Water → 6-(3,5-difluorophenyl)-2-[3-(5-oxo-4,5-dihydro-1,3,4-oxadiazol-2-yl)benzyl]-2H-pyridazin-3-one

7.2 A solution of 131 mg (0.65 mmol) of trichloromethyl formate in 3 ml of dioxane is added to a suspension of 178 mg (0.50 mmol) of 3-[3-(3,5-di-fluorophenyl)-6-oxo-6H-pyridazin-1-ylmethyl]benzohydrazide in 1 ml of dioxane, and the mixture is heated at the boil for 4 hours. The reaction mixture is allowed to cool, and water is added. The resultant precipitate is filtered off with suction, washed with water and dried. The residue is chromatographed on a silica gel column with dichloromethane/methanol, giving 6-(3,5-difluorophenyl)-2-[3-(5-oxo-4,5-dihydro-1,3,4-oxadiazol-2-yl)benzyl]-2H-pyridazin-3-one (“A15”) as colourless crystals; ESI 383;