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Electrocatalysis of ethanol oxidation on Pt monolayers deposited on carbon-supported Ru and Rh nanoparticles

LIMA, F. H. B.; GONZALEZ, E. R.
Fonte: ELSEVIER SCIENCE BV Publicador: ELSEVIER SCIENCE BV
Tipo: Artigo de Revista Científica
ENG
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Pt monolayers deposited on carbon- supported Ru and Rh nanoparticles were investigated as electrocatalysts for ethanol oxidation. Electronic features of the Pt monolayers were studied by in situ XANES (X-ray absorption near-edge structure). The electrochemical activity was investigated by cyclic voltammetry and cronoamperometric experiments. Spectroscopic and electrochemical results were compared to those obtained on carbon-supported Pt-Ru and Pt-Rh alloys, and Pt E-TEK. XAS results indicate a modification of the Pt 5d band due to geometric and electronic interactions with the Ru ant Rh substrates, but the effect of withdrawing electrons from Pt is less pronounced in relation to that for the corresponding alloys. Electrochemical stripping of adsorbed CO, which is one of the intermediates, and the currents for the oxidation of ethanol show faster kinetics on the Pt monolayer deposited on Ru nanoparticles, and an activity that exceeds that of conventional catalysts with much larger amounts of platinum. (c) 2007 Elsevier B.V. All rights reserved.

Synthesis of supported metal nanoparticle catalysts using ligand assisted methods

Costa, Natália J. S.; Rossi, Liane M.
Fonte: ROYAL SOC CHEMISTRY; CAMBRIDGE Publicador: ROYAL SOC CHEMISTRY; CAMBRIDGE
Tipo: Artigo de Revista Científica
ENG
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The synthesis and characterization methods of metal nanoparticles (NPs) have advanced greatly in the last few decades, allowing an increasing understanding of structure-property-performance relationships. However, the role played by the ligands used as stabilizers for metal NPs synthesis or for NPs immobilization on solid supports has been underestimated. Here, we highlight some recent progress in the preparation of supported metal NPs with the assistance of ligands in solution or grafted on solid supports, a modified deposition-reduction method, with special attention to the effects on NPs size, metal-support interactions and, more importantly, catalytic activities. After presenting the general strategies in metal NP synthesis assisted by ligands grafted on solid supports, we highlight some recent progress in the deposition of pre-formed colloidal NPs on functionalized solids. Another important aspect that will be reviewed is related to the separation and recovery of NPs. Finally, we will outline our personal understanding and perspectives on the use of supported metal NPs prepared through ligand-assisted methods.; FAPESP; CAPES; CNPq; INCT-Catalise

Oxidação alílica de alcenos catalisada por nanopartículas de óxido de cobalto suportadas; Allylic oxidation of alkenes catalyzed by supported cobalt oxide nanoparticles.

Silva, Fernanda Parra da
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 31/03/2011 PT
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Este trabalho compreende a síntese e caracterização de um novo catalisador magneticamente recuperável de CoO para oxidação alílica de alcenos. O catalisador foi preparado através da deposição de nanopartículas (de tamanho entre 2-3 nm) do metal cataliticamente ativo em nanopartículas de magnetita revestidas por sílica. A natureza magnética do suporte permitiu a fácil separação do catalisador do meio reacional após o termino das reações pela simples aproximação de um ímã na parede do reator. O catalisador pôde ser completamente separado da fase líquida, fazendo com que a utilização de outros métodos de separação como filtração e centrifugação, comumente utilizados em sistemas heterogêneos líquidos, fossem completamente dispensados. O catalisador foi inicialmente testado em reações de oxidação do substrato modelo cicloexeno e mostrou seletividade para a produção do produto alílico, cicloex-2-en-1-ona, que é reagente de partida de grande interesse para a síntese de diversos materiais na indústria química. As reações de oxidação foram realizadas utilizando-se apenas O2 como oxidante primário, dispensando o uso de oxidantes tóxicos como cromatos ou permanganatos, que não são recomendados do ponto de vista ambiental. O catalisador sintetizado mostrou ser reutilizável em sucessivos ciclos de oxidação...

