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Showing 1 to 20 of 30 for “"Cinchona"”.
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Derivatisierungsreaktionen von Cinchona-Alkaloiden und eine Cinchona-Alkaloid-katalysierte asymmetrische Synthese von 2,5-Diarylphopholanen
… deals with the synthesis of structurally diverse cinchona alkaloid derivatives via nucleophilic addition of organometallic reagents. An addition of organolithium reagents leads to 2´-alkylated products. The reaction with Grignard reagents leads to new 4´-substituted cinchona alkaloid derived …
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Synthesis of cinchona alkaloid analogues as mechanistic probes of the osmium-catalyzed asymmetric dihydroxylation of olefins
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 1991.
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ASYMMETRIC ORGANOCATALYTIC HENRY REACTION OF β–SUBSTITUTED α-KETO ESTERS VIA DYNAMIC KINETIC RESOLUTION
… reaction of ß-substituted a-keto esters using cinchona alkaloid derived bifunctional catalyst via dynamic kinetic resolution. Chapter 1 presents a brief historical background and development of asymmetric catalysis. Particularly, the asymmetric organocatalysis is introduced in detail. Then the …
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Harnessing cheminformatics for catalyst design I. Investigation into a general, asymmetric synthesis of cinchona alkaloid analogs towards asymmetric phase transfer II. Development of an enantioselective brønsted acid catalyzed four-component Ugi reaction
… ‘core’ catalyst scaffolds were chosen. First, Cinchona alkaloids were studied against an asymmetric phase transfer catalyzed cyclopropanation reaction. Second, (R)-BINOL derived phosphoric acids were studied in regards to the brønsted acid catalyzed Ugi reaction. In regards to Cinchona …
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Design, synthesis and evaluation of organocatalysts in 1,4-conjugate additions to nitroolefins and alkylidene malonates
A family of cinchona-based and thiourea pyrrolidine-based organocatalysts were synthesised and fully characterised. Their catalytic activity and selectivity in 1,4-conjugate additions involving the Michael acceptor, nitrostyrene, was evaluated. Thiourea catalysts based upon the cinchona alkaloid …
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The Design and Application of Ion-paired Ligands to Address Selectivity Challenges in Transition Metal Catalysed Oxygen and Nitrogen Transfer Reactions
… to chiral cations based on readily available cinchona alkaloids and have been shown to induce enantioselectivity in challenging reaction types: iridium- catalysed C-H borylation, and rhodium-catalysed C-H amination and alkene aziridination. Chapter 2 explores the synthesis of novel ion-paired …
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Organocatalytic asymmetric mannich-type reactions: an easy approach to optically active amine derivatives
… protocols for Mannich-type reactions mediated by Cinchona alkaloids derivatives (Scheme I, left); the second topic, instead, regards the study of a new approach towards the enantioselective total synthesis of Aspirochlorine, a potent gliotoxin that recent studies indicate as a highly selective and …
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Utilising Non-Covalent Interactions in Developing Enantioselective Radical Transformations
… ion-paired to a chiral cation derived from cinchona alkaloids, to create a chiral environment around the metal centre. The challenges encountered for both approaches are discussed. The third research chapter describes the incipient phase of a project based on the use of cinchona …
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The preparation and characterization of diastereomeric (+)-quinicinol
… (I) (see Fig. 1) (obtained from the bark of the Cinchona tree) is still listed among the most effective (1, 3, 4). Consequently, there has been much study done on isomers and derivatives of quinine, where the vinyl group on C-3, various substituents or, and the stereochemistry of, C-9, and C-8 to …
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Synthesis of Resveratrol and Its Analogs, Phase-Transfer Catalyzed Asymmetric Glycolate Aldol Reaction, and Total Synthesis of 8,9-Methylamido-Geldanamycin
… 17 μM) relative to resveratrol (24 μM). Cinchona phase-transfer catalysts (PTC) were developed for glycolate aldol reactions to give differentially protected 1,2-diol products. Silyl enol ether of diphenylmethoxy-2,5-dimethoxyacetophenone reacted to generate benzhydryl-protected products. …
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Chemical diversification of the natural products quinine, abietic acid and pleuromutilin by ring distortion
… application of ring distortion reactions to the cinchona alkaloid natural product quinine towards the creation of a collection of complex and diverse small molecules. Chapter 3 details the ring distortion of the terpene natural product abietic acid and details strategies for the synthesis of …
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The Application and Evolution of Chiral Ion-Paired Rhodium(II,II) Tetracarboxylate Catalysts for Enantioselective Nitrene Transfer
… combination of transition metal complexes and cinchona alkaloid-derived chiral cations. In the first section of research, an enantioselective aziridination of alkenyl alcohols using these catalysts is presented, which was conducted in collaboration with Dr. Alexander Fanourakis and Arthur R. …
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The development of novel hetrogeneous catalysts for the hydrogenation of prochiral imines
… investigated. As the methyl pyruvate system of cinchona modified catalysts was to be used, this system was first investigated with a series of platinum catalysts. Although these results provided some interesting results they maintained that the 5% Pt/alumina catalyst was the best for this …
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Asymmetric anhydride opening : optimization and applications
… of easily accessible meso-anhydrides by cinchona alkaloid-mediated opening with benzyl alcohol. This procedure was found to be applicable to a variety of structurally different substrates and leads to the corresponding optically active hemiesters with enantioselectivities of up to 99%. A …
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Insights into the mechanism of action of quinoline antimalarials against Plasmodium falciparum revealed by novel fluorescent analogues and chemical proteomics
… methanols, represented by the diastereomeric Cinchona alkaloids quinine and quinidine, and the 4-aminoquinolines, represented by chloroquine. Mechanistic studies of these antimalarials have typically focused on the inhibition of haemozoin biocrystallisation within the acidic digestive vacuole …
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The Kinetic Resolution of Secondary Alcohols Through A Tandem Enantioselective Silylation and the Synthesis of Bis(Oxazolidinyl)Pyridine Metal-Organic Complexes
… anion paired with a chiral quaternary ammonium cinchona alkaloid, is discussed. We found that when the addition of a silyl ketene acetyl to benzaldehyde is catalyzed with our bi-functional catalyst, the reaction proceeds through a two step tandem process. The first step involves racemic …
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New Catalysts for Asymmetric Nitrene Transfer Based on Ion-Pairing Between Sulfonated Rhodium(II,II) Tetracarboxylates and Chiral Cations: Design, Synthesis and Applications to Enantioselective Carbon-Nitrogen Bond Formation
… with two chiral cations based on quaternised cinchona alkaloids. The modular catalyst design is used to construct a large library with the aim of exerting catalyst-control over selectivity in the ensuing nitrene-transfer reactions. In the second part, proof of concept using these dimers is …
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Investigations of Catalysts Which Utilise Non-Covalent Interactions to Control Enantioselectivity in Rhodium-Catalysed Amination of C(sp3)–H Bonds
… rhodium(II) dimers ion-paired with N-quaternised Cinchona alkaloids are described herein. Design and initial synthesis of these novel catalysts was performed prior by Dr. Alex Fanourakis, and their application towards substrate-directed amination of aryl alcohols via a key alcohol-sulfonate …
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