Intramolecular Heterocyclization of Quinolyl-Substituted Carbothioamides to Functionalized 2,4-Dihydro-3H-1,2,4-triazoles and -1,3,4-thiadiazoles

A simple and economical approach has been proposed for the transformation of 2-(quinolyl­propanoyl)-N-phenylhydrazine-1-carbothioamide into 4-methyl-3-[2-(4-phenyl-5-sulfanylidene-4,5-dihydro-1H-1,2,4-triazol-3-yl)ethyl]quinolin-2(1H)-ones and 3-[2-(5-anilino-1,3,4-thiadiazol-2-yl)ethyl] 4-methylquino­lin-2(1H)-ones by heterocyclization in the presence of aqueous sodium hydroxide and concentrated sulfuric acid, respectively. The reactions are economically efficient, and the target products are formed in high yields (85–98%) under mild conditions without using expensive catalysts and column chromatography for their isolation.