[F:1][C:2]1[CH:10]=[CH:9][C:8]([N+:11]([O-])=O)=[CH:7][C:3]=1[C:4]([OH:6])=O.S(Cl)(Cl)=O.[CH:18]([NH2:21])([CH3:20])[CH3:19].[Cl-].[NH4+]>[Zn].O.CO.C(N(CC)CC)C.C1COCC1>[NH2:11][C:8]1[CH:9]=[CH:10][C:2]([F:1])=[C:3]([CH:7]=1)[C:4]([NH:21][CH:18]([CH3:20])[CH3:19])=[O:6]
A mixture of 2-fluoro-5-nitrobenzoic acid (600 mg) and thionyl chloride (2 mL) was heated under reflux for 15 hours. The reaction liquid was concentrated under reduced pressure, followed by an azeotropic process with toluene to give a yellow crystal. To a mixture of the yellow crystal and THF (11 mL), triethylamine (0.47 mL) and isopropylamine (0.29 mL) were added under ice cooling and stirred at room temperature for 5 hours. The reaction liquid was poured into water and extracted with ethyl acetate. The organic layer was washed with saturated aqueous sodium chloride and then dried over anhydrous sodium sulfate, and the solvent was distilled off under reduced pressure to give a yellow crystal. To a mixture of the yellow crystal (723 mg) and methanol (8 mL) and water (3 mL), ammonium chloride (2.05 g) and zinc powder (2.09 g) were added, and the mixture was heated under reflux for 3 hours. After filtration of the reaction suspension through celite, the filtrate was concentrated under reduced pressure. The residue was poured into saturated aqueous sodium hydrogen carbonate and extracted with ethyl acetate. The organic layer was washed with saturated aqueous sodium chloride and then dried over anhydrous sodium sulfate, and the solvent was distilled off under reduced pressure. The residue was purified by silica gel column chromatography (eluent; chloroform:methanol) to give 5-amino-2-fluoro-N-isopropylbenzamide (527 mg) as a light brown crystal.
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