Quantum chemical studies on tautomerism of 2-, 3- or 4-hydroxyquinoline derivatives along with their thio and azo analogs

Tokay, Nesrin; Öğretır, Cemi̇l

doi:10.1016/s0166-1280(02)00390-1

Cited by 27 publications

(8 citation statements)

References 12 publications

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“…On-line analysis of nine peaks led to identification of six new and two known 4-quinolinone alkaloids as well as a hemiterpenoid 2-quinolinone alkaloid and a lignan. In agreement with earlier investigations of tautomeric equilibria between hydroxyquinolines and quinolinones in solution (de la Cruz et al, 1992;Mphahlele and El-Nahas, 2004;Tokay and Ögretir, 2002), the alkaloids are formulated as quinolinones. The finding of six new 2-alkylquinolinones in extract of aerial parts of H. acutifolium shows that reinvestigation of plants with new and more sensitive technology can add considerable new phytochemical information to already well-investigated species.…”

Section: Resultssupporting

confidence: 89%

Accelerated dereplication of crude extracts using HPLC–PDA–MS–SPE–NMR: Quinolinone alkaloids of Haplophyllum acutifolium

et al. 2009

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Direct hyphenation of analytical-scale high-performance liquid chromatography, photo-diode array detection, mass spectrometry, solid-phase extraction and nuclear magnetic resonance spectroscopy (HPLC-PDA-MS-SPE-NMR) has been used for accelerated dereplication of crude extract of Haplophyllum acutifolium (syn. Haplophyllum perforatum). This technique allowed fast on-line identification of six quinolinone alkaloids, named haplacutine A-F, as well as of acutine, haplamine, eudesmine, and 2-nonylquinolin-4(1H)-one. Acutine and haplacutine E, isolated by preparative-scale HPLC, showed moderate antiplasmodial activity with IC(50) values of 2.17+/-0.22 microM and 3.79+/-0.24 microM, respectively (chloroquine-sensitive Plasmodium falciparum 3D7 strain).

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Section: Resultssupporting

confidence: 89%

Accelerated dereplication of crude extracts using HPLC–PDA–MS–SPE–NMR: Quinolinone alkaloids of Haplophyllum acutifolium

et al. 2009

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“…Further evidence for the preferred stability of lactim forms comes from computational studies. 20 Table 4 reports the effect of the changes of the temperature on [B]/[A] ratios in a mixed solvent (THF/H 2 O). The spectroscopic data obtained at different temperatures, for compounds 4 and 6 in THF/water mixtures indicate that the equilibrium is strongly affected by changes in temperature.…”

Section: Issn 1424-6376mentioning

confidence: 99%

Reinvestigation of the tautomerism of some substituted 2-hydroxypyridines

Forlani¹,

Cristoni²,

Boga³

et al. 2002

Arkivoc

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The tautomerism of some substituted 2-hydroxypyridines is investigated by UV/Vis-and 1 H-, and 13 C-NMR spectroscopic methods, with the aid of the N-Me and O-Me fixed parents. NMR spectroscopic data do not allow discrimination between the two tautomeric forms (with the exception of the unsubstituted 2-hydroxypyridine), while UV/Vis-data permit the quantitative determination, in different solvents, of the amounts of the two forms. The electronic substituent effect and the change of solvent are discussed. An X-Ray diffraction study carried out on a crystal of 2-hydroxy-5-nitropyridine (7) reveals that this compound, in the solid state, is in the oxo-form.

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“…The OH and aza groups may also be involved in the keto‐enol tautomeric equilibrium. Rotation barriers, intramolecular hydrogen bonding, and solvent effects have been carried out on hydroxyquinoline by density functional theory (DFT) . Filip et al.…”

Section: Introductionmentioning

confidence: 99%

“…studied the molecular structure of 8‐hydroxyquinoline using B3LYP/6‐31+G and PM3 semiempirical methods . On the other hand, Tokay and Ogretir studied tautomerism of 2,3 or 4‐hydroxyquinoline derivatives along with their thio analogs . Theoretical studies on proton transfer reactions of 8‐hydroxyquinoline monomers and dimers have been done .…”

Section: Introductionmentioning

confidence: 99%

A thermochemistry and kinetic study on the thermal decomposition of ethoxyquinoline and ethoxyisoquinoline

El‐Demerdash

El-Gogary

El‐Nahas

2018

Int J of Chemical Kinetics

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Quantum chemical calculations were used to study the production of ethylene and keto/enol tautomers from ethoxyquinoline (2-EQ) and ethoxyisoquinoline (1-EisoQ and 3-EisoQ) in the gas phase and ethanol at the MP2/6-311++G(2d,2p)//BMK/6-31+G(d,p) level. The obtained data indicate that the elimination of ethylene from 1-EisoQ and 2-EQ is slightly more favorable than from 3-EisoQ. Formation of quinolone and isoquinolone (2-EQO, 1-EisoQO, and 3-EisoQO) is kinetically favored compared to their enols. Decomposition of 2-EQ and 1-EisoQ to ethylene and keto forms is thermodynamically and kinetically preferable more stable than the corresponding enols. However, the hydroxy form of 3-EisoQ is more stable than its keto tautomer in the gas phase and ethanol. The enol tautomers cost less energy when formed from their keto forms rather than from the parent ethoxyquinolone and ethoxyisoquinoline. K E Y W O R D SBMK and MP2, ethoxyisoquinoline, ethoxyquinoline, ethylene formation, potential energy surface 604

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Quantum chemical studies on tautomerism of 2-, 3- or 4-hydroxyquinoline derivatives along with their thio and azo analogs

Cited by 27 publications

References 12 publications

Accelerated dereplication of crude extracts using HPLC–PDA–MS–SPE–NMR: Quinolinone alkaloids of Haplophyllum acutifolium

Accelerated dereplication of crude extracts using HPLC–PDA–MS–SPE–NMR: Quinolinone alkaloids of Haplophyllum acutifolium

Reinvestigation of the tautomerism of some substituted 2-hydroxypyridines

A thermochemistry and kinetic study on the thermal decomposition of ethoxyquinoline and ethoxyisoquinoline

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