Aminocatalysis: beyond steric shielding and hydrogen-bonding.

The stereochemical outcome of most aminocatalytic transformations is determined by the steric-shielding or hydrogen-directing approach. However, in recent years several reactions have appeared in which the stereochemical outcome is beyond these two approaches. This Concept article will highlight such reactions and postulate that the stereochemical outcome can be accounted for by electrostatic interactions between the catalyst-bound substrate and the reagent in the transition state.