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Item Exploitation of Biomass for Applications in Sustainable Materials Science(North Dakota State University, 2019) Serum, Eric MichaelBiorefinery may be defined as the process of accessing chemical commodities from living systems; consequently, biomass becomes the antecedent for renewable resources through biorefinery. Advantages to this process over petroleum refinery include: (1) increased potential for sustainable products, (2) increased diversity in chemical structure including heterocycles, and (3) potential for regional resource independence. Despite these clear advantages, adoption of biorefined commodities can be limited by the risk associated with small initial application portfolios and concomitant uncertainties. The strategies adopted by our dynamic and collaborative research team entail continuous engagement of those issues by: (1) preparing renewable polymers, (2) chemical diversification of biomass-derived platform chemicals, (3) direct modification of biopolymers, and (4) development of petroleum replacements. Battling the inveterate proclivity towards portents of gloom need not solely justify investigations into biorenewable feedstock chemicals; the ramifications of bioinspired molecular inquiry create opportunities to go beyond mere sustainability through innovation. This dissertation includes specific examples which illustrate utilization of three types of biomass: (1) oil seeds, (2) lignin, and (3) carbohydrates. Each class of biomass-derived materials offered unique advantages as well as challenges associated with their varied structures. The presentation has been divided into five sections: (1) biomass, sustainable chemistry and design thinking; (2) styrene replacements and their application in renewable vinyl ester thermosets; (3) catalyst-free lignin valorization by acetoacetylation; (4) chemical diversification of 5-(hydroxymethyl)furfural; (5) valorization of cellulose-derivable platform chemicals by cycloaddition with a potentially bioderivable reactive intermediate: benzyne.Item 4-Dimethylamino Pyridine (DMAP) Catalyst with Fluxional Chirality: Synthesis and Applications(North Dakota State University, 2016) Ma, GaoyuanOrganocatalysis using small organic molecules to catalyze organic transformations, has emerged as a powerful synthetic tool that is complementary to metal-catalyzed transformations and remarkably promote stereoselective synthesis. Our group has designed useful templates, ligands, and additives that use fluxional groups to control and/or enhance stereoselectivity in a variety of asymmetric transformations. A key feature of this strategy is that the size of the fluxional substituent can be varied readily. As an extension of this strategy we became interested in developing efficient and broadly applicable and adjustable 4-dimethylaminopyridine (DMAP) organocatalysts. In our design, we surmised that a fluxional group would be effective in relaying stereochemical information from the fixed chiral center to the catalytic center of DMAP. Presented herein the synthesis of novel fluxionally chiral DMAP catalysts and their application in the acylative kinetic resolution of secondary alcohols and axially chiral biaryls, dynamic kinetic resolution of chiral biaryls with low rotation barriers and allylic substitution reactions. In the beginning, a comprehensive study of the chiral relay concept in enantioselective transformations was reviewed and the historic and current story of the chiral relay concept is covered. The design and synthesis of fluxionally chiral 4-dimethylaminopyridine catalysts was introduced. The key issues addressed in this chapter include the design concept regarding a stereoselective fluxionally 4-dimethylaminopyridine catalyst and muti-step synthesis strategies developed for catalyst synthesis. The development of fluxionally chiral 4-dimethylaminopyridine catalysts in the acylative kinetic resolution studies of secondary alcohols as well as axially chiral biaryls is investigated. Six different secondary alcohols are resolved with good selectivity factors (6-37) and ten biaryl substrates are resolved with moderate to high selectivity factors (10-51). Dynamic kinetic resolution has more practical applications to organic synthesis than simple kinetic resolution. The dynamic kinetic resolution of atropisomeric biaryls using the novel fluxionally chiral 4-dimethylaminopyridine catalysts was explored and the corresponding acylated products were obtained with 11-80 %ee. The newly designed DMAP catalysts containing fluxional groups as a stereocontrol unit could also be effectively applied as a nucleophilic catalyst in asymmetric