Reversal of Regioselectivity in Asymmetric C ̶ H Bond Annulation with Bromoalkynes under Cobalt Catalysis

Metal‐catalyzed asymmetric 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 pi‐coupling partner between M‐C bond with high enantio‐induction remain elusive. Using commercially available Co(II) salt and chiral‐Salox ligands, we demonstrate an unusual protocol for the regio‐reversal, enantioselective C‐H bond annulation of phosphinamide with bromoalkyne through desymmetrization. The reaction proceeds through ligand‐assisted enantiodetermining cyclocobaltation followed by regioselective insertion of bromoalkyne between Co‐C, subsequent reductive elimination, and halogen exchange with carboxylate resulted in P‐stereogeneic compounds in excellent ee (up to 99%). The isolation of cobaltacylce involved in the catalytic cycle and the outcome of control experiments provide support for a plausible mechanism.