Experiments were performed with naphthalene and a-naphthol to compare the processes involved in the sorption of a polycyclic aromatic hydrocarbon (PAH) and its metabolite, respectively, and to assess the bioavailability of these two compounds adsorbed to two sandy soils with different organic carbon contents. Adsorption conditions were varied to estimate the extent that biologically-mediated and chemically-induced oxidative coupling, and rate-limited diffusive processes contributed to the apparent irreversible adsorption of these compounds. The purposes of this research were to: (1) investigate the processes which cause the irreversible adsorption of organic contaminants to soil~ (2) gauge the impact that these different adsorption processes have on the bioavailability of sorbed contaminants; and, (3) evaluate the environmental significance of these processes in soils and the subsurface. This dissertation has been prepared as three separate articles for publication in peer reviewed journals. The first article serves as a literature review in evaluating the significance of oxidative coupling reactions in soil and subsurface environments. This review concludes that oxidative coupling of organic contaminants may be important in soils and could be stimulated as a viable remediation strategy. For subsurface systems oxidative coupling appears much more limited, however, engineered systems could be developed to enhance this process. The second article presents experimental results used to quantify the individual processes involved in the irreversible adsorption of naphthalene and a-naphthol. This article concludes that both biological and chemical catalysts are important in promoting irreversible adsorption reactions, and that once the partial oxidation of a PAH occurs, oxidative coupling can become a significant process affecting contaminant fate. The third and final article examines the effect of different adsorption processes on the subsequent bioavailability of sorbed naphthalene and anaphthol, and concludes that the biodegradation of naphthalene and α-naphthol adsorbed to both the soils tested was controlled by the rate of desorption and the reversibility of the adsorption process. / Ph. D.

With the increasing production of natural gas as a result of the advancement in the technology, methane conversion to more valuable products has become a must. One of the most attractive processes which allow the utilization of the world’s most abundant hydrocarbon is the oxidative coupling. The main advantage of this process is the ability of converting methane into higher paraffins and olefins (primarily C2) in a direct way using a single reactor. Nevertheless, low C2+ yields have prevented the process to be commercialized despite the fact that great number of attempts to prepare catalysts were conducted so that it can be economically viable. Due to these limitations, understanding the mechanism and kinetics of the reaction can be utilized in improving the catalysts’ performance. The reaction involves the formation of methyl radicals that undergo gas-phase radical reactions. CH4 activation is believed to be done the surface oxygen species. However, recent studies showed that, in addition to the surface oxygen mediated pathway, an OH radical mediated pathway have a large contribution on the CH4 activation. The experiments of Li/MgO, Sr/La2O3 and NaWO4/SiO2 catalysts revealed variation of behavior in activity and selectivity. In addition, water effect analysis showed that Li/MgO deactivate at the presence of water due to sintering phenomena and the loss of active sites. On the other hand, negative effect on the C2 yield and CH4 conversion rate was observed with Sr/La2O3 with increasing the water partial pressure. Na2WO4/SiO2 showed a positive behavior with water in terms of CH4 conversion and C2 yield. In addition, the increment in CH4 conversion rate was found to be proportional with PO2 ¼ PH2O ½ which is consistent with the formation of OH radicals and the OH-mediated pathway. Experiments of using ring-dye laser, which is used to detect OH in combustion experiments, were tried in order to detect OH radicals in the gas-phase of the catalyst. Nevertheless, noisy signals were obtained that prevented the ability of detecting OH at the expected few ppms concentrations. Further optimization of the experimental setup is required.