allylic aminations. A range of α-methylene-β-amino esters were obtained with good yields and selectivities (up to 72 %ee).Item Achiral Templates in Asymmetric Catalysis: Applications in Construction of All Carbon Quaternary Centers(North Dakota State University, 2018) Subramanian, HariharaputhiranConjugated olefins are readily available and inexpensive starting materials and their functionalization offers a rapid access to many important building blocks for organic synthesis. The functionalization of these olefins by asymmetric catalytic methods for the formation of C-C and C-X bonds is an active area of research. Major advances in this field are not only triggered by the development of new catalysts but also by engineering of new acceptor olefins. In our lab we have successfully developed acceptor olefins appended to alkoxyimidazoles as a novel template. Using these templated acceptors, we demonstrated methodologies to construct all carbon-quaternary centers, one of the demanding tasks in synthetic methodology development. We have also made significant efforts towards understanding the solution structures of the intermediates involved in the catalytic asymmetric reactions developed in our lab. In chapter 1, the importance of templated acceptors in the field of chemical synthesis with special emphasis on acylimidazoles is reviewed. The versatility of the N-alkylimidazole templates is showcased by their utility in several organic transformations. In chapter 2, modes of activation of acceptor olefins by catalysts, need for templated acceptors and challenges associated with designing an asymmetric catalytic process is described. Our approach in designing novel acceptors based on imidazoles is also described. In chapter 3 the synthetic utility of these novel N-alkoxyimidazole based acceptors is shown by enantioselective construction all carbon quaternary centers by Lewis-acid catalysis. We also compare the effectiveness of other templates such as oxazolidinone and N-methylimidazoles in the Lewis-acidic catalyzed Friedel-Crafts alkylation reaction. The effect of various parameters such as Lewis acid, chiral ligands, temperature, additives and solvents on the conjugate addition of Friedel-Crafts nucleophiles are presented in this chapter. In chapter 4, our research efforts toward understanding solution structures of intermediates involved in catalytic asymmetric reactions are presented. A combination of Diffusion Ordered Spectroscopy (DOSY), heteronuclear NMR spectroscopy, mass spectrometry and X-ray crystallography has been used to study the solution structure of intermediates involved in asymmetric catalytic reactions. In chapter 5, a future outlook on templated chemistry developed in our laboratory is presented. Some preliminary results pertinent to future projects are presented.Item Interactions of Light with Organic Chromophores: A Photochemical and Photophysical Investigation(North Dakota State University, 2018) Clay, Anthony MarcelOver the past century, light has emerged as a useful tool finding utility in various fields such as device fabrication, the medical field, as well as utility as an energy source. Chemist have adopted this abundant energy source to do work in material applications and to mediate simple chemical transformations. In regards to the latter, light utilized as a traceless benign reagent for organic transformations has proven fruitful and therefore unequalled in its ability to afford structural complexity from simple starting material(s). Photon absorption of the correct energy elevates organic molecules to a high energy excited state of “short” finite lifetime. In order to afford photoproducts of high selectivity or merely dictate the outcome of a desired photoreaction, control must exist during this short-lived excited state. This dissertation describes a complementary approach to already established photochemical methodologies by which excited state control can be employed in efforts to afford photoproducts of enhanced selectivity. By employing the NEER principle (Non-Equilibrating Excited State Rotamers) and exploiting axial chiral substrates and thereby implementing rotamer control in the excited state, photoproducts of high chemoselectivity, diastereoselectivity and enantioselectivity can be accessed. Additionally, by judicious choice of chromophore control over the excited state process can be gained affording materials of desired physical properties. It was determined that altering the functionality of bio-based feedstocks afforded photoresponsive molecules with altered photoreactivity. Photoacids and photoinitiators were synthesized and their photophysical properties were investigated. Photoinitiators