Synthesis of 3,6-dichloro-2-cyanopyridine: 2,5-dichloropyridine-N-oxide (11.7 g, 71.38 mmol) was added batchwise to dimethyl sulfate (9 g, 71.35 mmol), followed by stirring the reaction mixture overnight. Upon completion of the reaction, 50 mL of ether was added to the mixture and stirring was continued. Subsequently, the ether layer was removed by decantation and the remaining ether was removed by distillation under vacuum. The residue was dissolved in 50 mL of water to obtain Solution A. In another vessel, sodium cyanide (13.77 g, 71.38 x 3.9 mmol) was dissolved in 67.4 mL of water and the solution was cooled under nitrogen protection to -7 °C to 15 °C. The reaction was carried out by stirring. The pre-prepared solution A was slowly added dropwise to this cooled sodium cyanide solution under continuous stirring. After the dropwise addition, the reaction temperature was kept constant and stirring was continued for 1.5 hours. At the end of the reaction, the precipitated crystal precipitate was collected by filtration and washed with water, followed by washing the solid product with a small amount of ethyl acetate. The resulting white solid had a melting point of 90-92 °C and yielded 6.6 g in 53.6% yield. The product was analyzed by IR (KBr, cm-1 ) showing characteristic absorption peaks: 2254, 1428, 1164, 840. 1H-NMR (60 MHz, CDCl3, δ) data: 7.4 (1H, d, J = 8 Hz, pyridine ring H), 7.8 (1H, d, J = 8 Hz, pyridine ring H).
