A Novel Synthesis of Aryl- and Heteroaryl - Annulated Carbazoles: Newly Synthesized Pyrido-, Benzo[a]- and Spirooxindolinebenzo[a]-carbazols

A previously unknown class of highly substituted aryl-and heteroaryl-annulated carbazoles such as pyrido[2,3-a] carbazole, benzo[a] carbazole and spiro[indoline-3', 4-benzo[a] carbazole] has been prepared by the condensation of substituted a, adicyanoalkenes and malononitrile with salicylaldehyde, aryl/heteroaryl aldehydes and isatin respectively in good to excellent yield. The structures of the compounds were confirmed spectroscopically (FT-IR, (HNMR)-H-1, (CNMR)-C-13) and by single X-ray diffraction. The generality and functional tolerance of this convergent method is demonstrated. Compared with the former and contemporary reaction methodologies, these approaches afford several advantages such as operational simplicity, simple work-up procedure, higher yield, short reaction time and environment friendly protocols.