134-11-2

200575-16-2

Example 1 Preparation of 5-chlorosulfonyl-2-ethoxybenzoic acid (II): in a 250 mL three-neck flask, 2-ethoxybenzoic acid (50 g, 0.30 mol) was slowly added dropwise to ice-bath cooled dichlorosulfoxide (22 mL). Under stirring conditions, dichlorosulfoxide (0.30 mol) and chlorosulfonic acid (82.6 mL, 1.24 mol) were added sequentially. The temperature of the reaction mixture needed to be strictly controlled not to exceed 25 °C during the reaction. After the reaction mixture was stirred continuously for 18 h at room temperature, it was slowly poured into ice water with stirring, at which time a white precipitate was generated. The reaction mixture was continued to be stirred for 1 h. Subsequently, filtration was carried out, the precipitate was washed with water, and finally dried under vacuum to give 64.4 g of the crude product (II) as a white solid in 81% yield with a melting point of 108-110 °C.