Synthesis of symmetric and non-symmetric indolo[2,3-c]carbazole derivatives: preparation of indolo[2,3-c]pyrrolo[3,4-a]carbazoles

Symmetric and non-symmetric indolo[2,3-c]carbazoles have been prepared from 3,3′-biindolyls 9a–d by two strategies; step by step, by thermal electrocyclic reaction, or directly. Indolo[2,3-c]pyrrolo[3,4-a]carbazoles 28aa–db, a new class of indolopyrrolocarbazoles, have been obtained in a one step reaction from readily available precursors.