m-Chloroperbenzoic acid → Ethyl 2-chloromethyl-4-(3,4-dimethoxyphenyl)-6,7-dimethoxyquinoline-3-carboxylate 1-oxide

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A mixture of ethyl 2-chloromethyl-4-(3,4-dimethoxyphenyl)-6,7-dimethoxyquinoline-3-carboxylate (3.0 g), m-chloroperbenzoic acid (85%, 2.3 g) and methanol (40 ml) was stirred under reflux for 2 hours. The reaction mixture was concentrated under reduced pressure. The residue was dissolved in chloroform. The chloroform layer was washed with water and dried over magnesium sulfate, and the solvent was evaporated under reduced pressure. The residue was subjected to column chromatography on silica gel. The fractions eluted with chloroform-ethyl acetate (6:4, v/v) gave ethyl 2-chloromethyl-4-(3,4-dimethoxyphenyl)-6,7-dimethoxyquinoline-3-carboxylate 1-oxide (2.0 g, 65%). This was recrystallized from acetone-isopropyl ether. Colorless prisms, mp. 193°-194° C.

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