Malenko and Yu. G. Gololobov, Zh. Obshch. Khim., 1979, 48, 2793 (Chern. Abs.,

Boland, J. Org. Chem., 1978, 43, 2877.

Reports), The Chemical Society, London, 1975, Vol. 6, p. 16.

49, 25 (Chem. Abs., 1979,90, 187 042).

1979, 90, 137 924).

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86 Organophosphorus Chemistry

The nickel(r~)-catalysed Arbusov reaction of diethyl methylphosphonite and 2-bromoacetanilide has been used to prepare (10) en route to the trico- ordinate iodinan (1 1) l P (Scheme 5). Vinyl halides co-ordinated to manganese undergo u.v.-initiated Arbusov reactions to give the vinylphosphonates (12). l6

0

(10)

Scheme 5

Reagents: i, MeP(OEt)z, NiClz; ii, several steps.

CN I

The normal Arbusov products (13) are amongst those isolated from the reaction of tertiary phosphites with 2-chlorovinyl ketones (Scheme 6).l6 Tris(diethy1-

1 4 T. M. Balthazor, J. A. Miles, and B. R. Stults, J. Org. Chem., 1978, 43, 4538. 16 M. G. Newton, N. S. Pantaleo, R. B. King, and S. P. Diefenbach, J. Chem. SOC., Chem.

16 F . Hamnnerschmidt and E. Zbiral, Justus Liebigs Ann. Chem., 1979, 492. Cummun., 1979, 55; R. B. King and S. P. Diefenbach, Inorg. Chern., 1979, 18, 63.

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Tervalent Phosphorus Acids 87

amino)phosphine reacts with the chloro-substituted quinones (16) to form salts (17). This is quite different to the behaviour of triphenylphosphine in a similar reaction. l7

x()cl X ' 'c1 (Et,N),P: :61FJ3 I I Cl'

0 0 (16) X = CN or C1 (17)

The interest in equivalents of acyl anions continues. The phosphoramidate (1 8) reacts under mild conditions with saturated and unsaturated aldehydes to give the phosphoramidates (19) and (20) respectively, which are excellent enolate-anion equivalents of (21) and (22). The analogous phosphonate (23)

OSiEt, I

(Et,SiO)P(NMe,), RCH==CHCHO

0 (18) \ R I1

R~=CHCOR II

RC' (21) (22)

can be converted into p-substituted carboxylates via alkylation (which is redo- selectively y-) and alcoholysis lB (see Scheme 7). The phospholan oxide analogue

0 H 11 R' RTH OSiMe, R' RTHCHaCOaR3

+ R' ,c/cyP(oEtL a . .. \ / iii, /c=c\ 0

I I //P(OEt), (EtO),PH

OSiEt, H (23) 0

Reagents: i, lithium di-isopropylamide; ii, R2X; iii, R30H, HsO+. Scheme 7

1 7 D. B. Denney and A. D. Pendse, Phosphorus Surfu., 1978, 5, 249. 18 D. A. Evans, J. M. Takacs, and K. M. Hurst, J . Am. Chem. SOC., 1979,101,371. 19 T. Mata, M. Nakajima, and M. Sekine, Tetrahedron Lett., 1979, 2047.

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88 Organophosphorus Chemistry

(25) of a pentofuranose has been prepared from the secondary phosphinite (24) by intramolecular addition to the aldehyde group.2o

2,5-Diphenylfuran is formed on treatment of trans-1 ,2-dibenzoylethylene with trimethyl phosphite,21 and attempts to use this reaction as a general method of furan synthesis have been reported. 22 Aryl-substituted 2-butene-l,4-diones (26) form furans in moderate yield, but no reaction was observed with o-phthal- aldehyde or naphthalene-2,3-dialdehyde. However, if dienophiles were added to the reaction mixture in these latter cases, adducts, e.g. (27), were formed.

