Reversing Site Selectivity in Cu-Catalyzed Borylative Transformations of Aryl-Substituted Vinylsilanes via a Directing Group Strategy.

A directing group strategy is reported to achieve β-selective Cu-catalyzed borylative transformations of aryl-substituted vinylsilanes. While conventional protocols predominantly give α-products, installation of a pyridyl substituent on silicon in combination with an N-heterocyclic carbene-copper system enables efficient reversal of regioselectivity. Both protoboration and carboborylation proceed smoothly, affording diverse vicinal borosilanes in high yields with excellent β-selectivity. Mechanistic studies support the stabilization of the Cu-C intermediate via pyridyl coordination. These vicinal borosilanes exhibit broad synthetic utility to access structurally complex organosilicon compounds.