[NH2:1][NH2:2].C(O)C.[OH:6][C:7]([CH2:18][C:19](=O)[C:20]1[CH:25]=[CH:24][N:23]=[CH:22][CH:21]=1)([C:13]([O:15][CH2:16][CH3:17])=[O:14])[C:8](OCC)=[O:9].Cl.NN>CO.C(O)CO.N1C=CC=CC=1.O1CCCC1.O1CCOCC1.C(O)(C)C>[OH:6][C:7]1([C:13]([O:15][CH2:16][CH3:17])=[O:14])[CH2:18][C:19]([C:20]2[CH:25]=[CH:24][N:23]=[CH:22][CH:21]=2)=[N:2][NH:1][C:8]1=[O:9]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.
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