[Br:1][C:2]1[S:6][C:5]([C:7]([O:9]C)=O)=[C:4]([NH:11][C:12](=[O:17])[C:13](F)(F)F)[C:3]=1[CH3:18].[CH3:19]CN(C(C)C)C(C)C.NC1C(C)=C(Br)SC=1C(OC)=O.[C:40]([O:46][C:47]([C:49](F)(F)F)=O)(C(F)(F)F)=[O:41]>C(Cl)Cl.C(Cl)(Cl)Cl>[Br:1][C:2]1[S:6][C:5]2[C:7]([OH:9])=[C:13]([C:40]([O:46][CH2:47][CH3:49])=[O:41])[C:12](=[O:17])[N:11]([CH3:19])[C:4]=2[C:3]=1[CH3:18]Methyl 5-bromo-4-methyl-3-(2,2,2-trifluoroacetamido)thiophene-2-carboxylate. At 0° C., DIEA (4.32 mL, 24.8 mmol) was added dropwise to a solution of methyl 3-amino-5-bromo-4-methylthiophene-2-carboxylate (6.20 g, 24.8 mmol) in DCM (100 mL), followed by dropwise addition of TFAA (3.45 mL, 24.8 mmol). The mixture was stirred at room temperature for 18 hours, diluted with CHCl3, washed with water, dried over MgSO4, and evaporated. The crude product was purified by flash chromatography using EtOAc/hexanes to give the title compound. MS (ESI) m/z: Calculated; 346.1: Observed; 345.9. 1H NMR (300 MHz, CDCl3) δ ppm 9.62 (1H, br. s.), 3.89 (3H, s), 2.15 (3H, m).
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