Sodium Thiosulfate → 6-(2-Ethylsulfonylphenyl)-2-trifluoromethylimidazo[1,2-a]pyridine

220 mg of 3-chloroperbenzoic acid (purity of 65% or more) was added to a mixture of 134 mg of 6-(2-ethylsulfanylphenyl)-2-trifluoromethylimidazo[1,2-a]pyridine and 4 ml of chloroform, under ice cooling, and the mixture was stirred at room temperature for 4 hours. A 10% aqueous sodium thiosulfate solution was added to the reaction mixture, and the mixture was extracted with chloroform. The organic layer was washed with a saturated aqueous sodium bicarbonate solution and dried over anhydrous magnesium sulfate, and then concentrated under reduced pressure. 93 mg of 6-(2-ethylsulfonylphenyl)-2-trifluoromethylimidazo[1,2-a]pyridine (Compound of Present Invention 27) was obtained.