Raymond Calas

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.

Addition d'hydrocarbures silicies possedant une liaison SiC activee a des composes carbonyles : I. Additions au chloral

Abstract In the presence of a Lewis acid catalyst, silylated hydrocarbonds having an activated SiC bond (allyl-, aryl-, vinyl-, ethynyl- or propargyl-silanes) add to chloral and give after hydrolysis the corresponding α-trichloromethylated carbinols; this type of reaction is original in this series. Likewise allyltrimethylsilane adds to chloroacetone.

Synthese nouvelle d'allylcetones par voie organosilicique

Abstract In the presence of a Lewis acid (AlCl3, InCl3, GaCl3), acyl chlorides react with allyltrimethylsilane to give the corresponding allyl ketones, CH2CHCH2COR, in good yields. Substituted allylsilanes, synthesized by 1,4-disilylation of conjugated dienes, give a similar reaction. The electrophilic substitution of SiMe3 by a COR group occurs with allylic rearrangement and therefore silylated β,γ-ethylenic ketones, , are obtained. In most cases the allylic ketones prepared isomerize easily to the corresponding conjugated ketones; ketones having the formula CH2CHCH2COR lead uniquely to the trans-,propenylketones, MeCHCHCOR.

Silylation d'hydrocarbures mono-aromatiques mono- ou disubstitues

Abstract In the presence of lithium and in tetrahydrofuran as solvent, trimethylchlorosilane reacts at 0–10°C, in an inert atmosphere, with monoaromatic mono- or disubstituted hydrocarbons, to give the corresponding 1,4-disilyl derivatives. In the case of ortho -xylene and cumene, disilylation is accompanied by tetrasilylation, whereas phenyltrimethylsilane can lead to the tetrasilylated derivative in quantitative yields. 1,3-Dichlorotetramethyldisiloxane reacts with benzene to give: Most of the products described are new compounds.

Application du systeme Me3SiClLiTHF a la synthese d'acylsilanes, d'alcools, d'aldehydes, d'esters et de nitriles C-silicies

Abstract Synthesis of C -silylated products by silylation of various functional saturated derivatives (aldehydes, nitriles, acid anhydrides and esters), by mens of the Me 3 SiClLiTHF system used at 0–10°C, is described. Most of the products obtained are new. A mechanism explaining the formation of these derivatives is proposed.

Nouvelle méthode de création de la liaison silicium-carbone à partir de chlorosilanes VII. C-silylation d'esters

Abstract The trimethylchlorosilane/magnesium/hexamethylphosphoric triamide system reacts with methyl benzoate to lead to an O - and C -silylated mixed ketal, which under hydrolysis easily gives benzoyltrimethylsilane (new preparative method of this compound), but which in basic media is converted to an unexpected siloxanic isomer. Under the same conditions trimethylsilyl benzoate gives, after hydrolysis, an α- C -disilylated alcohol.

C-silylation et duplication réductrice observées lors de l'action de Me3SiClMgHMPT sur des composés carbonylés α-éthyléniques. : Application à la préparation d'εdicétones à partir de cétones α-éthyléniques

Abstract Two reactions, the 1,4-disilylation and the reductive duplication accompanied by O -silylation, can chiefly occur by action of the Me 3 SiClMgHMPT system on various α-ethylenic carbonylated compounds. When the sequence of such derivatives is conjugated with another group , the 1,4-disilylation is the main reaction and affords upon hydrolysis the corresponding derivative β-silylated with respect to the carbonyl group (new illustrative example: the pseudo-ionone). In contrast to this, when the sequence is not conjugated with another group, the reductive duplication accompanied by O -silylation occurs and leads, after hydrolysis, to the corresponding e-diketone (examples: methylbutenone, 2-cyclohexenone and isophorone). Such a reaction can be used in organic synthesis to prepare e-diketones from α-ethylenic ketones. A mechanism permitting homogeneous interpretation of all our results in this domain is proposed.

Nouvelle voie d'acces aux cetones α-alleniques

Resume Propargyltrimethylsilane and 1,3-bis(trimethylsilyl)propyne react with acyl halides to afford α-allenic ketones. In the case of 1,3-bis(trimethylsilyl)-3-methyl-1-butyne a 1,3-dienic ketone is obtained by a process which involves first a SiC propargylic bond cleavage under acidic conditions.

Silylation de derives gem-polychlores

Abstract In contrast to the already-known routes which require very low temperature conditions (in the region of −100°), the direct partial silylation of gem -polychlorinated compounds occurs at 30–60° with the organochlorosilane/Mg/HMPT system. This type of reaction permits an easy synthesis of α-chlorinated silylated derivatives which lead to the corresponding α-functional silylated compounds: thus, PhCOSiMe 3 can be easily prepared from PhCCl 3 . The complete silylation of gem -polychlorinated compounds occurs in good yields with the Me 3 SiCl/Mg/HMPT system even when the other direct methods are not satisfactory. Without completely rejecting the formation of a silylated Grignard intermediate of radical character, the authors propose a mechanism for these reactions consisting of attack on the bond by Mg, followed by silylation.

Poly(trimethylsilyl)benzenes: Synthese, sulfonation

Abstract The system Me 3 SiCl/Mg/hexamethylphosphorotriamide (HMPT) reacts with some di- or poly-chlorobenzenes leading directly to the corresponding di- or poly-trimethylsilyl derivatives (yields 70-85%). Reaction of trimethylsilyl chlorosulfonate with these compounds gives in a first step trimethylsilyl arylsulfonic esters, Ph(SiMe 3 )SO 3 SiMe 3 . An excess of sulfonating reagent leads to sulfonation either at the PhSi bond (SiMe 3 group in meta or para position) or, mainly, at the MeSi bond (SiMe 3 group in ortho position). By this process new silylated sulfonic compounds can be synthesized.