Olefin metathesis is a valuable synthetic tool, widely used in several fields of science. Due to the importance of this transformation several contributions have been made in this field in order to understand mechanistic aspects, reactivity and applicability of this process. In this topic, ruthenium indenylidene complexes have shown great activity and stability in metathesis, making them very valuable pre-catalysts. However, several aspects of these pre-catalysts have not been evaluated yet. For example, even though reports of active second generation ruthenium indenylidene complexes bearing bulky N-heterocyclic carbenes are present in the literature, no studies have been done to understand how steric hindrance affects the process. For these reasons, [RuCl₂(IPr*)(PPh₃)(3-phenylindenylidene)] (IPr*-PPh₃) and [RuCl₂(IPr*)(Py)(3-phenylindenylidene)] (IPr*-Py), bearing the very bulky ligand, IPr* have been synthesised and compared with [RuCl₂(IPr)(PPh₃)(3-phenylindenylidene)] (IPr-PPh₃) and the new [RuCl₂(IPr)(Py)(3-phenylindenylidene)] (IPr-Py). Another important aspect, presented in this thesis, is the investigation of the stability of indenylidene pre-catalysts in alcohol solvents. Surprisingly, several different decomposition processes occur depending on the starting complex and the alcohol used. Mechanistic investigation into this decomposition, allowed us to develop a better understanding of this process, and to predict the decomposition product based on the environment. In particular, this study revealed that [RuCl(η⁵-3-phenylindenyl)(PPh₃)₂] (Eta-5) is accessed from [RuCl₂(3-phenylindenylidene)(PPh₃)₂] (M₁₀) via a novel indenylidene to η⁵-indenyl rearrangement. This formal decomposition product has been found to be active in at least 20 different catalytic transformations, rendering it a versatile catalytic tool.

