[CH2:1]([O:3][C:4]([C:6]1[CH:23]=[CH:22][C:9]2[S:10][C:11]([C:13]3[CH:18]=[CH:17][C:16]([O:19]C)=[CH:15][C:14]=3[CH3:21])=[CH:12][C:8]=2[CH:7]=1)=[O:5])[CH3:2].B(Br)(Br)Br.O.C(Cl)(=O)C>ClCCl.C(OCC)(=O)C>[CH2:1]([O:3][C:4]([C:6]1[CH:23]=[CH:22][C:9]2[S:10][C:11]([C:13]3[CH:18]=[CH:17][C:16]([OH:19])=[CH:15][C:14]=3[CH3:21])=[CH:12][C:8]=2[CH:7]=1)=[O:5])[CH3:2]To a 0° C. solution of 2-(4-Methoxy-2-methyl-phenyl)-benzo[b]thiophene-5-carboxylic acid ethyl ester (1.07 mmol; 350 mg) in anhydrous dichloromethane (4.00 mL) is added a 1 M solution of boron tribromide (1.29 mmol; 1.29 mL) in dichloromethane. The reaction mixture is stirred at room temperature for 4 h. Water and ethyl acetate are added. The aqueous layer is separated and the organic layer is dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure. The residue is dissolved in ethanol (5 mL) and acetyl chloride (3.48 mmol, 0.25 mL) is added. The mixture is stirred at reflux for 5 h. The solvent is removed under reduced pressure and the residue is chromatographed using a gradient of 5% ethyl acetate in hexane to 20% ethyl acetate in hexane to yield the title compound (145 mg, 40%) as a white solid. ES/MS m/e 313 (M+1).
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