Phosphines, Trimethylsilyl coupling

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... 

In contrast to phosphonic acids, H-phosphinic acids can be coupled with alcohols using carbodiimides to give H-phosphinates 83 (Scheme 31, Table 12).[63-1231 These H-phosphinates 83 afford the corresponding phosphonic acids 84 directly by oxidation with NaI04[123l or by treatment with bis(trimethylsilyl)amide followed by carbon tetrachloride, triethylamine, and waterJ63 Alternatively, as described above (Section 10.10.2.1.3), H-phosphinates may also be converted into the phosphonochloridates by oxidation with carbon tetrachloride and then coupled to nucleophiles other than water, f63-75-76 ... 

Other miscellaneous syntheses that have benefited from the introduction of dppf to the catalytic mixture include the coupling reactions of aryl triflates or halides with ketene trimethylsilyl acetals [165], The catalyst mixture is [Pd(OAc)(i -C4H7)]2/LiOAc/phos-phine. In this case, nucleophilic activation of the Si-O bond of the acetal enables an Si-Pd transmetalation to give a a-complex 52 without necessitating a phosphine... 

Tunney and Stille88 described the coupling of diphenyl(trimethylsilyl)phosphine or (trimethylstan-nyl)diphenylphosphine with various aryl halides, in the presence of a palladium catalyst, to give aryldiphenylphosphines, e.g., (56), according to Equation (17). Unfortunately the reaction conditions are not compatible with functional groups such as N02, CHO, NH2, or OH. 

The role of silylated reagents in the formation of oligopeptides has been explored . Here, the bis(trimethylsilyl) ester of the [l-(trimethylsilylamino)alkyl]phosphonic acid is coupled with an activated A -cbz-amino acid and the silyl groups are subsequently removed under aqueous conditions the process can then be repeated. Oligopeptides have also been obtained as the result of enzyme catalysis when the condensations between amino carboxylic esters and (a) A -protected (aminoalkyl)phosphonic esters or (b) A -protected [(aminoalkyl)methyl]phosphinic esters is brought about in the presence of (a) alkaline phosphatase (Ej) and phosphodiesterase (E2) and (b) alkaline phosphatase and total bee venom (E3) (the latter aiding in the removal of both carboxylate ester and A -acetyl groups) ... 

Tinney and StUle reported the first C—P bond formation using silyl and stannyl phosphines with aryl iodides (Scheme 20.69) [231], Under these conditions, aryl chlorides and aryl bromides are ineffective. The coupling of terf-butyl(trimethylsilyl)phosphine has been subsequently accomplished with aiyl halides [232], Rossi and coworkers reported the coupling of (trialkylstan-nyl)diphenylphosphines with aryl iodides [233]. The reaction conditions can be extended for the coupling of aryl triflates using Cul as cocatalyst [234]. 

Hydrazobenzenes with a chalcogenophosphoryl group were prepared by the reduction of 2-iodoazobenzene with hydrazine hydrate followed by a Pd(ii)-cata-lyzed cross-coupling with diphenylphosphine. The P(in) function was subsequently oxidised by hydrogen peroxide, sulfur and selenixun (Scheme 22) It was possible to restore the azobenzene structure by oxidation. The radical phosphination of aryl iodides by chlorodiphenylphosphine in the presence of tris(trimethylsilyl)silane, 1,1 -azobis(cyclohexane-l-carbonitrile) (V-40) and pyridine led to aryldiphenylphos-phines that were converted to the P-sulfides (Scheme 23). ... 

---