Tautomers and polymorphs of pyrazolinone derivatives, generated from reactions of arylhydrazines, ArNHNH 2 , with 1,3-dicarbonyl compounds (original) (raw)
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Tetrahedron, 1997
I-Substituted 4-alkoxy-, 4-alkylthio-, and 4-aryloxy-lH-pyra~,x~l-5(2/-/)-ones have been prepared by the reaction of conjugated az~mlkene, s with "alot~ols, thiols, and phenols. In some cases the intermediate hydrazones were isolated, while in others the products were obtained in one step. I-Unsubstituted 4-alkoxy-, 4-alkylthio-, and 4-aryloxy-IH-pyra~'d-5(2H)-ones were t~rodueed by methanolysis of the corresponding l-substituted derivatives under reflux. Some of these compounds were studied by molecular mechanics calculations, as well as deuterium induced shills (DIS) on 13C chemical shifts, and tentative conclusion was drawn about their tautomerism and conformatiems. X-Ray crystal structure determinations of 1-(aminocarbonyl)-3-methyl~l-methoxy-1H-pyra/x~l-5(2/-/)-one 4e and 3-methyl-4-methoxy-IH-pyraJx~l-5(2H)-one $1 demonstrated thai both molecules Exist in the cr3,stal exclusively in the HN-CO tautomeric form. Some I~revi~vasly relXWted structural assignments in ~me pyra~,x~km~s and hydmxypyrazoles were ccm~ected,
Tetrahedron, 2008
Three series of 3,7-bis(arylazo)-6-methyl-2-phenyl-1H-imidazo-[1,2-b]pyrazoles were prepared starting from N-aryl 2-oxo-2-phenylethanehydrazonoyl bromides and 5-amino-4-arylazo-3-methyl pyrazoles. The acid dissociation constants pK and pK* in both the ground and excited states, respectively, were determined and correlated with the Hammett equation. The results of such correlations together with the spectroscopic data indicated that the title compounds exist predominantly in the 1H-bis(arylazo) form in both ground and excited states.
Acta crystallographica. Section C, Structural chemistry, 2015
The molecular structures of (E)-1-(4-{[1-(4-fluorophenyl)-3,5-dimethyl-1H-pyrazol-4-yl]diazenyl}phenyl)ethanone, C19H17FN4O, (III), and (E)-1-(4-chlorophenyl)-3,5-dimethyl-4-[2-(2-nitrophenyl)diazenyl]-1H-pyrazole, C17H14ClN5O2, (IV), prepared by reaction of the corresponding β-diketohydrazones with substituted arylhydrazines in acid media, are nonplanar, with the planes of the lateral phenyl rings forming dihedral angles with that of the central pyrazole ring varying from 2.71 (7) to 45.22 (7)°. The crystal structures are supported by C-H...O, C-H...π and π-π weak intermolecular interactions together with some unusual trifurcated C-Cl...Cl-C contacts, which are discussed in detail.
Synthesis and Tautomerism of Substituted Pyrazolo[4,3-c]pyrazoles
Keywords: Nitrogen heterocycles / Tautomerism / Low-temperature NMR spectroscopy / Electronic and steric effects / DFT calculations Fused five-membered nitrogen heterocycles comprise a very important group of compounds frequently utilized in pharmaceutical applications. In this study, we report the first systematic synthesis of substituted pyrazolo[4,3-c]pyrazoles and three regioisomers of their N-methyl derivatives. All compounds were fully characterized by NMR spectroscopy in solution and selected compounds also were studied by X-ray diffraction in the solid state. 1 H, 13 C, and 15 N NMR spectroscopic data for all isomers were interpreted by DFT calculations of nuclear shielding constants and indirect spin-spin coupling constants. The N-methyl isomers were used in the [a] Scheme 2. Synthesis of substituted pyrazolopyrazoles 21 and 22 from ethyl oxalate, and 31 from ethyl acetoacetate. Scheme 3. Synthesis of N-methylated pyrazolo[4,3-c]pyrazole analogues and thermal decarboxylation of the pyrazolo[4,3-c]pyrazole 21.
