The general procedure for the synthesis of 5-fluoro-2-methoxybenzenesulfonyl chloride from 4-fluoroanisole was as follows: 1-fluoro-4-methoxybenzene (10.0 g, 0.079 mol) was slowly added dropwise to sulfuryl chloride (31.4 ml, 0.474 mol) at 0 °C. The reaction mixture was stirred at room temperature for 6 h, followed by slow dropwise addition to ice water for quenching. The mixture was extracted three times with dichloromethane (CH2Cl2). The organic phases were combined, washed with saturated brine, dried over anhydrous sodium sulfate and concentrated under reduced pressure to afford the target product 5-fluoro-2-methoxybenzenesulfonyl chloride (15.0 g, 84.6% yield). The product was characterized by 1H NMR (300 MHz, DMSO-d6): δ 3.74 (s, 3H), 6.97 (dd, J = 4.3, 8.9 Hz, 1H), 7.13 (dt, J = 3.4, 8.6 Hz, 1H), 7.41 (dd, J = 3.3, 8.8 Hz, 1H).
