The oxidation of N-(2-Pyridyl)thioureas. The synthesis of [1,2,4]Thiadiazolo-[2,3-a]pyridinium salts

Abstract

The oxidation of N-(2-pyridyl)thioureas with bromine or sulphuryl chloride in inert solvents gives [1,2,4]thiadiazolo[2,3-alpyridinium salts (5). Similar products are obtained by the oxidation of N-(2-pyridyl)thioamides and N-(2-pyridyl)dithio-carbamates. The structure of this new ring system has been established by reduction to the parent thiourea or thioamide by hydrazine, by hydrolytic degradation, and by analytical and molecular weight evidence. 2-Phenylamino-substituted [1,2,4]- thiazolo[2,3-alpyridinium salts undergo a rapid rearrangement on basification or in one instance on being heated to give the isomeric 2-(2'-pyridylamino)benzothiazoles.