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Sample records for asymmetric catalysis solvent-free

  1. Prolinethiol ether catalysis in an asymmetric Michael reaction: solvent-free synthesis of functionalized monohaloalkenes.

    Science.gov (United States)

    Xia, Ai-Bao; Wu, Chao; Xu, Dan-Qian; Wang, Yi-Feng; Du, Xiao-Hua; Li, Zhao-Bo; Xu, Zhen-Yuan

    2013-02-01

    The organocatalytic Michael reaction of ketones with γ-monohalonitrodienes catalyzed by chiral prolinethiol ether under solvent-free conditions was developed. The described method represents a novel approach for accessing highly functionalized monohaloalkenes with α, β-stereocenters of up to >99% ee.

  2. Multicatalyst system in asymmetric catalysis

    CERN Document Server

    Zhou, Jian

    2014-01-01

    This book introduces multi-catalyst systems by describing their mechanism and advantages in asymmetric catalysis.  Helps organic chemists perform more efficient catalysis with step-by-step methods  Overviews new concepts and progress for greener and economic catalytic reactions  Covers topics of interest in asymmetric catalysis including bifunctional catalysis, cooperative catalysis, multimetallic catalysis, and novel tandem reactions   Has applications for pharmaceuticals, agrochemicals, materials, and flavour and fragrance

  3. Asymmetric cation-binding catalysis

    DEFF Research Database (Denmark)

    Oliveira, Maria Teresa; Lee, Jiwoong

    2017-01-01

    The employment of metal salts is quite limited in asymmetric catalysis, although it would provide an additional arsenal of safe and inexpensive reagents to create molecular functions with high optical purity. Cation chelation by polyethers increases the salts' solubility in conventional organic...... solvents, thus increasing their applicability in synthesis. The expansion of this concept to chiral polyethers led to the emergence of asymmetric cation-binding catalysis, where chiral counter anions are generated from metal salts, particularly using BINOL-based polyethers. Alkali metal salts, namely KF...... and KCN, are selectively bound to the catalyst, providing exceptionally high enantioselectivities for kinetic resolutions, elimination reactions (fluoride base), and Strecker synthesis (cyanide nucleophile). Asymmetric cation-binding catalysis was recently expanded to silicon-based reagents, enabling...

  4. Asymmetric Ion-Pairing Catalysis

    Science.gov (United States)

    Brak, Katrien

    2014-01-01

    Charged intermediates and reagents are ubiquitous in organic transformations. The interaction of these ionic species with chiral neutral, anionic, or cationic small molecules has emerged as a powerful strategy for catalytic, enantioselective synthesis. This review describes developments in the burgeoning field of asymmetric ion-pairing catalysis with an emphasis on the insights that have been gleaned into the structural and mechanistic features that contribute to high asymmetric induction. PMID:23192886

  5. Solvent-free heterogeneous catalysis for cyanosilylation in a dynamic cobalt-MOF.

    Science.gov (United States)

    Cui, Xin; Xu, Mei-Chen; Zhang, Ling-Juan; Yao, Ru-Xin; Zhang, Xian-Ming

    2015-07-28

    The butterfly-like tetranuclear cobalt cluster based 3D MOF [Me2NH2][Co2(bptc)(μ3-OH)(H2O)2] (1) underwent a reversible thermally triggered single-crystal-to-single-crystal transformation via Co-Owater weakened intermediate 1a to produce a partly dehydrated phase [Me2NH2][Co2(bptc)(μ3-OH)(H2O)] (2), which was confirmed by single-crystal X-ray diffraction, powder X-ray diffraction, thermogravimetric analysis, and IR spectroscopy. During the dehydration course, the local coordination environment of one Co(2+) ion was changed from the saturated octahedron to a coordinately unsaturated square-pyramid, accompanied by a crystal color change from red to purple. Compared with pristine hydrated 1, dehydrated 2 exhibits highly efficient and recyclable catalytic activity for cyanosilylation of carbonyl compounds with a low catalyst loading of 0.1 mol% Co at room temperature under solvent-free conditions, which due to the open Co(2+) sites as catalytically activated sites played a significant role in the heterogeneous catalytic process.

  6. Asymmetric trienamine catalysis: new opportunities in amine catalysis.

    Science.gov (United States)

    Kumar, Indresh; Ramaraju, Panduga; Mir, Nisar A

    2013-02-07

    Amine catalysis, through HOMO-activating enamine and LUMO-activating iminium-ion formation, is receiving increasing attention among other organocatalytic strategies, for the activation of unmodified carbonyl compounds. Particularly, the HOMO-raising activation concept has been applied to the greatest number of asymmetric transformations through enamine, dienamine, and SOMO-activation strategies. Recently, trienamine catalysis, an extension of amine catalysis, has emerged as a powerful tool for synthetic chemists with a novel activation strategy for polyenals/polyenones. In this review article, we discuss the initial developments of trienamine catalysis for highly asymmetric Diels-Alder reactions with different dienophiles and emerging opportunities for other types of cycloadditions and cascade reactions.

  7. Chiral fullerenes from asymmetric catalysis.

    Science.gov (United States)

    Maroto, Enrique E; Izquierdo, Marta; Reboredo, Silvia; Marco-Martínez, Juan; Filippone, Salvatore; Martín, Nazario

    2014-08-19

    Fullerenes are among the most studied molecules during the last three decades, and therefore, a huge number of chemical reactions have been tested on these new carbon allotropes. However, the aim of most of the reactions carried out on fullerenes has been to afford chemically modified fullerenes that are soluble in organic solvents or even water in the search for different mechanical, optical, or electronic properties. Therefore, although a lot of effort has been devoted to the chemical functionalization of these molecular allotropes of carbon, important aspects in the chemistry of fullerenes have not been properly addressed. In particular, the synthesis of chiral fullerenes at will in an efficient manner using asymmetric catalysis has not been previously addressed in fullerene science. Thus, despite the fact that the chirality of fullerenes has always been considered a fundamental issue, the lack of a general stereoselective synthetic methodology has restricted the use of enantiopure fullerene derivatives, which have usually been obtained only after highly expensive HPLC isolation on specific chiral columns or prepared from a pool of chiral starting materials. In this Account, we describe the first stereodivergent catalytic enantioselective syntheses in fullerene science, which have allowed the highly efficient synthesis of enantiomerically pure derivatives with total control of the stereochemical result using metallic catalysts and/or organocatalysts under very mild conditions. Density functional theory calculations strongly support the experimental findings for the assignment of the absolute configuration of the new stereocenters, which has also been ascertained by application of the sector rule and single-crystal X-ray diffraction. The use of the curved double bond of fullerene cages as a two-π-electron component in a variety of stereoselective cycloaddition reactions represents a challenging goal considering that, in contrast to most of the substituted

  8. An efficient solvent-free synthesis of meso-substituted dipyrromethanes using SnCl2•2H2O catalysis

    Directory of Open Access Journals (Sweden)

    Kabeer Ahmed Shaikh

    2012-07-01

    Full Text Available Highly rapid and simple methodology has been developed for the quantitative synthesis of meso-substituted dipyrromethanes from lowest pyrrole/aldehyde ratio. The method was carried out by using SnCl2•2H2O as a catalyst under solvent free condition. The method is environmentally friendly, easy to workup, and gives excellent yield of the products.

  9. Asymmetric Aldol Additions: A Guided-Inquiry Laboratory Activity on Catalysis

    Science.gov (United States)

    King, Jorge H. Torres; Wang, Hong; Yezierski, Ellen J.

    2018-01-01

    Despite the importance of asymmetric catalysis in both the pharmaceutical and commodity chemicals industries, asymmetric catalysis is under-represented in undergraduate chemistry laboratory curricula. A novel guided-inquiry experiment based on the asymmetric aldol addition was developed. Students conduct lab work to compare the effectiveness of…

  10. Engineering homochiral metal-organic frameworks for heterogeneous asymmetric catalysis and enantioselective separation.

    Science.gov (United States)

    Liu, Yan; Xuan, Weimin; Cui, Yong

    2010-10-01

    Owing to the potential applications in technological areas such as gas storage, catalysis, separation, sensing and nonlinear optics, tremendous efforts have been devoted to the development of porous metal-organic frameworks (MOFs) over the past ten years. Homochiral porous MOFs are particularly attractive candidates as heterogeneous asymmetric catalysts and enantioselective adsorbents and separators for production of optically active organic compounds due to the lack of homochiral inorganic porous materials such as zeolites. In this review, we summarize the recent research progress in homochiral MOF materials, including their synthetic strategy, distinctive structural features and latest advances in asymmetric heterogeneous catalysis and enantioselective separation.

  11. Artificial Metalloenzymes for Asymmetric Catalysis by Creation of Novel Active Sites in Protein and DNA Scaffolds

    NARCIS (Netherlands)

    Drienovska, Ivana; Roelfes, Gerard

    Artificial metalloenzymes have emerged as a promising new approach to asymmetric catalysis. In our group, we are exploring novel artificial metalloenzyme designs involving creation of a new active site in a protein or DNA scaffold that does not have an existing binding pocket. In this review, we

  12. Asymmetric Anion-π Catalysis: Enamine Addition to Nitroolefins on π-Acidic Surfaces.

    Science.gov (United States)

    Zhao, Yingjie; Cotelle, Yoann; Avestro, Alyssa-Jennifer; Sakai, Naomi; Matile, Stefan

    2015-09-16

    Here we provide experimental evidence for anion-π catalysis of enamine chemistry and for asymmetric anion-π catalysis. A proline for enamine formation on one side and a glutamic acid for nitronate protonation on the other side are placed to make the enamine addition to nitroolefins occur on the aromatic surface of π-acidic naphthalenediimides. With increasing π acidity of the formally trifunctional catalysts, rate and enantioselectivity of the reaction increase. Mismatched and more flexible controls reveal that the importance of rigidified, precisely sculpted architectures increases with increasing π acidity as well. The absolute configuration of stereogenic sulfoxide acceptors at the edge of the π-acidic surface has a profound influence on asymmetric anion-π catalysis and, if perfectly matched, affords the highest enantio- and diastereoselectivity.

  13. Asymmetric catalysis at the mesoscale: gold nanoclusters embedded in chiral self-assembled monolayer as heterogeneous catalyst for asymmetric reactions.

    Science.gov (United States)

    Gross, Elad; Liu, Jack H; Alayoglu, Selim; Marcus, Matthew A; Fakra, Sirine C; Toste, F Dean; Somorjai, Gabor A

    2013-03-13

    Research to develop highly versatile, chiral, heterogeneous catalysts for asymmetric organic transformations, without quenching the catalytic reactivity, has met with limited success. While chiral supramolecular structures, connected by weak bonds, are highly active for homogeneous asymmetric catalysis, their application in heterogeneous catalysis is rare. In this work, asymmetric catalyst was prepared by encapsulating metallic nanoclusters in chiral self-assembled monolayer (SAM), immobilized on mesoporous SiO2 support. Using olefin cyclopropanation as an example, it was demonstrated that by controlling the SAM properties, asymmetric reactions can be catalyzed by Au clusters embedded in chiral SAM. Up to 50% enantioselectivity with high diastereoselectivity were obtained while employing Au nanoclusters coated with SAM peptides as heterogeneous catalyst for the formation of cyclopropane-containing products. Spectroscopic measurements correlated the improved enantioselectivity with the formation of a hydrogen-bonding network in the chiral SAM. These results demonstrate the synergetic effect of the catalytically active metallic sites and the surrounding chiral SAM for the formation of a mesoscale enantioselective catalyst.

  14. Allenes in Asymmetric Catalysis. Asymmetric Ring-Opening of Meso-Epoxides Catalyzed by Allene-Containing Phosphine Oxides

    Science.gov (United States)

    Pu, Xiaotao; Qi, Xiangbing; Ready, Joseph M.

    2009-01-01

    Unsymmetrically substituted allenes (1,2 dienes) are inherently chiral and can be prepared in optically pure form. Nonetheless, to date the allene framework has not been incorporated into ligands for asymmetric catalysis. Since allenes project functionality differently than either tetrahedral carbon or chiral biaryls, they may create complementary chiral environments. This study demonstrates that optically active C2 symmetric allene-containing bisphosphine oxides can catalyze the addition of SiCl4 to meso epoxides with high enantioselectivity. The epoxide-opening likely involves generation of a Lewis acidic, cationic (bisphosphine oxide)SiCl3 complex. The fact that high asymmetric induction is observed suggests that allenes may represent a new platform for the development of ligands and catalysts for asymmetric synthesis. PMID:19722613

  15. Novel Cinchona derived organocatalysts: new asymmetric transformations and catalysis

    NARCIS (Netherlands)

    Breman, A.C.

    2014-01-01

    Cinchona alkaloids have a long history as being a powerful medicine against malaria. Since a relative short period (about 50 years) chemist have also used these alkaloids as chiral catalyst for a wide variety of asymmetric transformations. Especially since the beginning of this century, when strong

  16. Merging Photoredox Catalysis with Organocatalysis: The Direct Asymmetric Alkylation of Aldehydes

    Science.gov (United States)

    Nicewicz, David A.; MacMilla, David W. C.

    2009-01-01

    Photoredox catalysis and organocatalysis represent two powerful fields of molecule activation that have found widespread application in the areas of inorganic and organic chemistry, respectively. We merged these two catalysis fields to solve problems in asymmetric chemical synthesis. Specifically, the enantioselective intermolecular α-alkylation of aldehydes has been accomplished using an interwoven activation pathway that combines both the photoredox catalyst Ru(bpy)3Cl2 (where bpy is 2,2′-bipyridine) and an imidazolidinone organocatalyst. This broadly applicable, yet previously elusive, alkylation reaction is now highly enantioselective and operationally trivial. PMID:18772399

  17. Remote Cooperative Group Strategy Enables Ligands for Accelerative Asymmetric Gold Catalysis.

    Science.gov (United States)

    Wang, Zhixun; Nicolini, Corrado; Hervieu, Cedric; Wong, Yuk-Fai; Zanoni, Giuseppe; Zhang, Liming

    2017-11-15

    An accelerative asymmetric gold catalysis is achieved for the first time via chiral ligand metal cooperation. An asymmetrically positioned remote amide group in the designed chiral binaphthyl-based ligand plays the essential role of a general base catalyst and selectively accelerates the cyclizations of 4-allen-1-ols into one prochiral allene face. The reactions are mostly highly enantioselective with achiral substrates, and due to the accelerated nature of the catalysis catalyst loadings as low as 100 ppm are allowed. With a pre-existing chiral center at any of the backbone sp 3 -carbons, the reaction remained highly efficient and most importantly maintained excellent allene facial selectivities regardless of the substrate stereochemistry. By using different combinations of ligand and substrate enantiomers, it is now possible to access all four stereoisomers of versatile 2-vinyltetrahydrofurans with exceedingly high selectivity. The underpinning design of this chemistry reveals a novel and conceptually distinctive strategy to tackle challenging asymmetric gold catalysis, which to date has relied on decelerative asymmetric steric hindrance approaches.

  18. Asymmetric Catalysis with CO2 : The Direct α-Allylation of Ketones.

    Science.gov (United States)

    Pupo, Gabriele; Properzi, Roberta; List, Benjamin

    2016-05-10

    Quaternary stereocenters are found in numerous bioactive molecules. The Tsuji-Trost reaction has proven to be a powerful C-C bond forming process, and, at least in principle, should be well suited to access quaternary stereocenters via the α-allylation of ketones. However, while indirect approaches are known, the direct, catalytic asymmetric α-allylation of branched ketones has been elusive until today. By combining "enol catalysis" with the use of CO2 as a formal catalyst for asymmetric catalysis, we have now developed a solution to this problem: we report a direct, highly enantioselective and highly atom-economic Tsuji-Trost allylation of branched ketones with allylic alcohol. Our reaction delivers products bearing quaternary stereocenters with high enantioselectivity and water as the sole by-product. We expect our methodology to be of utility in asymmetric catalysis and inspire the design of other highly atom-economic transformations. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. SHORT COMMUNICATION SOLVENT FREE PREPARATION OF N ...

    African Journals Online (AJOL)

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    carboxy, 4-bromo, 4- hydroxy, 3-hydroxy, 4-chloro and ... KEYWORDS: Solvent free, Maleanilic acids, Maleic anhydride, Aniline derivatives ... vibration, also referred to as the amide II bands and are characterized to primary and secondary amide [16].

  20. Asymmetric fluorination of α-branched cyclohexanones enabled by a combination of chiral anion phase-transfer catalysis and enamine catalysis using protected amino acids.

    Science.gov (United States)

    Yang, Xiaoyu; Phipps, Robert J; Toste, F Dean

    2014-04-09

    We report a study involving the successful merger of two separate chiral catalytic cycles: a chiral anion phase-transfer catalysis cycle to activate Selectfluor and an enamine activation cycle, using a protected amino acid as organocatalyst. We have demonstrated the viability of this approach with the direct asymmetric fluorination of α-substituted cyclohexanones to generate quaternary fluorine-containing stereocenters. With these two chiral catalytic cycles operating together in a matched sense, high enantioselectivites can be achieved, and we envisage that this dual catalysis method has the potential to be more broadly applicable, given the breadth of enamine catalysis. It also represents a rare example of chiral enamine catalysis operating successfully on α-branched ketones, substrates commonly inert to this activation mode.

  1. Solvent-free fluidic organic dye lasers.

    Science.gov (United States)

    Choi, Eun Young; Mager, Loic; Cham, Tran Thi; Dorkenoo, Kokou D; Fort, Alain; Wu, Jeong Weon; Barsella, Alberto; Ribierre, Jean-Charles

    2013-05-06

    We report on the demonstration of liquid organic dye lasers based on 9-(2-ethylhexyl)carbazole (EHCz), so-called liquid carbazole, doped with green- and red-emitting laser dyes. Both waveguide and Fabry-Perot type microcavity fluidic organic dye lasers were prepared by capillary action under solvent-free conditions. Cascade Förster-type energy transfer processes from liquid carbazole to laser dyes were employed to achieve color-variable amplified spontaneous emission and lasing. Overall, this study provides the first step towards the development of solvent-free fluidic organic semiconducting lasers and demonstrates a new kind of optoelectronic applications for liquid organic semiconductors.

  2. Asymmetric catalysis mediated by the ligand sphere of octahedral chiral-at-metal complexes.

    Science.gov (United States)

    Gong, Lei; Chen, Liang-An; Meggers, Eric

    2014-10-06

    Due to the relationship between structure and function in chemistry, access to novel chemical structures ultimately drives the discovery of novel chemical function. In this light, the formidable utility of the octahedral geometry of six-coordinate metal complexes is founded in its stereochemical complexity combined with the ability to access chemical space that might be unavailable for purely organic compounds. In this Minireview we wish to draw attention to inert octahedral chiral-at-metal complexes as an emerging class of metal-templated asymmetric "organocatalysts" which exploit the globular, rigid nature and stereochemical options of octahedral compounds and promise to provide new opportunities in the field of catalysis. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Asymmetric Diels-Alder Cycloadditions of Trifluoromethylated Dienophiles Under Trienamine Catalysis.

    Science.gov (United States)

    Yuan, Xin; Zhang, Shan-Jun; Du, Wei; Chen, Ying-Chun

    2016-07-25

    β-Trifluoromethyl (CF3 ) enones were proved to act as good dienophiles in asymmetric normal-electron-demand Diels-Alder cycloadditions with 2,4-dienals under trienamine catalysis with a chiral secondary amine. The sequential reductive amination transformations with benzylamine produced cis- and trans-fused chiral trifluoromethylated octahydroisoquinolines in a diastereodivergent manner by using NaBH(OAc)3 and NaBH3 CN as the reductants, respectively. Moreover, other types of activated alkenes that bear a CF3 group have also been successfully utilized to construct a diverse range of chiral cyclic frameworks in high stereoselectivity. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Dynamics of solvent-free grafted nanoparticles

    KAUST Repository

    Chremos, Alexandros

    2012-01-01

    The diffusivity and structural relaxation characteristics of oligomer-grafted nanoparticles have been investigated with simulations of a previously proposed coarse-grained model at atmospheric pressure. Solvent-free, polymer-grafted nanoparticles as well as grafted nanoparticles in a melt were compared to a reference system of bare (ungrafted) particles in a melt. Whereas longer chains lead to a larger hydrodynamic radius and lower relative diffusivity for grafted particles in a melt, bulk solvent-free nanoparticles with longer chains have higher relative diffusivities than their short chain counterparts. Solvent-free nanoparticles with short chains undergo a glass transition as indicated by a vanishing diffusivity, diverging structural relaxation time and the formation of body-centered-cubic-like order. Nanoparticles with longer chains exhibit a more gradual increase in the structural relaxation time with decreasing temperature and concomitantly increasing particle volume fraction. The diffusivity of the long chain nanoparticles exhibits a minimum at an intermediate temperature and volume fraction where the polymer brushes of neighboring particles overlap, but must stretch to fill the interparticle space. © 2012 American Institute of Physics.

  5. Catálise assimétrica na ciclopropanação de olefinas Asymmetric catalysis in the cyclopropanation of olefins

    Directory of Open Access Journals (Sweden)

    Raquel A. C. Leão

    2007-01-01

    Full Text Available The main methodologies in the asymmetric cyclopropanation of alkenes with emphasis on asymmetric catalysis are covered. Exemples are the Simmons-Smith reaction, the use of diazoalkanes and reactions carried out by decomposition of alpha-diazoesters in the presence of transition metals.

  6. Synergistic Catalysis for the Asymmetric [3+2] Cycloaddition of Vinyl Aziridines with α,β-Unsaturated Aldehydes.

    Science.gov (United States)

    Naesborg, Line; Tur, Fernando; Meazza, Marta; Blom, Jakob; Halskov, Kim Søholm; Jørgensen, Karl Anker

    2017-01-05

    The first asymmetric [3+2] cycloaddition of vinyl aziridines with α,β-unsaturated aldehydes, based on synergistic catalysis, is disclosed. This methodology allows the formation of attractive pyrrolidine structures in good yields (up to 84 %), moderate diastereoselectivity, and high enantioselectivity values (up to >99 % ee). Additionally, a tricyclic pyrrolidine core structure found in biologically active molecules was synthesized in a one-pot fashion by using the presented reaction concept. Finally, a mechanistic proposal is outlined. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Sixteen isostructural phosphonate metal-organic frameworks with controlled Lewis acidity and chemical stability for asymmetric catalysis.

    Science.gov (United States)

    Chen, Xu; Peng, Yongwu; Han, Xing; Liu, Yan; Lin, Xiaochao; Cui, Yong

    2017-12-19

    Heterogeneous catalysts typically lack the specific steric control and rational electronic tuning required for precise asymmetric catalysis. Here we demonstrate that a phosphonate metal-organic framework (MOF) platform that is robust enough to accommodate up to 16 different metal clusters, allowing for systematic tuning of Lewis acidity, catalytic activity and enantioselectivity. A total of 16 chiral porous MOFs, with the framework formula [M3 L 2(solvent)2] that have the same channel structures but different surface-isolated Lewis acid metal sites, are prepared from a single phosphono-carboxylate ligand of 1,1'-biphenol and 16 different metal ions. The phosphonate MOFs possessing tert-butyl-coated channels exhibited high thermal stability and good tolerances to boiling water, weak acid and base. The MOFs provide a versatile family of heterogeneous catalysts for asymmetric allylboration, propargylation, Friedel-Crafts alkylation and sulfoxidation with good to high enantioselectivity. In contrast, the homogeneous catalyst systems cannot catalyze the test reactions enantioselectively.

  8. Asymmetric catalysis in aqueous media: use of metal-chiral crown ethers as efficient chiral Lewis acid catalysts in asymmetric aldol reactions

    Directory of Open Access Journals (Sweden)

    Shu Kobayashi

    2001-01-01

    Full Text Available Metal-chiral crown ether complexes have been developed as efficient chiral Lewis acid catalysts for asymmetric aldol reactions of silyl enol ethers with aldehydes in aqueous media. While many excellent catalytic asymmetric reactions have been developed recently, most of them have to be carried out under strictly anhydrous conditions in organic solvents. This is probably due to the instability of many catalysts and/or intermediates in the presence of even a small amount of water. To address this issue, we searched for metal-crown ether complexes on the basis of our "multi-coordination" hypothesis, and found that lead(II and lanthanide(III catalysts worked well as chiral Lewis acids in aqueous media. To the best of our knowledge, these are the first examples of chiral crown-based Lewis acids that can be successfully used in catalytic asymmetric reactions. The catalysts have been characterized by X-ray diffraction, and their unique structures as chiral catalysts have been revealed. Use of water as a solvent is essential in these asymmetric catalysis, and the role of water on these reactions to explain the high reactivity and selectivity has been suggested. Another important point is that kinetic studies have shown the possibility that these types of crown ether complexes would be suitable as chiral catalysts employed in aqueous media. In addition, although the catalytic asymmetric aldol reactions are one of the most powerful carbon-carbon bond-forming methodologies and several successful examples have been reported, the use of aprotic anhydrous solvents and low reaction temperatures (-78 °C has been needed in almost all successful cases. On the other hand, the present reactions proceeded smoothly at -10-0 °C in water-alcohol solutions while retaining high levels of diastereo- and enantioselectivities.

  9. Ligand Self-Sorting and Nonlinear Effects in Dinuclear Asymmetric Hydrogenation: Complexity in Catalysis

    NARCIS (Netherlands)

    Terrade, F.G.; Lutz, M.|info:eu-repo/dai/nl/304828971; Reek, J.N.H.

    2013-01-01

    Nature has been a source of inspiration for scientists as billion years of evolution have resulted in magnificent examples of how processes can be controlled efficiently. In the field of supramolecular catalysis, enzymes have been the major source of inspiration. As such, many synthetic systems have

  10. Solvent free lipase catalyzed synthesis of butyl caprylate

    Indian Academy of Sciences (India)

    % loss from its initial activity. The thermodynamic parametersnat different temperatures were also determined. The esterification was conducted successfully with 92% as maximum conversion in 5 h in a stirred batch reactor under solvent free ...

  11. Organic Synthesis under Solvent-free Condition. An Environmentally ...

    Indian Academy of Sciences (India)

    /fulltext/reso/007/10/0059-0068. Keywords. Solvents-free reactions; ecofriendly reactions; solid-solid reactions. Author Affiliations. Gopalpur Nagendrappa1. Department of Chemistry Bangalore University (Central College Campus) Bangalore ...

  12. SOLVENT-FREE SYNTHESIS OF XANTHENE DERIVATIVES BY ...

    African Journals Online (AJOL)

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    . SOLVENT-FREE SYNTHESIS OF XANTHENE DERIVATIVES BY PREYSSLER. TYPE HETEROPOLYACID. Majid M. Heravi1*, Hamideh Alinejhad1, Khadijeh Bakhtiari1, Mina Saeedi1*, Hossein A. Oskooie1 and Fatemeh F. Bamoharram2.

  13. Assisted Tandem Catalysis : Metathesis Followed by Asymmetric Hydrogenation from a Single Ruthenium Source

    NARCIS (Netherlands)

    Renom-Carrasco, Marc; Gajewski, Piotr; Pignataro, Luca; de Vries, Johannes G.; Piarulli, Umberto; Gennari, Cesare; Lefort, Laurent

    2015-01-01

    Here we report the first example of a tandem metathesis-asymmetric hydrogenation protocol where the prochiral olefin generated by metathesis is hydrogenated with high enantioselectivity by an in situ formed chiral ruthenium catalyst. We show that either the ruthenium metathesis catalysts or the

  14. as a Novel Chiral Ligand for Catalysis of the Asymmetric Diels-Al

    African Journals Online (AJOL)

    NJD

    2008-11-25

    Nov 25, 2008 ... the ligand in dichloromethane.22 The resultant catalyst complex was used to promote the described asymmetric Diels-Alder reaction (Scheme 1). From a range of metal salts evaluated, anhydrous Mg(ClO4)2 emerged as the best Lewis acid complex in terms of enantio- selectivity (Table 1, entry 6).

  15. Applications of ortho-Quinone Methide Intermediates in Catalysis and Asymmetric Synthesis

    OpenAIRE

    Pathak, Tejas P.; Sigman, Matthew S.

    2011-01-01

    Ortho -quinone methides are important synthetic intermediates and widely implicated in biological processes. In this Synopsis, recent advances concerning the synthesis and utility of these intermediates are discussed with a particular emphasis on metal-catalyzed formation of quinone methide intermediates. Additionally, applications of these intermediates as partners in asymmetric synthesis will be discussed including methods we have developed that involve the enantioselective Pd-catalyzed for...

  16. Synthesis of Main-Chain Chiral Quaternary Ammonium Polymers for Asymmetric Catalysis Using Quaternization Polymerization

    Directory of Open Access Journals (Sweden)

    Md. Masud Parvez

    2012-06-01

    Full Text Available Main-chain chiral quaternary ammonium polymers were successfully synthesized by the quaternization polymerization of cinchonidine dimer with dihalides. The polymerization occurred smoothly under optimized conditions to give novel type of main-chain chiral quaternary ammonium polymers. The catalytic activity of the polymeric chiral organocatalysts was investigated on the asymmetric benzylation of N-(diphenylmethylideneglycine tert-butyl ester.

  17. Attractive noncovalent interactions in asymmetric catalysis: Links between enzymes and small molecule catalysts

    Science.gov (United States)

    Knowles, Robert R.; Jacobsen, Eric N.

    2010-01-01

    Catalysis by neutral, organic, small molecules capable of binding and activating substrates solely via noncovalent interactions—particularly H-bonding—has emerged as an important approach in organocatalysis. The mechanisms by which such small molecule catalysts induce high enantioselectivity may be quite different from those used by catalysts that rely on covalent interactions with substrates. Attractive noncovalent interactions are weaker, less distance dependent, less directional, and more affected by entropy than covalent interactions. However, the conformational constraint required for high stereoinduction may be achieved, in principle, if multiple noncovalent attractive interactions are operating in concert. This perspective will outline some recent efforts to elucidate the cooperative mechanisms responsible for stereoinduction in highly enantioselective reactions promoted by noncovalent catalysts. PMID:20956302

  18. Asymmetric Hydrogen Bonding Catalysis for the Synthesis of Dihydroquinazoline-Containing Antiviral, Letermovir.

    Science.gov (United States)

    Chung, Cheol K; Liu, Zhijian; Lexa, Katrina W; Andreani, Teresa; Xu, Yingju; Ji, Yining; DiRocco, Daniel A; Humphrey, Guy R; Ruck, Rebecca T

    2017-08-09

    A weak Brønsted acid-catalyzed asymmetric guanidine aza-conjugate addition reaction has been developed. C2-symmetric, dual hydrogen-bond donating bistriflamides are shown to be highly effective in activating α,β-unsaturated esters toward the intramolecular addition of a pendant guanidinyl nucleophile. Preliminary mechanistic investigation, including density functional theory calculations and kinetics studies, support a conjugate addition pathway as more favorable energetically than an alternative electrocyclization pathway. This methodology has been successfully applied to the synthesis of the 3,4-dihydroquinazoline-containing antiviral, Letermovir, and a series of analogues.

  19. Structural Transitions of Solvent-Free Oligomer-Grafted Nanoparticles

    KAUST Repository

    Chremos, Alexandros

    2011-09-01

    Novel structural transitions of solvent-free oligomer-grafted nanoparticles are investigated by using molecular dynamics simulations of a coarse-grained bead-spring model. Variations in core size and grafting density lead to self-assembly of the nanoparticles into a variety of distinct structures. At the boundaries between different structures, the nanoparticle systems undergo thermoreversible transitions. This structural behavior, which has not been previously reported, deviates significantly from that of simple liquids. The reversible nature of these transitions in solvent-free conditions offers new ways to control self-assembly of nanoparticles at experimentally accessible conditions. © 2011 American Physical Society.

  20. [Acid-base catalysis of chiral Pd complexes: development of novel asymmetric reactions].

    Science.gov (United States)

    Hamashima, Yoshitaka

    2005-10-01

    Using a unique character of the chiral palladium complexes 1 and 2, several types of novel catalytic asymmetric reactions have been developed. In contrast to the conventional Pd(0)-catalyzed reactions, these complexes function as an acid-base catalyst. Thus active methine compounds were activated to form chiral palladium enolates, which underwent the enantioselective Michael reaction and Mannich-type reaction with up to 99% ee. Interestingly, these palladium enolates acted cooperatively with a strong protic acid activating the electrophiles, formed concomitantly during the formation of the enolates, whereby the C-C bond-forming reaction was promoted. In addition, this palladium enolate chemistry was also applicable to the electrophilic asymmetric fluorination reactions, and thus various carbonyl compounds including beta-ketoesters, beta-ketophosphonates, and oxindoles were fluorinated in a highly enantioselective manner (up to 98% ee). It is advantageous that these reactions were carried out in environmentally friendly alcoholic solvents such as ethanol, and exclusion of air and moisture is not necessary.

  1. Efficient, green and solvent-free synthesis of tetrasubstituted ...

    Indian Academy of Sciences (India)

    Antimony trichloride absorbed on silica gel (SbCl3/SiO2) efficiently catalyses the four-component cyclocondensation of 1,2-diketone, aldehyde, ammonium acetate, and primary amine under solvent-free conditions to afford the corresponding tetrasubstituted imidazoles in high yields. The main merit of this study is ...

  2. A Solvent-free Synthesis of Polyhydroquinolines via Hantzsch ...

    African Journals Online (AJOL)

    ... work-up procedure and catalyst reusability for several runs. Furthermore, easy isolation of the catalyst from the reaction mixture was enabled by use of an external magnet. KEYWORDS Nanomagnetic-supported sulfonic acid, multicomponent reaction, solvent-free conditions, heterocyclic compound, Hantzsch reaction.

  3. Solvent free lipase catalyzed synthesis of butyl caprylate

    Indian Academy of Sciences (India)

    MEERA T SOSE

    2017-11-10

    Nov 10, 2017 ... Special Issue on Recent Trends in the Design and Development of Catalysts and their Applications. Solvent free lipase ... The ester, butyl caprylate has wide applications in commercial market and it also possesses characteristic fruity ... lyst can offer better advantage rather the use of acid or harmful catalyst ...

  4. Organic Synthesis under Solvent-free Condition. An Environmentally ...

    Indian Academy of Sciences (India)

    environmental pollution caused by solvents and also their academic interest in solid-solid reactions have led them in recent times to develop methodologies for solvent-free reac- tions with considerable success. The Function of a Solvent. A general assumption with regard to organic reactions is that they are performed in a ...

  5. Microwave accelerated solvent-free synthesis of flavanones

    Energy Technology Data Exchange (ETDEWEB)

    Sagrera, Gabriel J. [Universidad de la Republica, Montevideo (Uruguay). Facultad de Ciencias. Dept. de Quimica Organica]. E-mail: gseoane@fq.edu.uy; Seoane, Gustavo A. [Universidad de la Republica, Montevideo (Uruguay). Facultad de Quimica

    2005-07-15

    Microwave irradiation of chalcones under solvent-free conditions resulted in a 'green-chemistry' procedure for the preparation of flavanones in very good yields. Using an unmodified household microwave oven, different mineral supports and catalysts were tested. By irradiation of chalcones with 30% TFA over silica gel, eleven known flavanones and five new compounds were prepared in high yields. (author)

  6. solvent-free synthesis of azomethines, spectral correlations

    African Journals Online (AJOL)

    B. S. Chandravanshi

    multi-linear regression analysis. From the results of statistical analysis, the effect of substituents on the above spectral data has been studied. The antimicrobial activities of all imines have been studied using standard methods. KEY WORDS: Solvent-free synthesis, Fly-ash: PTS, Aryl imines, Spectral correlations, ...

  7. INVESTIGATION OF THE SOLVENT FREE ISOMERISATION OF cis ...

    African Journals Online (AJOL)

    Preferred Customer

    mopipi.ub.bw. INVESTIGATION OF THE SOLVENT FREE ISOMERISATION OF cis-Mo(CO)4L2. [L = PPh2Et, PPh3, PPh2Me, AND P(m-tolyl)3] BY DIFFUSE REFLECTANCE. INFRARED FOURIER TRANSFORM SPECTROSCOPY AND THERMAL ...

  8. One-pot Solvent-free Catalytic Dimerization Reaction of ...

    Indian Academy of Sciences (India)

    Catalytic reactions; Phenylacetylene; 1-Phenylnaphthalene; Copper(0)-Carbone catalyst; Solvent free synthesis; EDS; SEM; Molecular modelling. 1. Introduction. Polycyclic aromatic hydrocarbons (PAHs) have been attracting a lot of attention in recent years.1–6 They are formed as a result of burning organic compounds ...

