Cascade bicyclizations of o-alkynyl aldehydes with thiazolium salts: a new access toward poly-functionalized indeno[2,1-b]pyrroles

Abstract

A new cascade bicyclization of o-alkynyl aldehydes with thiazolium salts is described, in which 25 examples of densely functionalized indeno[2,1-b]pyrroles are achieved in a functional-group-compatible manner. Thiazole carbenes generated in situ from thiazolium salts play dual roles as reaction partners and as NHC catalysts. The synthetic utility of these bicyclization reactions results in subsequent C–C bond-forming events to rapidly build up molecular complexity.