General procedure for the synthesis of 3-cyanobenzenesulfonyl chloride from 3-aminobenzonitrile: 3-aminobenzonitrile (2.5 g, 21 mmol) was dissolved in concentrated hydrochloric acid. The mixture of hydrochloric acid (20 mL) and water (20 mL) was cooled to 0 °C and a solution of sodium nitrite (1.5 g, 22 mmol) in water (5 mL) was added slowly and dropwise. The reaction mixture was stirred at 0 °C for 10 min to ensure complete formation of the diazonium salt. In another flask, copper (I) chloride (0.2 g) was added to a solution of acetic acid (25 mL) pre-saturated with sulfur dioxide and stirred at 0°C for 10 minutes. This solution was slowly added dropwise to the above diazonium salt solution, kept at 0°C and stirred for 1 hour. After completion of the reaction, the mixture was poured into ice water and the product was extracted with tert-butyl methyl ether. The organic layers were combined and washed sequentially with water and brine. The crude product was purified by column chromatography (silica gel 60-120 mesh, eluent 5% ethyl acetate in petroleum ether solution) to give pure 3-cyanobenzenesulfonyl chloride (1.9 g, 45% yield) as an off-white solid.1H NMR (300 MHz, CDCl3) δ 8.35 (t, J=1.5 Hz, 1H), 8.31-8.27 (m, 1H), and 8.06-8.02 (m, 1H), 7.82 (t, J=7.9Hz, 1H).
