Vinylsilane

Abstract: The complex [Cp*Ru(MeCN)3]PF6 is shown to catalyze the hydrosilylation of a wide range of alkynes. Terminal alkynes afford access to α-vinylsilane products with good regioselectivity. Deuterium labeling studies indicate a clean trans addition process is at work. The same complex is active in internal alkyne hydrosilylation, where absolute selectivity for the trans addition process is maintained. Several internal alkyne substrate classes, including propargylic alcohols and α,β-alkynyl carbonyl compounds, allow regioselective vinylsilane formation. The tolerance of a wide range of silanes is noteworthy, including alkyl-, aryl-, alkoxy-, and halosilanes. This advantage is demonstrated in the direct synthesis of triene substrates for silicon-tethered intramolecular Diels−Alder cycloadditions.

Abstract: A series of carbosilane dendritic macromolecules grown from four directions of a tetrahedral central core has been synthesized and characterized. In the synthesis tetravinylsilane is used as the central core molecule and dichloromethylsilane as the propagation unit. Two reactions are involved in the synthesis of each generation: hydrosilylation of vinylsilane with dichloromethylsilane and nucleophilic replacement of silicon chloride by vinylmagnesium bromide. The reaction conditions for hydrosilylation must be well controlled.

Abstract: The trans reduction of all types of alkynes to give (E)-olefins is achieved through a two-stage trans hydrosilylation and protodesilylation. Reaction of an alkyne and a silane with the ruthenium catalyst [Cp*Ru(MeCN)3]PF6 results in clean hydrosilylation to give only the (Z)-trans addition product at ambient temperature with catalyst loadings of 1−5 mol %. The crude vinylsilane products are then protodesilylated by the action of cuprous iodide and TBAF at rt−35 °C. The reaction is compatible with many sensitive functional groups and provides a general trans-alkyne reduction not possible by other means.