A N-15 NMR investigation of a series of benzotriazinones and related antitumour heterocycles
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A series of 3-substituted 1,2,3-benzotriazin-4-ones, 1 and 2, were synthesized by standard methods and the N-15 NMR spectra were recorded. All spectra were obtained using the natural abundance of the nitrogen-15 isotope. The chemical shifts appear in the normal range for N-1, N-2 and N-3 of the triazine ring, and also correlate with the chemical shifts in the spectra of the imidazolotriazinone, 4, and the imidazolotetrazinone, 5. Significantly, the spectra of la, 2 and 4, recorded with full NOE, show inversion of the singlet assigned to N-3, demonstrating that these compounds exist in the tautomeric form shown. The structure of the 4-iminobenzotriazinone (3) was confirmed by this N-15 NMR analysis. The spectrum shows a signal for the NH-bearing imino-nitrogen atom, which is an inverted singlet in the NOE spectrum, whereas the signal from the N-3 atom of 3 is not inverted in the NOE spectrum. Copyright (C) 2002 John Wiley Sons, Ltd.
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MAGNETIC RESONANCE IN CHEMISTRY, 2002, 40 pp. 300 - 302