313337-34-7

Step B: Potassium hydroxide (13.04 g, 0.232 mol) was dissolved in a 14% water/ethanol mixture (50 ml) and 4-fluoro-1H-indole-7-carbonitrile (900 mg, 5.60 mmol) was added. The reaction mixture was refluxed for 12 h followed by slow cooling to room temperature and concentrated under vacuum to about 30 ml. The residue was acidified to pH 2 with an aqueous hydrochloric acid solution of about 5.5 N. The precipitate was collected by filtration, washed with excess water and dried under high vacuum to give 4-fluoro-7-carboxyindole as a white solid (100% conversion). The resulting product can be used in subsequent reactions without further purification.

[1] Patent: US6469006, 2002, B1
[2] Patent: US2004/6090, 2004, A1. Location in patent: Page/Page column 33
[3] Patent: WO2004/11425, 2004, A2. Location in patent: Page 73
[4] Bioorganic and Medicinal Chemistry Letters, 2013, vol. 23, # 1, p. 198 - 202