Oxidative coupling of methane (OCM) represents a potentially viable method to convert methane directly into more desirable products such as ethane, and ethylene. In this dissertation, a comprehensive kinetic study of oxidative coupling of methane was performed over La2O3-based catalysts. An accurate and reliable gas-phase model is critical for the entire mechanism. The gas-phase kinetics was first studied using a jet-stirred reactor without catalyst. Both experiments and simulations were conducted under various operating conditions using different gas-phase models. Quantities of interest and rate of production analyses on hydrocarbon products were also performed to evaluate the models. NUIGMech1.1 was selected as the most comprehensive model to describe the OCM gas-phase kinetics and used for the next study. Next, microkinetic analysis on La2O3-based catalysts with different dopants was performed. The Ce addition has the greatest boost over the performance. The kinetics at low conversion regimes were analyzed and correlated to the catalysts’ properties. The activation energy for methane hydrogen abstraction was estimated, with the formation rate of primary products, which suggested that the initiation reaction steps were similar for La2O3-based catalyst. A homogeneous-heterogeneous kinetic model for La2O3/CeO2 catalyst was then constructed. By applying in situ XRD, the doping of CeO2 not only enhanced catalytic performance but also improved catalyst stability from CO2 and H2O. A wide range of operating conditions was investigated experimentally and numerically, where a packed bed reactor model was constructed based on the dimensions of experimental setup and catalyst characterization. The rate of production (ROP) was also performed to identify the important reactions and prove the necessity of surface reactions for the OCM process. Laser-induced fluorescence was implemented to directly observe the presence of formaldehyde. The last section includes the implementation of in situ laser diagnosis techniques at the near-surface region to solve the existing challenges. Raman scattering was implemented to quantitate the concentration profiles of major stable species near the surface and measure the in situ local temperatures at different heights above the catalyst surface, to study the kinetics transiting from the surface edge to the near-surface gas phase and provide a new perspective in OCM kinetic studies.

In this thesis, the effect of fluorinating reagents on a selection of transition metal-mediated organic transformations was investigated. The first four chapters are focused on gold-catalysed nucleophilic addition processes performed in the presence of “F⁺” sources. Chapter 1 provides a general introduction to homogeneous gold catalysis and summarises the aims and objectives of the project. The effect of the electrophilic fluorinating reagent Selectfluor (82) on the gold-catalysed rearrangement of propargyl acetates 85 is discussed in Chapter 2. α-Fluoroenones 92 resulting from fluorodeacetylation of an allenyl acetate intermediate were delivered as the major products of these reactions (Scheme i). [Scheme i Gold-Catalysed Rearrangement-Fluorodeacetylation of Propargyl Acetates 85.] By contrast, performing the gold(I)-catalysed cyclisation of allenoates 102 in the presence of Selectfluor (82) led to products of oxidative coupling. The “F⁺” source in these processes most likely acts as an external oxidant in an Au<sup>I</sup</Au^III redox cycle. In Chapter 3, the cascade cyclisation-intramolecular arylation of benzyl-substituted substrates is discussed whilst the extension of the methodology towards intermolecular homocoupling and intermolecular alkynylation is presented in Chapter 4 (Scheme ii). [Scheme ii Gold-Catalysed Cyclisation-Oxidative Coupling of tert-Butyl Allenoates 102.] In Chapter 5, the feasibility of palladium-catalysed allylic [¹⁸F]radiofluorination was investigated using high-specific-activity [¹⁸F]fluoride. This study led to the development of the first transition metal-mediated C-¹⁸F bond-forming process of relevance for the preparation of radiotracers for PET imaging (Scheme iii). [Scheme iii Palladium-Catalysed Allylic [18F]Radiofluorination of Allylic Methyl Carbonate 227b.] Chapter 6 gives full experimental procedures and characterisation data for all compounds.

