Potassium Hydroxide → [3-Bromo-4-(cyclopropylsulfanyl)phenyl]acetic acid

To hydrazine monohydrate (16.9 mL) was added [3-bromo-4-(cyclopropylsulfanyl)phenyl](oxo)acetic acid (15 g) under ice-cooling, followed by stirring at 80° C. for 10 minutes. To the reaction mixture was added potassium hydroxide (8.22 g), followed by stirring at 80° C. for 20 minutes and then stirring at 100° C. overnight. After leaving it to be cooled at room temperature, concentrated hydrochloric acid (50 mL) was added thereto under ice-cooling, followed by extraction with chloroform (50 mL×3). The organic layer was sequentially washed with 1 M hydrochloric acid (50 mL×2) and saturated brine (50 mL), and dried over anhydrous magnesium sulfate, and the solvent was then evaporated under reduced pressure to obtain [3-bromo-4-(cyclopropylsulfanyl)phenyl]acetic acid (13.5 g) as a pale yellow solid.