were evaluated for their efficacy towards photochemical polymerization. This dissertation details synthesis, characterization and photophysical investigations of various organic chromophores in efforts to provide mechanistic rationale regarding atropisomeric photoreactions and utility of biobased photoresponsive molecules.Item Lung Mucosal Response to Repeated Inhalational Insults with Immunomodulatory Agents in a Murine Model of Fungal Asthma: Airway Epithelium Takes the Center Stage(North Dakota State University, 2013) Pandey, SumaliAsthma is a debilitating disease of the lungs affecting 235 million people worldwide. Fungus-associated asthma leads to a particularly severe type of disease, and exposure to environmental fungi and their products is unavoidable due to the ubiquitous nature of fungal species. Besides being allergenic, fungi are opportunistic pathogens, and anti-fungal and/or allergic pathways may be modified through repeated inhalation of immunomodulatory agents, affecting the outcome of fungus-induced asthma. Our aim in this project was to investigate the extent to which repeated inhalation of immunomodulatory agents influence the lung mucosal responses in a naïve murine host or in one that had been sensitized to fungal proteins (allergic). The immunomodulatory substances chosen hold relevance to human inhalational exposure, and included live or irradiation-killed Aspergillus fumigatus (a fungi) spores, deoxyxnivalenol (a mycotoxin), and fluticasone propionate (an inhalationally administered corticosteroid, commonly prescribed for allergic asthma). In a naïve host, inhalation of live A. fumigatus spores showed pathological features of fungal asthma. However, in an allergen-sensitized lung, both dead and live A. fumigatus spores established fungal airway disease, albeit to different extents. Next, we tested the effect of deoxynivalenol in an allergic host and found that its repeated inhalation did not affect pulmonary disease pathology, but did lead to a dose- and time- dependent increase in mucosal and systemic total IgA. Finally, we tested the effect of fluticasone propionate, and found that it did not influence the development of fungal airway disease, but did induce dynamic changes in lung physiology and antibody titers. Besides mimicking human inhalational exposures, inhalation ensures direct interaction of the inhaled substances with airway epithelium, which plays an important role in defense against inhaled substances and in asthma pathophysiology. By analyzing various mechanisms involved in murine lung-mucosal response to the inhaled substances, a critical involvement of airway epithelium as an orchestrator of immune responses is highlighted, and this would inform mechanism-based future studies. In conclusion, this project is likely to aid in establishing evidence based standards for fungus-related exposures and in making informed therapeutic decisions for fungus-associated diseases.Item Stereoselective Carbon-Carbon Bond Construction Using Indium and Bismuth: New Methods in Green Chemistry(North Dakota State University, 2012) Balasubramanian, NarayanaganeshSelective chemical reactions that can be accomplished with minimal waste using non-toxic catalysts and reagents will allow for new greener chemical processes for future environmentally sustainable technologies. This work will present an account on enantioselective nucleophilic addition to carbon-nitrogen and carbon-oxygen double bonds mediated by the environmentally benign indium and bismuth metals. The dissertation entitled “ Stereoselective carbon-carbon bond construction using indium and bismuth: new methods in green chemistry” is divided into three chapters Chapter one outlines a few concepts in green chemistry and background information on the vital role of indium and bismuth in present day organic synthesis. The development of a procedure for using allylic alcohol derivatives for ümpolung type allylation of chiral hydrazones is described in chapter two. This procedure affords homo allylic amines in good yields and excellent diastereoselectivity. An interesting study with respect to the mechanism of the reaction has been conducted. Switching gears towards the end of this chapter, ultrasound-promoted indium-mediated Reformatsky reaction of chiral hydrazones is described. This chapter describes a potential green chemical method for making β-amino acids. In chapter three, indium mediated enantioselective allylation of α-ketoamides is described. The developed procedure is applied in the allylation of linear and cyclic α- ketoamides. Overall, an operationally simple and environmentally benign stratergy development has been explained. The