Calcium(ii)-catalyzed [2+3] annulation of enynones: a sustainable approach to 9H-pyrrolo[1,2-a]indole frameworks

Abstract

A Ca(II)-catalyzed, atom-economic, and regioselective [2+3] annulation reaction has been developed to synthesize 9H-pyrrolo[1,2-a]indoles by using easily accessible tryptamines and enynones. This protocol exhibits broad functional group tolerance; thus, 9H-pyrrolo[1,2-a]indole frameworks with diverse substitution patterns can be synthesized. The synthetic utility of this method is further demonstrated through its effectiveness in gram-scale preparations and versatile synthetic transformations.