Françoise Duboudin

A new practical synthesis of silyl enol ethers : Part.I. From simple aldehydes and ketones

Abstract A new, practical route to enoxysilanes is described from simple enolizable aldehydes or ketones, using the trimethylchlorosilane-sodium iodide—tertiary amine reagent in acetonitrile. From certain aldehydes, an onium intermediate has been isolated. A conformational study of this onium intermediate and a thermal unimolecular syn-elimination process may explain the stereoselectivity of the reaction. Such an interpretation can be extended to all the aldehydes and ketones considered, Steric factors related to the nature both of the carbonyl derivative and of the amine play a capital role for the regio- as well as for the stereo-control of the reaction

A new practical synthesis of silyl enol ethers : II. From α,β-unsaturated aldehydes and ketones

Abstract In acetonitrile as the solvent and in the presence of a tertiary amine the trimethylchlorosilane/sodium iodide (trimethyliodosilane “in situ”) reagent provides the corresponding siloxy dienes when reacted with α,β-unsaturated series. These reactions occurs via the formation of 1,2 or -1,4 onium salt intermediates.

Methode simple pour la synthese rapide et stereoselective d'enoxysilanes d'aldehydes et de cetones

A new highly regio- and stereo-selective method for the preparation of enoxysilanes, viz. treatment of Me3SiCl, NaI, Et3N with enolizable aldehydes and ketones is described.

LiTaO3 ceramics obtained by a gelation process

Abstract LiTaO3 powders have been prepared by appropriate hydrolysis of lithium and tantalum alkoxides. Ceramics with high shrinking coefficients have been obtained by sintering of the particles at 1150°C.

Mise en evidence de la formation de R2MMR2 a partir de disila-1,2 et digerma-1,2 cyclohexenes-4

Abstract Intermediates with π-bonded Si or Ge are generated during gas phase pyrolysis of 1,2-disila- or 1,2-digerma-cyclohex-4-enes. Compounds such as R2MMR2 are successfully trapped by addition or [2 + 2] and [4 + 2] cycloadditions. These results were proved by mass spectrometry.

Elaboration of LiNbO3 ceramics from sol–gel process powders

LiNbO 3 powders have been prepared by appropriate hydrolysis of lithium and niobium alkoxides using a sol-gel process. Ceramics with pretty high shrinkage coefficients and compactness have been obtained by sintering of the particles at 1075 °C.

Composes organometalliques a cycle moyen : VI. Mise en evidence d'une interaction transannulaire O—Si en serie silacyclanique par spectrometrie de masse et resonance magnetique nucleaire de 29Si

Abstract A mass spectral study of a series of silacyclanones with 9—13-membered rings revealed the existence of the ion C 2 H 7 OSi ( m/e 75) whose formation was interpreted as resulting from a transannular interaction between the carbonyl oxygen and silicon. The 29 Si NMR results were in good agreement with the existence of this interaction.

NMR study of the sol-gel preparation steps of a crystallized LiTaO3 powder

Abstract Samples with a composition close to LiTaO 3 were prepared by solid state reactions from Li 2 CO 3 and Ta 2 O 5 powders and by a sol-gel method using alkoxides of lithium and tantalum. The successive steps of the LiTaO 3 preparation process were followed by 1 H- and 7 Li-NMR spectroscopy, showing the formation of LiTa(OC 2 H 5 ) 6 in both ethanol and hexane, the xerogel evolution vs. the heat treatment and the various crystallization steps. Furthermore, the 7 Li v q quadropolar splitting is shown to be dependent on the stoichiometry of the samples, i.e. on the Li:Ta atomic ratio.

Catalyseurs pour la transformation de polydiméthylsilanes en polycarbosilanes

Abstract The conversion of polydimethylsilanes into the corresponding polycarbosilanes has been studied using liquid monomeric catalysts such as B(OR)3 (R = Me, Pr, SiMe3) or the BN bonded compounds: Me2BN(SiMe3)2 and B(NEt2)3. Using this route it is possible to obtain polycarbosilanes which are more stable than the “Mark III” synthesized by the Yajima route and have a smaller polydispersity. These precursors obtained at 380–400°C do not require the use of an autoclave.

Sur la synthese de derives C-silicies d'aziridines

Abstract Silyl bromo azides obtained from alkenyl silanes are transformed by LiAlH 4 reduction to C-silyl-substituted aziridines.