The general procedure for the synthesis of 2-hydrazinyl-4-methylpyridine from 2-fluoro-4-methylpyridine was as follows: first, 3.3 g (30.0 mmol) of 2-fluoro-4-methylpyridine was dissolved in 40 ml of ethylene glycol monoethyl ether. Subsequently, 14.6 ml (15.0 g, 300 mmol) of hydrazine hydrate was slowly added to this solution. The reaction mixture was heated to boiling (the oil bath temperature was maintained at 150°C) and the reaction was continuously stirred under these conditions for 16 hours. Upon completion of the reaction, the reaction solution was concentrated using a rotary evaporator. The concentrated residue was dissolved in 100 ml of water and extracted with ethyl acetate (100 ml each time for three times). All organic phases were combined, dried with anhydrous sodium sulfate, filtered and concentrated again. Finally, the crude product obtained was dried under reduced pressure to give 1.90 g of the target compound in 51% yield. The product was analyzed by LC-MS (Method 1): retention time Rt = 0.80 min; mass spectrum (ESI positive ion mode): m/z = 124 [M + H]+; 1H-NMR (400 MHz, DMSO-d6) data: δ = 7.83 (d, 1H), 7.22 (s, 1H), 6.51 (s, 1H), 6.38 (d, 1H). 4.04 (s, 2H), 2.17 (s, 3H).
