2,4-Dichlorobenzoyl chloride → [(2,4-Dichlorobenzoyl)amino]thiourea

Thiosemicarbazide hydrochloride (2.55 g, 20.0 mmol) was mixed to pyridine (20 ml), and 2,4-dichlorobenzoyl chloride (2.81 ml) was added thereto. The mixture was stirred at a room temperature for 14 hours. The solvent was distilled off. Water was added to the resulting residue, and the mixture was stirred. The precipitate was separated by filtration. 2,4-Dichlorobenzoylthiosemicarbazide (2.11 g, 8.00 mmol) obtained from the precipitate by through circulation drying was mixed to toluene (25 ml), and methanesulfonic acid (0.78 ml) was added to the mixture. The resulting mixture was heated and stirred for 6 hours. The mixture was allowed to cool to a room temperature. Then, the precipitate was separated by filtration, neutralized with water and 25% ammonia water, and stirred for 30 minutes. The precipitate was separated by filtration, washed with water, and subjected to through circulation drying to give the title compound (1.14 g, 58%) as a white substance.