General procedure for the synthesis of 5-fluorothiophene-2-carboxylic acid from 5-fluorothiophene-2-carbonitrile: 138 mg (1.07 mmol) of 5-fluorothiophene-2-carbonitrile and 5 ml of 1N sodium hydroxide solution were added to an eggplant flask, and the mixture was heated and stirred in an oil bath at 100 °C for 2 hours. After completion of the reaction, the reaction solution was cooled to room temperature. Subsequently, 5 ml of water was added to the reaction solution for dilution and the pH was adjusted with 10 ml of 1N hydrochloric acid to 1. Next, the mixture was extracted twice with 30 ml of dichloromethane. The organic layers were combined and dried with anhydrous sodium sulfate. Finally, the solvent was removed by concentration under reduced pressure to give 110 mg of 5-fluorothiophene-2-carboxylic acid.
