Relative stabilities of the tautomeric forms of conjugate acids and kinetics of deuterium exchange in derivatives of indolizine,pyrrolo [1,2-a] imidazole,and pyrrolo [1,2-a]benzimidazole

The effect of the temperature and the acidicity of the medium on the ratio of the two tautomeric forms of the conjugate acids of derivatives of indolizine, pyrrolo1,2-a]imidazole, and pyrrolo1,2-a]benzimidazole was investigated by PMR spectroscopy. The change in the ratio of the forms with time was studied under fixed reaction conditions. The position of the tautomeric equilibrium in a number of the investigated systems was established. A correspondence between the relative stabilities of the protonated forms and the rate constants for electrophilic deuterium exchange in the neutral molecules was observed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 70–75, January, 1976.