[Cl:1]N1C(=O)CCC1=O.[CH2:9]([O:11][C:12]([C:14]1[CH:18]=[C:17]([CH2:19][CH3:20])[S:16][CH:15]=1)=[O:13])[CH3:10]>C(O)(=O)C>[CH2:9]([O:11][C:12]([C:14]1[CH:18]=[C:17]([CH2:19][CH3:20])[S:16][C:15]=1[Cl:1])=[O:13])[CH3:10]N-Chlorosuccinimide (0.8 g, 5.9 mmol) was added to a solution of 5-ethyl-thiophene-3-carboxylic acid ethyl ester (1 g, 5.43 mmol) in acetic acid (10 mL) and stirred overnight. The reaction was filtered and the solvent removed under vacuum. The product was purified by flash chromatography on silica, eluting with 0%-100% t-butylmethyl ether in cyclohexane. The fractions containing the desired product were concentrated under vacuum to give the title compound (0.83 g). 1H NMR (400 MHz, CHCl3-d): δ 7.05 (s, 1H), 4.3 (q, 2H), 2.75 (q, 2H), 1.4 (t, 3H), 1.3 (t, 3H).
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