Molecules (Basel, Switzerland), 2018
The tautomerism of 1-phenyl-1,2-dihydro-3H-pyrazol-3-One was investigated. An X-ray crystal structure analysis exhibits dimers of 1-phenyl-1H-pyrazol-3-ol units. Comparison of NMR (nuclear magnetic resonance) spectra in liquid state (¹H, 13C, 15N) with those of "fixed" derivatives, as well as with the corresponding solid state NMR spectra reveal this compound to exist predominantly as 1H-pyrazol-3-ol molecule pairs in nonpolar solvents like CDCl₃ or C₆D₆, whereas in DMSO-d₆ the corresponding monomers are at hand. Moreover, the NMR data of different related 1H-pyrazol-3-ol derivatives are presented.
ChemInform Abstract: Pyrazol-5-ones: Tautomerism, Synthesis and Reactions
ChemInform, 2013
This review summarizes results from the literature concerning on tautomerism, synthetic approaches and chemical properties of title compounds as well as their chemical reactions since the pyrazolone chemistry began in 1883 by Ludwig Knorr to date are reported. Emphasis is placed on pinpoining old literature reports that need reinspection in light of modern techniques. The most eye catching features of this structure are their greatest utility resides in pharmaceuticals (analgesic, antibacterial, antifungal, antagonists, antiinflammatory, antimicrobial, antidiabetic, antihyperglycemic and anxiolytic), agrochemicals, dyes (textile and photography), and to a lesser extent in analytical chemistry are discussed with the help of adequate examples.
X-ray diffraction analysis and spectral studies of new derivatives of pyrazol-5-one
Russian Chemical Bulletin, 1999
The molecular and crystal structures of 4-acetamido-2,3-dimethyl-l-phenylpyrazol-5-one (1) and 4-nmteylamido-2,3-dimethyl-l-phenylpyrazol-5-one (2) were studied. The molecular conformations are stabilized via systems of intermolecular hydrogen bonds between the amide groups and the carbonyl oxygen atoms of the pyrazolone rings. The conformation of compound 2 is additionally stabilized via an intramolecular interaction between the carboxyl group and the amide oxygen atom. According to the I R spectral data, protonation of the compounds under sttldy in an acetonitrile solution occurs at the carbonyl oxygen atom of the pyrazolone ring, which is also confirmed by the UV spectral data.
Synthesis and Characterization of Some Compounds containing Pyrazole Moiety
Journal of University of Anbar for Pure Science
This study includes the preparation of some heterocyclic compounds compact of the Pyrazole, work is done in three steps. First step, treatment of acetophenone derivatives with DMF-DMA for the preparation of the first compound (2E)-1-(R phenyl)-3-(dimethylamino)prop-2-en-1-one , (R) is one of the derivatives used for acetophenone (R = Br, NH 2). The second step, treatment of benzaldehyde derivatives with hydrazine to prepare the second compound in the series (1E)-(R benzylidene) hydrazine, where (R) is one of the derivatives used for benzaldehyde to get the Shiff bases. And the third step, treatment of the first step products with the products of the second step. Each product from the first step gives us a series of Pyrazole compounds with its reaction with products of the second step interaction after the other. Thus, we can bring a number of compounds, the sum of the first step products multiplied by the products of the second step. The third-step reaction is a ring-blocking reaction to form a combined heterogeneous ring of Pyrazole. Finally, characterization these compounds with infrared spectra, NMR spectrum and mass spectrometry.
Studies on pyrazinyl-pyrazylidene tautomerism of pyrazine-acetonitrile derivatives
Monatshefte für Chemie Chemical Monthly, 1984
The equilibria between the pyrazinyl and 2(1H)-pyrazylidene ibrms of pyrazineacetonitrile derivatives were studied by II~, ~H-NMR and UV spectroscopy. The excess charges and dipole moments for the two tautomers were calculated by the CNDO/2-MO method. (Keywords: CNDO/2-MO; IR; PMR; UV) Untersuchungen iiber die Pyrazinyl-Pyraziliden-Tautomerie von Pyrazinacetonitril-Derivaten Die Gleiehgewichte zwischen Pyrazinyl-und 2(1H)-Ps~azyliden-Formen yon Pyrazinacetonitril-Derivaten warden mittels It£-, PMR-und UV-Spektroskopie untersueht. Die LTberschuBladungen und Dipolmomente der zwei Tautomeren wurden nach dem CNDO/2-MO-Verfahren berechnet.