  9. cis-2,5-Diaminobicyclo[2.2.2]octane, a New Chiral Scaffold for Asymmetric Catalysis.

    Science.gov (United States)

    Shaw, Subrata; White, James D

    2016-09-20

    Catalysis of widely used chemical transformations in which the goal is to obtain the product as a pure enantiomer has become a major preoccupation of synthetic organic chemistry over the past three decades. A large number of chiral entities has been deployed to this end, many with considerable success, but one of the simplest and most effective catalytic systems to have emerged from this effort is that based on a chiral diamine, specifically trans-1,2-diaminocyclohexane. While there have been attempts to improve upon this scaffold in asymmetric synthesis, few have gained the recognition needed to take their place alongside this classic diamine. The challenge is to design a scaffold that retains the assets of trans-1,2-diaminocyclohexane while enhancing its intrinsic chirality and maximizing the scope of its applications. It occurred to us that cis-2,5-diaminobicyclo[2.2.2]octane could be such a scaffold. Synthesis of this diamine in enantiopure form was completed from benzoic acid, and the (1R,2R,4R,5R) enantiomer was used in all subsequent experiments in this laboratory. Condensation of the diamine with various salicyl aldehydes generated imine derivatives which proved to be excellent "salen" ligands for encapsulation of transition and other metals. In total, 12 salen-metal complexes were prepared from this ligand, many of which were crystalline and three of which, along with the ligand itself, yielded to X-ray crystallography. An advantage of this ligand is that it can be tuned sterically or electronically to confer specific catalytic properties on the salen-metal complex, and this feature was used in several applications of our salen-metal complexes in asymmetric synthesis. Thus, replacement of one of the tert-butyl groups in each benzenoid ring of the salen ligand by a methoxy substituent enhanced the catalytic efficiency of a cobalt(II)-salen complex used in asymmetric cyclopropanation of 1,1-disubstituted alkenes; the catalyst was employed in an improved

  10. Ruthenium complexes with chiral tetradentate PNNP ligands: asymmetric catalysis from the viewpoint of inorganic chemistry.

    Science.gov (United States)

    Mezzetti, Antonio

    2010-09-14

    This is a personal account of the application of ruthenium complexes containing chiral tetradentate ligands with a P(2)N(2) ligand set (PNNP) as catalyst precursors for enantioselective "atom transfer" reactions. Therewith are meant reactions that involve bond formation between a metal-coordinated molecule and a free reagent. The reactive fragment (e.g. carbene) is transferred either from the metal to the non-coordinated substrate (e.g. olefin) or from the free reagent (e.g. F(+)) to the metal-bound substrate (e.g.beta-ketoester), depending on the class of catalyst (monocationic, Class A; or dicationic, Class B). The monocationic five-coordinate species [RuCl(PNNP)](+) and the six-coordinate complexes [RuCl(L)(PNNP)](+) (L = Et(2)O, H(2)O) of Class A catalyse asymmetric epoxidation, cyclopropanation (carbene transfer from the metal to the free olefin), and imine aziridination. Alternatively, the dicationic complexes [Ru(L-L)(PNNP)](2+) (Class B), which contain substrates that act as neutral bidentate ligands L-L (e.g., beta-ketoesters), catalyse Michael addition, electrophilic fluorination, and hydroxylation reactions. Additionally, unsaturated beta-ketoesters form dicationic complexes of Class B that catalyse Diels-Alder reactions with acyclic dienes to produce tetrahydro-1-indanones and estrone derivatives. Excellent enantioselectivity has been achieved in several of the catalytic reactions mentioned above. The study of key reaction intermediates (both in the solid state and in solution) has revealed significant mechanistic aspects of the catalytic reactions.

  11. Chiral Covalent Organic Frameworks with High Chemical Stability for Heterogeneous Asymmetric Catalysis.

    Science.gov (United States)

    Han, Xing; Xia, Qingchun; Huang, Jinjing; Liu, Yan; Tan, Chunxia; Cui, Yong

    2017-06-28

    Covalent organic frameworks (COFs) featuring chirality, stability, and function are of both fundamental and practical interest, but are yet challenging to achieve. Here we reported the metal-directed synthesis of two chiral COFs (CCOFs) by imine-condensations of enantiopure 1,2-diaminocyclohexane with C3-symmetric trisalicylaldehydes having one or zero 3-tert-butyl group. Powder X-ray diffraction and modeling studies, together with pore size distribution analysis demonstrate that the Zn(salen)-based CCOFs possess a two-dimensional hexagonal grid network with AA stacking. Dramatic enhancement in the chemical stability toward acidic (1 M HCl) and basic (9 M NaOH) conditions was observed for the COF incorporated with tert-butyl groups on the pore walls compared to the nonalkylated analog. The Zn(salen) modules in the CCOFs allow for installing multivariate metals into the frameworks by postsynthetic metal exchange. The exchanged CCOFs maintain high crystallinity and porosity and can serve as efficient and recyclable heterogeneous catalysts for asymmetric cyanation of aldehydes, Diels-Alder reaction, alkene epoxidation, epoxide ring-opening, and related sequential reactions with up to 97% ee.

  12. Solvent Free Synthesis of Chalcones and their Antibacterial Activities

    Directory of Open Access Journals (Sweden)

    K. Rajendra K. Saini

    2005-01-01

    Full Text Available The solvent free synthesis of six chalcones was carried out by grinding the piperanal and the acetophenone (unsubstituted, 4-methyl, 4-methoxy, 4-bromo, 4-nitro, 3-chloro in the presence of solid sodium hydroxide with a mortar and pestle. In general, the chalcones were obtained in high yield and high purity. Minor quantities of Ketol and Michael addition product were easily removed by recrystallization. The result indicates a correlation between the success of the solvent-free synthesis and melting point of the chalcone. Chalcone with relatively high melting points (higher than 80°C were obtained in high yields. The two chalcones that could not be produced in good yields were having relatively low melting points. They have been screened for their antibacterial activity against Gram positive and Gram negative bacteria.

  13. Photo-triggered solvent-free metamorphosis of polymeric materials

    OpenAIRE

    Honda, Satoshi; Toyota, Taro

    2017-01-01

    Liquefaction and solidification of materials are the most fundamental changes observed during thermal phase transitions, yet the design of organic and polymeric soft materials showing isothermal reversible liquid?nonliquid conversion remains challenging. Here, we demonstrate that solvent-free repeatable molecular architectural transformation between liquid-star and nonliquid-network polymers that relies on cleavage and reformation of a covalent bond in hexaarylbiimidazole. Liquid four-armed s...

  14. Solvent-free microwave-mediated Michael addition reactions

    Indian Academy of Sciences (India)

    Unknown

    “green chemistry”, a reaction should ideally, be con- ducted under solvent-free conditions with minimal or no side-product formation and with utmost atom- economy.10 Even though microwave-assisted sol- vent-free Michael addition reactions on BiCl3 or CdI2,11. EuCl3,12 CeCl3.5H2O,13 and alumina14 surfaces are.

  15. Insights into the asymmetric heterogeneous catalysis in porous organic polymers: constructing a TADDOL-embedded chiral catalyst for studying the structure-activity relationship.

    Science.gov (United States)

    An, Wan-Kai; Han, Man-Yi; Wang, Chang-An; Yu, Si-Min; Zhang, Yuan; Bai, Shi; Wang, Wei

    2014-08-25

    Construction of porous organic polymers (POPs) as asymmetric catalysts remains as an important but challenging task. Herein, we exploit the "bottom-up" strategy to facilely synthesize an α,α,α',α'-tetraaryl-1,3-dioxolane-4,5-dimethanol (TADDOL)-based chiral porous polymer (TADDOL-CPP) for highly efficient asymmetric catalysis. Constructed through the covalent linkages among the three-dimensional rigid monomers, TADDOL-CPP possesses hierarchical porous structure, high Brunauer-Emmett-Teller (BET) surface area, together with abundant and uniformly-distributed chiral sites. In the presence of [Ti(OiPr)4], TADDOL-CPP acts as a highly efficient and recyclable catalyst in the asymmetric addition of diethylzinc (Et2Zn) to aromatic aldehydes. Based on the direct observation of the key intermediates, the reaction mechanism has been revealed by solid-state (13)C magic-angle spinning (MAS) NMR spectroscopy. In combination with the catalytic testing results, characterization on the working catalyst provides further information for understanding the structure-activity relationship. We suggest that the catalytic activity of TADDOL-CPP is largely affected by the structural rigidity, cooperative catalysis, local chiral environment, and hierarchical porous framework. We expect that the information obtained herein will benefit to the designed synthesis of robust POP catalysts toward practical applications. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Asymmetric catalysis in Brazil: development and potential for advancement of Brazilian chemical industry; Catalise assimetrica no Brasil: desenvolvimento e potencialidades para o avanco da industria quimica brasileira

    Energy Technology Data Exchange (ETDEWEB)

    Braga, Antonio Luiz, E-mail: braga.antonio@ufsc.br [Universidade Federal de Santa Catarina (UFSC), Florianopolis, SC (Brazil). Departamento de Quimica; Luedtke, Diogo Seibert; Schneider, Paulo Henrique [Universidade Federal do Rio Grande do Sul (UFRS), Porto Alegre, RS (Brazil). Instituto de Quimica; Andrade, Leandro Helgueira [Universidade de Sao Paulo (USP), SP (Brazil). Instituto de Quimica; Paixao, Marcio Weber [Universidade Federal de Sao Carlos (UFSCar), SP (Brazil). Departamento de Quimica

    2013-07-01

    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, will be needed. These incentives could be a breakthrough once we establish several research groups working in the area of organic synthesis and on the development and application of chiral organocatalysts and ligands in asymmetric catalysis, thus contributing to boost the development of the Brazilian chemical industry. Considering these circumstances, Brazil can benefit from this opportunity because we have a wide biodiversity and a large pool of natural resources that can be used as starting materials for the production of new chiral catalysts and are creating competence in asymmetric catalysis and related areas. This may decisively contribute to the growth of chemistry in our country. (author)

  17. Solvent-Free Synthesis of Some1-Acetyl Pyrazoles

    Energy Technology Data Exchange (ETDEWEB)

    Thirunarayanan, Ganesamoorthy [Annamalai Univ., Tamil Nadu (India); Sekar, Krishnamoorthy Guna [National College, Tiruchirappalli (India)

    2013-10-15

    Some N-acetyl pyrazoles including 1-(3-(3,4-dichlorophenyl)-5-(substituted phenyl)-4,5-dihydro-{sup 1}H-pyrazole-1-yl) ethanones have been synthesised by solvent free cyclization cum acetylation of chalcones like substituted styryl 3,4-dichlorophenyl ketones using hydrazine hydrate and acetic anhydride in presence of catalytic amount of fly-ash: H{sub 2}SO{sub 4} catalyst. The yield of these N-acetyl pyrazole derivatives are more than 75%. The synthesised N-acetyl pyrazoline derivatives were characterized by their physical constants and spectral data.

  18. Photo-triggered solvent-free metamorphosis of polymeric materials.

    Science.gov (United States)

    Honda, Satoshi; Toyota, Taro

    2017-09-11

    Liquefaction and solidification of materials are the most fundamental changes observed during thermal phase transitions, yet the design of organic and polymeric soft materials showing isothermal reversible liquid-nonliquid conversion remains challenging. Here, we demonstrate that solvent-free repeatable molecular architectural transformation between liquid-star and nonliquid-network polymers that relies on cleavage and reformation of a covalent bond in hexaarylbiimidazole. Liquid four-armed star-shaped poly(n-butyl acrylate) and poly(dimethyl siloxane) with 2,4,5-triphenylimidazole end groups were first synthesized. Subsequent oxidation of the 2,4,5-triphenylimidazoles into 2,4,5-triphenylimidazoryl radicals and their coupling with these liquid star polymers to form hexaarylbiimidazoles afforded the corresponding nonliquid network polymers. The resulting nonliquid network polymers liquefied upon UV irradiation and produced liquid star-shaped polymers with 2,4,5-triphenylimidazoryl radical end groups that reverted to nonliquid network polymers again by recoupling of the generated 2,4,5-triphenylimidazoryl radicals immediately after terminating UV irradiation.The design of organic and polymeric soft materials showing isothermal reversible liquid-nonliquid conversion is challenging. Here, the authors show solvent-free repeatable molecular architectural transformation between liquid-star and non-liquid-network polymers by the cleavage and reformation of covalent bonds in the polymer chain.

  19. Controlling stereochemical outcomes of asymmetric processes by catalyst remote molecular functionalizations: chiral diamino-oligothiophenes (DATs) as ligands in asymmetric catalysis.

    Science.gov (United States)

    Albano, Vincenzo Giulio; Bandini, Marco; Barbarella, Giovanna; Melucci, Manuela; Monari, Magda; Piccinelli, Fabio; Tommasi, Simona; Umani-Ronchi, Achille

    2006-01-11

    The synthesis, characterization, and structure-guided application of a new class of highly versatile chiral C(2)-symmetric diamine-oligothiophene ligands in Pd-catalyzed asymmetric transformations are presented. Experimental investigations of the intimate role of pendant pi-conjugate oligothiophenes in determining the catalytic activity of the corresponding chiral Pd complexes are described. Their unusual behavior opens up new routes toward the logical design of finely tuned organometallic catalysts by remote structural functionalizations.

  20. Stereodirection of an α-ketoester at sub-molecular sites on chirally modified Pt(111): Heterogeneous asymmetric catalysis

    DEFF Research Database (Denmark)

    Demers-Carpentier, V.; Rasmussen, A.M.H.; Goubert, G.

    2013-01-01

    Chirally modified Pt catalysts are used in the heterogeneous asymmetric hydrogenation of α-ketoesters. Stereoinduction is believed to occur through the formation of chemisorbed modifier–substrate complexes. In this study, the formation of diastereomeric complexes by coadsorbed methyl 3,3,3-triflu......Chirally modified Pt catalysts are used in the heterogeneous asymmetric hydrogenation of α-ketoesters. Stereoinduction is believed to occur through the formation of chemisorbed modifier–substrate complexes. In this study, the formation of diastereomeric complexes by coadsorbed methyl 3...

  1. Solvent-free covalent functionalization of nanodiamond with amines

    Energy Technology Data Exchange (ETDEWEB)

    Basiuk, Elena V., E-mail: elenagd@unam.mx [Centro de Ciencias Aplicadas y Desarrollo Tecnológico, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, 04510 México D.F. (Mexico); Santamaría-Bonfil, Adriana; Meza-Laguna, Victor [Centro de Ciencias Aplicadas y Desarrollo Tecnológico, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, 04510 México D.F. (Mexico); Gromovoy, Taras Yu. [Institute of Surface Chemistry, National Academy of Sciences of the Ukraine, Gen. Naumova 17, 03164 Kiev (Ukraine); Alvares-Zauco, Edgar [Facultad de Ciencias, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, 04510 México D.F. (Mexico); Contreras-Torres, Flavio F.; Rizo, Juan [Centro de Ciencias Aplicadas y Desarrollo Tecnológico, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, 04510 México D.F. (Mexico); Zavala, Guadalupe [Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, 62210, Cuernavaca, Morelos (Mexico); Basiuk, Vladimir A. [Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, 04510 México, D.F. (Mexico)

    2013-06-15

    Covalent functionalization of pristine nanodiamond (ND) with 1,12-diaminododecane (DAD), 1,5-diaminonaphthalene (DAN), poly(ethylene glycol) diamine (PEGDA), and polyethylenimine (PEI) was carried out by employing solvent-free methodology, which is based on thermal instead of chemical activation of carboxylic groups at ND surface. A simple solubility/dispersibility test in water and isopropanol showed an increased lipophilicity of the functionalized samples. The conversion of intrinsic carboxylic groups into the corresponding amide derivatives was characterized by means of Fourier-transform infrared spectroscopy. Thermogravimetric analysis found the highest organic content of about 18% for ND-PEI, followed by ND-DAD, for which the contribution of covalently bonded diamine was estimated to be of ca. 10%. In temperature programmed desorption measurements with mass spectrometric detection, the presence of organic functionalizing groups changed both mass spectra and thermodesorption curves of ND. The changes in morphology of primary and secondary ND aggregates were characterized by scanning and transmission electron microscopy, as well as by atomic force microscopy. The current–voltage measurements under atmospheric pressure found an increased conductivity for ND-DAN, as compared to that of pristine ND, whereas for ND-DAD, ND-PEGDA and ND-PEI a dramatic decrease in conductivity due to functionalization was observed.

  2. Solvent-free functionalization of carbon nanotube buckypaper with amines

    Energy Technology Data Exchange (ETDEWEB)

    Basiuk, Elena V., E-mail: elbg1111@gmail.com [Centro de Ciencias Aplicadas y Desarrollo Tecnológico, Universidad Nacional Autónoma de México, Circuito Exterior C.U., 04510 México D.F., México (Mexico); Ramírez-Calera, Itzel J. [Centro de Ciencias Aplicadas y Desarrollo Tecnológico, Universidad Nacional Autónoma de México, Circuito Exterior C.U., 04510 México D.F., México (Mexico); Meza-Laguna, Victor [Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Circuito Exterior C.U., 04510 México D.F., México (Mexico); Abarca-Morales, Edgar; Pérez-Rey, Luis A. [Centro de Ciencias Aplicadas y Desarrollo Tecnológico, Universidad Nacional Autónoma de México, Circuito Exterior C.U., 04510 México D.F., México (Mexico); Re, Marilena [Italian National Agency for New Technologies, Energy and Sustainable Economic Development, Technical Unit for Material Technologies, 72100 Brindisi (Italy); Prete, Paola [Istituto per la Microelettronica e Microsistemi, via Monteroni, 73100 Lecce (Italy); Lovergine, Nico [Dipartimento di Ingegneria dell’Innovazione, Università del Salento, S.P. 6 Lecce-Monteroni, I-73100 Lecce (Italy); and others

    2015-12-01

    Graphical abstract: - Abstract: We demonstrate the possibility of fast and efficient solvent-free functionalization of buckypaper (BP) mats prefabricated from oxidized multiwalled carbon nanotubes (MWCNTs-ox), by using three representative amines of different structure: one monofunctional aliphatic amine, octadecylamine (ODA), one monofunctional aromatic amine, 1-aminopyrene (AP), and one aromatic diamine, 1,5-diaminonaphthalene (DAN). The functionalization procedure, which relies on the formation of amide bonds with carboxylic groups of MWCNTs-ox, is performed at 150–180 °C under reduced pressure and takes about 4 h including auxiliary degassing. The amine-treated BP samples (BP-ODA, BP-AP and BP-DAN, respectively) were characterized by means of a variety of analytical techniques such as Fourier-transform infrared and Raman spectroscopy, thermogravimetric and differential thermal analysis, scanning and transmission electron microscopy, scanning helium ion microscopy, and atomic force microscopy. The highest amine content was found for BP-ODA, and the lowest one was observed for BP-DAN, with a possible contribution of non-covalently bonded amine molecules in all three cases. Despite of some differences in spectral and morphological characteristics for amine-functionalized BP samples, they have in common a dramatically increased stability in water as compared to pristine BP and, on the other hand, a relatively invariable electrical conductivity.

  3. Microwave-assisted silica-promoted solvent-free synthesis of ...

    Indian Academy of Sciences (India)

    Abstract. The derivative of triazolo/benzimidazoquinazolinones is prepared via silica-promoted solvent-free ... G Krishnamurthy and K V Jagannath. Table 1. Silica promoted microwave-assisted solvent-free synthesis of quinazolinone derivatives 1a–2h. Entry. Amine. X ..... versity for financial support, and Indian Institute of.

  4. Asymmetric synthesis of highly substituted β-lactones through oxidative carbene catalysis with LiCl as cooperative Lewis acid.

    Science.gov (United States)

    Bera, Srikrishna; Samanta, Ramesh C; Daniliuc, Constantin G; Studer, Armido

    2014-09-01

    The reaction of enals with β-diketones, β-ketoesters, and malonates bearing a β-oxyalkyl substituent at the α-position by oxidative NHC catalysis to provide highly substituted β-lactones is described. Reactions occur with excellent diastereo- and enantioselectivity. The organo cascade comprises two CC bond formations and one CO bond formation. Up to four contiguous stereogenic centers including two fully substituted stereocenters are formed in the cascade. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Exchange Processes in Shibasaki's Rare Earth Alkali Metal BINOLate Frameworks and Their Relevance in Multifunctional Asymmetric Catalysis.

    Science.gov (United States)

    Robinson, Jerome R; Gu, Jun; Carroll, Patrick J; Schelter, Eric J; Walsh, Patrick J

    2015-06-10

    Shibasaki's rare earth alkali metal BINOLate (REMB) catalysts (REMB; RE = Sc, Y, La - Lu; M = Li, Na, K; B = 1,1-bi-2-naphtholate; RE/M/B = 1/3/3) are among the most successful enantioselective catalysts and have been employed in a broad range of mechanistically diverse reactions. Despite the phenomenal success of these catalysts, several fundamental questions central to their reactivity remain unresolved. Combined reactivity and spectroscopic studies were undertaken to probe the identity of the active catalyst(s) in Lewis-acid (LA) and Lewis-acid/Brønsted-base (LA/BB) catalyzed reactions. Exchange spectroscopy provided a method to obtain rates of ligand and alkali metal self-exchange in the RE/Li frameworks, demonstrating the utility of this technique for probing solution dynamics of REMB catalysts. Isolation of the first crystallographically characterized REMB complex with substrate bound enabled stoichiometric and catalytic reactivity studies, wherein we observed that substrate deprotonation by the catalyst framework was necessary to achieve selectivity. Our spectroscopic observations in LA/BB catalysis are inconsistent with previous mechanistic proposals, which considered only tris(BINOLate) species as active catalysts. These findings significantly expand our understanding of the catalyst structure in these privileged multifunctional frameworks and identify new directions for development of new catalysts.

  6. Stereodirection of an α-ketoester at sub-molecular sites on chirally modified Pt(111): heterogeneous asymmetric catalysis.

    Science.gov (United States)

    Demers-Carpentier, Vincent; Rasmussen, Anton M H; Goubert, Guillaume; Ferrighi, Lara; Dong, Yi; Lemay, Jean-Christian; Masini, Federico; Zeng, Yang; Hammer, Bjørk; McBreen, Peter H

    2013-07-10

    Chirally modified Pt catalysts are used in the heterogeneous asymmetric hydrogenation of α-ketoesters. Stereoinduction is believed to occur through the formation of chemisorbed modifier-substrate complexes. In this study, the formation of diastereomeric complexes by coadsorbed methyl 3,3,3-trifluoropyruvate, MTFP, and (R)-(+)-1-(1-naphthyl)ethylamine, (R)-NEA, on Pt(111) was studied using scanning tunneling microscopy and density functional theory methods. Individual complexes were imaged with sub-molecular resolution at 260 K and at room temperature. The calculations find that the most stable complex isolated in room-temperature experiments is formed by the minority rotamer of (R)-NEA and pro-S MTFP. The stereodirecting forces in this complex are identified as a combination of site-specific chemisorption of MTFP and multiple non-covalent attractive interactions between the carbonyl groups of MTFP and the amine and aromatic groups of (R)-NEA.

  7. Montmorillonite clay-promoted, solvent-free cross-aldol condensations under focused microwave irradiation

    National Research Council Canada - National Science Library

    Rocchi, Damiano; González, Juan F; Menéndez, J Carlos

    2014-01-01

    .... This method involved solvent-free reaction conditions under microwave irradiation in the presence of a clay-based catalyst, and afforded the target compounds in good yields and short reaction times...

  8. Durability of solvent-free one-step self-etch adhesive under simulated intrapulpal pressure

    National Research Council Canada - National Science Library

    Nagi, Shaymaa M

    2015-01-01

    .... Thus this study was conducted to evaluate the microtensile bond strength (?TBS) of solvent-free and ethanol-based one-step self-etch adhesives to dentin under simulated intrapulpal pressure (IPP...

  9. Microwave-Assisted One-Pot Synthesis of Pyrazolone Derivatives under Solvent-Free Conditions

    Directory of Open Access Journals (Sweden)

    Ruoqun Ma

    2010-05-01

    Full Text Available An efficient one-pot method to generate structurally diverse and medicinally interesting pyrazolone derivatives in good to excellent yields of 51–98% under microwave irradiation and solvent-free conditions has been developed.

  10. Solvent-free Oxidation of Alcohols and Mild Catalytic Deprotection of ...

    African Journals Online (AJOL)

    NJD

    tetrabromobenzene-1,3-disulphonamide. (TBBDA) can be used for solvent-free oxidation of primary and secondary alcohols to the corresponding carbonyl compounds without over-oxidation, and efficient catalytic deprotection of various silyl ...

  11. Microwave-assisted silica-promoted solvent-free synthesis of ...

    Indian Academy of Sciences (India)

    assisted silica-promoted solvent-free synthesis ... Author Affiliations. G Krishnamurthy1 K V Jagannath1. Department of Studies in Chemistry, Central College Campus, Bangalore University, Dr. B R Ambedkar Veedhi, Bengalore 560 001, India ...

  12. Solvent-free Oxidation of Alcohols and Mild Catalytic Deprotection of ...

    African Journals Online (AJOL)

    tetrabromobenzene- 1,3-disulphonamide (TBBDA) can be used for solvent-free oxidation of primary and secondary alcohols to the corresponding carbonyl compounds without over-oxidation, and efficient catalytic deprotection of various silyl ...

  13. Solvent Free Preparation of p-Cymene from Limonene Using Vietnamese Montmorillonite

    DEFF Research Database (Denmark)

    Nguyen, Thao-Tran Thi; Duus, Fritz; Le, Thach Ngoc

    2013-01-01

    p-Cymene, an important intermediate in industrial chemistry, has been prepared in good yields by thermally induced dehydrogenation of limonene under solvent-free reaction conditions using Vietnamese montmorillonite as an efficient green catalyst.......p-Cymene, an important intermediate in industrial chemistry, has been prepared in good yields by thermally induced dehydrogenation of limonene under solvent-free reaction conditions using Vietnamese montmorillonite as an efficient green catalyst....

  14. Experimental and theoretical analysis of asymmetric induction in heterogeneous catalysis: diastereoselective hydrogenation of chiral alpha-hydroxyketones over Pt catalyst.

    Science.gov (United States)

    Busygin, Igor; Taskinen, Antti; Nieminen, Ville; Toukoniitty, Esa; Stillger, Thomas; Leino, Reko; Murzin, Dmitry Yu

    2009-04-01

    Assessing the origin of asymmetric induction in heterogeneously catalyzed hydrogenation is a challenging task. In this work, hydrogenation of a chiral compound, (R)-1-hydroxy-1-phenyl-2-propanone [(R)-PAC], in toluene over cinchonidine modified and unmodified Pt/Al(2)O(3) was studied. To reveal the detailed reaction mechanism and the origin of stereoselectivity in the Pt-catalyzed hydrogenation of the CO double bond, the structures and energies of several adsorption modes of (R)-PAC as well as whole reaction paths for hydrogenation were investigated on Pt(111) by density functional theory (DFT). In agreement with experimental results, the theoretically obtained potential energy profiles for the studied hydrogenation mechanisms implied that (1R,2S)-1-phenyl-1,2-propanediol is formed in excess with respect to the other diastereomeric product diol, (1R,2R)-1-phenyl-1,2-propanediol. Generally, if the elementary hydrogen addition step was thermodynamically more favorable on one of the two diastereotopic faces, it was also kinetically preferred on the same face, and vice versa. Pairwise addition of hydrogen was the most energetically favorable mechanism. Adsorption and hydrogenation of other structurally similar chiral alpha-hydroxyketones, (R)-3-hydroxy-2-butanone and (R)-2-hydroxy-1-cyclohexanone, were also studied computationally on Pt(111). The results showed that cluster model DFT calculations can be used to assess (dia)stereoselectivity in metal-catalyzed hydrogenation of even such complex organic molecules as studied here.

  15. DNA-based hybrid catalysis

    NARCIS (Netherlands)

    Rioz-Martínez, Ana; Roelfes, Gerard

    In the past decade, DNA-based hybrid catalysis has merged as a promising novel approach to homogeneous (asymmetric) catalysis. A DNA hybrid catalysts comprises a transition metal complex that is covalently or supramolecularly bound to DNA. The chiral microenvironment and the second coordination

  16. Supramolecular catalysis: Refocusing catalysis

    NARCIS (Netherlands)

    van Leeuwen, P.W.N.M.; Freixa, Z.; van Leeuwen, P.W.N.M.

    2008-01-01

    This chapter contains sections titled: * Introduction: A Brief Personal History * Secondary Phosphines or Phosphites as Supramolecular Ligands * Host-Guest Catalysis * Ionic Interactions as a Means to Form Heterobidentate Assembly Ligands * Ditopic Ligands for the Construction of Bidentate Phosphine

  17. Asymmetric catalysis in organic synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Reilly, S.D.; Click, D.R.; Grumbine, S.K.; Scott, B.L.; Watkins, J.G.

    1998-11-01

    This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The goal of the project was to prepare new catalyst systems, which would perform chemical reactions in an enantioselective manner so as to produce only one of the possible optical isomers of the product molecule. The authors have investigated the use of lanthanide metals bearing both diolate and Schiff-base ligands as catalysts for the enantioselective reduction of prochiral ketones to secondary alcohols. The ligands were prepared from cheap, readily available starting materials, and their synthesis was performed in a ''modular'' manner such that tailoring of specific groups within the ligand could be carried out without repeating the entire synthetic procedure. In addition, they have developed a new ligand system for Group IV and lanthanide-based olefin polymerization catalysts. The ligand system is easily prepared from readily available starting materials and offers the opportunity to rapidly prepare a wide range of closely related ligands that differ only in their substitution patterns at an aromatic ring. When attached to a metal center, the ligand system has the potential to carry out polymerization reactions in a stereocontrolled manner.

  18. A Highly Efficient Solvent-Free Acetalization of Aldehydes to 1,1 ...

    African Journals Online (AJOL)

    1,1-Diacetates are prepared in excellent yields from aldehydes and acetic anhydride under solvent-free conditions at room temperature in short reaction times using catalytic amount of sulfonic acid functionalized silica (SiO2-Pr-SO3H) which could be easily handled and removed from the mixture of reaction. Keywords: 1 ...

  19. Solvent-free synthesis of nanosized hierarchical sodalite zeolite with a multi-hollow polycrystalline structure

    KAUST Repository

    Zeng, Shangjing

    2016-08-03

    A solvent-free route is developed for preparing nanoscale sodalite zeolite with a multi-hollow structure. Furthermore, the synthesis of nanosized hollow sodalite polycrystalline aggregates with a mesoporous structure and high crystallinity is investigated by adding an organosilane surfactant as a mesopore-generating agent.

  20. A Solvent-Free Base Liberation of a Tertiary Aminoalkyl Halide by Flow Chemistry

    DEFF Research Database (Denmark)

    Pedersen, Michael Jønch; Skovby, Tommy; Mealy, Michael J.

    2016-01-01

    A flow setup for base liberation of 3-(N,N-dimethylamino)propyl chloride hydrochloride and solvent-free separation of the resulting free base has been developed. Production in flow profits from an on-demand approach, useful for labile aminoalkyl halides. The requirement for obtaining a dry product...

  1. Kinetics study of oil extraction from Citrus auranticum L. by solvent-free microwave extraction

    Directory of Open Access Journals (Sweden)

    Heri Septya Kusuma

    2016-05-01

    Full Text Available Citrus and its oil are of high economic and medicinal value because of their multiple uses, such as in the food industry, cosmetics and folk medicine. The aim of this study is to investigate the potential of solvent-free microwave extraction for the extraction of essential oils from Citrus auranticum L. peels. Specifically, this study verifies the kinetics based on second-order model and mechanism of solvent-free microwave extraction of Citrus auranticum L. peels. Solvent-free microwave extraction is used to extract essential oils from Citrus auranticum L. peels. The initial extraction rate, the extraction capacity and the second-order extraction rate constant were calculated using the model. Using a three-step experimental design of the kinetics of oil extraction from Citrus auranticum L. peels by solvent-free microwave extraction, this study showed that the extraction process was based on the second-order extraction model. The initial extraction rate (h, the extraction capacity (CS, the second-order extraction rate constant (k, and coefficient of determination (R2 was 0.7483 g L-1 min-1, 0.7291 g L-1, 1.4075 L g-1 min-1 and 0.9992, respectively.

  2. Preparation of Ultra-fine Calcium Carbonate by a Solvent-free ...

    African Journals Online (AJOL)

    The treatment of calcium chloride with sodium carbonate under solvent-free conditions with a supersonic airflow and at a low heating temperature leads to the synthesis of ultra-fine calcium carbonate. The reaction not only involves mild conditions, a simple operation, and high yields but also gives a high conversion rate.

  3. Preparation of Ultra-fine Calcium Carbonate by a Solvent-free ...

    African Journals Online (AJOL)

    NJD

    2008-09-19

    Sep 19, 2008 ... circulating carbonation7 and absorption spraying.8 In this paper, we report a new solid-state reaction method using solvent-free conditions at low temperature and by application of a super- sonic airflow for the preparation of ultra-fine calcium carbonate. This new method could be extended to large-scale ...

  4. Solvent-free catalysed synthesis of tetrahydropyran odorants: the role of SiO

    Energy Technology Data Exchange (ETDEWEB)

    Macedo, Alexandra; Wendler, Edison P.; Zukerman-Schpector, Julio, E-mail: alcindo@iq.usp.b [Universidade Federal de Sao Carlos (DQ/UFSCar), SP (Brazil). Dept. de Quimica; Santos, Alcindo A. dos [Universidade de Sao Paulo (IQ/USP), SP (Brazil). Inst. de Quimica; Tiekink, Edward R.T. [University of Malaya, Kuala Lumpur (Malaysia). Dept. of Chemistry

    2010-07-01

    An efficient, green and solvent-free catalysed Prins-cyclization reaction based on the simple grinding of an aldehyde and a homoallylic alcohol in the presence of catalytic amount of p-TSA on silica gel is reported. By this protocol were synthesized tetrahydropyran odorants including commercial Florol and Clarycet, in one and two steps respectively. (author)

  5. Synthesis of Some Aryl Chalcones Using Silica-Sulphuric Acid Reagent under Solvent Free Conditions

    OpenAIRE

    G. Thirunarayanan; Vanangamudi, G.

    2007-01-01

    There are two series of α, β-unsaturated ketones derived form Biphenyl and 9H-Fluorenyl, and ketones with various substituted benzaldehydes under solvent free conditions using silica-sulphuric acid as a reagent in an oven. The catalyst silica is reusable and the yields of chalcones are more than 90%. These chalcones are characterized by physical constants and spectral data.

  6. H 2 O 2-HBr: A metal-free and organic solvent-free reagent system ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences; Volume 121; Issue 2. H2O2-HBr: A metal-free and organic solvent-free reagent system for the synthesis of arylaldehydes from methylarenes. Mohammad Ghaffarzadeh Mohammad Bolourtchian Kourosh Tabar-Heydar Iman Daryaei Farshid Mohsenzadeh. Full Papers Volume ...

  7. Solvent-Free Wittig Reaction: A Green Organic Chemistry Laboratory Experiment

    Science.gov (United States)

    Leung, Sam H.; Angel, Stephen A.

    2004-01-01

    Some Wittig reactions can be carried out by grinding the reactants in a mortar with a pestle for about 20 minutes, as per investigation. A laboratory experiment involving a solvent-free Wittig reaction that can be completed in a three-hour sophomore organic chemistry laboratory class period, are developed.

  8. Solvent-free porous framework resulted from 3D entanglement of 1D zigzag coordination polymer

    KAUST Repository

    Kole, Goutam Kumar Umar

    2010-01-01

    A solvent-free porous metal organic framework is constructed by the 3D entanglement of 1D zigzag coordination polymeric chains. The role of solvents and the effect of reaction conditions on such unique entanglement are addressed. © 2010 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.

  9. Mono lacunary phosphomolybdate supported on MCM-41: synthesis, characterization and solvent free aerobic oxidation of alkenes and alcohols.

