Carbon-silicon bond formation hydrosilylation

Organic silane derivatives with hydrolyzable groups on silicon (—OR, —Cl, —0C(0)R, etc.) are usually derived from a chlorosilane. Before or after formation of a carbon-silicon bond by hydrosilylation, the chlorosilanes are commonly converted to alkoxysilanes ... 

None of these difficulties arise when hydrosilylation is promoted by metal catalysts. The mechanism of the addition of silicon-hydrogen bond across carbon-carbon multiple bonds proposed by Chalk and Harrod408,409 includes two basic steps the oxidative addition of hydrosilane to the metal center and the cis insertion of the metal-bound alkene into the metal-hydrogen bond to form an alkylmetal complex (Scheme 6.7). Interaction with another alkene molecule induces the formation of the carbon-silicon bond (route a). This rate-determining reductive elimination completes the catalytic cycle. The addition proceeds with retention of configuration.410 An alternative mechanism, the insertion of alkene into the metal-silicon bond (route b), was later suggested to account for some side reactions (alkene reduction, vinyl substitution).411-414... 

The same type of reaction has been used just recently by Sonnek and coworkers [17] to get access to di(meth)acrylate structures added to siloxanes via hydrolytically stable silicon-carbon bond formation. 2-Heptamethyltrisiloxanylbut-2-en-l,4-diylbismethacrylate is accordingly prepared in 90 % yield by hydrosilylation of the bismethacrylate of 2-butyne-l,4-diol. 

Organosilanes as Reducing Agents. The two principal categories of reductive chemistry of hydridosilanes are hydrosilylation and ionic reduction. Hydrosilylation is the catalyzed addition of a hydridosilane to a multiply bonded system. This chemistry is a principal technology in silicon—carbon bond formation. Ionic reduction by silanes, a class of chemistry more properly considered within the context of organic synthesis, is the subject of detailed reviews (132). 

HydrosilyUUion. This silane is useful for hydrosilylation of alkencs and alkynes because the C—Si bond of the adducts is oxidized by 30% H,0, in the presence of KF, KHF, or NaHCO, with formation of the corresponding alcohol. The oxidation occurs with retention of configuration at carbon. At least one alkoxy group on silicon is necessary for this oxidation. Hydrosilylation followed by oxidation permits conversion of 1-alkenes to anti-Markownikoff alcohols (equation 1) and of internal alkynes to ketones (equation II). 

The hydrosilylation reaction (16,17) is a well known reaction for formation of silicon carbon bonds. When vinyl-containing polysiloxane is reacted with multi-Si-H-containing polysiloxane in the presence of a platinum catalyst, a crosslinked network forms, equation 10. Platinum is so active for the hydrosilylation reaction that inhibitors are added to moderate the rate of crosslinking (18). A typical platinum catalyst used by industry is the so-called Karstedt catalyst (19,20). A reaction of Karstedt s catalyst with a ligand, L (an inhibitor perhaps), is shown in equation 11. 

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