later section of this chapter discusses the Reformatsky reaction in isatin series using the same protocol applied for imines. To fully explore any organometallic reaction, it is important to understand the mechanism with which they operate at molecular level. Chapter three outlines some of our attempts to understand the enantioselective indium and bismuth mediated allylation and the nature of chiral- indium and bismuth Lewis acids. A postive non-linear effect has been observed and studied in bismuth-mediated allylation. Key findings obtained in each chapter and their implications to the future of our research is also discussed in each chapter. The chapters also details on what we understood about the potentials of organoindium and organobismuth chemistry towards developing new green chemical methods.Item Highly Functionalized Thermosets from Renewables for Composites and Coatings Applications(North Dakota State University, 2017) Yu, ArvinRenewable sources have attracted attention due to their affordable cost and wide availability. Vegetable oils are renewable sources that have been extensively studied as potential replacement for petroleum derived chemicals. However, vegetable oils tend to produce soft materials with modest properties due to their chemical structure. Consequently, their modifications have been studied to develop high performance materials with improved properties. One of the modifications involves substituting the glycerol core with sucrose to increase the functionality per molecule. Another approach is converting the less reactive internal carbon-carbon double bonds with the more reactive epoxy groups, which permits access to a variety of crosslinking pathways. Epoxidized sucrose soyate (ESS) is a sucrose ester fatty acid (SEFA), which was epoxidized via the Prilezhaev reaction. ESS has a rigid sucrose core and epoxy functionalized fatty acid side chains. The high functionality of ESS was exploited and it was converted to methacrylated and carbonated resins. The methacrylated resins were applied in producing themosets by free-radical polymerizations while the carbonated resins were studied in step-growth polymerizations. Several studies were done to exploit the high functionality of the methacrylated resins: reduction of the viscosity while increasing crosslinkable moieties, introduction of ductility, structure-property relationships, and investigation of resin versatility in photocurable systems. Meanwhile, the carbonated resins were used to form non-isocyanate polyurethane (NIPU) coatings via cyclic carbonate-amine reactions. Overall, the highly functionalized bio-based thermosets showed very promising properties for composites and coatings applications.Item Novel Asymmetric Approaches for Construction of Small Molecules by Cyclization and Cycloaddition(North Dakota State University, 2015) Moorthy, RamkumarDevelopment of novel asymmetric and catalytic methods for synthesizing small organic molecules containing hindered quaternary and tertiary centers is a major challenge and a dynamic area of investigation in synthetic organic chemistry. The incorporation of these chiral centers into small molecules such as cyclopropanes, aziridines or isoxazolidines is important because they are present in a large number of biologically active natural products as well as in synthetically designed pharmaceutical agents. However, the synthesis of non-natural compounds containing quaternary and tertiary centers that have potential as therapeutics are scarce due to the limited number of readily available methods. We have successfully used 1-(benzyloxy)imidazole as a new bidentate coordinating template for dipolar cycloaddition and cyclization reactions using chiral Lewis acid as a promoter to access these highly functionalized small molecules in high yields and selectivity. Chapter 1. Review for Michael Initiated Ring Closure (MIRC) reaction. The chapter provides different diastereo- and enantioselective strategies for the construction of chiral cyclopropanes. Also, the chapter will provide the current methodologies developed for MIRC reaction. Chapter 2. Development of a novel chiral Lewis acid methodology for synthesizing highly strained cyclopropanes with chiral quaternary and tertiary centers using Michael Initiated Ring Closure (MIRC) reaction for β-substituted and β,β-disubstituted enones with N-benzyloxy imidazole as an achiral template. Different types of nucleophiles such as sulfur ylides and bromomalonate were successfully employed in the MIRC reaction. Chapter 3. Development of a novel chiral Lewis acid methodology for synthesizing highly strained chiral CF3-substituted aziridines using aza-Michael initiated