A MULTINUCLEAR MAGNETIC-RESONANCE STUDY OF SOME MESOIONIC OXATRIAZOLES CONTAINING NITROGENOUS EXOCYCLIC GROUPS

H-1, C-13, N-14 and N-15 NMR measurements are reported for four mesoio nic 1-oxa-2,3,4-triazoles containing exocyclic nitrogenous groups. The NMR signal assignments are discussed and compared with those previous ly published for some corresponding oxatriazoles. The results obtained support the proposed cyclic mesoionic structures for the compounds st udied. The questions of possible charge delocalisation and valence tau tomerism are discussed. Compound with N-H as an exocyclic group (Fig. 1) is found to be relatively unstable, this is attributed to proton mi gration in the corresponding noncyclic form of this molecule.