Modular Access to Tetrasubstituted N‐H Pyrroles by Catalytic 1,3‐Dipolar Cycloaddition of Azomethine Ylides and α,β‐Ynones

Abstract

The development of efficient synthetic strategies for the preparation of tetrasubstituted N‐H pyrrole derivatives, especially in an environmentally benign fashion, still remains momentous, yet challenging. Herein, we report a Cu(II)‐catalyzed tandem reaction of 1,3‐dipolar cycloaddition of α,β‐ynones and glycine iminoesters, followed by Cu(II)‐promoted oxidative (air) dehydrogenative aromatization, allowing de novo access to tetrasubstituted N‐H pyrroles in up to 81% yield under green reaction conditions. The possible reaction pathway is tentatively proposed. Finally, fully substituted pyrroles can be available via N‐alkylation, and the preliminary phase‐transfer catalytic asymmetric N‐alkylation is also studied to give an axially chiral pyrrole.