To a reaction vial containing an acetonitrile solution (50.6 mL) of copper(I) oxide (0.906 g, 6.33 mmol), salicylaldimine (3.47 g, 25.3 mmol), 1H-pyrazole (12.93 g, 190 mmol) and cesium carbonate (66.0 g, 203 mmol) was added under nitrogen protection 3-bromopyridine (20 g, 127 mmol). The reaction mixture was heated to reflux for 24 hours. After completion of the reaction, the mixture was cooled to room temperature, diluted with ethyl acetate (EtOAc) and filtered through a diatomaceous earth pad. The filtrate was washed sequentially with water and saturated brine, the organic phase was separated, dried with anhydrous magnesium sulfate (MgSO4), filtered and concentrated under reduced pressure. The resulting crude product was purified by column chromatography with the eluent being a hexane solution of 0-50% acetone to afford 3-(1H-pyrazol-1-yl)pyridine as a yellow oil (17 g, 93% yield). The product was confirmed by 1H NMR (400 MHz, acetone-d6): δ 9.14 (d, J = 2.2 Hz, 1H), 8.54 (d, J = 3.8 Hz, 1H), 8.45 (dd, J = 2.5, 0.5 Hz, 1H), 8.24 (ddd, J = 8.3, 2.7, 1.5 Hz, 1H), 7.79 (d, J = 1.5 Hz, 1H), 7.53 (ddd, J = 8.3, 4.7, 0.7 Hz, 1H), 6.59 (dd, J = 2.5, 1.8 Hz, 1H); EIMS m/z 145.