Thesis advisor: Amir H. Hoveyda / Chapter 1. Mechanistic Insights and Factors Influencing Polytopal Rearrangements in Stereogenic-at-Ru Carbenes. Herein, the mechanistic elucidation of the stereochemical inversion in stereogenic-at-Ru carbene complexes through olefin metathesis (OM) and non-olefin metathesis (non-OM) based polytopal rearrangements is provided. Our investigations involve the isolation and characterization of previously hypothesized higher-energy (e.g., endo-anti) and lower-energy (e.g., exo-anti) diastereomers, and their interconversion under thermal and/or acid-catalyzed conditions is demonstrated. Furthermore, our computational efforts highlighting the importance of the anionic ligands, due to their critical role in trans influence, dipolar interactions, and e-e repulsions, in polytopal rearrangements are reported. Finally, the positive influence of H-bonding in OM and non-OM processes is also rationalized. (a) Khan, R. K. M.; Zhugralin, A. R.; Torker, S.; O'Brien, R. V.; Lombardi, P. J. and Hoveyda, A. H. "Synthesis, Isolation, Characterization, and Reactivity of High-Energy Stereogenic-at-Ru Carbenes: Stereochemical Inversion Through Olefin Metathesis and Other Pathways," J. Am. Chem. Soc. 2012, 134, 12438-12441. (b) Torker, S.; Khan, R. K. M. and Hoveyda, A. H. "The Influence of Anionic Ligands on Stereoisomerism of Ru Carbenes and Their Importance to Efficiency and Selectivity of Catalytic Olefin Metathesis Reactions," J. Am. Chem. Soc. 2014, 136, 3439-3455. Chapter 2. Highly Z- and Enantioselective Ring-Opening/Cross-Metathesis of Enol Ethers Through Curtin-Hammett Kinetics. The first instances of Z- and enantioselective Ru-catalyzed olefin metathesis are presented. Ring-opening/cross-metathesis (ROCM) reactions of oxabicyclic alkenes and enol ethers and a phenyl vinyl sulfide are promoted by 0.5-5.0 mol % of enantiomerically pure stereogenic-at-Ru complexes with an aryloxy chelate tethered to the N-heterocyclic carbene. Products are formed efficiently and with exceptional enantioselectivity (up to >98:2 enantiomer ratio). Surprisingly, the enantioselective ROCM reactions proceed with high Z selectivity (up to >98% Z). Moreover, reactions proceed with the opposite sense of enantioselectivity versus aryl olefins, which afford E- isomers exclusively. DFT calculations and deuterium-scrambling experiments, indicating fast interconversion between endo- and exo-Fischer carbene diastereomers, support a Curtin-Hammett situation. On this basis, models accounting for the stereoselectivity levels and trends are provided. Furthermore, the correlation of Fischer carbene character to the observed chemoselectivity in ROCM with enol ethers is also disclosed. Finally, a general proposal for the substrate-controlled Z selectivity in OM is also discussed. (a) Khan, R. K. M.; O'Brien, R. V.; Torker, S.; Li, B. and Hoveyda, A. H. "Z- and Enantioselective Ring-Opening Cross-Metathesis with Enol Ethers Catalyzed by Stereogenic-at-Ru Carbenes: Reactivity, Selectivity, and Curtin-Hammett Kinetics," J. Am. Chem. Soc. 2012, 134, 12774-12779. (b) Torker, S.; Koh, M. J.; Khan, R. K. M. and Hoveyda, A. H. "Origin of Z selectivity in Olefin Metathesis Reactions of Certain Terminal Alkenes Catalyzed by Typically E-Selective Ru Carbenes," manuscript submitted. Chapter 3. A New Class of Highly Efficient Ru Catalysts for Z-Selective Olefin Metathesis. Herein, we outline a general design for Z-selective OM, which led to the development of a new class of stereogenic-at-Ru carbene complexes (Ru4-9). Furthermore, we demonstrate that the newly developed dithiolate complexes Ru4b and Ru5 efficiently promote high activity and selectivity in ROMP reactions of norbornene and cyclooctene. Notably, the catechothiolate Ru4b catalyzes Z-selective ROCM with a broad scope of alkenes involving various functional groups (e.g., alcohols, enol ethers, vinyl sulfides, amides, heterocycles, and conjugated 1,3-dienes). More importantly, we disclose that the catecholate complex Ru4a is kinetically non-selective in OM and readily decomposes in the presence of mildly acidic moieties (e.g., alcohols and CDCl3). Subsequently, Ru9 is developed to efficiently promote highly Z-selective CM of a diol cross-partner with a wide range of alkene substrates. Most remarkably, the aforementioned protocol is employed in two natural product syntheses and the OM-based Z-selective cracking of oleic acid, which is unprecedented with existing Ru-carbenes and Mo/W-alkylidenes. (a) Khan, R. K. M.; Torker, S. and Hoveyda, A. H. "Readily Accessible and Easily Modifiable Ru-Based Catalysts for Efficient and Z-Selective Ring-Opening Metathesis Polymerization and Ring-Opening Cross-Metathesis," J. Am. Chem. Soc. 2013, 135, 10258-10261. (b) Koh, M. J.; Khan, R. K. M.; Torker, S. and Hoveyda, A. H. "Broadly Applicable Z- and Diastereoselective Ring-Opening/Cross-Metathesis Catalyzed By a Dithiolate Ru Complex," Angew. Chem., Int. Ed. 2014, 53, 1968-1972. (c) Khan, R. K. M. ; Torker, S. and Hoveyda, A. H. "Reactivity and Selectivity Differences Between Catecholate and Catechothiolate Ru Complexes. Implications Regarding Design of Stereoselective Olefin Metathesis Catalysts," J. Am. Chem. Soc. 2014, 136, 14337-14340. (d) Koh, M. J.; Khan, R. K. M.; Torker, S.; Yu, M.; Mikus, M. S. and Hoveyda, A. H. "Synthesis of High-Value Alcohols, Aldehydes and Acids by Catalytic Z-Selective Cross-Metathesis" manuscript submitted. / Thesis (PhD) — Boston College, 2014. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

