Methoxymethyl chloride (1.2 g, 14.3 mmol) was added dropwise to a mixture of N-(2-bromo-5-chloro-pyridin-3-yl)-4-chloro-3-methyl-benzenesulfonamide (5.0 g, 12.7 mmol) and potassium carbonate (3.2 g, 23.2 mmol) in THF (30 mL) at room temperature. After 5 h, the potassium salts were removed by vacuum filtration and the filtrate was concentrated under reduced pressure. The residual light yellow solid was chromatographed on silica gel using ethyl acetate-hexane to provide the N-(2-bromo-5-chloro-pyridin-3-yl)-4-chloro-N-methoxymethyl-3-methyl-benzenesulfonamide as white crystals. MS m/z 441.2 (M+H).
