Facile one-pot synthesis of novel 6-monosubstituted 5,11-dihydroindolo[3,2-b]carbazoles and preparation of different derivatives

The synthesis of novel 6-monosubstituted 5,1 1-dihydroindolo[3.2-b]carbazoles was accomplished by a three-stage one-pot procedure involving condensation of indole and an aldehyde affording 3,3'-bis(indolyl)methanes, followed by isomerization to the 2,3'-analogues and acid-catalyzed intramolecular reaction with triethyl orthoformate to give the corresponding 6-monosubstituted indolo[3.2-b]carbazoles in good overall yield. Different substitution patterns, such as N-alkylation, N-arylation, formylation and bromination, were successfully introduced, leading to the formation of novel substituted 5,11-dihydroindolo[3,2-b]carbazole derivatives.