    Science.gov (United States)

    Narkhede, Nilesh; Patel, Anjali; Singh, Sukriti

    2014-02-14

    A new catalyst comprising monolacunary phosphomolybdate and MCM-41 was synthesized and characterized by different physicochemical techniques. The catalytic activity was evaluated by carrying out solvent free aerobic oxidation of alkenes and alcohols. The catalyst showed 60% conversion of styrene and 28% conversion of benzyl alcohol. The superiority of the present catalytic system lies in obtaining better conversion under solvent free and aerobic conditions.

  10. Lipase-catalysed ester synthesis in solvent-free oil system: is it esterification or transesterification?

    Science.gov (United States)

    Sun, Jingcan; Yu, Bin; Curran, Philip; Liu, Shao-Quan

    2013-12-01

    Ester synthesis was carried out in a solvent-free system of lipase, coconut oil and ethanol or fusel alcohols to ascertain the reaction mechanism. During ester formation, octanoic and decanoic acids increased initially and then decreased gradually, indicating that ester production was a two-step reaction consisting of hydrolysis and esterification, rather than alcoholysis. With ethanol as the alcohol substrate, added butyric acid inhibited ester synthesis. However, when fusel alcohols were used as the alcohol substrate, no significant inhibitory effect by butyric acid was observed. Added octanoic acid did not show any adverse effect on the synthesis of corresponding esters. The results suggest that polarity of the reactants determines lipase activity. This study provides the first evidence on the mechanism of immobilised lipase-catalysed ester synthesis in a solvent-free system involving both hydrolysis and esterification. Copyright © 2013 Elsevier Ltd. All rights reserved.

  11. Solvent-Free Production of Bioflavors by Enzymatic Esterification of Citronella (Cymbopogon winterianus) Essential Oil.

    Science.gov (United States)

    Paroul, Natália; Grzegozeski, Luana Paula; Chiaradia, Viviane; Treichel, Helen; Cansian, Rogério L; Oliveira, J Vladimir; de Oliveira, Débora

    2012-01-01

    Enzymatic esterification of citronella essential oil towards the production of geranyl and citronellyl esters may present great scientific and technological interest due to the well-known drawbacks of the chemical-catalyzed route. In this context, this work reports the maximization of geranyl and citronellyl esters production by esterification of oleic and propionic acids in a solvent-free system using a commercial immobilized lipase as catalyst. Results of the reactions showed that the strategy adopted for the experimental design proved to be useful in evaluating the effects of the studied variables on the reaction conversion using Novozym 435 as catalyst. The operating conditions that maximized the production of each ester were determined, leading, in a general way, to conversions of about 90% for all systems. New experimental data on enzymatic esterification of crude citronella essential oil for geranyl and citronellyl esters production in solvent-free system are reported in this work.

  12. Predicting the Disorder–Order Transition of Solvent-Free Nanoparticle–Organic Hybrid Materials

    KAUST Repository

    Yu, Hsiu-Yu

    2013-07-02

    The transition from a disordered to a face-centered-cubic phase in solvent-free oligomer-tethered nanoparticles is predicted using a density-functional theory for model hard spheres with tethered bead-spring oligomers. The transition occurs without a difference of volume fraction for the two phases, and the phase boundary is influenced by the loss of oligomer configurational entropy relative to an ideal random system in one phase compared with the other. When the particles are localized in the ordered phase, the cooperation of the oligomers in filling the space is hindered. Therefore, shorter oligomers feel a stronger entropic penalty in the ordered solid and favor the disordered phase. Strikingly, we found that the solvent-free system has a later transition than hard spheres for all investigated ratios of oligomer radius of gyration to particle radius. © 2013 American Chemical Society.

  13. Solvent-Free Toner Printing of Organic Semiconductor Layer in Flexible Thin-Film Transistors

    Science.gov (United States)

    Sakai, Masatoshi; Koh, Tokuyuki; Toyoshima, Kenji; Nakamori, Kouta; Okada, Yugo; Yamauchi, Hiroshi; Sadamitsu, Yuichi; Shinamura, Shoji; Kudo, Kazuhiro

    2017-07-01

    A solvent-free printing process for printed electronics is successfully developed using toner-type patterning of organic semiconductor toner particles and the subsequent thin-film formation. These processes use the same principle as that used for laser printing. The organic thin-film transistors are prepared by electrically distributing the charged toner onto a Au electrode on a substrate film, followed by thermal lamination. The thermal lamination is effective for obtaining an oriented and crystalline thin film. Toner printing is environmentally friendly compared with other printing technologies because it is solvent free, saves materials, and enables easy recycling. In addition, this technology simultaneously enables both wide-area and high-resolution printing.

  14. Montmorillonite Clay-Promoted, Solvent-Free Cross-Aldol Condensations under Focused Microwave Irradiation

    Directory of Open Access Journals (Sweden)

    Damiano Rocchi

    2014-06-01

    Full Text Available An environmentally benign, clean and general protocol was developed for the synthesis of aryl and heteroaryl trans-chalcones. This method involved solvent-free reaction conditions under microwave irradiation in the presence of a clay-based catalyst, and afforded the target compounds in good yields and short reaction times. Furthermore, the same conditions allowed the synthesis of symmetrical, diarylmethylene-α,β-unsaturated ketones from aromatic aldehydes and ketones.

  15. Solvent-Free Synthesis of Flavour Esters through Immobilized Lipase Mediated Transesterification

    OpenAIRE

    Garlapati, Vijay Kumar; Banerjee, Rintu

    2013-01-01

    The synthesis of methyl butyrate and octyl acetate through immobilized Rhizopus oryzae NRRL 3562 lipase mediated transesterification was studied under solvent-free conditions. The effect of different transesterification variables, namely, molarity of alcohol, reaction time, temperature, agitation, addition of water, and enzyme amount on molar conversion (%) was investigated. A maximum molar conversion of 70.42% and 92.35% was obtained in a reaction time of 14 and 12 h with the transesterifica...

  16. Solvent-free, visible-light photocatalytic alcohol oxidations applying an organic photocatalyst

    Directory of Open Access Journals (Sweden)

    Martin Obst

    2016-11-01

    Full Text Available A method for the solvent-free photocatalytic conversion of solid and liquid substrates was developed, using a novel rod mill apparatus. In this setup, thin liquid films are realized which is crucial for an effective photocatalytic conversion due to the low penetration depth of light in heterogeneous systems. Several benzylic alcohols were oxidized with riboflavin tetraacetate as photocatalyst under blue light irradiation of the reaction mixture. The corresponding carbonyl compounds were obtained in moderate to good yields.

  17. Solvent-free preparation of co-crystals of phenazine and acridine with vanillin

    Energy Technology Data Exchange (ETDEWEB)

    Braga, Dario, E-mail: dario.braga@unibo.it [Dipartimento di Chimica ' G.Ciamician' , Universita degli studi di Bologna, Via Selmi 2, 40126 Bologna (Italy); Grepioni, Fabrizia; Maini, Lucia; Mazzeo, Paolo P.; Rubini, Katia [Dipartimento di Chimica ' G.Ciamician' , Universita degli studi di Bologna, Via Selmi 2, 40126 Bologna (Italy)

    2010-08-10

    Co-crystals of phenazine and acridine with vanillin have been obtained by solvent-free reaction or thermal treatment of the solid reactants: their structures, thermal behaviour and eutectic formation have been investigated via single crystal X-ray diffraction, differential scanning calorimetry (DSC), variable temperature X-ray powder diffraction and hot-stage microscopy (HSM). Polymorph screening of the reagents has also been carried out.

  18. Triton-B catalyzed, efficient and solvent-free approach for the synthesis of dithiocarbamates

    Directory of Open Access Journals (Sweden)

    Sadaf Zaidi

    2017-09-01

    Full Text Available A novel one-pot, solvent-free method for the synthesis of dithiocarbamates was developed through the reaction of corresponding alkyl halides, amines and carbon disulfide employing catalytic amount of benzyl trimethyl ammonium hydroxide (Triton-B. The reaction conditions are milder with extremely simple work-up procedures than the reported methods, afforded high yields (82-98% of the desired products.

  19. Solvent-free Fabrication of Tissue Engineering Scaffolds with Immiscible Polymer Blends

    OpenAIRE

    Ma, Liang; Jiang, Wei; Li, Wei

    2014-01-01

    A completely organic solvent-free fabrication method is developed for tissue engineering scaffolds by gas foaming of immiscible polylactic acid (PLA) and sucrose blends, followed by water leaching. PLA scaffolds with above 90% porosity and 25–200 μm pore size were fabricated. The pore size and porosity was controlled with process parameters including extrusion temperature and foaming process parameters. Dynamic mechanical analysis showed that the extrusion temperature could be used to control...

  20. Innovative polymeric system (IPS) for solvent-free lipophilic drug transdermal delivery via dissolving microneedles.

    Science.gov (United States)

    Dangol, Manita; Yang, Huisuk; Li, Cheng Guo; Lahiji, Shayan Fakhraei; Kim, Suyong; Ma, Yonghao; Jung, Hyungil

    2016-02-10

    Lipophilic drugs are potential drug candidates during drug development. However, due to the need for hazardous organic solvents for their solubilization, these drugs often fail to reach the pharmaceutical market, and in doing so highlight the importance of solvent free systems. Although transdermal drug delivery systems (TDDSs) are considered prospective safe drug delivery routes, a system involving lipophilic drugs in solvent free or powder form has not yet been described. Here, we report, for the first time, a novel approach for the delivery of every kind of lipophilic drug in powder form based on an innovative polymeric system (IPS). The phase transition of powder form of lipophilic drugs due to interior chemical bonds between drugs and biodegradable polymers and formation of nano-sized colloidal structures allowed the fabrication of dissolving microneedles (DMNs) to generate a powerful TDDS. We showed that IPS based DMN with powder capsaicin enhances the therapeutic effect for treatment of the rheumatic arthritis in a DBA/1 mouse model compared to a solvent-based system, indicating the promising potential of this new solvent-free platform for lipophilic drug delivery. Copyright © 2016 Elsevier B.V. All rights reserved.

  1. Liquefaction of Biopolymers: Solvent-free Liquids and Liquid Crystals from Nucleic Acids and Proteins.

    Science.gov (United States)

    Liu, Kai; Ma, Chao; Göstl, Robert; Zhang, Lei; Herrmann, Andreas

    2017-05-16

    Biomacromolecules, such as nucleic acids, proteins, and virus particles, are persistent molecular entities with dimensions that exceed the range of their intermolecular forces hence undergoing degradation by thermally induced bond-scission upon heating. Consequently, for this type of molecule, the absence of a liquid phase can be regarded as a general phenomenon. However, certain advantageous properties usually associated with the liquid state of matter, such as processability, flowability, or molecular mobility, are highly sought-after features for biomacromolecules in a solvent-free environment. Here, we provide an overview over the design principles and synthetic pathways to obtain solvent-free liquids of biomacromolecular architectures approaching the topic from our own perspective of research. We will highlight the milestones in synthesis, including a recently developed general surfactant complexation method applicable to a large variety of biomacromolecules as well as other synthetic principles granting access to electrostatically complexed proteins and DNA. These synthetic pathways retain the function and structure of the biomacromolecules even under extreme, nonphysiological conditions at high temperatures in water-free melts challenging the existing paradigm on the role of hydration in structural biology. Under these conditions, the resulting complexes reveal their true potential for previously unthinkable applications. Moreover, these protocols open a pathway toward the assembly of anisotropic architectures, enabling the formation of solvent-free biomacromolecular thermotropic liquid crystals. These ordered biomaterials exhibit vastly different mechanical properties when compared to the individual building blocks. Beyond the preparative aspects, we will shine light on the unique potential applications and technologies resulting from solvent-free biomacromolecular fluids: From charge transport in dehydrated liquids to DNA electrochromism to biocatalysis in

  2. Heterogeneous Catalysis.

    Science.gov (United States)

    Vannice, M. A.

    1979-01-01

    Described is a graduate course in catalysis offered at Penn State University. A detailed course outline with 30 lecture topics is presented. A list of 42 references on catalysis used in place of a textbook is provided. (BT)

  3. 21 CFR 182.40 - Natural extractives (solvent-free) used in conjunction with spices, seasonings, and flavorings.

    Science.gov (United States)

    2010-04-01

    ...) SUBSTANCES GENERALLY RECOGNIZED AS SAFE General Provisions § 182.40 Natural extractives (solvent-free) used... use, within the meaning of section 409 of the Act, are as follows: Common name Botanical name of plant...

  4. SOLVENT-FREE FACILE SYNTHESIS OF NOVEL α-TOSYLOXY β-KETO SULFONES USING [HYDROXY(TOSYLOXY)IODO]BENZENE

    Science.gov (United States)

    A facile, general and high yielding protocol for the synthesis of novel α-tosyloxy β-keto sulfones is described utilizing relatively non-toxic, [hydroxy(tosyloxy)iodo]benzene, under solvent-free conditions at room temperature.

  5. Synthesis of 4-Aryl Substituted 3,4-Dihydropyrimidinones Using Silica-chloride Under Solvent Free Conditions

    Directory of Open Access Journals (Sweden)

    M P Kaushik

    2007-07-01

    Full Text Available This paper describes an improved procedure for the efficient and facile synthesis of 4-aryl substituted 3, 4-dihydropyrimidinones under mild reaction conditions with excellent yields using inexpensive silica chloride under solvent free conditions.

  6. Structural requirements for producing solvent-free room temperature liquid fullerenes.

    Science.gov (United States)

    Michinobu, Tsuyoshi; Okoshi, Kensuke; Murakami, Yoshihiko; Shigehara, Kiyotaka; Ariga, Katsuhiko; Nakanishi, Takashi

    2013-04-30

    A new class of solvent-free room temperature liquid fullerenes was synthesized by attaching a single substituent of 1,3,5-tris(alkyloxy)benzene unit to C60 or C70 under the Prato conditions. Although the C60 monoadducts were single components after chromatographic purification, the C70 monoadducts were isomeric mixtures due to the prolate spheroidal π-chromophore. The alkyl chain length of the substituents significantly affected both melting points and rheological behavior of the fullerene derivatives. When the alkyl chains were short, the intermolecular π-π interactions of adjacent fullerene cores led to a melting point higher than room temperature. In contrast, in the case of exceedingly long alkyl chains, such as eicosyl (-C20H41) and docosanyl (-C22H45) groups, the van der Waals interactions among neighboring alkyl chains became dominant. Accordingly, only medium alkyl chain lengths could provide solvent-free fluidic fullerenes with low melting points. The rheological measurements of the liquid fullerenes at 25 °C revealed their unique liquid characteristics; molecular-level friction (or viscosity) and nanometer-scale clustering were noticed. It is generally thought that alkyl chains serve as a stabilizer of the fullerene core units. Thus, a longer chain or higher plasticity of the stabilizers would promote the disturbance of the core-core interactions. It was indeed shown that longer alkyl chains resulted in a lower fluid viscosity. It was also found that metastable solid phases were produced by the noticeable van der Waals interaction between the long alkyl chains especially when a symmetric C60 core was adopted. This interesting finding enabled the comparison of electrochemical activities of the C60 unit between the solvent-free liquid and metastable solid form, which revealed a superior electrochemical activity in the liquid state.

  7. Durability of solvent-free one-step self-etch adhesive under simulated intrapulpal pressure.

    Science.gov (United States)

    Nagi, Shaymaa M

    2015-10-01

    There are different solvents presented in simplified adhesives. Bond-1 SF has been developed, which contains neither water nor organic solvents, in order to eliminate technical issues in terms of evaporation of solvents and concerns for the durability of resin-dentin bond. Thus this study was conducted to evaluate the microtensile bond strength (?TBS) of solvent-free and ethanol-based one-step self-etch adhesives to dentin under simulated intrapulpal pressure (IPP). Occlusal surfaces of human molars were prepared to expose mid-dentin depth. Bond-1SF Solvent-Free SE [SF] and AdperTM easy one adhesives [AE] were applied on dentin specimens. Resin composite build up was done in increments. Then specimens were stored under simulated IPP 20 mmHg, immersed in artificial saliva at 37 ºC for 24 hours (24h) and 6 months (6m). Specimens were sectioned into sticks of (1 mm²) to be tested for (?TBS) using a universal testing machine. Both fractured sections of each stick were inspected using a stereomicroscope at 40× magnification to determine the mode of failure. Data were statistically analyzed by Two-way ANOVA of Variance. There was no statistically significant difference between the mean ?TBS of both [SF] and [AE] adhesives at both aging periods, 24h and 6m (padhesive failure at tooth side. Under simulated IPP solvent-free adhesive [SF] had comparable performance as ethanol-based adhesive [AE] when bonded to dentin substrate. Bond strength, dentin, simulated intrapulpal pressure, self-etch adhesives, solvents.

  8. Development of solvent-free ambient mass spectrometry for green chemistry applications.

    Science.gov (United States)

    Liu, Pengyuan; Forni, Amanda; Chen, Hao

    2014-04-15

    Green chemistry minimizes chemical process hazards in many ways, including eliminating traditional solvents or using alternative recyclable solvents such as ionic liquids. This concept is now adopted in this study for monitoring solvent-free reactions and analysis of ionic liquids, solids, and catalysts by mass spectrometry (MS), without using any solvent. In our approach, probe electrospray ionization (PESI), an ambient ionization method, was employed for this purpose. Neat viscous room-temperature ionic liquids (RTILs) in trace amounts (e.g., 25 nL) could be directly analyzed without sample carryover effect, thereby enabling high-throughput analysis. With the probe being heated, it can also ionize ionic solid compounds such as organometallic complexes as well as a variety of neat neutral solid chemicals (e.g., amines). More importantly, moisture-sensitive samples (e.g., [bmim][AlCl4]) can be successfully ionized. Furthermore, detection of organometallic catalysts (including air-sensitive [Rh-MeDuPHOS][OTf]) in ionic liquids, a traditionally challenging task due to strong ion suppression effect from ionic liquids, can be enabled using PESI. In addition, PESI can be an ideal approach for monitoring solvent-free reactions. Using PESI-MS, we successfully examined the alkylation of amines by alcohols, the conversion of pyrylium into pyridinium, and the condensation of aldehydes with indoles as well as air- and moisture-sensitive reactions such as the oxidation of ferrocene and the condensation of pyrazoles with borohydride. Interestingly, besides the expected reaction products, the reaction intermediates such as the monopyrazolylborate ion were also observed, providing insightful information for reaction mechanisms. We believe that the presented solvent-free PESI-MS method would impact the green chemistry field.

  9. Solvent free one pot synthesis of amidoalkyl naphthols over phosphotungstic acid

    Directory of Open Access Journals (Sweden)

    Divya P. Narayanan

    2017-07-01

    Full Text Available Montmorillonite KSF clay was effectively modified by the encapsulation of phosphotungstic acid into the clay layers via sonication followed by incipient wet impregnation method. The prepared catalysts were characterized by X-ray diffraction (XRD, Fourier-transform infrared spectroscopy (FTIR and scanning electron microscopy (SEM techniques. The catalytic activities of the prepared systems were investigated in the solvent free synthesis of amidoalkyl naphthols by the multicomponent one-pot condensation of an aldehyde, β-naphthol and an amide or urea. Excellent yield, shorter reaction time, easy work-up, and reusability of the catalyst are the main attractions of this green procedure.

  10. Coumarin Derivatives Solvent-Free Synthesis under Microwave Irradiation over Heterogeneous Solid Catalysts

    Directory of Open Access Journals (Sweden)

    Souad Bouasla

    2017-11-01

    Full Text Available A suitable methodology of synthesis of coumarin derivatives by Pechmann reaction over heterogeneous solid acid catalysts in a free solvent media under microwave irradiation is described. Resorcinol, phenol and ethyl acetoacetate were selected as model reactants in the Pechmann condensation. The catalytic activity of several materials—Amberlyst-15, zeolite β and sulfonic acid functionalized hybrid silica—in solvent-free microwave-assisted synthesis of the corresponding coumarin derivatives has been investigated in detail. 7-Hydroxy-4-methylcoumarin and 4-methylcoumarin were obtained in 97% and 43% yields, respectively, over Amberlyst-15. This was the most active catalyst in the Pechmann reaction under studied conditions.

  11. Microwave-Assisted Solvent-Free Synthesis of Zeolitic Imidazolate Framework-67

    Directory of Open Access Journals (Sweden)

    Heng Zhang

    2016-01-01

    Full Text Available A microporous metal-organic framework (MOF, cobalt-based zeolitic imidazolate framework-67 (ZIF-67, was synthesized by the combination of solvent-free hand-mill and microwave irradiation, without any organic solvent and within 30 minutes. The hand-milling process can mix the reactants well by the virtue of high moisture/water absorption capacity of reactants. In addition, the outstanding electromagnetic wave absorption capability of cobalt leads to efficient conversion to MOF structures before carbonization. The obtained ZIF-67 possesses high surface area and micropore volume.

  12. Synthesis and characterization of solvent-free ionic molybdenum disulphide (MoS{sub 2}) nanofluids

    Energy Technology Data Exchange (ETDEWEB)

    Gu, Shu-Ying, E-mail: gushuying@tongji.edu.cn [School of Materials Science and Engineering, Tongji University, Shanghai 201804 (China); Key Laboratory of Advanced Civil Engineering Materials, Ministry of Education, School of Materials Science and Engineering, Tongji University, Shanghai 201804 (China); Gao, Xie-Feng; Zhang, Yi-Han [School of Materials Science and Engineering, Tongji University, Shanghai 201804 (China)

    2015-01-15

    A development of the novel and stable solvent-free ionic MoS{sub 2} nanofluids by a facile and scalable hydrothermal method is presented. The nanofluids were synthesized by surface functionalizing nanoscale MoS{sub 2} from hydrothermal synthesis with a charged corona, and ionically tethering with oligomeric chains as a canopy. The structures and properties of the nanofluids were characterized by Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR, {sup 1}H), differential scanning calorimeter (DSC), thermogravimetric analysis (TGA) and ARES rheometer. The obtained solvent-free nanofluids are homogeneous, stable amber-like fluids with no evidence of phase separation. The nanofluids could be easily dispersed in both aqueous and organic solvents to form transparent and stable liquids due to the ionic nature and the presence of oligomeric polymer chains. It was found that the solvent-free nanofluids with up to 32 wt% inorganic content show Newtonian rheological behaviors due to the high graft density and uniform dispersion of inorganic cores, indicating that the nanofluids would have a stable lubricating performance. As reported in our previous communication, the nanofluids showing lower, more stable friction coefficients of less than 0.1 with self-healing lubricating behaviors. For deeper understanding of the nanofluids, the details of synthesis, chemical structures, rheological behaviors and molecular dynamics of the nanofluids were investigated in details. The rheological behaviors can be tailored by varying the grafting density of the canopy. Dynamic results of the canopy of the MoS{sub 2} nanofluids show that inorganic MoS{sub 2} cores have hindrance effect on the canopy segmental motions above 253 K due to their effect to the mobility of anions and the departing-recombining motions between the paired cations and anions. - Highlights: • A development of the novel synthesis of solvent-free MoS{sub 2} nanofluids is presented. • The rheological

  13. Indium(III)-catalyzed synthesis of N-substituted pyrroles under solvent-free conditions

    OpenAIRE

    Chen, Jiu-Xi; Liu, Miao-Chang; Yang, Xiao-Liang; Ding, Jin-Chang; Wu, Hua-Yue

    2008-01-01

    A variety of N-substituted pyrroles have been synthesized by reacting γ-diketones (R¹C(O)CH2CH2C(O)R²: R¹, R² = Me, Ph) with amines (RNH2: R=Alkyl, Aryl, TsNH) or diamines (1,6-diaminohexane and 1,2-diaminoethane) in the presence of indium tribromide, indium trichloride or indium trifluoromethanesulfonate at room temperature under solvent-free conditions. The experiment protocol features simple operations, and the products are isolated in high to excellent yields (81-98%). Vários pirróis N...

  14. Direct sp(3)C-H acroleination of N-aryl-tetrahydroisoquinolines by merging photoredox catalysis with nucleophilic catalysis.

    Science.gov (United States)

    Feng, Zhu-Jia; Xuan, Jun; Xia, Xu-Dong; Ding, Wei; Guo, Wei; Chen, Jia-Rong; Zou, You-Quan; Lu, Liang-Qiu; Xiao, Wen-Jing

    2014-04-07

    Sequence catalysis merging photoredox catalysis (PC) and nucleophilic catalysis (NC) has been realized for the direct sp(3) C-H acroleination of N-aryl-tetrahydroisoquinoline (THIQ). The reaction was performed under very mild conditions and afforded products in 50-91% yields. A catalytic asymmetric variant was proved to be successful with moderate enantioselectivities (up to 83 : 17 er).

  15. Tuning of Activated Carbon for Solvent-Free Oxidation of Cyclohexane

    Directory of Open Access Journals (Sweden)

    Mohammad Sadiq

    2017-01-01

    Full Text Available Activated carbon (AC was prepared from carbonization of phosphoric acid soaked peanut shell at 380°C under inert atmosphere followed by activation with hydrogen peroxide. The AC was characterized by SEM, EDX, FTIR, TGA, and BET surface area and pore size analyzer. The potential of AC as a catalyst for solvent-free oxidation of cyclohexane to cyclohexanol and cyclohexanone (the mixture is known as KA oil in the presence of molecular oxygen at moderate temperature was investigated in a self-designed double-walled three-necked batch reactor. The effect of different reaction parameters/additive was optimized. The maximum productivity value (2.14 mmolg−1 h−1, without base, and 4.85 mmolg−1 h−1, with 0.2 mmol NaOH of the desired product was achieved under optimal reaction parameters: vol 12.5 mL, cat 0.4 g, time 14 h, oxygen flow 40 mL/min (pO2 760 Torr, stirring 1100 rpm, and temp 75°C. The AC shows recyclability for multiple runs without any significant loss in activity. Thus, the AC can be an efficient catalyst, due to low cost, ease of synthesis, easy recovery, nonleaching, and recyclability for multiple uses for the solvent-free oxidation of cyclohexane.

  16. Solvent-Free Synthesis of Flavour Esters through Immobilized Lipase Mediated Transesterification

    Directory of Open Access Journals (Sweden)

    Vijay Kumar Garlapati

    2013-01-01

    Full Text Available The synthesis of methyl butyrate and octyl acetate through immobilized Rhizopus oryzae NRRL 3562 lipase mediated transesterification was studied under solvent-free conditions. The effect of different transesterification variables, namely, molarity of alcohol, reaction time, temperature, agitation, addition of water, and enzyme amount on molar conversion (% was investigated. A maximum molar conversion of 70.42% and 92.35% was obtained in a reaction time of 14 and 12 h with the transesterification variables of 0.6 M methanol in vinyl butyrate and 2 M octanol in vinyl acetate using 80 U and 60 U immobilized lipase with the agitation speed of 200 rpm and 0.2% water addition at 32°C and 36°C for methyl butyrate and octyl acetate, respectively. The immobilized enzyme has retained good relative activity (more than 95% up to five and six recycles for methyl butyrate and octyl acetate, respectively. Hence, the present investigation makes a great impingement in natural flavour industry by introducing products synthesized under solvent-free conditions to the flavour market.

  17. Solvent-Free Synthesis of Flavour Esters through Immobilized Lipase Mediated Transesterification

    Science.gov (United States)

    Banerjee, Rintu

    2013-01-01

    The synthesis of methyl butyrate and octyl acetate through immobilized Rhizopus oryzae NRRL 3562 lipase mediated transesterification was studied under solvent-free conditions. The effect of different transesterification variables, namely, molarity of alcohol, reaction time, temperature, agitation, addition of water, and enzyme amount on molar conversion (%) was investigated. A maximum molar conversion of 70.42% and 92.35% was obtained in a reaction time of 14 and 12 h with the transesterification variables of 0.6 M methanol in vinyl butyrate and 2 M octanol in vinyl acetate using 80 U and 60 U immobilized lipase with the agitation speed of 200 rpm and 0.2% water addition at 32°C and 36°C for methyl butyrate and octyl acetate, respectively. The immobilized enzyme has retained good relative activity (more than 95%) up to five and six recycles for methyl butyrate and octyl acetate, respectively. Hence, the present investigation makes a great impingement in natural flavour industry by introducing products synthesized under solvent-free conditions to the flavour market. PMID:23819043

  18. Lipase Mediated Isoamyl Acetate Synthesis in Solvent-Free System Using Vinyl Acetate as Acyl Donor

    Directory of Open Access Journals (Sweden)

    Annapurna Kumari

    2009-01-01

    Full Text Available Synthesis of isoamyl acetate, a flavour ester extensively used in food industry, has been carried out in a solvent-free system. In the present study, an attempt has been made to enhance the isoamyl acetate synthesis yield by transesterification of isoamyl alcohol with vinyl acetate using immobilized Rhizopus oryzae NRRL 3562 lipase. In the present synthesis, substrates had no inhibitory effect on immobilized lipase. The effects of various reaction parameters on isoamyl acetate synthesis were studied and maximum conversion was achieved at 16 % (by mass per volume of immobilized lipase, 40 °C and 200 rpm. Under these conditions, 8-hour reaction time was sufficient to reach a high ester conversion of 95 % with 0.5 mol/L of isoamyl alcohol. The structure of the transesterified product was confirmed by infrared and nuclear magnetic resonance spectroscopic studies. Immobilized lipase had Km and vmax values of 306.53 mmol/L and 99 µmol/(h·g respectively, for isoamyl acetate synthesis in a solvent-free system.

  19. Cooperative catalysis designing efficient catalysts for synthesis

    CERN Document Server

    Peters, René

    2015-01-01

    Written by experts in the field, this is a much-needed overview of the rapidly emerging field of cooperative catalysis. The authors focus on the design and development of novel high-performance catalysts for applications in organic synthesis (particularly asymmetric synthesis), covering a broad range of topics, from the latest progress in Lewis acid / Br?nsted base catalysis to e.g. metal-assisted organocatalysis, cooperative metal/enzyme catalysis, and cooperative catalysis in polymerization reactions and on solid surfaces. The chapters are classified according to the type of cooperating acti

  20. DNA-based hybrid catalysis.

    Science.gov (United States)

    Rioz-Martínez, Ana; Roelfes, Gerard

    2015-04-01

    In the past decade, DNA-based hybrid catalysis has merged as a promising novel approach to homogeneous (asymmetric) catalysis. A DNA hybrid catalysts comprises a transition metal complex that is covalently or supramolecularly bound to DNA. The chiral microenvironment and the second coordination sphere interactions provided by the DNA are key to achieve high enantioselectivities and, often, additional rate accelerations in catalysis. Nowadays, current efforts are focused on improved designs, understanding the origin of the enantioselectivity and DNA-induced rate accelerations, expanding the catalytic scope of the concept and further increasing the practicality of the method for applications in synthesis. Herein, the recent developments will be reviewed and the perspectives for the emerging field of DNA-based hybrid catalysis will be discussed. Copyright © 2015 Elsevier Ltd. All rights reserved.

  1. Solvent-Free Patterning of Colloidal Quantum Dot Films Utilizing Shape Memory Polymers

    Directory of Open Access Journals (Sweden)

    Hohyun Keum

    2017-01-01

    Full Text Available Colloidal quantum dots (QDs with properties that can be tuned by size, shape, and composition are promising for the next generation of photonic and electronic devices. However, utilization of these materials in such devices is hindered by the limited compatibility of established semiconductor processing techniques. In this context, patterning of QD films formed from colloidal solutions is a critical challenge and alternative methods are currently being developed for the broader adoption of colloidal QDs in functional devices. Here, we present a solvent-free approach to patterning QD films by utilizing a shape memory polymer (SMP. The high pull-off force of the SMP below glass transition temperature (Tg in conjunction with the conformal contact at elevated temperatures (above Tg enables large-area, rate-independent, fine patterning while preserving desired properties of QDs.

  2. Cinnamyl acetate synthesis by lipase-catalyzed transesterification in a solvent-free system.

    Science.gov (United States)

    Geng, Bo; Wang, Mengfan; Qi, Wei; Su, Rongxin; He, Zhimin

    2012-01-01

    Cinnamyl acetate was synthesized using immobilized lipase through transesterification between ethyl acetate and cinnamyl alcohol. In the solvent-free system, ethyl acetate acted as not only the acyl donor but also as the solvent of cinnamyl alcohol. Conversion (90.06%) was achieved after 3 H when transesterification was carried out at ethyl acetate/cinnamyl alcohol 15:1, 2.67 g L of lipase (Novozym 435) loading, and 40°C. Excellent stability and reusability of the enzyme resulted from the moderate reaction system. Kinetic studies showed that the Michaelis constants for ethyl acetate and cinnamyl alcohol and the inhibition constant of cinnamyl alcohol were 2.241, 206.82, and 0.461 mmol L⁻¹, respectively, which indicated that the reaction complied with the Ping-Pong Bi-Bi mechanism, with the inhibition of cinnamyl alcohol on lipase. Copyright © 2012 International Union of Biochemistry and Molecular Biology, Inc.

  3. The Reactivity of HNOx Species in Solvent-Free, Aqueous Media and Biological Systems

    Science.gov (United States)

    Francisco, Joseph S.; Dixon, David A.; Feller, David; Zhan, Chang-Guo

    2002-03-01

    The hydronitrogen oxides (HNO_x) have important and different chemical functions in aqueous media under biological conditions. HNO can act as a potent cytotoxic agent that causes double-stranded breaks in DNA. It has been proposed that peroxynitrous acid (HOONO), which forms after protonation of the peroxynitrite ion (ONOO^-), a potent oxidant of biomolecules. We report results of fundamental chemical and energetic properties of HNOx (x = 1-3) in solvent-free (gas phase) and in aqueous solvent environments. It is critical to get the gas phase properties for these molecules correct before evaluating solution corrections. These data are used to evaluate the reactivity toward biomolecules. New possibilities for the involvement of nitroxyl and peroxynitrite will be discussed.

  4. Enzymatic coproduction of biodiesel and glycerol carbonate from soybean oil in solvent-free system.

    Science.gov (United States)

    Go, A-Ra; Lee, Youngrak; Kim, Young Hwan; Park, Sehkyu; Choi, Joongso; Lee, Jinwon; Han, Sung Ok; Kim, Seung Wook; Park, Chulhwan

    2013-08-15

    The enzymatic coproduction of biodiesel and glycerol carbonate by transesterification of soybean oil and dimethyl carbonate (DMC) has been studied in a solvent-free system. The effects on biodiesel and glycerol carbonate conversion of reaction conditions including the kind of enzyme, the amount of enzyme, the molar ratio of DMC to soybean oil, the reaction temperature, and water addition were investigated. The optimal conditions for biodiesel and glycerol carbonate were 20% Novozym 435, 10:1 molar ratio of DMC to soybean oil, and 0.7% water addition. Under these conditions, the conversions of 96.4% biodiesel and 92.1% glycerol carbonate have been achieved after 48h. Copyright © 2013 Elsevier Inc. All rights reserved.

  5. Solvent-free synthesis of three layered manganese sulfate-oxalates with different pore apertures

    Science.gov (United States)

    Shi, Jingyu; Guo, Furong; Yang, Meng; Zeng, Hongmei; Lin, Zhien

    2018-01-01

    Three manganese sulfate-oxalates, namely, H2pip·Mn2(SO4)2(ox)(H2O)2·2H2O (1), H3ipaṡMn2(SO4)(ox)2.5·H2O (2), and H3dptaṡMn2(SO4)2(ox)1.5(H2O)3 (3), were prepared under solvent-free conditions, where pip = piperazine, ox = oxalate, ipa = 3,3‧-iminobis(N,N-dimethylpropylamine), and dpta = dipropylenetriamine. These compounds have different layered structures intercalated with organic cations. Their pore apertures range from small 8-membered ring (8 MR) to large 12 MR and extra-large 20 MR. The temperature dependence of the magnetic susceptibility of these compounds were also investigated.

  6. Bromodimethylsulfonium bromide (BDMS) mediated dithioacetalization of carbohydrates under solvent-free conditions.

    Science.gov (United States)

    Khan, Abu T; Khan, Md Musawwer

    2010-10-13

    A variety of diethyl dithioacetals of sugars can be prepared in very good yields by the reaction of various monosaccharides with ethanethiol in the presence of 3 mol% bromodimethylsulfonium bromide (BDMS) at 0-5°C. Similarly, dipropyl dithioacetal derivatives can also be obtained in good yields using propanethiol under identical reaction conditions. These dithioacetal derivatives were characterized by per-O-acetylation using silica gel-supported perchloric acid. The significant features of the present protocol are good-to-excellent yields, mild, clean, and solvent-free reaction conditions. This method is extremely suitable for the large-scale preparation of dithioacetal derivatives of various sugars. Copyright © 2010 Elsevier Ltd. All rights reserved.

