Indolo[3,2-b]carbazole is a molecule of great biological significance, as it is formed in vivo after consumption of cruciferous vegetables. The reaction of 1H-indole and various aldehydes in the presence of a catalytic amount of N,2-dibromo-6-chloro-3,4-dihydro-2H-benzo[e][1,2,4]thiadiazine-7-sulfonamide 1,1-dioxide as an efficient and homogeneous catalyst in acetonitrile at 50°C produces 6,12-disubstituted 5,7-dihydroindolo[2,3-b]carbazole with an in good to excellent yield. The presented technique offers a fast and robust method, by the use of inexpensive commercially available starting materials toward 6,12- disubstituted 5,7-dihydroindolo[2,3-b]carbazole. A new anomeric-based oxidation was kept in mind for the final step of the indolo[2,3-b]carbazoles synthesis. The suggested anomeric-based oxidation mechanism was supported by experimental and theoretical evidences.
