The general procedure for the synthesis of 3-amino-4,6-dibromopyridazine from 3-amino-6-bromopyridazine was as follows: first, 285 g (1638 mmol) of 6-bromopyridazin-3-amine was dissolved in 2815 mL of methanol, and 275 g (3276 mmol) of sodium bicarbonate and 85 mL (1638 mmol) of bromine were added slowly and dropwise at room temperature. The reaction mixture was stirred at room temperature overnight. Subsequently, 34 mL (655 mmol) of bromine and 55 g (655 mmol) of sodium bicarbonate were added supplementally to the reaction system and stirring was continued overnight at room temperature. Upon completion of the reaction, the solvent was concentrated under reduced pressure to about 1000 mL and the mixture was slowly poured into 5 L of water. The precipitate was collected by filtration, washed with water and dried to give 411 g (99% yield) of the target product 3-amino-4,6-dibromopyridazine. The structure of the product was confirmed by 1H-NMR (CDCl3) with chemical shifts of δ = 6.14 (1H), 9.92 (2H) ppm.