  7. Microwave Synthesis Under Solvent-Free Conditions and Spectral Studies of Some Mesoporphyrinic Complexes

    Directory of Open Access Journals (Sweden)

    Rica Boscencu

    2012-05-01

    Full Text Available A series of A3B and A4 type mesoporphyrinic complexes were synthesized with superior yields using microwave irradiation under solvent-free conditions. The structures of the complexes were confirmed using elemental analysis, FT-IR, UV-Vis, EPR and NMR spectral data. The influence of environmental polarity on spectral properties of the mesoporphyrinic complexes was investigated. The obtained results indicate that the shape of absorption and fluorescence spectra does not depend on the solvent polarity under the experimental conditions used. The small shifts of the absorption and emission maximums that occur by increasing of solvent polarity reflects the physical interaction between the porphyrinic substituents and the solvent molecules.

  8. Olive oil glycero lysis with the immobilized lipase Candida antarctica in a solvent free system

    Energy Technology Data Exchange (ETDEWEB)

    Singh, A. K.; Mukhopadhyay, M.

    2012-11-01

    In the present work, the solvent free lipase glycerolysis of olive oil for the production of monoglyceride (MG) and diglyceride (DG) with an immobilized Lipase B Candida antarctica was studied. The experiments were performed in batch mode by varying different process parameters. The Results showed that the MG and DG yields were dependent on operating conditions such as time, temperature, glycerol/ oil molar ratio, enzyme concentration and the water content in glycerol. The optimum operating time for maximum MG, 26 wt% and DG, 30 wt% production was 3h. The initial reaction rate was studied by varying different process parameters for 1h. The initial reaction rate increased at 30 degree centigrade temperature, 2:1 glycerol/oil molar ratio, 3.5% (w/w) water content in glycerol and 0.015g of enzyme loading. Comparative data for MG and DG yields for different oils and enzyme combinations were presented.

  9. Structure of solvent-free grafted nanoparticles: Molecular dynamics and density-functional theory

    KAUST Repository

    Chremos, Alexandros

    2011-01-01

    The structure of solvent-free oligomer-grafted nanoparticles has been investigated using molecular dynamics simulations and density-functional theory. At low temperatures and moderate to high oligomer lengths, the qualitative features of the core particle pair probability, structure factor, and the oligomer brush configuration obtained from the simulations can be explained by a density-functional theory that incorporates the configurational entropy of the space-filling oligomers. In particular, the structure factor at small wave numbers attains a value much smaller than the corresponding hard-sphere suspension, the first peak of the pair distribution function is enhanced due to entropic attractions among the particles, and the oligomer brush expands with decreasing particle volume fraction to fill the interstitial space. At higher temperatures, the simulations reveal effects that differ from the theory and are likely caused by steric repulsions of the expanded corona chains. © 2011 American Institute of Physics.

  10. Facile synthesis of symmetrical bis(benzhydryl)ethers using p-toluenesulfonyl chloride under solvent-free conditions

    Science.gov (United States)

    2013-01-01

    Background The benzhydryl ether moiety is widely distributed in nature and constitutes a key structural motif in numerous molecules of significant biological potential and of prospective clinical uses. Solvent-free and cost-effective facile synthesis of symmetrical bis(benzhydryl)ethers is, thus, much desirable. Results A simple and efficient method for the facile synthesis of symmetrical bis(benzhydryl)ethers directly from the corresponding benzhydrols has been developed using a catalytic amount of p-toluenesulfonyl chloride (5 mol%) at an oil bath temperature of 110°C under solvent-free conditions. Conclusions Operational simplicity, low reagent loading, high product yields, short reaction time, and solvent-free conditions are the notable advantages of the present method. PMID:23414667

  11. Solvent free low-melt viscosity imide oligomers and thermosetting polymide composites

    Science.gov (United States)

    Chuang, Chun-Hua (Inventor)

    2012-01-01

    .[.This invention relates to the composition and a solvent-free process for preparing novel imide oligomers and polymers specifically formulated with effective amounts of a dianhydride such as 2,3,3',4-biphenyltetra carboxylic dianydride (a-BPDA), at least one aromatic diamine and an endcapped of 4-phenylethynylphthalic anhydride (PEPA) or nadic anhydride to produce imide oligomers that possess a low-melt viscosity of 1-60 poise at 260-280.degree. C. When the imide oligomer melt is cured at about 371.degree. C. in a press or autoclave under 100-500 psi, the melt resulted in a thermoset polyimide having a glass transition temperature (T.sub.g) equal to and above 310.degree. C. A novel feature of this process is that the monomers; namely the dianhydrides, diamines and the endcaps, are melt processable to form imide oligomers at temperatures ranging between 232-280.degree. C. (450-535.degree. F.) without any solvent. These low-melt imide oligomers can be easily processed by resin transfer molding (RTM), vacuum-assisted resin transfer molding (VARTM) or the resin infusion process with fiber preforms e.g. carbon, glass or quartz preforms to produce polyimide matrix composites with 288-343.degree. C. (550-650.degree. F.) high temperature performance capability..]. .Iadd.This invention relates to compositions and a solvent-free reaction process for preparing imide oligomers and polymers specifically derived from effective amounts of dianhydrides such as 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA), at least one aromatic polyamine and an end-cap such as 4-phenylethynyphthalic anhydride (PEPA) or nadic anhydride to produce imide oligomers that possess a low-melt viscosity of 1-60 poise at 260.degree. C.-280.degree. C..Iaddend.

  12. A series of phenyl sulfonate metal coordination polymers as catalysts for one-pot Biginelli reactions under solvent-free conditions.

    Science.gov (United States)

    Wang, Jin-Hua; Tang, Gui-Mei; Wang, Yong-Tao; Cui, Yue-Zhi; Wang, Jun-Jie; Ng, Seik Weng

    2015-10-28

    Three new metal coordination polymers, namely, [Co(DPP)2(H2O)2]·(BS)2·2H2O (1), [Co(DPP)2(H2O)2]·(ABS)2·2H2O (2) and [Co(DPP)2(MBS)2] (3) [DPP = 1,3-di(pyridin-4-yl)propane, BS = phenyl sulfonic acid, ABS = p-aminobenzene sulfonic acid, MBS = p-methylbenzene sulfonic acid] were obtained under hydrothermal conditions. Complexes 1-3 were structurally characterized using X-ray single-crystal diffraction, XRD and IR spectroscopy. Both complexes 1 and 2 display a 1D tape structure. Meanwhile, complex 3 exhibits a 2D layer and further stacks via C-Hπ interactions to generate a three-dimensional supramolecular architecture. These three metal coordination polymers have been applied as catalysts for the green synthesis of a variety of 3,4-dihydropyrimidin-2(1H)-ones under solvent-free conditions through the Biginelli reaction. Interestingly, the catalysis products have been obtained in high yields under eco-friendly synthesis conditions.

  13. Marginal Microleakage and Morphological Characteristics of a Solvent-Free One-Step Self-Etch Adhesive (B1SF)

    OpenAIRE

    Maryam Khoroushi; Farinaz Shirban; Mohammadreza Shirban

    2013-01-01

    Objective: In recent years, newly developed solvent-free dental adhesives have been introduced. The aim of this study was to evaluate the marginal integrity of a new one-step solvent-free self-etch adhesive and to compare it with a commonly used two-step self-etch adhesive as the gold standard. Materials and Methods: Class V cavities (2?4?1.5 mm) were prepared on the buccal aspects of 28 human premolars. The cervical margins of the cavity preparations were placed 1 mm apical to the CEJ. Clear...

  14. Comparison of microwave hydrodistillation and solvent-free microwave extraction of essential oil from Melaleuca leucadendra Linn

    Science.gov (United States)

    Ismanto, A. W.; Kusuma, H. S.; Mahfud, M.

    2017-12-01

    The comparison of solvent-free microwave extraction (SFME) and microwave hydrodistillation (MHD) in the extraction of essential oil from Melaleuca leucadendra Linn. was examined. Dry cajuput leaves were used in this study. The purpose of this study is also to determine optimal condition (microwave power). The relative electric consumption of SFME and MHD methods are both showing 0,1627 kWh/g and 0,3279 kWh/g. The results showed that solvent-free microwave extraction methods able to reduce energy consumption and can be regarded as a green technique for extraction of cajuput oil.

  15. Efficient synthesis of sulfonamide derivatives on solid supports catalyzed using solvent-free and microwave-assisted methods

    Energy Technology Data Exchange (ETDEWEB)

    Camargo-Ordonez, Argelia; Moreno-Reyes, Christian; Olazaran-Santibanez, Fabian; Martinez-Hernandez, Sheila; Bocanegra-Garcia, Virgilio; Rivera, Gildardo [Universidad Autonoma de Tamaulipas, Reynosa (Mexico). Dep. de Farmacia y Quimica Medicinal

    2011-07-01

    In this work we report the synthesis of sulfonamide derivatives using a conventional procedure and with solid supports, such as silica gel, florisil, alumina, 4A molecular sieves, montmorillonite KSF, and montmorillonite K10 using solvent-free and microwave-assisted methods. Our results show that solid supports have a catalytic activity in the formation of sulfonamide derivatives. We found that florisil, montmorillonite KSF, and K10 could be used as inexpensive alternative catalysts that are easily separated from the reaction media. Additionally, solvent-free and microwave-assisted methods were more efficient in reducing reaction time and in increasing yield. (author)

  16. Heterogeneous Catalysis.

    Science.gov (United States)

    Miranda, R.

    1989-01-01

    Described is a heterogeneous catalysis course which has elements of materials processing embedded in the classical format of catalytic mechanisms and surface chemistry. A course outline and list of examples of recent review papers written by students are provided. (MVL)

  17. Characterisation of the interactions between substrate, copper(II) complex and DNA and their role in rate acceleration in DNA-based asymmetric catalysis.

    Science.gov (United States)

    Draksharapu, Apparao; Boersma, Arnold J; Browne, Wesley R; Roelfes, Gerard

    2015-02-28

    Interactions of the azachalcone derived substrate Aza with copper(II) complexes in the presence and absence of st-DNA were studied in detail by UV/Vis absorption, EPR and Raman and (UV and vis) resonance Raman spectroscopies. The binding of Aza to the Lewis acidic copper(II) complexes, which results in activation of the substrate, was established spectroscopically. It was shown that the binding of Aza differs between Cu(II)dmbpy and Cu(II)terpy, consistent with the observed differences in catalytic asymmetric Diels-Alder reactions with regard to both the rate and enantiomeric preference. Finally, it was shown that DNA has a major beneficial effect on the binding of Aza to the copper(II) complex due to the fact that both bind to the DNA. The result is a high effective molarity of both the copper complexes and the Aza substrate, which leads to a significant increase in binding of Aza to the copper(II) complex. This effect is a key reason for the observed rate acceleration in the catalyzed reactions brought about by the presence of DNA.

  18. Nafion®-catalyzed microwave-assisted Ritter reaction: An atom-economic solvent-free synthesis of amides

    Science.gov (United States)

    An atom-economic solvent-free synthesis of amides by the Ritter reaction of alcohols and nitriles under microwave irradiation is reported. This green protocol is catalyzed by solid supported Nafion®NR50 with improved efficiency and reduced waste production.

  19. A FACILE ONE-POT SYNTHESIS OF β-KETO SULFONES FROM KETONES UNDER SOLVENT-FREE CONDITIONS

    Science.gov (United States)

    An easy solvent-free method is described for the conversion of ketones into β-keto sulfones in high yields that involves in situ generation of α-tosyloxyketones followed by nucleophilic substitution with sodium arene sulfinate in presence of tetra-butylammonium bromide at ...

  20. Three component, one-pot synthesis of amidoalkyl naphthols using polyphosphate ester under solvent-free conditions

    Directory of Open Access Journals (Sweden)

    Hassan Moghanian

    2014-04-01

    Full Text Available Amidoalkyl naphthols are synthesized via a simple, one-pot, three-component reaction between aldehydes, 2-naphthol and amides or ureas using polyphosphate ester (PPE as a reaction mediator under solvent-free conditions in good to excellent yields. High yields, short reaction time, easy work-up, elimination of solvents and toxic catalysts are the advantages of this procedure.

  1. Three component, one-pot synthesis of amidoalkyl naphthols using polyphosphate ester under solvent-free conditions

    OpenAIRE

    Moghanian, Hassan; Ebrahimi, Sattar

    2014-01-01

    Amidoalkyl naphthols are synthesized via a simple, one-pot, three-component reaction between aldehydes, 2-naphthol and amides or ureas using polyphosphate ester (PPE) as a reaction mediator under solvent-free conditions in good to excellent yields. High yields, short reaction time, easy work-up, elimination of solvents and toxic catalysts are the advantages of this procedure.

  2. Fly-ash:H2SO4 catalyzed solvent free efficient synthesis of some aryl chalcones under microwave irradiation

    Science.gov (United States)

    Thirunarayanan, G.; Mayavel, P.; Thirumurthy, K.

    2012-06-01

    Some 2E aryl chalcones have been synthesized using greener catalyst Fly-ash:H2SO4 assisted solvent free environmentally benign Crossed-Aldol reaction. The yields of chalcones are more than 90%. The synthesized chalcones are characterized by their physical constants and spectral data.

  3. A Solvent-Free, One-Step, One-Pot Gewald Reaction for Alkyl-aryl Ketones via Mechanochemistry

    Directory of Open Access Journals (Sweden)

    William C. Shearouse

    2014-04-01

    Full Text Available Herein, we report on the solvent-free synthesis of 2-aminothiophenes via the Gewald reaction. Utilizing high speed ball milling conditions, we discovered the Gewald reaction can be catalytic in base, and conducted under aerobic conditions. Using thermal heat in tandem with the mixer/mill significantly increases the rate of reaction.

  4. A Solvent-Free, One-Step, One-Pot Gewald Reaction for Alkyl-aryl Ketones via Mechanochemistry

    OpenAIRE

    William C. Shearouse; Maxwell Z. Shumba; James Mack

    2014-01-01

    Herein, we report on the solvent-free synthesis of 2-aminothiophenes via the Gewald reaction. Utilizing high speed ball milling conditions, we discovered the Gewald reaction can be catalytic in base, and conducted under aerobic conditions. Using thermal heat in tandem with the mixer/mill significantly increases the rate of reaction.

  5. A novel and organic solvent-free preparation of solid lipid nanoparticles using natural biopolymers as emulsifier and stabilizer.

    Science.gov (United States)

    Xue, Jingyi; Wang, Taoran; Hu, Qiaobin; Zhou, Mingyong; Luo, Yangchao

    2017-10-05

    In this work, a new and novel organic solvent-free and synthetic surfactant-free method was reported to fabricate stable solid lipid nanoparticles (SLNs) from stearic acid, sodium caseinate (NaCas) and pectin, as well as water. Melted stearic acid was directly emulsified into an aqueous phase containing NaCas and pectin, followed by pH adjustment and thermal treatment to induce the formation of a compact and dense polymeric coating which stabilized SLNs. The preparation procedures and formulations were comprehensively optimized. The inter- and intra-molecular interactions among three ingredients were characterized by fluorescence and Fourier transform infrared spectroscopies. The stability of as-prepared SLNs was evaluated under simulated gastrointestinal conditions, and compared with traditional SLNs prepared with organic solvents. Our results revealed that the SLNs prepared from this organic solvent-free method had superior physicochemical properties over the traditional SLNs, including smaller size and better stability. Furthermore, redispersible SLNs powders were obtained by nano spray drying, but only the SLNs prepared by organic solvent-free method had sub-micron scale, uniform and spherical morphology. The organic solvent-free preparation method was proved to be a promising approach to prepare stable and uniform SLNs for potential oral delivery applications. Copyright © 2017 Elsevier B.V. All rights reserved.

  6. Microstructure of polyacrylonitrile-based activated carbon fibers prepared from solvent-free coagulation process

    Directory of Open Access Journals (Sweden)

    Norhaniza Yusof

    2016-02-01

    Full Text Available Polyacrylonitrile precursor fibers prepared using a solvent-free coagulation process were stabilized, carbonized, and physically activated by carbon dioxide into activated carbon fibers (ACFs. The activation temperature varied from 600 to 900 °C while the activation time was 1 h. Atomic force microscopy was used to observe the surface morphology, as well as the surface roughness of the ACFs. Higher pyrolysis temperature formed rougher surfaces, and increased the pore sizes. Meanwhile, Fourier transform infrared spectroscopy revealed more conversion of oxygen containing functional groups to carbonaceous materials as the activation temperature increased. Moreover, the microstructure properties were thoroughly characterized by the X-ray photoelectron spectroscopy (XPS and X-ray diffraction (XRD studies. XRD analysis showed that the activation of the ACFs shrank the ordered structure, reducing the D-spacing from 0.358 to 0.347 nm for the fibers prepared at activation temperatures of 600 to 900 °C. Meanwhile, XPS analysis concluded that that the oxygen containing functional groups were still retained even at high activation temperatures while the nitrogen containing functional groups were reduced during the high temperature activation in the CO2 atmosphere.

  7. Modeling, Simulation, and Kinetic Studies of Solvent-Free Biosynthesis of Benzyl Acetate

    Directory of Open Access Journals (Sweden)

    Vijay Kumar Garlapati

    2013-01-01

    Full Text Available Solvent-free biosynthesis of benzyl acetate through immobilized lipase-mediated transesterification has been modeled and optimized through statistical integrated artificial intelligence approach. A nonlinear response surface model has been successfully developed based on central composite design with transesterification variables, namely, molarity of alcohol, reaction time, temperature, and immobilized lipase amount as input variables and molar conversion (% as an output variable. Statistical integrated genetic algorithm optimization approach results in an optimized molar conversion of 96.32% with the predicted transesterification variables of 0.47 M alcohol molarity in a reaction time of 13.1 h, at 37.5°C using 13.31 U of immobilized lipase. Immobilized lipase withstands more than 98% relative activity up to 6 recycles and maintains 50% relative activity until 12 recycles. The kinetic constants of benzyl acetate, namely, Km and Vmax were found to be 310 mM and 0.10 mmol h−1 g−1, respectively.

  8. Ultrasound assisted lipase catalyzed synthesis of cinnamyl acetate via transesterification reaction in a solvent free medium.

    Science.gov (United States)

    Tomke, Prerana D; Rathod, Virendra K

    2015-11-01

    Cinnamyl acetate is known for its use as flavor and fragrance material in different industries such as food, pharmaceutical, cosmetic etc. This work focuses on ultrasound assisted lipase (Novozym 435) catalyzed synthesis of cinnamyl acetate via transesterification of cinnamyl alcohol and vinyl acetate in non-aqueous, solvent free system. Optimization of various parameters shows that a higher yield of 99.99% can be obtained at cinnamyl alcohol to vinyl acetate ratio of 1:2 with 0.2% of catalyst, at 40°C and 150 rpm, with lower ultrasound power input of 50 W (Ultrasound intensity 0.81 W/cm(2)), at 25 kHz frequency, 50% duty cycle. Further, the time required for the maximum conversion is reduced to 20 min as compared to 60 min of conventional process. Similarly, the enzyme can be successfully reused seven times without loss of enzyme activity. Thus, ultrasound helps to enhance the enzyme catalyzed synthesis of flavors. Copyright © 2015 Elsevier B.V. All rights reserved.

  9. Solvent-free, microwave-assisted synthesis of thiophene oligomers via Suzuki coupling.

    Science.gov (United States)

    Melucci, Manuela; Barbarella, Giovanna; Sotgiu, Giovanna

    2002-12-13

    The purpose of this study was to obtain a rapid, efficient, and environmentally friendly methodology for the synthesis of highly pure thiophene oligomers. The solvent-free, microwave-assisted coupling of thienyl boronic acids and esters with thienyl bromides, using aluminum oxide as the solid support, allowed us to rapidly check the reaction trends on changing times, temperature, catalyst, and base and easily optimize the experimental conditions to obtain the targeted product in fair amounts. This procedure offers a novel, general, and very rapid route to the preparation of soluble thiophene oligomers. Thus, for example, quaterthiophene was obtained in 6 min by reaction of 2-bromo-2,2'-bithiophene with bis(pinacolato)diboron (isolated yield 65%), whereas quinquethiophene was obtained in 11 min by reaction of dibromoterthiophene with thienylboronic acid (isolated yield 74%). The synthesis of new chiral 2,2'-bithiophenes is reported. The detailed analysis of the byproducts of some reactions allowed us to elucidate a few aspects of reaction mechanisms. While the use of microwaves proved to be very convenient for the coupling between conventional thienyl moieties, the same was not true for the coupling of thienyl rings to thienyl-S,S-dioxide moieties. Indeed, in this case, the targeted product was obtained in low yields because of the competitive, accelerated, Diels-Alder reaction that affords a variety of condensation products.

  10. Erratum to: Solvent-free geranyl oleate production by enzymatic esterification.

    Science.gov (United States)

    Paroul, Natália; Grzegozeski, Luana Paula; Chiaradia, Viviane; Treichel, Helen; Cansian, Rogério L; Oliveira, J Vladimir; de Oliveira, Débora

    2011-03-01

    This study reports the maximization of geranyl oleate production by esterification of geraniol and oleic acid in a solvent-free system using a commercial lipase as catalyst. The operating conditions that maximized geranyl oleate production were determined to be 40 °C, geraniol to oleic acid molar ratio of 5:1, 150 rpm and 10 wt% of enzyme, with a resulting reaction conversion of about 93%. After determining the best reaction parameters, a kinetic study was performed and the results obtained in this step allow to conclude that an excess of alcohol (alcohol to acid molar ratio of 5:1), relatively low enzyme concentration (5 wt%) and temperature of 50 °C afforded nearly complete reaction conversion after 1 h of reaction. New experimental data on enzymatic esterification of geraniol and oleic acid for geranyl oleate production are reported in this work, showing a promising perspective of the technique to overcome the inconvenience of the chemical-catalyzed route.

  11. Solvent-free microwave extraction of essential oil from Dryopteris fragrans and evaluation of antioxidant activity.

    Science.gov (United States)

    Li, Xiao-Juan; Wang, Wei; Luo, Meng; Li, Chun-Ying; Zu, Yuan-Gang; Mu, Pan-Song; Fu, Yu-Jie

    2012-07-15

    Solvent-free microwave extraction (SFME) of the essential oil from Dryopteris fragrans and its antioxidant activity were investigated. A central composite design combined with response surface methodology was applied to study the influences of extraction time, irradiation power and humidity (proportion of water pretreatment). A maximal extraction yield of 0.33% was achieved under optimal conditions of extraction time 34 min, irradiation power 520 W and humidity 51%. Sixteen compounds, representing 89.65% of the oil, were identified, of which the major ones, (1R,4S,11R)-4,6,6,11-tetramethyltricyclo[5.4.0.0(4,8)]undecan-1-ol (30.49%), 1R,4S,7S,11R-2,2,4,8-tetramethyltricyclo[5.3.1.0(4,11)]undec-8-ene (22.91%) and, 1,4,4a,5,6,7,8,8a-octahydro-2,5,5,8a-tetramethyl-1-naphthalenemethanol (15.11%), accounted for 68.51% of the oil. The antioxidant activity of the essential oil was assessed by 2,2-diphenyl-1-picrylhydrazyl (DPPH), β-carotene/linoleic acid, and reducing power assay, the IC50 values were 0.19, 0.09 and 0.18 mg/mL, respectively. All these results suggest that SFME represents an excellent alternative protocol for production of essential oils from plant materials. Copyright © 2012 Elsevier Ltd. All rights reserved.

  12. An Efficient, Solvent-Free Process for Synthesizing Anhydrous MgCl2

    Energy Technology Data Exchange (ETDEWEB)

    Motkuri, Radha K.; Vemuri, Venkata Rama S.; Barpaga, Dushyant; Schaef, Herbert T.; Loring, John S.; Martin, Paul F.; Lao, David; Nune, Satish K.; McGrail, Bernard P.

    2018-01-02

    A new efficient and solvent-free method for the synthesis of anhydrous MgCl2 from its hexahydrate is proposed. Fluidized dehydration of MgCl2·6H2O feedstock at 200 °C in a porous bed reactor yields MgCl2·nH2O (0 < n < 1), which has a similar diffraction pattern as activated MgCl2. The MgCl2·nH2O is then ammoniated directly using liquefied NH3 in the absence of solvent to form MgCl2·6NH3. Calcination of the hexammoniate complex at 300 °C then yields anhydrous MgCl2. Both dehydration and deammoniation were thoroughly studied using in situ as well as ex situ characterization techniques. Specifically, a detailed understanding of the dehydration process was monitored by in situ PXRD and in situ FTIR techniques where formation of salt with nH2O (n = 4, 2, 1, <1) was characterized. Given the reduction in thermal energy required to produce dehydrated feedstock with this method compared with current strategies, significant cost benefits are expected. Overall, the combined effect of activation, macroporosity, and coordinated water depletion allows the formation of hexammoniate without using solvent, thus minimizing waste formation.

  13. Eco-friendly all-carbon paper electronics fabricated by a solvent-free drawing method

    Science.gov (United States)

    Kanaparthi, Srinivasulu; Badhulika, Sushmee

    2016-03-01

    Here we report the fabrication of high-performance all-carbon temperature and infrared (IR) sensors with a solvent-free multiwalled carbon nanotube (MWCNT) trace as the sensing element and commercial graphite pencil trace as the electrical contact on recyclable and biodegradable cellulose filter paper without using any toxic materials or complex procedures. The temperature sensor shows a large negative temperature coefficient of resistance (TCR) in the range of -3100 ppm K-1 to -4900 ppm K-1, which is comparable to available commercial temperature sensors, and an activation energy of 34.85 meV. The IR sensor shows a high responsivity of 58.5 V W-1, which is greater than reported IR sensors with similar dimensions. A detailed study of the conduction mechanism in MWCNTs with temperature and the photo response with IR illumination was done and it was found that the conduction is due to thermally assisted hopping in band tails and the photo response is bolometric in nature. The successful fabrication of these sensors on cellulose filter paper with a comparable performance to existing components indicates that it is possible to fabricate high-performance electronics using low-cost, eco-friendly materials without the need for expensive clean-room processing techniques or harmful chemicals.

  14. Highly Conductive Solvent-Free Polymer Electrolytes for Lithium Rechargeable Batteries

    Energy Technology Data Exchange (ETDEWEB)

    Robert Filler, Zhong Shi and Braja Mandal

    2004-10-21

    In order to obviate the deficiencies of currently used electrolytes in lithium rechargeable batteries, there is a compelling need for the development of solvent-free, highly conducting solid polymer electrolytes (SPEs). The problem will be addressed by synthesizing a new class of block copolymers and plasticizers, which will be used in the formulation of highly conducting electrolytes for lithium-ion batteries. The main objective of this Phase-I effort is to determine the efficacy and commercial prospects of new specifically designed SPEs for use in electric and hybrid electric vehicle (EV/HEV) batteries. This goal will be achieved by preparing the SPEs on a small scale with thorough analyses of their physical, chemical, thermal, mechanical and electrochemical properties. SPEs will play a key role in the formulation of next generation lithium-ion batteries and will have a major impact on the future development of EVs/HEVs and a broad range of consumer products, e.g., computers, camcorders, cell phones, cameras, and power tools.

  15. Efficient and Highly Selective Solvent-Free Oxidation of Primary Alcohols to Aldehydes Using Bucky Nanodiamond.

    Science.gov (United States)

    Lin, Yangming; Wu, Kuang-Hsu Tim; Yu, Linhui; Heumann, Saskia; Su, Dang Sheng

    2017-09-11

    Selective oxidation of alcohols to aldehydes is widely applicable to the synthesis of various green chemicals. The poor chemoselectivity for complicated primary aldehydes over state-of-the-art metal-free or metal-based catalysts represents a major obstacle for industrial application. Bucky nanodiamond is a potential green catalyst that exhibits excellent chemoselectivity and cycling stability for the selective oxidation of primary alcohols in diverse structures (22 examples, including aromatic, substituted aromatic, unsaturated, heterocyclic, and linear chain alcohols) to their corresponding aldehydes. The results are comparable to reported transition-metal catalysts including conventional Pt/C and Ru/C catalysts for certain substrates under solvent-free conditions. The possible activation process of the oxidant and substrates by the surface oxygen groups and defect species are revealed with model catalysts, ex situ electrochemical measurements, and ex situ attenuated total reflectance. The zigzag edges of sp(2) carbon planes are shown to play a key role in these reactions. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Eco-friendly all-carbon paper electronics fabricated by a solvent-free drawing method.

    Science.gov (United States)

    Kanaparthi, Srinivasulu; Badhulika, Sushmee

    2016-03-04

    Here we report the fabrication of high-performance all-carbon temperature and infrared (IR) sensors with a solvent-free multiwalled carbon nanotube (MWCNT) trace as the sensing element and commercial graphite pencil trace as the electrical contact on recyclable and biodegradable cellulose filter paper without using any toxic materials or complex procedures. The temperature sensor shows a large negative temperature coefficient of resistance (TCR) in the range of -3100 ppm K(-1) to -4900 ppm K(-1), which is comparable to available commercial temperature sensors, and an activation energy of 34.85 meV. The IR sensor shows a high responsivity of 58.5 V W(-1), which is greater than reported IR sensors with similar dimensions. A detailed study of the conduction mechanism in MWCNTs with temperature and the photo response with IR illumination was done and it was found that the conduction is due to thermally assisted hopping in band tails and the photo response is bolometric in nature. The successful fabrication of these sensors on cellulose filter paper with a comparable performance to existing components indicates that it is possible to fabricate high-performance electronics using low-cost, eco-friendly materials without the need for expensive clean-room processing techniques or harmful chemicals.

  17. Natural zwitterionic l-Carnitine as efficient cryoprotectant for solvent-free cell cryopreservation.

    Science.gov (United States)

    Zhai, Hongwen; Yang, Jing; Zhang, Jiamin; Pan, Chao; Cai, Nana; Zhu, Yingnan; Zhang, Lei

    2017-07-15

    Organic solvents, such as dimethyl sulfoxide (DMSO) and glycerol, have been commonly used as cryoprotectants (CPAs) in cell cryopreservation. However, their cytotoxicity and need of complex freezing protocols have impeded their applications especially in clinical cell therapy and regenerative medicine. Trehalose has been explored as a natural CPA to cryopreserve cells, but its poor cell permeability frequently results in low cryopreservation efficacy. In this work, we presented that a natural zwitterionic molecule-l-carnitine-could serve as a promising CPA for solvent-free cryopreservation. We demonstrated that l-carnitine possessed strong ability to depress water freezing point, and with ultrarapid freezing protocol, we studied the post-thaw survival efficiency of four cell lines (GLC-82 cells, MCF-7 cells, NIH-3T3 cells and Sheep Red Blood Cells) using l-carnitine without addition of any organic solvents. At the optimum l-carnitine concentration, all four cell lines could achieve above 80% survival efficiency, compared with the significantly lower efficiency using organic CPAs and trehalose. After cryopreservation, the recovered cell behaviors including cell attachment and proliferation were found to be similar to the normal cells, indicating that the cell functionalities were not affected. Moreover, l-carnitine showed no observable cytotoxicity, which was superior to the organic CPAs. This work offered an attractive alternative to traditional CPAs and held great promise to revolutionize current cryopreservation technologies, to benefit the patients in various cell-based clinical applications. Copyright © 2017 Elsevier Inc. All rights reserved.

  18. Solvent-free, molecular-level modeling of self-assembling amphiphiles in water

    Science.gov (United States)

    Dey, Somajit; Saha, Jayashree

    2017-02-01

    Aggregation mesophases of self-assembling amphiphiles in water are highly important in the context of biology (biomembranes), therapy (liposomes), industry (polymer surfactants), and condensed-matter physics (lyotropic liquid crystals). Besides helping to increase fundamental understanding of collective molecular behavior, simulations of these lyotropic phases are pivotal to technological and medical developments such as smart drug carriers for gene therapy. Implicit-solvent, coarse-grained, low resolution modeling with a simple pair potential is the key to realizing the larger length and time scales associated with such mesoscopic phenomena during a computer simulation. Modeling amphiphiles by directed, soft, ellipsoidal cores interacting via a computationally simple yet tunable anisotropic pair potential, we have come to such a single-site model amphiphile that can rapidly self-assemble to give diverse lyotropic phases (such as fluid bilayers, micelles, etc.) without requiring the explicit incorporation of solvent particles. The model directly represents a tunable packing parameter that manifests in the spontaneous curvature of the amphiphile aggregates. Besides the all-important hydrophobic interaction, the hydration force is also treated implicitly. Thanks to the efficient solvent-free molecular-level coarse graining, this model is suitable for generic mesoscale studies of phenomena such as self-assembly, amphiphile mixing, domain formation, fusion, elasticity, etc., in amphiphile aggregates.

  19. An insight on acyl migration in solvent-free ethanolysis of model triglycerides using Novozym 435.

    Science.gov (United States)

    Sánchez, Daniel Alberto; Tonetto, Gabriela Marta; Ferreira, María Luján

    2016-02-20

    In this work, the ethanolysis of triglycerides catalyzed by immobilized lipase was studied, focusing on the secondary reaction of acyl migration. The catalytic tests were performed in a solvent-free reaction medium using Novozym 435 as biocatalyst. The selected experimental variables were biocatalyst loading (5-20mg), reaction time (30-90min), and chain length of the fatty acids in triglycerides with and without unsaturation (short (triacetin), medium (tricaprylin) and long (tripalmitin/triolein)). The formation of 2-monoglyceride by ethanolysis of triglycerides was favored by long reaction times and large biocatalyst loading with saturated short- to medium-chain triglycerides. In the case of long-chain triglycerides, the formation of this monoglyceride was widely limited by acyl migration. In turn, acyl migration increased the yield of ethyl esters and minimized the content of monoglycerides and diglycerides. Thus, the enzymatic synthesis of biodiesel was favored by long-chain triglycerides (which favor the acyl migration), long reaction times and large biocatalyst loading. The conversion of acylglycerides made from long-chain fatty acids with unsaturation was relatively low due to limitations in their access to the active site of the lipase. Copyright © 2016 Elsevier B.V. All rights reserved.

  20. Diffusivities, viscosities, and conductivities of solvent-free ionically grafted nanoparticles

    KAUST Repository

    Hong, Bingbing

    2013-01-01

    A new class of conductive composite materials, solvent-free ionically grafted nanoparticles, were modeled by coarse-grained molecular dynamics methods. The grafted oligomeric counterions were observed to migrate between different cores, contributing to the unique properties of the materials. We investigated the dynamics by analyzing the dependence on temperature and structural parameters of the transport properties (self-diffusion coefficients, viscosities and conductivities) and counterion migration kinetics. Temperature dependence of all properties follows the Arrhenius equation, but chain length and grafting density have distinct effects on different properties. In particular, structural effects on the diffusion coefficients are described by the Rouse model and the theory of nanoparticles diffusing in polymer solutions, viscosities are strongly influenced by clustering of cores, and conductivities are dominated by the motions of oligomeric counterions. We analyzed the migration kinetics of oligomeric counterions in a manner analogous to unimer exchange between micellar aggregates. The counterion migrations follow the "double-core" mechanism and are kinetically controlled by neighboring-core collisions. © 2013 The Royal Society of Chemistry.

  1. Solvent-free optical recording of structural colours on pre-imprinted photocrosslinkable nanostructures

    Science.gov (United States)

    Jiang, Hao; Rezaei, Mohamad; Abdolahi, Mahssa; Kaminska, Bozena

    2017-09-01

    Optical digital information storage media, despite their ever-increasing storage capacity and data transfer rate, are vulnerable to the potential risk of turning inaccessible. For this reason, long-term eye-readable full-colour optical archival storage is in high demand for preserving valuable information from cultural, intellectual, and scholarly resources. However, the concurrent requirements in recording colours inexpensively and precisely, and preserving colours for the very long term (for at least 100 years), have not yet been met by existing storage techniques. Structural colours hold the promise to overcome such challenges. However, there is still the lack of an inexpensive, rapid, reliable, and solvent-free optical patterning technique for recording structural colours. In this paper, we introduce an enabling technique based on optical and thermal patterning of nanoimprinted SU-8 nanocone arrays. Using photocrosslinking and thermoplastic flow of SU-8, diffractive structural colours of nanocone arrays are recorded using ultra-violet (UV) exposure followed by the thermal development and reshaping of nanocones. Different thermal treatment procedures in reshaping nanocones are investigated and compared, and two-step progressive baking is found to allow the controllable reshaping of nanocones. The height of the nanocones and brightness of diffractive colours are modulated by varying the UV exposure dose to enable grey-scale patterning. An example of recorded full-colour image through half-tone patterning is also demonstrated. The presented technique requires only low-power continuous-wave UV light and is very promising to be adopted for professional and consumer archival storage applications.

