NMR spectra of cyclic nitrones. 5. 13C NMR spectra of the potential tautomeric systems of amino-, hydroxy-, and mercaptonitrones in the series of 3-imidazoline 3-oxide

Abstract

The position of the tautomeric equilibrium in amino-, hydroxy, and mercaptonitrones was determined by the 13C NMR method for the case of the derivatives of 3-imidazoline-3-oxide. It was shown that the tautomeric equilibrium in the OH and SH derivatives is shifted toward the oxo and thioxo forms (∼95%). The chemical shifts of the carbon atoms of the nitrone group in the α-N-, α-O-, and α-S-substituted nitrones lie in the region of 137–150 ppm.