1073525-71-9

1073525-70-8

1073525-71-9

General procedure for the synthesis of 3,4-dibromo-6-(trifluoromethyl)pyridazin-3(2H)-one from 4-bromo-6-(trifluoromethyl)pyridazin-3(2H)-one: 4-bromo-6-(trifluoromethyl)pyridazin-3-ol (D3) (4.0 g, 16.4 mmol) was mixed with tribromophosphorus oxide (28.2 g, 98.4 mmol) and the reaction was stirred for 4 hours at 60 °C. After completion of the reaction, the reaction mixture was slowly poured into an ice-water mixture, diluted with dichloromethane and neutralized with saturated sodium bicarbonate solution. The organic layer was separated and dried with anhydrous magnesium sulfate followed by evaporation of the solvent under reduced pressure. The crude product was purified by fast column chromatography (silica gel as stationary phase and dichloromethane containing 3% ammonia in methanol solution (7 M) as eluent). The fraction containing the target product was collected and the solvent was evaporated under reduced pressure to give 3,4-dibromo-6-(trifluoromethyl)pyridazine (D5) (2.28 g, 46% yield) as a solid. Elemental analysis (calculated value C5HBr2F3N2): 305; measured value (MH+): 306.