Regioselective Access to alpha-Vinylsilanes and alpha-Vinylgermanes by Cobalt-Catalyzed Migratory Hydrofunctionalization of 2-Alkynes

Abstract

While migratory functionalization of alkynes has been recognized as a unique way to access allylic functionalities via pi-allyl metal intermediates, hydrofunctionalization of pi-alkynes to afford alpha-functional olefins has been unexplored. We describe herein the use of a cobalt hydride based system for regioselective migratory hydrofunctionalization of 2-alkynes to furnish alpha-vinylsilanes and alpha-vinylgermanes by a mechanistic understanding of the cobalt hydride species on alkyne pi-bond migration. The key mechanism of alkyne pi-bond migration by [bis(dicyclohexylphosphino)ethane]cobalt hydride is strongly supported by both experimental and computational studies, and the role of each reaction component, such as alkynes and silanes, is elucidated to rationalize the unique alpha-vinyl selectivity.