Synthesis
General procedure for the synthesis of 4,5-diaminopyridazine from 3,6-dichloro-5-nitropyridazin-4-amine:
1. Pd/C (5%, 5 g) was added to a methanol (MeOH, 1000 ml) solution of intermediate 11 (17 g, 81.7 mmol, 1 equiv).
2. The reaction mixture was stirred at 25 °C under 50 psi hydrogen atmosphere overnight.
3. Upon completion of the reaction, the catalyst was removed by filtration through a diatomaceous earth pad.
4. The solvent was evaporated under reduced pressure to give Intermediate 12 (15 g, 100% crude yield).
Step 3: Synthesis of pyridazine-4,5-diamine (13)
1. potassium carbonate (22.6 g, 164 mmol, 2 eq.) was added to intermediate 12 (15 g, 82 mmol, 1 eq.) in a solvent mixture of methanol (MeOH, 150 ml) and dichloromethane (CH2Cl2, 150 ml).
2. The reaction mixture was stirred at room temperature overnight.
3. The reaction mixture was filtered and the filtrate was concentrated under reduced pressure to give Intermediate 13 (9 g, 95% yield).
