[NH2:1][C:2]1[C:15]([Br:16])=[CH:14][C:5]2[C:6]([C:9]([O:11]CC)=[O:10])=[CH:7][O:8][C:4]=2[CH:3]=1.O[Li].O.Cl>O1CCOCC1.O>[NH2:1][C:2]1[C:15]([Br:16])=[CH:14][C:5]2[C:6]([C:9]([OH:11])=[O:10])=[CH:7][O:8][C:4]=2[CH:3]=1
To a solution of the compound ethyl 6-amino-5-bromobenzofuran-3-carboxylate (58 g, 204 mmol) in 1,4-dioxane and H2O (850 mL and 150 mL) was added LiOH.H2O (42.8 g, 1.02 mol). The reaction mixture was refluxed for 2 hours, and then 400 mL H2O was added to the reaction mixture. After acidifying to pH 4˜5 with HCl, the resulting solid was filtered to give 6-amino-5-bromobenzofuran-3-carboxylic acid (51 g, yield: 97%). 1H-NMR (400 MHz, DMSO-d6) δ 8.36 (s, 1H), 7.87 (s, 1H), 7.02 (s, 1H), 5.51 (br s, 2H).
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