Catálise assimétrica no Brasil : desenvolvimento e potencialidades para o avanço da indústria química brasileira; Asymmetric catalysis in Brazil : development and potential for advancement of brazilian chemical industry

Braga, Antonio Luiz; Lüdtke, Diogo Seibert; Schneider, Paulo Henrique; Andrade, Leandro Helgueira de; Paixão, Marcio W.
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Artigo de Revista Científica Formato: application/pdf
POR
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The preparation of enantiomerically pure or enriched substances is of fundamental importance to pharmaceutical, food, agrochemical, and cosmetics industries and involves a growing market of hundreds of billions of dollars. However, most chemical processes used for their production are not environmentally friendly because in most cases, stoichiometric amounts of chiral inductors are used and substantial waste is produced. In this context, asymmetric catalysis has emerged as an efficient tool for the synthesis of enantiomerically enriched compounds using chiral catalysts. More specifically, considering the current scenario in the Brazilian chemical industry, especially that of pharmaceuticals, the immediate prospect for the use of synthetic routes developed in Brazil in an enantioselective fashion or even the discovery of new drugs is practically null. Currently, the industrial production of drugs in Brazil is primarily focused on the production of generic drugs and is basically supported by imports of intermediates from China and India. In order to change this panorama and move forward toward the gradual incorporation of genuinely Brazilian synthetic routes, strong incentive policies, especially those related to continuous funding...

Solvent free esterification reactions using Lewis acids in solid phase catalysis

Barbosa, Sandro L.; Dabdoub, Miguel J.; Hurtado, Gabriela R.; Klein, Stanlei I.; Baroni, Adriano C. M.; Cunha, Christielle
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 146-150
ENG
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A clean, efficient and fast method for esterification reactions for sterically (biodiesels) or otherwise inactive (aromatic) precursors was developed, using catalysts supported in a solid phase under solvent free conditions, and whose reactions can be promoted by MW irradiation. (c) 2006 Elsevier B.V. All rights reserved.

Estudo das propriedades físico-químicas de sistemas Pd, Pd-Fe e Pd-Co suportados em CeO2/Al2O3; Study of the physico-chemical properties of the Pd, Pd-Fe and Pd-Co systems supported at CeO2/Al2O3

Eleonora Maria Pereira de Luna Freire
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 2005/08/3 PT
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Os catalisadores à base de paládio apresentam particular interesse para o tratamento de gases de exaustão automotiva, notadamente no caso da combustão do etanol. O presente trabalho tem o objetivo de estudar as propriedades físico- químicas de catalisadores Pd - Fe e Pd - Co suportados em alumina modificada pelo óxido de cério. Para tanto, catalisadores modelo foram preparados através do método de impregnação por via úmida, empregando-se sais precursores à base de nitrato dos metais, e os suportes Al2O3, CeO2 e CeO2/Al2O3. Os catalisadores obtidos tiveram seus teores metálicos determinados por meio de espectrofotometria de absorção atômica, tendo sido caracterizados através de adsorção de nitrogênio (método B.E.T), espectroscopia no infravermelho, difração de raio-X, redução à temperatura programada. Os sistemas preparados foram avaliados pela reação catalítica de oxidação do etanol em fase gasosa em um microreator tubular de leito fixo, operando a pressão atmosférica e a temperatura de 3500 C. Os catalisadores preparados apresentam frações mássicas em torno de 2 % para o Pd, e de 1% para os aditivos Fe ou Co. A adição de Pd, Pd-Fe e Pd-Co aos suportes Al2O3 e CeO2/Al2O3 não levou a modificações...

