[NH2:1][C:2]1[C:3]([F:11])=[C:4]([CH:8]=[CH:9][CH:10]=1)[C:5]([OH:7])=[O:6].S(=O)(=O)(O)O.[CH3:17]O>>[CH3:17][O:6][C:5](=[O:7])[C:4]1[CH:8]=[CH:9][CH:10]=[C:2]([NH2:1])[C:3]=1[F:11]In a round bottom flask, 3-amino-2-fluoro-benzoic acid (71, 2.51 g, 16.2 mmol) is dissolved in 100 mL of methanol and 1 mL of concentrated sulfuric acid is added. The reaction is heated to reflux for 24 hours and an additional 1 mL of concentrated sulfuric acid is added. The reaction is heated to reflux another 20 hours, then extracted with ethyl acetate and saturated aqueous sodium chloride. The organic layer is isolated and washed with water, sodium bicarbonate, and brine, then dried with magnesium sulfate, and filtered. The filtrate is concentrated under vacuum to provide the desired compound (72, 2.688 g).
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