To a cold (0° C.) suspension of N-(4′-amino-2′-chloro-6′-(trifluoromethyl)biphenyl-3-yl)methanesulfonamide (570 mg, 1.56 mmol, Eq: 1.00) and calcium carbonate (313 mg, 3.13 mmol, Eq: 2) in dichloromethane (3.38 ml) and water (3.38 ml) was added thiophosgene (198 mg, 131 μl, 1.72 mmol, Eq: 1.1). The reaction mixture was allowed to warm up to room temperature and was vigorously stirred for 16 h. 1N HCl was added to adjust the pH to ca. 2. The reaction mixture was partitioned between water and ethyl acetate. The organic layer was separated and washed with water then brine and purified on silica gel (column 24 g, dichloromethane/ethyl acetate 1:0 to 85:15) to give 565 mg (89%) of the desired product as a colorless oil.
