General procedure for the synthesis of 4-(2-pyridyl)aniline from 2-(4-nitrophenyl)pyridine: the compound 2-(4-nitrophenyl)pyridine (0.2 g, 1.03 mmol) was dissolved in methanol (10 mL), 10% palladium-carbon (20 mg) was added as a catalyst, and the reduction reaction was carried out under hydrogen atmosphere. The reaction mixture was stirred at room temperature for 18 hours. Upon completion of the reaction, the catalyst was removed by filtration through a Celite pad, which was washed with methanol (50 mL). After combining the filtrates, the solvent was removed by evaporation under reduced pressure to give the crude product. The crude product was purified by rapid chromatography on silica gel with the eluent dichloromethane-methanol-ammonia (95:4.5:0.5, v/v/v) to afford the target compound 4-(2-pyridyl)aniline (0.15 g, 87% yield) as a brown solid. The physical and spectroscopic data of the product were as follows: melting point 89-92 °C (literature value 94-95 °C); IR spectra (νmax/cm?1) 3333, 3210, 1606, 1586, 1519, 1294, 1181; 1H NMR (500 MHz, CDCl?) δ 8.62 (1H, dt, J=1.0, 5.0 Hz), 7.83 (2H, d, J=8.5 Hz), 7.68-7.61 (2H, m), 7.11 (1H, m), 6.75 (2H, d, J=8.5 Hz), 3.83 (2H, br s); 13C NMR (125 MHz, CDCl?) δ 157.6, 149.5, 147.5, 136.6, 129.8, 128.1, 121.0, 119.4, 115.2; mass spectrometry (ESI) m/z 171 ([M + H]? , 100).