The only example of the Perkow reaction worth reporting in the present volume is the formation of the insecticidal enolphosphate (28), which has been shown by an X-ray analysis to have the (2) configuration.23

ao M. Yamashita, M. Yoshikane, T. Ogata, and S. Inokawa, Terrahedrun, 1979, 35, 741. 21 0. P. Madan and C. P. Smith, J. Org. Chem., 1965, 30, 2284. z2 M. J. Haddadin, B. J. Agha, and R. F. Tabri, J . Org. Chem., 1979, 44, 494. 13 Z. Galdecki, M. L. Glowka, and A. Zwierzak, Phosphorus Sulfur, 1979, 5, 299.

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Tervalent Phosphorus Acids 89

A variety of cyclic products, e.g. (29) and (30), have been obtained from the reaction of alkylphosphorous acid isocyanates with imines 2 4 and with chloro- ketones.2s

Tetra-alkyl methylenediphosphonites give the expected products (3 1) and (32) on reaction with acyl chlorides.26 More interesting is the first reported isolation of an acyl-fluorophosphorane (33) from the reaction of ethyl diphenylphos- phinite with benzoyl flu~ride.~' The addition of secondary phosphine oxides to carboxylic acid anhydrides provides a general route to acylphosphine oxides (34).

0 0 II I I

R'RtPH + (R3CO),0 __f R'R2PCOR3

(34)

The nitrone (35) reacts with trialkyl phosphites under acidic, basic, or neutral conditions to give different products in each case. 29 Reasonable mechanistic speculation is offered, with phosphite attack on carbon as the common initial step (Scheme 8).

24 I. V. Konovalova, R. D. Gareev, L. A. Burnaeva, M. V. Cherkina, 0. A. Molchanova, and

25 I. V. Konovalova, N. R. Novikova, L. A. Burnaeva, T. M. Moshkina, and A. N. Pudovik,

26 Z. S . Novikova, A. A. Prishchcnko, and I. F. Lutsenko, Zh. Obshch. Khim., 1979,49, 470

37 S . Neumann, S . Schomburg, G . Richtarsky, and R. Schmutzler, J. Chem. Soc., Chem.

28 G. Frey, H. Lesiecki, E. Lindner, and G. Vordermaier, Chem. Ber., 1979,112, 763.

A. N. Pudovik, Zh. Obshch. Khim., 1978, 48, 1940 (Chem. Abs. 1979, 90, 23 176).

Zh. Obshch. Khim., 1979,49, 36 (Chem. Abs., 1979, 90, 187 043).

(Chem. Abs., 1979,90, 204 193).

Commun., 1978, 946.

P . Milliet and X. Lusinchi, Tetrahedron, 1979, 35, 43.

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Organophosphorus Chemistry

Reagents: i, (R0)3P, MeOH; ii, (R0)3P, AcOH; iii, (R0)3P, Et3N. Scheme 8

Attack on Nitrogen. Copper(1) complexes of phenyl phosphites, phosphonites, phosphinites, and phosphines react with 3-cyano-3-bromopyrrolidine-2,5- diones to give phosphoranes, e.g. (36; X=Br). Some differences in yield and products are observed in the absence of copper.3o

C1CuPhnP(OPh)3-, + pxy-(- /PPhn(OPh)3 --I7

R O R 0

(36)

A large number of pentaco-ordinate amino(oxy)- and diamino(oxy)- phosphoranes (38) have been prepared by the reaction of bifunctional azides (37) with tervalent phosphorus compounds. The same basic reaction has been

f Y,R3 (r + R'R2R3P + HN-P

R' (3 8)

(:"=pR1RaR3 I 'R'

(37)

30 R. Ketari and A. Foucaud, Tetrahedron Lett., 1978, 4515. 31 J. I. G. Cadogan, I. Gosney, E. Henry, T. Naisky, B. Nay, N. J. Stewart, and N. J. Tweddle,

J. Chem. SOC., Chem. Cornmiin., 1979, 189.

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Tervalent Phosphorus Acids 91

used in a more general synthesis of pentaco-ordinate phosphoranes from 2-phenyl-l,3,2-dioxaphospholan (39) through reaction with phenyl azide followed by the addition of a di01.~~ Closely related reactions of trialkyl phosphites with azidocarboxylic acids give dialkoxyphosphonyl-amino-acids (40),33 presumably due to the relative instability of acetoxypho~phoranes.~~

n n

P h ‘NPh

0 II

(MeO),P + N,CH,CO,H --+ (MeO),PNHCH,CO,Me

(40)

