Prototropic isomerization of dihydropyridazinecarboxylic and dihydropyridazinedicarboxylic acid esters
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3,5-Disubstituted 1,4-dihydropyridazine-4-carboxylic and 4,6-disubstituted 2,5-dihydropyridazine-3,5-dicarboxylic acid esters undergo isomerization into 2,5-dihydropyridazine-4-carboxylate and 1,4-dihydropyridazine-3,5-dicarboxylate derivatives, respectively, by the action of a catalytic amount of a mineral acid or strong base at 20°C. The transformation may be regarded as prototropic rearrangement, and it includes two consecutive 1,2-hydride shifts. The direction of the isomerization is determined by higher thermodynamic stability of the isomer containing a β-aminoacrylate fragment.
KeywordsDicarboxylate Sodium Methoxide Potassium Permanganate High Thermodynamic Stability Methyl Diazoacetate
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