[S:1]1[CH:5]=[CH:4][CH:3]=[C:2]1[CH2:6][C:7]([O:9][CH3:10])=[O:8].[Al+3].[Cl-].[Cl-].[Cl-].[Br:15]Br.O>C(Cl)(Cl)Cl>[Br:15][C:4]1[CH:3]=[C:2]([CH2:6][C:7]([O:9][CH3:10])=[O:8])[S:1][CH:5]=1To a solution of methyl 2-(thiophen-2-yl)acetate (5 g, 32 m mol) and anhydrous AlCl3 (10.7 g, 80 mmol) in CHCl3 (50 ml) was added dropwise bromine (1.8 ml, 34 mmol) at 0˜5° C. over 30 min. When the addition was complete, the mixture was allowed to warm to room temperature overnight. Then it was poured into icy water (50 ml), extracted with EtOAc (30 ml×3). The combined organic phase was dried over Na2SO4, filtered and concentrated. Purification by column chromatography (PE/EtOAc=10/1) gave the product (3.1 g, 41%) as light yellow oil.
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