  2. Extraction of orange peel's essential oil by solvent-free microwave extraction

    Science.gov (United States)

    Qadariyah, Lailatul; Amelia, Prilia Dwi; Admiralia, Cininta; Bhuana, Donny S.; Mahfud, Mahfud

    2017-05-01

    Sweet orange peel (Citrus sinensis) is part of orange plant that contains essential oils. Generally, taking essential oil from orange peel is still using hydrodistillation and steam-hydrodistillation method which still needs solvent and takes a long time to produce high quality essential oil. Therefore, the objectives of this experiment are to study the process of orange peel's essential oil extraction using Solvent Free Microwave Extraction (SFME) and to study the operating condition that effect an optimum yield and quality of the essential oil. In this experiment, extraction process with SFME method goes for 60 minutes at atmospheric pressure. Variables for SFME are: variation of orange peel condition (fresh and dry), ratio orange peel mass to distiller volume (0,1; 0,2; 0,3; 0,4 g/mL), orange peel size (±0,5; ±2; ±3,5 cm width), and microwave power (100, 264, 400 Watt). Moisture content of fresh peel is 71,4% and for dry peel is 17,37% which is obtained by sun drying. The result of this experiment will be analyzed with GC-MS, SEM, density, and miscibility in ethanol 90%. The optimum result obtained from this experiment based on the number of the yield under condition of fresh orange peel is at peel mass/distiller volume 0,1 g/mL, orange peel size ±3,5 cm width, and microwave power 400 Watt, results 1,6738% yield. The result of GC-MS for fresh orange peel shows that the dominant compound is Limonene 54,140% and for dry orange peel is Limonene 59,705%. The density obtained is around 0,8282-0,8530 g/mL and miscibility in ethanol 90% is 1:5.

  3. Solvent-free mechanochemical preparation of phosphonium salts, phosphorus ylides, and olefins

    Energy Technology Data Exchange (ETDEWEB)

    Pecharsky, Vitalij K; Balema, Viktor P; Wiench, Jerzy W; Pruski, Marek

    2006-09-12

    The present invention provides a method of preparing a phosphonium salt of the formula [R.sup.1R.sup.2R.sup.3P--CR.sup.4R.sup.5R.sup.6]X, comprising ball-milling a phosphine of the formula R.sup.1R.sup.2R.sup.3P with a compound of the formula XCR.sup.4R.sup.5R.sup.6; a method of preparing a phosphorus ylide of the formula R.sup.1R.sup.2R.sup.3P.dbd.CR.sup.4R.sup.5, comprising ball-milling a phosphonium salt of the formula [R.sup.1R.sup.2R.sup.3P--HCR.sup.4R.sup.5]X in the presence of a base; and a method of preparing an olefin of the formula R.sup.4R.sup.5C.dbd.CR.sup.7H or R.sup.4R.sup.5C.dbd.CR.sup.7R.sup.8, comprising ball-milling a phosphorus ylide of the formula R.sup.1R.sup.2R.sup.3P.dbd.CR.sup.4R.sup.5 with a compound of the formula R.sup.7C(O)H or R.sup.7C(O)R.sup.8. The inventive method produces phosphonium salts and phosphorus ylides by mechanical processing solid reagents under solvent-free conditions. The advantages of the present invention over conventional solution methods, include: (1) extremely high selectivity; (2) high yields; (3) low processing temperatures; (4) simple and scalable reactions using commercially available equipment; and (5) the complete elimination of solvents from the reaction.

  4. Enantioconvergent catalysis

    Directory of Open Access Journals (Sweden)

    Justin T. Mohr

    2016-09-01

    Full Text Available An enantioconvergent catalytic process has the potential to convert a racemic starting material to a single highly enantioenriched product with a maximum yield of 100%. Three mechanistically distinct approaches to effecting enantioconvergent catalysis are identified, and recent examples of each are highlighted. These processes are compared to related, non-enantioconvergent methods.

  5. Application of 2k Full Factorial Design in Optimization of Solvent-Free Microwave Extraction of Ginger Essential Oil

    Directory of Open Access Journals (Sweden)

    Mumtaj Shah

    2014-01-01

    Full Text Available The solvent-free microwave extraction of essential oil from ginger was optimized using a 23 full factorial design in terms of oil yield to determine the optimum extraction conditions. Sixteen experiments were carried out with three varying parameters, extraction time, microwave power, and type of sample for two levels of each. A first order regression equation best fits the experimental data. The predicted values calculated by the regression model were in good agreement with the experimental values. The results showed that the extraction time is the most prominent factor followed by microwave power level and sample type for extraction process. An average of 0.25% of ginger oil can be extracted using current setup. The optimum conditions for the ginger oil extraction using SFME were the extraction time 30 minutes, microwave power level 640 watts, and sample type, crushed sample. Solvent-free microwave extraction proves a green and promising technique for essential oil extraction.

  6. One-pot synthesis of 2,4,5-trisubstituted imidazole derivatives catalyzed by btppc under solvent-free conditions

    Directory of Open Access Journals (Sweden)

    M. Alikarami

    2017-07-01

    Full Text Available A simple and efficient method for one-pot synthesis of lophine derivatives (2,4,5-trisubstituted imidazoles by using the benzyltriphenylphosphonium chloride (BTPPC, as a catalyst, under solvent-free conditions is described. BTPPC is an available and inexpensive catalyst; also, it can be easily supplied. This procedure led to the corresponding 2,4,5-trisubstituted imidazoles products in high yields.

  7. Nanocrystalline copper(II oxide-catalyzed one-pot four- component synthesis of polyhydroquinoline derivativesunder solvent-free conditions

    Directory of Open Access Journals (Sweden)

    J. Safaei-Ghomi

    2011-07-01

    Full Text Available The efficient and environmentally friendly method for the one-pot synthesis of polyhydroquinolines has been developed in the presence of CuO nanoparticles. The multi-component reactions of aldehydes, dimedone, ethyl acetoacetate andammonium acetate were carried out under solvent-free conditions to afford some polyhydroquinoline derivatives. This method provides several advantages including high yields, low reaction times and little catalyst loading.

  8. An Organocatalyzed and Ultrasound Accelerated Expeditious Synthetic Route to 1,5-Benzodiazepines under Solvent-Free Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Shinde, Pravin V.; Shingate, Bapurao B.; Shingare, Murlidhar S. [Babasaheb Ambedkar Marathwada University, Aurngabad (India)

    2011-04-15

    In the present work, successful implementation of ultrasound irradiations for the rapid synthesis of 1,5- benzodiazepine derivatives under solvent-free conditions is demonstrated. Use of a novel catalyst i.e. camphor sulphonic acid in combination with ultrasound technique is reported for the first time. Comparative study for the synthesis of 1,5-benzodiazepines using conventional as well as ultrasonication method is discussed.

  9. Solvent-Free Off-On Detection of the Improvised Explosive Triacetone Triperoxide (TATP) with Fluorogenic Materials.

    Science.gov (United States)

    Calvo-Gredilla, Patricia; García-Calvo, José; Cuevas, José V; Torroba, Tomás; Pablos, Jesús-Luis; García, Félix C; García, José-Miguel; Zink-Lorre, Nathalie; Font-Sanchis, Enrique; Sastre-Santos, Ángela; Fernández-Lázaro, Fernando

    2017-10-09

    A fluorogenic perylenediimide-functionalized polyacrylate capable of generating color and fluorescence changes in the presence of triacetone triperoxide TATP), an improvised explosive used in terrorist attacks, under solvent-free, solid-state conditions has been developed. The material works by accumulating volatile TATP until it reaches a threshold; therefore, triggering colorimetric and fluorescent responses. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. NaHSO4-SiO2-Promoted Solvent-Free Synthesis of Benzoxazoles, Benzimidazoles, and Benzothiazole Derivatives

    Directory of Open Access Journals (Sweden)

    K. Ravi Kumar

    2013-01-01

    Full Text Available An efficient protocol has been developed for the preparation of a library of benzoxazole, benzimidazole, and benzothiazole derivatives from reactions of acyl chlorides with o-substituted aminoaromatics in the presence of catalytic amount of silica-supported sodium hydrogen sulphate under solvent-free conditions. Simple workup procedure, high yield, easy availability, reusability, and use of ecofriendly catalyst are some of the striking features of the present protocol.

  11. A solvent-free microbial-activated air cathode battery paper platform made with pencil-traced graphite electrodes

    Science.gov (United States)

    Lee, Seung Ho; Ban, Ju Yeon; Oh, Chung-Hun; Park, Hun-Kuk; Choi, Samjin

    2016-06-01

    We present the fabrication of an ultra-low cost, disposable, solvent-free air cathode all-paper microbial fuel cell (MFC) that does not utilize any chemical treatments. The anode and cathode were fabricated by depositing graphite particles by drawing them on paper with a pencil (four strokes). Hydrophobic parchment paper was used as a proton exchange membrane (PEM) to allow only H+ to pass. Air cathode MFC technology, where O2 was used as an electron acceptor, was implemented on the paper platform. The bioelectric current was generated by an electrochemical process involving the redox couple of microbial-activated extracellular electron transferred electrons, PEM-passed H+, and O2 in the cathode. A fully micro-integrated pencil-traced MFC showed a fast start-time, producing current within 10 s after injection of bacterial cells. A single miniaturized all-paper air cathode MFC generated a maximum potential of 300 mV and a maximum current of 11 μA during 100 min after a single injection of Shewanella oneidensis. The micro-fabricated solvent-free air cathode all-paper MFC generated a power of 2,270 nW (5.68 mW/m2). The proposed solvent-free air cathode paper-based MFC device could be used for environmentally-friendly energy storage as well as in single-use medical power supplies that use organic matter.

  12. Olive oil glycerolysis with an immobilized lipase Candida antarctica in a solvent free system

    Directory of Open Access Journals (Sweden)

    Mukhopadhyay, M.

    2012-06-01

    Full Text Available In the present work, the solvent free lipase glycerolysis of olive oil for the production of monoglyceride (MG and diglyceride (DG with an immobilized Lipase B Candida antarctica was studied. The experiments were performed in batch mode by varying different process parameters. The Results showed that the MG and DG yields were dependent on operating conditions such as time, temperature, glycerol/ oil molar ratio, enzyme concentration and the water content in glycerol. The optimum operating time for maximum MG, 26 wt% and DG, 30 wt% production was 3h. The initial reaction rate was studied by varying different process parameters for 1h. The initial reaction rate increased at 30 °C temperature, 2:1 glycerol/oil molar ratio, 3.5% (w/w water content in glycerol and 0.015g of enzyme loading. Comparative data for MG and DG yields for different oils and enzyme combinations were presented.En el presente trabajo se ha estudiado la glicerolisis sin disolvente de aceites de oliva para la producción de monoglicéridos (MG y diglicéridos (DG, con la lipasa inmovilizada Candida antarctica. Los experimentos fueron realizados por lotes, variando distintos parámetros del proceso. Los resultados mostraron que los rendimientos de MG y DG dependen de las condiciones de operación como el tiempo, la temperatura, la relación molar glycerol/aceite, la concentración de la enzima y del contenido en agua del glicerol. El tiempo óptimo de la operación fue de 3h para un rendimiento máximo en peso del 26% de MG, y del 30% de la producción en peso de DG. La velocidad de reacción inicial ha sido estudiada variando los diferentes parámetros del proceso durante 1h. La velocidad de reacción aumenta a la temperatura de 30 °C, con una relación molar 2:1 glicerina/aceite, un contenido de agua en glicerol de 3,5% (w/w y una carga de enzima de 0.015g. Se presentan datos comparativos de redimientos de MG y DG para diferentes aceites y combinaciones de enzima.

  13. Solvent-free oxidation of benzyl alcohol using Au-Pd catalysts prepared by sol immobilisation.

    Science.gov (United States)

    Dimitratos, Nikolaos; Lopez-Sanchez, Jose Antonio; Morgan, David; Carley, Albert F; Tiruvalam, Ramchandra; Kiely, Christopher J; Bethell, Donald; Hutchings, Graham J

    2009-07-07

    We report the preparation of Au-Pd nanocrystalline catalysts supported on TiO(2) and carbon prepared via a sol-immobilisation technique using three different preparation strategies; namely, simultaneous formation of the sols for both metals or initial formation of a seed sol of one of the metals followed by a separate step in which a coating sol of the second metal is added. The catalysts have been structurally characterised using a combination of transmission electron microscopy and X-ray photoelectron spectroscopy. The catalysts have been evaluated for the oxidation of benzyl alcohol under solvent-free conditions. The catalysts prepared using the sol immobilisation technique show higher activity when compared with catalysts prepared by impregnation, particularly as lower metal concentrations can be used. The Au-Pd catalysts were all more active than the corresponding monometallic supported Au or Pd catalysts. For 1 wt% Au-Pd/TiO(2) the order of metal addition in the preparation was not observed to be significant with respect to selectivity or activity. However, the 1 wt% Au-Pd/carbon catalysts are more active but less selective to benzaldehyde than the TiO(2)-supported catalysts when compared at iso-conversion. Furthermore, for the carbon-supported catalyst the order of metal addition has a very marked affect on activity. The carbon-supported catalysts are also more significantly affected by heat treatment, e.g. calcination at 400 degrees C leads to the activity being decreased by an order of magnitude, whereas the TiO(2)-supported catalysts show a 50% decrease in activity. Toluene is observed as a by-product of the reaction and conditions have been identified that minimise its formation. It is proposed that toluene and benzaldehyde are formed by competing parallel reactions of the initial benzyl intermediate via an adsorbed benzylidene species that can either be hydrogenated or oxidised. Hence, conditions that maximise the availability of oxygen on the catalyst

  14. Cyclodextrins in Asymmetric and Stereospecific Synthesis

    Directory of Open Access Journals (Sweden)

    Fliur Macaev

    2015-09-01

    Full Text Available Since their discovery, cyclodextrins have widely been used as green and easily available alternatives to promoters or catalysts of different chemical reactions in water. This review covers the research and application of cyclodextrins and their derivatives in asymmetric and stereospecific syntheses, with their division into three main groups: (1 cyclodextrins promoting asymmetric and stereospecific catalysis in water; (2 cyclodextrins’ complexes with transition metals as asymmetric and stereospecific catalysts; and (3 cyclodextrins’ non-metallic derivatives as asymmetric and stereospecific catalysts. The scope of this review is to systematize existing information on the contribution of cyclodextrins to asymmetric and stereospecific synthesis and, thus, to facilitate further development in this direction.

  15. Asymmetric Aminalization via Cation-Binding Catalysis

    DEFF Research Database (Denmark)

    Park, Sang Yeon; Liu, Yidong; Oh, Joong Suk

    2018-01-01

    -protected alkyl- and aryl-substituted α-amido sulfones. In-situ generated imines smoothly reacted with the nitrogen nucleophiles to corresponding aminals with good to excellent enantioselectivitiy under mild reaction conditions. In addition, transformation of aminal products gave biologically relevant...

  16. Selective Homogeneous Catalysis in Asymmetric Synthesis

    DEFF Research Database (Denmark)

    Fristrup, Peter

    with predictions based on computational modelling of the transition states. Visualization of the determined transition states allowed for the construction of the new mnemonic device for prediction of absolute configuration, which also included a mapping of the important features onto an overlaid transition state....

  17. DIFLUORPHOS and SYNPHOS in asymmetric catalysis: Synthetic ...

    Indian Academy of Sciences (India)

    It should be noted that the use of sterically more hin- dered arylboronic acids such as 2-tolylboronic acid and. 1-naphthylboronic acid gave slightly lower enantiose- lectivity, probably due to increased steric hindrance. As highlighted in scheme 9, both cyclic and acyclic α,β- unsaturated ketones and lactones were found to be ...

  18. DIFLUORPHOS and SYNPHOS in asymmetric catalysis: Synthetic ...

    Indian Academy of Sciences (India)

    Author Affiliations. Sebastien Prevost1 Tahar Ayad1 Jean-Pierre Genet1 Phannarath Phansavath1 Virginie Ratovelomanana-Vidal1. Institut de Recherche de Chimie Paris, CNRS - Chimie ParisTech, 11 rue Pierre et Marie Curie, 75231 Paris Cedex 05, France ...

  19. B(HSO4)3: a novel and efficient solid acid catalyst for the regioselective conversion of epoxides to thiocyanohydrins under solvent-free conditions

    National Research Council Canada - National Science Library

    Ali Reza Kiasat; Mehdi Fallah-Mehrjardi

    2008-01-01

    B(HSO4)3 was easily prepared and used as a novel and efficient solid acid catalyst for conversion of epoxides to the corresponding thiocyanohydrins under solvent-free conditions with high isolated yields...

  20. Marginal Microleakage and Morphological Characteristics of a Solvent-Free One-Step Self-Etch Adhesive (B1SF

    Directory of Open Access Journals (Sweden)

    Maryam Khoroushi

    2013-01-01

    Full Text Available Objective: In recent years, newly developed solvent-free dental adhesives have been introduced. The aim of this study was to evaluate the marginal integrity of a new one-step solvent-free self-etch adhesive and to compare it with a commonly used two-step self-etch adhesive as the gold standard.Materials and Methods: Class V cavities (2×4×1.5 mm were prepared on the buccal aspects of 28 human premolars. The cervical margins of the cavity preparations were placed 1 mm apical to the CEJ. Clearfil SE Bond (CSEB (two-step self-etch adhesive and Bond 1SF (B1SF (one-step self-etch adhesive were applied to the cavities in groups 1 and 2 (n=14, respectively. Then, the specimens were restored with A2 shade of APX composite resin. Each group was evaluated for dye penetration under a stereomicroscope at ×32 after 24 hours and 500 rounds of thermocycling. Statistical analyses were carried out using Mann Whitney test (α=0.05. In addition, in each experimental group, two specimens were prepared for analysis under SEM.Results: There were no significant differences in enamel margin microleakage between the two adhesives used (P=0.24(; whereas, there were significant differences in dentin margin microleakage between CSEB and B1SF (P=0.004. Dentin microleakage of B1SF was higher than that of CSEB.Conclusion: Results showed that the enamel marginal integrity of B1SF as a newly developed one-step solvent-free self-etch adhesive was similar to that of CSEB as a commonly used two-step self-etch; however, dentinal sealing of CSEB was better than that of B1SF.

  1. Marginal Microleakage and Morphological Characteristics of a Solvent-Free One-Step Self-Etch Adhesive (B1SF)

    Science.gov (United States)

    Khoroushi, Maryam; Shirban, Farinaz; Shirban, Mohammadreza

    2013-01-01

    Objective: In recent years, newly developed solvent-free dental adhesives have been introduced. The aim of this study was to evaluate the marginal integrity of a new one-step solvent-free self-etch adhesive and to compare it with a commonly used two-step self-etch adhesive as the gold standard. Materials and Methods: Class V cavities (2×4×1.5 mm) were prepared on the buccal aspects of 28 human premolars. The cervical margins of the cavity preparations were placed 1 mm apical to the CEJ. Clearfil SE Bond (CSEB) (two-step self-etch adhesive) and Bond 1SF (B1SF) (one-step self-etch adhesive) were applied to the cavities in groups 1 and 2 (n=14), respectively. Then, the specimens were restored with A2 shade of APX composite resin. Each group was evaluated for dye penetration under a stereomicroscope at ×32 after 24 hours and 500 rounds of thermocycling. Statistical analyses were carried out using Mann Whitney test (α=0.05). In addition, in each experimental group, two specimens were prepared for analysis under SEM. Results: There were no significant differences in enamel margin microleakage between the two adhesives used (P=0.24(; whereas, there were significant differences in dentin margin microleakage between CSEB and B1SF (P=0.004). Dentin microleakage of B1SF was higher than that of CSEB. Conclusion: Results showed that the enamel marginal integrity of B1SF as a newly developed one-step solvent-free self-etch adhesive was similar to that of CSEB as a commonly used two-step self-etch; however, dentinal sealing of CSEB was better than that of B1SF. PMID:23724201

  2. Solvent free fabrication of micro and nanostructured drug coatings by thermal evaporation for controlled release and increased effects.

    Directory of Open Access Journals (Sweden)

    Eman S Zarie

    Full Text Available Nanostructuring of drug delivery systems offers many promising applications like precise control of dissolution and release kinetics, enhanced activities, flexibility in terms of surface coatings, integration into implants, designing the appropriate scaffolds or even integrating into microelectronic chips etc. for different desired applications. In general such kind of structuring is difficult due to unintentional mixing of chemical solvents used during drug formulations. We demonstrate here the successful solvent-free fabrication of micro-nanostructured pharmaceutical molecules by simple thermal evaporation (TE. The evaporation of drug molecules and their emission to a specific surface under vacuum led to controlled assembling of the molecules from vapour phase to solid phase. The most important aspects of thermal evaporation technique are: solvent-free, precise control of size, possibility of fabricating multilayer/hybrid, and free choice of substrates. This could be shown for twenty eight pharmaceutical substances of different chemical structures which were evaporated on surfaces of titanium and glass discs. Structural investigations of different TE fabricated drugs were performed by atomic force microscopy, scanning electron microscopy and Raman spectroscopy which revealed that these drug substances preserve their structurality after evaporation. Titanium discs coated with antimicrobial substances by thermal evaporation were subjected to tests for antibacterial or antifungal activities, respectively. A significant increase in their antimicrobial activity was observed in zones of inhibition tests compared to controls of the diluted substances on the discs made of paper for filtration. With thermal evaporation, we have successfully synthesized solvent-free nanostructured drug delivery systems in form of multilayer structures and in hybrid drug complexes respectively. Analyses of these substances consolidated that thermal evaporation opens up

  3. Hot Melt Extrusion as Solvent-Free Technique for a Continuous Manufacturing of Drug-Loaded Mesoporous Silica

    DEFF Research Database (Denmark)

    Genina, Natalja; Hadi, Batol; Löbmann, Korbinian

    2018-01-01

    The aim of this study is to explore hot melt extrusion (HME) as a solvent-free drug loading technique for preparation of stable amorphous solid dispersions using mesoporous silica (PSi). Ibuprofen and carvedilol were used as poorly soluble active pharmaceutical ingredients (APIs). Due to the high...... friction of an API:PSi mixture below the loading limit of the API, it was necessary to add the polymer Soluplus(®) (SOL) in order to enable the extrusion process. As a result, the APIs were distributed between the PSi and SOL phase after HME. Due to its higher affinity to PSi, ibuprofen was mainly adsorbed...

  4. YCl3-Catalyzed Highly Selective Ring Opening of Epoxides by Amines at Room Temperature and under Solvent-Free Conditions

    Directory of Open Access Journals (Sweden)

    Wuttichai Natongchai

    2017-11-01

    Full Text Available A simple, efficient, and environmentally benign approach for the synthesis of β-amino alcohols is herein described. YCl3 efficiently carried out the ring opening of epoxides by amines to produce β-amino alcohols under solvent-free conditions at room temperature. This catalytic approach is very effective, with several aromatic and aliphatic oxiranes and amines. A mere 1 mol % concentration of YCl3 is enough to deliver β-amino alcohols in good to excellent yields with high regioselectivity.

  5. Chemoselective Synthesis of Dithioacetals from Bio-aldehydes with Zeolites under Ambient and Solvent-free Conditions

    DEFF Research Database (Denmark)

    Li, Hu; Yang, Tingting; Riisager, Anders

    2017-01-01

    of commercial and modified zeolites are excellent catalysts for thioacetalization of different thiols with carbonyl compounds, including biomass-derived aldehydes, at room temperature under solvent-free conditions. A near quantitative yield of dithioacetal was obtained over H-beta(19) at room temperature...... calcination at 550 degrees C. The results and physicochemical properties of the zeolites revealed that relatively large pores and moderate acidity with an appropriate distribution of Bronsted/Lewis acid sites contributed to the pronounced performance in the dithioacetal formation....

  6. Bimetallic catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Beuken, E.K. van den; Leeuwen, P.W.N.M. van; Budzelaar, P.H.M.; Feringa, B.L. [Univ. of Groningen (Netherlands)

    1995-12-31

    The field of binucleating ligand systems and their bimetallic complexes has developed considerably in recent years. When two metals are in close proximity the formation of metal-metal bonds, insertion of small molecules into a metal-metal bond, ligand mobility from terminal to bridging site and the transfer of ligands from one metal centre to the other can be observed. A prominent example is the cooperative effect of two metal centres in the hydroformylation reaction of 1-hexene with a dinuclear rhodium phosphine complex. Following interest in bimetallic catalysis, the authors now report the synthesis, molecular structure determination and application in catalysis of a new dinuclear rhodium phosphate complex. A relatively simple synthetic route to diphosphite ligand 1 and tetraphosphite ligand 2 and their corresponding mononuclear complex Rh(acac) and dinuclear complex Rh{sub 2}(acac){sub 2} was developed. Rh{sub 2}(acac){sub 2}, which is the precursor of the catalyst was characterised by X-ray analysis. The active catalysts derived from 1 and 2 are studied by high pressure NMR. Hydroformylation of various alkenes under mild conditions (20 mmol substate, 4 {mu}mol Rh(acac)(CO){sub 2}, 20 bar CO/H{sub 2}, 80{degrees}C) with diphosphite 1 and tetraphosphite 2 will be reported.

  7. Enantioselective Solvent-Free Synthesis of 3-Alkyl-3-hydroxy-2-oxoindoles Catalyzed by Binam-Prolinamides

    Directory of Open Access Journals (Sweden)

    Abraham Bañn-Caballero

    2015-07-01

    Full Text Available BINAM-prolinamides are very efficient catalyst for the synthesis of non-protected and N-benzyl isatin derivatives by using an aldol reaction between ketones and isatins under solvent-free conditions. The results in terms of diastereo- and enantioselectivities are good, up to 99% de and 97% ee, and higher to those previously reported in the literature under similar reaction conditions. A high variation of the results is observed depending on the structure of the isatin and the ketone used in the process. While 90% of ee and 97% ee, respectively, is obtained by using (Ra-BINAM-l-(bisprolinamide as catalyst in the addition of cyclohexanone and α-methoxyacetone to free isatin, 90% ee is achieved for the reaction between N-benzyl isatin and acetone using N-tosyl BINAM-l-prolinamide as catalyst. This reaction is also carried out using a silica BINAM-l-prolinamide supported catalyst under solvent-free conditions, which can be reused up to five times giving similar results.

  8. Monitoring ibuprofen-nicotinamide cocrystal formation during solvent free continuous cocrystallization (SFCC) using near infrared spectroscopy as a PAT tool.

    Science.gov (United States)

    Kelly, A L; Gough, T; Dhumal, R S; Halsey, S A; Paradkar, A

    2012-04-15

    The purpose of this work was to explore NIR spectroscopy as a PAT tool to monitor the formation of ibuprofen and nicotinamide cocrystals during extrusion based solvent free continuous cocrystallization (SFCC). Drug and co-former were gravimetrically fed into a heated co-rotating twin screw extruder to form cocrystals. Real-time process monitoring was performed using a high temperature NIR probe in the extruder die to assess cocrystal content and subsequently compared to off-line powder X-ray diffraction measurements. The effect of processing variables, such as temperature and mixing intensity, on the extent of cocrystal formation was investigated. NIR spectroscopy was sensitive to cocrystal formation with the appearance of new peaks and peak shifts, particularly in the 4800-5200 cm(-1) wave-number region. PXRD confirmed an increased conversion of the mixture into cocrystal with increase in barrel temperature and screw mixing intensity. A decrease in screw rotation speed also provided improved cocrystal yield due to the material experiencing longer residence times within the process. A partial least squares analysis in this region of NIR spectrum correlated well with PXRD data, providing a best fit with cocrystal conversion when a limited range of process conditions were considered, for example a single set temperature. The study suggests that NIR spectroscopy could be used to monitor cocrystal purity on an industrial scale using this continuous, solvent-free process. Copyright © 2011 Elsevier B.V. All rights reserved.

  9. Insights of the Crystallization Process of Molecular Sieve AlPO4-5 Prepared by Solvent-Free Synthesis.

    Science.gov (United States)

    Sheng, Na; Chu, Yueying; Xin, Shaohui; Wang, Qiang; Yi, Xianfeng; Feng, Zhaochi; Meng, Xiangju; Liu, Xiaolong; Deng, Feng; Xiao, Feng-Shou

    2016-05-18

    Crystallization of AlPO4-5 with AFI structure under solvent-free conditions has been investigated. Attention was mainly focused on the characterization of the intermediate phases formed at the early stages during the crystallization. The development in the long-range ordering of the solid phases as a function of crystallization time was monitored by XRD, SEM, IR, UV-Raman, and MAS NMR techniques. Particularly, the UV-Raman spectroscopy was employed to obtain the information on the formation process of the framework. J-HMQC (27)Al/(31)P double-resonance NMR experiments were used to identify the P-O-Al bonded species in the intermediate phases. For the first time the P-O-Al bonded species in the intermediate phases can be correctly described through using this advanced NMR technique. The crystallization under solvent-free conditions appears to follow the pathway: The initial amorphous raw material is converted to an intermediate phase which has four-/six-membered ring species, then gradually transformed into crystalline AlPO4-5. This observation is not consistent with the common idea that the intermediate phase is the semicrystalline intermediates with a three-dimensional structure.

  10. Physicochemical characterization of a navy bean (Phaseolus vulgaris) protein fraction produced using a solvent-free method.

    Science.gov (United States)

    Jafari, Mousa; Rajabzadeh, Amin Reza; Tabtabaei, Solmaz; Marsolais, Frédéric; Legge, Raymond L

    2016-10-01

    A solvent-free electrostatic separation method was employed to separate navy bean flour (NBF) into protein-rich (PR) and starch-rich (SR) fractions. The physicochemical properties of NBF and separated fractions were compared to proteins (navy bean isolate (NBI) and 7S globulin) prepared using a wet process. Gel electrophoresis confirmed that the protein distribution in the isolated fractions was similar to that of NBF. The protein profile of NBI and 7S globulin was found to be devoid of certain proteins that were found in the NBF and PR fraction. Amino acid analysis revealed that the NBI and 7S globulin had a lower content of sulfur-containing amino acids compared to NBF and the electrostatically isolated fractions. CD and fluorescence spectroscopy confirmed that denaturation of the proteins during the acid precipitation is likely. This novel solvent-free electrostatic separation process preserves the native protein structure found in NBF and improves the recovery of some of the smaller MW proteins. Copyright © 2016 Elsevier Ltd. All rights reserved.

  11. Highly efficient cobalt-doped carbon nitride polymers for solvent-free selective oxidation of cyclohexane

    Directory of Open Access Journals (Sweden)

    Yu Fu

    2017-04-01

    Full Text Available Selective oxidation of saturated hydrocarbons with molecular oxygen has been of great interest in catalysis, and the development of highly efficient catalysts for this process is a crucial challenge. A new kind of heterogeneous catalyst, cobalt-doped carbon nitride polymer (g-C3N4, was harnessed for the selective oxidation of cyclohexane. X-ray diffraction, Fourier transform infrared spectra and high resolution transmission electron microscope revealed that Co species were highly dispersed in g-C3N4 matrix and the characteristic structure of polymeric g-C3N4 can be retained after Co-doping, although Co-doping caused the incomplete polymerization to some extent. Ultraviolet–visible, Raman and X-ray photoelectron spectroscopy further proved the successful Co doping in g-C3N4 matrix as the form of Co(IIN bonds. For the selective oxidation of cyclohexane, Co-doping can markedly promote the catalytic performance of g-C3N4 catalyst due to the synergistic effect of Co species and g-C3N4 hybrid. Furthermore, the content of Co largely affected the activity of Co-doped g-C3N4 catalysts, among which the catalyst with 9.0 wt% Co content exhibited the highest yield (9.0% of cyclohexanone and cyclohexanol, as well as a high stability. Meanwhile, the reaction mechanism over Co-doped g-C3N4 catalysts was elaborated. Keywords: Selective oxidation of cyclohexane, Oxygen oxidant, Carbon nitride, Co-doping

  12. Synthesis and application of aryl-ferrocenyl(pseudo-biarylic) complexes. Part 5. Design and synthesis of a new type of ferrocene-based planar chiral DMAP analogues. A new catalyst system for asymmetric nucleophilic catalysis

    DEFF Research Database (Denmark)

    Seitzberg, J.G; Dissing, C; Søtofte, Inger

    2005-01-01

    A new first-generation catalyst system for nucleophilic catalysis has been developed. It is based on a planar chiral ferrocene skeleton with either the potent nucleophile 4-(dimethylamino)pyridine (DMAP) or the related 4-nitropyridine N-oxide attached in either the 2- or the 3-position. The synth......A new first-generation catalyst system for nucleophilic catalysis has been developed. It is based on a planar chiral ferrocene skeleton with either the potent nucleophile 4-(dimethylamino)pyridine (DMAP) or the related 4-nitropyridine N-oxide attached in either the 2- or the 3-position...

  13. Application of (S,S)-Pentacycloundecane bis(4-Phenyloxazoline) as a Novel Chiral Ligand for Catalysis of the Asymmetric Diels-Alder Reaction of Cyclopentadiene with 3-Acryloyl-2-oxazolidinone

    National Research Council Canada - National Science Library

    Arvidsson, Per I; Govender, Thavendran; Kruger, G; Maguire, M; Naicker, Tricia

    2009-01-01

    The synthesis of the novel C-1 symmetric (S,S)-pentacycloundecane bis(4-phenyloxazoline) ligand 5 and its evaluation as a chiral Lewis acid catalyst in the benchmark asymmetric Diels-Alder reaction between 3-acryloyloxazolidin-2-one...

  14. Solvent-free bismuth oxycarbonate-mediated mechanochemical glycosylation: A simple greener alternative to access O-/S-glycosides efficiently.

    Science.gov (United States)

    Sethi, Kashmir Prasad; Kartha, K P Ravindranathan

    2016-11-03

    Preparation of a variety of per-O-acylated O- and S-glycosides of a set of commonly encountered mono- and disaccharides has been achieved effectively by solvent-free grinding of the corresponding acetylated/benzoylated glycosyl bromide and the desired acceptor alcohol/thiol in the presence of bismuth carbonate in a planetary ball mill. The method is simple, requires short reaction time periods and is practical allowing it to be performed at a milligram-to multi-gram scale as required. In the cases where the product is crystalline, it was often obtained in practically pure form by crystallization (and without the need for chromatographic isolation). Copyright © 2016 Elsevier Ltd. All rights reserved.

  15. Solvent-free microwave extraction of essential oil from aromatic herbs: from laboratory to pilot and industrial scale.

    Science.gov (United States)

    Filly, Aurore; Fernandez, Xavier; Minuti, Matteo; Visinoni, Francesco; Cravotto, Giancarlo; Chemat, Farid

    2014-05-01

    Solvent-free microwave extraction (SFME) has been proposed as a green method for the extraction of essential oil from aromatic herbs that are extensively used in the food industry. This technique is a combination of microwave heating and dry distillation performed at atmospheric pressure without any added solvent or water. The isolation and concentration of volatile compounds is performed in a single stage. In this work, SFME and a conventional technique, hydro-distillation HD (Clevenger apparatus), are used for the extraction of essential oil from rosemary (Rosmarinus officinalis L.) and are compared. This preliminary laboratory study shows that essential oils extracted by SFME in 30min were quantitatively (yield and kinetics profile) and qualitatively (aromatic profile) similar to those obtained using conventional hydro-distillation in 2h. Experiments performed in a 75L pilot microwave reactor prove the feasibility of SFME up scaling and potential industrial applications. Copyright © 2013 Elsevier Ltd. All rights reserved.

