Example 22 Synthesis of 1,2,4-triazin-3-amine (16): an aqueous solution of glyoxal (57 kg, 40 wt% aqueous, 393 mol, 0.73 eq.) was slowly added to a suspension of aminoguanidine bicarbonate (73 kg, 536.3 mol) in water (400 L) and the reaction was carried out at room temperature. Immediately after addition, the release of carbon dioxide (CO2) gas was observed. The reaction mixture was stirred continuously at room temperature for 18 hours, and the gas release essentially stopped after about 2 hours. Upon completion of the reaction, the mixture was separated by filtration and the filtrate was evaporated to dryness under reduced pressure. The resulting residue was extracted with cold methanol (MeOH, 3 x 120 L) and the combined methanol extracts were cooled to 0-5 °C to remove insoluble solids. Subsequently, the filtrate was concentrated under reduced pressure and the residue was recrystallized in acetonitrile to give the final 1,2,4-triazin-3-amine (16, 34 kg, theoretical yield 37.76 kg, 90% yield) as fine white needle-like crystals.
