[O:1]=[C:2]1[NH:7][CH2:6][CH2:5][N:4]([C:8]([O:10][C:11]([CH3:14])([CH3:13])[CH3:12])=[O:9])[CH2:3]1.[H-].[Na+].[Br:17][C:18]1[CH:23]=[CH:22][C:21]([CH2:24]Br)=[CH:20][CH:19]=1>CN(C)C=O>[Br:17][C:18]1[CH:23]=[CH:22][C:21]([CH2:24][N:7]2[CH2:6][CH2:5][N:4]([C:8]([O:10][C:11]([CH3:14])([CH3:13])[CH3:12])=[O:9])[CH2:3][C:2]2=[O:1])=[CH:20][CH:19]=1To a solution of 1,1-dimethylethyl 3-oxo-1-piperazinecarboxylate (500 mg, 2.497 mmol) in N,N-dimethylformamide (DMF) (8 mL) at room temperature under nitrogen was added sodium hydride (60% w/w in mineral oil, 120 mg, 3.00 mmol) and the resulting suspension was stirred at this temperature for 30 min. 1-Bromo-4-(bromomethyl)benzene (749 mg, 3.00 mmol) in DMF (5 mL) was then added via syringe. The resulting mixture was stirred at room temperature for 1.5 h then partitioned between AcOEt and water. The layers were separated and the aqueous phase was extracted three times with AcOEt. The combined organic phases were washed three times with brine, dried over MgSO4 and concentrated in vacuo. Purification of the residue by SP4 using a 25 G silica cartridge (gradient: 13 to 63% AcOEt in Hexanes) gave 1,1-dimethylethyl 4-[(4-bromophenyl)methyl]-3-oxo-1-piperazinecarboxylate (763 mg, 2.066 mmol, 83% yield) as an oil which solidified to a white solid over 16 h.
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