[C:1]([O:5][C:6]([CH:8]1[CH2:14][CH2:13][C:12]2[CH:15]=[CH:16][C:17]([O:19][CH3:20])=[CH:18][C:11]=2[N:10]([CH2:21][CH3:22])[C:9]1=[O:23])=[O:7])([CH3:4])([CH3:3])[CH3:2].C1C(=O)N(Br)C(=O)C1.C/C(/O[Si](C)(C)C)=N\[Si](C)(C)C.C(Cl)(Cl)(Cl)Cl>C(Cl)Cl>[C:1]([O:5][C:6]([CH:8]1[CH:14]=[CH:13][C:12]2[CH:15]=[CH:16][C:17]([O:19][CH3:20])=[CH:18][C:11]=2[N:10]([CH2:21][CH3:22])[C:9]1=[O:23])=[O:7])([CH3:4])([CH3:3])[CH3:2]A three-necked flask, equipped with reflux condenser, was charged with 3-tert-butoxycarbonyl-1-ethyl-8-methoxy-2,3,4,5-tetrahydro-1H-1-benzazepine-2-one (4.0 g, 12.52 mmol), NBS (2.452 g, 13.76 mmol), N,O-bis(trimethylsilyl)acetamide (1.712 mL, 6.88 mmol), BPO (ca. 20 mg) and carbon tetrachloride (160 mL). The suspension was heated to reflux when another portion (ca. 20 mg) of BPO was added. After being refluxed for 3 hrs, the reaction mixture was diluted with DCM (100 mL), washed with water and dried over Na2SO4. The reaction was repeated for another 5 times and the combined organic layers were filtered and evaporated. The residue was repeatedly purified by flash chromatograghy on silica column eluted by ethyl acetate/DCM (2.5%) or ethyl acetate/hexane (20%). The crystal residue was further washed with ethyl acetate/hexane (20%) and dried in vacuum, giving the title compound (4.970 g, 21%) as white crystal.
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