The reaction of N-(trimethylsi1oxy)phosphine imines with phosphites gives imines (41) containing both tervalent and quinquevalent phosphoru~.~~

R’,P=NOSiMe, + (R20)g -+ R18=NP(OR9,

(41)

Attack on Oxygen. In wet acetonitrile, the bicyclic phosphoramidate (42) forms ring-opened products. 36 Surprisingly, (43), which appears to be the intermediate in this reaction, can be observed by 31P n.m.r. Similar adducts (44) and (45) are formed on addition of methanol and phenol respectively.

0-q-0 4 ‘\

H OR

(44; R = Me) (45; R = Ph)

32 J. I. G. Cadogan, N. J. Stewart, and N. J. Tweddle, J . Chem. Soc., Chem. Comnzun., 1979, 191.

33 N. I. Gusar, M. P. Chaus, and Yu. G. Gololobov, Zh. Obshch. Khim., 1979,49,21 (Chem. Abs., 1979, 90, 187 041).

34 B, J. Walker, in ‘Organophosphorus Chemistry’, ed. D. W. Hutchinson and S. Trippett (Specialist Periodical Reports), The Chemical Society, London, 1979, Vol. 10, p. 105.

35 E. P. Flindt, Z. Anorg. Allg. Chem., 1978, 447, 97. 86 D. Houalla. M. Sanchez. R. Wolf. and F. H. Osman. TetruhPdron rpt t 19711 4675

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92 Organophosphorus Chemistry

A variety of stable oxyphosphoranes (46) and (47) have been prepared from fluorophosphites and hexafluoroacetone and hexafluorobiacetyl, for n.m.r.

Thiophosphoranes (49) are less stable, but they can be prepared by the reaction of phosphites with the dithiet (48).38 The first synthesis of a selenophos- phorane (50) is reported, from the reaction of 2-methoxy-l,3,2-dioxaphospholan with 5,5-bis(trifluoromethy1)-A3-1 ,2,4-diselenazoline. 39

F F

The conversion of aliphatic nitro-compounds into nitriles in high yield is conveniently accomplished by reaction with hexamethylphosphortriamide. 40

Phosphite coupling continues to be used in the synthesis of thiafulvalenes. Deoxygenation of thiapendione (51) with phosphite gives the dimer (52),41 while, as might be expected, a variety of products can be isolated from the

87 H. B. Eikmeier, K. C. Hodges, 0. Stelzer, and R. Schmutzler, Chem. Ber., 1978, 111, 2077. 88 B. C. Burros, N. J. De'ath, D. B. Denney, D. Z. Denney, and I. J. Kipni, J. Am. Chem. SOC.,

1978,100,7300. se K. Burger, R. Ottlinger, A. Frank, and U. Schubert, Angew. Chem., Int. Ed. Engl., 1978,

17,774. 4o G. A. Olah, Y. D. Vankar, and B. G. B. Gupta, Synthesis, 1979, 36.

N. M. Rivera, E. M. Engler, and R. R. Schumaker, J. Chem. SOC., Chem. Commun., 1979, 184

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Tervalent Phosphorus Acids 93 reaction of a mixture of (51) and (53) with trimethyl ph~sphite.~* Amongst these products is the unsymmetrical adduct (54).

Tris(trimethylsily1) phosphite is a highly effective deoxygenating agent for sulphoxides and nitro-comp~unds.~~ It has the advantages over other phosphites of not rearranging to phosphonate before reaction and that its oxidation product is readily hydrolysed to phosphoric acid, which can be easily separated from the products. The deoxygenation of DMSO is especially facile, and this fact has been used as the basis for a method of nucleoside-phosphonate to -phosphate con- version (Scheme 9). Similarly, dimethyl selenoxide is reported to be an effective,

0

1 Jii, iii

II

(Me,SiO),P-0 ll

nucleoside Hp-ol I nucleoside -0

0

HOP-0 1 I nucleoside -0 Reagents: i, MeC(O)NSiMea, DMSO; ii, DMSO; iii, HzO.

