13C NMR spectra and carbon-proton coupling constants of various methylangelicins

The ¹³C-nmr spectra of various methyl derivatives of angelicin are reported. The assignment of chemical shifts for all the C atoms has been achieved by using carbon-proton coupling constants, nuclear Overhauser effect consideration and shift effects caused by the introduction of methyl groups on various positions of the angelicin nucleus. Substituent effects on ¹³C chemical shifts and carbon-proton coupling constants are discussed.     

13C n.m.r. spectra of 2-substituted pyrimidines

¹³C n.m.r. chemical shifts and carbon-proton coupling constants of 2-substituted pyrimidines are reported. The carbon chemical shifts are correlated with π-electron densities. Substituents which cause deshielding at the directly bound carbon (e.g. NH₂, OCH₃ and F) exert a more powerful effect in the benzene series than in the pyridine or pyrimidine series. The carbon-proton coupling constants do not correlate with the electronegativity of the substituents. Carbon-proton coupling constants and proton-proton coupling constants over the same number of bonds do not obey the Karabatsos relationship. The changes in the carbon-proton coupling constants in 2(1H)-pyrimidinone and 2(1H)-pyrimidinethione which accompany anion and cation formation are reported.     

13C NMR spectra of benzothiazepinone,benzothiazinone and benzosulphonamide N-substituted derivatives

A comparative study of the ¹³C NMR spectra of benzothiazinone and benzothiazepinone dioxide derivatives and of some structurally related benzosulphonamides is presented. The size of the heterocyclic ring is reflected in the ¹³C chemical shifts and in the one-bond carbon-proton aromatic coupling constants. An upfield γ-effect of sulphur on the ¹³C chemical shifts in N-substituted carboxyethylbenzene-4,5-dimethoxysulphonamides is reported.     

Furopyridines. XI. 13C NMR Spectra of 2- or 3-Substituted Furo[2,3-b]-, Furo[3,2-b]-, Furo[2,3-c]- and Furo[3,2-c]pyridine

The ¹³C nmr spectra of 2- or 3-monosubstituted furo[2,3-b]- 1a-1j , furo[3,2-b]- 2a-2j , furo[2,3-c]- 3a-3j and furo[3,2-c]pyridine derivatives 4a-4j are reported. Effects by change in annelation and substituent effects on ¹³C chemical shifts and carbon-proton coupling constants are discussed. The spectra of benzo[b]furan derivatives 5a-5j having the corresponding substituent are also reported for comparison.     

Carbon-13 NMR spectroscopy of heterocyclic compounds—IV : A 20 MHz study of chemical shifts and carbon-proton coupling constants in a series of hydroxy,methoxy and glucosyl coumarins

Complete assignments of chemical shifts and extensive assignments of carbon-proton coupling constants are presented for all the monohydroxycoumarins except the 5-derivative, together with similar data for 6,7- and 7,8-dihydroxy-,4- and 7-methoxy-, 7-hydroxy-4-methyl- and 6,7- and 7,8-dihydroxy-4-methyl-coumarins. It is shown that shifts in the polysubstituted molecules can be predicted with high precision from substituent effects evaluated for the more simple derivatives. The approach is extended to some simple glucosyl derivatives, and it is demonstrated that not only the anomeric configuration but also the exact site of the sugar substitution can be determined from ¹³C data.     

13C NMR spectra and three-dimensional structures of isomeric 3,4-substituted thiophans

The chemical shifts and the direct carbon-proton spin-spin coupling constants for a number of cis and trans isomers of 4-amino-substituted 3-hydroxy(acyloxy)-thiophans, the configurations of the substituents in which and the conformational states were previously established by an independent method, were studied. It was found that in the spectra of the cis isomers the signals of the vicinal ¹³C atoms, which bear the substituents, are shifted to strong field as compared with the trans isomers ( trans-cis 1.7–4.3 ppm). Conformational effects of the substituents on the chemical shifts of the ring ¹³C atoms were noted. It is shown that a relationship exists between the direct carbon-proton spin-spin coupling constants and the spatial orientations of the acyloxy and acylamino substituents for five-membered saturated rings.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1612–1616, December, 1981.     

