[C:1]([O:5][C:6](=[O:20])[NH:7][C@H:8]1[C:14](=[O:15])[NH:13][C:12]2[CH:16]=[CH:17][CH:18]=[CH:19][C:11]=2[CH2:10][CH2:9]1)([CH3:4])([CH3:3])[CH3:2].C(O)(=O)C.[Br:25]Br>C(OCC)(=O)C>[C:1]([O:5][C:6](=[O:20])[NH:7][C@@H:8]1[CH2:9][CH2:10][C:11]2[CH:19]=[C:18]([Br:25])[CH:17]=[CH:16][C:12]=2[NH:13][C:14]1=[O:15])([CH3:4])([CH3:2])[CH3:3]A round-bottom flask containing ((R)-2-oxo-2,3,4,5-tetrahydro-1H-benzo[b]azepin-3-yl)-carbamic acid tert-butyl ester (0.338 g, 1.20 mmol) was fitted with a stirbar and septa. Acetic acid (glacial, 5 mL) and bromine (0.37 g, 2.3 mmol) were added, in that order, giving a solution that was stirred at room temperature for 1.5 hours. The reaction was then poured into ethyl acetate (50 mL) and washed with saturated aqueous NaHCO3 solution (2×50 mL). The organic layer was dried over MgSO4, filtered and concentrated in vacuo to give an oil that was purified via flash chromatography on silica gel (10% to 50% ethyl acetate/hexanes linear gradient) to give the desired product.
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