Scheme 9

mild reagent for the oxidation of tervalent phosphorus Of more interest is the inversion (> 80%) of configuration observed on oxidation of acyclic compounds and the retention (> 90%) in the case of 2-methoxy-4- methyl-l,3,2-dioxaphosphorinan (55) . In both cases the reaction is thought to proceed by initial attack of phosphorus on selenium; however, the explanations for the differences in stereochemistry are not acceptable without further ex- periment a1 support.

OMe

Me

42 E. M. EngIer, V. V. Patel, and R. R. Schumaker, J. Chem. SOC., Chem. Cornmun., 1979,516. 45 M. Sekine, H. Yamagata, and T. Hata, Tetrahedron Lett., 1979, 375. 44 M. Mikolajczyk and J. Luczak, J. Org. Chem., 1978, 43, 2132.

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94 Organophosphorus Chemistry

Both polymeric [e.g. (56)] and crystalline [e.g. (57)] aminophosphines have been synthesized and used as desulphurization in this role they have a number of advantages, including the ease of separation of products, over the previously used liquid aminophosphines. The polymers (56) occlude large

( 5 6 ) (57)

amounts of solvent during their formation, and the removal of this reduces their efficiency in the desulphurization reaction. Evidence for the mechanism shown in Scheme 10 is provided by the inversion at the chiral carbon centre.

0

0

0 .H'

C*H,,

N R , k 3 - - C 9 ' Me

\

I '0

0 +

R,P=S

Scheme 10

The reaction of tervalent phosphorus compounds with p-quinones has been shown to take place via a free-radical mechanism.46 Attack on Halogen. The reactions of alkyl di-t-butylphosphinites (58) with a wide variety of alkyl halides have been in~estigated.~' As expected, Arbusov and Perkow products are formed, depending on the nature of the halide used. However, the sterically hindered nature of (58) leads to an increase in pathways involving attack on halogen, and to behaviour closer to that expected of phosphites.

ReIatively stable phosphonium salts (59) have been observed in the Arbusov reaction of phosphites and phosphonites with chlorine and sulphur d ich l~r ide .~~

45 D. N. Harpp, J. Adams, J. G . Gleason, D. Mullins, and K. Steliou, Tefrahedron Letr.,

46 G. Bockstein and H. M. Buck, Phosphorus Sulfur, 1978, 5, 61. 47 0. Dahl, J. Chem. SOC., Perkin Trans. I , 1978, 947. 48 J. Michalski, J. Mikolajczak, and A. Skowronska, J. Am. Chem. SOC., 1978, 100, 5386.

1978, 3989.

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Tervalent Phosphorus Acids 95

B U',PO R

0

R'P(OR2), + C1X - [R1$X(OR2), C1-] + RIP

(5 8)

II,X

(59) X = C1 or SCl 'OR'

The range of spirophosphoranes (60) available from tervalent phosphorus compounds in the presence of N-chlorodi-isopropylamine has been extended by prolonged reaction times. 49 Hexamethylphosphortriamide and iodine provide

R,P + ") + ClNPri, --+ R,P, HY /? Y

(60; X,Y = S, 0, or NR)

a new reagent for the deoxygenation of sulphoxides and azoxy-arenes. 50 The reaction is catalysed by iodide, and the mechanism suggested is shown in Scheme 11.

0 0 -P(NMe,), R1SR2 /I + (Me,N),PI, _.f [giz 1 --+ R'R'S + I, + (Me,N),PO

I- Scheme ll

Electrophilic Reactions.-The study of two-co-ordinate pmbonded phosphorus continues to be an area of major interest. Tetrameric cyclophosphazanes (61) are in temperature- and solvent-dependent equilibrium with the monomeric form (62).51 The latter form can be stabilized by co-ordination of a Lewis acid,

probably as shown. 1H-1 ,2,3a2-diazaphospholes (63) have been detected in the reaction of acetone methylhydrazone with phosphorus trichloride and separated from the 2H-isomer (64), which previously was the only isomer is0lated.~1 Physical and chemical investigations of these compounds did not clearly answer the question concerning delocalization across a2-phosphorus.

