C(=O)([O-])[O-].[K+].[K+].C(N(C(C)C)C(C)C)C.Cl[CH2:17][C:18](=[O:20])[CH3:19].[N:21]1([C:27]([O:29][CH2:30][C:31]2[CH:36]=[CH:35][CH:34]=[CH:33][CH:32]=2)=[O:28])[CH2:26][CH2:25][NH:24][CH2:23][CH2:22]1>C(#N)C>[O:20]=[C:18]([CH3:19])[CH2:17][N:24]1[CH2:23][CH2:22][N:21]([C:27]([O:29][CH2:30][C:31]2[CH:36]=[CH:35][CH:34]=[CH:33][CH:32]=2)=[O:28])[CH2:26][CH2:25]1
Potassium carbonate (1.27 g, 9.22 mmol), N-ethyldiisopropylamine (0.80 ml, 4.61 mmol), and chloroacetone (1.22 ml, 13.83 mmol) were added to a solution of benzyl piperazine-1-carboxylate (2.03 g, 90.22 mmol) in acetonitrile(20 ml), and the mixture was heated under reflux for 2 hours. The insoluble substances were removed by filtration and washed with ethyl acetate. The filtrate was concentrated under reduced pressure. The residue was purified by silica gel column chromatography(methylene chloride/methanol=100/1) to afford benzyl 4-(2-oxopropyl)piperazine-1-carboxylate (2.24 g, yield 88%) as a pale yellow oil.
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