La réaction d'aldolisation est une des méthodes les plus importantes et plus utilisées pour former des liaisons C-C. La réaction tandem d'isomérisation-aldolisation catalytique d'alcools allyliques permet d'effectuer cette réaction avec de nombreux avantages synthétiques et nous avons préparé par ce moyen des beta-hydroxyacylsilanes à partir d'alpha-hydroxyallylsilanes. Tout d'abord, nous avons cherché à mettre au point une version catalytique asymétrique de cette réaction tandem et nous avons aussi synthétisé des beta-hydroxyacylsilanes par aldolisation directe. Ensuite, nous avons utilisé des alpha-hydroxyallylsilanes pour préparer des aldolsalpha-silylés au moyen de réactions d'époxydation. Dans une troisième partie, nous avons synthétisé des aldols à partir de beta-hydroxyacylsilanes protégés de manière simple et efficace, ce qui nous a permis d'effectuer des réactions d'aldolisation itératives. Nous avons illustré le potentiel de cette méthode par la synthèse d'un fragment de (±)-pironetine. Enfin, nous avons synthétisé, à partir des mêmes beta-hydroxyacylsilanes protégés, des éthers d'énol silylés qui ont été ensuite utilisés avec succès comme substrats pour des réactions de Mukaiyama. / The aldol reactions is one of the most important and commonly used methods to form C-C bonds. The catalytic tandem isomerization-aldol reaction of allylic alcohols allows to perform this reaction with many synthetic advantages. Thus, we have prepared by this method beta-hydroxyacylsilanes from alpha-hydroxyallylsilanes. First, we have attempted to develop a catalytic asymmetric version of this reaction, and also to synthesize beta-hydroxyacylsilanes by direct aldol reaction. Then, we used alpha-hydroxyallylsilanes to prepare alpha-silyl aldols trough epoxidation reactions. Next, we synthesized aldols from protected beta-hydroxyacylsilanes in a simple and efficient fashion which allowed us to perform iterative aldol reactions. We have illustrated the potential of this method by the synthesis of a fragment of (±)-pironetine. Finally, we have synthesized, from the same protected beta-hydroxyacylsilanes, silyl enol ethers that next have been used successfully as substrates for Mukaiyama aldol reactions.

Microwave-Assisted Thermolysis of ortho-Substituted Aroylsilanes Marc Tremblay Master of Science Department of Chemistry University of Toronto 2008 The microwave-assisted thermolysis of ortho-substituted aroylsilanes has been investigated. When irradiated at 250ºC in DMSO or o‑dichlorobenzene for 10 minutes, aroylsilanes form siloxycarbenes that react following different pathways depending on the solvent and the structure of the starting material. It is shown that in the case of substrates having an O‑allyl or an O‑propargyl chain ortho to the acylsilane, cycloaddition occurs followed by a cascade ring opening to give respectively chroman‑4-one and chromen‑4-one derivatives in up to 66% yield. Among the major competitive pathways were the insertion of the siloxycarbene into allylic C–H bonds and decomposition of the acylsilane group to the corresponding aldehyde, followed by Claisen rearrangement.

Microwave-Assisted Thermolysis of ortho-Substituted Aroylsilanes Marc Tremblay Master of Science Department of Chemistry University of Toronto 2008 The microwave-assisted thermolysis of ortho-substituted aroylsilanes has been investigated. When irradiated at 250ºC in DMSO or o‑dichlorobenzene for 10 minutes, aroylsilanes form siloxycarbenes that react following different pathways depending on the solvent and the structure of the starting material. It is shown that in the case of substrates having an O‑allyl or an O‑propargyl chain ortho to the acylsilane, cycloaddition occurs followed by a cascade ring opening to give respectively chroman‑4-one and chromen‑4-one derivatives in up to 66% yield. Among the major competitive pathways were the insertion of the siloxycarbene into allylic C–H bonds and decomposition of the acylsilane group to the corresponding aldehyde, followed by Claisen rearrangement.