Synthesis of benzocarbazoles, indoloquinolines and indolonaphthridines from thermolysis of benzoenynyl ketenimines and carbodiimides

The development of a general route to the N-[2-(1-alkynyl)phenyl]ketenimines (enyne-ketenimines) and N-[2-(1-alkynyl)phenyl]carbodiimides (enyne-carbodiimides) and their subsequent thermal behavior are described. Like enyne-allene and enyne-ketene systems, these enyne-hetereocumulenes undergo cycloaromatization through two competing biradical mechanisms under thermal conditions and therefore could serve as potential DNA cleaving agents. The resultant nitrogen-containing hetereocyclic compounds are also biologically interesting. The research described herein provides a easy access to the synthesis of benzo[b]carbazole, indoloquinoline and indolonaphthyridine alkaloids. In addition, the new synthetic strategies for these compounds are very versatile, providing access to a diverse array of analogs of these alkaloids