Br[CH2:2][CH2:3][C:4]#[CH:5].[C:6]([O:10][C:11]([N:13]1[CH2:18][CH2:17][NH:16][CH2:15][CH2:14]1)=[O:12])([CH3:9])([CH3:8])[CH3:7].C(=O)([O-])[O-].[K+].[K+].O>C(#N)C>[CH2:2]([N:16]1[CH2:15][CH2:14][N:13]([C:11]([O:10][C:6]([CH3:9])([CH3:8])[CH3:7])=[O:12])[CH2:18][CH2:17]1)[CH2:3][C:4]#[CH:5]A solution of 4-bromo-1-butyne (0.500 g, 3.76 mmol) in acetonitrile (20 mL) was added with 1-tert-butoxycarbonylpiperazine (0.700 g, 3.76 mmol) and potassium carbonate (0.779 g, 5.64 mmol), and the mixture was stirred at 60° C. for 6 hours. The reaction mixture was added with water, and the mixture was extracted with methylene chloride. The organic layer was washed with saturated brine, then dried over anhydrous magnesium sulfate, and concentrated under reduced pressure. The resulting residue was purified by silica gel column chromatography (hexane/ethyl acetate) to obtain tert-butyl 4-(but-3-ynyl)piperazine-1-carboxylate (0.621 g, 69%).
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