  16. Tunable microwave-assisted method for the solvent-free and catalyst-free peracetylation of natural products

    Directory of Open Access Journals (Sweden)

    Manuela Oliverio

    2016-10-01

    Full Text Available Background: The peracetylation is a simple chemical modification that can be used to enhance the bioavailability of hydrophilic products and to obtain safe and stable pro-drugs.Results: A totally green, solvent-free and catalyst-free microwave (MW-assisted method for peracetylation of natural products such as oleuropein, alpha-hederin, quercetin and rutin is presented. By simply tuning the MW heating program, polyols with chemical diverse –OH groups or thermolabile functionalities can be peracetylated to improve the biological activity without degradation of the natural starting molecules. An evaluation of the process greenness was performed.Conclusion: The method is potentially universally applicable for green acetylation of hydrophilic biological molecules, potentially easily scalable for industrial applications, including pharmaceutical, cosmetic and food industry.

  17. Facile synthesis of 1-naphthol azo dyes with nano SiO2/HIO4 under solvent-free conditions

    Directory of Open Access Journals (Sweden)

    A.R. Pourali

    2013-09-01

    Full Text Available Nano-silica supported periodic acid (nano-SPIA has been utilized as a heterogeneous reagent for a highly efficient and one pot synthesis of azo dyes based on 1-naphthol under solvent-free conditions at room temperature. This method has some advantages, the reaction workup is very easy and the catalyst can be easily separated from the reaction mixture and one-pot procedure. The related products have been obtained in good to excellent yields, high purity and short reaction times. The structures of the products have been characterized by several techniques using UV-Vis, FT-IR, 1H NMR, 13C NMR and mass spectra.DOI: http://dx.doi.org/10.4314/bcse.v27i3.13

  18. An improved solvent-free synthesis of flunixin and 2-(arylamino) nicotinic acid derivatives using boric acid as catalyst.

    Science.gov (United States)

    Yarhosseini, Mahsa; Javanshir, Shahrzad; Dolatkhah, Zahra; Dekamin, Mohammad G

    2017-12-01

    A simple solvent-free protocol for the preparation of flunixin, a potent non-narcotic, non-steroidal anti-inflammatory drugs is reported using boric acid as catalyst. Its salt, flunixin meglumine are then prepared under reflux in EtOH. This sustainable method are then extended for the synthesis of a series of 2-(arylamino) nicotinic acid derivatives. The present protocol combines non-hazardous neat conditions with associated benefits like excellent yield, straightforward workup, and use of readily available and safe catalyst in the absence of any solvent, which are important factors in the pharmaceutical industry. The pathway for catalytic activation of 2-chloronicotic acid with boric acid was also investigated using Gaussian 03 program package.

  19. Solvent-free synthesis of azomethines, spectral correlations and antimicrobial activities of some E-benzylidene-4-chlorobenzenamines

    Directory of Open Access Journals (Sweden)

    R. Suresh

    2015-07-01

    Full Text Available Some azomethines including substituted benzylidene-4-chlorobenzenamines (E-imines have been synthesized by fly-ash: PTS catalyzed microwave assisted condensation of 4-chloroaniline and substituted benzaldehydes under solvent-free conditions. The yield of the imines has been found to be more than 85%. The purity of all imines has been checked using their physical constants and UV, IR and NMR spectral data. These spectral data have been correlated with Hammett substituent constants and F and R parameters using single and multi-linear regression analysis. From the results of statistical analysis, the effect of substituents on the above spectral data has been studied. The antimicrobial activities of all imines have been studied using standard methods.

  20. Fast synthesis of 1,3-DAG by Lecitase® Ultra-catalyzed esterification in solvent-free system.

    Science.gov (United States)

    Liu, Ning; Wang, Yong; Zhao, Qiangzhong; Zhang, Qingli; Zhao, Mouming

    2011-08-01

    Lecitase® Ultra, a phospholipase, was explored as an effective biocatalyst for direct esterification of glycerol with oleic acid to produce 1,3-DAG. Experiments were carried out in batch mode, and optimal reaction conditions were evaluated. In comparison with several organic solvent mediums, the solvent-free system was found to be more beneficial for this esterification reaction, which was further studied to investigate the reaction conditions including oleic acid/glycerol mole ratio, temperature, initial water content, enzyme load, and operating time. The results showed that Lecitase® Ultra catalyzed a fast synthesis of 1,3-DAG by direct esterification in a solvent-free medium. Under the optimal reaction conditions, a short reaction time 1.5 h was found to achieve the fatty acid esterification efficiency of 80.3 ± 1.2% and 1,3-DAG content of 54.8 ± 1.6 wt% (lipid layer of reaction mixture mass). The reusability of Lecitase® Ultra was evaluated via recycling the excess glycerol layer in the reaction system. DAG in the upper lipid layer of reaction mixture was purified by molecular distillation and the 1,3-DAG-enriched oil with a purity of about 75 wt% was obtained.Practical applications: The new Lecitase® Ultra catalyzed process for production of 1,3-DAG from glycerol and oleic acid described in this study provides several advantages over conventional methods including short reaction time, the absence of a solvents and a high product yield.

  1. Solvent-free functionalization of fullerene C{sub 60} and pristine multi-walled carbon nanotubes with aromatic amines

    Energy Technology Data Exchange (ETDEWEB)

    Ramírez-Calera, Itzel J. [Centro de Ciencias Aplicadas y Desarrollo Tecnológico, Universidad Nacional Autónoma de México, Circuito Exterior C. U., 04510, México, D.F. (Mexico); Meza-Laguna, Victor [Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Circuito Exterior C. U., 04510 México, D.F. (Mexico); Gromovoy, Taras Yu. [O.O. Chuiko Institute of Surface Chemistry, National Academy of Sciences of the Ukraine, Gen. Naumova 17, 03164 Kiev (Ukraine); Chávez-Uribe, Ma. Isabel [Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior C. U., 04510 México, D.F. (Mexico); Basiuk, Vladimir A., E-mail: basiuk@nucleares.unam.mx [Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Circuito Exterior C. U., 04510 México, D.F. (Mexico); Basiuk, Elena V., E-mail: elbg1111@gmail.com [Centro de Ciencias Aplicadas y Desarrollo Tecnológico, Universidad Nacional Autónoma de México, Circuito Exterior C. U., 04510, México, D.F. (Mexico)

    2015-02-15

    Highlights: • Pristine multi-walled carbon nanotubes were functionalized with aromatic amines. • The amines add onto nanotube defects, likewise they add onto fullerene C{sub 60}. • The addition takes place at elevated temperature and without organic solvents. • Functionalized nanotubes were characterized by a number of instrumental techniques. - Abstract: We employed a direct one-step solvent-free covalent functionalization of solid fullerene C{sub 60} and pristine multi-walled carbon nanotubes (MWCNTs) with aromatic amines 1-aminopyrene (AP), 2-aminofluorene (AF) and 1,5-diaminonaphthalene (DAN). The reactions were carried out under moderate vacuum, in a wide temperature range of 180–250 °C, during relatively short time of about 2 h. To confirm successful amine attachment, a large number of analytical techniques were used (depending on the nanomaterial functionalized) such as Fourier transform infrared, Raman, X-ray photoelectron, {sup 13}C cross-polarization magic angle spinning NMR spectroscopy, thermogravimetric analysis, laser-desorption ionization time-of-flight mass spectrometry, temperature-programmed desorption with mass spectrometric detection, as well as scanning and transmission electron microscopy. The nucleophilic addition of the aromatic amines to C{sub 60} molecule was studied theoretically by using density functional theory (PBE GGA functional with Grimme dispersion correction in conjunction with the DNP basis set). In the case of crystalline C{sub 60}, the solvent-free technique has a limited applicability due to poor diffusion of vaporous aromatic amines into the bulk. Nevertheless, the approach proposed allows for a facile preparation of aromatic amine-functionalized pristine MWCNTs without contamination with other chemical reagents, detergents and solvents, which is especially important for a vast variety of nanotube applications spanning from nanoelectronics to nanomedicine.

  2. Synthesis of quinoxaline 1,4-di-n-oxide derivatives on solid support using room temperature and microwave-assisted solvent-free procedures

    Energy Technology Data Exchange (ETDEWEB)

    Gomez-Caro, Lilia C.; Sanchez-Sanchez, Mario; Bocanegra-Garcia, Virgilio; Rivera, Gildardo [Universidad Autonoma de Tamaulipas, Reynosa (Mexico). Dept. de Farmacia y Quimica Medicinal; Monge, Antonio [Universidad de Navarra, Pamplona (Spain). Centro de Investigacion en Farmacobiologia Aplicada. Unidad de Investigacion y Desarrollo de Medicamentos

    2011-07-01

    We describe the synthesis of 12 new ethyl and methyl quinoxaline-7-carboxylate 1,4-di-N-oxide derivatives on solid supports with room temperature and microwave-assisted solvent-free procedures. Results show that solid supports have good catalytic activity in the formation of quinoxaline 1,4-di-N-oxide derivatives. We found that florisil and montmorillonite KSF and K10 could be used as new, easily available, inexpensive alternatives of catalysts. Additionally, room temperature and microwave-irradiation solvent-free synthesis was more efficient than a conventional procedure (Beirut reaction), reducing reaction time and increasing yield. (author)

  3. Catalysis of Photochemical Reactions.

    Science.gov (United States)

    Albini, A.

    1986-01-01

    Offers a classification system of catalytic effects in photochemical reactions, contrasting characteristic properties of photochemical and thermal reactions. Discusses catalysis and sensitization, examples of catalyzed reactions of excepted states, complexing ground state substrates, and catalysis of primary photoproducts. (JM)

  4. Al(HSO{sub 4}){sub 3} as an efficient catalyst for acetalization of carbonyl compounds under heterogeneous or solvent-free conditions

    Energy Technology Data Exchange (ETDEWEB)

    Mirjalili, BiBi Fatemeh; Hazar, Azizeh [Yazd University, Yazd (Iran, Islamic Republic of). College of Science. Dept. of Chemistry]. E-mail: fmirjalili@yazduni.ac.ir; Zolfigol, Mohammad Ali [Bu-Ali Sina University, Hamadan (Iran, Islamic Republic of). College of Science. Dept. of Chemistry; Bamoniri, Abdolhamid [Kashan University, Kashan (Iran, Islamic Republic of). College of Science. Dept. of Chemistry

    2005-07-15

    Al(HSO{sub 4}){sub 3} as a solid acid was applied for acetalization of carbonyl compounds at room temperature and under solvent-free conditions with good to excellent yields. The cheapness and availability of this reagent with easy procedure and work-up make this method attractive for the organic synthesis. (author)

  5. Solvent-free fabrication of micro-porous polyurethane amide and polyurethane-urea scaffolds for repair and replacement of the knee-joint meniscus

    NARCIS (Netherlands)

    Spaans, C.J; Belgraver, V.W.; Rienstra, O.; de Groot, J.H; Veth, R.P.H.; Penning, J.P

    2000-01-01

    New porous polyurethane urea and polyurethane amide scaffolds for meniscal reconstruction have been developed in a solvent-free process. As soft segments, copolymers of 50/50 L-lactide/epsilon-caprolactone have been used. After terminating the soft segment with diisocyanates, chain extension was

  6. Highly active and stereoselective zirconium and hafnium alkoxide initiators for solvent-free ring-opening polymerization of rac-lactide.

    Science.gov (United States)

    Chmura, Amanda J; Davidson, Matthew G; Frankis, Catherine J; Jones, Matthew D; Lunn, Matthew D

    2008-03-21

    Under solvent-free conditions (at 130 degrees C), zirconium and hafnium amine tris(phenolate) alkoxides are extremely active, well-controlled, single-site initiators for the ring-opening polymerization of rac-lactide, yielding highly heterotactic polylactide.

  7. The extraction of essential oil from patchouli leaves (Pogostemon cablin Benth) using microwave hydrodistillation and solvent-free microwave extraction methods

    Science.gov (United States)

    Y Putri, D. K.; Kusuma, H. S.; E Syahputra, M.; Parasandi, D.; Mahfud, M.

    2017-12-01

    Patchouli plant (Pogostemon cablin Benth) is one of the important essential oil-producing plant, contributes more than 50% of total exports of Indonesia’s essential oil. However, the extraction of patchouli oil that has been done in Indonesia is generally still used conventional methods that require enormous amount of energy, high solvent usage, and long time of extraction. Therefore, in this study, patchouli oil extraction was carried out by using microwave hydrodistillation and solvent-free microwave extraction methods. Based on this research, it is known that the extraction of patchouli oil using microwave hydrodistillation method with longer extraction time (240 min) only produced patchouli oil’s yield 1.2 times greater than solvent-free microwave extraction method which require faster extraction time (120 min). Otherwise the analysis of electric consumption and the environmental impact, the solvent-free microwave extraction method showed a smaller amount when compared with microwave hydrodistillation method. It is conclude that the use of solvent-free microwave extraction method for patchouli oil extraction is suitably method as a new green technique.

  8. Chemoselective Preparation of 1,1-Diacetates from Aldehydes, Mediated by a Keggin Heteropolyacid Under Solvent Free Conditions at Room Temperature

    Directory of Open Access Journals (Sweden)

    G. Romanelli

    2007-01-01

    Full Text Available A simple, general and efficient method has been developed for the conversion of aldehydes to 1,1-diacetates using acetic anhydride, a catalytic amount of non commercial Keggin heteropolyacid (H6 PalMo11O40 (1% mol in solvent free conditions at room temperature. Aromatic and aliphatic, simple and conjugated aldehydes were protected with excellent yields.

  9. Benign and efficient preparation of thioethers by solvent-free S-alkylation of thiols with alkyl halides catalyzed by potassium fluoride on alumina

    DEFF Research Database (Denmark)

    Nguyen, Kha Ngoc; Duus, Fritz; Luu, Thi Xuan Thi

    2016-01-01

    The preparation of thioethers by S-alkylation of various thiols with alkyl halides under solvent-free reaction conditions using potassium fluoride on alumina (KF/Al2O3) as a solid catalyst has been investigated in detail with respect to three different modes of reaction activation (ultrasound...

  10. K-10 and KSF clays as green and recyclable heterogeneous catalysts for the Cannizzaro reaction using DABCO under MWI and solvent-free conditions

    OpenAIRE

    Omid Marvi; Maryam Talakoubi

    2016-01-01

    Montmorillonite K-10 and KSF clays as recyclable and heterogeneous catalysts are used to catalyze the Cannizzaro reaction by 1,4-diazabicyclo[2.2.2]octane (DABCO) under microwave irradiation (MWI) and solvent-free conditions in excellent yields within seconds. The solid clays applied in the first cycle is recovered and reused in the subsequent reactions.

  11. Microwave-Enhanced Sulphated Zirconia and SZ/MCM-41 Catalyzed Regioselective Synthesis of β-Amino Alcohols Under Solvent-Free Conditions

    Directory of Open Access Journals (Sweden)

    Eduardo González-Zamora

    2008-04-01

    Full Text Available A solvent-free approach for the regioselective synthesis of β-amino alcohols inshorter reaction times and higher yields, compared to conventional heating is described. Itinvolves microwave (MW exposure of undiluted reactants in the presence of sulphatedzirconia (SZ or sulphated zirconia over MCM-41 (SZM as catalyst. Both acid materialscan be easily recovered and reused.

  12. Melamine trisulfonic acid as a highly efficient catalyst for the synthe-sis of 14-aryl-14H-dibenzo[a,j]xanthenes under solvent-free conditions

    Directory of Open Access Journals (Sweden)

    Abdolkarim Zare

    2014-02-01

    Full Text Available Melamine trisulfonic acid (MTSA is utilized as a highly efficient catalyst for the solvent-free condensation of 2-naphthol with arylaldehydes under conventional thermal or microwave irradiation to give 14-aryl-14H-dibenzo[a,j]xanthenes in high to excellent yields and in short reaction times.

  13. Synthesis of 1-amidoalkyl-2-naphthols based on a three-component reaction catalyzed by boric acid as a solid heterogeneous catalyst under solvent-free conditions

    Directory of Open Access Journals (Sweden)

    Zahed Karimi-Jaberi

    2012-12-01

    Full Text Available An efficient method for the preparation of 1-amidoalkyl-2-naphthols has been described using a multi-component, one-pot condensation reaction of 2-naphthol, aldehydes and amides in the presence of boric acid under solvent-free conditions.DOI: http://dx.doi.org/10.4314/bcse.v26i3.18

  14. Advances in catalysis

    CERN Document Server

    Gates, Bruce C

    2012-01-01

    Advances in Catalysis fills the gap between the journal papers and the textbooks across the diverse areas of catalysis research. For more than 60 years Advances in Catalysis has been dedicated to recording progress in the field of catalysis and providing the scientific community with comprehensive and authoritative reviews. This series in invaluable to chemical engineers, physical chemists, biochemists, researchers and industrial chemists working in the fields of catalysis and materials chemistry. * In-depth, critical, state-of-the-art reviews * Comprehensive, covers of all as

  15. Application and evaluation of solvent-free matrix-assisted laser desorption/ionization mass spectrometry for the analysis of derivatized fullerenes.

    Science.gov (United States)

    Kotsiris, Sotirios G; Vasil'ev, Yury V; Streletskii, Alexey V; Han, Ming; Mark, Lewis P; Boltalina, Olga V; Chronakis, Nikos; Orfanopoulos, Michael; Hungerbühler, Hartmut; Drewello, Thomas

    2006-01-01

    A variety of derivatized fullerenes have been studied by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. Of particular emphasis has been the evaluation of a recently introduced solvent-free sample/target preparation method. Solvent-free MALDI is particularly valuable in overcoming adverse solvent-related effects, such as insolubility and/or degradation of the sample. The method was applied to fullerene derivatives susceptible to decomposition under insufficiently "soft" MALDI conditions. Analytes included the hydrofullerene: C(60)H(36), fluorofullerenes: C(60)F(x) where x = 18, 36, 46, 48 and C(70)F(x) where x = 54, 56, methano-bridged amphiphilic ligand adducts to C(60) and the [4 + 2] cycloadduct of tetracene to C(60). The new solvent-free sample preparation is established as an exceedingly valuable addition to the repertoire of preparation protocols within MALDI. The MALDI mass spectra were of very high quality throughout, providing a testimony that "soft" MALDI conditions could be achieved. Using the [4 + 2] cycloadduct of tetracene to C(60) as the model analyte for direct comparison with solvent-based MALDI, the solvent-free approach led to less fragmentation and more abundant analyte ions. Applying solvent-free sample preparation, different matrix compounds have been examined for use in the MALDI of derivatized fullerenes, including sulfur, tetracyanoquinodimethane (TCNQ), 9-nitroanthracene (9-NA) and trans-2-[3-(4-tert-butylphenyl)-2-methyl-2- propenylidene]malononitrile (DCTB). DCTB was confirmed as the best performing matrix, reducing unwanted decomposition and suppression effects.

  16. Electromagnetic functionalized micro-ribbons and ropes for strain sensors via UV-assisted solvent-free electrospinning

    Science.gov (United States)

    He, Xiao-Xiao; Yu, Gui-Feng; Wang, Xiao-Xiong; Zhang, Jun; Zheng, Jie; Yu, Miao; Ning, Xin; Long, Yun-Ze

    2017-10-01

    Electromagnetic functionalized polyaniline/polyurethane acrylate/Fe3O4 (PANI/PUA/Fe3O4) micro-ribbons have been fabricated by UV-assisted solvent-free electrospinning. Herein, two strategies are used to fabricate the composite. One involves the direct electrospinning of PANI/PUA/Fe3O4 ribbons (the one-step method), the other involves electrospinning the PUA/Fe3O4 ribbons first, followed by the in situ polymerization of PANI on the surface of the PUA/Fe3O4 ribbons (the two-step method). The conductivity of the PANI/PUA/Fe3O4 composite produced via the two-step method can reach 2.04  ×  10-3 S·cm-1, which is 7.5  ×  102 times higher than that of the composite made via the one-step method. In particular, strain sensors based on PANI/PUA/Fe3O4 micro-ropes show a linear response to the applied strain from 0% to 199.9%, as well as a quick and repeatable response to pressure and finger motion. Meanwhile, the electromagnetic functionalized ribbons exhibit superparamagnetic behavior at 300 K. This work will provide an efficient and eco-friendly approach to fabricating multi-functional composites and devices.

  17. New 1-octanoyl-3-aryl thiourea derivatives: Solvent-free synthesis, characterization and multi-target biological activities

    Directory of Open Access Journals (Sweden)

    Fayaz Ali Larik

    2016-12-01

    Full Text Available An efficient solvent-free synthesis of a 10-member library of octanoyl linked substituted aryl thioureas was accomplished successfully. The octanoyl isothiocyanate was freshly prepared in excellent yield and purity by the reaction of potassium thiocyanate with octanoyl chloride followed by removal of potassium chloride by filtration. The reaction of the latter with a series of ten different substituted anilines by stirring at 60-65°C lead to the formation of the title compounds. The in vitro antifungal activity of newly synthesized compounds was evaluated against Aspergillus niger, A. flavus and Fusarium solani strains of pathogenic fungi. Antibacterial assay was carried out against Gram positive (Staphylococcus aureus, Micrococcus luteus and Gram negative bacterial strains (Escherichia coli, Enterobacter aerogens. Furthermore, anti-oxidant potential and enzyme inhibition studies against α-amylase and butyryl cholinestrase were performed. The results obtained indicated moderate to excellent activities of most of the compounds whilst some derivatives showed potency higher than the standard used.

  18. Esterification synthesis of ethyl oleate in solvent-free system catalyzed by lipase membrane from fermentation broth.

    Science.gov (United States)

    Li, Wei-Na; Chen, Bi-Qiang; Tan, Tian-Wei

    2011-01-01

    In this study, the immobilized lipase was prepared by fabric membrane adsorption in fermentation broth. The lipase immobilization method in fermentation broth was optimized on broth activity units and pH adjustments. The viscose fermentation broth can be used with a certain percentage of dilution based on the original broth activity units. The fermentation broth can be processed directly without pH adjustment. In addition, the oleic acid ethyl ester production in solvent-free system catalyzed by the immobilized lipase was optimized. The molar ratio of ethanol to oil acid, the enzyme amount, the molecular amount, and the temperature were 1:1, 12% (w/w), 9% (w/w)(based the total amount of reaction mixture), and 30 °C, respectively. Finally, the optimal condition afforded at least 19 reuse numbers with esterification rate above 80% under stepwise addition of ethanol. Due to simple lipase immobilization preparation, acceptable esterification result during long-time batch reactions and lower cost; the whole process was suitable for industrial ethyl oleate production.

  19. Improved interfacial adhesion in carbon fiber/polyether sulfone composites through an organic solvent-free polyamic acid sizing

    Science.gov (United States)

    Yuan, Haojie; Zhang, Shouchun; Lu, Chunxiang; He, Shuqing; An, Feng

    2013-08-01

    An organic solvent-free polyamic acid (PAA) nanoemulsion was obtained by direct ionization of the solid PAA in deionized water, with the average particle size of 261 nm and Zeta potential of -55.1 mV, and used as a carbon fiber sizing to improve the interfacial adhesion between the carbon fiber and polyether sulfone (PES). The surface characteristics of PAA coated carbon fibers were investigated using Fourier transform infrared spectroscopy, scanning electron microscopy, atomic force microscopy and dynamic contact angle measurement. The results demonstrated that a continuous and uniform PAA sizing layer was formed on the surface of carbon fibers, and the surface energy of carbon fibers increased from 42.91 to 54.55 mN/m after sizing treatment. The single fiber pull-out testing was also performed, which showed the increased interfacial shear strength (IFSS) of carbon fiber/PES composites from 33.6 to 49.7 MPa by 47.9%. The major reasons for the improved interfacial adhesion were the increased van der Waals forces between the PES matrix and sizing layer as well as the chemical bonding between the sizing layer and carbon fiber surface. Furthermore, the PAA sizing also presented a positive effect on the interfacial adhesion of carbon fiber/PES composites under hydrothermal condition.

  20. Optimization of 2-ethylhexyl palmitate production using lipozyme RM IM as catalyst in a solvent-free system.

    Science.gov (United States)

    Richetti, Aline; Leite, Selma G F; Antunes, Octávio A C; de Souza, Andrea L F; Lerin, Lindomar A; Dallago, Rogério M; Paroul, Natalia; Di Luccio, Marco; Oliveira, J Vladimir; Treichel, Helen; de Oliveira, Débora

    2010-04-01

    This work reports the application of a lipase in the 2-ethylhexyl palmitate esterification in a solvent-free system with an immobilized lipase (Lipozyme RM IM). A sequential strategy was used applying two experimental designs to optimize the 2-ethylhexyl palmitate production. An empirical model was then built so as to assess the effects of process variables on the reaction conversion. Afterwards, the operating conditions that optimized 2-ethylhexyl palmitate production were established as being acid/alcohol molar ratio 1:3, temperature of 70 degrees C, stirring rate of 150 rpm, 10 wt.% of enzyme, leading to a reaction conversion as high as 95%. From this point, a kinetic study was carried out evaluating the effect of acid:alcohol molar ratio, the enzyme concentration and the temperature on product conversion. The results obtained in this step permit to verify that an excess of alcohol (acid to alcohol molar ratio of 1:6), relatively low enzyme concentration (10 wt.%) and temperature of 70 degrees C, led to conversions next to 100%.

  1. Development of solvent-free offset ink using vegetable oil esters and high molecular-weight resin.

    Science.gov (United States)

    Park, Jung Min; Kim, Young Han; Kim, Sung Bin

    2013-01-01

    In the development of solvent-free offset ink, the roles of resin molecular weight and used solvent on the ink performance were evaluated by examining the relationship between the various properties of resin and solvent and print quality. To find the best performing resin, the soy-oil fatty acid methyl ester (FAME) was applied to the five modified-phenolic resins having different molecular weights. It is found from the experimental results that the ink made of higher molecular weight and better solubility resin gives better printability and print quality. It is because larger molecular weight resin with better solubility gives higher rate of ink transfer. From the ink application of different esters to high molecular weight resin, the best printing performance was yielded from the soy-oil fatty acid butyl ester (FABE). It is due to its high kinematic viscosity resulting in the smallest change of ink transfer weight upon multiple number of printing, which improves the stability of ink quality.

  2. A Solvent-Free Surface Suspension Melt Technique for Making Biodegradable PCL Membrane Scaffolds for Tissue Engineering Applications

    Directory of Open Access Journals (Sweden)

    Ratima Suntornnond

    2016-03-01

    Full Text Available In tissue engineering, there is limited availability of a simple, fast and solvent-free process for fabricating micro-porous thin membrane scaffolds. This paper presents the first report of a novel surface suspension melt technique to fabricate a micro-porous thin membrane scaffolds without using any organic solvent. Briefly, a layer of polycaprolactone (PCL particles is directly spread on top of water in the form of a suspension. After that, with the use of heat, the powder layer is transformed into a melted layer, and following cooling, a thin membrane is obtained. Two different sizes of PCL powder particles (100 µm and 500 µm are used. Results show that membranes made from 100 µm powders have lower thickness, smaller pore size, smoother surface, higher value of stiffness but lower ultimate tensile load compared to membranes made from 500 µm powder. C2C12 cell culture results indicate that the membrane supports cell growth and differentiation. Thus, this novel membrane generation method holds great promise for tissue engineering.

  3. Improved interfacial adhesion in carbon fiber/polyether sulfone composites through an organic solvent-free polyamic acid sizing

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, Haojie [National Engineering Laboratory for carbon fiber technology, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Zhang, Shouchun, E-mail: zschun@sxicc.ac.cn [National Engineering Laboratory for carbon fiber technology, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001 (China); Lu, Chunxiang, E-mail: chunxl@sxicc.ac.cn [National Engineering Laboratory for carbon fiber technology, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001 (China); He, Shuqing [National Engineering Laboratory for carbon fiber technology, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); An, Feng [National Engineering Laboratory for carbon fiber technology, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001 (China)

    2013-08-15

    An organic solvent-free polyamic acid (PAA) nanoemulsion was obtained by direct ionization of the solid PAA in deionized water, with the average particle size of 261 nm and Zeta potential of −55.1 mV, and used as a carbon fiber sizing to improve the interfacial adhesion between the carbon fiber and polyether sulfone (PES). The surface characteristics of PAA coated carbon fibers were investigated using Fourier transform infrared spectroscopy, scanning electron microscopy, atomic force microscopy and dynamic contact angle measurement. The results demonstrated that a continuous and uniform PAA sizing layer was formed on the surface of carbon fibers, and the surface energy of carbon fibers increased from 42.91 to 54.55 mN/m after sizing treatment. The single fiber pull-out testing was also performed, which showed the increased interfacial shear strength (IFSS) of carbon fiber/PES composites from 33.6 to 49.7 MPa by 47.9%. The major reasons for the improved interfacial adhesion were the increased van der Waals forces between the PES matrix and sizing layer as well as the chemical bonding between the sizing layer and carbon fiber surface. Furthermore, the PAA sizing also presented a positive effect on the interfacial adhesion of carbon fiber/PES composites under hydrothermal condition.

  4. Solvent-Free Synthesis of Zeolite Crystals Encapsulating Gold-Palladium Nanoparticles for the Selective Oxidation of Bioethanol.

    Science.gov (United States)

    Zhang, Jian; Wang, Liang; Zhu, Longfeng; Wu, Qinming; Chen, Chunyu; Wang, Xiong; Ji, Yanyan; Meng, Xiangju; Xiao, Feng-Shou

    2015-09-07

    The conversion of bioethanol into valuable products is an important area in the conversion of biomass. We demonstrate the successful synthesis of bimetallic gold-palladium (Au-Pd) nanoparticles encapsulated within S-1 zeolite crystals (AuPd@S-1) by a solvent-free strategy. This strategy allows highly efficient use of the noble metals, with more than 96 % of the gold and palladium being loaded into the final samples. Electron microscopy characterization and investigations with probe molecules confirm that the Au-Pd nanoparticles are encapsulated inside the S-1 crystals. The AuPd@S-1 catalyst is very active for the aerobic oxidation of bioethanol, giving 100 % conversion and 99 % selectivity to acetic acid. Even in the presence of 90 % water, the catalyst still gives a conversion higher than 80 % and a selectivity of 95 %. More importantly, the AuPd@S-1 catalyst exhibits excellent stability in the oxidation of bioethanol. These features are important for future practical applications of the AuPd@S-1 catalyst. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Solvent-Free Microwave-Assisted Extraction of Polyphenols from Olive Tree Leaves: Antioxidant and Antimicrobial Properties

    Directory of Open Access Journals (Sweden)

    Selin Şahin

    2017-06-01

    Full Text Available Response surface methodology (RSM and artificial neural networks (ANN were evaluated and compared in order to decide which method was the most appropriate to predict and optimize total phenolic content (TPC and oleuropein yields in olive tree leaf (Olea europaea extracts, obtained after solvent-free microwave-assisted extraction (SFMAE. The SFMAE processing conditions were: microwave irradiation power 250–350 W, extraction time 2–3 min, and the amount of sample 5–10 g. Furthermore, the antioxidant and antimicrobial activities of the olive leaf extracts, obtained under optimal extraction conditions, were assessed by several in vitro assays. ANN had better prediction performance for TPC and oleuropein yields compared to RSM. The optimum extraction conditions to recover both TPC and oleuropein were: irradiation power 250 W, extraction time 2 min, and amount of sample 5 g, independent of the method used for prediction. Under these conditions, the maximal yield of oleuropein (0.060 ± 0.012 ppm was obtained and the amount of TPC was 2.480 ± 0.060 ppm. Moreover, olive leaf extracts obtained under optimum SFMAE conditions showed antibacterial activity against S. aureus and S. epidermidis, with a minimum inhibitory concentration (MIC value of 1.25 mg/mL.

  6. Orthogonal protection of saccharide polyols through solvent-free one-pot sequences based on regioselective silylations

    Directory of Open Access Journals (Sweden)

    Serena Traboni

    2016-12-01

    Full Text Available tert-Butyldimethylsilyl (TBDMS and tert-butyldiphenylsilyl (TBDPS are alcohol protecting groups widely employed in organic synthesis in view of their compatibility with a wide range of conditions. Their regioselective installation on polyols generally requires lengthy reactions and the use of high boiling solvents. In the first part of this paper we demonstrate that regioselective silylation of sugar polyols can be conducted in short times with the requisite silyl chloride and a very limited excess of pyridine (2–3 equivalents. Under these conditions, that can be regarded as solvent-free conditions in view of the insolubility of the polyol substrates, the reactions are faster than in most examples reported in the literature, and can even be further accelerated with a catalytic amount of tetrabutylammonium bromide (TBAB. The strategy proved also useful for either the selective TBDMS protection of secondary alcohols or the fast per-O-trimethylsilylation of saccharide polyols. In the second part of the paper the scope of the silylation approach was significantly extended with the development of unprecedented “one-pot” and “solvent-free” sequences allowing the regioselective silylation/alkylation (or the reverse sequence of saccharide polyols in short times. The developed methodologies represent a very useful and experimentally simple tool for the straightforward access to saccharide building-blocks useful in organic synthesis.

  7. Asymmetric total synthesis of Apocynaceae hydrocarbazole alkaloids (+)-deethylibophyllidine and (+)-limaspermidine.

    Science.gov (United States)

    Du, Ji-Yuan; Zeng, Chao; Han, Xiao-Jie; Qu, Hu; Zhao, Xian-He; An, Xian-Tao; Fan, Chun-An

    2015-04-01

    An unprecedented asymmetric catalytic tandem aminolysis/aza-Michael addition reaction of spirocyclic para-dienoneimides has been designed and developed through organocatalytic enantioselective desymmetrization. A unified strategy based on this key tandem methodology has been divergently explored for the asymmetric total synthesis of two natural Apocynaceae alkaloids, (+)-deethylibophyllidine and (+)-limaspermidine. The present studies not only enrich the tandem reaction design concerning the asymmetric catalytic assembly of a chiral all-carbon quaternary stereocenter contained in the densely functionalized hydrocarbazole synthons but also manifest the potential for the application of the asymmetric catalysis based on the para-dienone chemistry in asymmetric synthesis of natural products.

  8. Asymmetric fluorocyclizations of alkenes.

    Science.gov (United States)

    Wolstenhulme, Jamie R; Gouverneur, Véronique

    2014-12-16

    CONSPECTUS: The vicinal fluorofunctionalization of alkenes is an attractive transformation that converts feedstock olefins into valuable cyclic fluorinated molecules for application in the pharmaceutical, agrochemical, medical, and material sectors. The challenges associated with asymmetric fluorocyclizations induced by F(+) reagents are distinct from other types of halocyclizations. Processes initiated by the addition of an F(+) reagent onto an alkene do not involve the reversible formation of bridged fluoronium ions but generate acyclic β-fluorocationic intermediates. This mechanistic feature implies that fluorocyclizations are not stereospecific. A discontinuity exists between the importance of this class of fluorocyclization and the activation modes currently available to implement successful catalysis. Progress toward fluorocyclization has been achieved by investing in neutral and cationic [NF] reagent development. The body of work on asymmetric fluorination using chiral cationic [NF](+) reagents prepared by fluorine transfer from the dicationic [NF](2+) reagent Selectfluor to quinuclidines, inspired the development of asymmetric F(+)-induced fluorocyclizations catalyzed by cinchona alkaloids; for catalysis, the use of N-fluorobenzenesulfonimide, which is less reactive than Selectfluor, ensures that the achiral F(+) source remains unreactive toward the alkene. These organocatalyzed enantioselective fluorocyclizations can be applied to indoles to install the fluorine on a quaternary benzylic stereogenic carbon center and to afford fluorinated analogues of natural products featuring the hexahydropyrrolo[2,3-b]indole or the tetrahydro-2H-furo[2,3-b]indole skeleton. In an alternative approach, the poor solubility of dicationic Selectfluor bis(tetrafluoroborate) in nonpolar solvent was exploited with anionic phase transfer catalysis as the operating activation mode. Exchange of the tetrafluoroborate ions of Selectfluor with bulky lipophilic chiral anions (e

  9. High ambient dc and ac conductivities in solvent-free, low-dimensional polymer electrolyte blends with lithium salts

    Energy Technology Data Exchange (ETDEWEB)

    Yungui Zheng; Fusiong Chia; Ungar, G.; Wright, P.V. [Sheffield Univ. (United Kingdom). Dept. of Engineering Materials; Richardson, T.H. [Sheffield Univ. (United Kingdom). Dept. of Physics

    2001-07-01

    Measurements of dc conductivity on solvent-free, low dimensional polymer electrolyte complexes with lithium salts using Li metal electrodes and giving{sigma} = 10{sup -3} S cm{sup -1} at 25-40{sup o}C are reported. The materials are blends of the amphiphilic helical polyethers poly[2,5,8,11,14-pentaoxapentadecamethylene(5-alkyloxy-1,3-phenylene)] , coded CmO5 or (I) (where m = 16, 18 or equimolar 12/16 mixture is the number of carbon atoms in the n-alkyl side chains), and a polytetrahydrofuran copolymer (II) with various Li salts. Heptamer segments of II are in equimolar proportion to the repeating units of I. In Li | I:II:Li salt | Li cells, dc conductivities of 1 x 10{sup -3} to 3 x 10{sup -3} S cm{sup -1} are achieved by an apparent 'self-tracking' process from a low level (10{sup -7}-10{sup -6} S cm{sup -1}) over 12 to 24 h. The dc results are complemented by ac impedance spectroscopy measurements with ITO electrodes that show a 'transformation' from the low level up to 6 x 10{sup -4} S cm{sup -1} at 20{sup o}C after a heating excursion to 100{sup o}C. The ac data also demonstrate temperature-independent conductivity, with {sigma} = 8 x 10{sup -5} S cm{sup -1} at -5{sup o}C. X-ray diffraction, thermal analysis and molecular dynamics modelling suggest a structure that would allow Li{sup +} to be mobile in the polyether helices of I whilst anions are mobile in the unimpeded spaces between them. Ions transfer between the pathways of I via a matrix of II when the polymers are intimately blended. (author)

  10. Silica sulfuric acid: a reusable solid catalyst for one pot synthesis of densely substituted pyrrole-fused isocoumarins under solvent-free conditions

    Directory of Open Access Journals (Sweden)

    Sudipta Pathak

    2013-11-01

    Full Text Available A convenient and efficient methodology for the synthesis of densely substituted pyrrole-fused isocoumarins, which employs solid-supported silica sulfuric acid (SSA as catalyst, has been developed. When the mixture of ninhydrin adducts of acetylacetone/ethyl acetoacetate and primary amines was heated on the solid surface of SSA under solvent-free conditions, the pyrrole-fused isocoumarins were formed in good yields. This synthetic method has several advantages such as the employment of solvent-free reaction conditions without the use of any toxic reagents and metal catalysts, the ease of product isolation, the use of a recyclable catalyst, the low cost, the easy availability of the starting materials, and the excellent yields of products.

