Importance of Electrostatic Effects in the Stereoselectivity of NHC-Catalyzed Kinetic Resolutions.

Three N-heterocyclic carbene (NHC) catalyzed kinetic resolutions (KR) and one dynamic kinetic resolution (DKR) were examined using modern density functional theory methods to identify the origin of catalytic activity and selectivity and the role of cocatalysts in these reactions. The results reveal electrostatic interactions as the common driver of selectivity. Furthermore, in the case of a recently described KR of BINOL-derivatives, a computational examination of the full catalytic cycle reveals that a benzoic acid byproduct changes the turnover limiting transition step, obviating the need for an added cocatalyst. Together, these data provide key insights into the activity and selectivity of NHC-catalyzed kinetic resolutions, and underscore the importance of electrostatic interactions as a driver of selectivity.