[N:1]1([C:7]2[CH:8]=[C:9]3[C:13](=[CH:14][CH:15]=2)[NH:12][N:11]=[CH:10]3)[CH2:6][CH2:5][NH:4][CH2:3][CH2:2]1.[OH-].[Na+].[C:18]([O:22][C:23](=O)[O-:24])([CH3:21])([CH3:20])[CH3:19].O>O1CCOCC1>[C:18]([O:22][C:23]([N:4]1[CH2:5][CH2:6][N:1]([C:7]2[CH:8]=[C:9]3[C:13](=[CH:14][CH:15]=2)[NH:12][N:11]=[CH:10]3)[CH2:2][CH2:3]1)=[O:24])([CH3:21])([CH3:20])[CH3:19]To a solution of 5-Piperazin-1-yl-1H-indazole (0.34 g, 1.3 mmol) in 1,4-dioxane (5 mL) was added 3N NaOH (0.42 mL, 1.3 mmol). After cooling to 0° C., a solution of tert-butylcarbonate (0.25 g, 1.3 mmol) in 1,4-dioxane (1 mL) was added dropwise. The reaction mixture was stirred at room temperature overnight and then poured into water and extracted with EtOAc. The combined organic layers were washed with saturated aqueous NaHCO3, water, brine, dried and concentrated. The residue was purified by column chromatography (EtOAc:hexanes, 1:1) to give 4-(1H-Indazol-5-yl)-piperazine-1-carboxylic acid tert-butyl ester (0.31 g, 82%) as a white solid. 1H NMR (CDCl3, 400 MHz) δ 10.01 (s, 1H), 7.80 (s, 1H), 7.42 (d, J=9.2 Hz, 1H), 7.21 (dd, J=9.2 Hz, J=2.0 Hz, 1H), 7.16 (d, J=2.0 Hz, 1H), 3.62 (m, 4H), 3.09 (m, 4H), 1.50 (s, 9H). LCMS (APCI+) m/z 303 [M+H]+; Rt=2.50 minutes.
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