F. Pisciotti

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.

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 par des chlorosilanes de polyènes conjugués obtention de dérivés monosiliciés y-éthyléniques par scission Si-C

Summary In the presence of magnesium and in hexamethylphosphoric triamide (HMPT), trimethylchlorosilane reacts with 2,6-dimethyl-2,4,6-octatriene to lead only to one disilylated derivative with 1,4-addition of trimethylsilyl groups. Silylation of dienes has been especially worked out with butadiene and carried out with isoprene: particularly with dimethyldichlorosilane, the corresponding silacyclopentenes have been synthetized with satisfactory yields. The disilylated compounds prepared all undergo acid cleavage of one allylic Si-C bond, with allylic rearrangement. These reactions can be explained both by steric and electronic reasons.

Addition d'hydrocarbures silicies possedant une liaison SiC activee a des composes carbonyles α-chlores

Abstract In the presence of a Lewis acid catalyst, silylated hydrocarbons having an activated SiC bond (allyl- ethynyl-, phenylsilanes, etc.) add to chloral or chloracetone; this reaction type is original in these series.

Acetylation de dimethyl-1,1 silacyclopentenes-3. Synthese de cetones ethyleniques β-siliciees

Abstract Acetylation of substituted or unsubstituted 1,1-dimethylsilacyclopent-3-enes by means of CH 3 COClAlCl 3 and (CH 3 CO) 2 OBF 3 occurs with ring opening and leads to two types of β-silylated ethylenic ketones: siloxanic ketones in the case of CH 3 COClAlCl 3 , and β-fluorosilylketones with (CH 3 CO) 2 OBF 3 . According to the substitution degree of the double bond of the starting silacyclopentenes, acetylation gives conjugated or unconjugated ketones, the latter resulting from the isomerization of the former ones. An interpretation of these results is proposed.