Copper-Catalyzed Diboron-Mediated cis -Semi-Hydrogenation of Alkynes under Facile Conditions.

Cis -alkenes are ubiquitous in biological molecules, which makes it greatly significant to develop efficient methods toward construction of cis -olefins. Herein, we reported a facile semi-hydrogenation of alkynes to cis -alkenes in an efficient way with cuprous bromide/tributylphosphine as the catalyst and bis(pinacolato)diboron/methanol as the hydrogen donor. The method features convenient and facile reaction conditions, wide substrate scope, high yields, and high stereoselectivity.