Flash-vacuum pyrolysis of N-vinylbenzotriazoles: formation of N-phenylketenimines

A real-time analysis of the flash-vacuum pyrolysis products of 1-vinyl-, 1-(2-methylprop-1-enyl)-, and 1-styryl-benzotriazole (3), (16), and (18) has been performed by tandem mass spectrometry. In the 500–700 °C temperature range, these compounds lose nitrogen yielding the N-phenylketenimines (14), (17), and (19), respectively. At higher pyrolysis temperatures (3) gives indole (4)via isomerization of (14), whereas from (16) the secondary products of (17) are benzene and methacrylonitrile. In a preparative pyrolysis of (18) at 800 °C 2- and 3-phenylindole (9) and (10) respectively, have also been detected.