Synthesis of benzo[a]carbazoles via cyanide-catalyzed imino-Stetter reaction/Friedel–Crafts reaction sequence

Abstract

A new protocol to access benzo[a]carbazole derivatives was developed, via the cyanide-catalyzed imino-Stetter reaction/Friedel–Crafts reaction sequence. The cyanide-catalyzed imino-Stetter reaction of aldimines derived from 2-aminochalcones and aromatic aldehydes provided the corresponding 2-aryl-3-arenacylindole derivatives, which could be converted to benzo[a]carbazoles via intramolecular Friedel–Crafts ractions. Various 2-aminochalcones and aldehydes were applicable to this protocol, affording the desired benzo[a]carbazoles in good to high yields. Furthermore, we also developed a sequential protocol for the construction of benzo[a]carbazoles from 2-aminochalcones and aldehydes, without isolating any intermediates.