Multinuclear magnetic resonance study of some mesoionic oxatriazoles containing nitrogenous exocyclic groups |
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Authors: | Wojciech Bocian Jaros?aw Ja?wínski Lech Stefaniak Graham A Webb |
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Institution: | (1) Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland;(2) Department of Chemistry, University of Surrey, Guildford, GU2 5XH Surrey, UK |
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Abstract: | 1H,13C,14N and15N NMR measurements are reported for four mesoionic 1-oxa-2, 3, 4-triazoles containing exocyclic nitrogenous groups. The NMR signal assignments are discussed and compared with those previously published for some corresponding oxatriazoles. The results obtained support the proposed cyclic mesoionic structures for the compounds studied. The questions of possible charge delocalization and valence tautomerism are addressed. Compound with N– H as a exocyclic group (Fig. 1) is found to be relatively unstable, this is attributed to proton migration in the corresponding non-cyclic form of this molecule.Published in Khimiya Geterotsikiicheskikh Soedinenii, No. 9, pp. 1260–1263, September, 1995. |
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Keywords: | 1H 13C 14N and15N NMR chemical shifts line widths mesoionic oxatriazoles charge localization valence tautomerism |
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