Etude par RMN protonique d'heterocycles voisins de l'oxazaphospholane-1,3,2. II—Le diméthylamino-2 méthyl-3 oxazaarsolane-1,3,2

The ¹H NMR spectrum of the 2-dimethylamino-3-methyl 1,3,2 oxazaarsolane is very sensitive to solvent and temperature. A complete analysis of the spectrum at ?48 °C in deuteriated toluene shows that the molecule exists in a preferred conformation in the C-4? C-5 region. The spectrum, corresponding to an A₂X₂ system in nitrobenzene at +31 °C, indicates free movement around that bond. At higher temperatures a new coalescence phenomenon is explained by inversion of the As atom.     

Dérivés Alléniques du Phosphore. Influence de l'État de Coordination du Phosphore et de la Nature des Radicaux Liés au Phosphore sur les Signes de J(P?H)

The signs of the phosphorus-proton coupling constants in various allenic organophosphorus compounds have been determined by either analysis of the AB₂X spectra or double resonance. Probable absolute signs have been obtained by taking ³J(P? H) as positive. In allenic phosphine oxides, the following signs are obtained: ²J(P? H) +ve, ³J(P? H) +ve, ⁴J(P? H) ?ve, ⁵J(P? H) +ve and the ⁴J(P? H) coupling constant varies mostly with the inductive effect of the substituents bound to the phosphorus atom. In allenic phosphines, these sings are: ²J(P? H) +ve, ³J(P? H) +ve, ⁴J(P? H) ?ve and +ve and the ⁴J(P? H) coupling constant varies with both the inductive and resonance effects to the substituents. This coupling constant is negative except when the phosphorus atom is bound to groups which are electron-donating by resonance effects. These results are discussed in relation to the pπ? dπ bonding in phosphine.     

Structural studies by 1H and 13C d.n.m.r.: I—barrier to trans-cis isomerization in aliphatic enamino ketones of the type R?CO?CHCH?NHR1

D.n.m.r. studies have been performed involving the measurement of rates of trans-cis isomerization of aliphatic enamino ketones of the type R? CO? CH?CH? NHR₁, by means of equilibration experiments and the method of finding the coalescence temperature. Simultaneous observation of the rates of dynamic N? H proton exchange and isomerization processes by the latter method has facilitated the assignment of the rate-determining reaction step in the title compounds studied in aprotic solvents. Thermodynamic parameters are discussed and the dipolar transition state to isomerization in a nonpolar solvent indicated. The dynamic behaviour of all protons undergoing exchange between the possible sites in the molecule are discussed in the light of our own experiments and other recent data.     

Dérivés Alléniques de l'Étain,du Plomb et du Mercure. Signes Relatifs des Constantes de Couplage Métal-Proton á Travers Deux et Quatre Liaisons

Satellites corresponding to metal-proton coupling constants through two and four bonds are observed in PMR spectra of Pb, Sn and Hg allenic derivatives. The relative signs of these coupling constants are deduced from analysis of the satellite spectra: ²J(X? H) and ⁴J(X? H) are of opposite signs for X = ²⁰⁷Pb, ¹¹⁹Sn, ¹¹⁷Sn and of same sign for X = ¹⁹⁹Hg. Probable absolute signs of reduced coupling constants are discussed in relation to published data: ²K(X? C? H) is probably positive for X = ²⁰⁷Pb, ¹¹⁹Sn, ¹¹⁷Sn and ¹⁹⁹Hg. ⁴K(X? C?C?C? H) is probably negative for X = ²⁰⁷Pb, ¹¹⁹Sn, ¹¹⁷Sn and positive for X = ¹⁹⁹Hg.     

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.     

Kernresonanz-spektroskopische Untersuchung protonierter Stickstoffverbindungen in Trifluoressigsäure

The nuclear magnetic resonance spectra of a series of protonated organic nitrogen compounds in trifluoroacetic acid solution have been studied. A direct correlation between the exchange rate of the ammonium protons and the acidity constant of the functional group is established. Substituted anilinium and pyridinium ions with pK values below 4 show coalescence for the signals of N^⊕? H protons and disappearence of the coupling with the α protons.     

Etude de composés d'addition des acides de Lewis XXVIII. Constantes de Hammett et vibration carbonyle des composés formés par TiCl4 et SbCl5 avec des chlorures de benzoyle parasubstitués

The adducts of benzoyl chlorides p-substituted by CH₃O? , CH₃? , and H? with the electronic acceptors SbCl₅ and TiCl₄ have been prepared, and the IR. absorption spectra of the solid products studied.     

