Chiral Brønsted acid catalysis has recently become attractive because of its wide application in various asymmetric syntheses.[1] Among these catalysts, chiral phosphoric acids represent an outstanding example.[2] Whereas phosphoric acids are used to activate imine type compounds, we reported the first preparation of chiral N-triflyl phosphoramide 1a (Scheme 1, Table 1) and its utility in activating a carbonyl group in the asymmetric Diels– ...