Orientador: Gustavo Paim Valença / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-07-31T19:58:48Z (GMT). No. of bitstreams: 1 Paloschi_RozileiaSimoni_M.pdf: 2623823 bytes, checksum: 569787d9b56d1368559be20011050e5e (MD5) Previous issue date: 2002 / Resumo: A conversão catalítica de metano para combustível liquido ou outros produtos químicos é de grande interesse e muitas tentativas de utilização têm sido feitas para ativar metano em condições não oxidativas e convertê-lo em hidrocarbonetos grandes e compostos aromáticos. Neste trabalho, duas zeólitas H-ZMS-5 com razões Si/AI diferentes e uma zeólita H-Y foram impregnadas com 3% p/p de Mo e testadas na reação de acoplamento não oxidativo de metano. Análises de DRX e FTIR demonstraram que o Mo está bem disperso na superfície nos canais das zeólitas. A área superficial BET e o volume de poros apresentaram uma pequena redução após a impregnação. As reações foram feitas a 973 K. O catalisador Mo/H-Y só apresentou CO e H2 como produtos. O catalisador MO/H-ZSM-5 com a zeólita de menor razão Si/AI apresentou a maior conversão de metano e seletividade à benzeno quando a reação foi realizada em condição de baixa velocidade espacial de metano. A adição de 40% de H2 não favorece a formação de hidrocarbonetos C2 e aromáticos, enquanto a adição de apenas 10% resultou em um aumento na estabilidade da conversão de metano, especialmente para a zeólita com menor razão Si/AI. A adição de 20% de H2 resultou em menor conversão de metano e seletividade a benzeno quando comparada às reações sem adição de co-reagente e com 10% de co-reagente. Foram feitas também reações a 923 K e 1023 K para a determinação da energia de ativação. O catalisador 3Mo/H-ZSM-5 com menor razão Si/AI desativou completamente após 13 h de reação, enquanto o catalisador 3Mo/H-ZSM-5 com maior razão Si/AI desativou completamente após 9 h de reação. Este último foi regenerado por passagem de oxigênio à temperatura entre 723 e 823 K e testado novamente na reação de acoplamento não oxidativo de metano, apresentando valores de conversão de metano e seletividade à benzeno equivalentes aos observados na reação com o catalisador não regenerado / Abstract: The catalytic conversion of methane to liquid fuels or commodity chemicals is an attactive process that has received a great dela of attention recently. The conversion of methane under nonoxidative conditions results in longer chain hydrocarbons and aromatics compounds. In this work, two H-ZSM-5 zeolites with different Si/AI ratios and one H-Y zeolite were loaded with 3wt% Mo. They were used as catalysts in the reaction of nonoxidative coupling of methane. XRD and FTIR analysis showed that the molybdenum species are uniformly distributed on the surface in the channels of the zeolites. The BET surface area and the pore volume decreased slightly after impregnation with Mo. The reactions were carried out at 973 K. The only products for the Mo/H-Y smaples were CO and H2. The methane conversion and selectivity to benzene were higher for the Mo/H-ZSM-5 catalyst with lower Si/AI ratio and for lower methane space velocity. The nonoxidative coipling of methane reaction did not occur when 40% hydrogen were added to the methane feed stream. However, the methane conversion became stable and increase as 10% hydrogen were added to methane. This was true for the zeolite with lower Si/AI ratio. When 20% hydrogen were added to the methane feed stream, the methane conversion and selectivity to benzene were lower than when 10% hydrogen or no hydrogen were added to the feedstream. Reactions were carried out at 923 and 1023 K in order to determine the activation energy. The activation energy values were similar fo the reaction on the zeolites with different Si/AI ratios. The catalyst with lower Si/AI ratio deactivated after 13 h and the catalyst with higher Si/AI ratio deactivated after 9 h on stream. The catalyst with higher So/SI ratio was regenerated by flowing oxygen at temperatures between 723 and 823 K. After regeneration the catalyst had the same catalytic performance as the ¿fresh¿ catalyst / Mestrado / Desenvolvimento de Processos Químicos / Mestre em Engenharia Química

