The general procedure for the synthesis of 2-fluoro-5-cyanobenzoic acid from methyl 5-cyano-2-fluorobenzoate was as follows: to a solution of ethanol (50 mL) containing methyl 5-cyano-2-fluorobenzoate (3.0 g, 16.8 mmol) was added a 40% aqueous solution of KOH (15 mL). The reaction mixture was heated to 45 °C and stirred continuously for 2 h until all solids were completely dissolved. Upon completion of the reaction, the mixture was cooled to room temperature and partially concentrated under reduced pressure. Subsequently, the reaction mixture was diluted with ethyl acetate (EtOAc) and acidified with 10% aqueous hydrochloric acid. The organic and aqueous layers were separated and the aqueous layer was further extracted with ethyl acetate (3 x 20 mL). All organic extracts were combined, dried with anhydrous sodium sulfate (Na2SO4), filtered and concentrated under reduced pressure to afford the target product 2-fluoro-5-cyanobenzoic acid (3.0 g, 16.4 mmol, 98% yield). Mass spectrometry analysis (DCI/NH3) showed m/z 183 (M+NH4)+.
