J. Dedier

Nouvelles Méthodes de création de liaisons siliciumcarbone À partir de chlorosilanes VI. Double silylation en 1,4 de dienes conjugués

Abstract In hexamethylphosphoric triamide and in the presence of magnesium, triorganochlorosilanes react with conjugated dienes to yield 1,4-addition products. In the aliphatic series the diorganodichlorosilanes lead to the formation of 1-sila-3-cyclopentenes.

Etude de l'obtention d'enoxysilanes par action du triethylsilane sur des cetones enolisables, aliphatiques ou cyclaniques, en presence de catalyseurs au nickel

Abstract The preparion of alkoxysilanes and alkenoxysilanes has been achieved by the reaction of enolizable aliphatic or cyclic ketones with triethylsilane in the presence of nickel catalysts. For some catalysts, the reaction can be directed to give exclusively one or the other of these derivatives. The use of certain nickel catalysts gives very high yields of alkenoxysilanes, and this has been closely investigated.

Etude structurale d'enoxysilanes : I. Attribution des spectres de vibration du trimethylsiloxyethylene, de ses homologues deuteries et des methoxytrimethylsilanes diversement deuteries. Discussion des conformations moleculaires de l'enoxysilane

Abstract The infrared and Raman spectra of six compounds (trimethylsiloxyethylene, (CH 3 ) 3 SiOCHCH 2 , methoxytrimethylsilane, (CH 3 ) 3 SiOCH 3 , and their deuterated derivatives: (CD 3 ) 3 SiOCHCH 2 , (CH 3 ) 3 SiOCDCD 2 , (CD 3 ) 3 SiOCH 3 , (CH 3 ) 3 SiOCD 3 have been analysed. The majority of the bands observed have been assigned, in particular those due to ν(SiO). The study of the vinyl compounds shows that the enoxysilane exists in two conformers, the major being the gauche and the minor the s-cis one.

Étude structurale d'hexaalkyldisiloxanes et de trialkylalcoxyou aryloxysilanes : I. Détermination par dipolemétrie d′angles SiOC ET SiOSi

Abstract The authors have determined the dipole moments of hexaalkyldisiloxanes, trialkylalkoxysilanes and trialkylaryloxysilanes, having the formula R3SiOΣ with R=Me, Et, Pr and Σ=SiR3′ (R′= Me, Et, Pr), or Σ=Me, t-Bu, Ph, p-ClC6H4−, in benzene, dioxane and cyclohexane solutions. The atomic and electronic polarizations of these compounds have been estimated; the moments of the R3Si-O groups and oxygen valence angles of these compounds have been calculated. This study shows that the moments of the R3Si-O groups are constants, (1.10±0.05 D in benzene and 1.03 ±0.05 D in dioxane) whatever R may be, and that the oxygen valence angles in compounds of the ΣOΣ′ type vary on a wide scale according to the nature of Σ and of Σ′.

Étude structurale d'hexaalkyldisiloxanes, et de trialkylalcoxy - ou aryloxysilanes : II. Influence des facteurs électroniques et stériques sur les angles de valence de l'oxygène dans ces composés☆

Abstract Electronic and steric factors which influence oxygen valence angles in R3SiOΣ compounds (Σ=R, Ar, SiR′3) have been analysed.

Polysilylation de nitriles aromatiques à partir de chlorosilanes: synthèse d'énamines

Abstract The trimethylchlorosilane/magnesium/hexamethylphosphorictriamide system reacts with aromatic nitriles to give enamines. The silylation occurs both on the nitrile function and on the aromatic ring. It begins at the position ortho to the nitrile function of 1-and 2-naphthonitrile, and para to that of benzonitrile. This latter gives a pentasilylated enamine while tetra- and hexasilylated enamines are obtaine from 1-naphthonitrile; with 2-naphthonitrile we isolate two hexasilylated isomers. One of them, by further silylation and after rearrangement of the intermediate enamine, gives an amine including eight SiMe 3 groups. Through hydrolysis some enamines lead to aldehydes while others, treated by hydrogen chloride in ether, give amines. Further, for one of these amines we observe a rearrangement of SiMe 3 groups. A mechanism is proposed to give an explanation for these reactions.

Étude structurale d'hexaalkyldisiloxanes et de trialkylalcoxysilanes : III. Determination par diffusion rayleigh depolarisée des anisotropies optiques des groupes t-BuO et R3SiO (R = Me, Et, Pr).

Abstract Molecular optical anisotropies of some ethers, alcoxysilanes and disiloxanes have been measured both in cyclohexane solution and in pure liquid state, using depolarized light scattering. Optical anisotropies of the t-BuO and R3SiO groups (R = Me, Et, Pr) were deduced assuming an ∞-fold symmetry axis for the groups. The difference of optical anisotropy between the SiC and SiO bonds has been evaluated. The optical anisotropy invariability of the Me3SiO group has been taken to be indicative of the lack of conjugation between the two (p→d)π bonds of the SiOSi system. It has also been shown for the Et3SiO and Pr3SiO groups that the absolute value of the optical anisotropy decreases when the steric hindrance of the antagonist group increases.

Thermotropic liquid crystalline properties of semiperfluoroalkyloxyphenyl and perfluoroalkylphenyl β-D-glucopyranosides

The synthesis of two series of semiperfluoroalkyloxyphenyl and perfluoroalkylphenyl β-D-glucopyranosides is described. Their mesomorphic properties are studied by DSC, polarized optical microscopy and X-ray diffraction. All mesophases are identified as smectic A with a bimolecular in-layer arrangement.

Synthesis and characterization of thermotropic amphiphilic liquid crystals: semiperfluoroalkyl-β-D-glucopyranosides

As part of our study of the mesomorphic properties of glucopyranosides containing fluorinated chains, this paper focuses on an investigation of the liquid crystalline behaviour of nonaromatic compounds. The synthesis of eight single-tailed materials which contain a semiperfluoroalkyl chain linked to the polar glucose head group is described. Using polarized optical microscopy, DSC and X-ray diffraction all the materials were found to show only monomesomorphism, a smectic A phase with bimolecular layers. The thermal behaviour is discussed in comparison with the previously reported data on the series of parent compounds.

Etude structurale d'énoxysilanes—II. Cacul des modes normaux de vibration et du champ de forces de valence du triméthylsiloxyéthylène [(CH3)3SiOCHCH2] et de ses homologues deutériés [(CD3)3SiOCHCH2 et (CH3)3SiOCDCD2]; determination des conformations☆☆☆

Abstract The detailed analysis of the vibrational spectra of trimethylsiloxyethylene: [(CH 3 ) 3 SiOCHCH 2 ] and his deuterated derivatives [(CD 3 ) 3 SiOCHCH 2 and (CH 3 ) 3 SiOCDCD 2 ] leads to the complete assignment of the observed frequencies. The computation of the valence force field and of the normal modes of vibration in various structural hypotheses shows that these compounds exist in a preferential plane s-trans conformer, the minor one being gauche .