Cl.[Br:2][C:3]1[CH:10]=[CH:9][C:6]([CH2:7][NH2:8])=[CH:5][CH:4]=1.C(=O)([O-])[O-].[K+].[K+].[O:17](C(OC(C)(C)C)=O)[C:18]([O:20][C:21]([CH3:24])([CH3:23])[CH3:22])=O.CCOC(C)=O>C1COCC1.O>[C:21]([O:20][C:18](=[O:17])[NH:8][CH2:7][C:6]1[CH:9]=[CH:10][C:3]([Br:2])=[CH:4][CH:5]=1)([CH3:24])([CH3:23])[CH3:22]
A solution of 4-bromobenzylamine hydrochloride 116 (2.225 g, 10.0 mmol) and potassium carbonate (2.07 g, 15.0 mmol, 1.5 equiv) in THF (20 mL) and water (5 mL) was treated with BOC2O (2.40 g, 11.0 mmol, 1.1 equiv) at room temperature and stirred for 12 h. When TLC and HPLC/MS showed the reaction was complete, the reaction mixture was treated with water (10 mL) and EtOAc (40 mL). The two layers were separated, and the aqueous layer was extracted with EtOAc (20 mL). The combined organic extracts were washed with water (2×20 mL) and saturated aqueous NaCl (20 mL), dried over MgSO4, and concentrated in vacuo. The residue was further dried in vacuo to afford the desired (4-bromo-benzyl)-carbamic acid tert-butyl ester 117 (2.60 g, 90.9% yield) as a colorless oil.
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