Zinc-Catalysed Hydroboration of Terminal and Internal Alkynes.

A regioselective hydroboration of alkynes has been developed by using commercially available zinc triflate as a catalyst, in the presence of catalytic amount of NaBHEt3 . The reaction tolerates a wide range of terminal alkynes having several synthetically useful functional groups and proceeds regioselectively to furnish hydroborated products in moderate to excellent yields. This system shows moderate chemoselectivity towards terminal C≡C bond over terminal and internal C=C bond and internal C≡C bond.