Le noyau benzofuro[2,3-b]indoline est une structure complexe que l’on retrouve dans différentes substances naturelles telles que l’azonazine, la voacalgine A, la bipleiophylline ou encore le diazonamide A. Ces produits naturels possèdent une activité biologique intéressante et plus particulièrement le diazonamide A avec un IC50 inférieur à 15ng/mL sur plusieurs lignées cellulaires cancéreuses. De plus, certaines de ces substances n’ont jamais été synthétisées à ce jour. Lors de la biogénèse de ces composés, il est supposé que le motif benzofuroindoline est créé par un couplage oxydant entre un indole et un phénol. Nous avons ainsi entrepris de développer différentes méthodologies de synthèse biomimétiques du motif benzofuroindoline. Inspiré par les biosynthèses de l’azonazine et du diazonamide A, nous avons développé une arylation diastéréodivergente du tryptophane par la tyrosine. Les diverses méthodologies de synthèse de benzofuroindolines existantes effectuant ce couplage ne permettent pas un contrôle stéréosélectif. Nous avons remédiés à ce problème en réalisant une réaction de Friedel-Crafts entre une tyrosine protégée et des exo- et endo-bromopyrroloindolines issues stéréosélectivement du tryptophane. Cette réaction procède avec rétention de configuration et nous permettent une synthèse diastéréodivergente de précurseurs potentiels du diazonamide et de l’azonazine. Une méthodologie générale de synthèse de benzofuroindolines par un couplage oxydant direct entre des indoles 2,3-disubstitués et des phénols a été développée. Cette réaction implique l’oxydation de l’indole par du N-iodosuccinimide. L’iodoindolénine intermédiaire réagit par action d’un sel d’argent, via une réaction de Friedel-Crafts avec le phénol pour donner la benzofuroindoline en une étape. Une bibliothèque de diverses benzofuroindolines a pu être obtenue par cette stratégie.Cette dernière méthodologie a été appliquée à la synthèse de modèles hexacycliques complexes de la voacalgine A et de la bipleiophylline à partir d’indoles apparentées à la pleiocarpamine que nous avons synthétisés. Une autre stratégie de synthèse du motif benzofuroindoline de la voacalgine A et de la bipleiophylline impliquant l’oxydation d’un catéchol en orthoquinone a également été étudiée. / The benzofuro[2,3-b]indoline core is a complex structure present in several natural products such as azonazine, voacalgine A, bipleiophylline and diazonamide A. These products possess an interesting biological activity and especially diazonamide A with an IC50 below 15ng/mL on different cancer cells lines. Some of these compounds have never been synthesize. It is postulated that the biogenesis of the benzofuroindolines natural products implies an oxidative coupling between indoles and phenols. Therefore, we wished to develop a bioinspired synthesis of benzofuroindoline core.Inspired by the biosynthesis of azonazine and diazonamide A, we developed an diastereodivergent arylation of tryptophan by tyrosine. The existing synthetic methodology of benzofuroindoline involving an oxidative coupling do not allow a stereoselective control. We solved this problem by doing a Friedel-Crafts reaction between a protected tyrosine and the exo-, and endo-bromopyrroloindolines obtained stereoselectively from tryptophan. This reaction witch proceeds with a retention of configuration allowed us to access selectively azonazine and diazonamide A precursors. A general methodology of benzofuroindoline synthesis by an oxidative coupling between 2,3-disubstituted indoles and phenols has then been developed. This reaction proceeds by oxidation of the indole with N-iodosuccinimide. The resulting iodoindoline was then engaged in a Friedel-Crafts reaction with a phenol in presence of a silver salt to form the desired benzofuroindoline in a one-pot operation. Through this method, a library of several benzofuroindolines has been created.This last methodology has been applied to the synthesis of complex hexacyclic voacalgine A and bipleiophylline analogs from pleiocarpamine-like indoles. Another strategy towards the voacalgine A and bipleiophylline benzofuroindoline core has also been studied and involves the oxidation of a catechol into an orthoquinone which can react with an indole.

No description available.