Avaliação da produção de hidrogênio a partir de catalisadores suportados em alumina; Assessment of hydrogen production from catalysts supported on alumina

Éder Valdir de Oliveira
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 20/02/2015 PT
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A produção de hidrogênio através de glicerol apresenta ser uma maneira sustentável e economicamente viável, visto que há um excesso de glicerol no mercado, o que reduz seu valor consideravelmente, de modo que, a produção de hidrogênio se torne bastante viável. Mediante este fato, torna-se necessário e urgente o desenvolvimento do processo de produção de hidrogênio. Nesse contexto, o presente trabalho tem por objetivo estudar a produção de hidrogênio através do processo de reforma aquosa do glicerol avaliando a utilização de dois suportes de alumina distintos pela fase, α-alumina e γ-alumina com ambos os suportes preparados com 5 % de concentração de metais ativos preparados por impregnação via-úmida favorecendo a troca iônica pelo ajuste de pH, de acordo com o ponto isoelétrico de cada suporte. O principal metal ativo utilizado é a platina, conforme recomendado pela literatura. Foram também avaliados catalisadores bimetálicos, com a substituição de 1 % de platina por ródio. Os catalisadores foram avaliados pela determinação da área superficial, volume de poros e diâmetro dos poros por meio da adsorção de N2 (método B.E.T). Outro método utilizado para avaliar os catalisadores foi a difração de raios-X...

Towards an atomic level understanding of niobia based catalysts and catalysis by combining the science of catalysis with surface science

Schmal,Martin; Freund,Hans-Joachim
Fonte: Academia Brasileira de Ciências Publicador: Academia Brasileira de Ciências
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2009 EN
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The science of catalysis and surface science have developed, independently, key information for understanding catalytic processes. One might argue: is there anything fundamental to be discovered through the interplay between catalysis and surface science? Real catalysts of monometallic and bimetallic Co/Nb2O5 and Pd-Co/Nb2O5 catalysts showed interesting selectivity results on the Fischer-Tropsch synthesis (Noronha et al. 1996, Rosenir et al. 1993). The presence of a noble metal increased the C+5 selectivity and decreased the methane formation depending of the reduction temperature. Model catalyst of Co-Pd supported on niobia and alumina were prepared and characterized at the atomic level, thus forming the basis for a comparison with "real" support materials. Growth, morphology and structure of both pure metal and alloy particles were studied. It is possible to support the strong metal support interaction suggested by studies on real catalysts via the investigation of model systems for niobia in comparison to alumina support in which this effect does not occur. Formation of Co2+ penetration into the niobia lattice was suggested on the basis of powder studies and can be fully supported on the basis of model studies. It is shown for both real catalysts and model systems that oxidation state of Co plays a key role in controlling the reactivity in Fischer-Tropsch reactions systems and that the addition of Pd is a determining factor for the stability of the catalyst. It is demonstrated that the interaction with unsaturated hydrocarbons depends strongly on the state of oxidation.

Isoporphyrin Intermediate in Heme Oxygenase Catalysis: OXIDATION OF α-MESO-PHENYLHEME*S⃞

Evans, John P.; Niemevz, Fernando; Buldain, Graciela; de Montellano, Paul Ortiz
Fonte: American Society for Biochemistry and Molecular Biology Publicador: American Society for Biochemistry and Molecular Biology
Tipo: Artigo de Revista Científica
Publicado em 11/07/2008 EN
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Human heme oxygenase-1 (hHO-1) catalyzes the O2- and NADPH-dependent oxidation of heme to biliverdin, CO, and free iron. The first step involves regiospecific insertion of an oxygen atom at the α-meso carbon by a ferric hydroperoxide and is predicted to proceed via an isoporphyrin π-cation intermediate. Here we report spectroscopic detection of a transient intermediate during oxidation by hHO-1 of α-meso-phenylheme-IX, α-meso-(p-methylphenyl)-mesoheme-III, and α-meso-(p-trifluoromethylphenyl)-mesoheme-III. In agreement with previous experiments (Wang, J., Niemevz, F., Lad, L., Huang, L., Alvarez, D. E., Buldain, G., Poulos, T. L., and Ortiz de Montellano, P. R. (2004) J. Biol. Chem. 279, 42593–42604), only the α-biliverdin isomer is produced with concomitant formation of the corresponding benzoic acid. The transient intermediate observed in the NADPH-P450 reductase-catalyzed reaction accumulated when the reaction was supported by H2O2 and exhibited the absorption maxima at 435 and 930 nm characteristic of an isoporphyrin. Product analysis by reversed phase high performance liquid chromatography and liquid chromatography electrospray ionization mass spectrometry of the product generated with H2O2 identified it as an isoporphyrin that...

