L'isopolyalthenol et le neopolyalthenol,nouveaux indolosesquiterpenes isoles de Polyalthia suaveolens, annonacees

The novel indolosesquiterpenes isopolyalthenol 3 and neopolyalthenol 4 have been obtained from Polyalthia suaveolens (Annonaceae). A pathway for the biogenesis of indolosesquiterpenes is considered.     

Synthese et etude par RMN 119Sn de nouveaux composes benzyliques organostanniques

Preparations of new benzylic organotin compounds are presented. ¹¹⁹Sn NMR studies show long range coupling constants ¹¹⁹Sn¹¹⁹Sn and intramolecular coordination of tin.     

Reactivite du tris(hydroxymethyl)aminomethane avec des nitro-aldehydes aromatiques. Synthese de nouveaux composes antimicrobiens.

Heterogeneous reaction of TRIS 1 with nitro-aldehydes leads to oxazolidines in good yield. New products are obtained as monocyclic or bicyclic compounds, and are of potential medicinal value.     

Sur les composes fluores du tellure (IV): Etude structurale de CsTeF5

CsTeF₅ was synthetized in hydrofluorhydric solution by action of CsF and TeO₂. The structure was solved by means of three dimensional Patterson synthesis (final R_w value = 0,033). This structure contains isolated TeF₅ groups which are distorted square pyramids (Cs symmetry). The apical Te-F bond distance and the basal Te-F bond distances are 1,81 , 1,91 and 1,95 Å respectivly.     

Reactivite des organomagnesiens vis-a-vis de composes acetyleniques en presence du complexe de nickel (PPh3)2NiCl2

In the presence of dichlorobis(triphenylphosphine) nickel, acetylenic compounds undergo stereospecific or stereoselective syn addition of non recuding Grignard reagent. With reducing Grignard reagents, addition and reduction reactions are observed. These reactions yield vinylic organomagnesium compounds. A catalytic process is proposed to explain the experimental results.     

Synthese de dihydroxy phenacylidene triphenylphosphoranes nouveaux precurseurs de composes flavonoides: Synthese d'hydroxy-6 et hydroxy-7 chromones.

The synthesis of two new dihydroxy phenacylidene triphenylphosphoranes from 2,4-dibenzoyloxy and 2,5-dibenzoyloxy acetophenones is described. By acylation of the hydroxyl groups of theses ylids, intramolecular of the esters carbonyl group and hydrolysis of the second esters group, some 6-hydroxy and 7-hydroxy chromones are prepared with good yields.     

Sur les composes chlorofluores de l'antimoine III : etude structurale de CsSbClF3

CsSbClF₃ was prepared in aqueous solution with CsCl and SbF₃. The structure was solved by means of a three dimensional Patterson synthesis. Antimony shows an unpublished coordination 8 : 5 fluorine atoms, 2 chlorine atoms and the lone pair of electrons E situated on the corners of a hendecaedron     

Etude RMN du 13C de composes fluoroaliphatiques et de tensioactifs non ioniques perfluoroalkyles

Carbon-13 chemical shifts, spin-lattice relaxation times and nuclear Overhauser enhancement factors at 28°C are reported for a series of polyfluoroaliphatic compounds :

, and perfluoroalkyl nonionic surfactants C_mF_2m+1CH₂(OC₂H₄)_nOH with m = 6, 7 and n = 3, 4, 5, 6 and C₆F₁₃CH₂CH₂CONH(C₂H₄O)_nH with n = 3, 4. The influence of the perfluoroalkyl group on the ¹³C chemtcal shifts of the neighbouring hydrogenated carbons is discussed in terms of hyperconjugative type interactions between lone electron pairs on fluorine and the neighbouring CC or CO bond. Relaxation data show similar flexibilities of the fluorinated chains in the different molecules investigated. Nonionic surfactants exhibit segmental motions in both the hydrophobic perfluoroalkyl and the hydrophilic polyoxyethylene chains ; these motions appear to be similar to those of the analogous hydrogenated surfactants.     

