General procedure for the synthesis of 2-chloro-4-methylsulfonylbenzoic acid from compound (CAS:101349-95-5): acetonitrile (4 mL) and compound 5 (100 mg, 0.46 mmol) were added to a 10 mL three-necked flask and stirred until complete dissolution. After cooling the reaction mixture to 0 °C, an aqueous solution of NaClO2 (124 mg, 1.38 mmol) was slowly added. Subsequently, 1 mL of HCl (117 μL) was added and stirred for 0.5 h at 0 °C. The reaction system was warmed up to 80 °C and stirring was continued for 0.5 hours. The reaction progress was monitored by thin layer chromatography (TLC). After completion of the reaction, the mixture was cooled to room temperature. The reaction mixture was dried with acetonitrile, the pH was adjusted to 2 with 1N HCl aqueous solution and then the organic phase was separated by extraction with ethyl acetate and water. The organic phase was dried with anhydrous Na2SO4 and concentrated under reduced pressure to remove the organic solvent to give the crude product. The crude product was purified by column chromatography using petroleum ether and ethyl acetate (1:1, v/v) as eluents, and concentrated under reduced pressure (5 torr) to give compound 32 as a white solid (50 mg, 46.6% yield).
