Synthesis of Azapyrrolo[3,2,1-jk]carbazoles, Azaindolo[3,2,1-jk]carbazoles, and Carbazole-1-carbonitriles by Gas-Phase Cyclization of Aryl Radicals

Abstract

Flash vacuum pyrolysis of N-(2-nitroheteroaryl)indoles or-carbazoles at 875°C gave aza analogues of strained pyrrolo[3,2,1-jk]carbazole (50-55%) and indolo[3,2,1-jk]carbazole (55-85%) ring systems, respectively, through generation of aryl radicals and cyclization. The corresponding reactions of N-(2-nitroheteroaryl)indazoles and-benzimidazoles at 850°C, on the other hand, gave carbazole-1-carbonitrile derivatives (56-64%) by a mechanism involving radical ring opening and hydrogen atom rearrangement.