Rhodium catalysed intramolecular benzannulation for the formation of tetracyclic carbazoles

Rhodium catalyzed alkyne-tethered intramolecular annulation has been demonstrated for the synthesis of tetracyclic carbazole skeletons and a series of five to eight-membered pyrido[3,2,1-jk]carbazoles were successfully obtained. The present atom economical annulation proceeded under mild reaction conditions, offering a broad substrate scope.