General procedure for the synthesis of 2-cyano-3-fluoro-5-trifluoromethylpyridine from 3-chloro-2-cyano-5-trifluoromethylpyridine: Cesium fluoride (9.6 g, 63 mmol) and potassium carbonate (250 mg, 1.8 mmol) were suspended in anhydrous DMSO (50 mL) under nitrogen protection, heated to 80 °C and then added 3-chloro-2-cyano-5-trifluoromethyl pyridine (8.7 g, 42 mmol). After 10 min of reaction, the mixture was heated to 95 °C and maintained for 20 min. After completion of the reaction, it was cooled to 55 °C and poured into ice water. It was extracted twice with hexane and then once with dichloromethane. The organic phases were combined and evaporated to give the solid product 2-cyano-3-fluoro-5-trifluoromethylpyridine (8 g, 100% yield). The product was characterized by 1H NMR (400 MHz, CDCl3): δ 7.91 (1H, d, J=7.6 Hz), 8.84 (1H, s).
