[CH3:1][O:2][C:3]1[C:19]([O:20][CH3:21])=[C:18]([O:22][CH3:23])[CH:17]=[C:16]([CH3:24])[C:4]=1[C:5]([C:7]1[C:12]([O:13][CH3:14])=[CH:11][N:10]=[CH:9][C:8]=1[Cl:15])=[O:6].ClC1C=CC=C(C(OO)=[O:33])C=1.[OH-].[Na+]>C(Cl)(Cl)Cl>[CH3:1][O:2][C:3]1[C:19]([O:20][CH3:21])=[C:18]([O:22][CH3:23])[CH:17]=[C:16]([CH3:24])[C:4]=1[C:5]([C:7]1[C:12]([O:13][CH3:14])=[CH:11][N+:10]([O-:33])=[CH:9][C:8]=1[Cl:15])=[O:6]A chloroform (60 ml) solution of 3.4 g (1 mmol) of 4-(2,3,4-trimethoxy-6-methylbenzoyl)-3-chloro-5-methoxypyridine (compound No. 244) was cooled with ice, 4.1 g (1.6 mmol) of m-chloroperbenzoic acid was added thereto, followed by stirring under cooling with ice for 2 hours, and stirring was further conducted at room temperature for 2 hours. 30 ml of a 0.5 mol/l aqueous sodium hydroxide solution was added to the mixture to terminate the reaction, the organic layer was dried over anhydrous sodium sulfate and subjected to filtration, and the solvent was distilled off under reduced pressure to obtain 3.5 g (yield 85%) of 4-(2,3,4-trimethoxy-6-methylbenzoyl)-3-chloro-5-methoxypyridine-N-oxide (m.p. 160-166° C.).
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