Trichloromethanesulfenyl chloride → 5-Chloro-3-(propan-2-yl)-1,2,4-thiadiazole

To a mixture of 2-methyl propanimidamide hydrochloride (5.0 g, 40.8 mmol), trichloromethanesulfenyl chloride (7.14 g, 38.4 mmol) in methylene chloride (200 mL) at 0° C. was added dropwise an aqueous solution of sodium hydroxide (50%, 9.9 mL) over 20 minutes. The reaction mixture was stirred for 2 h at 0° C. and then was allowed to warm to room temperature, and stirred for an additional 3 h. Ice was added to the reaction mixture, the mixture was separated, and the aqueous layer was extracted with methylene chloride (3×25 mL). The combined organic extracts were dried over magnesium sulfate, filtered and concentrated under reduced pressure. The resulting residue was purified by medium pressure liquid chromatography (0 to 100% gradient of ethyl acetate in hexanes as eluant) to provide the title compound as a oil (3.8 g).