Unlocking Nucleophilic Reactivity in Co-MHAT Catalysis: Stereospecific Backside-Backside Displacement via Anion-Activated Organocobalt Intermediates

The recent renaissance of olefin hydrofunctionalization based on cobalt-catalyzed hydrogen atom transfer (Co-MHAT) has primarily focused on two pathways: the homolytic cleavage of the alkyl-CoIII intermediate, and its electrophilicity upon oxidation. In contrast, a third pathway, which leverages the two-electron nucleophilic potential of alkyl-CoIII, has remains unexplored due to the inherently low polarization of the C–Co bond. Here, we report an axial-coordination activation strategy to unlock this new reactivity space in Co-MHAT catalysis. Through stoichiometric organometallic studies using well-defined alkyl–CoIII complexes, we demonstrate that an alkoxide ligand can render alkyl-CoIII sufficiently nucleophilic to displace a suitable leaving group, via a stereospecific backside-backside approach. This new pathway is further applied in catalysis, enabling a diastereoselective redox neutral Co-MHAT cyclopropanation reaction.