Determination Rapide de la Configuration Cis Trans des Alcenes CH?CHCH? Utilisation des Complexes de Terres Rares

In Z? CH? CH?CH? Y compounds (Z or Y being an alkyl group) the ethylenic part of the spectra is often very complex and the ³J(H? C?C? H) coupling constant which is a good tool for determining the configuration, is not easily determined. We have studied such allylic derivatives and many configurations have been assigned through stereospecific synthesis. Except a very few cases, δ CH(Z) of the cis isomer is larger than δ CHZ of the trans isomer. In alcohols RCH?CH? CHOHR′ the stereoisomers behave differently in solutions with europium, praseodymium, holmium and dysprosium complexes. The spectra of the trans isomers remain strongly coupled but ³J(H? C?C? H) becomes easy to measure in the cis compounds.     

Synthèse de sucres aminès ramifiés II. Synthèse et réactions de spiro-aziridines. Communication préliminaire

Treatment of 3-C-cyano-1,2:5,6-di-O-isopropylidene-3-O-(toluene-p-sulfonyl)-α-D -allofurannose with AlLiH₄ or RMgX yields spiro-aziridines with two identical substituents on C(3′) (? H, ? CH₃, ? C₂H₅). Reactions of these products and their derivatives are briefly described. If the C(3′) substituents are protons, the aziridine ring is easily opened. In acidic media (HCl), an amino-sugar containing the branched chain ? CH₂Cl is produced; with hydrogenation, a ? CH₃ branched chain results. If the C(3′) substituents are methyl groups, the aziridine ring cannot be opened neither with HCl nor with hydrogen. The acetylated derivative of this latter compound rearranges to the corresponding allylamide with HCl. For both types of spiro-aziridine, the nitrous deamination leads to the corresponding alkene.     

Modele de nitrogenase. activite de complexes molybdenecysteine dans la reduction de l'acetylene

The complex Mo₂O₄(cys)₂^2? disproportionates nito Mo^VI and Mo^III at a _pH higher than 9. Under our experimental conditions, the reduction of acetylene by molybdenum-cystéine complexes does only occur after addition of naBH₄·Mo^III; the molybdenum(III) species seems to be responsible for this activity.     

Analogues de la showdomycine à activité antitumorale

Antitumor showdomycin analogues A series of 3-glycosylidenesuccinimides ( 3 ) and 3-glycosylidene-1-phenyl-succinimides ( 5 ) have been prepared in good yields using a Wittig reaction. In each case, the preponderant, or even the exclusive, isomer formed was E. As expected from orbital considerations, the contribution to the conformational equilibrium of the rotamer whose H? C (γ) and H? C(δ) bonds were antiparallel was low. One of these succinimide derivatives 3a showed interesting anticancer activity, similar to that of the sugar enone C. These compounds probably act as somewhat selective alkylating agents.     

Etude par Résonance Magnétique Nucléaire de dioxaphosphorinanes-1,3,2 à liaison P?N extracyclique. Exemple de changement d'orientation de la liaison P?N

The ¹H NMR spectra of several 1,3,2-dioxaphosphorinanes bearing an extracyclic P? N bond have been analysed. The ³J(POCH) couplings are strongly dependent upon the orientation of the bond around the phosphorus atom. Depending upon the nature of the bonds attached to the nitrogen atom, the dioxaphosphorinane ring may adopt either a fixed chair conformation with the P? N bond in the axial or equatorial orientation, or it may be in equilibrium between two chair conformations where the P? N bond is alternately axial or equatorial. The equilibrium is fast on the NMR time scale.     

Vibrations de valence C?H/C?D fondamentales et harmoniques de dérivés halogénés du méthane et du deutériométhane

The fundamentals and overtones of the C? H stretching vibrations of a number of halogenated methanes and deuteriomethanes are compared with a hypothetical model consisting of isolated groups. The anharmonicity constants are evaluated and lie between ?20 cm^?1 and ?130 cm^?1 for the C? H and C? D stretching vibrations. The value of the anharmonicity constant for a coupling between two different modes of vibration is always greater (in absolute numbers) than its value for an overtone of one frequency. The constant is larger for a symmetric mode than for an asymmetric mode in the case of a C? H vibration; the contrary is true for a C? D bond. Complex interactions between different vibrations often strongly modify the spectra of the overtones. It is shown, however, that the conception of an isolated group is helpful for evaluating the spectra of these substances.     

