Ni-Catalyzed Enantioconvergent Kumada–Corriu Cross-Coupling between β‑Bromostyrenes and Secondary Grignard Reagents: Reaction Development, Scope and Mechanistic Investigations

A Ni-catalyzed enantioconvergent cross-coupling between β-bromostyrenes and secondary Grignard reagents is reported. This C(sp2)–C(sp3) cross-coupling is applicable to a broad range of electrophilic and nucleophilic partners and affords the products in good to high levels of enantio-induction. Experimental mechanistic investigations revealed an unexpected binding mode of the chiral (P,N) ligand and support a radical rebound mechanism involving in-cage radicals. Kinetic experiments provide evidence for an off-cycle resting state featuring dinuclear species. Computational analyses are in line with this hypothesis and coherent with a catalytic cycle proceeding via a Ni(I)/Ni(III) manifold. They further suggest an enantio-determining radical capture event and shed light on the origin of the Dynamic Kinetic Resolution process.