The general procedure for the synthesis of 3-fluoro-4-methoxybenzenesulfonyl chloride from 2-fluoroanisole was as follows: 2-fluoroanisole (33.7 mL, 301 mmol) was dissolved in chloroform (250 mL), stirred and cooled to 0 °C. Subsequently, chlorosulfonic acid (50.0 mL, 752 mmol) was slowly added dropwise. After the dropwise addition, the reaction mixture was stirred at room temperature for 14 hours. After completion of the reaction, the mixture was poured into ice water (700 mL) and the aqueous phase was extracted with chloroform (2 x 200 mL). The organic phases were combined, dried with anhydrous sodium sulfate, filtered and concentrated to afford 3-fluoro-4-methoxybenzenesulfonyl chloride as a white fine solid (58.6 g, 87% yield) with a melting point of 80°C. 1H NMR (400 MHz, DMSO-d6) δ: 7.32 (m, 1H), 7.25 (dd, J = 11.5, 2.0 Hz, 1H), 7.05 (t, J = 8.5 Hz, 2.0 Hz, 1H). J = 8.5 Hz, 1H), 3.78 (s, 3H).