Made available in DSpace on 2014-12-17T15:42:05Z (GMT). No. of bitstreams: 1 GuttoRSF_DISSERT.pdf: 5697314 bytes, checksum: 6d49e92c8978493580da74eee2885a8f (MD5) Previous issue date: 2013-02-22 / The present work aims to study the theoretical level of some processes employed in the refining of petroleum fractions and tertiary recovery of this fluid. In the third chapter, we investigate a method of hydrogenation of oil fractions by QTAIM (Quantum Theory of Atoms in Molecules) and thermodynamic parameters. The study of hydrogenation reactions, and the stability of the products formed, is directly related to product improvement in the petrochemical refining. In the fourth chapter, we study the theoretical level of intermolecular interactions that occur in the process of tertiary oil recovery, or competitive interactions involving molecules of non-ionic surfactants, oil and quartz rock where oil is accumulated. Calculations were developed using the semiempirical PM3 method (Parametric Model 3). We studied a set of ten non-ionic surfactants, natural and synthetic origin. The study of rock-surfactant interactions was performed on the surface of the quartz (001) completely hydroxylated. Results were obtained energetic and geometric orientations of various surfactants on quartz. QTAIM was obtained through the analysis of the electron density of interactions, and thus, providing details about the formation of hydrogen bonds and hydrogen-hydrogen systems studied. The results show that the adsorption of ethoxylated surfactants in the rock surface occurs through the hydrogen bonding of the type CH---O, and surfactants derivatives of polyols occurs by OH---O bonds. For structures adsorption studied, the large distance of the surfactant to the surface together with the low values of charge density, indicate that there is a very low interaction, characterizing physical adsorption in all surfactants studied. We demonstrated that surfactants with polar group comprising oxyethylene units, showed the lowest adsorption onto the surface of quartz, unlike the derivatives of polyols / O presente trabalho tem como objetivo o estudo a n?vel te?rico de alguns processos empregados no refino das fra??es do petr?leo e na recupera??o terci?ria deste fluido. No terceiro capitulo, investigamos um m?todo de hidrogena??o das fra??es de petr?leo atrav?s da QTAIM (Quantum Theory of Atoms in Molecules) e par?metros termodin?micos. O estudo das rea??es de hidrogena??o, bem como a estabilidade dos produtos formados, est? diretamente relacionada ? melhoria dos produtos de refino na ind?stria petroqu?mica. No quarto cap?tulo, realizamos o estudo a n?vel te?rico das intera??es intermoleculares que ocorrem no processo de recupera??o terci?ria de petr?leo, ou seja, as intera??es competitivas envolvendo mol?culas de tensoativos n?oi?nicos, o petr?leo e o quartzo da rocha onde o petr?leo est? acumulado. Os c?lculos foram desenvolvidos utilizando o m?todo semi-emp?rico PM3 (Parametric Model 3). Estudamos um conjunto de dez tensoativos n?o-ionicos, de origem natural e sint?ticos. O estudo das intera??es rocha-tensoativo foi realizado sobre a superf?cie do quartzo (001) completamente hidroxilada. Foram obtidos resultados energ?ticos e geom?tricos de v?rias orienta??es dos tensoativos sobre o quartzo. Atrav?s da QTAIM foi obtida a an?lise da densidade eletr?nica das intera??es, e assim, fornecendo detalhes sobre a forma??o de liga??es de hidrog?nio e hidrog?nio-hidrog?nio, nos sistemas estudados. Os resultados obtidos mostram que a adsor??o de tensoativos etoxilados na superf?cie da rocha ocorre atrav?s de liga??o de hidrog?nio do tipo C-H---O, e tensoativos derivados de poli?is ocorre por liga??es O-H---O. Para as estruturas de adsor??o estudadas, a grande dist?ncia do tensoativo para a superf?cie aliada com os baixos valores de densidade de carga, indicam que h? uma intera??o muito fraca, caracterizando uma adsor??o f?sica em todos os tensoativos estudados. Evidenciamos que tensoativos com o grupo polar constitu?do por unidades oxietileno, apresentaram a menor adsor??o sobre a superf?cie do quartzo, ao contr?rio dos derivados de poli?is

