[Br:1][C:2]1[C:3]([N:23]2[CH2:27][CH2:26][CH2:25][C:24]2=[O:28])=[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]CC)=[O:18])[C:6]=2[CH:22]=1.[Li+].[OH-]>O1CCOCC1.O>[Br:1][C:2]1[C:3]([N:23]2[CH2:27][CH2:26][CH2:25][C:24]2=[O:28])=[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]([OH:19])=[O:18])[C:6]=2[CH:22]=1A solution of ethyl 5-bromo-2-(4-fluorophenyl)-6-(2-oxopyrrolidin-1-yl)benzofuran-3-carboxylate (2.5 g, 5.8 mmol) and LiOH (0.5 g, 21.0 mmol) in dioxane (30 mL) and water (10 mL) was allowed to stir at 90° C. for 1 hour. The mixture was cooled to room temperature and extracted with dichloromethane, the organic extract was washed with brine, dried over Na2SO4 and concentrated to provide 5-bromo-2-(4-fluorophenyl)-6-(2-oxopyrrolidin-1-yl)benzofuran-3-carboxylic acid (2.2 g, yield: 91%). 1H-NMR (CDCl3, 400 MHz) δ 8.08 (s, 1H), 7.81˜7.84 (m, 2H), 7.34 (s, 1H), 6.89˜6.93 (m, 2H), 3.79˜3.82 (m, 2H), 2.66˜2.70 (m, 2H), 2.26˜2.31 (m, 2H). MS (M+H)+: 418/420.
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