Metal-catalyzed C-H bond annulation strategy offers a versatile platform, allowing the construction of complex p-chiral molecules through atom- and step-economical fashion. However, regioselective insertion of -coupling partner between M-C bond and high enantio-induction remain elusive. Using commercially available Co(II) salt and chiral-salox ligands, we demonstrate an unorthodox protocol for the regio-reversal, enantioselective C-H bond annulation of phosphanamide with bromoalkyne through asymmetric desymmetrization. This method was accomplished by sequentical C-H bond activation, regioselective migratory insertion, reductive elimination, and ligand exchange with carboxylate, which resulted in the formation of novel P-stereogeneic compounds with good substrate scope and high ee (up to 99% ee). The isolation of reactive intermediates involved in the catalytic cycle and the outcomes of control experiments provide support for a plausible mechanism.
Reversing the Regioselectivity of Asymmetric C ̶ H and N ̶ H Bond Annulation with Bromoalkynes Under Cobalt(III)-Catalysis