Abstract Interaction of 6-chloroquinoline-5, 8-dione hydrochloride (I) or 6, 7- dichloroquinoline-5, 8-dione (II) with sulfa drug in ethanol containing diethylaniline afforded 7-substituted sulfonamide-10H-pyrido [3, 2-b] carbazole-5, 11-dione (III), and sulfonamide derivatives of 7-chloroquinoline-5, 8-diones (IV). Moreover the reaction of II with arylamine in pyridine afforded substituted 6H-pyrido [2, 3-b] carbazole-5, 11-dione (V). The structure of ...