[Br:1][C:2]1[CH:3]=[C:4]([C:11]([O:13][CH2:14][CH3:15])=[O:12])[C:5]2[CH:10]=[N:9][NH:8][C:6]=2[N:7]=1.C([O-])([O-])=O.[K+].[K+].Br[CH:23]([CH3:25])[CH3:24]>C(#N)C>[Br:1][C:2]1[CH:3]=[C:4]([C:11]([O:13][CH2:14][CH3:15])=[O:12])[C:5]2[CH:10]=[N:9][N:8]([CH:23]([CH3:25])[CH3:24])[C:6]=2[N:7]=1To a stirred solution of ethyl 6-bromo-1H-pyrazolo[3,4-b]pyridine-4-carboxylate (20 g, 74.3 mmol) in acetonitrile (200 mL), K2CO3 (15.39 g, 111.52 mmol) and 2-bromopropane (18.13 g, 148.64 mmol) was added to it. The reaction mixture was refluxed for 8 h. On completion, acetonitrile was removed under reduced pressure and water was added to it. Extraction was carried out using ethyl acetate; the combined organic layers were washed with water, brine and dried over anhydrous Na2SO4. Solvent was removed under reduced pressure and residue was purified by silica gel column chromatography to obtain the desired intermediate (13.5 g, 58.3%).
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