Mechanism and Origins of Enantioselectivity of Cobalt-Catalyzed Intermolecular Hydroarylation/Cyclization of 1,6-Enynes with N-Pyridylindoles.

Density functional theory calculations were performed to investigate the cobalt-catalyzed intermolecular hydroarylation/cyclization of 1,6-enynes with N-pyridylindoles. The computations reveal that the reaction begins with the oxidative cyclization of 1,6-enyne to afford the five-membered cobaltacycle, from which the metal-assisted σ-bond metathesis/C-C reductive elimination led to the final hydroarylation/cyclization product. The initial oxidative cyclization constitutes the rate-determining step of the overall reaction. The steric repulsion and π···π interaction were found to play a crucial role in dictating the experimentally observed enantioselectivity.