Synthesis
The general procedure for the synthesis of 4-hydroxy-6-bromoquinoline-3-carboxylic acid from ethyl 6-bromo-4-hydroxy-3-quinolinecarboxylate was as follows: ethyl 6-bromo-4-hydroxy-3-quinolinecarboxylate (102.59 g, 337.7 mmol) was suspended in a 10% aqueous potassium hydroxide solution (689 mL) and heated and refluxed for 5 hours, and the reaction solution changed to light brown. After completion of the reaction, it was cooled to room temperature and filtered to remove undissolved solid particles. The filtrate was extracted with dichloromethane to remove neutral impurities. The aqueous layer was neutralized with 3.0 N hydrochloric acid to precipitate a white precipitate. The solid was collected by filtration and washed with water. After drying in air, 4-hydroxy-6-bromoquinoline-3-carboxylic acid was obtained as 91 g (98% yield) as a white solid.EI-HRMS m/e calculated value of C10H6BrNO3 (M+) 266.9531, measured value 266.9521.
References
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[3] Patent: CN106432073, 2017, A. Location in patent: Paragraph 0061; 0062; 0067; 0068
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