[O:1]=[C:2]1[NH:7][CH2:6][CH2:5][N:4]([C:8]([O:10][C:11]([CH3:14])([CH3:13])[CH3:12])=[O:9])[CH2:3]1.[CH3:15][N:16]1[CH:20]=[C:19](I)[CH:18]=[N:17]1.C(O)CO.P([O-])([O-])([O-])=O.[K+].[K+].[K+]>C(O)(C)C.[Cu](I)I>[CH3:15][N:16]1[CH:20]=[C:19]([N:7]2[CH2:6][CH2:5][N:4]([C:8]([O:10][C:11]([CH3:14])([CH3:13])[CH3:12])=[O:9])[CH2:3][C:2]2=[O:1])[CH:18]=[N:17]1
tert-Butyl 3-oxopiperazine-1-carboxylate (0.164 g, 0.819 mmol) was suspended in isopropanol (3 mL) under an atmosphere of nitrogen and treated with 1-methyl-4-iodo-1H-pyrazole (0.204 g, 0.983 mmol, 1.20 equiv), ethylene glycol (0.051 g, 0.82 mmol, 1.0 equiv), copper iodide (0.031 g, 0.16 mmol, 0.20 equiv), and potassium phosphate (0.695 g, 3.28 mmol, 4.00 equiv), and placed into a preheated oil bath at 100° C. for 8 hours. The mixture was cooled to ambient temperature, concentrated in vacuo and the residue was dissolved in dichloromethane, washed with water, dried with sodium sulfate, filtered, and concentrated in vacuo. The residue was purified by silica gel chromatography (100:0 to 0:100 hexanes:ethyl acetate), providing the titled compound.
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