a) Synthesis of 2-phenyl-pyridin-4-ylamine: To a stirred solution of 16.0 g (124 mmol) of 2-chloro-4-aminopyridine dissolved in 200 ml of toluene, 18.2 g (149 mmol) of phenylboronic acid, 7.19 g (6.22 mmol) of tetrakis(triphenylphosphine)palladium(0), and 130 ml (260 mmol) of 2M sodium carbonate were added in turn. aqueous solution. The reaction mixture was heated to reflux at 100 °C for 16 h and subsequently cooled to room temperature. The reaction solution was extracted three times with ethyl acetate and the organic phases were combined. The organic phase was washed three times with 200 ml of 1 M hydrochloric acid aqueous solution. The acidic and aqueous phases were combined, adjusted to alkaline with 5 M aqueous sodium hydroxide and extracted three times with dichloromethane. The organic extracts were combined, dried with anhydrous sodium sulfate and concentrated under reduced pressure. The crude product was purified by fast column chromatography (eluent: acetone) and subsequently ground in hexane containing a small amount of ether to give 18.5 g (87% yield) of 2-phenyl-pyridin-4-ylamine as a white solid.ES-MS m/e (relative abundance): 171 ([M+H]+, 100).
