Reactions of unsaturated tetra- and tri-esters with hydrazine hydrate and semicarbazide hydrochloride

Various 4,5-disubstituted pyrazolidin-3-ones (IIc–f) have been isolated as intermediates in the reaction between 3-substituted tetraethyl propene-1,1,3,3-tetracarboxylates (I) and hydrazine hydrate. No such intermediates were obtained in the reaction between 3-substituted triethyl propene-1,1,3-tricarboxylates (VI) and with hydrazine hydrate, which gave ethyl 5-oxo-Δ2-pyrazoline-4-carboxylate (III) and the appropriate saturated esters (VII). Semicarbazide hydrochloride reacted similarly with the various esters to give the same final products as with hydrazine hydrate.