Hydrosilylation-ethenylation

In a similar manner, the hydrosilylation-ethenylation cycle starting from tetraethenyl-silane (GO) in THF yields up to fourth generation dendrimers . This protocol is combined with reduction of the SiCls moieties by L1A1H4 to afford starburst dendrimers bearing up to 324 Si—H bonds at its periphery . The structure of the second generation dendrimer 267 (G2-H) is characterized by X-ray crystallography . The synthesis of 267 is shown in Scheme 28 as an example. 

Yttrium-catalyzed cascade cyclization/hydrosilylation was also applied to 3-substituted 4-vinyl-1,6-hexadienes. For example, reaction of 5y/7-3-(/ r/-butyldimethylsiloxy)-4-ethenyl-l,6-heptadiene syn-l ) with phenylsilane catalyzed by Gp 2YMe(THF) gave 72a in 72% yield as a 2.1 1 mixture of diastereomers (Equation (47)). Yttrium-catalyzed cascade reaction of the corresponding diastereomer anti-1 was more effective and gave 72b in 78% yield as a 7.2 1... 

Hydrosilylation-polymerization provides a new approach to the syntheses of macromonomers such as poly(arylene-silylethylene) and poly(aralkylene-silylethylene) (274) that possess reactive ethenyl and SiH termini for further manipulations through self-polyaddition of 273 promoted by Speier s catalyst (equation 103)272. 

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