Silicones olefin addition method

Our interest in silicon chemistry quite naturally led to a study of the hydrosilation reaction, the addition of the Si-H group across an olefin or an acetylene. This reaction is one of the most useful methods of making silicon-carbon bonds and is an important industrial process. Typically, homogeneous catalysts based on platinum, rhodium or ruthenium are used, and while very efficient, they are not recoverable(46). 

It is likely that more silicon-carbon bonds are produced by the hydrosilylation of olefins than by any other method except the direct process. This deceptively simple addition of an Si-H bond to a C-C multiple bond can be promoted by a variety of means, but transition metal catalysis is by far the most significant. Two relatively old catalysts, H2PtCl6 ( Speier s catalyst ) and Pt2(Me2ViSiOSiMe2Vi)3 ( Karstedt s catalyst ), remain the most effective, and the remarkable rates and turnover numbers observed in these systems are among the most impressive in all of organometallic chemistry. The bulk of the literature on hydrosilylation falls outside the scope of this review, and readers are directed to the comprehensive work on hydrosilylation edited by Marciniec.93... 

Fig. 15.14. Comparison of specific catalytic activities of Ni and Cu nanoparticles deposited onto a thermally oxidized silicon by laser electrodispersion (n m 5 x 1012cm-2) with those of catalysts prepared by the method of impregnation and reduction (1% Ni/Si02, 1% Cu/Si02). Reaction of carbon tetrachloride addition to olefins.

The peroxide-catalyzed addition of trichlorosilane or methyldichlorosilane to olefins affords a new method of synthesizing organochlorosilanes.1 It is possible to effect reaction between trichlorosilane and pentene, cyclohexene, isobutylene, and acetylene. A similar reaction takes place between trichlorosilane and both vinyltrichlorosilane and allyltrichlorosilane. In each case, the corresponding alkyl silicon derivatives can be isolated. The synthesis of cyclo-hexyltriehlorosilane is described below as an example of the general procedure. Cyclohexyltrichlorosilane has also been prepared by the Grignard reaction.2... 

The Peterson olefination may also be applied to the preparation of a,P-unsatu-rated esters, thus providing an attractive alternative to the HWE phosphonate method. For example, deprotonation of trimethylsilylacetate with RjNLi followed by addition of cyclohexanone yields the intermediate P-hydroxysilane, which, on elimination of the silicon-oxygen moieties, furnishes ethyl cyclohexylidene-acetate. ... 

Researchers fundamentally interested in C-C bond-forming methods for polyketide synthesis have at times viewed allylation methods as alternatives, and maybe even competitors, to aldol addition reactions. Both areas have dealt with similar stereochemical problems simple versus absolute stereocontrol, matched versus mismatched reactants. There are mechanistic similarities between both reaction classes open and closed transition states, and Lewis acid and base catalysis. Moreover, there is considerable overlap in the prominent players in each area boron, titanium, tin, silicon, to name but a few, and the evolution of advances in both areas have paralleled each other closely. However, this holds for an analysis that views the allylation products (C=C) merely as surrogates of or synthetic equivalents to aldol products (C=0). The recent advances in alkene chemistry, such as olefin metathesis and metal-catalyzed coupling reactions, underscore the synthetic utility and versatility of alkenes in their own right. In reality, allylation and aldol methods are complementary The examples included throughout the chapter highlight the versatility and rich opportunities that allylation chemistry has to offer in synthetic design. 

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