4-(3-Azidopyridin-4-yl)-N,N-dimethylaniline (0.20 g, 0.836 mmol, 1.00 equiv.) was dissolved in acetonitrile (10 mL), and methyl iodide (0.178 g, 1.25 mmol, 1.50 equiv.) was added dropwise at 25 °C with stirring. The resulting reaction mixture was left for 16 h at 40 oC. The precipitate was collected by filtration and washed with acetonitrile. After dissolving in 10 mL of water, ammonium hexafluorophosphate (0.681 g, 4.18 mmol, 5.00 equiv.) was added, which resulted in a precipitate. The precipitate was collected by filtration, washed with water, and dried. After dissolving the solid in 10 mL of acetonitrile, tetrabutylammonium chloride (1.16 g, 4.18 mmol, 5.00 equiv.) was added, which resulted in a precipitate. The precipitate was collected by filtration, washed with acetonitrile, and dried. The desired product 3-azido-4-(4-(dimethylamino)phenyl)-1-methylpyridin-1-ium chloride was obtained as an orange solid (0.224 g, 0.773 mmol, 92%).
