文摘
A regioselective nucleophilic addition to 3-geminal bis(silyl) N-acyl pyridinium has been described. Geminal bis(silane) shows contrasting roles that lead to different regioselectivities for the addition of different nucleophiles: its steric effect dominates to favor 1,6-addition of alkyl, vinyl, and aryl organometallic reagents; its directing effect dominates to favor 1,2-addition of less sterically demanding alkynyl Grignard reagents.