49 S. Singh, M. Swindles, S. Trippett, and R. E. L. Waddling, J. Chem. SOC., Perkin Trans. I ,

50 G. A. Olah, B. G. B. Gupta, and S. C. Narang, J. Org. Chem., 1978, 43,4503. 51 C. Malavaud, M. T. Boisdon, Y. Charbonnel, and J. Barrans, Tetrahedrm Lett., 1979,447. 52 J. H. Weinmaier, J. Luber, A. Schmidpeter, and S. Pohl, Angew. Chem., Int. Ed. Engl.,

1978, 1438.

1979, 18, 412.

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96 Organophosphorus Chemistry

MeNHN=CMe, + PCI,

Some novel reactions of two-co-ordinate phosphorus have been reported. Addition of a carbene to (65) gives a bicyclic phosphiran which is converted into monocyclic products (66) on treatment with alcohols.63 The first example of a [2 + 21-cycloaddition of 02- and a4-phosphazenes is provided by the reaction of the imino-aminophosphine (68) with the dimethyl azaphosphole (67).64 The product is reported to undergo reversible dissociation to (67) and (68). Four-

(Me,%), P-N C0,Me + (Me,Si),NP=NSiMe, __)I

C0,Me (6 8)

membered phosphorus-nitrogen rings are also obtained from the reaction of trimethylsilylimino-bis(trimethylsilyl)aminophosphine (69) with the silazene equivalent (70).66 The novel three-membered cyclic adduct (71) is the product of the reaction of (69) with hexafluoroacetone, while a similar reaction with hexafluorobiacetyl gives the five-membered cyclic adduct (72).66 The dico-

68 B. A. Arbuzov, E. N. Dianova, and Yu. Yu. Samitov, Dokl. Akad. Nauk SSSR, 1979,244, 117 (Chem. Abs., 1979,90, 187 058). A. Schmidpeter and T. von Criegern, 2. Naturforsch., Teil B, 1978, 33, 1330 (Chem. Abs., 1979, 90, 55 024).

65 U. Klingebiel, Chern. Ber., 1978, 111, 2735. ti6 G. V. Roschenthaler, K. Sauerbrey, and R. Schmutzler, Chem. Ber., 1978, 111, 3105.

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Tervalent Phosphorus Acids 97

Me,Si-NAr Me,SiN=PN(SiMe,), + Me,Si-NAr - I I

I: Li Me,SiN-PN( SiMe,), (69) (70)

(71) (Me,Si),NP = NSiMe,

(69) NSiMe,

CF, (72)

ordinate nature of the phosphorus cation (73)67 has been confirmed by an X-ray structure.68 1,2,3-Tri-t-butylphosphiran oxide undergoes thermal de- composition to (2)-2,2,5,5-tetrarnethyl-3-hexene and t-butylphosphinidene oxide (74), as shown by trapping with various reactionss9 (see also Chapter 4).

(Pr',N),PCl N (Pr ',N),P' AICG (7 3)

0 \p,But

B ut ABut

> 60°C ~ "H" + [ButP-01 But But / (74) \

5 0%

0

Bu'POMe H

100%

II

57 M. G. Thomas, C. W. Schultz, and R, W. Parry, Inorg. Chem., 1977, 16, 994. 58 A. H. Cowley, M. C. Cushner, and J. S. Szobota, J. Am. Chem. SOC., 1978,100,7784. 59 H. Quast and M. Heuschmann, Angew. Chem., In?. Ed. Engl., 1978,17, 867.

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98 Organophosphorus Chemistry

In spite of its sterically hindered nature, it is amazing to read of the stability of P-mesityl(diphenylmethy1ene)phosphine (75)60 (see also Chapter 1).

