[H-].[Na+].[CH2:3]([O:10][C:11]([N:13]1[CH2:18][CH2:17][NH:16][C:15](=[O:19])[CH2:14]1)=[O:12])[C:4]1[CH:9]=[CH:8][CH:7]=[CH:6][CH:5]=1.[CH2:20](Br)[C:21]#[CH:22]>C1COCC1.CN(C=O)C>[CH2:3]([O:10][C:11]([N:13]1[CH2:18][CH2:17][N:16]([CH2:22][C:21]#[CH:20])[C:15](=[O:19])[CH2:14]1)=[O:12])[C:4]1[CH:5]=[CH:6][CH:7]=[CH:8][CH:9]=1Sodium hydride (0.82 g, 23.0 mmol, 60% mineral oil dispersion) is added to a solution of 4-benzyloxycarbonylpiperazin-2-one (5.13 g, 21.9 mmol) in THF/DMF (75 mL, 3/1 v/v) at 0° C. The mixture is stirred for 5 minutes, then propargyl bromide (3.7 mL, 41.5 mmol) is added dropwise. The resulting solution is stirred for 1 hour then brought to room temperature and stirred for 2 hours. The reaction is quenched with saturated ammonium chloride solution then diluted with ethyl acetate and washed with water (4×) and brine. The organic layer is dried over MgSO4, filtered and concentrated to dryness. The residue is purified by column chromatography eluting with 5% MeOH/CH2Cl2 to give the product (5.96 g, 21.9 mmol) as a white solid. 1H NMR (CDCl3, 300 MHz) δ7.3 (m, 5H), 5.12 (s, 2H), 4.25 (s,2H), 4.16 (s, 2H), 3.75 (m, 2H), 3.47 (m, 2H), 2.22 (s, 1H).
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