Carbon-13 NMR spectra of some 4- and 5-substituted pyrimidines

Carbon-13 NMR chemical shifts and carbon-proton coupling constants for nine 4-substituted and six 5-substituted pyrimidines are reported. The carbon chemical shifts are correlated with π-electron densities. Carbon-proton coupling constants fail to correlate with substituent electronegativity.     

13C?19F spin–spin coupling in some monofluoro-substituted polycyclic aromatic hydrocarbons

The determination and complete assignment of the ¹³C? ¹⁹F coupling constants and ¹³C chemical shifts for 15 monofluoro derivatives of nine polycyclic aromatic hydrocarbons are reported. Fluorine substitutent effects on the ¹³C chemical shifts are given and their regular behaviour, making comparisons between different compounds possible, is discussed. The numerical values of the ¹³C? ¹⁹F long range coupling constants are found, with a few exceptions, to decrease in an alternating manner along the periphery of the molecules. In several cases the signs of the coupling constants have been determined. It appears that the signs alternate, but additional evidence is required. The magnitudes of different types of coupling constants are discussed in terms of steric and electronic effects. CNDO/2 and INDO calculations of the ¹³C? ¹⁹F coupling constants in the fluoronaphthalenes have been performed using the ‘sum-over-states’ method with the aim of examining the orbital and spin–dipole contributions to the various couplings.     

13C NMR spectra of alkyl- and phenylpyrazines and their N-oxides

The ¹³C chemical shifts of 37 pyrazines, including their N-oxides, are reported. Substituent effects of methyl, phenyl and N-oxide groups on the chemical shifts were examined. To comprehend these effects, the chemical shifts were compared with charge densities calculated by the CNDO/2 method and a good correlation was obtained. ¹³C, ¹H coupling constants of some pyrazines were also determined and assigned. These data enable us to assign the ¹³C NMR spectra of substituted pyrazines and to understand the effects of N-oxidation on the pyrazine nuclei.     

1H and13C NMR spectra and structure of 2,3,4-trisubstituted sulfolanes

Conclusions The¹H and¹³C NMR spectra were studied for 2,3,4-trisubstituted sulfolanes and the isomerism of these compounds was determined, The use of chemical shift information is more convenient to determine the isomerism of polysubstituted cyclic compounds by PMR spectroscopy, while use of the direct carbon-proton coupling constants is more convenient for this problem when employing¹³C NMR spectroscopy.Deceased.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2498–2501, November 1984.     

Etudes des sélénophènes mono et bisubstitués par Résonance Magnétique de 1H et de 13C

Proton and carbon magnetic resonance spectra of mono-and disubstituted selenophenes are investigated. The proton chemical shifts are discussed in terms of magnetic anisotropy and electric field effects of the substituents, with a view to studying the conformational equilibrium of the carbonyl group. π Electronic charges, computed by the PPP method, are correlated with the proton and carbon chemical shifts. The coupling constants between ¹³C and ¹H (1, 2 or 3 bonds) and ¹³C? ⁷⁷Se are shown to be good structural parameters and a set of substituent additivity constants is calculated.     

Carbon Magnetic Resonance Spectra of α, β, γ, δ- and α, β, α′, β′- Unsaturated Ketones

Carbon-13 spectra of a series of 26 unsaturated ketones (ortho- and para-cyclo-hexadienones and corresponding open-chain analogues) have been measured by Fourier-transform. Pulse spectroscopy. A complete analysis has been achieved by means of double resonance experiments using noise-modulated and coherent off-resonance proton irradiation and with the aid of non-decoupled spectra. Chemical shifts are interpreted in terms of charge distribution in the dienone system and of methyl substituent effects. Carbon chemical shifts were also obtained for O-protonated ortho- and para-cyclohexadienones. One-bond and long-range carbon-proton and carbon-fluorine spin coupling constants are reported for several compounds.     

Chemistry of the phenoxathiins and isosterically related heterocycles. IX.N-oxidation on the 13C-nmr chemical shifts and coupling constants of the 1-azaphenoxathiin system

The synthesis of 1-azaphenoxathiin N-oxide is described. Total assignment of the ¹³C-nmr spectrum and the effects of the N-oxide moiety on the chemical shifts and ¹H-¹³C spin couplings constants are described and compared to the parent 1-azaphenoxathiin system. The potential for the use of N-oxidation induced changes in ¹³C-nmr chemical shifts and ¹H-¹³C coupling constants as an assignment criterion is also discussed.     

