Synthesis
General procedure for the synthesis of 1-benzofuran-5-carboxylic acid from methyl benzofuran-5-carboxylate: Methyl benzofuran-5-carboxylate (1.3 g, 7.38 mmol) was dissolved in methanol (51 mL), 5% aqueous sodium hydroxide solution (41 mL) was added, and the mixture was stirred. The reaction mixture was heated to 65 °C and kept at this temperature for 4 hours. After completion of the reaction, the mixture was cooled to room temperature and the methanol was removed by distillation under reduced pressure. The remaining aqueous phase was extracted with dichloromethane and the organic phase was discarded. The aqueous phase was acidified with concentrated hydrochloric acid to pH=1 and then extracted with chloroform. The organic phases were combined, washed with deionized water, dried over anhydrous magnesium sulfate, filtered and concentrated under reduced pressure to give 1.2 g (98% yield) of 1-benzofuran-5-carboxylic acid as a white solid.1H NMR (400 MHz, DMSO-d6) δ 12.9, 8.30, 8.11, 7.92, 7.69, 7.09.
References
[1] Patent: US2003/232853, 2003, A1. Location in patent: Page 37
[2] Patent: WO2004/39815, 2004, A2. Location in patent: Page 70
[3] Patent: WO2017/155909, 2017, A1. Location in patent: Paragraph 0182
[4] Bioorganic and Medicinal Chemistry, 2018, vol. 26, # 8, p. 1797 - 1809
[5] Journal of Medicinal Chemistry, 1995, vol. 38, # 16, p. 3094 - 3105