Solvothermal Synthesis and Supported Catalysis of Polyanion-derived Metal Oxide Nanoparticles

Soultanidis, Nikolaos
Fonte: Universidade Rice Publicador: Universidade Rice
ENG
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Supported metal oxides (SMOs) are important catalytic materials that find numerous applications in important industrial processes. Improving the structural properties of SMOs is a challenging objective due to material synthesis and characterization limitations. Recent developments in the characterization of SMOs, specifically tungstated zirconia (WO x /ZrO 2 ), have revealed structural information that renewed scientific interest in developing more sophisticated synthetic protocols for SMOs. The current work aims to provide a robust characterization of WO x /ZrO 2 by using different characterization techniques and probe reactions. Conventional and non-conventional synthetic methods are investigated to cover the whole spectrum of published methods in order to understand the properties and limitations of these techniques. In the second part of this work, a new synthetic approach is presented that successfully produces ultrasmall (smaller than 2 nm) tungsten oxide nanoparticles (WO x NPs). By using conventional tungsten precursors and oleylamine, WO x NPs are synthesized, characterized, and finally supported to test their propene metathesis activity. Conventional WO x /ZrO 2 catalysts were prepared and extensively studied by probing their n -pentane isomerization activity and methanol dehydration activity. WO x /ZrO 2 prepared via incipient wetness impregnation shows maximum n -pentane isomerization turnover rates ( TOR ) at intermediate surface densities ( � surf ). This method delivers the most active n -pentane isomerization WO x /ZrO 2 catalysts since it maximizes the number density of the active sub-nm slightly distorted Zr-WO x sites at � surf between 5.2-6.2 W/nm 2 . By comparing the n -pentane isomerization activity with the methanol dehydration activity of WO x /ZrO 2 ...

Synthesis and evaluation of chiral phosphine and NHC-Ligands or heterogeneous asymmetric catalysis

Marques, Carolina Silva
Fonte: Universidade de Évora Publicador: Universidade de Évora
Tipo: Tese de Doutorado
ENG
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No âmbito deste trabalho, foram estudadas as reacções de arilação catalítica assimétrica em vários substratos, utilizando novos e já conhecidos catalisadores quirais, possuindo metais de transição. Esta metodologia levou à formação de novas ligações C-C, fornecendo uma panóplia de interessantes compostos, podendo-se revelar intermediários extremamente úteis na síntese de compostos biologicamente activos. Deve-se salientar a síntese de aminas quirais, α-hidroxiésteres, α-amino-ácidos e α-aminoésteres e também bi-arildiarilaminas, utilizando catalisadores de metais de transição, baseados em Pd, Rh e Ru. Reagentes organoboronados foram aplicados com sucesso neste estudo. Uma nova família de carbenos N-heterocíclicos (NHCs) foi obtida com bons rendimentos e aplicada, com sucesso, nas reacções catalíticas acima referidas. Um novo método de catálise homogénea sequencial (arilação/Suzuki-Miyaura) foi desenvolvido na síntese de bi-arilarilmetilaminas. Este método foi transformado eficientemente numa versão heterogénea utilizando Catálise com uma Fase líquida Iónica Suportada (SILPC), aplicado pela primeira vez neste tipo de catálise sequencial; ABSTRACT: The study of catalytic asymmetric arylations of appropriate substrates...

