Aluminum-Catalyzed Selective Hydroboration of Alkenes and Alkynylsilanes

An efficient aluminum-catalyzed selective hydroboration of alkenes and alkynylsilanes is reported. A wide variety of alkenes and alkynylsilanes bearing various functional groups and heterocyclic substituents were converted to boronic ester products in good yields with high selectivity. Mechanistically, density functional theory calculations favored a mechanism involving the insertion of the double bond into the Al–H species followed by C–Al/B–H metathesis.