The research described in this thesis is directed toward the efficient, enantioselective synthesis of chiral products that have useful functionality. This goal was pursued through catalytic asymmetric hydrogenation, a reaction class that selectively introduces one or two stereocenters into a molecule in an atom-efficient step. This reaction uses a small amount (often <1 mol%) of a chiral catalyst to impart stereoselectivity to the product formed. Though catalytic asymmetric hydrogenation is not a new reaction type, there remain many substrate classes for which it is ineffective. The present thesis describes efforts to extend the reaction to some of these substrates classes. Some of the products synthesized in these studies may eventually find use as building blocks for the production of chiral pharmaceuticals, agrochemicals, or flavouring or colouring agents. However, the primary and immediate aim of this thesis was to develop and demonstrate new catalysts that are rapid and effective in the asymmetric hydrogenation of a broad range of compounds. Paper I describes the design and construction of two new, related chiral iridium compounds that are catalysts for asymmetric hydrogenation. They each contain an N,P-donating phosphinooxazoline ligand that is held together by a rigid bicyclic unit. One of these iridium compounds catalyzed the asymmetric hydrogenation of acyclic aryl imines, often with very good enantioselectivities. This is particularly notable because acyclic imines are difficult to reduce with useful enantioselectivity. The second catalyst was useful for the asymmetric hydrogenation of two aryl olefins. In Paper II, the class of catalysts introduced into Paper I is expanded to include many more related compounds, and these are also applied to the asymmetric hydrogenation of prochiral imines and olefins. By studying a range of related catalysts that differ in a single attribute, we were able to probe how different parts of the catalyst affect the yield and selectivity of the hydrogenation reactions. Whereas iridium catalysts had been applied to the asymmetric hydrogenation of imines and largely unfunctionalized olefins prior to this work (with varied degrees of success), they had not been used to reduce fluoroolefins. Their hydrogenation, which is discussed in Paper III, was complicated by concomitant defluorination to yield non-halogenated alkanes. To combat this problem, several iridium-based hydrogenation catalysts were applied to the reaction. Two catalysts stood out for their ability to produce chiral fluoroalkanes in good enantioselectivity while minimizing the defluorination reaction, and one of these bore a phosphinooxazoline ligand of the type described in Papers I and II. Enol phosphinates are another class of olefins that had not previously been subjected to iridium-catalyzed asymmetric hydrogenation. They do, however, constitute an attractive substrate class, because the product chiral alkyl phosphinates can be transformed into chiral alcohols or chiral phosphines with no erosion of enantiopurity. Iridium complexes of the phosphinooxazoline ligands described in Papers I and II were extremely effective catalysts for the asymmetric hydrogenation of enol phosphinates. They produced alkyl phosphinates from di- and trisubstituted enol phosphinate, β-ketoester-derived enol phosphinates, and even purely alkyl-substituted enol phopshinates, in very high yields and enantioselectivities.

This thesis describes synthesis of new chiral N,P ligands and their evaluation in two types of asymmetric transition-metal catalyzed reactions. The first part of the thesis describes studies in iridium-catalyzed asymmetric hydrogenation. A new class of chiral N,P ligands, imidazole-phosphines, was synthesized and evaluated in the Ir-catalyzed asymmetric hydrogenation of olefins (Paper I). The new ligands proved to be highly efficient and enantioselective in the reaction. Because the substrate scope of Ir-catalyzed asymmetric hydrogenation is still limited to certain types of test substrates, new substrate classes with importance in medicinal and materials chemistry were investigated. Vinyl fluorides were efficiently hydrogenated to fluorine-containing chiral centers by the iridium catalysts with imidazole-phosphine ligands (Paper I). To obtain CF3-bearing chiral centers, we hydrogenated CF3-substituted olefins (Paper II). Ir-catalyzed asymmetric  hydrogenation was highly enantioselective for the functionalized CF3-substituted olefins and the resulting chiral products can be valuable in design of materials such as LCD screens. Ir-catalyzed asymmetric hydrogenation was also evaluated as a route to diarylmethine chiral centers (Paper III). A wide range of new chiral compounds possessing a diarylmethine chiral center was obtained. The second part of the thesis deals with asymmetric intermolecular Heck reaction utilizing N,P ligands. The N,P ligand class of thiazole-phosphines was evaluated in the Heck reaction (Paper IV) and gave high enantioselectivity. Further, the intermolecular Heck reaction was examined using computational and experimental studies (Paper V). This study led to a better understanding of the enantioselectivity in the reaction.

The isolation and identification of the active constituents from an Allium sp. extract possessing antibacterial activity was undertaken. The plant material of interest was extracted, purified and screened for antibacterial activity against a Gram positive bacteria. Multiple trials were performed and the isolation was scaled-up repeatedly, overall three compounds potentially possess the observed activity. One compound was identified to yield the majority of activity, and a refined procedure for its purification was established. Initial characterization studies demonstrated the major isolate of interest is novel compared to other isolates from the Allium genus. A ruthenium-catalyzed homo Diels-Alder [2+2+2] cycloaddition between bicyclo[2.2.1]hepta-2,5-diene and alkynyl phosphonates was also studied. The observed reactivity was found to be dependent on the presence of the phosphonate moiety. The cycloaddition was compatible with a variety of aromatic and aliphatic substituted alkynyl phosphonates providing the corresponding phosphonate substituted deltacyclenes in low to good yields (up to 88%).

