Relations structure-réactivité grandeurs thermodynamiques de protonation d''h''et''erocycles saturés et non saturés

Proton ionisation thermodynamical quantities ot two series of heterocyclic compounds were determined at 25°C, in an aqueous medium of constant ionic strength 0.5M KNO₃.

The first series consists of some saturated molecules, e.g., imides (pyrrolidine, thiazolidine, 2,4-thiazolidinedione, hydantoin, thiohydantoin, succinimide, parabanic acid, barbituric acid), the second one of azoles (imidazole, benzimidazole, pyrazole, thiazole, 1,2,4-triazole, benzotriazole).

The influence of the structure of these molecules on their reactivity towards the hydrogen ion was discussed, on the basis of the related ΔH° and ΔS° functions.     

Etude de l'oxydation de tétrahydroisoquinoléinols-4 diméthoxylés en 6,7 ou 7,8, et sur la réactivité du carbonyle de la tétrahydroisoquinolone-4 diméthoxylée en 6,7

Preparation of the tetrahydroisoquinolin-4-ols indicated in the title and their oxidation by different reagents (chromic anhydride, NBA, dimethylsulfoxide, Oppenauer oxidation) is reported. Only the last reaction led to the title compounds, while the other reagents (except NBA) yielded 1,2,3-trioxotetrahydroisoquinoline. Furthermore, the reactivity of 6,7-dimethoxytetrahydroisoquinolin-4-one was examined towards different carbonyl reagents.     

Synthèse de composés cyclopentaniques chiraux,di, tri et tétrasubstitués. Application à la synthèse de dérivés Oxa-13-prostanoïques

The cyclopentenecarbaldehyde 1a , acetals 2a , 2b and the cyclopentenone 2c have been transformed through regio and stereocontrolled reactions into a variety of enantiomerically pure substituted cyclopentanes. Using appropriately selected Wittig reagents, aldehyde 1a furnished the condensation products 3 , 4 , 5 . Michael addition of diethyl malonate on the α,β-unsaturated aldehyde 1a under phasetransfer conditions led efficiently to 7 . Reduction of the cyclopentenone 2c gave 21 in high yield. The cyclopentenes 2a , 2b and 23 , submitted to hydroboration-oxidation furnished the cyclopentanols 10 , 13 and 24 , respectively, in 30, 70 and 50% yields, reflecting the substitution pattern of the starting alkenes. The salient feature of these reactions is the stereospecificity due to the chiral centre of the molecules 1a , 2a , 2b and 2c , leading to compounds with two, three and four asymmetric centres. The straightforward synthesis of 11α-hydroxy-13-oxaprostanoic acid 20 is described and an approach towards the preparation of 9α, 11α-dihydroxy-13-oxaprostanoic acid 34 is also presented. The structure of these products has been determined by ¹H- and ¹³C-NMR spectroscopy.     

Transfert d'Hétéroatomes (Cl,Br, OH) lors de la Fragmentation d'Acétyléniques δ-Fonctionnalisés

The mass spectra of three δ-functionalized alkynes provide evidence for the migration of chlorine, bromine and hydroxyl towards the unsaturated portion of the molecules. The strong resemblance between these spectra and those of the isomeric allenes suggests that an acetylene→allene isomerization occurs after electron impact.     

Ionisation Chimique de Composés Aromatiques Nitrés

The collision induced dissociations of [MH – 30]⁺ ions observed in the chemical ionization (methane) mass spectra of some nitro aromatic compounds show that these ions are formed by reduction in the ion source with subsequent protonation and not by the previously reported losses of NO^· from the protonated molecular ions.     

RMN du 13C de Composés Méthylés Soufrés

A ¹³C NMR study of a series of methyl sulphur compounds is described. The results are discussed in terms of the deshielding effects on the methyl carbon exerted by –SH, –SMe, –SSMe, –SSEt, –SSMe, –SC(O)Me, –SC(S)Me, –SC(S)SMe. The ¹³C NMR chemical shifts of a series of S-methyl thioesters and dithioesters are compared with corresponding esters and connected with chemical properties.     

