[N:1]1([C:7]([O:9][C:10]([CH3:13])([CH3:12])[CH3:11])=[O:8])[CH2:6][CH2:5][NH:4][CH2:3][CH2:2]1.[C:14]([O:18][CH2:19][CH3:20])(=[O:17])[CH:15]=[CH2:16].C(OCC)C>C(O)C>[C:14]([CH2:15][CH2:16][N:4]1[CH2:5][CH2:6][N:1]([C:7]([O:9][C:10]([CH3:13])([CH3:12])[CH3:11])=[O:8])[CH2:2][CH2:3]1)([O:18][CH2:19][CH3:20])=[O:17]Combine t-butyl 1-piperazinecarboxylate (10.47 g, 56.2 mmol), ethyl acrylate (8 mL) in ethanol (30 mL). Heat at reflux. After 5.5. hours, cool the reaction mixture and evaporate in vacuo to give a residue. Combine the residue and diethyl ether (200 mL) and extract with a 1 M aqueous solution of hydrochloric acid. Adjust the pH of the aqueous layer to basic using sodium bicarbonate and then extract with ethyl acetate. Dry the organic layer over MgSO4, filter, and evaporate in vacuo to give t-butyl 4-carboethoxyethyl-1-piperazinecaboxylate.
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