ClC1C=CC=C(C(OO)=[O:9])C=1.[CH:12]1([C:15]2[CH:16]=[CH:17][C:18]([C:21]([O:23][CH2:24][CH3:25])=[O:22])=[N:19][CH:20]=2)[CH2:14][CH2:13]1.C(=O)(O)[O-].[Na+].S([O-])([O-])(=O)=S.[Na+].[Na+]>C(Cl)(Cl)Cl>[CH:12]1([C:15]2[CH:20]=[N+:19]([O-:9])[C:18]([C:21]([O:23][CH2:24][CH3:25])=[O:22])=[CH:17][CH:16]=2)[CH2:13][CH2:14]1m-Chloroperbenzoic acid (55 g) was added to a solution of ethyl 5-cyclopropylpyridine-2-carboxylate (15.5 g) in chloroform (300 mL) under ice-cooling, and the mixture was stirred at room temperature for four hours. The reaction solution was poured into a mixed solvent of saturated aqueous sodium bicarbonate and a saturated sodium thiosulfate solution, and the mixture was stirred at room temperature for 30 minutes. After extraction with chloroform, the organic layer was washed with brine, dried over anhydrous magnesium sulfate and filtered. The solvent was then evaporated under reduced pressure. The residue was purified by silica gel column chromatography (chloroform:methanol=10:0→9:1) to give ethyl 5-cyclopropylpyridine-2-carboxylate 1-oxide (15.4 g) as a pale yellow oil.
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