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Showing 1 to 20 of 34 for “"cyclopropanation"”.
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Catalytic, Enantioselective Cyclopropanation of Allylic Alcohols
In mechanistic investigations, spectroscopic examinations and reaction surveys of substrate, reagent, and promoter were combined with solid-state evidence concerning the active form of the catalytically operative species to rationalize many of the observed features and trends of this system. …
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Anion Relay Cyclopropanation and Aryl Vinyl Cyclopropane Cope Rearrangements
… followed by an overview of a novel anion relay cyclopropanation accomplished through a retro-Claisen activation of a nascent allylic alcohol following an initial Tsuji-Trost allylation between a carbon nucleophile and a vinyl epoxide. This reaction constitutes the latest example of retro-Claisen …
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Investigations into cyclopropanation and ethylene polymerization via salicylaldiminato copper (II) complexes
… diastereoselective homogeneous copper catalyzed cyclopropanation reactions. Cyclopropanation of styrene and ethyl diazoacetate (EDA) is a standard test reaction for homogeneous catalysts. Sterically bulky salicylaldimine (SAL) ligands should select for the ethyl …
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Rhodium(II)-Stabilized Vinylcarbenes: Synthetic Applications in Ylide, Cyclopropanation, and C-H Insertion Reactions
… as metal vinylcarbene precursors in asymmetric cyclopropanation and intermolecular C-H insertion reactions. The vinyldiazolactone derived from 5,6-dihydro-2H-pyran-2-one provided good enantioselectivities (>80% ee) in an intermolecular C-H insertion reaction with 1,4-cyclohexadiene and …
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Asymmetric cyclopropanation via catalysts incorporating the 1,4-diol ligands and the newly designed dioxaborolane /
… Their application in Simmons-Smith type cyclopropanation is investigated, and the pleasing results suggest that they are the potential catalytic enantioselective candidates to build C-C bonds.
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Studies in Asymmetric Catalysis. Part I. Lewis Base-Catalyzed Aldol Additions. Part II. Bis(oxazoline)palladium(ii)-Catalyzed Cyclopropanation
… complexes were prepared and tested in the cyclopropanation of ethyl (E)-cinnamate with diazomethane. Although an enantioselective process was never realized, effects of substitution on the ligand, catalyst loading studies, and other investigations led to a mechanistic proposal wherein …
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Part I. Development of an enantioselective cyclopropanation reagent. Part II. Studies on the addition of organometallic reagents to imine derivatives
Efforts to develop an enantioselective zinc-based cyclopropanation reagent are described. Enantioselectivities of up to 24% e.e. were achieved using N-methylephedrine as a chiral controller ligand for iodomethylzinc cyclopropanations of cinnamyl alcohol. Chiral bis-ether complexes of …
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Part 1: Lanthanum(III) Triflate-Catalyzed Cyclopropanation via Intramolecular Methylene Transfer. Part 2: Reaction Design with Aromatic Ions - Nucleophilic Acyl Substitution and Organophotoredox Catalysts
… methods in the areas of methylene transfer cyclopropanation and reaction design with aromatic cations. The first chapter presents a new cyclopropanation method involving intramolecular methylene transfer from an epoxide to an olefin. The lanthanum(III) triflate-catalyzed process proceeds …
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An Investigation of Gold(I) Catalyzed Cycloaddition Reactions
… [3C+2C] cycloaddition reactions to exclusive cyclopropanation depending on the structure of the vinyl ether. Some cyclopropanation products rearrange into the corresponding [3C+2C] cycloaddition products after treatment with fresh Au(I) complex at 80°C. Vinylcyclopropanes formed from …
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Enantioselective synthesis and reactivity of bicyclobutanes: strained molecular platforms for 4-, 5-, and 6-membered ring synthesis and rhodium(II)-catalyzed reactions of diazoesters with organozinc reagents
… Rhodium(II)-catalyzed intermolecular cyclopropanation of diazoesters and alkenes has been widely studied and applied to complex synthesis; however, reports of intramolecular cyclopropanation had been quite limited. In Chapter 2, I will discuss the development of general conditions for …
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Catalyst and substrate effects in enantioselective C–H insertion reactions of α-diazosulfones
… pathways explored were C–H insertion and cyclopropanation, with hydride transfer competing in certain instances. Significantly, up to 98% ee has been achieved in the C–H insertion processes using copper-NaBARF-bisoxazoline catalysts, with the presence of the additive NaBARF critical to the …
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The generation and reactivity of functionalised organozinc carbenoids for cyclopropane synthesis
… by my predecessor for the development of the cyclopropanation reaction using an “amidoorganozinc” carbenoid derived from N,N diethoxymethyloxazolidinones derivatives in the presence of a source of zinc and chlorotrimethylsilane. Thus, the chemoselectivity and stereoselectivtity of the reaction …
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The chemistry of 1,2-dioxines.