  11. Nanocrystalline MgAl2O4 as an efficient catalyst for one-pot synthesis of multisubstituted imidazoles under solvent-free conditions

    Directory of Open Access Journals (Sweden)

    Javad Safari

    2016-09-01

    Full Text Available An efficient and eco-friendly procedure has been developed using nanocrystalline MgAl2O4 with specific surface area as catalyst for rapid and an improved synthesis of 2,4,5-trisubstituted and 1,2,4,5-tetrasubstituted imidazoles under solvent-free conditions in excellent yields. The method has several benefits, such as shorter reaction time, recyclable catalyst and excellent yields.

  12. A facile solvent-free Synthesis Route for the Assembly of Highly CO2 Selective and H2S tolerant NiSIFSIX Metal-Organic Framework

    KAUST Repository

    Eddaoudi, Mohamed

    2015-07-06

    The development of materials for CO2 capture with high selectivity and high tolerance to H2S is of prime importance for various industrially relevant gas streams (e.g. natural gas and biogas upgrading as well as pre-combustion capture). Here, we report the successful fabrication of a MOF with combined exceptional CO2 capture properties and H2S tolerance, namely Ni SIFSIX based-MOF using both solvothermal and solvent-free methodologies.

  13. Salen complexes of zirconium and hafnium: synthesis, structural characterization, controlled hydrolysis, and solvent-free ring-opening polymerization of cyclic esters and lactides.

    Science.gov (United States)

    Saha, Tanmoy Kumar; Ramkumar, Venkatachalam; Chakraborty, Debashis

    2011-04-04

    Dinuclear salen compounds of zirconium and hafnium are efficient initiators for the solvent-free ring-opening polymerization of cyclic ester monomers and lactides. There is a correlation between the theoretical and experimental number-average molecular weights (M(n)'s) in these polymerizations. Polymerization of β-butyrolactone gives poly(3-hydroxybutyrate) with a good M(n) and molecular weight distribution.

  14. One-pot solvent-free rapid and green synthesis of 3,4-dihydropyrano[c]chromenes using grindstone chemistry

    Directory of Open Access Journals (Sweden)

    Devji S. Patel

    2016-09-01

    Full Text Available An easy solvent-free method is described for the synthesis of 3,4-dihydropyrano[c]chromenes by a one pot three component coupling reaction of aromatic aldehydes, malononitrile, and 4-hydroxycoumarin using basic ionic liquid as the catalyst by grindstone chemistry. The salient features of this one pot protocol are short reaction times, cleaner reaction profiles and simple workup.

  15. Lithium bromide as a flexible, mild, and recyclable reagent for solvent-free Cannizzaro, Tishchenko, and Meerwein-Ponndorf-Verley reactions.

    Science.gov (United States)

    Mojtahedi, Mohammad M; Akbarzadeh, Elahe; Sharifi, Roholah; Abaee, M Saeed

    2007-07-19

    A room temperature convenient disproportionation or reduction of aldehydes prompted by lithium bromide and triethylamine is described in a solvent-free environment. Distribution of the products to selectively direct the process toward Cannizzaro or Tishchenko reactions is controlled by the type of workup selection. The presence of hydrogen donor alcohols in the mixture completely diverts the process toward the Meerwein-Ponndorf-Verley reaction.

  16. Microwave-Assisted Condensation Reactions of Acetophenone Derivatives and Activated Methylene Compounds with Aldehydes Catalyzed by Boric Acid under Solvent-Free Conditions.

    Science.gov (United States)

    Brun, Elodie; Safer, Abdelmounaim; Carreaux, François; Bourahla, Khadidja; L'helgoua'ch, Jean-Martial; Bazureau, Jean-Pierre; Villalgordo, Jose Manuel

    2015-06-23

    We here disclosed a new protocol for the condensation of acetophenone derivatives and active methylene compounds with aldehydes in the presence of boric acid under microwave conditions. Implementation of the reaction is simple, healthy and environmentally friendly owing to the use of a non-toxic catalyst coupled to a solvent-free procedure. A large variety of known or novel compounds have thus been prepared, including with substrates bearing acid or base-sensitive functional groups.

  17. Microwave-Assisted Condensation Reactions of Acetophenone Derivatives and Activated Methylene Compounds with Aldehydes Catalyzed by Boric Acid under Solvent-Free Conditions

    Directory of Open Access Journals (Sweden)

    Elodie Brun

    2015-06-01

    Full Text Available We here disclosed a new protocol for the condensation of acetophenone derivatives and active methylene compounds with aldehydes in the presence of boric acid under microwave conditions. Implementation of the reaction is simple, healthy and environmentally friendly owing to the use of a non-toxic catalyst coupled to a solvent-free procedure. A large variety of known or novel compounds have thus been prepared, including with substrates bearing acid or base-sensitive functional groups.

  18. Marine Sponge/H3PO4: As a Naturally Occurring Chiral Catalyst for Solvent-free Fischer-Indole Synthesis.

    Science.gov (United States)

    Shushizadeh, Mohammad Reza; Mostoufi, Azar; Badri, Rashid; Azizyan, Somaye

    2013-11-01

    A new and efficient method have been developed for the synthesis of different indole derivatives from various ketones, having at least one hydrogen atom attached to each of their α-carbon atoms, and hydrazines in solvent-free conditions, using marine sponge/H3PO4 as a naturally occurring chiral catalyst. This study recommended the use of marine sponge/H3PO4 as a naturally occurring chiral catalyst for preparation of phenylhydrazones from ketones having one α-hydrogen and subsequent cyclisation of the products to indoles. The reaction was carried out by mixing the phenylhydrazine, ketone, and marine sponge/H3PO4 powder in mortar and pestle; the mixture was ground at room temperature in an appropriate time until TLC show the completion of the reaction. The product extracted by CH2Cl2 and evaporation of solvent yields the products. In this research work, several indoles are synthesized using phenylhydrazine and aliphatic or aromatic ketone as starting materials, in the presence of marine sponge/H3PO4 powder as a natural catalyst under solvent-free condition. We found marine sponge/H3PO4 to be an effective catalyst for indolisation of phenylhydrazones from ketones having α-hydrogens in solvent-free conditions.

  19. Catalysis seen in action

    NARCIS (Netherlands)

    Tromp, M.

    2015-01-01

    Synchrotron radiation techniques are widely applied in materials research and heterogeneous catalysis. In homogeneous catalysis, its use so far is rather limited despite its high potential. Here, insights in the strengths and limitations of X-ray spectroscopy technique in the field of homogeneous

  20. New mechanistic aspects of the asymmetric homogeneous hydrogenation of alkenes.

    Science.gov (United States)

    Brown, J M; Giernoth, R

    2000-11-01

    Progress in homogeneous catalysis depends upon an understanding of the reaction mechanism; in asymmetric catalysis this entails an insight into the origins of enantioselectivity. Significant advances have been made in the area of alkene reduction catalyzed by rhodium or ruthenium complexes, which has been in tandem with the development of new, more effective ligands for the reaction. The combination of quantum chemical calculations and direct spectroscopic observation of catalytic intermediates has proved powerful in this regard.

  1. Surface and nanomolecular catalysis

    CERN Document Server

    Richards, Ryan

    2006-01-01

    Using new instrumentation and experimental techniques that allow scientists to observe chemical reactions and molecular properties at the nanoscale, the authors of Surface and Nanomolecular Catalysis reveal new insights into the surface chemistry of catalysts and the reaction mechanisms that actually occur at a molecular level during catalysis. While each chapter contains the necessary background and explanations to stand alone, the diverse collection of chapters shows how developments from various fields each contributed to our current understanding of nanomolecular catalysis as a whole. The

  2. Molecular water oxidation catalysis

    CERN Document Server

    Llobet, Antoni

    2014-01-01

    Photocatalytic water splitting is a promising strategy for capturing energy from the sun by coupling light harvesting and the oxidation of water, in order to create clean hydrogen fuel. Thus a deep knowledge of the water oxidation catalysis field is essential to be able to come up with useful energy conversion devices based on sunlight and water splitting. Molecular Water Oxidation Catalysis: A Key Topic for New Sustainable Energy Conversion Schemes presents a comprehensive and state-of-the-art overview of water oxidation catalysis in homogeneous phase, describing in detail the most importan

  3. Multicomponent, Solvent-Free Synthesis of 1-Amidoalkyl-2-naphthols in the Presence of H3+xPMo12-x Vx O40 Heteropolyacids as Recyclable and Green Catalysts

    Directory of Open Access Journals (Sweden)

    Fatemeh F. Bamoharram

    2011-01-01

    Full Text Available A rapid and efficient one-pot method for the synthesis of 1-amidoalkyl-2-naphthols has been developed in the presence of mixed-addenda vanadium(V-substituted polyoxomolybdates including: H3+xPMo12-xVxO40 (x=1-3 heteropolyacids (HPAs as recyclable catalysts under solvent-free conditions. In all cases heteropolyacid with x = 3 gave the highest yield under solvent-free conditions.

  4. Research on Catalysis.

    Science.gov (United States)

    Bartholomew, Calvin H.; Hecker, William C.

    1984-01-01

    The objectives and philosophy of the Catalysis Laboratory at Brigham Young University are discussed. Also discusses recent and current research activities at the laboratory as well as educational opportunities, research facilities, and sources of research support. (JN)

  5. Solvent-Free Lipase-Catalyzed Synthesis of Technical-Grade Sugar Esters and Evaluation of Their Physicochemical and Bioactive Properties

    Directory of Open Access Journals (Sweden)

    Ran Ye

    2016-05-01

    Full Text Available Technical-grade oleic acid esters of sucrose and fructose were prepared using solvent-free biocatalysis at 65 °C, without any downstream purification applied, and their physicochemical and bioactivity-related properties were evaluated and compared to a commercially available sucrose laurate emulsifier. To increase the conversion of sucrose and fructose oleate, prepared previously using solvent-free lipase-catalyzed esterification catalyzed by Rhizomucor miehei lipase (81% and 83% ester, respectively, the enzymatic reaction conditions was continued using CaSO4 to control the reactor’s air headspace and a lipase (from Candida antarctica B with a hydrophobic immobilization matrix to provide an ultralow water activity, and high-pressure homogenation, to form metastable suspensions of 2.0–3.3 micron sized saccharide particles in liquid-phase reaction media. These measures led to increased ester content of 89% and 96% for reactions involving sucrose and fructose, respectively. The monoester content among the esters decreased from 90% to <70% due to differences in regioselectivity between the lipases. The resultant technical-grade sucrose and fructose lowered the surface tension to <30 mN/m, and possessed excellent emulsification capability and stability over 36 h using hexadecane and dodecane as oils, comparable to that of sucrose laurate and Tween® 80. The technical-grade sugar esters, particularly fructose oleate, more effectively inhibited gram-positive foodborne pathogens (Lactobacillus plantarum, Pediococcus pentosaceus and Bacillus subtilis. Furthermore, all three sugar esters displayed antitumor activity, particularly the two sucrose esters. This study demonstrates the importance of controlling the biocatalysts’ water activity to achieve high conversion, the impact of a lipase’s regioselectivity in dictating product distribution, and the use of solvent-free biocatalysis to important biobased surfactants useful in foods, cosmetics

  6. Hydroxamic acids in asymmetric synthesis.

    Science.gov (United States)

    Li, Zhi; Yamamoto, Hisashi

    2013-02-19

    Metal-catalyzed stereoselective reactions are a central theme in organic chemistry research. In these reactions, the stereoselection is achieved predominantly by introducing chiral ligands at the metal catalyst's center. For decades, researchers have sought better chiral ligands for asymmetric catalysis and have made great progress. Nevertheless, to achieve optimal stereoselectivity and to catalyze new reactions, new chiral ligands are needed. Because of their high metal affinity, hydroxamic acids play major roles across a broad spectrum of fields from biochemistry to metal extraction. Dr. K. Barry Sharpless first revealed their potential as chiral ligands for asymmetric synthesis in 1977: He published the chiral vanadium-hydroxamic-acid-catalyzed, enantioselective epoxidation of allylic alcohols before his discovery of Sharpless asymmetric epoxidation, which uses the titanium-tartrate complex as the chiral reagent. However, researchers have reported few highly enantioselective reactions using metal-hydroxamic acid as catalysts since then. This Account summarizes our research on metal-catalyzed asymmetric epoxidation using hydroxamic acids as chiral ligands. We designed and synthesized a series of new hydroxamic acids, most notably the C2-symmetric bis-hydroxamic acid (BHA) family. V-BHA-catalyzed epoxidation of allylic and homoallylic alcohols achieved higher activity and stereoselectivity than Sharpless asymmetric epoxidation in many cases. Changing the metal species led to a series of unprecedented asymmetric epoxidation reactions, such as (i) single olefins and sulfides with Mo-BHA, (ii) homoallylic and bishomoallylic alcohols with Zr- and Hf-BHA, and (iii) N-alkenyl sulfonamides and N-sulfonyl imines with Hf-BHA. These reactions produce uniquely functionalized chiral epoxides with good yields and enantioselectivities.

  7. Nano-SbCl5/SiO2 as an Efficient Catalyst for One-Pot Synthesis of 2, 4, 5-Trisubstituted Imidazoles Under Solvent- Free Condition

    Directory of Open Access Journals (Sweden)

    A. Bamoniri

    2012-06-01

    Full Text Available A general synthetic route to the synthesis of imidazoles has been developed using nano SbCl5/SiO2 under solvent-free conditions. The multi-component reactions of aldehydes, benzil and ammonium acetate were carried out to afford some trisubstituted imidazole derivatives. This method provides several advantages like simple work-up, environmentally benign, and shorter reaction times along with high yields. The mentioned nano catalyst was investigated by SEM, TEM and XRD. Meanwhile, structures of trisubstituted imidazoles were elucidated by FT-IR, 1 H NMR and 13 C NMR spectra.

  8. Solvent-free microwave extraction of essential oils from Laurus nobilis and Melissa officinalis: comparison with conventional hydro-distillation and ultrasound extraction.

    Science.gov (United States)

    Uysal, Burcu; Sozmen, Fazli; Buyuktas, Birsen S

    2010-01-01

    Solvent-free microwave extraction (SFME) has been applied to the extraction of essential oils from Melissa officinalis L. and Laurus nobilis L. The results of SFME were compared with those obtained by hydro-distillation (HD) and ultrasound-assisted extraction (USE) of essential oils from dried plant materials. The compositions of the essential oils were identified by GC-MS. The essential oil obtained with SFME contained substantially higher amounts of oxygenated compounds and lower amounts of monoterpenes than the oils obtained by conventional methods. The three different extraction methods used showed differences in the compositions and contents of the essential oils.

  9. Solvent-free and time-efficient Suzuki–Miyaura reaction in a ball mill: the solid reagent system KF–Al2O3 under inspection

    Directory of Open Access Journals (Sweden)

    Franziska Bernhardt

    2010-01-01

    Full Text Available Although a plethora of synthetic procedures mediated by KF-loaded aluminas is available in the literature, there is almost no data concerning the influence of parameters such as alumina modification or KF-loading on experimental results. Hence, the Pd-catalyzed, solvent-free Suzuki–Miyaura reaction was chosen as model reaction to investigate the effect of the above mentioned parameters on the results of coupling reactions. The results from ball milling experiments led to the conclusion that self-prepared and commercially available KF–Al2O3 differ in water content. The higher the residual water content, the higher are the product yields.

  10. Facile synthesis of 1-naphthol azo dyes with nano SiO2/HIO4 under solvent-free conditions

    OpenAIRE

    A.R. Pourali; A. Bamoniri; S.M.R. Nazifi

    2013-01-01

    Nano-silica supported periodic acid (nano-SPIA) has been utilized as a heterogeneous reagent for a highly efficient and one pot synthesis of azo dyes based on 1-naphthol under solvent-free conditions at room temperature. This method has some advantages, the reaction workup is very easy and the catalyst can be easily separated from the reaction mixture and one-pot procedure. The related products have been obtained in good to excellent yields, high purity and short reaction times. The structure...

  11. Synthesis of Azanucleosides through Regioselective Ring-Opening of Epoxides Catalyzed by Sulphated Zirconia under Microwave and Solvent-Free Conditions

    Directory of Open Access Journals (Sweden)

    Guillermo E. Negrón-Silva

    2012-03-01

    Full Text Available New azanucleosides were obtained using sulphated zirconia (ZS as catalyst in the nucleophilic oxirane ring opening reaction of 1-allyl-3-(oxiran-2-ylmethyl pyrimidine-2,4(1H,3H-dione and 1-allyl-5-methyl-3-(oxiran-2-ylmethyl-pyrimidine-2,4(1H,3H-dione, with (S-prolinol. The new templates were obtained with good yields following a route which exploits the reactivity of epoxides in the presence of sulphated zirconia as catalyst. The key step was carried out using microwave and solvent-free conditions and proceeds with high selectivity.

  12. SbCl3-catalyzed one-pot synthesis of 4,4′-diaminotriarylmethanes under solvent-free conditions: Synthesis, characterization, and DFT studies

    Directory of Open Access Journals (Sweden)

    Ghasem Rezanejade Bardajee

    2011-01-01

    Full Text Available A simple, efficient, and mild procedure for a solvent-free one-step synthesis of various 4,4′-diaminotriarylmethane derivatives in the presence of antimony trichloride as catalyst is described. Triarylmethane derivatives were prepared in good to excellent yields and characterized by elemental analysis, FTIR, 1H and 13C NMR spectroscopic techniques. The structural and vibrational analysis were investigated by performing theoretical calculations at the HF and DFT levels of theory by standard 6-31G*, 6-31G*/B3LYP, and B3LYP/cc-pVDZ methods and good agreement was obtained between experimental and theoretical results.

  13. Switching-off toluene formation in the solvent-free oxidation of benzyl alcohol using supported trimetallic Au-Pd-Pt nanoparticles.

    Science.gov (United States)

    He, Qian; Miedziak, Peter J; Kesavan, Lokesh; Dimitratos, Nikolaos; Sankar, Meenakshisundaram; Lopez-Sanchez, Jose Antonio; Forde, Michael M; Edwards, Jennifer K; Knight, David W; Taylor, Stuart H; Kiely, Christopher J; Hutchings, Graham J

    2013-01-01

    Trimetallic Au-Pd-Pt nanoparticles have been supported on activated carbon by the sol-immobilisation method. They are found to be highly active and selective catalysts for the solvent-free aerobic oxidation of benzyl alcohol. The addition of Pt promotes the selectivity to the desired product benzaldehyde at the expense of toluene formation. Detailed aberration corrected STEM-XEDS analysis confirmed that the supported particles are indeed Au-Pd-Pt ternary alloys, but also identified composition fluctuations from particle-to-particle which vary systematically with nanoparticle size.

  14. Tetrabutylammonium Bromide Media Aza-Michael Addition of 1,2,3,6-Tetrahydrophthalimide to Symmetrical Fumaric Esters and Acrylic Esters under Solvent-Free Conditions

    Directory of Open Access Journals (Sweden)

    Mohammadreza Zamanloo

    2010-10-01

    Full Text Available The aza-Michael addition of 1,2,3,6-tetrahydrophthalimide with symmetrical fumaric esters has been performed efficiently in a solvent-free system at 100 °C and using 1,4-diazabicyclo[2.2.2]octane (DABCO as a base in the presence of tetrabutylammonium bromide (TBAB. The products were obtained in good to high yields within 2.5-7.0 h. This reaction worked well on linear alkyl fumarates and was not effective with nonlinear alkyl fumarates. Although the reaction was also applicable to acrylates such as n-butyl acrylate, methacrylates and crotonates were not suitable Michael acceptors for this reaction.

  15. ZnS nanoparticles as an efficient and reusable heterogeneous catalyst for synthesis of 1-substituted-1 H-tetrazoles under solvent-free conditions

    Science.gov (United States)

    Naeimi, Hossein; Kiani, Fatemeh; Moradian, Mohsen

    2014-09-01

    An efficient and green protocol for the synthesis of 1-substituted-1 H-tetrazoles through cyclization reaction of various primary amines, sodium azide, and triethyl orthoformate was described. In this method, a series of tetrazole derivatives was synthesized by using ZnS nanoparticles as an effective, recoverable, and reusable catalyst under solvent-free conditions. This strategy is a magnificent improvement for the synthesis of these heterocycles due to the non-acidic, clean, and solvent-free conditions via a solid recyclable catalyst. The catalyst was separated by simple filtration and reused seven times without significant loss of activity. The ZnS nanoparticles with high surface area and fine monodisperse particles were prepared using the simple microwave-assisted method without using any surfactant. The ZnS nanoparticle catalyst is a good candidate to replace brønsted acids and metal salts or other catalyst for the preparation of 1-substituted-1 H-tetrazoles in high yields and has potential values for industrial applications.

  16. Functionalized SBA-15 supported nickel (II)–oxime–imine catalysts for liquid phase oxidation of olefins under solvent-free conditions

    Energy Technology Data Exchange (ETDEWEB)

    Paul, Luna [Department of Chemistry, Jadavpur University, Kolkata 700 032 (India); Banerjee, Biplab [Department of Materials Science, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032 (India); Bhaumik, Asim, E-mail: msab@iacs.res.in [Department of Materials Science, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032 (India); Ali, Mahammad, E-mail: m_ali2062@yahoo.com [Department of Chemistry, Jadavpur University, Kolkata 700 032 (India)

    2016-05-15

    A new oxime–imine functionalized highly ordered mesoporous SBA-15 (SBA-15-NH{sub 2}-DAMO) has been synthesized via post-synthesis functionalization of SBA-15 with 3-aminopropyl-triethoxysilane followed by the Schiff base condensation with diacetylmonooxime, which was further reacted with Ni(ClO{sub 4}){sub 2} to yield the functionalized nickel catalyst SBA-15-NH{sub 2}-DAMO-Ni. All the synthesized materials were thoroughly characterized using different characterization techniques. It was found that SBA-15-NH{sub 2}-DAMO-Ni catalyzes the one-pot oxidation of olefins like styrene, cyclohexene, cyclooctene, 1-hexene and 1-octene to the corresponding benzaldehyde, cyclohexene-1-ol and cyclooctene-oxide, respectively under solvent-free conditions by using tert-butylhydroperoxide as oxidant. - Graphical abstract: A new well characterized oxime–imine functionalized highly ordered mesoporous SBA-15-NH{sub 2}-DAMO-Ni complex catalyzes the one-pot oxidation of olefins under solvent free mild conditions.

  17. Solvent-free microwave extraction coupled with headspace single-drop microextraction of essential oils from flower of Eugenia caryophyllata Thunb.

    Science.gov (United States)

    Jiang, Chunzhu; Sun, Ying; Zhu, Xiaonan; Gao, Yan; Wang, Liying; Wang, Jian; Wu, Liwei; Song, Daqian

    2010-09-01

    Solvent-free microwave extraction coupled with headspace single-drop microextraction was developed for extracting the essential oils from Eugenia caryophyllata Thunb. Carbonyl iron powders were mixed with the sample to extract essential oils from the dried plant materials and single-drop solvent was used to simultaneously extract essential oils from the headspace. The single-drop of decane was suspended from the tip of a microsyringe and exposed to the headspace above the sample. After the extraction was finished, the single-drop was injected into gas chromatographic system and analyzed by GC-MS. The effects of the experimental parameters, including microwave power, microwave irradiation time, the ratio of carbonyl iron powder to sample, extraction solvent, single-drop volume and extraction time, were investigated. Sixteen compounds in the essential oils of E. caryophyllata T. were obtained and identified. The constituents of essential oils obtained by hydro-distillation and solvent-free microwave extraction-headspace single-drop microextraction were not obviously different. Compared with hydro-distillation, the proposed method required shorter extraction time and less amount of the sample.

  18. Homogeneous, Heterogeneous, and Enzymatic Catalysis.

    Science.gov (United States)

    Oyama, S. Ted; Somorjai, Gabor A.

    1988-01-01

    Discusses three areas of catalysis: homegeneous, heterogeneous, and enzymatic. Explains fundamentals and economic impact of catalysis. Lists and discusses common industrial catalysts. Provides a list of 107 references. (MVL)

  19. Catalysis for alternative energy generation

    CERN Document Server

    2012-01-01

    Summarizes recent problems in using catalysts in alternative energy generation and proposes novel solutions  Reconsiders the role of catalysis in alternative energy generation  Contributors include catalysis and alternative energy experts from across the globe

  20. Preface: Catalysis Today

    DEFF Research Database (Denmark)

    Li, Yongdan

    2016-01-01

    This special issue of Catalysis Today with the theme “Sustain-able Energy” results from a great success of the session “Catalytic Technologies Accelerating the Establishment of Sustainable and Clean Energy”, one of the two sessions of the 1st International Symposium on Catalytic Science and Techn......This special issue of Catalysis Today with the theme “Sustain-able Energy” results from a great success of the session “Catalytic Technologies Accelerating the Establishment of Sustainable and Clean Energy”, one of the two sessions of the 1st International Symposium on Catalytic Science...... and Technology in Sustainable Energy and Environment, held in Tianjin, China during October8–10, 2014. This biennial symposium offers an international forum for discussing and sharing the cutting-edge researches and the most recent breakthroughs in energy and environmental technologies based on catalysis...

  1. Catalysis seen in action.

    Science.gov (United States)

    Tromp, Moniek

    2015-03-06

    Synchrotron radiation techniques are widely applied in materials research and heterogeneous catalysis. In homogeneous catalysis, its use so far is rather limited despite its high potential. Here, insights in the strengths and limitations of X-ray spectroscopy technique in the field of homogeneous catalysis are given, including new technique developments. A relevant homogeneous catalyst, used in the industrially important selective oligomerization of ethene, is taken as a worked-out example. Emphasis is placed on time-resolved operando X-ray absorption spectroscopy with outlooks to novel high energy resolution and emission techniques. All experiments described have been or can be done at the Diamond Light Source Ltd (Didcot, UK). © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  2. Isotopes in heterogeneous catalysis

    CERN Document Server

    Hargreaves, Justin SJ

    2006-01-01

    The purpose of this book is to review the current, state-of-the-art application of isotopic methods to the field of heterogeneous catalysis. Isotopic studies are arguably the ultimate technique in in situ methods for heterogeneous catalysis. In this review volume, chapters have been contributed by experts in the field and the coverage includes both the application of specific isotopes - Deuterium, Tritium, Carbon-14, Sulfur-35 and Oxygen-18 - as well as isotopic techniques - determination of surface mobility, steady state transient isotope kinetic analysis, and positron emission profiling.

  3. Asymmetric synthesis II more methods and applications

    CERN Document Server

    Christmann, Mathias

    2012-01-01

    After the overwhelming success of 'Asymmetric Synthesis - The Essentials', narrating the colorful history of asymmetric synthesis, this is the second edition with latest subjects and authors. While the aim of the first edition was mainly to honor the achievements of the pioneers in asymmetric syntheses, the aim of this new edition was bringing the current developments, especially from younger colleagues, to the attention of students. The format of the book remained unchanged, i.e. short conceptual overviews by young leaders in their field including a short biography of the authors. The growing multidisciplinary research within chemistry is reflected in the selection of topics including metal catalysis, organocatalysis, physical organic chemistry, analytical chemistry, and its applications in total synthesis. The prospective reader of this book is a graduate or undergraduate student of advanced organic chemistry as well as the industrial chemist who wants to get a brief update on the current developments in th...

  4. Homogenous asymmetric hydrogenation: Recent trends and industrial applications.

    Science.gov (United States)

    Palmer, Andreas M; Zanotti-Gerosa, Antonio

    2010-01-01

    Recent advances in the field of homogeneous asymmetric hydrogenation are presented in this review. An analysis of academic literature published in the past 2 years highlights significant advances in the asymmetric hydrogenation of functional groups that previously were considered difficult to hydrogenate, as well as the emergence of novel concepts in catalysis, such as the use of non-traditional metals, phosphine-free catalysts and chiral counterions. An analysis of industry publications from 2009 and 2010 highlights more established applications of asymmetric hydrogenation reactions; these are discussed with a particular focus on practical aspects, such as catalyst selection, experimental conditions and the removal of metal residues.

  5. Palladium-Catalyzed Asymmetric Benzylic Substitution of Secondary Benzyl Carbonates with Nitrogen and Oxygen Nucleophiles.

    Science.gov (United States)

    Najib, Atifah; Hirano, Koji; Miura, Masahiro

    2017-05-05

    A Pd/(R)-BINAP-catalyzed asymmetric benzylic substitution of secondary benzyl carbonates with amides and amines proceeds to form the corresponding optically active benzylamines in good yields with a high enantiomeric ratio. The reaction occurs in a dynamic kinetic asymmetric transformation (DYKAT) manner. Additionally, the asymmetric Pd catalysis can also be applicable to phenol nucleophiles, thus delivering chiral ethers with acceptable yields and enantioselectivity.

  6. Catalysis for Sustainable Development

    Indian Academy of Sciences (India)

    Issue front cover thumbnail. Volume 126, Issue 2. March 2014, pages 309-532. Catalysis for Sustainable Development. pp 309-309. Foreword · M Lakshmi Kantam K S Rama Rao · More Details Fulltext PDF. pp 311-317. Concept and progress in coupling of dehydrogenation and hydrogenation reactions through catalysts.

  7. Pollution Control by Catalysis

    DEFF Research Database (Denmark)

    Eriksen, Kim Michael; Fehrmann, Rasmus

    1998-01-01

    The report summarises the results of two years of collaboration supported by INTAS between Department of Chemistry,DTU,DK , IUSTI,Universite de Provence,FR, ICE/HT University 6of Patras,GR, and Boreskov Institute of Catalysis,RU.The project has been concerned with mechanistic studies of deNOx and...

  8. Anion-π catalysis.

    Science.gov (United States)

    Zhao, Yingjie; Beuchat, César; Domoto, Yuya; Gajewy, Jadwiga; Wilson, Adam; Mareda, Jiri; Sakai, Naomi; Matile, Stefan

    2014-02-05

    The introduction of new noncovalent interactions to build functional systems is of fundamental importance. We here report experimental and theoretical evidence that anion-π interactions can contribute to catalysis. The Kemp elimination is used as a classical tool to discover conceptually innovative catalysts for reactions with anionic transition states. For anion-π catalysis, a carboxylate base and a solubilizer are covalently attached to the π-acidic surface of naphthalenediimides. On these π-acidic surfaces, transition-state stabilizations up to ΔΔGTS = 31.8 ± 0.4 kJ mol(-1) are found. This value corresponds to a transition-state recognition of KTS = 2.7 ± 0.5 μM and a catalytic proficiency of 3.8 × 10(5) M(-1). Significantly increasing transition-state stabilization with increasing π-acidity of the catalyst, observed for two separate series, demonstrates the existence of "anion-π catalysis." In sharp contrast, increasing π-acidity of the best naphthalenediimide catalysts does not influence the more than 12 000-times weaker substrate recognition (KM = 34.5 ± 1.6 μM). Together with the disappearance of Michaelis-Menten kinetics on the expanded π-surfaces of perylenediimides, this finding supports that contributions from π-π interactions are not very important for anion-π catalysis. The linker between the π-acidic surface and the carboxylate base strongly influences activity. Insufficient length and flexibility cause incompatibility with saturation kinetics. Moreover, preorganizing linkers do not improve catalysis much, suggesting that the ideal positioning of the carboxylate base on the π-acidic surface is achieved by intramolecular anion-π interactions rather than by an optimized structure of the linker. Computational simulations are in excellent agreement with experimental results. They confirm, inter alia, that the stabilization of the anionic transition states (but not the neutral ground states) increases with the π-acidity of the

  9. HNO3@nano SiO2: An efficient catalytic system for the synthesis of multi-substituted imidazoles under solvent-free conditions

    Directory of Open Access Journals (Sweden)

    Kobra Nikoofar

    2017-11-01

    Full Text Available Concentrated nitric acid supported on nano silica (HNO3@nano SiO2 has been prepared via a simple procedure. The synthetic powder has been utilized as an effective catalytic system for the synthesis of various 2,4,5-trisubstituted imidazoles under solvent-free conditions at 100 °C in good to excellent yields. In addition, under the same reaction conditions, 1,2,4,5-tetrasubstitued imidazoles have also been performed successfully. The recovery and reusability of HNO3@nano SiO2 have been checked in 3 runs without activity loss. The significant features of this acidic nanocatalyst in the reported procedure, are high yield of products, short reaction times, green reaction media, and vast range of substrates usage. The proposed mechanism of the cyclo-condensation has also been represented.

  10. Functionalized SBA-15 supported nickel (II)-oxime-imine catalysts for liquid phase oxidation of olefins under solvent-free conditions

    Science.gov (United States)

    Paul, Luna; Banerjee, Biplab; Bhaumik, Asim; Ali, Mahammad

    2016-05-01

    A new oxime-imine functionalized highly ordered mesoporous SBA-15 (SBA-15-NH2-DAMO) has been synthesized via post-synthesis functionalization of SBA-15 with 3-aminopropyl-triethoxysilane followed by the Schiff base condensation with diacetylmonooxime, which was further reacted with Ni(ClO4)2 to yield the functionalized nickel catalyst SBA-15-NH2-DAMO-Ni. All the synthesized materials were thoroughly characterized using different characterization techniques. It was found that SBA-15-NH2-DAMO-Ni catalyzes the one-pot oxidation of olefins like styrene, cyclohexene, cyclooctene, 1-hexene and 1-octene to the corresponding benzaldehyde, cyclohexene-1-ol and cyclooctene-oxide, respectively under solvent-free conditions by using tert-butylhydroperoxide as oxidant.

  11. Facile and rapid synthesis of divers xanthene derivatives using lanthanum(III chloride/chloroacetic acid as an efficient and reusable catalytic system under solvent-free conditions

    Directory of Open Access Journals (Sweden)

    Pouramiri Behjat

    2017-01-01

    Full Text Available LaCl3/ClCH2COOH was used as an efficient, and recyclable catalytic system for synthesis of 11H-benzo[a]xanthene-11-one, hexahydro-1H-xanthene- 1,8(2H-dione and 11-aryl-10H-diindeno[1,2-b:2′,1′-e]pyran-10,12(11H-dione derivatives via a one-pot three-component reaction of aldehydes, 2-naphthol, and cyclic 1,3-dicarbonyl compounds. The reactions proceeded rapidly at 70°C under solvent-free conditions and the desired products were obtained in good to excellent yields.

