[F:1][C:2]1[CH:3]=[CH:4][C:5]([N+:15]([O-])=O)=[C:6]([CH:14]=1)[O:7][CH2:8][C:9](OCC)=[O:10]>C(O)(=O)C.C(OCC)(=O)C.[Fe]>[F:1][C:2]1[CH:3]=[CH:4][C:5]2[NH:15][C:9](=[O:10])[CH2:8][O:7][C:6]=2[CH:14]=1Iron powder (36.42 g) was suspended in 5% aqueous acetic acid (69 ml) and heated to 80° C. To the suspension, a solution of ethyl 5-fluoro-2-nitrophenoxyacetate (15.86 g) in acetic acid (65 ml) and ethyl acetate (65 ml) was dropwise added, and the resultant mixture was heated at 60° to 80° C. under reflux for 3 hours. After removal of residue by filtration, the filtrate was extracted with ethyl acetate. The extract was washed with water and sodium bicarbonate solution, dried and concentrated to give 7-fluoro-2H-1,4-benzoxazin-3(4H)-one (6.82 g). m.p., 186.720 C. 1H-NMR (CDCl3 +DMSO-D6) δ ppm: 4.2 (1H, broad), 4.51 (2H, s), 6.5-7.0 (3H, m).
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