… These cis-γ-hydroxyenone intermediates undergo cyclopropanation when allowed to react with stabilised phosphorus ylides. The synthesis of some l,2-dioxines is presented. This is followed by an investigation into the cobalt catalysed rearrangement of unsymmetrical 1,2-dioxines to …
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[4+1] cyclopentene annulation in the total synthesis of pentalenene type sesquiterpenes
… conversion to diazoketone 148, intramolecular cyclopropanation of this substance to vinylcyclopropane 163 and the vinylcyclopropane-cyclo pentene rearrangement of several derivatives of 195 to triquinanes 147, 146, 197, and 204. A detailed study of temperature, conformation, and electronic …
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Mechanistic studies of diastereoselective cyclopropanations of homochiral ene-ketals and synthesis and resolution of diastereomeric alpha-hydroxycycloalkanone ketals.
… were prepared and subjected to the Simmons-Smith cyclopropanation. A mechanistic model was formulated to explain the observed diastereoselectivity seen for the common ring systems. Diastereoselectivity is thought to result from preferential chelation of the Simmons-Smith reagent at the least …
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I Progress towards the synthesis of plakortether B through a zinc-mediated homologation II Synthesis of novel hydroxy-cyclopropyl peptides isosteres
… proposed to involve a cascade of homologation-cyclopropanation-rearrangement-lactonization reactions. Amino acid-derived beta-keto imides were synthesized in order to enhance the stereocontrol of the tandem lactonization reaction. The use of amino acid derived beta-keto imides was beneficial in …
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Development of Palladium-Catalyzed and Iodine-Mediated Formal [4+1] Annulation Protocols. Progress toward a New Fulvene-Based Organocatalytic Platform for Carbonyl α-Functionalization
… palladium-catalyzed intramolecular vinylcyclopropanation of dienyl beta-ketoesters followed by a magnesium iodide-mediated vinylcyclopropane-cyclopentene rearrangement. The cyclopropanation makes use of magnesium perchlorate to increase reactivity at the alpha-carbon of the …
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Synthesis and rearrangements of vinylcyclopropanes in a [2+3] cyclopentene and oxycyclopentene annulation methodology approach to (-)- specionin
… The key steps in this synthesis involved the cyclopropanation of optically pure enone 147 with Iithium dienolate 155 to give vinylcyclopropanes 169-exo/endo and the rearrangement of 169 to the oxygenated cyclopentanoid 187-exo which possesses the correct stereochemistry for further elaboration …
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Materials with supramolecular chirality : liqid crystals and polymers for catalysis
… ligands for use as catalysts in asymmetric cyclopropanation. Preliminary results indicate that the heterogeneous system gives higher enantioselectivities than the analogous homogeneous system.
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Applications of C₂-symmetric bis(azaferrocenes) in asymmetric copper-catalyzed reactions
… as ligands in the asymmetric copper-catalyzed cyclopropanation of olefins. We discovered that one of these ligands is particularly effective, and using a hindered diazo ester, an array of monosubstituted olefins has been cyclopropanated with excellent diastereo- as welf as enantioselectivity. …
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