Halogeno-o-phenylenediamines and derived heterocycles. Part II. Hydrodechlorination of chloroquinoxalines

Abstract

Treatment of 5,6,8-trichloro-7-methylquinoxaline (II) with alkali in aqueous ethanol gives 5,8-dichloro-6-methyl-quinoxaline (III) cleanly in good yield. 5,6,7,8-Tetrachloroquinoxaline similarly, though less satisfactorily, yields 5,6,8-trichloroquinoxaline and 5,8-dichloroquinoxaline. Further experiments with a bearing on the course of these reactions are described and a possible mechanism is discussed.

The preparation of 5,8-dichloro-6-ethoxy-7-methylquinoxaline (XV; R = Et), a possible product from the reaction (II)→(III), and unambiguous syntheses of (III) and 5,7-dichloro-6-methylquinoxaline (VI) are described.

I.r. and ¹H n.m.r. data for several quinoxalines and their intermediates are also given.