[Br:1]N1C(=O)CCC1=O.[S:9]1[C:13]2[CH:14]=[CH:15][CH:16]=[CH:17][C:12]=2[C:11]([CH:18]([O:23][C:24]([CH3:27])([CH3:26])[CH3:25])[C:19]([O:21][CH3:22])=[O:20])=[CH:10]1.O>C(#N)C>[Br:1][C:10]1[S:9][C:13]2[CH:14]=[CH:15][CH:16]=[CH:17][C:12]=2[C:11]=1[CH:18]([O:23][C:24]([CH3:27])([CH3:26])[CH3:25])[C:19]([O:21][CH3:22])=[O:20]N-bromosuccinimide (67 mg, 0.37 mmol) was added at room temperature to a stirred solution of methyl 2-(1-benzothiophen-3-yl)-2-(tert-butoxy)acetate (4b) (70 mg, 0.25 mmol) in acetonitrile (2 mL) under a nitrogen atmosphere. After 20 hours, water (10 mL) was added and the reaction mixture was extracted with dichloromethane (2×10 mL). The organic layer was washed with brine (10 mL), dried over sodium sulfate, filtered and evaporated to dryness. The residue was purified by flash chromatography on silica gel (cyclohexane/ethyl acetate 90/10) to afford the desired product (4c) as a pale oil (40 mg, 0.11 mmol, 45%).
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