Synthesis
General procedure for the synthesis of 7-hydroxy-2-oxo-2H-benzopyran-3-carboxylic acid from ethyl 7-hydroxy-2-oxo-2H-benzopyran-3-carboxylate: ethyl 7-hydroxy-2-oxo-2H-benzopyran-3-carboxylate (2.00 g, 8.55 mmol) was dissolved in water (20 ml) at 90 °C and concentrated hydrochloric acid (6 ml) was added slowly. The reaction mixture was refluxed for 8 hours. After the reaction was completed, the reaction solution was cooled to room temperature, the precipitate was collected by filtration and washed with cold water to obtain 7-hydroxy-2-oxo-2H-benzopyran-3-carboxylic acid (1.32 g, 6.41 mmol) as a light red solid in 75% yield.
References
[1] Indian Journal of Chemistry, Section B: Organic Chemistry Including Medicinal Chemistry, 1986, vol. 25, p. 638 - 639
[2] Food Chemistry, 2012, vol. 135, # 4, p. 2872 - 2878
[3] ACS Medicinal Chemistry Letters, 2015, vol. 6, # 5, p. 502 - 506
[4] Chemical Communications, 2017, vol. 53, # 11, p. 1813 - 1816
[5] Patent: CN106279125, 2017, A. Location in patent: Paragraph 0041; 0042
