Flash‐vacuum pyrolysis of 1‐acylbenzotriazole: Direct observation of cyclopenta‐2,4‐dienylidenemethaneimines by tandem mass spectrometry and low‐temperature infrared spectrometry

Abstract

Abstract A real‐time analysis of the flash‐vacuum pyrolysis products of 1‐acetylbenzotriazole (1) and 1‐benzoylbenzotriazole (2) was performed by tandem mass Spectrometry. In the temperature range 500‐600 °C, these compounds lose nitrogen, yielding N ‐acetyl‐ and N ‐benzoylcyclopenta‐ 2,4‐dienylidenemethaneimines (10 and 17, respectively). At higher pyrolysis temperatures, 1 gives 2‐methylbenzoxazole, cyanocyclopentadiene, methylcyanocyclopentadiene(s), benzonitrile and ketene, which were identified by collision‐activated dissociation mass Spectrometry. Low‐temperature infrared experiments confirmed the pyrolytic transformation 1(2) → 10(17) at mediated temperatures.