General procedure for the synthesis of 2-cyano-5-fluoropyridine from 3-amino-6-cyanopyridine: Sodium nitrite (8.7 g, 126 mmol) was added in batches to ice-salt-bath-cooled 5-amino-pyridine-2-carbonitrile (10.03 g, 84.2 mmol) dissolved in a solution of 70% hydrogen fluoride-pyridine (Aldrich, 100 g, 3.5 mol HF) ( Note: the reaction was carried out in a special reaction flask). The reaction solution was dark red in color, and after stirring in an ice-salt bath for 45 min, the ice bath was removed and the mixture continued to be stirred at room temperature for 30 min, followed by heating at 80 °C for 1.5 h. The reaction was carried out in a special reaction flask. Upon completion of the reaction, the reaction mixture was quenched by slowly pouring it into an ice/water mixture (about 400 g), extracted with dichloromethane (6 x 150 mL), the organic phase was dried over anhydrous magnesium sulfate, filtered and the solvent was concentrated under reduced pressure. The resulting crude product (10.08 g, 98% yield, orange solid) was pure enough for subsequent use and did not require further purification. The product was characterized by 1H NMR (CDCl3, 300 MHz): δ= 8.61 (d, 1H), 7.78 (m, 1H), 7.58 (m, 1H).GC-MS showed the molecular ion peak M+ 122.