13C NMR spectra of some 1-, 3- and 4-monosubstituted and disubstituted isoquinolines

Chemical shifts and substituent chemical shift (SCS) effects are reported for 21 monosubstituted iso-quinolines, carrying a halogeno, amino, piperidino or ethoxy group in position 1, 3 or 4. In some cases, assignments of ¹³C resonances were based on the spectra of the corresponding 5-deutero derivatives. For the fluoroisoquinolines some ¹³CF coupling constants are given. The ¹³C NMR spectra of 15 disubstituted isoquinolines were measured; with a few exceptions, mainly the 3,4- and 1,4-disubstituted isoquinolines, the chemical shifts agreed well with those calculated by addition of the SCS effects.     

13C?13C coupling constants and substituent effects on 13C chemical shifts in 13C labelled pyrene and pyrene derivatives

Long range inter-ring ¹³C? ¹³C couplings are found to be effective in the title compounds, and the magnitudes of coupling constants and of substituent effects on ¹³C chemical shifts, as well as the signs of the latter, alternate with respect to the number of connecting bonds.     

Interpretation of the 13C NMR spectrum of physostigmine

The 25.1 MHz ¹³C nmr spectrum of physostigmine in deuteriochloroform has been reanalysed with the aid of high resolution proton coupled spectrum and selective proton irradiation experiments. In addition to unambiguous assignment the analysis yielded values for carbon-proton coupling constants.     

1H- und 13C-NMR.-Spektren von 6-(p-X-Phenyl)fulvenen. Kurzmitteilung

¹H- and ¹³C-NMR.-spectra of 6-(p-X-phenyl)fulvenes The ¹H- and ¹³C-NMR.-spectra of a series of 6-(p-X-phenyl)fulvenes 3 , measured at 9.39 T (93.9 kgauss), have been analyzed. In these compounds, electronic effects due to the substituent X clearly exert changes in chemical shifts as well as in coupling constants in the 5-membered ring. Small changes in bond length are observed by comparison of the vicinal ¹H, ¹H-coupling constants, whereas changes in charge densities linearly influence the chemical shifts of C(5), C(2) and C(3).     

Substituent effects on 13C?13C coupling constants and chemical shifts in 13C labelled polycyclic aromatic hydroxy compounds

The effects of an hydroxy substituent on ¹³C? ¹³C coupling constants and ¹³C chemical shifts have been measured in 1-hydroxynaphthalene-2-¹³C and 1-hydroxypyrene-1-¹³C. The changes observed in the ¹³C? ¹³C couplings show the effect of a substituent attached directly to the labelled carbon or to a carbon ortho to this. In both situations the effect is a decrease in the numerical magnitude of most of the long range ¹³C? ¹³C coupling constants.     

Linear solvation energy relationships VIII—solvent effects on NMR spectral shifts and coupling constants

The solvatochromic comparison method is used to unravel solvent polarity and hydrogen bonding effects on a variety of NMR spectral shifts and coupling constants. Solvent effects are rationalized in terms of the solvatochromic parameters π*, δ, α and β. Properties analyzed include ¹⁹F shifts of 5-fluoroindole, ¹H shifts of fluorodinitromethane, tert-butanol, phenol, 2-methylbut-1-en-3-yne, and thioacetamide, ¹H and ¹³C shifts and J(¹³C¹H) coupling constants of chloroform, ¹³C shifts of acetone, ¹⁵N shifts of pyridine, ¹⁵N and ²⁹Si shifts of 1-methylsilatrane, and some J(¹¹⁹Sn,C,¹⁹F) coupling constants of polyalkyltin compounds.     

Characterization of coupling constants to nitrogen. Carbon-13 chemical shifts and carbon–nitrogen coupling constants of substituted benzaldoximes

Carbon-13 chemical shifts and ¹³C?¹⁵N coupling constants of substituted benzaldoximes and of two non-aromatic oximes have been determined. The coupling constants display little variation as a function of the nature or position of substitution, which suggests that perturbations in the π electron distribution have little effect. The values are compared with the markedly different ones reported for mesitaldoxime, and, in conjunction with the observed solvent effects, are discussed within the Schulman-Venanzi framework for assessing the role of the lone-pair.