Synthetic and Spectrometric Studies of Some Pyrazolones

Abstract

Fourteen pyrazolones were synthesized from the corresponding mono or disubstituted cyanoacethydrazides or cyanoacetphenylhydrazides and evidence concerning their constitution was obtained from chemical reactions and ultraviolet absorption spectra determinations. A mixture of two tautomeric forms was obtained when 4-benzyl-3-amino-5-pyrazolone was prepared; it was converted to a single form by treatment with hydrochloric acid. The following compounds, as far as the authors are aware, have been prepared for the first time: 4-methyl-3-amino-5-pyrazolone, 4-methyl-2-phenyl-3-amino-5-pyrazolone, 4-ethyl-3-amino-5-pyrazolone, 4-ethyl-2-phenyl-3-amino-5-pyrazolone, 4-(2-phenoxyethyl)-3-amino-5-pyrazolone, 4-(2-phenoxyethyl)-2-phenyl-3-amino-5-pyrazolone, 4-(3-phenoxypropyl)-3-amino-5-pyrazolone, 4-(3-phenoxypropyl)-2-phenyl-3-amino-5-pyrazolone, 4-phenyl-3-amino-5-pyrazolone, 4-benzyl-3-amino-5-pyrazolone, 4-benzyl-2-phenyl-3-amino-5-pyrazolone, 4,4-dibenzyl-3-amino-5-pyrazolone, 4, 4-dibenzyl-2-phenyl-3-imino-5-pyrazolone, 4,4-(2,2-spiro-indanyl)-3-amino-5-pyrazolone.

Cyanoacetic Esters, Amino Acids, and Pyrazolones

“…There is evidence that acids catalyze the transfornlation of one tautomeric form (VIII) into the other (IX). This \\.as observed with 4-benzyl-3-amino-5-pyrazolone (9).…”

“…It has been demonstrated that pyrazolones of structure I X like 4-alky1-3-amino-2-phenyl-5-pyrazolones (9) have their ~n a x i~n u m abso&ion in the range from 2350 to 2450 A, whereas pyrazolones of structure VIII like 4-alkyl-3-amino-5-pyrazolones absorb in the range from 2750 to 2850 A (9).…”

“…The 4-n~onosubstituted compounds, however, were more soluble in water than the 4,4-disubstituted ones. The individual properties are given in Table IV. ULTRAVIOLET ABSORP'I'ION SPECTRA The ~~ltraviolet absorption spectra were taken on a Beckman spectrophotometer Model DU in the same \vay as previously described (9). Results are listed in Table I\; For personal use only.…”

“…Most of the substituted cyanoacetic esters used for the preparation of amino acids gave hydrazides which were transformed by treatment with sodium hydroxide into 5-pyrazolones which were extensively studied to determine their structures (6,8,9,10,14,15).…”

Recent advances in the synthesis of polysubstituted 3-pyrazolidinones

“…The first reports on 3-pyrazolidinones date to the 1940s. [1][2][3][4][5][6] Since that time, the importance of 3-pyrazolidinones has risen significantly, due to their applicability in industrial processes and biological activity. So far, progress on 3-pyrazolidinone chemistry has been reviewed by Dorn in 1981, 7 Claramunt and Elguero in 1991, 8 and in part by Svete in 2008.…”