SYNTHESIS OF PYRAZOLONES FROM α-KETO AND α-CYANO ESTERS

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Abstract
1,4-Dimethyl-3-amino-5-pyrazolone and 4-methyl- and 4-ethyl-3-amino-1-phenyl-5-pyrazolones were synthesized from α-keto esters and methyl- and phenylhydrazines. The hydrazones first obtained were transformed into pyrazolones having a carbethoxy group in position 3, which was converted into an amino group by a Curtius degradation. 2,4-Dimethyl-3-amino-5-pyrazolone was obtained directly from methylhydrazine and ethyl α-cyanopropionate. A series of 3-imino-2-methyl-5-pyrazolones monosubstituted in position 4 with pentyl, hexyl, heptyl, and octyl groups and another series disubstituted in position 4 with butyl, hexyl, and heptyl groups were also prepared from the corresponding mono- and disubstituted cyanoacetates and methylhydrazine.The ultraviolet absorption spectra were determined in neutral and acid medium.