Carbon-13 magnetic resonance spectral studies of some bipyridine derivatives

Assignments of¹³C chemical shifts and¹³C-¹H coupling constants are presented for six bipyridine derivatives. Some earlier spectral assignments have been corrected. The spectral parameters of the bipyridines are generally very similar to those of the appropriate simple substituted pyridines. Long range interring coupling constants in these compounds have been discussed.

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¹³C-NMR einiger Bipyridine

Zusammenfassung Es werden die Zuordnungen der¹³C-Verschiebungen und der¹³C-¹H-Kopplungskonstanten für sechs Bipyridinderivate präsentiert. Dabei wurden einige früher getroffene Zuordnungen korrigiert. Das NMR-Verhalten der Bipyridine ist dem der analog substituierten Pyridine generell sehr ähnlich. Die Long-Range-Kopplungen zwischen den Ringen werden diskutiert.

     

Proton magnetic resonance studies of 8-hydroxyquinoline derivatives

The PMR spectra of 8-hydroxyquinoline and eighteen derivatives have been obtained at 220 MHz. For several of the compounds, PMR spectra have not been reported previously. The use of 220-MHz frequency considerably facilitates the interpretation of spectra from such complex derivatives as 2-(2'-pyridyl) and 2-(2'-thienyl)-8-hydroxyquinoline.     

Oxygen-17 nuclear magnetic resonance study of some oxirane derivatives

The ¹⁷O chemical shifts of seventeen variously substituted oxiranes have been measured in CDCI₃ solution. Deviations of δ_o from additivity have been interpreted in terms of steric effects and loss of conjugation. Moreover, in the case of certain cis- and trans-dimethyl-substituted compounds, ¹⁷O NMR allows a differentiation between the different molecular configurations.     

Nuclear magnetic resonance spectra of tropic acid and some derivatives

The NMR spectra of tropic acid, its methyl ester and acetyltropic acid methyl ester were measured at 100 and 220 MHz in various solvents. The spectra were analysed by means of an iterative computer procedure. The results indicate, for all the compounds studied, a predominance of the conformation where the phenyl and hydroxyl (or acetoxyl) groups are in anti.positions to each other. The solvent and concentration effects upon the vicinal coupling constants and hence upon the position of the conformational equilibria are rather weak.     

C-13 magnetic resonance studies of some papaveraceae alkaloids

The natural abundance ¹³C magnetic resonance spectra of some Papaveraceae alkaloids have been determined at 22·628 MHz employing the pulse Fourier transform technique. Several techniques were employed to aid in spectral assignments and it has been possible to make self-consistent assignments for all the resonances for these alkaloids. Evidence is presented for trans-annular interaction between the amino group and the carbonyl group situated across the ten-membered ring.     

Desulfurization of epidithio-2,5-piperazinedione derivatives and their open chain analogs with triphenyl phosphine

Desulfurization of epidithio-2,5-piperazinediones (6 and 7) by triphenylphosphine in THF gave dimeric compounds (8 and 15). In the presence of water or phenol the desulfurization gave 3-hydroxy (9) or 3-phenoxy-2,5-piperazinedione (10). Reaction of 6c with triphenylphosphine in ethyl vinyl ether yielded 2,5-diazabicyclo[2.2.2]octane-3,6-dione (11), indicating the presence of 1,4-dipole (B) as an intermediate of the desulfurization. Similar cycloaddition products (13 and 14) were obtained by the desulfurization of 6c in the presence of benzofuran, indole or skatole. Desulfurization of open chain disulfides (16, 21, 23 and 25) by triphenylphosphine gave reduced products (17, 22 and 26) and an isoxazole (18), but CC bond formation was not observed.     

Chemical and nuclear magnetic resonance studies of 3,3-diphenyltetrahydrofuran derivatives

Pyrolytic cyclization of a- and β-methadol methiodides afforded cis and trans isomers of 2-ethyl-3,3-diphenyl-5-methyltetrahydrofuran, respectively. Catalytic hydrogenation of 2-ethyli-dene-3,3-diphenyl-5-methyltetrahydrofuran yielded the cis and trans isomers in a 2:1 ratio. The nmr spectra of these and structurally related compounds have been analyzed in terms of a half-chair conformation for 2-ethyl-5-methyl, 2-ethyl, and 5-methyl derivatives. An envelope conformation has been suggested for the compounds containing a double bond at C-2.     