Organically Modified Mesoporous Silica as a Support for Synthesis and Catalysis

McEleney, Kevin
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado Formato: 14165145 bytes; application/pdf
EN; EN
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Mesoporous silicates are excellent materials for supported catalysis due to their ease of functionalization, tunable pore size and high surface areas. Mesoporous silicates have been utilized in a variety of applications such as drug delivery scaffolds and catalyst supports. Functionalization of the surface can be achieved by either grafting of alkoxy silanes or co-condensation of the organosilane with the inorganic silica source. My research in this area can be divided into two components. In the first, we address the significant issue of metal contamination after reactions that are catalyzed by transition metals. In the second, we examine the design of new catalysts based on organic/inorganic composites. Ruthenium catalyzed processes such as olefin metathesis or asymmetric hydrogenation, are often underutilized due to the difficulty of removing the ruthenium by-products. Attempts to remove ruthenium involve treating the solution with a scavenging reagent followed by silica chromatography. Often these scavenging agents are expensive phosphines or toxic agents like lead tetra-acetate. SBA-15 functionalized with aminopropyl triethoxysilane displays a high affinity for ruthenium. Furthermore, it can be utilized to remove ruthenium by-products from olefin metathesis or hydrogenation reactions without the need for silica chromatography. We have also prepared sulfur-functionalized mesoporous silicates that have a high affinity for palladium. The materials after loading prove to be active catalysts for a variety of palladium catalyzed processes such as Suzuki-Miyaura and Sonogashira couplings. The catalysts are recyclable with moderate loss of activity and structure...

Síntese de nanopartículas metálicas suportadas em sílicas mesoporosas organofuncionalizadas; Synthesis of metal nanoparticles supported in organofunctionalized mesoporous silica

Natália Fattori
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 11/11/2014 PT
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O presente trabalho descreve um método de preparação de nanopartículas metálicas suportadas em sílicas mesoporosas organofuncionalizadas. Dois diferentes substratos foram explorados: uma sílica mesoporosa constituída de uma estrutura porosa altamente ordenada e uniforme, composta de poros ou canais cilíndricos dispostos paralelamente e empacotados em arranjo hexagonal (SBA-15), e uma sílica mesoporosa caracterizada por uma rede desordenada de poros, de tamanho e forma variados, distribuídos e interconectados aleatoriamente ao longo da estrutura porosa (SMD). As duas matrizes tiveram suas superfícies quimicamente modificadas com dois diferentes agentes funcionalizantes constituídos de cátions orgânicos (R+Cl-) com propriedades de troca-iônica, derivados das moléculas 1-metilimidazol (Imi) e 4,4'-bipiridina (Bipy). Em ambos os casos, as propriedades íontrocadoras dos cátions orgânicos ancorados na superfície das sílicas permitem a retenção de ânions complexos de metais nobres ([AuCl4]-, [PtCl6]2- e [PdCl4]2-) confinados na estrutura porosa. Estas espécies foram convertidas in situ nas nanopartículas metálicas de interesse pela redução dos íons metálicos com agentes redutores adequados. As matrizes modificadas com o grupo funcional Imi foram utilizadas como suportes para a preparação e estabilização de nanopartículas metálicas (Au...

