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

While migratory functionalization of alkynes has been recognized as a unique way to access allylic functionalities via π-allyl metal intermediates, hydrofunctionalization of 2-alkynes to afford α-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 α-vinylsilanes and α-vinylgermanes by a mechanistic understanding of the cobalt hydride species on alkyne π-bond migration. The key mechanism of alkyne π-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 α-vinyl selectivity.