[F:1][C:2]1[CH:7]=[CH:6][C:5]([NH:8][CH2:9][C:10](O)=[O:11])=[C:4]([N+:13]([O-])=O)[CH:3]=1>C(O)(=O)C.C(OCC)(=O)C.[Fe]>[F:1][C:2]1[CH:3]=[C:4]2[C:5]([NH:8][CH2:9][C:10](=[O:11])[NH:13]2)=[CH:6][CH:7]=1Iron powder (6.52 g, 116.8 mmol, 5.0 eq) is added at room temperature to a stirred solution of (4-fluoro-2-nitro-phenylamino)-acetic acid (6.85 g, 23.4 mmol, 1.0 eq) in glacial acetic acid (40 mL). The resulting suspension is heated at 90° C. for 3 hours, then cooled to room temperature, diluted with ethyl acetate (40 mL), and filtered through silica gel. The filtrate is concentrated to give a crude that is purified by column chromatography (silica gel, eluent: ethyl acetate:petroleum ether, 1:3, v/v) to afford 7-fluoro-3,4-dihydro-1H-quinoxalin-2-one as a brown solid (4.01 g, 72% yield).
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