[Br:1][C:2]1[S:6][C:5]([C:7]([O:9]C)=O)=[C:4]([N:11]([CH3:20])[C:12](=[O:19])[CH2:13][C:14]([O:16][CH2:17][CH3:18])=[O:15])[C:3]=1[CH3:21].BrC1SC(C(OC)=O)=C(NC)C=1C.CCN(C(C)C)C(C)C.ClC(=O)CC(OCC)=O>CN(C)C1C=CN=CC=1.CN(C=O)C.CCOC(C)=O>[Br:1][C:2]1[S:6][C:5]2[C:7]([OH:9])=[C:13]([C:14]([O:16][CH2:17][CH3:18])=[O:15])[C:12](=[O:19])[N:11]([CH3:20])[C:4]=2[C:3]=1[CH3:21]Methyl 5-bromo-3-(3-ethoxy-N-methyl-3-oxopropanamido)-4-methylthiophene-2-carboxylate. A solution of methyl 5-bromo-4-methyl-3-(methylamino)thiophene-2-carboxylate (0.28 g, 1.1 mmol), DIEA (0.22 mL, 1.3 mmol), N,N-dimethylpyridin-4-amine (0.020 g, 0.16 mmol) in DMF (4 mL) was treated at room temperature with ethyl 3-chloro-3-oxopropanoate (0.16 mL, 1.3 mmol) and stirred for 18 hours. The mixture was diluted with EtOAc, washed with water, brine, dried over MgSO4, and evaporated. The residue was purified by flash chromatography using EtOAc/hexanes to give the title compound. MS (ESI) m/z: Calculated 378.2; Observed; 379.0. 1H NMR (300 MHz, CDCl3) δ ppm 4.12-4.11 (2H, m), 3.86 (3H, s), 3.16 (3H, s), 3.12 (2H, s), 2.10 (3H, s), 1.23 (3H, t, J=7.1 Hz).
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