Ph.D. - Chemistry

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https://hdl.handle.net/10125/1384

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    MOLECULAR DYNAMICS SIMULATIONS TOWARD ENHANCING MEMBRANE PERMEABILITY AND DYNAMICS
    (2024) Kang, Christopher Alan; Sun, Rui; Chemistry
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    ELUCIDATING MECHANISMS OF GAS-PHASE REACTIONS WITH DYNAMICS SIMULATIONS
    (2024) LUO, YUHENG; Sun, Rui; Chemistry
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    UNTANGLING THE FOLDING AND FUNCTION OF LEPTIN
    (2024) Simien, Jennifer Michelle; Haglund, Ellinor; Chemistry
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    Synthesis and Applications of Organobismuth(III) Complexes: Novel Materials and Catalysts
    (2024) Louis-Goff, Thomas Aiwei Finfgeld; Hyvl, Jakub; Chemistry
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    THE DESIGN AND SYNTHESIS OF NOVEL CHIRAL 2,2’-BIPYRIDINE LIGANDS
    (2023) Liu, Chaolun; Tius, Marcus A.; Chemistry
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    Probing Hydrogen Mesosorption by High Pressure Nuclear Magnetic Resonance Spectroscopy
    (University of Hawaii at Manoa, 2022) Nakamoto, Bryson Yoshio; Jensen, Craig M.; Chemistry
    Concerns related to fossil fuels as an energy source has driven studies to shift focus to renewable energy. Specifically, the development of hydrogen as an onboard energy carrier. Hydrogen possesses a large amount of energy and has the potential to be a viable renewable energy carrier. Chemisorption and physisorption are two types of material-based interactions researched for hydrogen storage. Physisorption interactions have low binding energies which results in fast kinetics and complete reversibility. However, low binding energies also require liquid nitrogen temperatures to hold the hydrogen to sorbents. Carbon materials have a binding energy of 4-7 kJ/mol to H2, however doped carbon material have shown to improve the binding energy of specific binding sites. Overall, the materials have a relatively low hydrogen storage capacity, but the high energy binding sites supplies valuable information about the possibilities of future dopants. Binding energies needed to facilitate near ambient conditions are found in a region between physisorption and chemisorption, known as mesosorption. Current techniques cannot reliably characterize mesosorption interactions as they are observed on specific high energy binding sites. The technique developed for the observation of strong binding sites utilizes 1H Nuclear Magnetic Resonance (NMR) spectroscopy to examine the change in free and bound hydrogen under high pressures and variable temperatures. Based on the temperature dependent equilibrium, the ΔHdes of a specific high energy binding site was calculated. Studies presented in this dissertation are based on this specialized NMR technique and are used to analyze boron-doped carbon and other materials to identify limitations. Employing high pressure NMR analysis in this manner has shown to be versatile and provides valuable thermodynamic data on compounds typically difficult to investigate.
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    Catalytic Asymmetric Nazarov Cyclizations & Methods for the Synthesis of Fluorenes and Advanced Geodesic Polyaromatic Hydrocarbons
    (University of Hawaii at Manoa, 2022) Dickinson, Cody Francis; Tius, Marcus A.; Chemistry
    PART I: CATALYTIC ASYMMETRIC NAZAROV CYCLIZATIONS The synthesis of all-carbon quaternary stereocenters remains a significant challenge in organic synthesis. Even more challenging is the synthesis of vicinal all-carbon quaternary stereocenters. While there are a small number of methodologies that have attempted to address both of these problems, there are very few reports on the catalytic asymmetric synthesis of the latter type. The Nazarov cyclization offers a unique opportunity to address this problem, in that the orbital symmetry-controlled process can be catalyzed in a number of different ways because of the diversity of the acyclic precursors. This thesis will describe a new catalytic asymmetric synthesis of compounds containing vicinal all-carbon quaternary stereocenters through a Nazarov cyclization. In the first chapter the Nazarov cyclization is introduced and briefly reviewed. A brief review on catalytic asymmetric variants of this reaction is given. In the second chapter an (R)-BINOL-derived N-triflyl phosphoramide-catalyzed Nazarov cyclization of geometrically pure dienones to α-hydroxycyclopentenones is described. This follow up work describes an expanded substrate scope to all-alkyl C1,C2-tetrasubstituted cyclopentenones containing vicinal quaternary centers and to C1,C5-trisubstituted cyclopentenones containing vicinal quaternary and tertiary centers. The mode of asymmetric induction is discussed.In the third chapter a novel Lewis acid-Brønsted base-catalyzed cyclization of α-diketoesters to α-hydroxycyclopentenones is described. The chiral-at-rhodium catalyst for this metal enolate Nazarov cyclization is unique and demonstrates high catalytic activity and enantioselectivity. The substrate scope of all-aliphatic α-hydroxycyclopentenones bearing either vicinal quaternary or vicinal quaternary and tertiary stereocenters is described. PART II: METHODS FOR THE SYNTHESIS OF FLUORENES AND ADVANCED GEODESIC POLYAROMATIC HYDROCARBONS Polyaromatic hydrocarbons (PAH) have a long and rich history in organic synthesis. At the forefront today is the synthesis of highly strained geodesic compounds, for example, buckminsterfullerene, C60 (buckyball). Interest in non-planar PAHs has grown because of their unique UV-vis, electronic, and structural properties. The use of these compounds in asymmetric catalysis has not been described to date, possibly because their synthesis is impractical on scale. As such, our group has an interest in developing new methodologies to address these shortcomings. We have focused on the fluorene motif as an initial starting point in the synthesis of more advanced PAHs, since many others have identified it in geodesic hydrocarbons. In the first chapter a new methodology for the preparation of fluorenes and dibenzo[g,p]chrysenes through an oxidative cascade process using copper(II) bromide is described. A novel dibenzo[g,p]chrysene containing an ether linkage is reported. In the second chapter a synthesis of a geodesic, C30 semibuckminsterfullerene “buckybowl” is described. The synthetic route used to access this compound is versatile and modular. The scalable and simple synthesis of a strategic precursor 1,8-difluoro-9H-fluorene is also described.