Organocatalytic asymmetric aza-Nazarov cyclization of an azirine

摘要

An unusual organocatalytic asymmetric cyclization of a keto-azirine that is accompanied by a kinetic resolution leads to 4-hydroxy-3-oxo-1,2,3,6-tetrahydropyridine-2-carboxylates in >99/1 er.rnThe Nazarov cyclization provides one of the most effective means of forming cyclopentenones and has been applied to the total synthesis of diverse natural products. As a part of our program to develop asymmetric Nazarov reactions we have identified 1,2-diamines as promising scaffolds for organo-catalysts for the Nazarov cyclization. We had postulated that α-aminodienones and their derivatives might be useful substrates for Nazarov cyclization. This led us to the synthesis that has been summarized in Scheme 1.