Stereoselective Electrophilic Additions to Alpha-Trialkylsilyl-Beta,Gamma-Unsaturated Esters

dc.contributorSnowden, Timothy
dc.contributorShaughnessy, Kevin
dc.contributorWoski, Stephen
dc.contributorRossi, Lauren
dc.contributor.advisorBonizzoni, Marco
dc.contributor.advisorJennings, Michael P.
dc.contributor.authorFealy, Lisa M.
dc.contributor.otherUniversity of Alabama Tuscaloosa
dc.descriptionElectronic Thesis or Dissertationen_US
dc.description.abstractThis dissertation details stereoselective additions to alpha-trialkylsilyl beta, gamma-unsaturated esters synthesized from alpha-trialkylsilyl alpha, beta-unsaturated esters. This work is divided into five chapters. Chapter 1 utilizes organometallic methodology and begins by discussing background of the Suzuki-Miyaura cross-coupling reaction. It goes on to outline our efforts toward palladium-catalyzed cross coupling of alpha-bromoketones via their palladium enolates. The goal of this chapter was to develop a dependable method to prepare gamma-substituted alpha, beta-unsaturated esters through a Suzuki-Miyaura cross-coupling using substituted boronic acids as a precursor to gamma-halogenated alpha, beta-unsaturated esters discussed in Chapter 3. Chapter 2 details an approach to simultaneous installation of these three functional groups mediated by alpha-silyl alpha, beta-unsaturated esters, starting from ethyl prop-2-ynoate (ethyl propiolate). Initial synthetic steps include a catalytic carbocupration with copper iodide, various Grignard reagents, and trialkylsilyl triflate to yield alpha-silyl alpha,beta-unsaturated esters with (E)-selectivity (>20:1) of the newly formed olefin. Deprotonation of the alpha-trialkylsilyl alpha, beta-unsaturated ester at its gamma-position, followed by kinetic reprotonation of this species, yielded the deconjugated alpha-trialkylsilyl beta,gamma-unsaturated ester, retaining good selectivity for the (E)-alkenes (>20:1). Chapter 3 discusses the halogenation of the various previously obtained alpha-trialkylsilyl beta, gamma-unsaturated ester with halo-succinimides (NXS, X = Cl, Br, and I). These reactions retain excellent diastereoselectivity (>20:1) when carried out on the series of deconjugated alpha-trialkylsilyl beta, gamma-unsaturated esters prepared previously, providing a straightforward approach to preparing gamma-halo-(E)-alpha,beta-unsaturated esters.Chapter 4 further expands the usefulness of these ester intermediates by showing that they can be converted into beta, gamma -epoxy esters, with good selectivity for the formation of the epoxide ring anti to the previously installed α-trialkylsilyl substituent (dr ~6:1). We also demonstrate that these intermediates can be further converted into valuable γ-hydroxy compounds with excellent regioselectivity and good stereoselectivity. The alcohol products are obtained through epoxide ring opening and desilylation, to produce a gamma-hydroxy alpha, beta-unsaturated ester as the (E)-olefin (>20:1). Chapter 5 outlines future directions for the research outlined, as well as, natural products that could be synthesized utilizing the methods outlined in this dissertation.en_US
dc.publisherUniversity of Alabama Libraries
dc.relation.hasversionborn digital
dc.relation.ispartofThe University of Alabama Electronic Theses and Dissertations
dc.relation.ispartofThe University of Alabama Libraries Digital Collections
dc.rightsAll rights reserved by the author unless otherwise indicated.en_US
dc.titleStereoselective Electrophilic Additions to Alpha-Trialkylsilyl-Beta,Gamma-Unsaturated Estersen_US
dc.typetext of Alabama. Department of Chemistry and Biochemistry University of Alabama
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