Etude par RMN 13C Et 199Hg de composes oxobromo- et dioxomercuriques

Organomercuric compounds of the general formula

and [RCOCH(R′)]₂Hg, obtained from three ketones, 2,2-dimethyl 3-pentanone, 1-mesityl 1-propanone and 1-mesityl 1-ethanone, have been studied by ¹³C and ¹⁹⁹Hg NMR techniques. Coupling constants J(CHg) and J(HgH) are consistent with C-metalated species; in each case the values of δ(C(2)) and J(C(2)H) observed are higher than expected for purely sp³ carbon. The contribution of O-metalated species and hyperconjugative effects are discussed. For two dioxomercuric compounds (R′  Me, R  t-Bu, mesityl) the existence of diastereoisomers is suggested from ¹⁹⁹Hg NMR data.     

Analyse conformationnelle theorique (methode CNDO/2) de quelques composes ditertiobutyles du phosphore (III) P(t-Bu)2X (X = H,F)

Optimized geometries and conformational analysis of P(t-Bu)₂F and P(t-Bu)₂H molecules are investigated within the framework of the CNDO/2 approximation. The CPC angles are found to be equal to 114° in agreement with the 113°8 value provided by X-ray study of the trans-NiBr₂ [P(t-Bu)₂F]₂ square planar complex. Therefore, it seems that the highest XPX value in the PX₃ series is observed for di-tert-butyl derivatives and not for the tri-tert-butylphosphine.     

Etude par diffraction X et par spectrometrie de vibration de composes de coordination des halogenures d'aluminium avec l,acetonitrile: analyse vibrationnelle des cations AlCl(CH3CN)2+5 et AlBr(CH3CN)52+

The compounds AlX₃-2CH₃CN and AlX₃-1.66CH₃CN (X = Cl, Br) are prepared in order to study the vibrational properties of AlX(CH₃CN)²⁺₅. The different chemical phases obtained are characterised by X-ray diffraction. It is shown that AlCl₃-2CH₃CN and AlBr₃-2CH₃CN are isomorphic and unit cell parameters are determined. The spectra of the cations AlX(CH₃CN)²⁺₅ in the 600-50cm^?1 range are interpreted by comparison with those of Al(CH₃CN)³⁺₆ and from the data obtained from H-D substitution. Analysis of the spectra of the complexes AlX₃-1,66CH₃CN enables the formula [2AlX^?₄: AlX(CH₃CN)|²⁺₅] to be postulated.     

Determination des structures de deux ferrites mixtes nouveaux de formule BaLa2Fe2O7 et SrTb2Fe2O7

The structures of the two new ferrites BaLa₂Fe₂O₇ and SrTb₂Fe₂O₇ with tetragonal symmetry have been resolved by X-ray and neutron diffraction performed on powder samples. In both compounds the arrangement of atoms present a close resemblance with the idealized Sr₃Ti₂O₇ structure. It consists of a packing along the c axis of two different blocks. One is formed by the adjunction of two perovskite cells and the other one by a halved rocksalt Sr(Ba)O cell. The iron cation lattice is built by infinite double layers perpendicular to the c axis with the shortest Fe³⁺Fe³⁺ distances inside the double layers much shorter than between the layers. In BaLa₂Fe₂O₇, Ba²⁺ is located on a regular 12-coordinated site and La³⁺ in a regular 9-coordinated polyhedron. Fe³⁺ is surrounded by five oxygen neighbours at 1.98 Å, building a rather regular tetragonal pyramid, with a sixth oxygen at 2.25 Å. In SrTb₂Fe₂O₇, Sr has only eight close neighbours at ～2.80 Å and four more distant at 3.15 Å. Tb³⁺ has seven close neighbours, six building a distorted octahedron with the largest triangular face capped by the seventh oxygen. Fe³⁺ again has five neighbours, but due to the lowering of the symmetry, the square pyramid has become a distorted trigonal bipyramid.     

Sur les composes fluores et oxyfluores du tellure (IV) : Synthese,caracterisation et etude structurale de l'acide trioxotetrafluoroditellurique (IV), H2Te2O3F4

The trioxotetrafluoroditelluric (IV) acid, H₂Te₂O₃F₄, was synthetized in fluorhydric solution and characterized by X-ray powder diffraction. The structure was solved by means of three-dimensional Patterson synthesis (final R value = 0,026). This structure is characterized by Te₂O₃F₄ groups linked by hydrogen bonds to form a very distorted diamond network.     

