C([O:3][C:4](=[O:14])[C:5]([C:7]1[S:8][C:9]([Br:13])=[C:10]([Br:12])[CH:11]=1)=[O:6])C.[OH-].[Na+].C(O)(=O)C>O>[Br:12][C:10]1[CH:11]=[C:7]([C:5](=[O:6])[C:4]([OH:14])=[O:3])[S:8][C:9]=1[Br:13](4,5-Dibromothiophen-2-yl)-oxo-acetic acid ethyl ester (1.00 g, 2.92 mmol) was stirred in a mixture of 5 ml water and 1 N NaOH (3.65 ml, 3.65 mmol) at room temperature for 2 hours. The reaction was then poured into 2 N acetic acid, and extracted into 100 ml ethyl acetate. The ethyl acetate layer was dried over Na2SO4 and concentrated under vacuum to provide (4,5-dibromothiophen-2-yl)-oxo-acetic acid (788 mg, 86%). MS (M−H)−: 312.73; 1H NMR (300 MHz, DMSO-d6) δ7.98 (s).
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