Etude par Résonance Magnétique Nucléaire de dérivés phosphores. Etude de dithiaphospholanes-1,3,2

The proton NMR spectral analysis of eight different 1,3,2-dithiaphospholanes with various groups attached to the phosphorus atom has been performed. The AA′BB′X (X phosphorus atom) system shows that the two ³J(P? S? C? H) coupling constants have a small magnitude and opposite signs. Using the ³J(HH) values, the torsion about the C₄—C₅ bond has been evaluated. The conformational requirements in the two isomers of the 2 phenyl-4-methyl-1,3,2-dithiaphospholane are also discussed.     

Etude par Résonance Magnétique Nucléaire du carbone 13 de complexes du cobalt (III) et de la diméthylglyoxime

From a carbon magnetic resonance study of several alkylcobaloximes RCo(DMG)₂B (DMG = dimethylglyoximate monoanion), it was possible to estimate the α, β and γ effects of the Co(DMG)₂B group on the chemical shifts of the carbon atoms of various alkyl groups R. The chemical shifts of the carbon atoms belonging to the equatorial ligands and to the axial base B are not significantly affected by structural modification of the R groups. Values of δ in benzylcobaloximes XC₆H₄CH₂Co(DMG)₂B agree with a donor effect of the ? CH₂Co(DMG)₂B radical. Values of ¹J(¹³C? H) coupling constants, measured in ¹³C enriched methylcobaloximes, do not vary appreciably when B is changed (J(¹³C? H) = 137 ± 1 Hz) and are close to the value obtained for methylcobalamine.     

Effets de Substituants en Série Diazolique et Diazinique-1,3—Etude par Résonance Magnétique Nucléaire du Carbone-13

We have recorded the ¹³C n.m.r. spectra of thiones and thioethers in the 1,3-diazole and 1,3-diazine series with various alkyl substituents at the nitrogen atoms. Some analogous oxygen containing heterocycles were also examined. We have shown that in the thiocarbonylated compounds the thiol ? thione equilibrium is displaced towards the thione form, but that ¹³C n.m.r. gives only qualitative results. In the sulphur containing derivatives the isopropyl group is in a fixed conformational position because of the steric hindrance of the sulphur atom. Substitution by a tert-butyl group leads to unexpected γ values. We ascribe this phenomenon to ring deformation or to variations in the valence angles of the substituted nitrogen atoms.     

Héterocycles contenant du phosphore—XVII: Etude par Résonance Magnétique Nucléaire et analyse conformationnelle de quelques oxazaphosphorinanes-1,3,2

The PMR spectra of some new 1,3,2-oxazaphosphorinanes are analysed. In one case, after elimination of the P? H spin coupling, the spectra give rise to a particular ABKLXY pattern in which certain coupling constants between vicinal protons are zero. The ABKLXY system where J_AK = J_AL = J_BK = J_BL is studied and most of the parameters of the related compound are calculated. The ring conformation is discussed and the free energy is given; for one oxazaphosphorinane, the calculation of the torsional angle of the C₄? C₅ and C₅? C₆ fragments is described.     

Etude par Résonance Magnétique Nucléaire du 13C des chlorhydrates de-N-(phényl-1 cyclohexyl) piperidines.

The conformations of N-(1-phenylcyclohexyl)piperidinium chloride and some 4-substituted derivatives in H₂O and CDCl₃ were studied by means of ¹³C NMR. The results confirm the greater stability of compounds with equatorial piperidinium. Certain characteristics in the observed chemical shifts may be attributed to deformations of the cyclohexyl system, probably caused by the phenomenon of solvation.     

Etude en Résonance Magnétique Nucléaire du Carbone-13 de N-Aryl Pyrazolines-2 Diversement Substituées. Effets de Substituant et Etude Conformationnelle

The ¹³C chemical shifts of 1-phenyl-2-pyrazoline and 25 N-nitrophenyl-2-pyrazolines, with different substituents on the heterocyclic ring, have been assigned. These values are discussed as a function of the steric and electronic nature of the various substituents. The steric effects produced conformational modifications, both in the nitrophenyl and 2-pyrazoline moieties, which explain some of the chemical shifts.     

