Borane-Catalyzed Reductive alpha-Silylation of Conjugated Esters and Amides Leaving Carbonyl Groups Intact

摘要

Described herein is the development of the B(C6F5)(3)(-)catalyzed hydrosilylation of alpha, beta-unsaturated esters and amides to afford synthetically valuable alpha-silyl carbonyl products. The a-silylation occurs chemoselectively, thus leaving the labile carbonyl groups intact. The reaction features a broad scope of both acyclic and cyclic substrates, and the synthetic utility of the obtained alpha-silyl carbonyl products is also demonstrated. Mechanistic studies revealed two operative steps: fast 1,4-hydrosilylation of conjugated carbonyls and then slow silyl group migration of a silyl ether intermediate.