Gas-phase pyrolysis of 4-amino-3-allylthio-1,2,4-triazoles: a new route to [1,3]thiazolo[3,2-b][1,2,4]triazoles

Abstract

Flash vacuum pyrolysis of the 3-allylthio derivatives of 4-amino-4H-1,2,4-triazoles 10–13 and 15–17 at 750–850 °C (10⁻²–10⁻³ Torr) gives [1,3]thiazolo[3,2-b][1,2,4]triazoles 19 and 24–29 in ca. 50% yield. The mechanism is thought to involve initial [3,3]sigmatropic shift of the allyl group, followed by cleavage of the N–N bond to generate a thiaza-allyl radical, which then undergoes cyclisation, rearrangement and alkyl group extrusion.