5754-17-6

34584-69-5

General procedure for the synthesis of 3,6-dichloro-4,5-dimethylpyridazine from 4,5-dimethylpyridazine-3,6-dione: A mixture of 6-hydroxy-4,5-dimethyl-2H-pyridazin-3-one (2.56 g, 18 mmol), phosphorus trichloride (8 mL), and diisopropylethylamine (4 mL) was placed in a microwave reactor (Biotage MW oven) and The reaction was stirred at 160 °C for 20 min. Upon completion of the reaction, the solvent was partially evaporated under reduced pressure and the residue was poured into a mixture of cold water, saturated sodium bicarbonate solution and methylene chloride. The mixture was alkalized with saturated sodium bicarbonate solution until no CO2 gas was released. The organic layer was separated, dried over anhydrous sodium sulfate, filtered and the solvent concentrated under reduced pressure. The residue was purified by column chromatography (eluent: dichloromethane/heptane, ratio tapered from 1/1 to 10/0) to afford the target product 3,6-dichloro-4,5-dimethylpyridazine (D9) (1.7 g, 53% yield) as a solid. Elemental analysis: theoretical value 176 for C6H6Cl2N2; measured value 177 (MH+).