Reinvestigation of the tautomerism of some substituted 2-hydroxypyridines

Forlani, Luciano; Cristoni, Giampiero; Boga, Carla; Todesco, P. E.; Vecchio, Erminia Del; Selva, Simona; Monari, Magda

doi:10.3998/ark.5550190.0003.b18

Cited by 84 publications

(66 citation statements)

References 16 publications

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“…Figure 6 shows the optimized geometry for isolated enol-and keto-dimers using Gaussian B3LYP/6-311++G(d,p) along with those in a unit cell (CASTEP; PBEsol). In agreement with the reported X-ray crystal structure, [20] the result of calculations favors the keto-dimer rather than the enol-dimer by 1941-2091 cm À1 (5.55-5.98 kcal/mol). In addition, the energy of keto dimer is found lesser than a duplicate of a monomer, in which the dimer unit is found more stable by 18.93 kcal/mol.…”

Section: Keto-enol Tautomerism and Conformational Stabilitysupporting

confidence: 89%

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2‐Hydroxy‐5‐nitropyridine and 5‐nitro‐2‐pyridone: Tautomerism, infrared, Raman, and NMR spectral interpretations, normal coordinate analysis, and DFT calculations

Mohamed

Shaaban

Soliman

et al. 2021

J Chinese Chemical Soc

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Raman (3700-50 cm À1 ) and infrared (IR) (4000-230 cm À1 ) spectra of 2-hydroxy-5-nitropyridine (HNP; C 5 H 4 N 2 O 3 ) have been recorded in the solid phase in addition to 1 H, 13 C, and 15 N nuclear magnetic resonance (NMR) spectra of the sample in dimethyl sulfoxide-d 6 (DMSO-d 6 ). Initially, keto and enol tautomeric forms were proposed owing to proton transfer from the hydroxyl group to pyridine nitrogen atom. Quantum mechanical calculations based on density functional theory (DFT; B3LYP, ωB97XD, and mPW1PW91) were carried out using 6-31G(d) and 6-311++G(d,p) basis sets favoring keto-NPO, 5-nitro-2-pyridone, tautomer by $0.857-1.345 kcal/mol with minor enol-HNP in the gas phase. Moreover, 1 H, 13 C, and 15 N NMR chemical shifts were predicted using gauge-invariant atomic orbital-DFT calculation at 6-311++G (d,p) basis set using integral equation formalism of the polarization continuum solvation model including solvent effects. The calculated chemical shifts and spin-spin coupling constants (J HH ) for keto tautomer better resemble those experimentally observed rather than the enol form. The observed IR/Raman bands were assigned quantitatively to their normal modes based on the calculated vibrational frequencies, force constants in internal coordinates, normal coordinate analysis, and potential energy distributions. Finally, the nitro and hydroxyl barriers to internal rotations were predicted via a relaxed potential energy surface scan using B3LYP/6-311++G(d,p) calculations. The results are reported herein and compared with similar molecules whenever appropriate.

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Section: Keto-enol Tautomerism and Conformational Stabilitysupporting

confidence: 89%

“…For enol/keto dimer, this distance was markedly shorter by 28-38% than the sum of van der Waal radii, [41] which reflect strong inter-molecular H-bonding interactions. Compared to the reported X-ray values, [20] the computed CCC angles were accurate within ±0.2 -1.1 .…”

Section: Structural Parametersmentioning

confidence: 54%

2‐Hydroxy‐5‐nitropyridine and 5‐nitro‐2‐pyridone: Tautomerism, infrared, Raman, and NMR spectral interpretations, normal coordinate analysis, and DFT calculations

Mohamed

Shaaban

Soliman

et al. 2021

J Chinese Chemical Soc

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“…The data for the tautomerism of 1 in solution are also helpful in validating the approach. Such information is available for cyclohexane [41,42], carbon tetrachloride [43] and acetonitrile [42], determined by UV spectroscopy and methylated compounds as references. The corresponding ∆G o values are 0.3, 1.3 and 2.7 kcal/mol respectively, which *Difference between the total energies of the enol and keto forms (∆E = E E − E K ), negative value indicates more stable enol form and vice versa **Presented as the most stable isomer ***Orientation of the CONH 2 group corresponds exactly to the crystal structure of T-705-ribonucleoside as reported in [25] indicates predominance of the keto tautomer as predicted by the calculations.…”

Section: Resultsmentioning

confidence: 99%

Favipiravir tautomerism: a theoretical insight

Antonov

2020

Theor Chem Acc

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There is no experimental information about the tautomerism of Favipiravir (T-705). Therefore, its tautomeric state was predicted by using density functional theory in gas phase and in solution (toluene, acetonitrile and water). The results have shown that, in neutral state, the enol form is strongly dominating in both gas phase and solution. The carboxamide group is easily protonated in the presence of acid, which leads to shift of the tautomeric equilibrium toward the keto tautomer. In order to validate the theoretical predictions, 2-hydroxy pyridine and 2-hydroxy pyrazine were also included in the set of studied compounds. The available experimental data about their tautomerism are in very good agreement with the theoretical predictions, which validate the conclusions made for T-705.

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“…The data for the tautomerism of 1 in solution are also helpful in validating the approach. Such information is available for cyclohexane 48,49 , carbon tetrachlode 50 and acetonitrile 49 , determined by UV spectroscopy and methylated compounds as references. The corresponding values of ∆G are 0.3, 1.3 and 2.7 kcal/mol respectively, which indicates predominance of the keto tautomer as predicted by the calculations.…”

Section: Resultsmentioning

confidence: 99%

Favipiravir Tautomerism: A Short Theoretical Report

Antonov¹

2020

Preprint

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There is no experimental data about the tautomerism of Favipiravir (T-705). Therefore its tautomeric state was predicted by using density functional theory in gas phase and in solution (toluene, acetonitrile and water). The solvent effect was described by means of the Polarizable Continuum Model. The results have shown that the enol form is strongly dominating in both gas phase and solution. In order to validate the theoretical predictions, 2-hydroxy pyridine and 2-hydroxy pyrazine were also included in the set of studied compounds. The available experimental data for their tautomerism are in very good agreement with the theoretical predictions, which validate the conclusions made for T-705.

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Reinvestigation of the tautomerism of some substituted 2-hydroxypyridines

Cited by 84 publications

References 16 publications

2‐Hydroxy‐5‐nitropyridine and 5‐nitro‐2‐pyridone: Tautomerism, infrared, Raman, and NMR spectral interpretations, normal coordinate analysis, and DFT calculations

2‐Hydroxy‐5‐nitropyridine and 5‐nitro‐2‐pyridone: Tautomerism, infrared, Raman, and NMR spectral interpretations, normal coordinate analysis, and DFT calculations

Favipiravir tautomerism: a theoretical insight

Favipiravir Tautomerism: A Short Theoretical Report

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