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 π‐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‐stereogenic compounds in excellent ee (up to >99 %). The isolation of cobaltacycle involved in the catalytic cycle and the outcome of control experiments provide support for a plausible mechanism. Herein, we demonstrate the cobalt‐catalyzed asymmetric desymmetrization of phosphinamides with haloalkynes with excellent enantioinduction and inverse regioselectivity. In a single step, the approach provides access to several P‐chiral molecules. Based on control experiments and preliminary study, a plausible mechanism is provided.