Oxadiazoles are a class of heterocyclic aromatic chemical compound of the azole family; with the molecular formula C2H2N2O. There are four isomers of oxadiazole:1,2,4-Oxadiazole, 1,2,5-oxadiazole, and 1,3,4-oxadiazole are all known and appear in a variety of pharmaceutical drugs including raltegravir, butalamine, fasiplon, oxolamine, and pleconaril. The 1,2,3-isomer is unstable and ring-opens to form the diazoketone tautomer;[1] however, it does exist within the unusual sydnone motif.