R($- P- CPh,

Me (75) R = Me

7

Ph H H

(77)

The kinetics of dynamic PIII-PV systems (76) and (77) have been investigated using n.m.r. spectroscopy. 61 French workers have isolated the first PI11 tautomers of bicyclic phosphoranes (78) as co-ordination complexes, e.g. (79), of molybdenum, tungsten, and rhodium. O 2 The preference for five-co-ordination is maintained in the tetracyclic example (80) obtained from 1,4,7,1O-tetra-

(8Q)

‘ 0 T. C. Klebach, R. Lourens, and F. Bickelhaupt, J. Am. Chem. SOC., 1978,100,4886. 61 B. Garrigues, C. B. Cong, A. Munoz, and A. Klaebe, J . Chem. Res. (S), 1979, 172. 02 D. Bondoux, I. Tkatchenko, D. Houalla, R. Wolf, C. Pradat, J. Riess, and B. F. Mentzen,

J. Chem. SOC., Chem. Commun., 1978, 1022; C . Pradat, J. G. Riess, D. Bondoux, B. F. Mcntzen, T. Tkatchenko, and D. Houalla, J. Am. Chem. SOC., 1979, 101, 2234.

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Terualent Phosphorus Acids 99 azacyclodecane and hexamethylphosphortriamide;s3 however, an investigation of the effect of ring size in this type of reaction provides tetracyclic compounds (81) which do prefer the tervalent f01-m.~~ Obviously, only the tervalent form (82)

is available from the reaction of cyclic triamines with hexamethylphosphor- triamide, and, in agreement with predictions using models, although (82; Z=rn=2, n=3) could be obtained, (82; I = m = n = 2 ) could not?

Equilibrium constants and reaction rates have been determined for the reactions of alcohols and amines with 2-R-1,3,2-dioxaphosphorinans (83) and 2-R-1,3-dimethyl-l,3,2-diazaphosphorinans (84).s6 The equilibrium constants depend on the nucleophilicity of the exchanging groups and also on the steric

(83; X = OR' or NR2,, Y = 0) (84; X = OR' or NR',, Y = NR3)

93 J. E. Richman and T. J. Atkins, Tetrahedron Lett., 1978,4333. 64 T. J. Atkins and J. E. Richman, Tetrahedron Lett., 1978, 5149. 65 T. J. Atkins, Tetrahedron Lett., 1978, 4331. 66 J. A. Mosbo, Phosphorus Sulfur, 1978, 4, 273.

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lo0 0 rganop hosp hor us Chemistry

interaction between substituents at the 2-position and substituents at the 1- and 3-positions. An analogous exchange occurs in the reaction of 2-O-methyl- xylitan with hexaethylphosphortriamide to give isomeric 1,3,2-dioxaphos- phorinans (85).67 The report includes an investigation of the chemistry and conformation of (85).

+ P(NEt,), - MeO

( 8 5 ) M e 0

A wide range of tervalent phosphorus acid chlorides react with benzil mono- (o-hydroxyanil) (85) to give bicyclic phosphoranes (88).68 Evidence has been presented for a reaction pathway involving initial substitution to give (87).

HO' /

R,P-0

(87)

Cyclic Esters of Phosphorous Acid.-cis-2-Phenyl-5-t-butyl-l, 3,2-dithiaphos- phorinan has been shown by X-ray structural analysis to have the chair form (89).6B This and other results confirm that oxidation of (89) with peroxide takes place with retention of configuration at phosphorus.

Ph

More examples of ten-membered cyclic dimers formed from various 2- substituted-l,3,2-dioxaphospholans have been reported.'O Meso- and racemic structures were allocated on the basis of n.m.r. data and, in one case, i.e. trans- (90; R= Ph), by X-ray data. As with 1,3,2-dioxa- and 1,3,2-dithia- cyclic

67 E. E. Nifant'ev, L. T. Elepina, A. A. Borisenko, M. P. Koroteev, L. A. Aslanov, B. M.

68 A. Schmidpeter and J. H. Weinmaier, Chem. Ber., 1978, 111, 2086. 69 R. 0. Hutchins, B. E. Maryanoff, M. J. Castillo, K. D. Hargrave, and A. T. McPhail,

' 0 J. P. Dutasta, A. Grand, A. C. Guimaraes, and J. B. Robert, Tetruhedron, 1979, 35, 197.

