Etude par RMN du proton d'hétérocycles voisins de l'oxazaphospholane-1,3,2. I—La phényl-3 oxo-2 oxathiazolidine-1,3,2

A complete analysis of the ¹H NMR spectrum of the title compound is used for the conformational assignment of the molecule in the C-4—C-5 region. The position of protons is related to the position of the S?O bond with the help of a europium complex Eu(fod)₃. The results obtained are consistent with those found for similar compounds with or without a phosphorus atom.     

Etude comparative des méthyl-borazines par RMN

A comparative study of borazine ( 0 ) and six methyl borazines ( 1 to 6 ) has been conducted by NMR. It becomes evident that the chemical shift of N? CH₃ protons hardly varies between mono-, di- and tri-N-methyl borazines, whereas this parameter undergoes a strong change (in all 0·21 ppm, to high field) when one passes from N-trimethyl borazine (HB? NCH₃)₃ to hexamethyl borazine (CH₃B? NCH₃)₃ through a gradual substitution on the three boron atoms ( 3, 4, 5 and 6 ). Moreover, a systematic variation of the parameter δ has been found between compounds 3, 4 and 5 for the protons which keep precisely the same immediate environment. A qualitative interpretation of this experimental result is proposed in terms of electronic effects general to the hexagonal planar boron/nitrogen ring which characterises these molecules.     

Hétérocycles contenant du phosphore. XXIV—Etude par RMN du proton de l'oxo-2 phénoxy-2 diphényl-6,6 oxazaphosphorinane-1,3,2 et de l'oxo-2 phénoxy-2 méthyl-4 oxadiazaphosphorinane-1,3,4,2

Two phosphorus heterocycles are studied by means of ¹H NMR and IR spectroscopy. The ring conformation is discussed and the torsional angle of the C-5—C-6 fragment is calculated for one of them.     

Etude par RMN 1H d'hétérocycles voisins de l'oxazaphospholane-1,3,2: III—Le phényl-1 dioxa-2,8 aza-5 phosphav-1 bicyclo[3.3.0]octane et le dioxa-1,6 diaza-4,9 phosphav-5 spir[4.4]nonane

The interpretation in terms of conformational analysis of ¹H n.m.r. parameters of 1-phenyl-2,8-dioxa-5-aza-1-phospha^v bicyclo[3.3.0]octane is consistent with a rigid envelope conformation for each 5-membered ring and a planar nitrogen atom. In the case of 1,6-dioxa-4,9-diaza-5-phospha^vspiro[4.4]nonane, the same procedure shows librational motions around the C? C bond.     

Etude conformationnelle de la dimethyl-3,4 cyclopentanone trans: II—Spectres de RMN

The NMR spectra of trans-3,4-dimethylcyclopentanone and trans-3,4-dimethyl-2,2,5,5-tetradeuteriocyclopentanone are analysed. The coupling constants, calculated for the deuterated compound, are in good agreement with a diequatorial conformation of the methyl groups.     

Hétérocycles contenant du phosphore. XXII—Etude par RMP de dérivés de l'oxazaphospholane-1,3,2: II—Analyse des spectres de composés monosubstitués en 5 ou disubstitués en 4 et 5.

The influence of various factors (temperature, nature and concentration of solvent) or the utilisation of various physical methods (tickling or INDOR experiments, for example) are employed to analyse the PMR spectra of some 5-monosubstituted or 4,5-disubstituted 1,3,2-oxazaphospholane derivatives.     

Etude par RMN d'une inversion de cycle de quelques benzodiazépinones

The NMR spectra of five benzodiazepinones are determined over a range of temperature. They indicate that the seven ring has a twist-boat shape, which inverts more or less rapidly according to the nature of substituents. The activation parameters and the rates of inversion are determined and the substituent effects are discussed.     

