The thermal decomposition of 1-methyl-1,2,3-benzotriazin-4-(1H)-one: matrix isolation of the reactive intermediates

Thermal decompostion of 1-methyl-1,2,3-benzotriazian-4(1H)-one (1) above 120°C gave rise to 1-methylbenzazetinone (2), which was trapped in solid argon at 15 K; near-UV irradiation of (2) converted it partially into its iminoketene isomer (3), and the reverse conversion of (3) into (2) was effected with longer wavelength irradiation.