Hétérocycles contenant du phosphore: XXVII—Etude par Résonance Magnétique Nucléaire de quelques dérivés des dioxa-et dithiaphospholanes-1,3,2 monosubstitués en 4

The ¹H n.m.r. spectra of some derivatives of 4-methyl (or 4-phenyl) 1,3,2-dioxa- and 1,3,2-dithiaphospholanes are analysed. The configurational study of the compounds has been investigated. The torsional angle of the C₄? C₅ fragment is calculated and the ring conformation in solution is discussed.     

Hétérocycles contenant du phosphore: XXVIII—Etude par Résonance Magnétique Nucléaire et analyse conformationnelle de quelques oxazaphosphorinanes-1,3,2 (II)

The ¹H n.m.r. spectra of some new 1,3,2-oxazaphosphorinanes are analysed. The stereochemistry and the ring conformation is discussed. The free energy and the torsional angle of the C-4? C-5 and C-5? C-6 fragments are calculated for some of these 1,3,2-oxazaphosphorinanes.     

Etude par Résonance Magnétique Nucléaire de la thiamine (vitamine B1). Site de protonation-équilibre de tautomérie

Calculations are presented as evidence for the existence of a tautomeric equilibrium in thiamine and its polyphosphoric esters. The relative position of the equilibrium in these compounds is considered. Most of the experimental observations can be explained by the results of the calculations.     

Résonance magnétique nucléaire du noyau 14N par Transformée de Fourier

¹⁴N-NMR. measurements using the Fourier Transform technique are presented and compared to C. W. experiments. The F. T. technique is especially advantageous for relaxation time measurements. However, since ¹⁴N-nuclei may have widely different relaxation times, it is often not possible to have optimal gain in sensitivity (as compared to C. W. measurements) in a single F. T. experiment for different ¹⁴N-nuclei contained in the same sample. Different experiments have to be performed, optimizing the spectrometer parameters for each ¹⁴N-resonance of appreciably different linewidth. The technique is applied to three different problems. ¹⁴N-relaxation in symmetrical ammonium salts is shown to arise from reorientation of the water dipoles. The use of a double spin-probe, ¹³C-¹⁴N, allows the determination of the electric field gradients in cyclic ammonium salts. The electronic distribution is especially distorted from tetrahedral symmetry in the highly strained N, N-dimethyl-aziridinium cation. Finally, electric and dynamic effects in ion pairing may be studied as shown on the case of tetrabutylammonium iodide in water and in benzene.     

Etude Conformationnelle par Résonance Magnétique Nucléaire Protonique des Dérivés de la O-Isopropylidène-2′,3′ Adénosine

Conformational analysis using ¹H n.m.r. data (δ, ³J and NOE) has been carried out on several derivatives of 2′,3′,-O-isopropylideneadenosine bearing various substituents at positions C-5′, C-8 and N-6. Conformational modifications are assigned to specific interactions between the sugar and purine moieties and also to solvent effects.     

Identification et Etude en Résonance Magnétique Nucléaire du Carbone-13 des Produits de la Réaction de Quaternisation en Série Thiazolo[3,2-d]tétrazolique

We have demonstrated that the compounds obtained by quaternization of thiazolo[3,2-d]tetrazole, and two of its derivatives, 3-phenyl-thiazolo[3,2-d]tetrazole and tetrazolo[5,1-b]benzothiazole, are tetrazolium salts. The quaternization effects are discussed as a function of the ¹³C NMR results.     

Résonance Magnétique Nucléaire. V.—Etude de Chlorures Vinyliques par RMN 1H. Incréments spécifiques des radicaux alkyle

Twenty five geometrical isomers of vinylic chlorides have been isolated and studied by ¹H n.m.r. and g.l.c; some of these have been chemically reduced for identification. New values of alkyl substituent increments for the estimation of olefinic proton chemical shifts are listed. The effect of chlorine (down field shift) on vinylic allylic and homoallylic protons is described, as well as the solvent effect of benzene (high field shift).     

Dynamique Moléculaire des Chloro-4 et Bromo-4 Méthylènecyclohexanes par Résonance Magnétique Nucléaire du 13C

Kinetic parameters are obtained for ring inversion of 4-chloro- and 4-bromo-1-methylenecyclohexanes by observation of ¹³C and ¹H NMR spectra as a function of sample temperature. Cl and Br substituents show similar effects on the inversion barrier in the exo-methylene system and in the parent cyclohexane.     

