反应详情

The preparation of lower-alkyy 2,3-dihydro-2-R-3-oxo-6-PY-4-pyridazinecarboxylates by reacting di-(lower-alkyl)hydroxy[2-oxo-2-PY-ethyl]propanedioate (II) with a hydrazine salt of the formula RNHNH2.nHxAn (III), where PY and R are defined as in formula I above and n, x and An are defined as in formula III above, is carried out by heating the reactants at about 60° C. to 100° C., preferably about 75° C. to 85° C., and preferably in the presence of a suitable solvent, e.g., a lower-alkanol such as methanol, ethanol or isopropyl alcohol. Other suitable solvents would be dioxane, tetrahydrofuran, pyridine, ethylene glycol, and the like. Preferred R-hydrazine salts are the dihydrochlorides or sulfates. This preparation is illustrated below in Examples C-2 through C-17. Also note Example B-1 where diethyl hydroxy[2-oxo-2-(4-pyridinyl)ethyl]propanedioate was refluxed with hydrazine monohydrochloride in methanol for a relatively short period (less than 2 hours) to produce ethyl 2,3,4,5-tetrahydro-4-hydroxy-3-oxo-6-(4-pyridinyl)-4-pyridazinecarboxylate which, as shown in Example C-1, was readily dehydrated by treating a solution of it in a suitable solvent, e.g., acetonitrile, ethanol, tetrahydrofuran or dioxane with hydrogen chloride to produce ethyl 2,3-dihydro-3-oxo-6-(4-pyridinyl)-4-pyridazinecarboxylate.

1. temperatureby heating the reactants at about 60° C. to 100° C.
2. custompreferably about 75° C. to 85° C.
3. custom(less than 2 hours)