Visible-light-driven proton reduction for semi-hydrogenation of alkynes via organophotoredox/manganese dual catalysis.

Described here is a unprecedented organophotoredox/manganese dual catalyzed proton reduction and its application for semi-reduction of alkynes. The catalytic active pre-catalyst [Mn-1] can be feasibly be prepared on gram-scale from Mn(acac) 2 ·2H 2 O in air. This dual catalytic protocol features noble-metal-free catalysts, simple ligand, and mild conditions. Besides, a unique ortho -halogen and -hydroxyl effect was observed to achieve high Z -stereoselectivity.