Ethanol → 1-Ethyl-1H-pyrazolo[3,4-b]pyridine-4,5-dicarboxylic acid

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Reaction Steps

4-Cyano-1-ethyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid, ethyl ester (2.0 g, 8.2 mmol) was suspended in ethanol (20 mL), and an aqueous solution of NaOH (6 N, 3 eq) was added. The reaction mixture was heated at reflux for 2 h and then diluted with water (100 mL). This aqueous solution was extracted with diethyl ether (50 mL×2) and the organic extracts were discarded. The aqueous layer was then acidified with phosphoric acid and extracted with EtOAc (50 mL×3). The extracts were concentrated via evaporation under reduced pressure to afford the title compound (>90% purity, 50-90% yield). This material was used directly without further purification.

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