Add 6.90 g (0.05 mol) of p-nitrotoluene to a 100 mL three-necked flask, slowly add 17.5 g (0.15 mol) of chlorosulfonic acid dropwise with vigorous stirring, and after dropping, warm up the reaction to 65C for 24 h. After the reaction, the reaction solution was slowly poured into 100 mL of iced water, and then extracted with dichloromethane (100 mL2), and the organic layers were combined to obtain 2-methyl-5-nitrobenzenesulfonyl chloride. The organic layer was extracted with dichloromethane (100 mL2).
