Thermally induced fragmentation and cyclisation of C-azidohydrazones

C-Azidohydrazones 2 were synthesized from the corresponding C-chlorohydrazones 1 and submitted to thermal decomposition in boiling benzene. Various kinds of products were obtained due to competitive modes of evolution of first-formed nitrenes 13 , namely hydrogen abstraction to form aminohydrazones 3 and benzotriazepine 8 , and radical fragmentation to give ultimatively diaryls 4 and arylglyoxylate arylhydrazones 5 . Ring-closed products, namely 1, 2, 4-triazoles 6 and imidazolones 7 were also formed.