General procedure for the synthesis of 2-pyrazole-1-pyridine (Pyr-N-PzH) from pyrazole and 2-bromopyridine: To a 250 mL single-necked round-bottomed flask were added 15.0 g (95 mmol) of 2-bromopyridine, 25.0 g (367 mmol, 3.86 equiv) of pyrazole and 45 mL of xylene. The reaction mixture was heated to reflux for 8 hours and subsequently cooled to room temperature. The resulting mixture was dissolved in dichloromethane and the organic layer was washed four times with 250 mL of water (until pyrazole was not detected by gas chromatography). The organic layer was dried over anhydrous magnesium sulfate, filtered and rotary evaporated to give 12.0 g (82.6 mmol, 87% yield) of the target product as a white solid. The structure of the product was confirmed by 1H NMR (400 MHz, CDCl3): δ 8.59 (m, 1H, pyridinyl 6-H), 8.39 (s, 1H, pyrazol-5-H), 7.90 (d, 1H, pyridinyl 3-H), 7.80 (m, 1H, pyridinyl 4-H), 7.73 (s, 1H, pyrazol 3-H), 7.15 (s, 1H, pyridinyl -5-H), 6.45 (m, 1H, pyrazole-4-H).
