The reaction between 1,2,3-thiadiazoles, unsubstituted in the 5-position, and a strong base such as an organolithium compound, sodamide, sodium methylsulfinyl carbanion, or potassium t-butoxide results in cleavage of the thiadiazole ring system with evolution of nitrogen and formation of alkalimetal alkynethiolate. Subsequent addition of an alkyl or acyl halide to the reaction mixture produces 1-alkynyl thioethers. 4-(5-Phenyl-1,2,3-thiadiazolyl)lithium, obtained from 5-phenyl-1,2,3-thiadiazole and methyl-or phenyllithium, reacts with methyl iodide to give 4-methyl-5-phenyl-1,2,3-thiadiazole.