M. Bordeau

L'électrosynthèse, une voie simple d'accès aux di- et polysilanes

Abstract Electrochemical reduction of chlorosilanes, at constant current intensity, in a single compartment cell fitted with a sacrificial aluminium anode, is a practical and convenient route to di-, tri-, and poly-silanes.

Stereoselective electrochemical synthesis of silyl enol ethers using a sacrificial magnesium anode

Abstract The 2-pyrrolidone magnesium salt electrogenerated in an undivided cell fitted with a sacrificial magnesium anode allowed the stereoselective synthesis of Z-silyl enol ethers upon deprotonation of enolizable ketones in the presence of a complexing agent.

Molar scale electrosynthesis of ethyl-2,2-difluoro-2-trimethylsilylacetate, a difluoromethylene building block precursor

Abstract Ethyl-2,2-difluoro-2-trimethylsilylacetate has been prepared by electrolysis of ethyl-2-chloro-2,2-difluoroacetate in one step, at a molar scale, in the presence of a large excess of chlorotrimethylsilane. The transfer of the ethyl-2,2-difluoroacetate moiety to various electrophiles has been achieved.

Electrosynthèse en chimie organosilicique: silylation sélective de polychlorométhanes

Abstract Silylation by electroreduction of carbon tetrachloride, chloroform or methylene chloride is more selective than the common organometallic route. Me 3 SiCCl 3 (94%) and (Me 3 Si) 2 CCl 2 (68%) were thus obtained from CCl 4 , Me 3 SiCHCl 2 (94%) and (Me 3 Si) 2 CHCl (56%) from CHCl 3 and Me 3 SiCH 2 Cl (90%) from CH 2 Cl 2 . Complete silylation of polychloromethanes was also successful by electrosynthesis and gave satisfactory yields.

Magnesium bis(diisopropylamide), a useful reagent for regio- and stereoselective synthesis of kinetic silyl enol ethers

Abstract Less highly substituted silyl enol ethers are regiospecifically prepared in high yield, around room temperature under kinetic conditions, from unsymmetrical cyclic ketones and magnesium bis(diisopropylamide) [(DA) 2 Mg] in THF/heptane. This high regioselectivity is markedly higher than these reported for bromomagnesium diisopropylamide (DAMgBr); it is also similar to this of LDA/DME at −78°C, but (DA) 2 Mg can be used at room temperature. In addition, a high E-enolization stereoselectivity is observed for benzylic ketones, reverse of this obtained with LDA.

Selective electrochemical synthesis and reactivity of functional benzylic fluorosilylsynthons

Abstract Electrochemical reductive silylation of meta -(trifluoromethyl)arenes by the sacrificial anode technique selectively led to meta -trimethylsilyldifluoromethylarenes (ArCF 2 TMS), in the presence of an excess of TMSCl and in a THF/cosolvent mixture (cosolvent=DMPU or HMPA). In the case of meta -(trimethylsilyldifluoromethyl)trifluoromethylbenzene, the influence of the cosolvent on the silylation selectivity was studied. A cyclic voltammetry study allowed an explanation of the difference in the results obtained between the trifluoromethylbenzene and meta -bistrifluoromethylbenzene series. ArCF 2 TMS (Ar=Ph, m -CF 3 C 6 H 4 ) species were found efficient for ArCF 2 -group transfer to diverse electrophiles under Fuchigami’s conditions (KF catalysis in DMF).

Electrogenerated Base-Promoted Synthesis of Dithiocarbamate Acid Esters and 3-(N-Substituted-amino)-2-cyanodithiocrotonates from Primary or Secondary Amines and Carbon Disulfide

Electrogenerated cyanomethyl anion promotes the reaction between primary or secondary amines, carbon disulfide, and alkyl or benzyl halide. Secondary amines are converted to alkyl or benzyl dithiocarbamates, whereas primary amines give N-substituted alkyl or benzyl 3-amino-2-cyanodithiocrotonates. The mechanisms are discussed.

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.

Non-defluorinative electrochemical silylation of ethyl trifluoroacetate: a practical synthesis of trifluoroacetyltrimethylsilane via its ethyltrimethylsilyl ketal

Abstract An efficient method for the preparation of original trifluoroacetyltrimethylsilane, CF 3 COSiMe 3 ( 3 ), in two steps from readily available ethyl trifluoroacetate is described. Electrochemical reduction of this ester using a sacrificial anode and performed on a semimolar scale afforded the unprecedented corresponding ketal, CF 3 C(SiMe 3 )(OSiMe 3 )OEt ( 2 ) in 30–56% isolated yield. Treated with concentrated sulphuric acid at room temperature, the latter directly led to pure acylsilane 3 in 86% yield.