Silylphosphines reactions

Lithium aluminium hydride has been used to cleave a furfuryl group from a range of furfurylphosphonium salts, which are easily accessible by the reactions of trimethylsilylphosphines with furfuryl bromide. Thus, e.g., the reaction of diphenyltrimethyl-silylphosphine yields the salt (52) which, on treatment with... 

The thermolysis of a linear (fluorostannyl)silylphosphine has been reported to give the corresponding stannaphosphene.8 This reaction can be considered to be a defluorosilylation and, as such, is analogous to the dehydrohalogenation reactions discussed below. 

Silylphosphines add thermally to the carbon-carbon triple bond of acetylenic ketones. The reaction affords (Z)-a-silyl-/Tphosphino-a,/3-unsaturated ketones via regioselective cis- 1,2-addition (Equation (124)).286... 

Dialkyl(trimethylsilyl)phosphines undergo 1,4-addition to a,/3-unsaturated ketones and esters to give phosphine-substituted silyl enol ethers and silyl ketene acetals, respectively. A three-component coupling reaction of a silylphosphine, activated alkenes, and aldehydes in the presence of a catalytic amount of GsF affords an aldol product (Scheme 76).290 291... 

Silylphosphines are known to add to aldehydic carbonyl groups.292 The reaction between Me3Si-PPh2 and chiral aldehydes proceeds with a high diastereoselectivity to afford ct-siloxyalkylphosphines (Equation (125)).293... 

Addition reactions of silylphosphines to imines have been reported, 4 as illustrated for diethyl(trimethylsilyl)phosphine (70). Organic azides react with germylphosphines by an insertion pathway,65 as shown for various phenyl(trimethylgermyl)phosphines (71). The initial products (72) isomerize to phosphine imines on heating.66... 

With ethyl iodide, ethylphosphine and phosphine are formed. The reaction with excess silyl bromide results in the formation of silylphosphine. Silylphosphine, like methylphosphine, forms an adduct with diborane... 

The most direct synthesis is performed by reaction of a dihalo compound with a tricoordinated phosphorus compound including a reactive P—Y bond (reaction 101). This synthesis, first used with secondary phosphines, the corresponding phosphides or diphosphines (Y = H, Na, K, PPh2)2b,38°, has subsequently been developed also with silylphosphines (Y = SiMe3),132,381-383 which are easier to handle (reaction 102). The same kind of cyclization by intramolecular alkylation can be achieved using a functional phosphine prepared in a multi-step synthesis380,384,385 (reaction 103). 

Tri-t-butylphenyl)(trimethylsilyl)phosphine (10a) and its t-butyldimethylsilyl analog (10b) were prepared from (2,4,6-tri-t-butylphenyl)phosphine33 (equation 76)3. Treatment of the silylphosphines 10a or 10b with n-butyllithium led to the formation of silylphosphides 11a and lib3, which were utilized for the reactions shown in Section V. (2,4,6-Tri-r-butylphenyl)(triphenylsilyl)phosphine and related compounds were also prepared starting from Mes PH i (equation 77) and their structures were analyzed27,89. 

Reaction of 10a with Mes P=C=0 afforded the adduct 12 (equation 78)90. It should be noted that compounds of the Mes P=C(OSiR3)PHMes type were converted to Mes P=C=PMes by addition of alkyllithiums90,91. Isophosphaethyne complexes were prepared using 10a as well as the related silylphosphines (equation 79)92. Stable cis-diphosphene was prepared from 10a and a dichloroaminophosphine, and its structure was analyzed by X-ray crystallography (equation 80)93. 

Si-H containing silylphosphines, however, leads to cleavage of an Si-P bond and alkylation at silicon. These reactions, and many other interesting cyclic and acyclic phosphines, most of which contain alkyl groups on sihcon, are discussed in more detail by Fritz. ... 

The reaction of tertiary alkyl- or aryl-phosphines with hexachloroethane results in the formation of dichlorophosphoranes (76) and tetrachloroethene. In contrast, the silylphosphines (77) react with equimolar amounts of hexachloroethane to give a... 

Several syntheses of trimethylsilylphosphines have been described. Thus the silylphosphines (59) have been prepared by a Grignard-type reaction. 

Silylphosphines can add across the C==N bond in aldimines as shown in equation (42) to produce compounds containing an Si—N—C—P atom sequence further reactions with di-imines and N-acylimines have also been reported. ... 

The reactions of silylphosphines with electron-rich compounds are complex, involving insertion into the Si-P bond as the first step. With carbon dioxide, bis(silyl)phosphines give an equilibrium (equation 20) dominated by the phosphacarbamic acid ester 8 which loses disiloxane if R = 2,4,6-t-Bu3C6H2 (henceforth represented as Ar) to give the phosphaketene 9. This in turn reacts with the silylphosphide 10 to form the 1,3-phosphaallene 11, an analogue of carbodiimides, and also results directly from ArPHSiMe3, n-BuLi and C02 (equation 21)28. 

The chemistry of acylphosphines continues to attract attention. Reactions of acyl chlorides with silylphosphines have now been applied to the synthesis of a... 

Alkylation or arylation of silylated alkylarylphosphines 214 instead of P-H phosphines for the preparation of chiral tertiary phosphines in some cases led to an appreciable increase of enantioselectivity. For example, as reported by Toste and Bergman [133], the reaction of arylsubstituted iodides with silylphosphines 214 catalyzed by Pd(Et-FerroTANE)Cl2, in the presence of -dimethyl-W,W,Af-pro-pylene (DMPU) led to the formation of P-chiral tertiary phosphines 215 with 55-98% ee (Scheme 69). 

R=MeO, MeS, COOBu-t, COOC6H4Me2-2,6, COONEtj, COONPr-ij Scheme 69 Reaction of aryl iodides with silylphosphines 214 catalyzed by Pd complex... 

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