Dipolar Cycloaddition-Based Multicomponent Reactions

As an extension of this methodology, these authors employed the same catalyst to induce a three-component synthesis of chiral pyrrolidines [350]. The first step of the domino process consisted in an imine formation between 2-aminomalonate and an aldehyde. Its corresponding azomethine yUde, prepared in situ, reacted with a,P-unsaturated aldehydes, furnishing the final products in good yields (51-63%) and diastereo- and enantioselectivities of 50-82% de and 92-98% ee, respectively. Various aromatic and ahphatic enals were compatible acceptors in this process, as were a broad range of berrzaldehydes. In 2008, a three-component reaction of aldehydes, diaUcyl maleates, and a-amino esters was described by Gong et al. [351]. The 

(a) Noyori, R. (1994) Asymmetric Catalysts in Organic Synthesis, John Wiley Sons, Inc., New York, (b) Jacobsen, E.N., Pfaltz, A., and Yamamoto, H. 

and Riebel, B.R. (2004) Biocatalysis, Wiley-VCH Verlag GmbH, Weinheim. 

(a) Dalko, P.I. and Moisan, L. (2001) Angew. Chem. Int. Ed., 40, 3726-3748. (b) Berkessel, A. and Groger, H. (2005) Asymmetric Organocatalysis-From Biomimetic Concepts to Powerful Methods for Asymmetric Synthesis, Wiley-VCH Verlag GmbH, Weinheim. (c) Seayad, 

---