Water → 6-Chloro-2,3-dihydro-2-ethoxycarbonylmethyl-s-triazolo[4,3-b]pyridazin-3-one

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Reaction Conditions

Reaction Steps

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, 1.00 g., 5.9 m.mole) in dry DMF (30 ml.) was added sodium hydride (50% in paraffin, 0.3 g., 6.3 m.mole) under stirring with formation of yellow crystals. To the mixture was added ethyl chloroacetate (1.4 ml., 13 m.mole) and the mixture was heated at 90° C. for 8 hours with stirring. After cooling, the reaction mixture was poured into water (50 ml) and extracted with toluene (5×40 ml.). The organic extracts were combined, dried over anhydrous sodium sulfate and evaporated at reduced pressure. The residue was crystallized with benzene-n-hexane to give yellow needles of 2 (1.16 g., 77%), m.p. 114°-115° C. (lit. 110° C.).

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