C-H Amination Catalysis from High-Spin Ferrous Complexes

Hennessy, Elisabeth Therese
Fonte: Harvard University Publicador: Harvard University
Tipo: Thesis or Dissertation
EN_US
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The C-H amination and olefin aziridination chemistry of iron supported by dipyrromethene ligands (RLAr, L=1,9-R2-5-aryldipyrromethene, R = Mes, 2,4,6-Ph3C6H2, tBu, Ad, 10-camphoryl, Ar = Mes, 2,4,6-Cl3C6H2) was explored. The weak-field, pyrrole-based dipyrrinato ligand was designed to generate an electrophilic, high-spin metal center capable of accessing high valent reactive intermediates in the presence of organic azides. Isolation of the reactive intermediate in combination with a series of mechanistic experiments suggest the N-group transfer chemistry proceeds through a rapid, single-electron pathway and maintains an overall S=2 electronic configuration throughout the catalytic cycle. We have established the catalysts' strong preference for allylic amination over aziridination with olefin containing substrates. Aziridination is limited to styrenyl substrates without allylic C-H bonds, while allylic amination has been demonstrated with both cyclic and linear aliphatic alkenes. Notably, the functionalization of &alpha-olefins to linear allylic amines occurs with outstanding regioselectivity.; Chemistry and Chemical Biology

Characterization of Graphite-Supported Palladium-Cobalt Catalysts by Temperature-Programmed Reduction and Magnetic Measurements

Noronha, Fábio Bellot; Schmal, Martin; Nicot, C.; Moraweck, B.; Fréty, R.
Fonte: Instituto Nacional de Tecnologia Publicador: Instituto Nacional de Tecnologia
Tipo: Artigo de Revista Científica
EN
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Journal of catalysis, 168(1): 42-50, Maio 1997.; Graphite-supported cobalt, palladium, and cobalt-palladium systems were prepared by a simple impregnation technique and submitted to hydrogen reduction in a temperature-programmed mode. Using X-ray diffraction to define the structure of the calcined precursors, magnetic measurements to determine the amount of metallic cobalt formed after reduction, and analysis of the gaseous medium during the reduction, a general model for the reduction of the graphite supported catalysts has been suggested. At room temperature, both pure Pd~ and Pd~ associated with C0304 are reduced to the metallic state. In the case of bimetallic systems, a fraction of C0304 in close proximity or interfaced with Pd~ can be reduced to the metallic state and to CoO species, demonstrating a strong catalytic effect of palladium on the reduction of cobalt oxides. At temperatures between 298 and 500 K, depending on the catalyst formulation, the presence of metallic palladium promotes the reduction of a large fraction of oxidized cobalt. At higher reduction temperature, at least two competitive phenomena were detected: direct reduction of the residual oxidized cobalt by the graphite, leading to carbon monoxide and dioxide formation...

Selective hydrogenation of dimethyl adipate on titania-supported RuSn catalysts.

Silva, Adriana Maria da; Morales, Marco A; Baggio-Saitovitch, Elisa M; Jordão, Elisabete; Fraga, Marco André
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
EN
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Applied Catalysis A: General, 353(2009):101-106; The hydrogenation of dimethyl adipate over RuSn catalysis was studied to examine the effect of tin species and titania on selective production of 1,6-hexanediol.

Supported Ionic-Liquid Films (SILF) as Two-Dimensional Nanoreactors for Enantioselective Reactions: Surface-Mediated Selectivity Modulation (SMSM)

Castillo, María R.; Fousse, Leslie; Fraile, José M.; García, José I.; Mayoral, José A.
Fonte: Wiley-VCH Publicador: Wiley-VCH
Tipo: Artículo Formato: 13824 bytes; application/vnd.ms-excel
ENG
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5 pages, 3 figures, 3 tables, 2 scheme.; Supported ionic-liquid films (SILF) of nanometric thickness containing bis(oxazoline)-copper complexes can be used as recoverable catalysts for enantioselective cyclopropanation reactions. When a thin film of ionic liquid is supported on a clay, the system behaves as a nearly two-dimensional nanoreactor in which the restrictions in rotational mobility and the close proximity to the surface support produce variations in the stereo- and enantioselectivities, leading to a complete reversal of the overall selectivity of the reaction. As an example, the cyclopropanation of styrene changes from a preference for the (1S,2S)-trans isomer in bulk solution to the (1R,2S)-cis isomer in the SILF. This variation is strongly dependent on both the thickness of the film and the nature of the support. Only layered solids with negative charges in the layers (clays) give rise to this type of behaviour, showing that the formation of ion pairs may be a decisive factor. This unexpected effect also shows the existence of differences between bulk and supported ionic liquids.; This work was made possible by the generous financial support of the CICYT(pro ject CTQ2005-08016 and CSD2006-0003). M.R.C. is indebted to DGA for a grant.; Peer reviewed

