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General procedure for the synthesis of 7-azaindole-6-carboxylic acid from 6-cyano-7-azaindole: 1H-pyrrolo[2,3-b]pyridine-6-carbonitrile (120 mg, 0.84 mmol) was dissolved in ethanol (10 mL). To the solution was added 6 N sodium hydroxide solution (1.4 mL, 8.4 mmol) and the reaction mixture was stirred at 90 °C for 18 hours. Upon completion of the reaction, the mixture was distilled under reduced pressure to remove the solvent. Subsequently, a 1 N hydrochloric acid solution was added to the residue for acidification. The acidified solution was extracted with ethyl acetate. The organic phases were combined, washed with saturated aqueous sodium chloride solution, dried over anhydrous magnesium sulfate and filtered. The filtrate was concentrated under reduced pressure and purified by column chromatography to afford the target product 7-azaindole-6-carboxylic acid (100 mg, 74% yield). The nuclear magnetic resonance hydrogen spectrum (1H-NMR, 400 MHz, DMSO-d6) data were as follows: δ 12.08 (broad single peak, 1H), 8.11 (double peak, 1H), 7.83 (double peak, 1H), 7.70 (double peak, 1H), 6.58 (double peak, 1H).

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