Differentiation between isomeric structures of benzazoles by 14N, 13C and 1H NMR

Nitrogen chemical shifts constitute an effective means of distinguishing between isomeric benzazole ring systems. There is a large difference in nitrogen shielding, usually more than 20 ppm, between isomeric benzenoid‐ and quinonoid‐like structures. 13C and 1H NMR is shown to provide unambiguous structure assignment only in cases of symmetric quinonoid ring systems of azoles.