Turning cucurbit[8]uril into a supramolecular nanoreactor for asymmetric catalysis

Zheng, Lifei; Sonzini, Silvia; Ambarwati, Masyitha; Rosta, Edina; Scherman, Oren A.; Herrmann, Andreas
Fonte: Wiley Publicador: Wiley
Tipo: Article; published version
EN
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This is the final version of the article. It first appeared from Wiley via http://dx.doi.org/10.1002/anie.201505628; Chiral macromolecules have been widely used as synthetic pockets to mimic natural enzymes and promote asymmetric reactions. An achiral host, cucurbit[8]uril (CB[8]), was used for an asymmetric Lewis acid catalyzed Diels?Alder reaction. We achieved a remarkable increase in enantioselectivity and a large rate acceleration in the presence of the nanoreactor by using an amino acid as the chiral source. Mechanistic and computational studies revealed that both the amino acid?Cu2+ complex and the dienophile substrate are included inside the macrocyclic host cavity, suggesting that contiguity and conformational constraints are fundamental to the catalytic process and rate enhancement. These results pave the way towards new studies on asymmetric reactions catalyzed in confined achiral cavities.; This research was supported by the European Union (European Research Council Starting GrantsASPiRe 240629 (OAS) and NUCLEOPOLY240080 (AH) and STREP project MICREAGENTS), the Netherlands Organization for Scientific Research (NWO-Vici Grant) and the Zernike Institute for Advanced Materials. E R. acknowledges computational support from the NIH Biowulf cluster...

Raw data for ACIE manuscript "Turning Cucurbit[8]uril into a Supramolecular Nanoreactor for Asymmetric Catalysis"

Zheng, Lifei; Sonzini, Silvia; Ambarwati, Masyitha; Rosta, Edina; Scherman, Oren A.; Herrmann, Andreas
Fonte: Universidade de Cambridge Publicador: Universidade de Cambridge
Tipo: Relatório Formato: .txt, .csv, .odt
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These are all the raw data supporting both the results in the manuscript and in the supporting information. A list of abbreviations used in the files is given within the folder.; This work was supported by the EPSRC, NIH, European Research Council Starting GrantsASPiRe 240629 (OAS) and NUCLEOPOLY240080 (AH) and STREP (project MICREAGENTS), the Netherlands Organization for Scientific Research (NWO-Vici Grant) and the Zernike Institute for Advanced Materials.

Hydroformylation of oct-1-ene by supported aqueous phase catalysis: Influence of catalytic complex and preparation method of the supports

Jáuregui-Haza,U. J.; Wilhelm,A. M.; Delmas,H.
Fonte: Latin American applied research Publicador: Latin American applied research
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2002 EN
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Four silica samples were evaluated as supports in the hydroformylation of oct-1-ene by Supported Aqueous Phase Catalysis (SAPC) using [Rh2(µ-StBu)2(CO)2(TPPTS)2] and [Rh(COD)Cl]2/TPPTS as catalysts. Adsorption studies of the [Rh(COD)Cl]2/TPPTS complex from aqueous solutions on the supports were carried out at 25 °C. The isotherms obtained were correlated by several models, among which the Fowler-Guggenheim/Jovanovic-Freundlich equation was found to be the most satisfactory. The influence of the nature of catalytic complex and of the methods for supporting the catalyst on the silica conversion was also studied.