Origin of enantioselectivity in asymmetric Pauson–Khand reactions catalyzed by [(BINAP)Co2(CO)6]

The quantum mechanics/molecular mechanics (QM/MM) ONIOM(B3LYP:UFF) approach is applied to the study of the asymmetric carbonylative intramolecular cycloaddition of a HCC-CH₂-N(Ts)-CH₂-CH=CH₂ enyne (Ts = tosyl) catalyzed by [(BINAP)Co₂(CO)₆] (BINAP = (1,1′-binaphtalene)-2,2′,diylbis(diphenylphosphine)). The experimental results, showing formation of the R product when the S-BINAP ligand is used, are reproduced. Comparison of the structures of the computed transition states leading to the R and S products provides a qualitative explanation for the origin of selectivity based on steric repulsions between specific substituents.