GENERAL PROCEDURE: A mixture of ethyl 6-fluoroindole-2-carboxylate (33.5 g, 0.15 mol), 4% sodium hydroxide solution (335 mL), and anhydrous ethanol (335 mL) was heated to reflux for 3 hours. Upon completion of the reaction, the mixture was cooled to room temperature and subsequently poured into ice water. The pH of the mixture was adjusted to 5 with glacial acetic acid and then the precipitate was collected by filtration. 6-Fluoroindole-2-carboxylic acid was finally obtained as a white solid (26.4 g, 90% yield).
[1] European Journal of Medicinal Chemistry, 2011, vol. 46, # 7, p. 3149 - 3157
[2] Journal of the Chemical Society, 1955, p. 1283,1284
