Rhodium-catalyzed hydroacylation is a powerful and atom-economical method for synthesizing ketones from aldehydes and olefins. Despite this, a narrow scope of reactive substrates has limited the utility and broad application of this transformation. Efforts towards the development of new classes of reactive substrates have focused on the use of oxygen- and sulfur-containing olefins, which have enabled various modes of reactivity and thus allowed access to novel types of hydroacylation products. In addition to reactivity, a key to the success of these transformations is the control of regio-, stereo-, and chemoselectivity. In combination with substrate structure, strategies in enantioselective catalysis and metal-organic cooperative catalysis have been applied to achieve requisite reactivity and selectivity when required. A variety of products, such as medium-sized heterocycles, branched sulfur-containing and β-hydroxy ketones, and ketones bearing quaternary carbon centres have been synthesized via hydroacylation using these strategies. A method for preparing polyelectrolyte-stabilized palladium nanoparticles and their use in Suzuki coupling reactions have also been developed.

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Orientador: Ulf Friedrich Schuchardt / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-06T22:18:12Z (GMT). No. of bitstreams: 1 Garcia_CamilaMartins_M.pdf: 3426251 bytes, checksum: 15281c791da719cabbecd7b5e99be0fa (MD5) Previous issue date: 2006 / Resumo: Neste trabalho sintetizou-se ésteres metílicos de óleo de soja, canola, milho, andiroba e óleo utilizado em frituras. Determinou-se a composição em ácidos graxos desses produtos, a viscosidade cinemática e a densidade. O comportamento dos ésteres em função do abaixamento da temperatura foi avaliado por calorimetria diferencial de varredura (DSC). Na etanólise via catálise básica homogênea, foram utilizados hidróxidos de sódio e de potássio, e metóxido de sódio como catalisadores. Os óleos vegetais empregados foram o óleo de soja e óleo utilizado em frituras. Estudaram-se estratégias para a separação e purificação dos ésteres etílicos. A melhor alternativa encontrada foi a lavagem dos ésteres etílicos após a neutralização do catalisador e subseqüente evaporação do excesso de etanol. Os desempenhos dos catalisadores foram semelhantes e as conversões em ésteres etílicos atingiram valores superiores a 92 % e 98 % nas reações realizadas a 70 °C e a 25 °C, respectivamente. Além das maiores conversões nas reações promovidas em temperatura ambiente, houve a separação espontânea da glicerina após o término da reação. No estudo da transesterificação via catálise ácida heterogênea, sintetizou-se um sólido superácido - a zircônia sulfatada (S-ZrO2) - através de uma rota alternativa sem solventes e precipitação. As condições reacionais para a metanólise de óleo de soja foram avaliadas e os melhores parâmetros foram: 5 % (m/m) de S-ZrO2, temperatura de 120 °C e tempo de reação de 1 hora. Essa condição otimizada foi aplicada à etanólise do óleo de soja. Tais condições foram aplicadas novamente à metanólise, porém utilizando-se uma zircônia sulfatada sintetizada através de um método de precipitação (SZ), e uma zircônia não sulfatada (ZrO2). Os resultados obtidos mostraram que a zircônia não sulfatada (ZrO2) não foi ativa na metanólise de óleo de soja nas condições reacionais otimizadas. A zircônia sulfatada sintetizada por um método convencional (SZ) apresentou uma atividade catalítica insatisfatória (8,5 % de conversão), muito menor que a da S-ZrO2 (98,6 % de conversão). Na etanólise, a conversão foi de 92 %. Os desempenhos da zircônia sulfatada (S-ZrO2) e de um catalisador comercial à base de nióbio (ácido niobídico suportado em grafite) foram comparados na esterificação de ácido oléico com metanol e na transesterificação do óleo de soja. Tanto a zircônia sulfatada quanto o catalisador à base de nióbio converteram o ácido oléico em oleato de metila, porém o catalisador comercial não foi ativo na transesterificação do óleo de soja. A espectroscopia de ressonância magnética nuclear foi utilizada na determinação da composição em ácidos graxos dos ésteres e na quantificação das conversões de todas as reações de transesterificação. / Abstract: In this work it were synthesized methyl ester from soybean oil, canola oil, corn oil, andiroba oil and used frying oil. It was determined their fatty acid composition, kinematic viscosity and specific mass. The temperature dependent methyl fatty esters behavior was evaluated by means of Differential Scanning Calorimetric (DSC). In the base-catalyzed ethanolysis it were used sodium and potassium hydroxides and sodium methoxide as catalysts. The vegetable oil used were soybean oil and used frying oil. Strategies were studied for ethyl esters isolation. The catalyst performances were similar and the ethyl ester conversions reached values higher than 92 % and 98 % in the reactions carried out at 70 and 25 °C, respectively. Additionally, in the transesterefication carried out at room temperature it has occurred the glycerol spontaneous decantation. By studying the heterogeneous acid-catalyzed soybean oil transesterefication, the sulfated zirconia (S-ZrO2) prepared by a free-solvent route, the conventional sulfated zirconia (SZ) and the zirconium oxide (ZrO2) were utilized as catalysts. The best result was achieved at 120 °C during 1 h. Catalyst ZrO2 was not active in the transesterefication of soybean oil. The conventional sulfated zirconia presented only a very low activity (conversion of 8,5 %), while the S-ZrO2 had a very high performance ¿ 98,6 % methyl ester conversion. NMR was used for the determination of the fatty acid composition and all reaction conversions. / Mestrado / Quimica Inorganica / Mestre em Química

