Pyrolyse‐Éclair Sous Vide de 1,2,4‐Triazolides = Une Étude par Spectrométrie de Masse en Tandem

A real-time analysis of the flash-vacuum pyrolysis products of some 1,2,4-triazolides has been performed by tandem mass spectrometry. Beside decay products, ketenes and the parent 1,2,4-triazole, 1-acyltriazoles give rise to 5-alkyloxazoles and nitrogen. This ring transformation reaction implies a sigmatropic shift of the acyl group from nitrogen to carbon, loss of nitrogen and cyclisation of the biradical intermediate. 5-aryloxazoles are similarly obtained from 1-aroyltriazoles.