Methanol → 1H-pyrazolo[3,4-b]pyridine-3-carboxylic acid

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Reaction Conditions

Reaction Steps

To a solution of NaOH (0.88 g, 22 mmol) in water (20 mL) was added 3-methyl-1H-pyrazolo[3,4-b]pyridine (IV) (0.4 g, 3 mmol). The suspension was heated at 80° C. until a clear solution was obtained. A solution of KMnO4 (1.73 g, 11 mmol) in water (180 mL) was added slowly over 2 h while heating the solution at 80° C. The solution was heated at 90° C. for an additional 2 h until the complete disappearance of starting material was observed by TLC. The solution was cooled to 70° C. and filtered through a pad of Celite. The solids were washed by boiling water. The combined filtrate was cooled to 0° C., acidified with conc. H2504 to pH=2 and extracted with n-butanol (2×10 mL). The n-butanol layer was concentrated under reduced pressure to get a white residue which was dissolved in DCM by adding minimum amount of MeOH and then filtered. The filtrate was concentrated to give 1H-pyrazolo[3,4-b]pyridine-3-carboxylic acid (V) as a white solid (390 mg, 2.39 mmol, 81% yield). 1H NMR (CDCl3) δ ppm 7.37 (dd, J=8.10, 4.52 Hz, 1H), 8.47 (dd, J=7.54, 1.88 Hz, 1H), 8.62 (dd, J=4.52, 1.32 Hz, 1H), 14.37 (brs, 1H).

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