Methyl iodide → 6-chloro-2-methyl[1,2,4]triazolo[4,3-b]pyridazin-3(2H)-one

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To a solution of 6-chloro-2,3-dihydro-s-triazolo[4,3-b]pyridazin-3-one [P. Francavilla and F. Lauria, J. Het. Chem. 8, 415 (1971)] (1, 8.5 g., 50 m.mol.) in dry DMF (12 ml.) was added NaH (50% dispersion in paraffin, 2.64 g., 55 m.mol) and the mixture was stirred for 1 hour at room temperature. After methyl iodide (21.3 g., 150 m.mole) was added, the mixture was stirred for 40 hours at room temperature, diluted with water (200 ml.) and extracted with CHCl3 (4 × 100 ml.). The combined extracts were washed with water (3 × 50 ml.), treated with a small amount of carbon and dried with anhydrous Na2SO4. Evaporation of the solvent under reduced pressure afforded pale yellow residue which was crystallized from chloroform-n-hexane. Yield: 7.23 g. (79%). M.p. 180°-181° C.

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