Cyanohalogénométhylidènetriphénylphosphoranes. Note de Laboratoire

Cyanohalogenomethylidenetriphenylphosphoranes Iodo-, bromo and chlorocyanomethylidenetriphenylphosphoranes are described as well as a procedure for the in situ generation of cyanofluoromethylidenetriphenylphosphorane. These ylides are reactive towards aldehydosugars.     

Préparation de polyesteramides alternés

The polycondensation of hydroxyamido acids of general formula HO-R₁-CO-NH-R₂-COOH provides alternating polyesteramides only when R₁ and R₂ are alkyl groups. These aliphatic alternating polyesteramides, according to their structural high regularity, possess a more important content of interchain hydrogen bonds than the random copolymers. The higher melting point of the random copolymers is attributed to the heterogeneity of amide group partition in the chain. The existence of a benzyl group in the structure of the hydroxyamido acids reduces the polycondensation ability and the molecular weights of the products are low. These aromatic monomers are thermally degraded, p-toluic acid evolving; ester and amide functions stoechiometric ratio is not maintained, but infrared and differential thermal analysis show that these aromatic polyestermides keep a reasonable structural regularity.     

Réduction alkylante de quelques composés hétéroaromatiques polyazotés

The reduction-aldylation of quinoxaline, phthalazine and pyrido[2,3-b] pyrazine by potassium borohydride in a carboxylic acid medium is described. Formic, acetic, chloroacetic and propinic acids were used. The diazine ring of the molecule was reduced and alkylated into an N,N¹-dialkyltetrahydro compound. With quinoxaline and formic acid, N-formylation may be an important factor. Sodium borodeuteride allows one to prepare an hexadeuterated compound.     

Etude par spectrométrie de masse de l'ionisation de benzonitriles,de phénylacétonitriles et de N,N-diméthylanilines substitués

Molecular ionization potentials for series of compounds of the type X? C₆H₄? CN, X? C₆H₄CH₂? CN and X? C₆H₄? N(CH₃)₂ have been measured using the retarding potential difference technique (RPD. technique). The effect of the various substituents X is better correlated through the electrophilic Brown σ_p⁺ constants than through Hammett's σ_p values. No meta-para orientation effect is observed. For all the disubstituted phenyl compounds studied, the effect of the second substituent is affected by the electron-releasing power of the original substituent. Ionization potentials calculated by using the semi-empirical method of equivalent orbitals are in good agreement with the experimental values.     

Etude de la fragmentation par impact électronique en ions positifs et négatifs de dérivés nitrés de l'amino-2-benzothiazole

Study of Positive and Negative Ions Electron Impact Fragmentation of 2-Amino-benzothiazole Nitro Derivatives The positive and negative ions mass spectra of 2-amino-4,6-dinitrobenzothiazole ( 1 ), 2-amino-4-nitrobenzothiazole ( 2 ), 2-amino-6-nitrobenzothiazole ( 3 ) are reported and discussed. These compounds give an intense molecular ion and show interesting fragmentations in both positive and negative ions spectra. Specific ¹⁵N-labelling was used in order to confirm the fragmentation patterns.     

Synthèse de dérivés indoliques substitués in 7

The synthesis and some aspects of the chemical reactivity of 7-acetyl-, 7-benzoyl- and 7-bromoindoles are described.     

Dérivés de l'hydroxyméthyl-5 furfural. I. Synthése de dérivés du di- et terfuranne

Addition of α, β-unsaturated sulfones or ketones to 5-hydroxmethyl-furaldehyde or related furanaldehydes in the presence of a thiazolium salt gives di or tetraketonic furan compounds. Dehydrative cyclizationled to di- and terfuryl derivatives.     

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.     

Reactivité de composés carbonylés avec des cétènes en présence d'alkoxydes de titane ou de zirconium. 3e communication

Reactivity of Carbonyl Compounds with Ketenes in the Presence of Titanium or Zirconium Alkoxides The reaction of ketene or dimethylketene with aldehydes or ketones in the presence of titanium or zirconium alkoxides gives essentially β-hydroxyesters. By polyinsertion of ketene and aldehydes in the Ti? O bond, di- tri- and tetraesters are formed. An excess of ketene produces acetyl derivatives of esters and 6-alkyl-3,4,5,6-tetrahydro-2,4-pyrandiones.