Spectroscopic effects and intramolecular interactions in the1H and13C NMR spectra of five-membered N-vinyllactams

Influence of the C—H· · ·N intramolecular interaction on the spatial structures and 1H and 13C NMR parameters of heteroaryl vinyl ethers and sulfides

“…p-Conjugation in the sulfides 22-43 is much less because of the less favorable condition for the 3p-conjugation 18 and depends on their spatial structure. 19 The s-trans orientation of the vinyl group relative to the heterocycle was generally detected in the ethers 1-21.…”

Long-range 19F-1H spin-spin coupling as an indication of conformational equilibrium of fluoro-substituted aryl vinyl sulfides

“…Hetaryl vinyl sulfides exist preferentially as s-trans conformers due to specific intramolecular interactions, and the H B proton therein resonates in a weaker field as compared to H A (the value Δδ = δH B -δH A is positive) [5,6]. Increase in the population of the s-cis conformer of vinyl sulfides having an aromatic ring on the sulfur atom may be judged by decrease of the parameter Δδ, which is positive when s-trans conformer prevails and negative when conformational equilibrium includes an appreciable fraction of s-cis conformer [5,6].…”

“…On the other hand, there are no published data on rotational isomerism in the series of aryl vinyl sulfides, though electronic structure of these compounds was examined on the basis of their 13 C NMR spectra [4]. Furthermore, 1 H and 13 C NMR studies on hetaryl vinyl sulfides revealed some conformation-related parameters which can be used to identify predominant spatial configuration [5,6].…”

“…On the other hand, there are no published data on rotational isomerism in the series of aryl vinyl sulfides, though electronic structure of these compounds was examined on the basis of their 13 C NMR spectra [4]. Furthermore, 1 H and 13 C NMR studies on hetaryl vinyl sulfides revealed some conformation-related parameters which can be used to identify predominant spatial configuration [5,6].We previously synthesized several fluoro-substituted aryl vinyl sulfides [7,8] which were used as initial compounds in the synthesis of a large number of more complex derivatives possessing an analogous fragment [9][10][11][12][13]. These compounds clearly displayed in the 1 H NMR spectra long-range spin-spin couplings between 19 F nuclei and proton in the α-position of the vinyl group, and the observed couplings were used to identify regioisomers [10,11].…”

Dependence of geminal1H−1H and31P−1H spin-spin coupling constants on the specific intramolecular C−H...X interaction

“…It is of interest to consider the physical meaning of the change in the jDSO For the two nuclei (N and M) interacting with each other, jDso is defined by formula (2): Is .__f ) I \ (2) where s and F• are radius vectors of the i-th electron relative to the N and M nuclei, respectively, and q)i is its wave function. The geometric peculiarity of the operator of diamagnetic spin-orbital interaction is that its value inside the sphere of the diameter equal to the distance between the N and M nuclei is negative; however, its value is positive outside this sphere.…”