[F:1][C:2]1[CH:3]=[N:4][CH:5]=[CH:6][C:7]=1[C:8]1[O:9][C:10]2[CH:16]=[CH:15][C:14]([C:17]([F:20])([F:19])[F:18])=[CH:13][C:11]=2[N:12]=1.C(Cl)(Cl)Cl.ClC1C=CC=C(C(OO)=[O:33])C=1>C(OCC)(=O)C>[F:1][C:2]1[CH:3]=[N+:4]([O-:33])[CH:5]=[CH:6][C:7]=1[C:8]1[O:9][C:10]2[CH:16]=[CH:15][C:14]([C:17]([F:20])([F:18])[F:19])=[CH:13][C:11]=2[N:12]=1To a mixture of 0.34 g of 2-(3-fluoropyridin-4-yl)-5-(trifluoromethyl)benzoxazole and 6 ml of chloroform, 0.48 g of 65% m-chloroperbenzoic acid was added at room temperature. The solution was stirred while heating at 50° C. for 1.5 hours. The reaction mixture was cooled to room temperature, and diluted with ethyl acetate, and then washed with a saturated aqueous solution of sodium hydrogencarbonate twice and a saturated sodium chloride solution once, sequentially. The organic layer was dried over anhydrous sodium sulfate, and concentrated under reduced pressure. The residue was subjected to silica gel column chromatography to give 0.23 g of 3-fluoro-4-[5-(trifluoromethyl)benzoxazole-2-yl]pyridine N-oxide (hereinafter, referred to as “active compound 26”).
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