The Origin of Enantioselectivity of Aryl Terminal Alkenes Hydroboration Catalyzed by Cobalt Complex: A Density Functional Theory (DFT) Study

Density functional theory (DFT) studies reveal the origin of the regioselectivity and stereoselectivity in Co-IPO-catalyzed hydroboration of aryl alkenes. Four insertion pathways dictate selectivity, with anti-Markovnikov S-product formation (Path A) being energetically favored. The alkene insertion step and σ-bond metathesis step jointly determine the selectivity of the reaction. In addition, the steric hindrance from the -NPhiPr2 moiety of the IPO ligand critically controls selectivity. Interestingly, substituting -NPhiPr2 with -NCH3 shifts selectivity toward Markovnikov products.