Synthese photochimique et etude structurale d'alcoxy-spirocetals et de trioxa-bis-spirocetals

The spiroketal systems can be obtained easily by a Norrish type II reaction applied to tetrahydropyranic ketoacetals having a carbonyl group in δ position of the acetalic hydrogen. The structures of spirans and bispirans established by IR, NMR (¹H and ¹³C show an axial conformation for the C-O bond of the tetrahydrofuran ring. With the bispirans this anomeric effect requires for some isomers a twist boat conformation of the tetrahydropyran ring.     

Synthese anionique de polymeres comportant une fonction vinylsilane a l'une ou aux deux extremites de la chaine macromoleculaire

The reaction of vinyldimethylchlorosilane with a living polymer (ω or α,ω carbanionic) leads under certain conditions to the quantitative formation of a vinylsilane group to one or two ends of the macromolecular chain.     

Synthese et etude de l'agregation moleculaire d'amines derivees de l'adamantane

Adamantanealkanamines were prepared by a new method: the wittig reaction of aminophosphonium ylides with 2-adamantanone. Conductance measurements have been employed to examine and compare the aggregation behaviour of these compounds.     

Synthese et etude spectrale de F-alkyl-4 coumarines

In this paper, we report synthesis and spectral characteristics of 24 new F-alkyl-4 coumarins and their synthetic intermediates, the corresponding F-alkyl β-keto esters. The reaction yields depend on the nature of the starting materials and the cyclisation agents. ¹H and ¹⁹F N.M.R. chemical shifts and coupling constants are assigned in every compound and a new kind of long distance H-F coupling constant ⁵J is observed and interpreted by means of geometric, steric and electronic effects as coupling through space.     

Synthese et etude de chlorotricyclopentadienylniobium(IV)

The action of cyclopentadienide anions on (Cp)_2?n(RCp)_nNbCl₂ complexes (n = 2,1 or 0; R = C(CH₃)₃) is reported. In all cases, the formation of tricyclopentadienyl complexes, identified by ESR spectroscopy, is observed. Some tricyclopentadienyl species are able to be transformed by η¹–η⁵ fluctuation. An example of a tricyclopentadienyl complex involving a stereochemical blocking is presented. By use of this intermediate a dicyclopentadienyl derivative of niobium(IV) containing two different rings is selectively synthetized.     

Synthese et etude par resonance magnetique nucleaire du carbone 13 et de l'etain 119 d'une serie de triorganostannyl-2 butanes

Optically active triorgano-2-stannylbutanes have been synthetized by different methods, one being the direct substitution of optically active s-butyl halides with triorganostannyl alkali metals. This route involves a complete or partial inversion of configuration at the chiral carbon atom. Carbon-13 and tin-119 NMR data are reported as support for the identification of eight triorgano-2-stannylbutanes. The special case of tetra(2-butyl)tin, with four identical chiral centres has been examined.     

Synthese,etude spectroscopique et magnetique de NbF4

NbF₄ is synthetized by reduction of NbF₅ by Nb. The conditions of preparation and some chemical properties are specified. The visible and near infrared spectrum is interpreted in terms of the ligand field theory, and the magnetic behaviour is investigated between 4 K and the room temperature. Comparison between experimental data and calculated values of the magnetic moment is carried out, with reference to the theory for a ²T₂ term perturbed by spin-orbit coupling and axial field component.     

Synthese et configuration absolue de deux α-ferrocenyl silanes bifonctionnels asymetriques

The preparation of two bifunctional and optically active α-ferrocenylsilanes is described. The absolute configuration of these compounds is determined by chemical correlation. Using this method it may be possible to obtain many functional and opticlly active α-ferrocenylsilanes.     

Synthese et etude de poly(ester-seq-ether)—III. Etude cinetique de la polycondensation d'oligomeres difonctionnels et de leurs modeles

The kinetics of the bulk catalysed and uncatalysed polycondensations of oligomeric ωω′ dihydroxy polyethers and ωω′ diacid polyesters are studied. A model reaction (condensation of octadecanoic acid with 1-octadecanol) is studied under the same conditions. For the model, without catalyst, the reaction order depends on the pressure. When a protonic catalyst is present, the reaction is second order and in the presence of Ti(OBu)₄ the overall order is 1 with respect to the reactants and 0.5 with respect to the catalyst. These results are compared to those of previous workers. For the oligomers, in the absence of added catalyst, the reaction is second order with respect to the acid and first order with respect to the alcohol; in the presence of Ti(OBu)₄, the reaction is first order with respect to the reactants. The rate constants and the activation enthalpies are reported.     

Synthese et configuration de l'alnincanone

Alnincanone 1, and its three diastereoisomers at C-20 and C-24, have been synthesized from dipterocarpol. The configuration of the four isomers has been defined by several independent methods; the naturally occurring alnincanone is 20S,24R.     

Synthese de polyacrylamides porteurs de groupements iminodiacetate et etude de leur pouvoir de complexation vis-a-vis de quelques cations metalliques

Water soluble polymers were prepared by topochemical reaction of sodium iminodiacetate with polymethylolacrylamide. Their complexing properties towards some metallic cations were investigated by potentiometric and spectroscopic techniques and compared with the complexing properties of iminodiacetic acid and of a model molecule of the polymer ionic unit. The results showed that polymer and model 1-1 chelates are stronger than iminodiacetic complexes. We explain this difference by participation of the amide group in the coordination of cation by the two first ligands.     

Synthese d'alkenyl et de cycloalkenyl polyflones

A method of synthesis of alkenyl and cycloalkenyl polyflones is described. It involves the reaction of a perfluoro or polyfluoro organometallic compound with an α-chloro alkyl or cycloalkyl thiocyanate. The obtained sulfide is oxidized into sulfone with m-chloro-perbenzoïc acid. Then this sulfone is transformed into vinylpolyflone by dehydrochloration.     

Structure de l'echitamidine,d'un stereoisomere et de deux regioisomeres

The relative configuration of echitamidine is established by spectral and X-ray crystallographic techniques. Three other isomers are described and a structure is proposed for them.     

Decarboxylation catalytique et quantitative d'acides arylacetiques en presence'de cuivre I

Copper(I) salts of arylacetic acids $\text{1}$ RCO₂H readily undergo a catalytic and quantitative decarboxylation in acetonitrile leading to hydrocarbons $\text{2}$ RH when the corresponding carbanions R are stabilized by resonance and/or electronwithdrawing substituents.     

Échanges inter et intra-molćulaires du proton entre deux atomes d'azote de cycles chélatés hydrazone-imine et azo-énamine

Inter- and intra-molecular exchanges of chelated proton are evaluated by NMR in arylhydrazones derived from β-keto-imines and β-diimines.     

Synthese et etude par resonance magnetique nucleaire de complexes olefiniques de l''iridium et du rhodium avec quelques bases de schiff derivees de l''aldehyde salicylique

[M(bds)(cod)] compounds (M = Ir or Rh, cod = 1,5-cyclooctadiene, bds = Schiff's base) have been studied by ¹H and ¹³C NMR.

Signals corresponding to the atoms of the double bond trans to the oxygen atom appear at higher field than those of the trans nitrogen side. ¹ and ¹³C attributions have been related by selective decoupling. Some structural data have been also obtained.     

Synthese d'acetals de cyclopentanones halogenees et deuteriees

Acetals of halogenocyclopentanones are formed in good yield from 5-chlorocyclopentenones. Their structures and stereochemistry are assigned on the basis of ¹H NMR data and confirmed by a method based on selective deuteriation. Chemical shifts and coupling constants are listed.