[I:1]I.[NH:3]1[C:7]2=[N:8][CH:9]=[CH:10][C:11]([N:12]3[CH2:17][CH2:16][N:15]([C:18]([O:20][C:21]([CH3:24])([CH3:23])[CH3:22])=[O:19])[CH2:14][CH2:13]3)=[C:6]2[CH:5]=[N:4]1.[OH-].[K+].[O-]S([O-])=O.[Na+].[Na+]>CN(C=O)C.CCOCC>[I:1][C:5]1[C:6]2[C:7](=[N:8][CH:9]=[CH:10][C:11]=2[N:12]2[CH2:17][CH2:16][N:15]([C:18]([O:20][C:21]([CH3:24])([CH3:23])[CH3:22])=[O:19])[CH2:14][CH2:13]2)[NH:3][N:4]=1I2 (0.920 g, 3.63 mmol) was added to tert-butyl 4-(1H-pyrazolo[3,4-b]pyridin-4-yl)piperazine-1-carboxylate (0.55 g, 1.81 mmol) and KOH (0.305 g, 5.44 mmol) (crushed by motar and pestle) in DMF (10 mL). The resulting mixture was warmed to 60° C. and stirred for 2 hours. Ether (20 mL) and saturated Na2SO3 (10 mL) were then added. The organic layer was separated, washed with brine and dried over sodium sulfate. After removal of the solvent, the resulting residue was purified by chromatography (hexane:ethyl acetate, 3:1) to give tert-butyl 4-(3-iodo-1H-pyrazolo[3,4-b]pyridin-4-yl)piperazine-1-carboxylate (0.45 g, 58%) as a solid. MS APCI (+) m/z 430.0 detected. 1H NMR (400 Hz, DMSO-d6) δ 8.31 (d, J=5.2 Hz, 1H), 6.63 (d, J=5.6 Hz, 1H), 3.63 (m, 4H), 3.18 (m, 4H), 1.44 (s, 9H).
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