Etude par RMN 1H des effets de solvant sur les déplacements chimiques et les couplages vincinaux des benzothiénopyridines

The solvent/solute interactions of four isomeric benzothienopyridines (parent compounds) have been investigated by ¹H n.m.r. A close study of the second-order spectra shows: (i) a preferential orientation of the solvent molecules (acetone) surrounding the pyridine ring; (ii) large variations in the coupling constants of the benzenic part of the benzothienopyridines as a function of the solvent; (iii) a preferential interaction of the pyridine ring in collision complexes with benzene. These results can be applied to a comparative study of the complexes between DNA base pairs and intercalating derivatives.     

Evolution des complexes catalytiques de rhodium supportes sur polymeres en catalyse d'hydrogenation

A set of styrene—chloromethylstyrene—divinylbenzene macroporous copolymers was phosphinated and treated with chlorocarbonyl rhodium and chlorophosphino rhodium complexes. The influence of the porous texture and functional group density of the resin on phosphination, fixation of the complexes and their extractibility by triphenylphosphine was studied. Measurement of their catalytic activity with respect to hydrogenation of hexene and benzene was carried out, before and during an ageing treatment under hydrogen or argon for up to 30 days. Results are very complex and suggest the existence of several families of active sites, their nature being discussed. Once again it is found that the structure of the support has a large influence on the evolution of catalytic activity.     

Effets de micelles cationiques sur l'hydrolyse alcaline d'acetanilides a groupe acyle active par des substituants electro-attracteurs

Micellar effects of CTAB upon the alkaline hydrolysis of CF₃-CO-N(CH₃)C₆H₅, CHCl₂-CO-N(CH₃)C₆H₄X and CH₂Cl-CO-N(CH₃)C₆H₄X, (X=p-OCH₃H,p-Cl) are reported. Variations of k_obs, and of kinetic order of the reaction with respect to HO^? ion, are interpreted as an acceleration of HO^?-catalyzed steps, and a decrease of catalysis by water for decomposition of tetrahedral intermediates; these two effects oppose each other in HO^? and H₂O catalyzed steps. Differences between micellar and DMSO effects suggest a very small local concentration of HO^? ions in micelles.     

Etude theorique des effets de substituants dans les cycloadditions dipolaires-1,3

A theoretical study of substituent effects on 1,3-dipolar cycloadditions has been carried out by the LCAO-SCF-MO method. The potential energy hypersurfaces for ten reactions and the electronic and energetic properties of the transition states have been investigated.     

Influence des effets de substituants sur la protonation de la pyridine

Standard thermodynamic values of proton ionisation of 3 substituted (Cl?, Br?, I?, C₂H₅? and CH₂CN?) pyridine derivatives are determined at 25°C, in an aqueous medium of ionic strength 0.5 M KNO₃.Free energies are deduced from equilibrium constants log K potentiometrically calculated. Enthalpies are obtained from calorimetric measurements.ΔG^o, ΔH^o and ΔS^o values are discussed in the context of the results of our earlier studies on this subject.The Hammett plot corresponding to the thirteen systems examined gives the proton ionisation constant of a substituted pyridine from the equation log K = 5,48 – 5,94Σσ.Besides, a linear relationship is found between ΔG^o and ΔH^o, which confirms the observation made previously in other series of pyridine derivatives.     

Influence des interactions de torsion dans les reactions d'addition sur les cyclohexanones. interpretation generale du deroulement sterique des reactions des hydrures ou des organomagnesiens sur les cyclohexanones

The addition of allyl and butenyl Grignard reagents to 4-t-butylcyclohexanone affords a greater proportion of the equatorial alcohols than is formed from the corresponding saturated Grignard reagents (propyl and s-butyl). In the case of the allyl Grignard reagent, the equatorial alcohol is the major product. Lithium aluminium hydride reduction in ether at 0° of cis and trans 4-t-butyl-2-methyl-cyclohexanone and cis and trans 4-t-butyl-2-chlorocyclohexanone affords mixtures of epimeric alcohols in ratios of equatorial to axial OH 8.4:1, 20:1, 4.2:1, and >70:1 respectively. These results fit in well with the view that polar interactions and torsional strain are both important in determining the steric course of the reaction.     

Action des perfluoroalkylcuivre(I) sur les perfluoroalkylethylenes

A series of new polyfluorinated dienes 3, containing the novel -CFCHCHCF-, pattern has been synthesized (50–70% yields) by reacting perfluoroalkyl iodides with perfluoroalkyl-ethylenes in the presence of copper. The monoalkenes R_fCFCHCH₂CF₂R′_f and the saturated compounds R_fCF₂CH₂CH₂CF₂R′_f were obtained by varying the experimental conditions. The ¹H and ¹⁹F NMR spectra are analysed and the reaction mechanism is discussed.     

Addition thermique des iodo-1-perfluoroalcanes sur les perfluoroalkylethylenes

We have undertaken a study of the thermal addition of 1-iodo-perfluoroalkanes (C_nF_{2n + 1}I where n = 4, 6, 8) to perfluoroalkylethylenes (C_nF_{2n + 1} CHCH₂ where n = 4, 6, 8). Structures of the reaction products were established through spectroscopic or chemical identification and the optimal conditions for obtaining 1,2-bis(perfluoroalkyl)iodoethanes determined. The good yields thus obtained demonstrate the utility of this method of perfluoroalkylation.     

Cycloaddition des diazoalcanes sur les alcenes et alcynes disubstitues

Theoretical PMO predictions are in accord with the reactions of diazoalkanes (diazomethane, diazoethane, 2-diazo propane and phenyldiazomethane) with dipolarophiles (ArCHCHCOR′ and ArCCCOR′). The influence of secondary interactions on orientation of cycloaddition are demonstrated in certain cases.     

Aspect energetique de l'agregation des tensioactifs cationiques

The critical micelle concentrations and the enthalpies of micellization of alkyltrimethylammonium bromides having dodecyl, tetradecyl and hexadecyl hydrocarbon chains have been studied using surface tension and calorimetry measurements as a function of temperature. As expected, the change of critical micelle concentrations is very small with an increase of temperature of 10 deg whereas we observe a drastic change of the enthalpies of micellization. As it has been found by applying the Van't Hoff law to thecmc values at different temperatures, the calorimetric measurements show that the enthalpy of micellization, exothermic above a minimal temperature, becomes endothermic below this temperature.     

α- Addition des amines sur les glycosyl isonitriles.

α-Addition reactions of glycosyl isonitriles with primary and secondary amines allowed to prepare substituted glycosyl formamidines representing good precursors in the synthesis of nucleosides.