Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 18 of 18 for “"iminium ion"”.
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NH-Isoxazolidines as Organocatalysts
This thesis describes the preparation and use of a range of N-unsubstituted bicyclic 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 …
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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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Studies in Synthesis and Organocatalysis: (i) The Design and Synthesis of Novel Electron Deficient Dienes and their Application in the First Enamine Activated Organocatalytic 1,6-Conjugate Addition. (ii) The Development of a New Organocatalytic Methodology through the Combination of DNA-Based Catalysis and Organocatalysis
… activated organocatalytic 1,6- conjugate addition was performed on the sulfonyl acceptors, using aldehydic enamines, giving excellent yields and selectivities (up to 98% yield, uniformly 99% ee). The mechanism of this reaction was explored in detail. The products of these additions were fully …
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Direct ⍺-C–H Functionalisation of Cyclic Alkylamines
… Consequently, methods for the selective functionalisation of these scaffolds would greatly facilitate the optimisation of biological activity, physicochemical properties and the systematic evaluation of structure-activity relationships. This thesis describes efforts towards the development of a …
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Asymmetric Synthesis of 1,3-Amino Alcohols and Tropinone Derivatives From Enantiopure Sulfinimines
… as precursors for acid-catalyzed cascade cyclizations. Chiral N-sulfinyl b-amino ketones derived from N-sulfinyl b-amino Weinreb amides, serve as novel and direct precursors to syn and anti N-sulfinyl 1,3-amino alcohols through stereoselective reductions. General reduction conditions have been …
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Development of selective high-affinity fluorescent sensors for imaging neurotransmitters and application in cells and tissue
… data (UV/Vis and fluorescence) and their applications in cells and tissue. NeuroSensor 510 (NS510) was designed and synthesized as a selective sensor for imaging norepinephrine. Formation of both an iminium ion and a boronate ester gave high affinity upon binding NS510 to norepinephrine. The …
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Total synthesis of ent-plagiochianin B and development of a metathesis approach to aleutianamine.
… found in (+)-3-carene led to production of material that was enantiomeric to the natural product. Key features of the synthesis include the utilization of a 6p-azatriene electrocyclization and the subsequent discovery of a palladium catalyzed oxidative cleavage of a terminal olefin. …
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Structural and mechanistic studies on eukaryotic UDP-galactopyranose mutases
… enzymes. Herein we present the detailed functional analysis of UGMs from A. fumigatus, T. cruzi, and L. major. The mechamism and structure these eukaryotic UGMs were examined by steady-state kinetics, rapid-reaction kinetics, trapping of reaction intermediates, fluorescence anisotropy, and …
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Radical methods for the synthesis of aliphatic amines
… is a ubiquitous and uniquely important functional group in pharmaceutical agents and the development of ever more efficient synthetic methods for their synthesis is a continuous challenge. This thesis details the development of three new radical reactions for the synthesis of aliphatic …
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Asymmetric Catalysis with Brønsted Acids: Experiments and Calculations
… having alternative groups at the 3,3’- positions, different from the widely common aryl scaffolds. These motifs include heavily hindered silyl groups and aryl sulfones. Such catalysts were used to design enantioselective ring-closing reactions to furnish nitrogen-based heterocycles via …
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Mechanistic investigation of the interrupted Bischler-Napieralski reaction and its application to the total synthesis of the aspidosperma alkaloids
I. Direct Observation of Intermediates Involved in the Interruption of the Bischler- Napieralski Reaction. The first mechanistic investigation of electrophilic amide activation of [alpha], [alpha]-disubstituted tertiary lactams and the direct observation of key intermediates by in situ FTIR, 1H, …
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Borenium Cations as Catalysts for the Reduction of Organic Molecules and Mechanistic Investigations into their Mode of Operation
The generation and isolation of two novel borenium cations has been described. The observation that the reaction of the Lewis acid B(C6F5)3 and the Lewis base diazabicyclo[2.2.2]octane (DABCO) with pinacol borane (HBpin) resulted in the activation of the B–H bond of HBpin and formation of a stable …
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Mechanistic Study of The Small Molecule Inhibitor DX-52-1
<p>Cell migration is a basic biological process that is fundamental to several normal and disease processes such as embryonic development, tissue repair, immune function, angiogenesis and cancer cell invasion and metastasis. Small organic molecules inhibiting cell migration can be used as both …
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Advances in Heterocyclic Synthesis through Ring Expansions and Flow Chemistry
This dissertation comprises three chapters, which focus on the development of new synthetic methodologies and the construction of a screening collection. An Application of the Schmidt Reaction: Construction of an Azasteroid Library. Ring expansion chemistry is a powerful way of introducing a …
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Development and application of new strategies for synthesis of complex diketopiperazine alkaloids
… of Bis(pyridine)silver (I) Permanganate Oxidation of Hydantoin Derivatives: Guidelines for Predicting the Site of Oxidation in Complex Substrates The bis(pyridine)silver(I) permanganate promoted hydroxylation of diketopiperazines has served as a pivotal transformation in the synthesis of …
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An excursion into the synthesis of novel flavanones
… approach was via an asymmetric aldol reaction catalysed by a chiral organocatalyst followed by an intramolecular Mitsunobu reaction. Following a review of the existing methodologies for the synthesis of racemic and asymmetric flavanones and various flavan analogues, an initial model …
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Mechanism-Guided Studies of Brønsted Acid and Base Organocatalysis
We have studied the mechanism of the reaction of N-Boc imines and acetylacetone in the presence and absence of chiral phosphoric acid catalysts. In order to gain mechanistic insight into the asymmetric Mannich reaction, a structurally homologous series of N-Boc imines and BINOL-derived phosphoric …
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The Use of High-Throughput Experimentation to Accelerate the Development of Methods for Complex Amine Synthesis
Technological innovations are crucial to advancing the chemical communities’ ability to develop new synthetic methodologies. To continue developing new reactions for the construction of important but increasingly complex molecules, modern chemists need to create faster and more environmentally …