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Showing 1 to 20 of 44 for “"iminium"”.
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RECENT ADVANCES IN IMINIUM SALT CATALYSED ASYMMETRIC EPOXIDATION
… asymmetric epoxidation of alkenes using chiral iminium salt catalysts. The first chapter reviews past and present developments in; catalytic asymmetric epoxidation, and covers the application of this reaction towards the kinetic resolution of racemic olefins. Chapter two is separated into two …
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Stereochemistry of Ternary Iminium Salts and Aziridinium Salts
Made available in DSpace on 2014-12-09T17:35:58Z (GMT). No. of bitstreams: 1 6808277.pdf: 5621528 bytes, checksum: ea7fa0ad440e0d46f097e14a1982097d (MD5) Previous issue date: 1967
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Diastereoselective aza-cope rearrangement-mannich cyclizations of conformationally mobile iminium cations
… was formed. We believe that the requisite iminium cation for the ACM reaction is quite stable, causing an unusually high aza- Cope activation barrier and allowing for an undesired pathway to be favored. Destabilization of the iminium cation intermediate via an electron withdrawing group may …
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Development of Highly Reactive Sulfone Iminium Fluoride Reagents and Their Application in Fluorine Methodologies
… of this work, we report the synthesis of sulfone iminium fluorides (SIFs), a new and highly reactive sulfur (VI) fluoride reagent class. A small library of these compounds was synthesized in five simple, modular steps from cheap starting materials. The SIF reagents successfully convert alcohols …
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NEW GREEN TECHNOLOGIES FOR ORGANOCATALYTIC ASYMMETRIC EPOXIDATION APPLICATIONS IN SYNTHESIS
… on chromene substrates mediated by Page’s iminium salt catalysts. Organocatalytic asymmetric epoxidation is an efficient tool to access enantiomerically rich epoxides. This study is divided into three main parts which are discussed in each chapter. The first part of this research is the …
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The application of organocatalytic Asymmetric Epoxidation
… catalytic asymmetric epoxidation using iminium salts such as 1 has been successfully employed to access chiral chromenes within the Page group. Iminium-catalysed asymmetric epoxidation methodology has been applied to the synthesis of levcromakalim, 3 trans-khellactone, and lomatin,4 …
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Direct ⍺-C–H Functionalisation of Cyclic Alkylamines
… the design of a sequential process involving iminium ion formation followed by the 1,2-addition of carbon-based nucleophiles. Key to this strategy was the selective formation of endo-iminium ions from six-membered N-heterocycles, achieved via α-C–H elimination from the corresponding cyclic …
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A Modified Procedure for the Synthesis of Bis(phenylenedioxy)tetrathiafulvalene (BPDO-TTF): an Electron Donor for Charge Transfer Organic Complexes.
<p>Iminium salt dimethyliminium hexafluorophosphate <em><strong>(5)</strong></em>, a precursor of the target compound BPDO-TTF, was synthesized in five steps with significant modifications in the previously worked out scheme. 2,3-Dihydrobenzo-1, 4-dioxin<em><strong>(1)</strong></em> was synthesized …
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Mechanistic investigation of the interrupted Bischler-Napieralski reaction and its application to the total synthesis of the aspidosperma alkaloids
… and full characterization of a tetracyclic iminium trifluoromethanesulfonate provided additional correlation between in situ characterization of sensitive intermediates and isolable compounds involved in this synthetic transformation. II. Total Synthesis of (+)-Fendleridine, …
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Charge-Transfer Complexes for Amine Synthesis
… step, single-electron reduction of alkyliminium ions to α-amino radicals was achieved, using an aromatic thiol and visible light irradiation. Mechanistic and computational studies supported the formation of a transient, ion-pair charge-transfer complex between iminium and thiolate ions. …
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Diverse Applications of Flow Technology in Discovery Chemistry
… variant nature of these reactions, both a simple iminium ether and a densely functionalized iminium ether derived from a bicyclo[3.2.1]octanoid scaffold were explored. Multidimensional reaction screening on an automated microfluidic platform was employed to facilitate the simultaneous …
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Imidazolidinones in amine catalysis
Iminium ion activation is a rapidly expanding and contemporary area of synthetic chemistry in which a number of enantio- and diastereoselective transformations have been developed. Despite the substantial attributes of the area, high catalyst loadings, aldehyde substrate specificity and incomplete …
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Mechanism-Guided Studies of Brønsted Acid and Base Organocatalysis
… between the phosphoric acid catalysts and the iminium ions is essential in order to determine the likely extent of proton transfer, full or partial, between these two species in the course of the Mannich reaction. The determination of aqueous pKa values of iminium ions was attempted by …
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Computational predictions and reactivity analyses of organic reactions
… radical addition step, the iminium in the lowest energy SR transition state (TS) takes up the conformation of the lowest energy ground state iminium (EE). The conjugated iminium in the SS TS adopts an EZ conformation to avoid potential structural deformations due to radical …
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NH-Isoxazolidines as Organocatalysts
… isoxazolidines as potential organocatalysts in iminium ion and enamine catalysis. The first chapter gives an overview of state-of-the-art organocatalysis. Reactions are discussed in terms of the catalytic mechanism and a selection of reactions catalysed by each route is included. The second …
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A novel photocatalytic strategy for complex aliphatic amine synthesis and the total synthesis of alkaloids (−) FR901483 and (+)-TAN1251C
… reduction of in situ generated all-alkyl iminium ions. Under optimized reaction conditions, the photocatalytic olefin-hydroaminoalkylation procedure was shown to be compatible with a broad range of benzyl amine, aldehyde, and olefin substrates. A detailed study of the mechanism of the …
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Asymmetric Catalysis with Brønsted Acids: Experiments and Calculations
… to furnish nitrogen-based heterocycles via iminium ions as reactive intermediates. Two of the transformations presented in this work include imino-Diels-Alder and Pictet-Spengler reactions. Moreover, a S,O-thioacetalization reaction to furnish 1,3-oxathiolanes enantioselectively is …
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