Human glutathione synthetase (hGS) is a homodimeric enzymes that catalyzes the second step in the biological synthesis of glutathione, a critical cellular antioxidant. The enzyme exhibits negative cooperativity towards the γ-glutamylcysteine (γ-GC) substrate. In this type of allosteric regulation, the binding of γ-GC at one active site significantly reduces substrate affinity at a second active site over 40 Å away. The presented work explores protein-protein interactions, substrate binding, and allosteric communication through investigation of three regions of hGS: the dimer interface, the S-loop, and the E-loop. Strong electrostatic interactions across the dimer interface of hGS maintain the appropriate tertiary and quaternary enzymatic structure needed for activity. The S-loop and E-loop of hGS form walls of the active site near γ-GC, with some residues serving to bind and position the negatively cooperative substrate. These strong interactions in the active site serve as a trigger for allosteric communication, which then passes through hydrophobic interactions at the interface. A comprehensive computational and experimental approach relates hGS structure with activity and regulation. ATP-grasp enzymes, including hGS, utilize ATP in the nucleophilic attack of a carboxylic acid in a reaction thought to proceed through the formation of an acylphosphate intermediate. Small metal cations are known to chelate the terminal phosphates of actives site ATP, yet the role of these atoms remains unclear. In the presented work, a computational metal substitution study establishes the role these divalent cations in the catalysis of peptide bonds. The simple model is used to determine the impact of metal cations on the thermodynamics and kinetics, an important stepping stone in understanding the importance of metal cations in larger biological systems.

Modern organic synthesis typically centers around the use of expensive, complex, homogeneous catalyst systems in organic solvents which often generate copious amounts of hazardous waste. Therefore, the development of water-tolerant catalysts capable of performing reactions in aqueous solutions has become a growing area of scientific inquiry. To this end, we have designed and optimized a water-stable catalyst (Mn[TMPyP4]I5) capable of generating aziridines from olefins in aqueous solutions. Aziridines are valuable synthetic building blocks that have been used to generate various biologically active compounds, though synthetic techniques for aziridine synthesis are not well-established. Our ultimate goal was developing a catalytic system, which could be paired with DNA in order to perform asymmetric transformation in aqueous solutions. Herein we report the optimization of reaction conditions using Mn[TMPyP4]I5 paired with various DNA types, in the hopes of generating chiral aziridines from several olefinic substrates.

