Rate Enhancement and Enantioselectivity of the Jacobsen-Katsuki Epoxidation: The Significance of the Sixth Coordination Site.

New light on the origin of the high enantioselectivities achieved in the Jacobsen-Katsuki epoxidation is shed by the results of density functional calculations. Axial ligation to the metal center not only enhances the epoxidation rate, but in addition leads to highly nonplanar, bent conformations of the active catalyst.