Cl[C:2]1[CH:7]=[CH:6][N:5]=[CH:4][C:3]=1[N+:8]([O-:10])=[O:9].C(N(CC)CC)C.[C:18]([O:22][C:23]([N:25]1[CH2:30][CH2:29][NH:28][CH2:27][CH2:26]1)=[O:24])([CH3:21])([CH3:20])[CH3:19]>O1CCOCC1>[C:18]([O:22][C:23]([N:25]1[CH2:30][CH2:29][N:28]([C:2]2[CH:7]=[CH:6][N:5]=[CH:4][C:3]=2[N+:8]([O-:10])=[O:9])[CH2:27][CH2:26]1)=[O:24])([CH3:21])([CH3:19])[CH3:20]A solution of 4-chloro-3-nitro-pyridine (2.0 mmol, 0.32 g), triethylamine (3.0 mmol, 0.42 mL) and piperazine-1-carboxylic acid tert-butyl ester (2.5 mmol, 0.47 g) in dioxane (2 mL) was irradiated using microwave for 8 minutes at a temperature of 150° C. The solution was then cooled to room temperature and concentrated in vacuo and the resulting residue was purified using flash column chromatography on silica gel (eluent: ethyl acetate) to provide 4-(3-nitro-pyridin-4-yl)-piperazine-1-carboxylic acid tert-butyl ester as a yellow solid (633 mg, quantitative yield). 1H NMR (400 MHz, CDCl3) δ 8.87 (s, 1H), 8.40 (d, J=5.6 Hz, 1H), 6.87 (d, J=6.0 Hz, 1H), 3.68-3.56 (m, 4H), 3.32-3.18 (m, 4H), 1.48 (s, 9H).
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