Sélénophènes substitués. Additivité de l'influence des substituants sur les couplages J(H?H) et J(Se?H)

The spin-spin coupling constants J(H? H) and J(Se? H) of 2- and 3-substituted selenophenes, whose signs have been obtained by double resonance experiments, have been correlated with the reactivity constants F and R of Swain and Lupton by means of linear equations J = i + fF + rR. The relative inductive and mesomeric contributions to the coupling constants are discussed. Substituent effects on J(H? H) and J(Se? H) are found to be additive in 2,4-disubstituted selenophenes. In agreement with experimental results, this additivity relationship indicates that ³J(Se? H) becomes negative in 2,4-dinitroselenophene. Evidence is given from long range coupling constant data that 2-formylselenophene exists almost exclusively in the Se? O cis conformation and 3-formylselenophene in the Se? O trans conformation.     

Elimination sous Impact Electronique de HCN et H· a partir de l'Indole. Comparaison avec l'Indolizine

The two primary electron impact induced fragmentations of indole, loss of HCN and loss of H?, are investigated by the examination of eleven deuterated indoles. All the hydrogen atoms are involved in HCN loss, but predominantly the 5-membered ring hydrogens. This is more pronounced in the 70 eV mass spectrum than in the metastable ions energy range, where the three positions of the 5-membered ring are equivalent. The qualitative results achieved for H? loss give clear indication of the occurrence of an isotope effect and are also consistent with the predominant loss of the 5-membered ring hydrogens, especially of the hydrogen bonded to the nitrogen atom. This behaviour is compared with the behaviour of indolizine, and the energy requirements for HCN loss from the two isomers are discussed.     

Equation de Karplus et l'Hybridation du Carbone. Correlation de la Constante de Couplage Vicinale 3J(Hi,Hj) et la Somme de Constantes de Couplages 1J(C,H)

The vicinal coupling constant ¹H? ¹H exhibits a marked hybridization dependence. The coupling constants ¹³C? ¹H could be used to correlate the Karplus type equation for calculation of ³J(Hi, Hj). The correction term to this equation is proposed.     

Heterocycles Contenant du Phosphore—V. Analyse des Spectres de Resonance Magnetique Protonique des Oxo-2 Methoxy ou Phénoxy-2, Methyl-3, Oxazaphospholanes-1,3,2: Exemples de Spectres du type ABXY

The ³¹P decoupled PMR spectra of the title oxazaphospholanes give rise to well resolved ABXY patterns. Among the eight possible solutions, six can be readily eliminated from chemical shifts considerations and the choice between the remaining two is based on tickling experiments. Good fits are observed between experimental and calculated spectra. The relative signs of the ³J(P? O? C? H) and ³J(P? N? C? H) coupling constants are given by tickling and Indor experiments. The ring conformation is discussed.     

Equilibres conformationnels de glucides au niveau de liaisons σ sp2-sp3 C-C. III Dérivés d'oximes d'aldéhydo-sucres utilisation de tris-dipivaloylméthanato-europium

A series of sugar oximes and O-methyloximes of the general formula RCH?NOR′ (R′ ? H, CH₃) have been studied by PMR. spectroscopy. These compounds exist in solution as a mixture of the syn and anti isomers. The conformational equilibrium of the syn isomers seems to consist exclusively of the eclipsed rotamers, whereas for the anti isomers there appears to be a significant contribution from bisecting rotamers. Using tris-dipivaloylmethanato-europium it is found that the α proton of the anti oximes is much more deshielded than the corresponding proton of the syn isomers, which means that the downfield shift of a particular proton does not depend exclusively on its distance from the oxygen of the oxyimino group.     

Transferts Protoniques de Sels d'Ammonium Substitues—VIII: Sels de Pyridinium 4-Substitues

The deprotonation rate 1/τ of the title compounds, [4 – R – Py H]⁺, where R = NH₂, t-Bu, Me, Cl, Br or CN, is measured using the coalescence of the pyridinic α-protons, in a mixture CF₃COOH/H₂O/HClO₄ of variable acidity Ho, at 38°C. 1/τ is a linear function k/ho of the acidity 1/ho. k is approximately proportional to the water content and independent of the salt concentration, which seems to be evidence for an exchange with an intermediate pyridine hydrate, according to: . After a preliminary ionisation step: k values, like K_A, fit a Hammett relationship (ρ = 5,05), except for R ? NH₂, and are very sensitive to the nature of R (k = 3,44 × 10² for R = NH₂ and k = 3,14 × 10⁸ M^?1 s^?1 for R ? CN), while k_H values (10¹⁰ s^?1) are not.     

Recherches dans la série des cyclitols XLIII. Sur des éthylène-cétals de cétoses dérivés du cyclopentane

The synthesis of a series of keto derivatives of cyclopentane is described. The configurations of these derivatives have been determined by chemical methods and verified by IR. and NMR. spectroscopy. The preferred conformation of the cyclopentane part of the molecule has been established by the study of intramolecular hydrogen bonds and the values of the coupling constants J_{H? C? OH} and J_{H, H}.