[Br:1][C:2]1[S:6][C:5]([Cl:7])=[C:4]([CH2:8][C:9]2[CH:14]=[CH:13][C:12]([O:15]C)=[CH:11][CH:10]=2)[CH:3]=1.B(Br)(Br)Br.Cl.O>C(Cl)Cl>[Br:1][C:2]1[S:6][C:5]([Cl:7])=[C:4]([CH2:8][C:9]2[CH:14]=[CH:13][C:12]([OH:15])=[CH:11][CH:10]=2)[CH:3]=1To a solution of thiophene 3 (5.44 g, 17.1 mmol) in CH2Cl2 (50 mL) was added boron tribromide (20 mL, 1M in CH2Cl2) at 0° C. The mixture was warmed up to room temperature slowly and stirred at room temperature for 3 hours. To the mixture was added aq. 1N HCl solution (35 mL) dropwise at 0° C. and H2O was added to the mixture. The mixture was extracted with EtOAc (50 mL×2). The combined organic layer was dried over MgSO4, filtered, and concentrated in vacuo. The crude product 4 was dried under high vacuum and used without further purification. (5.1 g, 99%)
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