Multinuclear NMR (1H,13C,15N,17O) studies of intramolecular interactions in 1-vinylpyridones and quinolones

Афонин, А. В.; Vashchenko, Alexander V.; Andriyankov, M. A.; Воронов, В. К.; Enikeeva, E. I.; Dmitrieva, L. L.

doi:10.1007/bf00957845

Russ Chem Bull

1990

DOI: 10.1007/bf00957845

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Multinuclear NMR (1H,13C,15N,17O) studies of intramolecular interactions in 1-vinylpyridones and quinolones

А. В. Афонин

Alexander V. Vashchenko

M. A. Andriyankov

et al.

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“…As other indicators of the conformational equilibrium in vinyl chalcogenides serve the difference between the chemical shifts of the β-protons of the vinyl group (Δδ = δН В -δН А ) and the chemical shift δН Х , whereas the decrease in the fi rst parameter corresponds to the larger population of the s-cis-conformation, and of the second, of the s-trans-conformation [6,10,11]. The direct comparison of parameters Δδ and δН Х in vinyl selenide I and vinyl sulfi de II is complicated by the infl uence of the essentially different electronic effect of selenium and sulfur.…”

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Through space spin-spin coupling 19F-1H as the base for comparative analysis of conformational equilibrium in fluorine-substituted aryl vinyl selenides and sulfides

Afonin

2010

Russ J Org Chem

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The analysis of long-range spin-spin coupling 19 F-1 H and the other conformation-dependent parameters of 1 Н NMR spectra shows that aryl vinyl selenides like aryl vinyl sulfi des exist as mixtures of s-cis and s-trans rotational isomers. The combined data of 1 Н and 13 С NMR spectra reveal the increase in the torsional angle ϑ at the bond Х-СН=СН 2 (Х = S, Se) in selenides compared to sulfi des due to diminished interaction energy of the unshared electron pairs of selenium with the π*-orbitals of the double bond as compared to analogous interaction in sulfi des.In the course of recent decades the phenomenon of the rotational isomerism in vinyl chalcogenides was subjected to thorough study by means of versatile physicochemical methods and quantum-chemical calculations [1, 2]. These investigations made it possible to estimate reliably the quantitative content and to study the features of the spatial arrangement of various conformers of vinyl ethers and sulfi des possessing a wide range of substituents. At the same time the rotationsl isomerism in vinyl selenides was considered only occasionally due to the limited number of the synthetically available compounds. In [3] the rotational isomerism of methyl vinyl selenide was studied by the temperature dependence of the characteristic absorption bands in the IR spectra. It was demonstrated that the methyl vinyl selenide existed as a mixture of rotatonal isomers among which the most stable was the fl at s-cisconformer [3]. This conclusion was later confi rmed by quantum-chemical calculations on the level MP2/6-31(d) that revealed the presence of the main minimum on the curve of potential energy of internal rotation corresponding to the s-cis-form [4]. The second minimum of the methyl vinyl selenide corresponded to two degenerate gauche-forms divided by a relatively small energy barrier (~0.5 kcal mol -1 ) in the region of s-trans-form [4].The quantum-chemical calculation on the level MP2/6-311(d,р) and the analysis of coupling constants 77 Se-1 H in divinyl selenide revealed that this compound exists as three rotational isomers: non-fl at s-cis/s-trans and two non-fl at s-trans/s-trans distinguished by the values of the torsional angles at the Se-C bonds [5]. Therewith the s-cis/s-trans-form is considerably more populated [5]. No data appeared in publications up till now concerning vinyl selenides with other substituents. In this study the rotational isomerism in aryl vinyl selenides was studied by the analysis of parameters of 1 H and 13 С NMR spectra.We formerly reported on a presence in the fl uorinesubstituted aryl vinyl sulfi des of a through-space longrange spin-spin coupling 19 F-1 H involving the protons of the vinyl group indicating that these compounds existed as a mixture of s-cis-and s-trans-rotational isomers [6]. The previously performed synthesis of 1,4-divinylseleno-2,3,5,6-tetrafl uorobenzene (I) [7] provided a possibility to apply this molecule as an object of such study in the series of aryl vinyl selenides. The parameters of 1 Н and 13 С spectra of t...

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Through space spin-spin coupling 19F-1H as the base for comparative analysis of conformational equilibrium in fluorine-substituted aryl vinyl selenides and sulfides

Afonin

2010

Russ J Org Chem

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Multinuclear NMR (1H,13C,15N,17O) studies of intramolecular interactions in 1-vinylpyridones and quinolones

Cited by 1 publication

References 5 publications

Through space spin-spin coupling 19F-1H as the base for comparative analysis of conformational equilibrium in fluorine-substituted aryl vinyl selenides and sulfides

Through space spin-spin coupling 19F-1H as the base for comparative analysis of conformational equilibrium in fluorine-substituted aryl vinyl selenides and sulfides

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