1,2,4-Triazole is one of a pair of isomeric chemical compounds with molecular formula C2H3N3, called triazoles, which have a five-membered ring of two carbon atoms and three nitrogen atoms. 1,2,4-Triazole is a basic aromatic heterocycle. 1,2,4-Triazole derivatives find use in a wide variety of applications, most notably as antifungals such as fluconazole and itraconazole.
1,2,4-Triazoles can be prepared using the Einhorn–Brunner reaction or the Pellizzari reaction.
Unsubstituted 1,2,4-triazole can be prepared from thiosemicarbazide by acyation with formic acid and subsequent cyclization of 1-formyl-3-thiosemicarbazide into 1,2,4-triazole-3(5)-thiol; oxydation of thiol by nitric acid yelds 1,2,4-triazole.
The ring structure appears in certain N-heterocyclic carbenes.