Bis(pinacolato)diboron-Enabled Ni-Catalyzed Reductive Coupling of Alkyl with Aryl/Vinyl Electrophiles

The chemistry herein stresses the use of economic and environmentally friendly (bispinacolato)diboron, as the non-metallic reductant that enables the reductive cross-coupling of alkyl electrophiles with aryl/vinyl halides to afford C(sp3)–C(sp2) bond forming products. The present method displays equivalent coupling efficiencies to those reported ones using Zn and Mn as the terminal reductants that have predominated the field of cross-electrophile coupling. Our mechanistic studies support that B2Pin2-mediated reduction of NiII to Ni0, and a radical-chain process emphasizing interception of an alkyl Ni(0) may operate to give alkyl–NiI followed by oxidative addition of ArX to give a key alkyl–NiIII–Ar intermediate prior to ejection of the product. We believe the present study offers insight into the use of B2Pin2 as a non-metallic reductant that does not involve a SET reduction process.