Nuclear magnetic resonance studies of 5,6-dicarboxy-2-norbornene derivatives

A detailed study has been made on the ¹H nuclear magnetic resonance (NMR) spectra of 5,6-dicarboxy-2-norbornene derivatives, whose chemical shifts and geminal, vicinal and long-range spin-spin coupling constants were determined. Each signal of the spectra of these derivatives shows a slight low-field shifts compared with norbornene itself. In the case of five methyl esters studied in this work, the signal of the 7s-proton remains at approximately the same position in all the compounds, but that of the 7a-proton is more variable. For the chemical shifts of the 7a-proton of the five methyl esters, an additive rule seems to hold: that the magnitude of the low-field shift, from the 7a-signal of norbornene itself, is obtained by adding each of the effects of the carboxyl and the carbomethoxy groups substituted at the endo-5-(or 6-) or the exo-5-(or 6-) positions of the norbornene ring. In most of the derivatives considered in this work, the spin-spin coupling constants, except those between bridgehead and bridged methylene protons, are about 1 to 2 Hz smaller than those of many other norbornene derivatives already studied. This fact seems to suggest that norbornenes, which have two bulky adjacent substituents at 5- and 6-positions, may suffer distortions in the norbornene ring.     

Oxygen-17 nuclear magnetic resonance study of some five-membered heterocyclic derivatives

¹⁷O NMR spectra have been obtained in the FT mode for some furan and isoxazole derivatives. The chemical shifts, mainly governed by the electronegativities of the atoms bonded to the central oxygen, are also affected by alkylation on the different positions of the ring systems, which gives rise to β and γ effects similar to those observed for simple aliphatic ethers.     

Triphenyl phosphine complex of cyclopentadienyl(manganese dicarbonyl triphenyl phosphine) gold

Conclusions The triphenyl phosphine complex of cyclopentadienyl (manganese dicarbonyl triphenyl phosphine) gold was obtained.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2641–2642, November, 1973.     

13C nuclear magnetic resonance studies on some substituted isoxazoles

¹³C n.m.r. spectra of some substituted isoxazoles have been examined to ascertain the reactive site in the metallation of 4-substituted 3,5-dimethylisoxazoles. The results obtained indicate that metallation occurred exclusively at the C-5 methyl.     

Nuclear magnetic resonance and the conformation of some derivatives of Michler's ketone

¹H NMR spectra are reported for Michler's ketone and twenty of its derivatives, along with ¹³C chemical shifts for five of the compounds. ¹H chemical shifts show only small changes with increasing substitution at the sterically hindered 2-position. Estimates of the dihedral angle between the benzene ring and C? CO? C planes have been obtained from the chemical shifts of C?O and 4-C for ketones 1, 3, 5, 15 and 16 . These angles are both internally consistent and very similar to dihedral angles determined by other methods for corresponding compounds in the benzophenone series.     

Proton and boron-11 magnetic resonance studies of some potassium tetraarylborates

Proton and boron-11 magnetic resonance spectra for several potassium para-substituted tetraarylborate compounds [KB(C₆H₄-pX)₄, where X is H, OCH₃, CH₃, Br, Cl, F, CF₃] have been obtained. The chemical shift between the centers of the AA′ and XX′ multiplets for the ring proton multiplets, relative to a reference chemical shift of 0·39 ppm for potassium tetraphenylborate, correlated with the corresponding Hammett σ values for the para-substituent. Additionally, the boron-11 chemical shifts gave a good correlation with corresponding σ values for the substituents. Electronegativities of para-substituted phenyl rings were calculated and found to be approximately 2·70 for all compounds studied. It was shown that electronic substituent effects do not greatly influence the electron density surrounding the central boron atom in the tetraarylborate ions.     

17O nuclear magnetic resonance studies of some enriched amino acids

The ¹⁷O NMR chemical shifts of five enriched amino acids have been measured under strictly controlled conditions of concentration, ionic strength, pH and temperature. The α, β and α, γ carboxyl resonances of aspartic and glutamic acid, respectively, have been resolved. Line widths were examined as a function of solution viscosity.     

