A simple synthesis of benzocarbazolequinones via o-nitroarylation of 2-hydroxy-1,4-naphthoquinones

The reaction of 2-hydroxy-1,4-naphthoquinones (la-c) with o-fluoronitrobenz enes (2a,b) in the presence of K2CO3 in DMSO at 100 degrees C gave 2-hydrox y-3-(2-nitroaryl)-1,4-naphthoquinones (3a-e) in moderate to fair yields, wh ich in turn were transformed into the corresponding 11H-benzo[a] carbazole- 5,6-dione (6a-e) and SH-benzo[b]carbazole-6, 11-dione (7a-e) derivatives in good yields by catalytic hydrogenation over PtO2 in AcOEt at room temperat ure and 1 atm, followed by exposure to air and then heating at reflux tempe rature.