Organosilane Reduction of Ethers

The organosilane reduction of ketones in the presence of alcohols provides an excellent route to unsymmetrical ethers. The reaction of cyclohexanone with ethanol and Et3SiH/TFA gives cyclohexyl ethyl ether in good yield.327,328 The... 

Ally halides (equation 37), vinyl halides (equation 38) and vinyl ethers are good substrates for the preparation of organosilanes having functional groups at the 3- or 7-position. Reduction of these substrates sometimes takes place to give the parent alkenes (equation 37), which are derived from 3-elimi-nation of the regioisomeric hydrosilylation intermediates. ... 

Organosilanes bearing a phosphine imide moiety have been synthesized from phosphine imide in ethyl ether and characterized crystallographically. In ether solution, a dynamic equilibrium exists between the chelated pentacoordinated and unchelated tetra-coordinated silicon moieties. Reaction of the pentacoordinated derivative with water gives [2-(diphenylphosphino)phenyl]diphenylsilanol accompanied by both reduction of the phosphine imide moiety and the hydrolytic oxidation of the Si-H moiety." °... 

Recently, Schaumann et al. 153,154 an(j Bienz et tf/.155,156 have developed dependable routes for the resolution of racemic functionalized organosilanes with Si-centered chirality using chiral auxiliaries, such as binaphthol (BINOL), 2-aminobutanol, and phenylethane-l,2-diol (Scheme 2). For instance, the successive reaction of BINOL with butyllithium and the chiral triorganochlorosilanes RPhMeSiCl (R = /-Pr, -Bu, /-Bu) affords the BINOL monosilyl ethers 9-11, which can be resolved into the pure enantiomers (A)-9-ll and (7 )-9-11, respectively. Reduction with LiAlFF produces the enantiomerically pure triorgano-H-silanes (A)- and (R)-RPhMeSiH (12, R = /-Pr 13, -Bu 14, /-Bu), respectively (Scheme 2). Tamao et al. have used chiral amines to prepare optically active organosilanes.157... 

Functional groups may already be present in the polymer structures of the chemicals or can be added to the surface by various chemical treatments, depending on the molecular configuration of the specific polymer required for modification. For example, the polymer PMMA, which consists of methyl ester groups, can be chemically modified by a simple reduction reaction to alcohols, with lithium aluminum hydride in ether-based solutions, followed by the widely used organosilane... 

This chapter covers preparations of organosilicon reagents and their use in organic synthesis. Because many books, book sections,and reviews are already available on these topics and only a limited space is available here, this chapter focuses on the reactions that involve cleavage of C-Si bonds for C-C bond formation, aldol reactions of silyl enol ethers, and oxidation of C-Si bonds. Therefore, topics concerning carbonyl reduction and the protection of functional groups, such as hydroxy with organosilanes, are not included in this chapter. 

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