Diastereoselectivity in Passerini Reactions of Chiral Aldehydes and in Ugi Reactions of Chiral Cyclic Imines

Diastereoselectivity in Passerini and Ugi reactions of chiral aldehydes/imines remains challenging. Moreover, the Ugi reaction of chiral acyclic imines is complicated by their easy racemization/epimerization, whereas this problem is nearly completely suppressed using chiral cyclic imines in a modification called Ugi-Joullié reaction. Thus 3-component modification also allows a better diastereoselectivity thanks to the higher steric rigidity of rings. This review presents an overview of the current knowledge on diastereoselective Passerini reaction of chiral aldehydes, and on diastereoselective Ugi-Joullié reaction of chiral cyclic imines, focusing on the results gathered by the authors' research group