Cl[CH2:2][C:3]([N:5]1[CH2:10][CH2:9][C:8](=[O:11])[CH2:7][CH2:6]1)=[O:4].[N:12]1([C:18]([O:20][C:21]([CH3:24])([CH3:23])[CH3:22])=[O:19])[CH2:17][CH2:16][NH:15][CH2:14][CH2:13]1.C(N(C(C)C)C(C)C)C.O>C(#N)C>[O:4]=[C:3]([N:5]1[CH2:10][CH2:9][C:8](=[O:11])[CH2:7][CH2:6]1)[CH2:2][N:15]1[CH2:14][CH2:13][N:12]([C:18]([O:20][C:21]([CH3:24])([CH3:23])[CH3:22])=[O:19])[CH2:17][CH2:16]1
1-(2-Chloroacetyl)piperidin-4-one (5.17 g, 29.4 mmol) was dissolved in acetonitrile (50 ml). To this solution, tert-butyl piperazine-1-carboxylate (5.48 g, 29.4 mmol) and N-ethyldiisopropylamine (6.2 ml, 35.3 mmol) were added, and the mixture was heated under reflux for 2 hours. The reaction mixture was allowed to return to room temperature, to which water was added, and the mixture was extracted with ethyl acetate. The extract was washed with brine, dried over magnesium sulfate, and then filtered. The filtrate was concentrated under reduced pressure, and the residue was purified by silica gel column chromatography (methylene chloride/methanol=100/1) to afford tert-butyl 4-[2-oxo-2-(4-oxopiperidin-1-yl)ethyl]piperazine-1-carboxylate (6.49 g, yield 68%) as a pale yellow crystalline powder.
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