Enantioselective Addition of Amines to Ketenes Catalyzed by a Planar-Chiral Derivative of PPY:  Possible Intervention of Chiral Brønsted-Acid Catalysis

The first method for the catalytic enantioselective addition of amines (specifically, pyrroles) to ketenes has been developed, and it has been demonstrated that the resulting acylpyrroles can be transformed into a broad spectrum of useful derivatives. On the basis of mechanistic studies, it is suggested that the planar-chiral catalyst plays an unanticipated role in this process as a chiral Brønsted acid.