To a solution of 5-bromo-N-(4-fluoro-2-aminophenyl)-2-methoxybenzenesulfonamide (0.1 mmol) in pyridine (0.5 mL) and DCM (2 mL), 4-chlorobenzenesulfonyl chloride (0.12 mmol) was added. The reaction mixture was stirred at room temperature for 4 h and then diluted with ethyl acetate (10 mL). The contents were washed with 10% aqueous HCl (10 mL) and brine (10 mL), dried over sodium sulfate, and concentrated under vacuum. The residue obtained was purified by column chromatography eluting with hexanes/ethyl acetate (1:1) followed by ethyl acetate to give 43 mg of 5-bromo-N-[2-(4-chlorobenzenesulfonylamino) -4-fluorophenyl]-2-methoxybenzenesulfonamide. LC: Tr 1.10 min, MS: 551.8 (M+1)+
