Synthesis
General procedure for the synthesis of 6-bromo-1H-indole-3-carboxylic acid from 1-(6-bromo-1H-indol-3-yl)-2,2,2-trifluoroethanone: 1-(6-bromo-1H-indol-3-yl)-2,2,2-trifluoroethanone (1.0 eq., 1.0 g) was mixed with a 20% aqueous sodium hydroxide solution (17 mL) and heated to 100 °C. Stirring was continued at this temperature until the reaction was complete (about 18 hours). After completion of the reaction, the solution was cooled to room temperature and washed twice with dichloromethane. Subsequently, the aqueous solution was acidified with hydrochloric acid to the appropriate pH, the precipitate precipitated was collected by filtration and dried under vacuum to afford the target product 6-bromo-1H-indole-3-carboxylic acid (715 mg, 87% yield).
References
[1] Patent: WO2011/50245, 2011, A1. Location in patent: Page/Page column 81
[2] Patent: EP2548864, 2013, A1. Location in patent: Paragraph 0171
[3] Patent: WO2013/14102, 2013, A1. Location in patent: Page/Page column 26; 31
[4] Patent: US2014/200215, 2014, A1. Location in patent: Paragraph 0978; 0980
[5] Bioorganic and Medicinal Chemistry Letters, 2011, vol. 21, # 23, p. 7107 - 7112
