Flash vacuum pyrolysis of 1,5-benzodiazepines

Article abstract of DOI:10.1016/S0040-4020(98)00523-7

Gas-phase pyrolysis of the 2,4-diphenyl- and 2,4-dimethyl-1,5- benzodiazepines 3 and 4 at 800-850 °C gave a range of heterocyclic products (e.g. quinoxalines 8, 10 and 11, indole 9, benzimidazole 5 and pyrazole 7) in low yields. The formation of most products is initiated by cleavage of the 2,3-bond to give a diradical intermediate, though the pyrazole is obtained by a mechanism involving a 1,5-hydrogen shift followed by an unusual ring contraction.