Functionalization of octavinylsilsesquioxane by ruthenium-catalyzed silylative coupling versus cross-metathesis

Functionalization of octavinylsilsesquioxane (Vi(8)T(8), 1) by two reactions catalyzed by ruthenium complexes is reported: a silylative coupling reaction catalyzed by [RuHCl(CO)(PCy3)(2)] (1) and cross-metathesis catalyzed by first- (11) and second-generation (111) Grubbs' catalysts. The two reactions of I with styrene take place highly regio- and stercoselectively (the X-ray structure of the product 2 has also been obtained); the cross-metathesis of 1-hexene and allyltrimethylsilane occurs quite effectively, whereas the silylative coupling with these compounds gives a mixture of isomers. Functionalization of I with heteroatom-substituted vinyl derivatives (Si, O, N) by silylative coupling reaction has been found to be highly efficient, but cross-metathesis appears to be the more effective method for the synthesis of S-substituted vinyl-silsesquioxane.