N-Chlorosuccinimide (NCS, 1.778 g, 13.32 mmol) was slowly added to a suspension of 4-(benzylthio)benzonitrile (1 g, 4.44 mmol) dissolved in acetic acid (AcOH, 10 mL) and water (3.5 mL) at 0 °C. The reaction mixture was stirred at room temperature for 2 hours. After completion of the reaction, the reaction mixture was diluted with ethyl acetate (EtOAc), washed sequentially with water and saturated brine, dried over anhydrous sodium sulfate (Na2SO4) and concentrated under reduced pressure. The crude product was purified by silica gel column chromatography using a hexane solution of 15%-20% ethyl acetate as eluent to give a white solid. The resulting solid was washed with hexane and dried under reduced pressure to give 4-cyanobenzenesulfonyl chloride (0.701 g, 3.48 mmol, 78% yield) as a white solid. The structure of the product was confirmed by 1H NMR (300 MHz, CDCl3): δ 7.91-7.97 (2H, m), 8.15-8.21 (2H, m).
