[CH3:1][C:2]1[C:3]2[CH:14]=[CH:13][CH:12]=[CH:11][C:4]=2[S:5][C:6]=1[C:7]([O:9][CH3:10])=[O:8].[Br:15]N1C(=O)CCC1=O.N(C(C)(C)C#N)=NC(C)(C)C#N>C1C=CC=CC=1>[Br:15][CH2:1][C:2]1[C:3]2[CH:14]=[CH:13][CH:12]=[CH:11][C:4]=2[S:5][C:6]=1[C:7]([O:9][CH3:10])=[O:8]A 250-mL single-neck round-bottomed flask equipped with a magnetic stirrer, nitrogen inlet and reflux condenser was purged with nitrogen and charged with methyl 3-methylbenzo[b]thiophene-2-carboxylate (2.00 g, 9.70 mmol) and benzene (20 mL). N-bromosuccinimide (1.72 g, 9.70 mmol) and 2,2′-azobisisobutyronitrile (160 mg, 1.00 mmol) were added, and the mixture was refluxed for 2 h. After this time, the mixture was cooled to room temperature and filtered. The filter cake was rinsed with carbon tetrachloride (20 mL) and the filtrate was concentrated under reduced pressure. The resulting residue was purified by column chromatography to afford 103a in 82% yield (2.27 g) as a white solid: mp 101-102° C.; 1H NMR (500 MHz, CDCl3) d 7.97 (m, 1H), 7.86 (m, 1H), 7.51 (m, 2H), 5.22 (s, 2H), 3.97 (s, 3H).
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