Etudes Conformationnelles par Résonance Magnétique Nucléaire d'Ethanes Disubstitués par un Hétéroatome appartenant aux Colonnes IV,V et VI et par un Groupement Fonctionnel

In this paper results obtained in the conformational analysis of ethers, sulphides, selenoethers, amines, arsine, germanes and stannanes such as R? X? CH₂? CH₂? Y are given. The AA′BB′ part (–CH₂? CH₂–) of the NMR spectra was studied by a method using chemical shifts. The electronegativity of the heteroatom was connected with the difference of the chemical shifts of AA′BB′. Following this, conformational analysis based on NMR spectra obtained at different temperatures permitted us to show that in the temperature range used (230 K–320 K) triphenylstannyl-3 propionitrile has a ‘blocked structure’.     

Détermination par Résonance Magnétique Nucléaire de la Configuration d'alcools Bicycliques [4.2.0] et Tricycliques [6.4.0.02,7] ou [5.4.0.02,6]

The configuration of various bicyclo[4.2.0]octanols has been established by ¹H NMR spectroscopy, with Eu(dpm)₃ as shift reagent. The intrinsic parameters Δ and K have been obtained and used as structural probes. Moreover, detailed data analysis showed that, contrary to the generally accepted concept, the vicinal coupling constant between trans cyclobutanic protons can be larger than that between cis protons. The chemical shifts obtained by ¹³C NMR spectroscopy are consistent with the proposed structures. The results have been extensively used to determine unambiguously the configuration of tricyclo[6.4.0.0^2,7]dodecanols and tricyclo[5.4.0.0^2,6]undecanol.     

Résonance Magnétique Nucléaire de 17O. Aldéhydes et cétones aliphatiques: additivité des effets de substitution et corrélation avec la 13C-RMN

¹⁷O-NMR. Aliphatic aldehydes and ketones, additivity of substituent effects and correlation with ¹³C-NMR. The ¹⁷O-chemical shifts of 9 aldehydes, 22 aliphatic and 4 alicyclic ketones, in the natural abundance FT.-NMR. spectra followed a good correlation with the ¹³C-chemical shifts of the terminal C-atoms of corresponding methylene compounds. An additivity relation involving 6 parameters represents the ¹⁷O-shifts of 28 of the measured products with a standard deviation of 2.5 ppm. The additivity parameters are discussed with respect to the modifications of the polarity of the carbonyl group induced by the hyperconjugative interaction of π and π* orbitals with the πCH ₃ orbitals of the alkyl substituent groups.     

Effet de Solvant en Résonance Magnétique Nucléaire du Carbone-13. V. Autoassociation des Cétones Aliphatiques et Alicycliques Saturées

The effect of self-association on the carbonyl carbon NMR screening constant is determined for 15 ketones. It is shown that the corresponding screening constant term can only be related to the dipole moment and the molecular volume both for aliphatic and alicyclic ketones. The average distance between the two carbonyls is determined for a bimolecular association model where the two dipoles are antiparallel. This distance increases with increasing alkyl substituent size from 3.1 Å for acetone to 4.75 Å for the bulky ketone (Et)₃CCOC(Me₂,tBu) where self-association is still significant. Cyclanones show a greater effect than aliphatic ketones with the same number of carbons.     

Recherches sur la stéréochimie des diènes fonctionnels—X: Etude par Résonance Magnétique Nucléaire d'alcoxybutadiènes 1,3

The nuclear magnetic resonance parameters of 1,3 alkoxy-butadienes are strongly dependent on the cis or trans configuration of the ethylenic systems. A discussion of the different types of coupling constants and of the additivity of substituent effects on the chemical shift is proposed. The results are applied to the identification of isomers and to the study of the electronic and stereochemical structure of each configuration. The conformational equilibrium about the C? C and C? O bonds is discussed with special reference to the aromatic solvent and temperature effects.     

Etudes conformationnelles par Résonance Magnetique Nucléaire et variations de températures d'éthanes di- et trisubstitués

In this paper we report the conformational analysis of several di- or trisubstituted ethanes substituted by the following groups: N-dialkly, thioalkyl, alkoxy, N-pyrrolidino, N-benzyl, nitrile or carbomethoxy. Spectra were calculated by a method based on chemical shifts. Relative stabilities of rotamers were discussed in relation to structural parameters (geometrical and electronic).