5-Amino-2-fluoropyridine

0.282 g of 5percent Pd / C and lOmmol of anhydrous sodium sulfate were added to a 100 mL round bottom flask containing 50 mmol of 5-nitro-2-fluoropyridine in 50 ml of toluene, then hydrogen gas was added and heated and stirred for 15 hours. After completion of the reaction, the mixture was cooled to room temperature, suction filtered, spin-evaporated, recrystallized and dried in vacuo to give 1.6806 g of 5-amino-2-fluoropyridine as a solid product in 75percent yield.To 100 g of 2-chloro-5-nitropyridine (Aldrich) in 600 mL of dimethyl sulfoxide under an inert atmosphere was added 100 g of anhydrous KF. The reaction was heated at 70° C. for 18 hours before cooling and diluting with 500 mL each of brine, ethyl acetate, and hexanes. This mixture was filtered through a pad of celite, the organic phase was separated, and the aqueous phase was extracted three times with equal volumes of ethyl acetate and hexanes. The pooled organic phases were washed with brine, dried with anhydrous sodium sulfate, and stripped of the solvents. This crude product was passed through a plug of silica gel with a gradient of 10-30percent ethyl acetate/hexanes and stripped to constant weight on a rotary evaporator to give 76 g (84percent) of 2-fluoro-5-nitropyridine as an oil, which was used in the following procedure. To 76 g of 2-fluoro-5-nitropyridine in 500 ml of ethyl acetate under nitrogen was added 100 g of Raney nickel which had been washed three times with ethanol and three times with ethyl acetate. The nitrogen was replaced with hydrogen and the reaction was allowed to proceed for 18 hours at 30 lb/in2. After the hydrogen atmosphere had been replaced by nitrogen, the reaction was filtered through celite and stripped of solvent. The product was purified by passing through a plug of silica gel with chloroform and recrystallized from chloroform to give 42 g (70percent) of 6-fluoro-pyridin-3-ylamine in two crops as white platelets: melting point 90-91° C.; mass spectrum (m/e): M+H 112.7.To 100 g of 2-chloro-5-nitropyridine (Aldrich) in 600 mL of dimethyl sulfoxide under an inert atmosphere was added 100 g of anhydrous KF. The reaction was heated at 70C for 18 hours before cooling and diluting with 500 mL each of brine, ethyl acetate, and hexanes. This mixture was filtered through a pad of celite, the organic phase was separated, and the aqueous phase was extracted three times with equal volumes of ethyl acetate and hexanes. The pooled organic phases were washed with brine, dried with anhydrous sodium sulfate, and stripped of the solvents. This crude product was passed through a plug of silica gel with a gradient of 10-30percent ethyl acetate/hexanes and stripped to constant weight on a rotary evaporator to give 76 g (84percent) of 2-fluoro-5-nitropyridine as an oil, which was used in the following procedure. To 76 g of 2-fluoro-5-nitropyridine in 500 ml of ethyl acetate under nitrogen was added 100 g of Raney nickel which had been washed three times with ethanol and three times with ethyl acetate. The nitrogen was replaced with hydrogen and the reaction was allowed to proceed for 18 hours at 30 lb/in2. After the hydrogen atmosphere had been replaced by nitrogen, the reaction was filtered through celite and stripped of solvent. The product was purified by passing through a plug of silica gel with chloroform and recrystallized from chloroform to give 42 g (70percent) of 6-fluoro-pyridin-3-ylamine in two crops as white platelets: melting point 90-91C; mass spectrum (m/e): M+H 112.7.