[H-].[Na+].[CH3:3][O:4][C:5](=[O:17])[C:6]1[CH:11]=[C:10](F)[C:9]([N+:13]([O-:15])=[O:14])=[CH:8][C:7]=1[F:16].[CH3:18][OH:19]>>[CH3:3][O:4][C:5](=[O:17])[C:6]1[CH:11]=[C:10]([O:19][CH3:18])[C:9]([N+:13]([O-:15])=[O:14])=[CH:8][C:7]=1[F:16]To a mixture 0.30 g (7.55 mmole) of sodium hydride (60% in mineral oil) and 30 mL of methanol was added 1.49 g (6.86 mmole) of 2,5-difluoro-4-nitro-benzoic acid methyl ester. The mixture was heated at reflux for 18 hours and then quenched by the addition of water, and then concentrated under reduced pressure. The residue was diluted with ethyl acetate, washed with brine, dried over anhydrous magnesium sulfate, filtered and concentrated under reduced pressure. The residue was purified by silica gel chromatography eluting with dichloromethane-hexanes (1:1) to give 0.92 g of 2-fluoro-5-methoxy-4-nitro-benzoic acid methyl ester.
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