The major goals of this thesis were to: (1) create a site-isolated aminosilica material with higher amine loadings than previously reported isolation methods, (2) use spectroscopic, reactivity, and catalytic (olefin polymerization precatalysts) probes to determine isolation of amine groups on these organic/inorganic hybrid materials, (3) synthesize an organic/inorganic hybrid material capable of activating Group 4 olefin polymerization precatalysts, and (4) synthesize a high amine loaded organic/inorganic hybrid material capable of reversibly capturing CO2 in a simulated flue gas stream. The underlying motivation of this research involved the synthesis and design of novel amine and sulfonic acid materials. Traditional routes to synthesize aminosilicas have led to the formation of a high loading of multiple types of amine sites on the silica surface. Part of this research involved the creation of a new aminosilica material via a protection/deprotection method designed to prevent multiple sites, while maintaining a relatively high loading. As a characterization technique, fluorescence spectroscopy of pyrene-based fluorophores loaded on traditional aminosilicas and site-isolated aminosilicas was used to probe the degree of site-isolation obtained with these methods. Also, this protection/deprotection method was compared to other reported isolation techniques with heterogeneous Group 4 constrained-geometry inspired catalysts (CGCs). It was determined that the degree of separation of the amine sites could be controlled with protection/deprotection methods. Furthermore, an increase in the reactivity of the amines and the catalytic activity of CGCs built off of the amines was determined for aminosilicas synthesized by a protection/deprotection method. The second part of this work involved developing organic/inorganic hybrid materials as heterogeneous Brønsted acidic cocatalysts for activation of olefin polymerization precatalysts. This was the first reported organic/inorganic hybrid sulfonic acid functionalized silica material capable of activating metallocenes for the polymerization of ethylene when small amounts of an alkylaluminum was added. Lastly, an organic/inorganic hybrid hyperbranched aminosilica material capable of capturing carbon dioxide from flue gas streams was synthesized. This material was determined to capture CO2 with capacities higher than currently reported aminosilica adsorbents.

Thesis (Ph.D.)--Mississippi State University. Department of Chemistry. / Title from title screen. Includes bibliographical references.

Title from first page of PDF document. Includes bibliographical references (p. 154-156).

Une des voies privilégiées pour réduire la teneur en soufre dans les essences commerciales est l'hydrodésulfuration sélective (HDS) des essences issues du procédé de FCC. Une essence étant composée d'un mélange de composés soufrés (1000 ppm) et d'oléfines (20-40%pds). Il est important de comprendre leur transformation de manière à améliorer l'HDS tout en minimisant l'hydrogénation (HYD) des oléfines. Par conséquent, la transformation de plusieurs molécules modèles soufrées (2-méthylthiophène, 3-méthylthiophène et le benzothiophène) et oléfiniques (hex-1-ène, 4-méthylpent-1-ène, 3,3-diméthylbut-1-ène et 2,3-diméthylbut-2-ène) a été étudiée dans les conditions opératoires d'HDS. Par une approche expérimentale couplée à de la modélisation cinétique, nous avons établi une échelle de réactivité entre les composés soufrés d'une part et les oléfines d'autre part. Le benzothiophène est le composé le plus réactif, mais aussi celui qui est le plus inhibiteur pour la transformation des autres composés soufrés. Concernant les oléfines, l'hex-1-ène est la plus réactive par rapport aux autres oléfines ramifiées. Lorsque ces composés sont en mélange, on constate des inhibitions mutuelles plus au moins conséquentes selon la structure des composés modèles. Ces effets qui résultent de compétitions à l'adsorption entre les molécules à la surface du catalyseur ont été modélisés et quantifiés (constantes cinétique et d'adsorption) à partir d'un modèle unique en considérant le formalisme de Langmuir-Hinshelwood. / A preferred route to reduce the sulfur content on the commercial gasoline is the selective hydrodesulfurization (HDS) process of FCC gasoline. A typical gasoline is composed by a mixture of sulfur (1000 ppm) and olefins (20-40%wt) compounds. Therefore, it is important to understand their transformation in order to improve the HDS and minimizing the olefin hydrogenation (HYD). Consequently, the transformation of various sulfur (2-methylthiophene, 3-methylthiophene and benzothiophene) and olefins (hex-1-ene, 4-methylpent-1-ene, 3,3-dimethylbut-1-ene and 2,3-dimethylbut-2-ene) has been studied under HDS operating conditions.By experimental and theoretical (kinetic modeling) approaches, a reactivity scale has been established between the sulfur compounds on one hand and olefins compounds on the other hand. The benzothiophene is the most reactive compound. However it is the most inhibitor compound for the transformation of others sulfur compounds. Regarding the olefins, the hex-1-ene is the most reactive compound among the others branched compounds. A mutual inhibition has been observed when those compounds are studied in mixture according with their structures. These effects result from competitive adsorption between the molecules on the catalyst surface. These results could be modeled and quantified (adsorption and kinetic constants) from a unique model considering the Langmuir-Hinshelwood formalism.