Palladium(II) acetate and palladium(II) chloride react with amino acids in acetone/water to yield cis or trans square planar bis-chelated palladium amino acid complexes. The naturally occurring amino acids and some N-alkylated and substituted derivatives and homologs were evaluated as ligands. Thirty-eight amino acids in total were investigated as ligands. The formation of aquo complexes in water was observed and studied by 13C NMR spectroscopy and modeled by DFT calculations. Each class of amino acid ligand is catalytically active with respect to the oxidative coupling of olefins and phenylboronic acids. Some enantioselectivity is observed and the formation of products not reported in other Pd(II) oxidative couplings is seen. Both activated and non-activated alkenes were oxidatively coupled to phenylboronic acids incorporating both electron-donating and electron-withdrawing groups. The crystal structures of nineteen catalyst complexes were obtained. The extended lattice structures arise from N-H..O or O..(HOH)..O hydrogen bonding. NMR, HRMS, FTIR, single crystal XRD, and powder XRD data are evaluated. / Ph. D.

La vescaline est une substance polyphénolique appartenant à la famille des ellagitannins C-arylglucosidiques qui inhibe in vitro la topoisomérase 2, une enzyme ciblée par les chimiothérapies utilisées contre le cancer. Jusqu’à présent, seuls des ellagitannins porteurs d’unités HHBP ont été obtenus par synthèse totale. La synthèse d’ellagitannins C-arylglucosidiques comme la vescaline, présentant un motif unique de type NHTP relié par une liaison C-arylglucosidique à une unité glucose sous forme ouverte, constitue le challenge de cette thèse. Le premier objectif a été de développer une méthodologie de couplage biarylique intramoléculaire transposable à la construction de l’unité NHTP de la vescaline. Nous avons ainsi mis au point la première méthode de couplage biarylique biomimétique, par action de l’o-chloranil, se déroulant uniquement sur des substrats poly-hydroxylés possédant un groupement méthoxyle en position anomérique du sucre. Moins restrictive, l’utilisation de complexes de cuivre-amine a permis elle aussi de réaliser ce couplage. L’étape suivante de formation biomimétique de la liaison C-arylglucosidique a ensuite été étudiée et le composé attendu a pu être obtenu avec un rendement de 25%, après optimisation des conditions, par réaction dans une solution de tampon phosphate à pH = 7.5. Les deux dernières étapes de la synthèse (galloylation sélective et formation de l’unité NHTP) ne sont pas encore réalisées mais, à ce stade, une seule étape de déprotection peut permettre d’obtenir un premier ellagitannin C-arylglucosidique naturel, l’épi-punicacortéine A 5-O-dégalloylée. / Vescalin is a polyphenol of the C-arylglucosidic ellagitannin subclass that fully inhibits topoisomerase II, an enzyme target in anticancer therapy. Up to date, most synthetic efforts have been directed towards HHBP-bearing ellagitannins. The development of a synthetic way to construct ellagitannins of the C-arylglucosidic subclass, bearing an atropoisomeric NHTP unit linked to an open-chain glucose by a C-arylglucosidic bond, as exemplified by vescalin, is the challenge of this thesis. The first objective was to establish an intramolecular biaryl coupling methodology that could be applied to the construction of vescalin’s NHTP unit. In this context, we developed the first example of biomimetic o-chloranil-mediated oxidative biaryl coupling carried out on a poly-hydroxylated substrate containing a methoxy group at the anomeric position of the sugar. Difficulties in the subsequent deprotection of the methoxy group led us to use an alternative method in which copper-amine complexes allow for the coupling of substrates bearing readily removable anomeric protecting groups. The latter methodology led to the elaboration of HHBP-containing precursors that have been subjected to the biomimetic formation of the C-arylglucosidic bond. After screening both acidic and basic conditions, the desired C-arylglucosidic compound was obtained by carrying out the reaction in a phosphate buffer (pH 7.5) in a 25% yield. The two final steps of the synthesis (selective galloylation and NHTP construction) have not been performed yet but, at this stage, we are confident that a single deprotection step will lead to the first natural C-arylglucosidic ellagitannin, 5-O-degalloyl epi-punicacortein A.

Thesis (Ph, D.)--Miami University, Dept. of Chemistry and Biochemistry, 2008. / Title from second page of PDF document. Includes bibliographical references (p. 77-83).