N-Heterocyclic carbenes as chiral Brønsted base catalysts: a highly diastereo- and enantioselective 1,6-addition reaction.

Highly diastereo- and enantioselective 1,6-addition of 1,3-ketoamides to -quinone methides (-QMs) using chiral NHCs as Brønsted base catalysts is developed. The reaction is based on the utilization of a 1,3-ketoamide having acidic N-H that forms a chiral ion-pair consisting of the enolate and the azolium ion. Different β-ketoamides and functionalized -QMs are applicable to the reaction. Synthetic application of the method is demonstrated the preparation of highly enantioenriched β and γ-lactam derivatives.