Ionov, and S. S. Sotman, Phosphorus Sulfirr, 1979, 5, 315.

J. Am. Chem. SOC., 1979,101, 1600.

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Tervalent Phosphorus Acids 101

phosphorus compounds, but unlike 1,3,2-diaza examples, 1,3,2-0xazaphos- pholidines, e.g. (91), are in equilibrium in solution with the ten-membered-ring dimer (92) and polymeric species.71 As with earlier reports, the conclusions are based on n.m.r. data and the isolation of the disulphide of (92) on addition of sulphur.

(93) R = C1, OMe, Ph, Me, or NMe,

The stereochemistry of several P-substituted 1,3,6,2-trioxaphosphocans (93) has been investigated by n.m.r. spectros~opy.~~ Miscellaneous Reactions-Quite unexpectedly, o-hydroxybenzyl alcohols react with phosphites, phosphonites, and phosphinites to give the corresponding benzylphosphorous acid (94).73 No explanation has been offered, but one suspects that a simple exchange reaction followed by an Arbusov rearrangement occurs, rather than the involvement of quinquevalent intermediates.

CH,OH I

0 II

CHzPRlR' 1

+ MeOPR'R' .f MeOH

(94) R', R2 = OMe or alkyl

Optically active 4-acyloxy-azetidin-2-ones have been prepared from peni- cillins by opening the thiazolidine ring by treatment with trimethyl phosphite and a carboxylic acid (Scheme 12).74 Presumably the phosphite somehow assists

71 J. B. Robert and H. Weichmann, J. Org. Chem., 1978, 43, 3031. 72 J. P. Dutasta, J. B. Robert, and M. Vincens, Tetrahedron Lett., 1979, 933. 73 W. Vogt, Phosphorus Sulfur, 1978, 5, 123. 74 A. Suarato, P. Lombardi, C. Galliani, and G . Franceschi, Tetrahedron Lett., 1978, 4059.

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102

0

Organophosphorus Chemistry

I I C0,Me C0,Me

Reagents: i, R2COzH, (Me0)3P, benzene. Scheme 12

the sulphur function as a leaving group. The presence of trimethyl phosphite also greatly improves the yield in the alkylation of certain alkyl vinylcuprates;76 no explanation has been offered.

Spin-labelled phosphites, e.g. (93, have been synthe~ized.~~

3 Phosphonous and Phosphinous Acids and their Derivatives A new synthesis of cyclic esters of arylphosphonic and arylthiophosphonic acids from aryl phosphorochloridous esters has been reported (Scheme 13)."

25-75% 40%

Reagents: i, Cu2B1-2, MeCOzEt; ii, HzO; iii, HzS. Scheme 13

Phosphinic anhydrides readily rearrange to bisphosphine monoxides ; however, stable gold(1) complexes (97) have now been prepared by partial hydrolysis of the chlorophosphine complex (96).7s

76 H. Westmijze, H. Keijn, and P. Vermeer, Tetrahedron Lett., 1978, 3125. 7' G. V. Roschenthaler and W. Storzer, Phosphorus Sulfur, 1978, 4, 373. 77 Z. E. Golubski and Z. Skrowaczawska, Synthesis, 1979, 21. 71 H. Schmidbaur, A. A. M. M y , and U. Schubert, Angew. Chem., Znt. Ed. Engl., 1978, 17,

846.

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Tervalent Phosphorus Acids 103

6-Oxoalkyl-phosphine oxides (98) have been synthesized by the Arbusov reaction of protected b-halogeno-aldehydes and -ketones, and have been shown to cyclize in the presence of acid to 2-hydroxyphospholan 1-oxides (99).7s

R o

79 S. Musierowicz, W. T. Waszktic, and H. W. Krawczyk, Phosphorus Surfur, 1979, 5, 377

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