Diphenylsilane, hydrogenation with

Owing to the expense, toxicity, and purification problems associated with use of stoichiometric amounts of tin hydrides, there has been interest in finding other hydrogen atom donors.205 The trialkylboron-oxygen system for radical generation (see Part A, Section 11.1.4) has been used with fra-(trimethylsilyl)silane or diphenylsilane as a hydrogen donor.206... 

It is clear that the ionizing power of the solvent used is important in many of these reductions. When 2,4,6-trimethylbenzyl chloride is heated with diphenylsi-lane in nitrobenzene at temperatures as high as 130°, no isodurene is formed.193 Not unexpectedly, the same lack of reactivity is reported for a series of benzyl fluorides, chlorides, and bromides substituted in the para position with nitro or methyl groups or hydrogen when they are heated in nitrobenzene solutions with triethylsilane, triethoxy silane, or diphenylsilane.193... 

Aryl tellurium trihalides are easily reduced by sodium hydrogen sulfite , sodium or potassium disulfitezinc in refluxing ethanoP, hydrazine hydrate " hypophos-phorous acid °, sodium sulfide nonahydrate , sodium borohydride , thiourea diox-ide, 4-methylbenzenesulfonyl hydrazide , or diphenylsilane. The reductions with sulfites are generally carried out in an aqueous medium in the presence of an immiscible organic solvent that extracts the ditellurium. 

Other than the previously shown hydrogenation, Brunner et al. [43] investigated the hydrosilylation of acetophenone with diphenylsilane and enantiomerically pure, planar-chiral, anionic 7-diphe-nylphosphanyl-8-phenyl-7,8-dicarba-mdo-undecaboraterhodiumcomplexes30and31 (Figure 22.17, Scheme 22.8). Resolution of anionic ligand 37 was achieved via a diastereomeric palladium complex that led to the enantiomerically pure form of the ligand. The precatalyst 30 was obtained by reaction of 37 with [ Rh(fi-Cl)(cod) 2J, whereas both enantiomers of 31 were obtained by the reaction of (R,R)- or (5,S)-D10P, [ Rh([i-Cl)(cod) 2] and 37. 

Barton s group have given full accounts of earlier Inief reports (see Vols. 25 and 26) on the use of phenylsilane, triphenylsilane and triethylsilane, and of diphenylsilane as hydrogen sources in free radical deoxygenations of thionocarbonates, with particular emphasis on the applications of these methods for the preparation of deoxysugars. 

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