[NH2:1][C:2]1[CH:10]=[C:9]([Br:11])[CH:8]=[C:7]([Br:12])[C:3]=1[C:4]([OH:6])=[O:5].[N+](=[CH2:15])=[N-].C(O)(=O)C>CCOCC.C(OCC)(=O)C>[CH3:15][O:5][C:4](=[O:6])[C:3]1[C:7]([Br:12])=[CH:8][C:9]([Br:11])=[CH:10][C:2]=1[NH2:1]To a solution of 2-amino-4,6-dibromo-benzoic acid (17.5 g, 59.3 mmol) in ether (150 mL) and ethyl acetate (15 mL) kept in an ice bath was added a solution of diazomethane (approximately 70.0 mmol, prepared from diazald 118.6 mmol) in ether (500 mL) over 1 hour. The reaction mixture was then stirred in an ice water bath for 2 hours. The resultant was treated with acetic acid 10 mL and washed with 2N NaHCO3 and brine. The organic layer was concentrated in vacuo. The residue was purified by chromatography (hexane:EtOAc=8:1) to give the objective compound (15.3 g, 83%) as brown solid: 1H NMR (200 MHz, CDCl3) δ 3.92 (s, 3H), 4.92 (br s, 2H), 6.80 (d, J=7.73, 2H), 7.11 (d, J=7.73, 1H); MS(EI) m/e 307 [M+].
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