1H-indazole-3-carboxylic acid was dissolved in anhydrous acetic acid in a three-necked flask, heated and stirred. After the substrate was dissolved and clarified, phosphorus oxychloride was dissolved in anhydrous acetic acid and slowly added dropwise. In an oil bath at 90°C, the mixture was condensed back into the chemical book and reacted for 14 hours. After the reaction was complete, a white precipitate was produced. It was cooled in an ice bath, vacuum filtered, and the solid was washed with ethyl acetate first and then with ether to obtain 5-Chloro-1H-indazole-3-carboxylic acid.
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