Carbon-13 nuclear magnetic resonance spectroscopy—VII:para-substituted fluorobenzenes

C-13 and F-19 NMR spectra of seventeen para-substituted fluorobenzenes were measured and the chemical shifts as well as coupling constants with respect to substituents were analysed. The chemical shifts of the fluorine, the C₁ and the C₂ atoms were found to depend on the total electron densities. In the case of the C₃ atom, the chemical shifts seem to depend on π-electron densities rather than the total electron densities. The present calculations also indicate that the chemical shift of the C₄ atom depends mainly on σ-electron densities due to the inductive effects of substituents. The strongest factor influencing the coupling constant, ⁿJ(C? F), is also considered to be the π-electron densities on the carbon atoms. In the case of the direct couplings, ¹J(C? F), the π-bond orders are important.     

Naphthopyrones,Part I Proton magnetic resonance spectral studies of some methylnaphthopyran-2-one and methylnaphthopyran-4-one derivatives

The 220 MHz¹H-NMR spectra of four methylnaphthopyrone derivatives are presented and discussed. The chemical shift changes which occur upon protonation in trifluoroacetic acid solution are much more significant for the benzochromones than for the benzocoumarins. The particularly large effects at the methyl (0.6 ppm) and at the residual pyrone ring proton (1.2 ppm) provide a useful technique for differentiation between the two series of compounds.

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Naphthopyrone, 1. Mitt.:¹H-N M R einiger Methylnaphthopyran-2-one und Methylnaphthopyran-4-one

Zusammenfassung Es werden die 220 MHz¹H-NMR-Spektren von vier Methylnaphthopyronen diskutiert. Die Änderungen der chemischen Verschiebungen, die sich mit Trifluoressigsäure als Lösungsmittel ergeben, sind für die Benzochromone bedeutend signifikanter als für Benzocumarine. Die besonders großen Effekte für Methyl (0,6 ppm) und das verbleibende Pyronringproton (1,2 ppm) stellen eine brauchbare Methode für die Unterscheidung der beiden Reihen dar.

     

Proton magnetic resonance spectra of some vinyl and ethyl derivatives of five-membered N-heterocycles

Conclusion On the basis of the chemical shifts of the signals in the PMR spectra of the N-vinyl and N-ethyl derivatives of indole, benzimidazole, benzotriazole, and imidazole a theory was advanced regarding the character of the influence of a second and third nitrogen atom on the vinyl and ethyl radicals.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 475–476, February, 1972.We express our gratitude to Yu. L. Frolov for his helpful evaluation of the experimental data.     

13C Nuclear magnetic resonance studies of some substituted thiols and thioanisoles

¹³C NMR spectra of thiophenol, 4-nitrothiophenol, 4-X-thioanisole (X = NO₂, NH₂, SH, H) were examined in CDCl₃ solution. Substituent chemical shift values (additivity parameters) for the −SH and −SCH₃ groups are reported.In para-substituted thioanisoles, while the −NH₂ group caused a deshielding and −NO₂ a shielding of SCH₃ carbon resonance, −SH appeared to have had no effect on the carbon resonance.     

Naphthopyrones,part II Carbon-13 magnetic resonance spectral studies of some methylnaphthopyran-2-one and methylnaphthopyran-4-one derivatives

Assignments of¹³C chemical shifts and¹³C-¹H coupling constants are presented for four methylnaphthopyrone derivatives. Differentiation between the benzocoumarin and benzochromone series is best performed by consideration of the carbonyl chemical shift and coupling pattern.

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Naphthopyrone, 2. Mitt.:¹³ C-NMR einiger Methylnaphthopyran-2-one und Methylnaphthopyran-4-one

Zusammenfassung Es werden die Zuordnungen der chemischen Verschiebungen der¹³C-Resonanzen und der¹³C-¹H-Kopplungen für vier Methylnaphthopyrone diskutiert. Die Unterscheidung zwischen der Benzocumarin- und der Benzochromon-Reihe erfolgt am besten mittels chemischer Verschiebungen und dem Kopplungsmuster.