Tautomerism of derivatives of azines. 16. Tautomerism of acylmethylpyrazines and -quinoxalines

The tautomeric equilibria of acylmethylpyrazines and -quinoxalines in chloroform were studied by ¹H, ¹⁴N, and ¹⁷O NMR spectroscopy. It was shown that keto-enol tautomerism is realized in the acylmethylpyrazine series. Annelation leads to the development of an ylidene tautomer in the acylmethylquinoxaline series. A marked dependence of the position of the intrachelate equilibrium on the character of the solvent was observed.See [1] for Communication 15.Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1663–1667, December, 1987.