[Br:1][C:2]1[C:3]([N+:23]([O-])=O)=[CH:4][C:5]2[O:9][C:8]([C:10]3[CH:15]=[CH:14][C:13]([F:16])=[CH:12][CH:11]=3)=[C:7]([C:17]([O:19][CH2:20][CH3:21])=[O:18])[C:6]=2[CH:22]=1.[NH4+].[Cl-]>CO.C1COCC1.O.[Fe]>[NH2:23][C:3]1[C:2]([Br:1])=[CH:22][C:6]2[C:7]([C:17]([O:19][CH2:20][CH3:21])=[O:18])=[C:8]([C:10]3[CH:11]=[CH:12][C:13]([F:16])=[CH:14][CH:15]=3)[O:9][C:5]=2[CH:4]=1A mixture of ethyl 5-bromo-2-(4-fluorophenyl)-6-nitrobenzofuran-3-carboxylate (52 g, 127 mmol), iron filings (21.3 g, 382.2 mmol) and NH4Cl (41 g, 764.4 mmol) in MeOH/THF/H2O (2/2/1, 500 mL) was stirred at reflux for 3 hour. After filtered and concentrated, the resulting residue was purified using column chromatography (petroleum ether/EtOAc/dichloromethane=20:1:20) to provide ethyl 6-amino-5-bromo-2-(4-fluorophenyl)benzofuran-3-carboxylate (40 g, yield: 82%). 1H-NMR (CDCl3, 400 MHz) δ 8.01 (s, 1H), 7.94˜7.98 (m, 2H), 7.08 (t, J=8.0 Hz, 2H), 6.83 (s, 1H), 4.32˜4.36 (m, 2H), 4.18 (s, 2H), 1.35 (t, J=8.0 Hz, 3H). MS (M+H)+: 378/380.
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