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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 20 of 54 for “"Chemoselectivity"”.
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Enhancing chemoselectivity and predicting site-selectivity in manganese catalyzed C–H oxidation
… two main challenges have emerged: improving chemoselectivity and accurately predicting site of oxidation. The highly reactive carboxylate-oxo active oxidant in PDP catalysis enables strong C–H bond oxidation but remains incompatible with many functional groups. Moreover, increased molecular …
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Three-Way Chemoselectivity Switching through Coupled Equilibria in Complex System and Post-synthetic Modification of Cyclobenzoins
Everything around us is complex systems, including ant-hills, human economies, climate systems, nervous systems, and human beings. In order to understand complex systems often requires cross-disciplinary techniques that merge the knowledge from different fields such as mathematics, physics, …
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Development and investigation of novel chemoselective processes in Pd and Cu catalysis
… obstacle to complex molecule synthesis'. Chemoselectivity is required to exploit the full potential of synthetic developments in organic chemistry, allowing for more efficient procedures and better route design. This thesis will describe the development of chemoselective processes across …
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Mechanistic investigations into the origin of chemoselectivity a methylene (csp3) c-h oxidation in the presence of α-β unsaturated carbonyls and exploration of reaction scope
Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2027-05-01
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New horizons of aliphatic C—H amination and hydroxylation reactions with manganese catalysis
… inverse correlation between reactivity and chemoselectivity: catalysts that are highly reactive to strong aliphatic C—H bonds usually lacks chemoselectivity for -functionalities (aromatics and olefins). My doctoral research in the White group has focused on developing novel manganese …
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Manganese-catalyzed C-H oxidation applied to the synthesis of complex molecules
Chemoselectivity remains a significant challenge in the field of undirected Csp3-H oxidation. The powerful oxidants required to functionalize these strong bonds often react with any oxidizable functional groups present in a substrate, furnishing undesired side products. Although there are many …
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C(sp3)-H aminations under first row transition metal catalysis
… sites, is responsible for this lack of chemoselectivity. Conversely, first row transition metal catalysts like iron and manganese are thought to react through a stepwise homolytic C—H abstraction/rebound mechanism. We hypothesized that this different mechanism would lead to orthogonal …
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Dirhodium(II,II) paddlewheel complexes conjugated to a polypyridyl tris-amine scaffold: synthesis and application as asdjncaslpre-catalysts in the hydroformylation of 1-octene
… (>99.8%) of 1-octene, excellent activity and chemoselectivity toward aldehydes (>98%) with moderate regioselectivity towards linear products (40-44%). Excellent conversion (97-99%), moderate to good chemoselectivity toward aldehyde products (59-87%) and moderate to good regioselectivity …
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A base modulated synthesis of indoles and quinolines, an expedient synthesis of salviadione, and chemoselective couplings en route to indoles and pyrroloindoles
… Salviadione. A systematic investigation of chemoselectivity in Kosugi-Migita-Stille coupling reactions provided the basis for the synthesis of isomeric pyrroloindoles through palladium-catalyzed reductive double N-heteroannulation of dinitro-dialkenyl benzenes.
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Preparation of Novel Carbenes and their Catalytic Application to the Cross-Benzoin, Aza-Benzoin and Stetter Reactions
… a fused 6 membered ring were found to induce chemoselectivity in the cross-benzoin between aromatic and aliphatic aldehydes. Use of these catalysts gave rise to predominantly one cross-benzoin product which could be isolated in good to excellent yield (68-99%). Consistently high …
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Alkylated PTA platforms for mono- and polynuclear pre-catalysts for the aqueous biphasic hydroformylation of 1-octene
… as side products. All complexes exhibited good chemoselectivity for aldehydes with the COD complexes displaying better chemoselectivity towards aldehydes than the CO complexes. However, the CO complexes exhibited better regioselectivity for linear aldehydes than the COD complexes. The trinuclear …
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Development of Novel, Regioselective Borylation Protocols
… synthetic value because they are shown to have chemoselectivity in downstream cross-coupling reactions; chemoselectivity is made possible by to the significant difference in Lewis acidity of the pinacol and diaminonapthalene-protected boron centers. This method allows for facile synthesis of …
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Dendritic rhodium catalyst precursors for the hydroformylation of olefins
… good to excellent conversion (78 – 100%), good chemoselectivity (66 – 95%) and moderate regioselectivity (51 – 67%). In contrast, the N,P-iminophosphine metallodendrons displayed low conversion (4 – 8%), good chemoselectivity (76 – 80%) and good regioselectivity (64 – 68%) under the …
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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
… amination product is favoured in typically high chemoselectivity (>20:1) and high enantiomeric excess (>85% ee) for a range of carbon length substrates featuring pendant alcohol groups. This work displays a rare example of chiral cations controlling both enantioselectivity and chemoselectivity in …
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Selective Synthesis of Trans-fused Lactam-Lactones by Vicinal Difunctionalization of Readily Affordable Allylic Lactams
… is challenging from the standpoints of chemoselectivity, stereoselectivity, and regioselectivity. In this thesis, the highly-selective, cost-effective, and high-yielding conversion of readily affordable allylic lactams into <em>trans</em>-fused lactam-lactones by intramolecular vicinal …
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Novel metal- and main group-catalyzed methods for modulating molecular oxygenation
… bonds such that a radical catalyst with tunable chemoselectivity breaks this weakened bond. In the presence of an oxygen atmosphere, this leads to carbon-oxygen bond formation.
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Cesium Effect: A Mild and Efficient Synthesis of Secondary and Tertiary Phosphines
… gives rise to high efficiency and excellent chemoselectivity, was proved advantageous for these syntheses. The use of cesium hydroxide as the base of choice has many advantages over traditional methods for construction of the C-P bond. Important mechanistic concepts and synthetic applications …
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Chemical Methods for Cobalt-Catalysed C(sp3)–H Activation and Iodonium Salt-Mediated Peptide Functionalisation
… in dilute aqueous solutions, exhibiting high chemoselectivity with respect to peptide sidechains. Excellent conversions were achieved in five minutes at room temperature, demonstrating the potential of this process for bioorthogonal labelling.
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Monometallic and multimetallic complexes as precatalysts in the hydroformylation of olefins
… of 2500 : 1. These conditions gave good aldehyde chemoselectivity (90%), excellent conversion of the substrate (99%) and good catalytic activity (554 h-1 ). Comparable catalytic performance of both precatalysts was obtained when milder reaction conditions (85 ℃, 20 bar for 4 h) were adopted in the …
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