C([O:4][C:5]1[C:13]2[S:12][C:11]([CH3:14])=[CH:10][C:9]=2[CH:8]=[C:7]([C:15]([O:17][CH2:18][CH3:19])=[O:16])[CH:6]=1)(=O)C.C(=O)([O-])[O-].[K+].[K+]>C(O)C.ClCCl>[OH:4][C:5]1[C:13]2[S:12][C:11]([CH3:14])=[CH:10][C:9]=2[CH:8]=[C:7]([C:15]([O:17][CH2:18][CH3:19])=[O:16])[CH:6]=1Ethyl 7-(acetyloxy)-2-methyl-1-benzothiophene-5-carboxylate was dissolved in absolute ethanol (500 mL). Potassium carbonate (18 g, 0.13 mol) was added. The reaction mixture was stirred for 3 h at 60° C. and diluted with 200 mL of dichloromethane. The suspension was filtered. The precipitate was washed by 100 mL of dichloromethane. The combined solutions were washed by 200 mL of a 10% aqueous solution of citric acid and evaporated in vacuum to dryness. The residue was crystallized from ether/hexane mixture (1:5) to give the desired product 10 g (42 mmol, 84%) as a cream solid. 1H NMR (DMSO-d6): δ ppm 1.30 (t, 3H), 2.50 (s, 3H), 4.30 (qt, 2H), 7.20 (s, 1H), 7.95(s, 1H), 7.85 (s, 1H); MS(APCl, pos): 237.1.
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