Photoredox/Nickel Dual Catalysis for Regio- and Stereoselective Reductive Coupling of Alkynes with Vinyl Phosphonates.

An efficient nickel-photoredox dual-catalyzed intermolecular reductive coupling reaction of alkynes with vinyl phosphonates is described. The reaction is highly regio- and stereoselective, affording the homoallylic phosphonates in good to high yields. The present protocol is also successfully applied to other activated alkenes such as enones, acrylates, and vinyl sulfone. The reaction is believed to proceed via the nickelacyclopentene intermediate. Mechanistic investigations, including control experiments and isotopic labeling studies, revealed that methanol serves as a proton source rather than a reducing agent.