Single atom catalysis is a relatively new form of heterogeneous catalysis. While single atom catalysts probably are already used in a lot of catalysis, their identification and characterization has only recently become common place. As we now have the ability to synthesis relatively pure systems consisting of single atoms and then to characterize them, there are many interesting questions that we can answer about them. In this work we will use a combination of several different types of characterizations such as kinetic measurements, diffuse reflectance infrared Fourier transform spectroscopy, extended x-ray absorption fine structure, and many more to better understand how single atoms react and how we can attempt to make such systems more active. The work here is primarily based around Ir single atoms and/or small clusters on three different supports MgAl2O4, TiO2, and CeO2. In each of these cases we attempt to understand how the Ir and the support catalytically oxidize CO into CO2 through a kinetic, and if possible, mechanistic study. Through these mechanistic studies we attempt to isolate the most important parameters of the catalyst so that we can create a more active catalyst. There are, of course, many different ways that we can use this information. The most obvious is by changing the catalyst support, but as the breadth of the research presented here will show, we can also optimize catalytic activity through using mixtures of single atoms with larger species as well as by changing the nuclearity of the said species, i.e., we can increase activity by controlling the size of the catalysts. However, in order to be able to control the activity in this way, we must 1) know how the size affects the activity and 2) know how the reaction conditions affect the size, i.e., we must establish the catalyst size is stable during reaction. Each of these topics are discussed to some extent here. Additionally, we also discuss how different sites of single atoms on the same support might differ and we show that we can create such different sites. On the whole, we have studied single atom and small cluster catalysis in many different directions based on systems of Ir for CO oxidation. This work is also performed with the intent to compare these Ir systems to similar systems of Rh, Pt, Pd, etc. However here we will only discuss the Ir pieces. / Doctor of Philosophy / In this work we study various properties of Ir single atom and subnanometer cluster catalysts for CO oxidation in hopes that we might be able to design a better catalyst with this information. A catalyst is a substance that facilitates a chemical reaction but is not consumed. For this work we will be considering the reaction of carbon monoxide (CO), which is a common pollutant and highly toxic gas, with O2 to create CO2, a much less dangerous pollutant. Our catalyst thus makes this reaction happen much faster and thus allows us to remove CO from exhaust streams, such as car exhaust, better. A single atom catalyst is a catalyst that is primarily a single atom on a metal oxide support. A subnanometer cluster catalyst is thus a catalyst that is smaller than one nanometer (0.00000004 inches). These are typically 10-20 atoms grouped together. This size is interesting as it is bigger than a single atom, but it is still much smaller than a classical catalyst nanoparticle and is thus controlled or dominated by different properties. In this work we will look at how different characteristics of the singe atom and cluster catalysts affect how good of a catalyst it is. The first is how the amount of single atoms and nanoparticles affect the overall activity of the catalyst. This study will tell us what the best mixture of single atoms is. The second study is how small clusters of Ir/MgAl2O4 react differently than single atoms and large nanoparticles. This tells us what the best size for Ir/MgAl2O4 catalysts are. The third study tells us how Ir/TiO2 single atom catalysts react which is useful when compared to Ir/MgAl2O4 and Ir/CeO2 (Chapter 7). The combination of single atom studies then allows us to make predictions on which supports (apart from Ir/MgAl2O4, Ir/TiO2, and Ir/CeO2) will be the best for CO oxidation. The fourth study compares different single atoms (all of Ir/TiO2) and shows how they behave differently, this is another possibility to increase the effectiveness of the catalyst. The fifth study discusses how different conditions affect the size of the Ir/TiO2 catalysts. Specifically, whether they exist as single atoms, subnanometer clusters, or larger clusters. All of these different studies represent another way that we can potentially increase catalytic activity and hopefully will allow our group, or another group to create even more active catalysts.

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