Etude vibrationnelle des composes (C4H4P)Mn(CO)3 et [C4H2(CH3)2P]Mn(CO)3 et calcul du champ de force du cycle C4H4P complexe

The Raman and infrared spectra (4000200 cm^?1) of (C₄H₄P)Mn(CO)₃ and (C₄D₄P)Mn(CO)₃, and of [C₄H₂(CH₃)₂P]Mn(CO)₃ and [C₄D₂(CH₃)₂P]Mn(CO)₃ in the liquid and solid states (10–400 K) have been investigated. A complete vibrational assignment is proposed and valence force fields of the (C₅H₅) and (C₄H₄P) cycles are compared. From these results, it is clearly shown that the (C₄H₄P) rings are more electrophilic and weaker π-electron donors than (C₅H₅) rings, this is in agreement with their chemical behavior.     

The crystal and molecular structure of acetato(2-phenylazophenyl-C,N′)tellurium(II) and (2-phenylazophenyl-C,N′)thiocyanatotellurium(II)

The crystal and molecular structures of acetato(2-phenylazophenyl-C,N′)tellurium(II) (I) and (2-phenylazophenyl-C,N′)thiocyanatotellurium(II) (II) have been determined. The structure of the former consists of discrete molecules in which weak intramolecular Te?ctdot;O [2.953(4) Å] interactions occur. However, the structure of the latter compound shows a very weak intermolecular Te?ctdot;N [3.535(3) Å] interaction, which links the molecules into dimers. The coordination about tellurium can be considered as approximately trigonal bipyramidal with the carbon atom and the two lone pairs in the equatorial positions and either N and O(I) or N and S (II) in the axial positions.     

Dienophilie des cyano-1 enamines,nouveaux equivalents de cetenes pour les cycloadditions de diels-alder1

The Diels-Alder reactivity of two captodative olefins, 2-morpho-lino-acrylonitrile $\text{15}$ and 2-(N-methlanilino) -acrylonitrile $\text{16}$, towards four conjugated dienes is evaluated.In every cases, isomeric {4+2} cyclo-adducts are obtained.With olefin $\text{15}$ yields are better than with olefin $\text{16}$. The adducts are easily transformed in to the corresponding ketones by a mild hydrolysis of the α-aminonitrile group. Thus, the 1-cyanoenamines can be considered as good ketene equivalents very useful for the synthesis of unsaturated cyclohexanones.     

Ordered perovskites in the A(Li1/4Nb3/4)O3-A(Li2/5W3/5)O3 (A=Sr, Ca) systems

Single-phase 1:2 B-site ordered perovskites are formed in the (1−x)A²⁺(Li_1/4Nb_3/4)O₃-(x)A²⁺(Li_2/5W_3/5)O₃ systems, A²⁺=Sr and Ca, within the range 0.238?x?0.333. The X-ray and electron diffraction patterns are consistent with a P2₁/c monoclinic supercell, , , , β≈125°, where the 1:2 order is combined with b⁻b⁻c⁺ octahedral tilting. Rietveld refinements of the ordered A(B^I_1/3B^II_2/3)O₃ structures give a good fit to a model with B^I occupied by Li and Nb, B^II by W and Nb, and a general stoichiometry (Sr,Ca)(Li_3/4+y/2Nb_1/4−y/2)_1/3(Nb_1−yW_y)_2/3O₃, y=0.9x=0.21-0.30. The Sr system also includes regions of stability of a 1:3 ordered phase for 0.0?x?0.111, and a 1:1 ordered double perovskite for 0.833?x?1.0. The formation of the non-stoichiometric 1:2 ordered phases is associated with the large site charge/size differences that can be accessed in these systems, and restricted by local charge imbalances at the A-sites for W-rich compositions. These concepts are used to generate stability maps to rationalize the formation of the known 1:2 ordered oxide perovskites.