13C NMR spectra of benzodiazepinones: Application to isomeric structure determination

A ¹³C NMR study of a number of substituted 1,5-benzodiazepin-2-ones has been carried out, and shows that this technique is one of the rare spectroscopic methods which allows an unambiguous identification of the number and nature of the isomers formed in the condensation of a β-ketoester with a substituted O-phenylenediamine.     

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.     

1H and13C NMR spectra of 1,5-disubstituted 1,3,4-oxadiazoles

The¹H and¹³C NMR spectra of 2, 5-disubstituted 1,3,4-oxadiazoles with aliphatic, aromatic, and hetero-aromatic substituents have been described and interpreted. The electronic effect of the 1,3,4-oxadiazole group as a benzene ring substituent was evaluated using¹³C NMR spectroscopy.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 834–842, June, 1994. Original article submitted April 8, 1994.     

13C NMR spectra of s-triazolo-as-triazinones: Application to isomeric and tautomeric structure determination

¹³C NMR spectroscopic data are reported for the s-triazolo-as-triazinones of five isomeric series. Comparison of their ¹³C chemical shifts and CH coupling constants allows the determination of the type of ring junction of the two heterocycles, as well as the predominant tautomeric form in each system.     

13C NMR spectra of S-methylquinolines

The ¹³C chemical shifts and the increments () of the SCH₃ group in the NMR spectra of S-methylquinolines were measured. It is shown that the chemical shifts of S-methylquinolines correlate satisfactorily with the total charges on the carbon atoms calculated within the CNDO/2 approximation. The coupling of the SCH₃ group with the quinoline ring was examined on the basis of the values.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1665–1671, December, 1979.The authors thank É. É. Liepin' for his discussion of the results.Original article submitted October 1, 1978.     

13C NMR spectra of alkenylsilanes

Conclusions The¹³C NMR spectra of 12 alkenylsilanes were measured and the values of the increments of the chemical shifts of the (CH₃)₃Si group were determined for some allylsilanes.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 938–939, April, 1978.     

13C NMR spectra of adamantane derivatives

The carbon-13 chemical shifts of mono- and 1,3-disubstituted adamantanes are reported. The effects caused by the substituents are compared with those met in aliphatic and alicyclic compounds. It is shown that the 1,4-interactions have only minor importance in l-substituted adamantanes. The influence of polar groups on the chemical shifts of γ- and δ-carbon atoms is a typical ‘through-the-bonds’ interaction and correlates with inductive parameters of the substituents.     

The 13C NMR spectra of homoisoflavonoids

The study of a set of 3-benzylidene-4-chromanones, 3-benzyl-4-chromanones, 3-benzyl-3-hydroxy-4-chromanones and 3-benzylchromones (homoisoflavonoids) by ¹³C NMR spectroscopy shows the influence of the structure of these molecules on the chemical shifts of the more characteristic carbon atoms at positions 2, 3 and 4.     

13C NMR spectra of protonated S-methylquinolines

The signals in the¹³C NMR spectra of protonated 2-, 3-, 4-, 5-, 6-, and 8-S-methylquinolines in solution in 6 N DCl were assigned. The changes in the¹³C chemical shifts relative to the neutral molecules were compared with the results of calculations within the CNDO/2 approximation. It is shown that when the molecules are protonated, the shift of the¹³C signals is due to changes in the charges and the paramagnetic components of shielding of the nuclei.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 663–665, May, 1980.     

13C NMR spectra of substituted thiacyclohexanes

Conclusions The use of the¹J_CH values permits making an unequivocal assignment of the¹³C signals in the spectra of substituted thiacyclohexanes. The steric arrangement of the substituants in 2,4-disubstituted thianes can be established on the basis of the chemical shift values of the C⁶ nuclei. The obtained data can be used to identify the cyclic organosulfur compounds that are isolated from crude petroleum.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 452–454, February, 1982.     

13C NMR spectra of polycyclic diaziridines

A significant difference between experimental¹³C NMR chemical shifts and those predicted from the¹³C NMR/IR databank was found for bi- and tricyclic diaziridines. Quantum chemical (AMI) and molecular-mechanical (MMX) calculations showed that the relative chemical shift of the nodal C atom is dependent mainly on deformations of the C-C-C valence angle at this atom.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2496–2499, November, 1991.     

13C NMR spectra of arylnaphthalene lignans

The¹³C NMR spectra have been investigated of a number of arylnaphthalene lignans of plant origin: daurinol and its acetyl derivative and reduction product, justicidin A, justicidin B and its reduction product and the diacetyl derivative of the reduction product, and diphyllin and its acetate. The values of the chemical shifts of the carbon atoms in the spectra of the compounds investigated and the nature of their change according to structural factors are discussed and an assignment is made of the resonance lines in the spectra. The characteristics of the spectrum of one compound are used as models for others. The parameters of the¹³C NMR spectra of a number of naphthalene derivatives are also used. On the basis of the results of the assignment of the signals, difference values of the chemical shifts of the carbon atoms in the series of compounds investigated have been determined. Using the experimental results as a background, some examples taken from the literature of investigations of the¹³C NMR spectra of related compounds have been analyzed.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 76–90, January–February, 1987.     

Interpreting doped polyacetylene13C NMR spectra

Karpov Physicochemical Research Institute. Translated from Zhurnal Strukturnoi Khimii, Vol. 30, No. 3, pp. 142–144, May–June, 1989.     

13C NMR spectra of acetylated hederagenin glycosides

The¹³C NMR spectra of acetylated derivatives of the following hederagenin glycosides have been studied hederagenin 3-0--L-arabinopyranoside, hederagenin 3-0-[0--L-rhamnopyanosyl-(12)--L-arabinopyranoside], hederagenin 3-0-[0--D-glucopyranosyl-(12)--L-arabinopyranoside], hederagenin 28-0--D-glucopyranoside, and hederagenin 28-0-[0--L-rhamnopyranosyl-(14)-0--D-glucopyranosyl-(16)--D-glucopyranoside]. The spectra give information about the monosaccharide composition, the position of attachment of the carbohydrate chain, and the configurations of the glycosidic bonds, and, in some cases, the orders of the bonds.Pacific Ocean Institute of Bioorganic Chemistry of the Far Eastern Scientific Center, Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 359–362, May–June, 1980.     

13C NMR spectra of gem-dichlorocyclopropyl aryl selenides

Conclusions The¹³C NMR spectra of a number of cyclopropyl aryl selenides were discussed for the first time and it was shown that p- interaction is absent between the three-membered ring and the ArE fragment, where E=0, S, Se.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2410–2412, October, 1978.     

13C NMR spectra of biologically active compounds

The diastereomeric effects on the¹³C NMR chemical shifts of thirteen epimeric pairs of 16-aryloxy-11-deoxyprostaglandins of the E₁ and F₁ series caused by the change in the configuration of the 15-hydroxy group, which are differential parameters for assigning epimers to the 15- and 15-stereochemical series, have been determined.For Communication (VIII), see [1].Institute of Chemistry, Bashkir Scientific Center, Urals Branch, Academy of Sciences of the USSR, Ufa. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 123–128, January–February, 1991.