A comparison of some pyrolysis reactions of benzotriazoles, benzisoxazolones and benzisothiazolones

Formation of Cumulenes, Triple-Bonded, and Related Compounds by Flash Vacuum Thermolysis of Five-Membered Heterocycles

“…[29] The latter compound is also obtained in over 90% yield by FVT of the benzisoxazole 35. [30] There was no mention of ring-contraction products in this work. The formation of benzoxazole is analogous to the formation of furans from 1-acylpyrazoles, described in Section 4.…”

“…[61] 1-Methylbenzotriazole also loses N 2 to produce N-phenylmethanimine, [30,61] which trimerizes. This trimer is also formed on FVT of 1-methylbenzisoxazole.…”

“…This trimer is also formed on FVT of 1-methylbenzisoxazole. [30] 1-Phenylbenzotriazole undergoes loss of N 2 and quantitative cyclization to carbazole. [62,63] 1-(2-Pyridyl)benzotriazole likewise affords pyrido[1,2-a]-benzimidazole.…”

“…[62,63] 1-(2-Pyridyl)benzotriazole likewise affords pyrido[1,2-a]-benzimidazole. [30] Other aspects of triazole chemistry are described in Sections 2, 4, and 9.…”

Pyrolysis of benzotriazoles. Relationships between 1- and 2-vinylbenzotriazoles, α- and β-azidostyrenes, N-phenylketenimine and indole. Pitfalls in the use of pyrolysis-mass spectrometry in mechanistic studies

“…More recently, there have been several investigations of pyrolyses of variously substituted benzotriazoles, especially by the groups of Moyano [2] [3], Al-Awadi [4][5] [6] and Prager [7] [8]. The flash vacuum pyrolysis (FVP) of benzotriazole itself constitutes an excellent synthetic route to 1-cyanocyclopentadiene in essentially quantitative yield [9].…”