ring closure reaction (aza-MIRC). The reaction involves β,β-disubstituted enones with N-benzyloxy imidazole as an achiral template and N-nosyloxy carbamate as ‘nitrene’ source. Chapter 4. Development of N-benzyloxy imidazole template as a chelating scaffold for chiral Lewis acid catalyzed enantioselective nitrone cycloaddition of β,β-disubstituted enones for the construction of isoxazolidines with trifluoromethyl group is described. The N-benzyloxy imidazole in the cycloadduct was efficiently transformed into corresponding isoxazolidine ester, which could be further converted into useful precursors such as β-hydroxycarbonyls, 1,3-diols, β-aminoalcohols, β-aminoacids, β-lactams and other functionalized building blocks.Item New Strategies for Ruthenium Catalyzed C-C Bond Formation(North Dakota State University, 2014) Zhang, JingTransition metal-catalyzed C-H bond activation allows direct functionalization of the ubiquitous C-H bonds in organic molecules to increase the molecular complexity. Since Murai's pioneering work in ruthenium catalyzed regioselective arene-alkene coupling reaction, a number of transition metal catalysts have been developed for C-C bond formation via C-H bond activation. However, metal-catalyzed C-H functionalization faces a number of long-standing challenges such as the control over regio- and stereoselectivity and harsh reaction conditions. Presented herein is our research on the development of ruthenium(II)-based catalysts for new and improved methods in C-C bond formations by formal activation of sp2 C-H bonds and subsequent coupling with alkyne substrates. Chapter 1 introduces the background of alkyne hydroarylation initiated by transition metal-catalyzed C-H bond activation and the significance to develop new strategies to overcome the limitations of current methods. In Chapter 2 and Chapter 3, ruthenium(II)-N-heterocyclic carbene (NHC) catalyst systems were developed for efficient [3+2] carbocyclization between N-H aromatic ketimines or aromatic ketones and internal alkynes under very mild conditions. This process incorporates the ortho-directing imine and ketone groups for C-H bond activation into the overall transformation in a tandem manner and enables efficient access to indenyl amines and alcohols in high yields. Chapter 4 describes the development of bis-cyclometalated ruthenium(II) complexes with readily available N-H aromatic ketimine and ketone ligands as a new class of catalyst precursors for C-C coupling reactions. The catalytic activity of the bis(imine) complex is evaluated in several catalytic coupling reactions of alkene and alkyne substrates. The coupling reactions are proposed to proceed by Ru(II)/Ru(IV) catalytic cycles involving C-C bond formation by oxidative cyclization. Chapter 5 details the development of a decarboxylative alkyne hydroarylation process to synthesize arylalkenes with controlled and versatile regiochemistry of aromatic substituents. Following a tandem sequence of C-H bond activation and alkyne coupling, the subsequent decarboxylation is facilitated by the newly installed ortho-alkenyl moiety and is compatible with various aromatic substituents at para-, meta- and ortho-positions. This new decarboxylation strategy eliminates the prerequisite of substrate activation by ortho-substitution and allows a broad scope of substituted benzoic acids to serve as aromatic building blocks for alkyne hydroarylation.Item Novel Synthetic Routes to Complex Amines: the Catalytic Hydroamination of Alkynes and Hydroimination of Allenes(North Dakota State University, 2016) Moran, Erik JohnAmines are valuable targets for synthesis in contexts of both research and industrial applications. This work proposes two atom-economical methods—hydroamination (HAM) and hydroimination (HIM)—as C-N bond formation strategies. A nickel-(N-heterocyclic carbene) catalyst system was developed to carry out HAM of internal, unactivated alkynes with aryl amines and cyclic secondary amines. It was demonstrated that the Ni-NHC catalyst was capable of promoting both HAM at room temperature and transfer hydrogenation to produce α-branched aryl amines. These two procedures were performed by the same catalyst to demonstrate an elegant 1-pot, multi-transformation protocol. Separately, optimization of a Rh-HIM catalyst system for the combination of monosubstituted allenes and aromatic N-H-ketimine was carried out to favor high conversion of substrates to the linear HIM product rather than [3+2] annulation. Both HAM and HIM C-N bond formation methods were found to be successful and capable of good conversion and selectivity for their respective products.
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