Hétérocycles contenant du phosphore. XXIII—Etude par RMP de dérivés de l'oxazaphospholane-1,3,2: III—Interprétation des résultats. Tentative d'analyse conformationnelle

By employing certain hypotheses, it is possible to determine the C₄? C₅ conformation of the various 1,3,2-oxazaphospholane derivatives for which PMR parameters have been calculated previously.     

Action d'organolithiens sur la méthyl-2 quinoxaline. Etude de la réactivité des adduits

The action of organolithium reagents such as phenyllithium or n-bulyllithium on 2-methylquinoxaline gave lithiation of the methyl group which upon reaction with electtropholesphiles produce side chain alkenyl derivatives. On the other hand organolithium reagents react with the quinoxaline azomethine bond to give I-lithio-2-alkyl)or ary-1)-3 methylquinoxalines which can be further loithiated on the methyl group to give 2-alkyl(or aryl)-3-alkenylquinoxaline derivatives. The adducts can be condensed with clectrophiles such as benzonitrile or methlyl benzoate but only methyl benzoate leads to N condensed derivatives. Furthermore substituted 1,2,3,4-terahydroqinoxalines are available via the above lithio intermediates.     

Complexation du trichlorure d'aluminium par la triméthylphosphine et la diméthylphénylphosphine: Etude RMN

NMR spectra of several R₃P/AlCl₃ systems [with R₃ = (CH₃)₃ and (CH₃)₂(C₆H₅)] in solution have been measured. The results suggest the occurrence of fast exchanges involving 1/1 and 2/1 adducts and free phosphine. The existence of the 2/1 compounds has been confirmed by low temperature (173 K) experiments.     

Etude par RMN des 2,2′-Dihalogeno-Diethylethers—I: Effet de Température

NMR spectra of disubstituted ethers with the formula (X? CH₂? CH₂)₂O, X = Cl, Br, I, have been studied. Spectra of neat liquids at ambient temperature and spectra of these compounds in CS₂ at different temperatures have been analysed. It has been possible to assign the chemical shifts. In each case, the more populated rotamers have been determined. Additionally, for these three compounds dissolved in CS₂, it is shown that the gauche form becomes more stable with cooling. The authors propose a procedure, using spectral decomposition, which allows the analysis of AA′BB′spectra almost degenerated in A₂B₂ cases.     

Etude structurale de la bipyrimidine par RMN en phase nématique

The 240 MHz NMR spectra of bipyrimidine in the nematic phase of p-methoxybenzylidene-p-n-butylaniline is analysed. The para H,H inter-ring distance is determined. The barrier to internal rotation of the inter-ring C? C bond is studied. Excellent agreement between experimental and calculated spectra is obtained using potential function V(?) = ½ Σ_NV_n (1 – cosn ?) with V₁ = V₂ = V₃ = 0 cal mol^?1 and V₄ = 500 cal mol^?1.     

Etude par RMN. de polyaminocarboxylates de terres rares,III. Hydroxyéthyliminodiacétates de praséodyme

¹H—NMR. has been used to study the chemistry of the hydroxyethyliminodiacetate complexes of praseodymium in aqueous solution. The ligand exchanges by spontaneous dissociation of the metal-bis-hydroxyethyliminodiacetate (1:2 complex) and of the metal-bis-hydroxyethyliminodiacetate hydroxocomplex, by acid catalysed dissociation of the 1:2 complex, and by a bimolecular process involving the free ligand and the 1:2 complex or the ternary hydroxo-complex. The ligand exchange rate constants are given and the mechanisms discussed.     

Etude par RMN des 2-2′ -Dihalogeno-diethylethers—II: Effet de Solvant

Solvent effects on compounds of formula (X? CH₂? CH₂)₂O with X ? Cl, Br, I have been studied. The rotamer ratios have been determined for each solvent according to Lin's method and it is shown that the three compounds moved to gauche forms when increasing the medium dielectric constant. Additionally, it is shown that geminal couplings of the iodine derivative algebraically decrease on increasing the medium polarity. An attempt to correlate these variations with rotamer populations is made.     

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.