Carbon-13 nuclear magnetic resonance studies of coumarin and related compounds

Fourier-transform ¹³C NMR spectra of nine coumarinoid compounds of medicinal interest are reported. All of the carbon resonances are assigned with the aid of various spectral techniques and stable isotopic labeling. The substituent effects on the chemical shifts in several systems are also discussed.     

Carbon-13 nuclear magnetic resonance spectra of nicotine metabolites and related compounds

The potential of ¹³C NMR techniques for studies of nicotine metabolism has been investigated by acquisition and assignment of ¹³C NMR spectra of nicotine, its metabolites and some related compounds. It is shown that C-2′ of nicotine would be the best site for ¹³C labelling when using the method to gain further insight into the metabolic pathways of nicotine.     

Carbon-13 nuclear magnetic resonance spectra of some heterocyclic D-homoandrostanes

The ¹³C chemical shift data of several D-homoandrostanes with heteroatoms (N,O) in the 17a-position are reported. Heteroatom effects on the shieldings of the carbons of rings C and D are discussed.     

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.     

The proton magnetic resonance of heterocyclic diketones

A full analysis of the 60 MHz ¹H NMR spectra of heterocyclic analogues of 1,3-indandione [N-(2-bromoethyl)-phthalimide, phthalic anhydride and thiophthalic anhydride] and of 1,2-indandione (N-methylisatin, coumarandione and 2,3-dihydrothionapthene-2,3-dione) has been carried out. The protons of the symmetric compounds resonate at lower fields than those of the asymmetric ones and the proton ortho to the CO function is more deshielded than the proton ortho to the heteroatom. Coupled Hartree-Fock perturbation theory has been applied to estimate the ring current contributions to the proton chemical shifts and to the magnetic susceptibilities. MO calculations based on the finite perturbation theory at the CNINDO levels provide information on the relative importance of σ and π pathways for the various coupling constants.     

Deuterium nuclear magnetic resonance spectroscopy. II—distribution of deuterium in some labelled nitrogen heterocyclic compounds

Pyridine, methylpyridines, quinoline and isoquinoline have been labelled with deuterium using pre-reduced platinum dioxide (PtO₂·2H₂O) and heavy water. Their ²H chemical shifts from monodeuteriated TMS have been assigned. The extent of the labelling has been determined directly by ²H NMR spectroscopy.     

Introduction to nuclear magnetic resonance

The basic principles of nuclear magnetic resonance (NMR) are presented in an elementary form using classical and elementary quantum mechanics and the experimental technique 1s explained. The motion of the magnetization by r.f. pulses, free induction decay and spectrum, transverse and longitudinal relaxation, local field and spin echo are described and the effects of molecular motion are discussed. The concepts of spin temperature and spin diffusion are presented and the advantage of using quadrupole nuclei is stressed. Finally, the specific problems of NMR in interface studies are considered and a typical example is given.     

Oxygen-17 nuclear magnetic resonance spectral investigation of 3-alkoxy-trans-3,4-disubstituted-thiolane 1,1-dioxides and related compounds

The ¹⁷O NMR spectra of 3-alkoxythiolane 1,1-dioxides indicate that the sulfonyl oxygens are diastereotopic but their chemical shift differences are essentially independent of the structure of the alkyl group in the alkoxy moiety. Eu(fod)₃ enhances the ¹⁷O chemical shift differences between the diastereotopic sulfonyl oxygens in 3-isopropoxythiolane 1,1-dioxide and shifts both oxygens upfield. α,β-Unsaturation deshields the sulfonyl oxygens in both five- and six-membered rings.     

Substituent effects in heterocyclic systems by carbon-13 nuclear magnetic resonance. Isoxazoles

The carbon-13 nmr spectra of a series of 3-aryl-5-phenylisoxazoles (I) and 3-phenyl-5-arylisoxazoles (II) have been recorded and the signals assigned. Carbon-13 data for series I show little effect of substituent on the chemical shift of the isoxazole ring carbons. However, a plot of the carbon-13 chemical shift of carbon-5 in the isoxazole system I versus the chemical shift of carbon-3 in the 3-(4′-aryl)-1-phenylpropenones gives a straight line (r = .989) with a slope of 0.35. In series II, the chemical shifts of both carbon-4 and -5 are relatively sensitive to substituent effects. Fair correlations between Hammett sigma values and the chemical shifts of these two carbons are found; dual substituent parameter treatment improves the correlations. The results obtained from correlations with carbon-4 in series II are similar to those obtained from β-carbons of a number of styrene systems. The data show that carbon-4 in series II is approximately 20% less sensitive to substituent effects than the previously reported data for carbon-3 of 2-arylfurans. Transmission of substituent effects in the isoxazole system compare well with those of the benzothiazole system.     

Cobalt-59 nuclear magnetic resonance spectra of compounds with cobalt-tin bonds

The cobalt-59 NMR spectra of a series of substituted tetracarbonyl cobalt compounds are recorded in solution. Several considerations have shown that in the series R_nX_m-nSn{Co(CO)₄}_4-m (m = 1,2,3; n ? m; R = alkyl, phenyl; X = Cl) the chemical shift is mainly sensitive to π-effects in the metal-metal bond.     

Chemistry of heterocyclic N-oxides and related compounds

The possibility of homogeneous dehydrogenation of anabasine with N-imines of pyridine, 2-picoline, and quinoline and of the Hantzsch ester with N-tosylimidopyridine and N-tosylimidoquinoline is shown.See [1] for communication II.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 816–818, June, 1973.     

Chemistry of heterocyclic N-oxides and related compounds

The dehydrogenation of anabasine, piperidine, and isoanabasine N-imine hydrochlorides by pyridine N-imine hydrochloride and the dehydrogenation of anabasine pyridinia-p-toluenesulfonamidate were studied. The corresponding pyridines and products of reductive deimination were obtained.See [1] for communication VII.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1535–1537, November, 1977.     

Chemistry of heterocyclic N-oxides and related compounds

The dehydrogenating activity of 4-nitropyridine N-oxide and picolinic, nicotinic, isonicotinic, and quinolinic acid N-oxides was studied in the case of the reaction with the Hantzsch ester.See [1] for communication VIII.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1651–1653, December, 1977.     

Chemistry of heterocyclic N-oxides and related compounds

The corresponding deoxy bases were obtained by hydrogenation of pyridine and quinoline N-oxides by hydrogen transfer from cyclohexene, 1,4-dihydronaphthalene, tetralin, and formic acid on a palladium catalyst.See [1] for communication VI.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 920–921, July, 1976.     

Chemistry of heterocyclic N-oxides and related compounds

Isonicoteine N-oxide and N-oxide were synthesized. A preparative method for the synthesis of anabasine Py-N-oxide is proposed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 378–380, March, 1973.The authors thank V. B. Leont'ev for his discussion of the UV, IR, and PMR spectra.