  12. Solvent-Free Biodiesel Production Catalyzed by Crude Lipase Powder from Seeds: Effects of Alcohol Polarity, Glycerol, and Thermodynamic Water Activity.

    Science.gov (United States)

    Kouteu, Paul Alain Nanssou; Blin, Joël; Baréa, Bruno; Barouh, Nathalie; Villeneuve, Pierre

    2017-10-04

    The aim of this work was to evaluate the potential of crude lipase powders made from Adansonia grandidieri and Jatropha mahafalensis seeds for the synthesis of fatty acid alkyl esters in a solvent-free system. The influence of the nature of the alcohol, the amount of glycerol, and hydration of the powder was investigated. Results showed that the activity of these crude lipase powders was inversely proportional to the alcohol polarity and the amount of the glycerol in the reaction medium. To ensure optimum activity, A. grandidieri and J. mahafalensis powders must be conditioned to a water activity of 0.33 and 0.66. To obtain a fatty acid ethyl ester yield greater than 95% with A. grandidieri, ethanol should be introduced at an amount corresponding to a triacylglycerol to ethanol molar ratio of 2:1 every 15 h for 96 h and use 25% of preconditioned crude lipase powders (2 additions of 12.5%).

  13. Solvent-free microwave extraction and hydrodistillation of essential oils from endemic Origanum husnucanbaseri H. Duman, Aytac & A. Duran: comparison of antibacterial activity and contents.

    Science.gov (United States)

    Uysal, Burcu; Sozmen, Fazli; Kose, Elif Odabas; Gokhan Deniz, I; Oksal, Birsen S

    2010-10-01

    The essential oils (EOs) obtained by solvent-free microwave extraction (SFME) and hydrodistillation (HD) from endemic Origanum husnucanbaseri H. Duman, Aytac & A. Duran were investigated using the gas chromatography-mass spectrometry system. The main constituents of both oils obtained from SFME and HD from O. husnucanbaseri are borneol (15.2-12.8%), α-terpineol (12.3-10.8%) and trans-sabinene hydrate (11.8-9.92%). The EO obtained from SFME contained substantially higher amounts of oxygenated compounds and lower amounts of monoterpenes than that from HD. The antibacterial activities of the EOs from SFME and HD were evaluated by the disc diffusion method against six bacterial strains. The EO extracted by SFME was more effective than the EO extracted by HD against the tested bacteria, except for Klebsiella pneumoniae American type culture collection (ATCC) 13883. Streptococcus pyogenes ATCC 19615 and Staphylococcus aureus ATCC 25923 in particular were more sensitive against the EO extracted by SFME.

  14. Solvent-free oxidation of secondary alcohols to carbonyl compounds by 1, 3-Dibromo-5, 5-Dimethylhydantoin (DBDMH) and 1, 3-Dichloro-5, 5-Dimethylhydantoin (DCDMH)

    Energy Technology Data Exchange (ETDEWEB)

    Khazaei, Ardeshir; Abbasi, Fatemeh, E-mail: Khazaei_1326@yahoo.com, E-mail: fatemehabbasi807@gmail.com [Faculty of Chemistry, Department of Organic Chemistry, Bu-Ali Sina University, Hamedan (Iran, Islamic Republic of); Kianiborazjani, Maryam [Faculty of Science, Department of Chemistry, Bushehr Payame Noor University (PNU), Bushehr (Iran, Islamic Republic of); Saednia, Shahnaz [Young Researchers Club, Toyserkan Branch, Islamic Azad University, Toyserkan (Iran, Islamic Republic of)

    2014-02-15

    Aldehydes and ketones are important intermediates, especially for the construction of carbon-skeletons. The oxidation of alcohols is so important that a large number of methods and reagents have been reported for this purpose. N-halo reagents are widely used in organic synthesis and as a continuation of our interest in the application of N-halo compounds in organic synthesis, dibromo dimethylhydantoin (DBDMH) and dichloro dimethylhydantoin (DCDMH) were used for the oxidation of alcohols and our ongoing work on development of highly efficient oxidation protocols. We observed the oxidation of secondary alcohols with stoichiometric amounts of DBDMH and DCDMH under solvent-free conditions in the range of temperature 70-80 deg C. (author)

  15. Sequential Dy(OTf)3-Catalyzed Solvent-Free Per-O-Acetylation and Regioselective Anomeric De-O-Acetylation of Carbohydrates.

    Science.gov (United States)

    Yan, Yi-Ling; Guo, Jiun-Rung; Liang, Chien-Fu

    2017-09-19

    Dysprosium(III) trifluoromethanesulfonate-catalyzed per-O-acetylation and regioselective anomeric de-O-acetylation of carbohydrates can be tuned by adjusting the reaction medium. In this study, the per-O-acetylation of unprotected sugars by using a near-stoichiometric amount of acetic anhydride under solvent-free conditions resulted in the exclusive formation of acetylated saccharides as anomeric mixtures, whereas anomeric de-O-acetylation in methanol resulted in a moderate-to-excellent yield. Reactions with various unprotected monosaccharides or disaccharides followed by a semi-one-pot sequential conversion into the corresponding acetylated glycosyl hemiacetal also resulted in high yields. Furthermore, the obtained hemiacetals could be successfully transformed into trichloroimidates after Dy(OTf) 3 -catalyzed glycosylation. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Highly Regio- and Stereoselective Diels-Alder Cycloadditions via Two-Step and Multicomponent Reactions Promoted by Infrared Irradiation under Solvent-Free Conditions

    Science.gov (United States)

    Flores-Conde, Maria Ines; Reyes, Leonor; Herrera, Rafael; Rios, Hulme; Vazquez, Miguel A.; Miranda, Rene; Tamariz, Joaquin; Delgado, Francisco

    2012-01-01

    Infrared irradiation promoted the Diels-Alder cycloadditions of exo-2-oxazolidinone dienes 1–3 with the Knoevenagel adducts 4–6, as dienophiles, leading to the synthesis of new 3,5-diphenyltetrahydrobenzo[d]oxazol-2-one derivatives (7, 9, 11 and 13–17), under solvent-free conditions. These cycloadditions were performed with good regio- and stereoselectivity, favoring the para-endo cycloadducts. We also evaluated the one-pot three-component reaction of active methylene compounds 20, benzaldehydes 21 and exo-2-oxazolidinone diene 2 under the same reaction conditions. A cascade Knoevenagel condensation/Diels-Alder cycloaddition reaction was observed, resulting in the final adducts 13–16 in similar yields. These procedures are environmentally benign, because no solvent and no catalyst were employed in these processes. The regioselectivity of these reactions was rationalized by Frontier Molecular Orbital (FMO) calculations. PMID:22489113

  17. Highly Regio- and Stereoselective Diels-Alder Cycloadditions via Two-Step and Multicomponent Reactions Promoted by Infrared Irradiation under Solvent-Free Conditions

    Directory of Open Access Journals (Sweden)

    Francisco Delgado

    2012-02-01

    Full Text Available Infrared irradiation promoted the Diels-Alder cycloadditions of exo-2-oxazolidinone dienes 1–3 with the Knoevenagel adducts 4–6, as dienophiles, leading to the synthesis of new 3,5-diphenyltetrahydrobenzo[d]oxazol-2-one derivatives (7, 9, 11 and 13–17, under solvent-free conditions. These cycloadditions were performed with good regio- and stereoselectivity, favoring the para-endo cycloadducts. We also evaluated the one-pot three-component reaction of active methylene compounds 20, benzaldehydes 21 and exo-2-oxazolidinone diene 2 under the same reaction conditions. A cascade Knoevenagel condensation/Diels-Alder cycloaddition reaction was observed, resulting in the final adducts 13–16 in similar yields. These procedures are environmentally benign, because no solvent and no catalyst were employed in these processes. The regioselectivity of these reactions was rationalized by Frontier Molecular Orbital (FMO calculations.

  18. Magnetic Catalysis in Graphene

    CERN Document Server

    Winterowd, Christopher; Zafeiropoulos, Savvas

    2015-01-01

    One of the most important developments in condensed matter physics in recent years has been the discovery and characterization of graphene. A two-dimensional layer of Carbon arranged in a hexagonal lattice, graphene exhibits many interesting electronic properties, most notably that the low energy excitations behave as massless Dirac fermions. These excitations interact strongly via the Coulomb interaction and thus non-perturbative methods are necessary. Using methods borrowed from lattice QCD, we study the graphene effective theory in the presence of an external magnetic field. Graphene, along with other $(2+1)$-dimensional field theories, has been predicted to undergo spontaneous breaking of flavor symmetry including the formation of a gap as a result of the external magnetic field. This phenomenon is known as magnetic catalysis. Our study investigates magnetic catalysis using a fully non-perturbative approach.

  19. Catalysis and biocatalysis program

    Science.gov (United States)

    Ingham, J. D.

    1993-01-01

    This final report presents a summary of research activities and accomplishments for the Catalysis and Biocatalysis Program, which was renamed the Biological and Chemical Technologies Research (BCTR) Program, currently of the Advanced Industrial Concepts Division (AICD), Office of Industrial Technologies of the Department of Energy (DOE). The Program was formerly under the Division of Energy Conversion and Utilization Technologies (ECUT) until the DOE reorganization in April, 1990. The goals of the BCTR Program are consistent with the initial ECUT goals, but represent an increased effort toward advances in chemical and biological technology transfer. In addition, the transition reflects a need for the BCTR Program to assume a greater R&D role in chemical catalysis as well as a need to position itself for a more encompassing involvement in a broader range of biological and chemical technology research. The mission of the AICD is to create a balanced Program of high risk, long-term, directed interdisciplinary research and development that will improve energy efficiency and enhance fuel flexibility in the industrial sector. Under AICD, the DOE Catalysis and Biocatalysis Program sponsors research and development in furthering industrial biotechnology applications and promotes the integrated participation of universities, industrial companies, and government research laboratories.

  20. Low Viscosity Imides Based on Asymmetric Oxydiphthalic Anhydride

    Science.gov (United States)

    Chuang, Kathy C.; Criss, Jim M., Jr.; Mintz, Eric A.; Scheiman, Daniel A.; Nguyen, Baochau N.; McCorkle, Linda S.

    2008-01-01

    A series of low-melt viscosity imide resins were prepared from asymmetric oxydiphthalic dianhydride (a-ODPA) and 4-phenylethynylphthalic anhydride as the endcap, along with 3,4' - oxydianiline (3,4' -ODA), 3,4' -methylenedianiline (3,4' -MDA), 3,3' -methylenedianiline (3,3' - MDA) and 3,3'-diaminobenzophenone (3,3'-DABP), using a solvent-free melt process. These imide oligomers displays low-melt viscosities (2-15 poise) at 260-280 C, which made them amenable to low-cost resin transfer molding (RTM) process. The a-ODPA based RTM resins exhibits glass transition temperatures (Tg's) in the range of 265-330 C after postcure at 343 C. The mechanical properties of these polyimide/carbon fiber composites fabricated by RTM will be discussed.

  1. Bis-phosphine allene ligand: coordination chemistry and preliminary applications in catalysis.

    Science.gov (United States)

    Vanitcha, Avassaya; Damelincourt, Cecilia; Gontard, Geoffrey; Vanthuyne, Nicolas; Mouriès-Mansuy, Virginie; Fensterbank, Louis

    2016-05-21

    A 1,3-bis-diphenylphosphine allene can give rise to new coordination complexes with palladium, platinum and gold metals. These complexes were fully characterized by NMR, HRMS and X-ray diffraction analysis. For gold(i), the corresponding dinuclear complex has been used in a series of diagnostic catalytic reactions and gave promising preliminary results in asymmetric catalysis.

  2. Enantioselective Decarboxylative Arylation of α-Amino Acids via the Merger of Photoredox and Nickel Catalysis

    Science.gov (United States)

    Zuo, Zhiwei; Cong, Huan; Li, Wei; Choi, Junwon; Fu, Gregory C.; MacMillan, David W. C.

    2016-01-01

    An asymmetric decarboxylative Csp3–Csp2 cross-coupling has been achieved via the synergistic merger of photoredox and nickel catalysis. This mild, operationally simple protocol transforms a wide variety of naturally abundant α-amino acids and readily available aryl halides into valuable chiral benzylic amines in high enantiomeric excess, thereby producing motifs found in pharmacologically active agents. PMID:26849354

  3. Microwave-assisted solvent-free synthesis of 14-aryl/alkyl-14H-dibenzo[a,j]xanthenes and tetrahydrobenzo[a]xanthen-11-ones catalyzed by nano silica phosphoric acid

    Directory of Open Access Journals (Sweden)

    Abdolhamid Bamoniri

    2013-01-01

    Full Text Available Nano silica phosphoric acid (nano SPA was applied as a catalyst for synthesis of 14-aryl/alkyl-14H-dibenzo[a,j]xanthenes and tetrahydrobenzo[a]xanthen-11-ones in microwave oven under solvent free conditions. High efficiency, easy availability and reusability are some advantages of this catalyst.

  4. Radical-Induced Metal and Solvent-Free Cross-Coupling Using TBAI-TBHP: Oxidative Amidation of Aldehydes and Alcohols with N-Chloramines via C-H Activation.

    Science.gov (United States)

    Achar, Tapas Kumar; Mal, Prasenjit

    2015-01-02

    A solvent-free cross-coupling method for oxidative amidation of aldehydes and alcohols via a metal-free radial pathway has been demonstrated. The proposed methodology uses the TBAI-TBHP combination which efficiently induces metal-free C-H activation of aldehydes under neat conditions at 50 °C or ball-milling conditions at room temperature.

  5. Mesoporous molecular sieve MCM-41 catalyzed one-pot synthesis of 3,4-dihydro-2(1H-pyrimidinones and –thiones under solvent-free conditions

    Directory of Open Access Journals (Sweden)

    Rahim Hekmatshoar

    2011-08-01

    Full Text Available An efficient synthesis of 3,4-dihydro-2(1H-pyrimidinones and -thiones using MCM-41 as the catalyst from an aldehyde, β-keto ester, and urea or thiourea under solvent-free conditions is described.

  6. Zeolite catalysis: technology

    Energy Technology Data Exchange (ETDEWEB)

    Heinemann, H.

    1980-07-01

    Zeolites have been used as catalysts in industry since the early nineteen sixties. The great majority of commercial applications employ one of three zeolite types: zeolite Y; Mordenite; ZSM-5. By far the largest use of zeolites is in catalytic cracking, and to a lesser extent in hydrocracking. This paper reviews the rapid development of zeolite catalysis and its application in industries such as: the production of gasoline by catalytic cracking of petroleum; isomerization of C/sub 5/ and C/sub 6/ paraffin hydrocarbons; alkylation of aromatics with olefins; xylene isomerization; and conversion of methanol to gasoline.

  7. Preparation of a Nanoemulsion with Carapa guianensis Aublet (Meliaceae Oil by a Low-Energy/Solvent-Free Method and Evaluation of Its Preliminary Residual Larvicidal Activity

    Directory of Open Access Journals (Sweden)

    Flávia L. M. Jesus

    2017-01-01

    Full Text Available Andiroba (Carapa guianensis seeds are the source of an oil with a wide range of biological activities and ethnopharmacological uses. However, few studies have devoted attention to innovative formulations, including nanoemulsions. The present study aimed to obtain a colloidal system with the andiroba oil using a low-energy and organic-solvent-free method. Moreover, the preliminary residual larvicidal activity of the nanoemulsion against Aedes aegypti was evaluated. Oleic and palmitic acids were the major fatty acids, in addition to the phytosterol β-sitosterol and limonoids (tetranortriterpenoids. The required hydrophile-lipophile was around 11.0 and the optimal nanoemulsion was obtained using polysorbate 85. The particle size distribution suggested the presence of small droplets (mean diameter around 150 nm and low polydispersity index (around 0.150. The effect of temperature on particle size distribution revealed that no major droplet size increase occurred. The preliminary residual larvicidal assay suggested that the mortality increased as a function of time. The present study allowed achievement of a potential bioactive oil in water nanoemulsion that may be a promising controlled release system. Moreover, the ecofriendly approach involved in the preparation associated with the great bioactive potential of C. guianensis makes this nanoemulsion very promising for valorization of this Amazon raw material.

  8. Mechanically stable solvent-free lipid bilayers in nano- and micro-tapered apertures for reconstitution of cell-free synthesized hERG channels.

    Science.gov (United States)

    Tadaki, Daisuke; Yamaura, Daichi; Araki, Shun; Yoshida, Miyu; Arata, Kohei; Ohori, Takeshi; Ishibashi, Ken-Ichi; Kato, Miki; Ma, Teng; Miyata, Ryusuke; Tozawa, Yuzuru; Yamamoto, Hideaki; Niwano, Michio; Hirano-Iwata, Ayumi

    2017-12-18

    The self-assembled bilayer lipid membrane (BLM) is the basic component of the cell membrane. The reconstitution of ion channel proteins in artificially formed BLMs represents a well-defined system for the functional analysis of ion channels and screening the effects of drugs that act on them. However, because BLMs are unstable, this limits the experimental throughput of BLM reconstitution systems. Here we report on the formation of mechanically stable solvent-free BLMs in microfabricated apertures with defined nano- and micro-tapered edge structures. The role of such nano- and micro-tapered structures on the stability of the BLMs was also investigated. Finally, this BLM system was combined with a cell-free synthesized human ether-a-go-go-related gene channel, a cardiac potassium channel whose relation to arrhythmic side effects following drug treatment is well recognized. Such stable BLMs as these, when combined with a cell-free system, represent a potential platform for screening the effects of drugs that act on various ion-channel genotypes.

  9. Attenuation of Multiple Organ Damage by Continuous Low-Dose Solvent-Free Infusions of Resveratrol after Severe Hemorrhagic Shock in Rats

    Science.gov (United States)

    Kirsch, Michael; Petrat, Frank

    2017-01-01

    Therapeutic effects of continuous intravenous infusions of solvent-free low doses of resveratrol on organ injury and systemic consequences resulting from severe hemorrhagic shock in rats were studied. Hemorrhagic shock was induced by withdrawing arterial blood until a mean arterial blood pressure (MAP) of 25–30 mmHg was reached. Following a shock phase of 60 min, rats were resuscitated with the withdrawn blood plus lactated Ringer’s. Resveratrol (20 or 60 μg/kg × h) was continuously infused intravenously starting with the resuscitation phase (30 min) and continued until the end of the experiment (total treatment time 180 min). Animals of the shock control group received 0.9% NaCl solution. After the observation phase (150 min), rats were sacrificed. Resveratrol significantly stabilized the MAP and peripheral oxygen saturation after hemorrhagic shock, decreased the macroscopic injury of the small intestine, significantly attenuated the shock-induced increase in tissue myeloperoxidase activity in the small intestine, liver, kidney and lung, and diminished tissue hemorrhages (particularly in the small intestine and liver) as well as the rate of hemolysis. Already very low doses of resveratrol, continuously infused during resuscitation after severe hemorrhagic shock, can significantly improve impaired systemic parameters and attenuate multiple organ damage in rats. PMID:28817064

  10. Immobilization of Pseudomonas fluorescens lipase on hydrophobic supports and application in biodiesel synthesis by transesterification of vegetable oils in solvent-free systems.

    Science.gov (United States)

    Lima, Lionete N; Oliveira, Gladson C; Rojas, Mayerlenis J; Castro, Heizir F; Da Rós, Patrícia C M; Mendes, Adriano A; Giordano, Raquel L C; Tardioli, Paulo W

    2015-04-01

    This work describes the preparation of biocatalysts for ethanolysis of soybean and babassu oils in solvent-free systems. Polystyrene, Amberlite (XAD-7HP), and octyl-silica were tested as supports for the immobilization of Pseudomonas fluorescens lipase (PFL). The use of octyl-silica resulted in a biocatalyst with high values of hydrolytic activity (650.0 ± 15.5 IU/g), immobilization yield (91.3 ± 0.3 %), and recovered activity (82.1 ± 1.5 %). PFL immobilized on octyl-silica was around 12-fold more stable than soluble PFL, at 45 °C and pH 8.0, in the presence of ethanol at 36 % (v/v). The biocatalyst provided high vegetable oil transesterification yields of around 97.5 % after 24 h of reaction using babassu oil and around 80 % after 48 h of reaction using soybean oil. The PFL-octyl-silica biocatalyst retained around 90 % of its initial activity after five cycles of transesterification of soybean oil. Octyl-silica is a promising support that can be used to immobilize PFL for subsequent application in biodiesel synthesis.

  11. Performance of an enzymatic packed bed reactor running on babassu oil to yield fatty ethyl esters (FAEE in a solvent-free system

    Directory of Open Access Journals (Sweden)

    Aline Simões

    2015-06-01

    Full Text Available The transesterification reaction of babassu oil with ethanol mediated by Burkholderia cepacia lipase immobilized on SiO2-PVA composite was assessed in a packed bed reactor running in the continuous mode. Experiments were performed in a solvent-free system at 50 °C. The performance of the reactor (14 mm ×210 mm was evaluated using babassu oil and ethanol at two molar ratios of 1:7 and 1:12, respectively, and operational limits in terms of substrate flow rate were determined. The system’s performance was quantified for different flow rates corresponding to space times between 7 and 13 h. Under each condition, the impact of the space time on the ethyl esters formation, the transesterification yield and productivity were determined. The oil to ethanol molar ratio was found as a critical parameter in the conversion of babassu oil into the correspondent ethyl esters. The highest transesterification yield of 96.0 ± 0.9% and productivity of 41.1 ± 1.6 mgester gcatalyst-1h-1 were achieved at the oil to ethanol molar ratio of 1:12 and for space times equal or higher than 11 h. Moreover, the immobilized lipase was found stable with respect to its catalytic characteristics, exhibiting a half-life of 32 d.

  12. Comparative Study of Essential Oils Extracted from Egyptian Basil Leaves (Ocimum basilicum L.) Using Hydro-Distillation and Solvent-Free Microwave Extraction.

    Science.gov (United States)

    Chenni, Mohammed; El Abed, Douniazad; Rakotomanomana, Njara; Fernandez, Xavier; Chemat, Farid

    2016-01-19

    Solvent-free microwave extraction (SFME) and conventional hydro-distillation (HD) were used for the extraction of essential oils (EOs) from Egyptian sweet basil (Ocimum basilicum L.) leaves. The two resulting EOs were compared with regards to their chemical composition, antioxidant, and antimicrobial activities. The EO analyzed by GC and GC-MS, presented 65 compounds constituting 99.3% and 99.0% of the total oils obtained by SFME and HD, respectively. The main components of both oils were linalool (43.5% SFME; 48.4% HD), followed by methyl chavicol (13.3% SFME; 14.3% HD) and 1,8-cineole (6.8% SFME; 7.3% HD). Their antioxidant activity were studied with the 2,2-diphenyl-1-picrylhydrazyl (DPPH(•)) radical scavenging method. The heating conditions effect was evaluated by the determination of the Total Polar Materials (TPM) content. The antimicrobial activity was investigated against five microorganisms: two Gram-positive bacteria, Staphylococcus aureus and Bacillus subtilis, two Gram-negative bacteria, Escherichia coli and Pseudomonas aeruginosa, and one yeast, Candida albicans. Both EOs showed high antimicrobial, but weak antioxidant, activities. The results indicated that the SFME method may be a better alternative for the extraction of EO from O. basilicum since it could be considered as providing a richer source of natural antioxidants, as well as strong antimicrobial agents for food preservation.

  13. Antibacterial activities of essential oils extracted from leaves of Murraya koenigii by solvent-free microwave extraction and hydro-distillation.

    Science.gov (United States)

    Erkan, Naciye; Tao, Zhou; Rupasinghe, H P Vasantha; Uysal, Burcu; Oksal, Birsen S

    2012-01-01

    Solvent-free microwave extraction (SFME) for the isolation of essential oil from leaves of Murraya koenigii L. (Rutaceae) has been compared with the conventional hydro-distilled oil (HD) in terms of yield, composition, antioxidant activity, and antibacterial activity against Listeria innocua. The yield of essential oil obtained from 30 min of SFME was similar to that of HD for 180 min. By GC-MS analysis, the major compounds of the essential oil extracted by SFME, which were obtained in somewhat lower amounts than in the essential oil obtained by HD, were alpha-copaene (44.3%), beta-gurjunene (25.5%), isocaryophyllene (12.1%), beta-caryophyllene (8.7%) and germacrene D (2.9%). The content of oxygenated terpenes, slightly higher for the SFME-essential oil (2.3%) than the HD-essential oil (1.4%), were much lower than that of nonoxygenated terpenes in both oils. DPPH radical scavenging activities of both essential oils were relatively low (10%-24%). Complete inhibition of growth of L. innocua was observed with both SFME and HD essential oils, at 400 and 600 microg/mL (minimum inhibitory concentration), respectively. The SFME-essential oil at 300 microg/mL provided 92% inhibition, indicating its potential as a natural antimicrobial agent.

  14. Sustained Release of Lidocaine from Solvent-Free Biodegradable Poly[(d,l-Lactide-co-Glycolide] (PLGA: In Vitro and In Vivo Study

    Directory of Open Access Journals (Sweden)

    Yi-Chuan Kau

    2014-09-01

    Full Text Available Local anesthetics are commonly used for pain relief by regional nerve blocking. In this study, we fabricated solvent-free biodegradable pellets to extend the duration of lidocaine release without any significant local or systemic toxicity levels. To manufacture the pellets, poly[(d,l-lactide-co-glycolide] (PLGA was first pre-mixed with lidocaine powder into different ratios. The powder mixture was then compressed with a mold (diameter of 1, 5, 8 or 10 mm and sintered at 65 °C to form pellets. The in vitro release study showed that the lidocaine/PLGA pellets exhibited a tri-phase release behavior (a burst, a diffusion-controlled release and a degradation-dominated release and reached completion around day 28. Scanning electron microscope (SEM photos show that small channels could be found on the surfaces of the pellets on day 2. Furthermore, the polymer matrix swelled and fell apart on day 7, while the pellets became viscous after 10 days of in vitro elution. Perineural administration of the lidocaine/PLGA pellets produced anti-hypersensitivity effects lasting for at least 24 h in rats, significant when compared to the control group (a pure PLGA was pellet administered. In addition, no inflammation was detected within the nerve and in the neighboring muscle by histopathology.

  15. Optimization of the production of biodiesel by a commercial immobilized lipase in a solvent-free system using a response surface methodology

    Directory of Open Access Journals (Sweden)

    ZORICA KNEZEVIC

    2008-02-01

    Full Text Available Response surface methodology was used for the evaluation of the effects of various factors on the synthesis of biodiesel catalyzed with immobilized lipase from Rhizomucor miehei in a solvent-free system. The production of biodiesel was optimized and model response equations were obtained, enabling the prediction of biodiesel production from the values of the four main factors. It would seem that the reaction temperature and the amount of water predominantly determined the conversion process while the methanol/oil molar ratio had no significant influence on the reaction rate. The temperature and amount of water showed negative interactive effects on the observed reaction rate per amount of enzyme. However, there were no significant interactions among the other variables according to the test of statistical significance. The highest yield of 10.15 mol kg-1 enzyme was observed at 45 °C with a 6:1 methanol to oil molar ratio and with no added water in the system.

  16. Solvent-free microwave-assisted synthesis of novel pyrazolo[4′,3′:5,6]pyrido[2,3-d]pyrimidines with potential antifungal activity

    Directory of Open Access Journals (Sweden)

    Paola Acosta

    2016-05-01

    Full Text Available Novel fused pyrazolo[4′,3′:5,6]pyrido[2,3-d]pyrimidines 5 were prepared by a solvent-free microwave assisted reaction of heterocyclic o-aminonitriles 3 and cyanopyridines 4 in the presence of tBuOK as catalyst. This protocol provides a versatile procedure for the synthesis of the title compounds with the advantages of easy work-up, mild reaction conditions and good yields. All compounds were also tested for antifungal properties against two clinically important fungi; Candida albicans and Cryptococcus neoformans. Several compounds showed moderate activity against both fungi, being 5a the most active compound. Analysis of the antifungal behavior of properly grouped compounds allowed to determine that the position of the N in the pyrimidyl moiety per se does not play a role in the activity. In turn, the type of 4-R substituent appears to influence the activity. In addition to the above considerations, the lipophilicity of compounds measured as logP showed to be not related to the activity and regarding the dipole moment (D, no net correlation was observed, although it is the most active compounds (% inhibition >50% that have a D ⩾ 7.5, mainly against C. albicans.

  17. Microfluidic White Organic Light-Emitting Diode Based on Integrated Patterns of Greenish-Blue and Yellow Solvent-Free Liquid Emitters

    Science.gov (United States)

    Kobayashi, Naofumi; Kasahara, Takashi; Edura, Tomohiko; Oshima, Juro; Ishimatsu, Ryoichi; Tsuwaki, Miho; Imato, Toshihiko; Shoji, Shuichi; Mizuno, Jun

    2015-01-01

    We demonstrated a novel microfluidic white organic light-emitting diode (microfluidic WOLED) based on integrated sub-100-μm-wide microchannels. Single-μm-thick SU-8-based microchannels, which were sandwiched between indium tin oxide (ITO) anode and cathode pairs, were fabricated by photolithography and heterogeneous bonding technologies. 1-Pyrenebutyric acid 2-ethylhexyl ester (PLQ) was used as a solvent-free greenish-blue liquid emitter, while 2,8-di-tert-butyl-5,11-bis(4-tert-butylphenyl)-6,12-diphenyltetracene (TBRb)-doped PLQ was applied as a yellow liquid emitter. In order to form the liquid white light-emitting layer, the greenish-blue and yellow liquid emitters were alternately injected into the integrated microchannels. The fabricated electro-microfluidic device successfully exhibited white electroluminescence (EL) emission via simultaneous greenish-blue and yellow emissions under an applied voltage of 100 V. A white emission with Commission Internationale de l’Declairage (CIE) color coordinates of (0.40, 0.42) was also obtained; the emission corresponds to warm-white light. The proposed device has potential applications in subpixels of liquid-based microdisplays and for lighting. PMID:26439164

  18. Preparation of a Nanoemulsion with Carapa guianensis Aublet (Meliaceae) Oil by a Low-Energy/Solvent-Free Method and Evaluation of Its Preliminary Residual Larvicidal Activity

    Science.gov (United States)

    Jesus, Flávia L. M.; de Almeida, Fernanda B.; Duarte, Jonatas L.; Oliveira, Anna E. M. F. M.; Cruz, Rodrigo A. S.; Souto, Raimundo N. P.; Ferreira, Ricardo M. A.; Kelmann, Regina Gendzelevski; Solans, Conxita

    2017-01-01

    Andiroba (Carapa guianensis) seeds are the source of an oil with a wide range of biological activities and ethnopharmacological uses. However, few studies have devoted attention to innovative formulations, including nanoemulsions. The present study aimed to obtain a colloidal system with the andiroba oil using a low-energy and organic-solvent-free method. Moreover, the preliminary residual larvicidal activity of the nanoemulsion against Aedes aegypti was evaluated. Oleic and palmitic acids were the major fatty acids, in addition to the phytosterol β-sitosterol and limonoids (tetranortriterpenoids). The required hydrophile-lipophile was around 11.0 and the optimal nanoemulsion was obtained using polysorbate 85. The particle size distribution suggested the presence of small droplets (mean diameter around 150 nm) and low polydispersity index (around 0.150). The effect of temperature on particle size distribution revealed that no major droplet size increase occurred. The preliminary residual larvicidal assay suggested that the mortality increased as a function of time. The present study allowed achievement of a potential bioactive oil in water nanoemulsion that may be a promising controlled release system. Moreover, the ecofriendly approach involved in the preparation associated with the great bioactive potential of C. guianensis makes this nanoemulsion very promising for valorization of this Amazon raw material. PMID:28798803

  19. Magnetic amine-functionalized graphene oxide as a novel and recyclable bifunctional nanocatalyst for solvent-free synthesis of pyrano[3,2-c]pyridine derivatives

    Directory of Open Access Journals (Sweden)

    Shahnaz Rostamizadeh

    2017-01-01

    Full Text Available The new magnetic amine-functionalized graphene oxide (Fe3O4-GO-NH2 nanocatalyst was prepared through the reaction of 3-aminopropyltriethoxysilane (APTES with magnetic graphene oxide (Fe3O4-GO. It was characterized by XRD, TEM, SEM, FT-IR and EDX techniques. The intrinsic carboxylic acids on the edges of Fe3O4-GO along with the amine groups post grafted to the surface of Fe3O4-GO led to preparation of an acid-base bifunctional magnetically recyclable nanocatalyst. It proved to be efficient nanocatalyst for solvent-free synthesis of pyrano[3,2-c]pyridine derivatives under mild reaction conditions with good to excellent yields. This heterogeneous catalyst also exhibited higher activities than acid or base functionalized mesoporous silica, magnetic GO or basic Al2O3 an even higher than some basic homogeneous catalysts such as triethylamine and piperazine. More importantly, due to the loaded iron oxide nanoparticles, this catalyst could be easily recovered from the reaction mixture using an external magnet and reused without significant decrease in activity even after 7 runs.

  20. Advances in Catalysis by Heteropolyacids

    Science.gov (United States)

    Kozhevnikov, I. V.

    1987-09-01

    The advances in acid catalysis by heteropolyacids are examined and data on the acidity of heteropolyacids are surveyed. The characteristics of homogeneous and heterogeneous acid catalysis by heteropolyacids are discussed and its applied aspects are noted. The bibliography includes 116 references.

  1. Catalysis and prebiotic RNA synthesis

    Science.gov (United States)

    Ferris, James P.

    1993-01-01

    The essential role of catalysis for the origins of life is discussed. The status of the prebiotic synthesis of 2',5'- and 3'5'-linked oligomers of RNA is reviewed. Examples of the role of metal ion and mineral catalysis in RNA oligomer formation are discussed.

  2. Heterogeneous Catalysis of Polyoxometalate Based Organic–Inorganic Hybrids

    Science.gov (United States)

    Ren, Yuanhang; Wang, Meiyin; Chen, Xueying; Yue, Bin; He, Heyong

    2015-01-01

    Organic–inorganic hybrid polyoxometalate (POM) compounds are a subset of materials with unique structures and physical/chemical properties. The combination of metal-organic coordination complexes with classical POMs not only provides a powerful way to gain multifarious new compounds but also affords a new method to modify and functionalize POMs. In parallel with the many reports on the synthesis and structure of new hybrid POM compounds, the application of these compounds for heterogeneous catalysis has also attracted considerable attention. The hybrid POM compounds show noteworthy catalytic performance in acid, oxidation, and even in asymmetric catalytic reactions. This review summarizes the design and synthesis of organic–inorganic hybrid POM compounds and particularly highlights their recent progress in heterogeneous catalysis. PMID:28788017

  3. Heterogeneous Catalysis of Polyoxometalate Based Organic–Inorganic Hybrids

    Directory of Open Access Journals (Sweden)

    Yuanhang Ren

    2015-03-01

    Full Text Available Organic–inorganic hybrid polyoxometalate (POM compounds are a subset of materials with unique structures and physical/chemical properties. The combination of metal-organic coordination complexes with classical POMs not only provides a powerful way to gain multifarious new compounds but also affords a new method to modify and functionalize POMs. In parallel with the many reports on the synthesis and structure of new hybrid POM compounds, the application of these compounds for heterogeneous catalysis has also attracted considerable attention. The hybrid POM compounds show noteworthy catalytic performance in acid, oxidation, and even in asymmetric catalytic reactions. This review summarizes the design and synthesis of organic–inorganic hybrid POM compounds and particularly highlights their recent progress in heterogeneous catalysis.

  4. Heterogeneous Catalysis of Polyoxometalate Based Organic-Inorganic Hybrids.

    Science.gov (United States)

    Ren, Yuanhang; Wang, Meiyin; Chen, Xueying; Yue, Bin; He, Heyong

    2015-03-31

    Organic-inorganic hybrid polyoxometalate (POM) compounds are a subset of materials with unique structures and physical/chemical properties. The combination of metal-organic coordination complexes with classical POMs not only provides a powerful way to gain multifarious new compounds but also affords a new method to modify and functionalize POMs. In parallel with the many reports on the synthesis and structure of new hybrid POM compounds, the application of these compounds for heterogeneous catalysis has also attracted considerable attention. The hybrid POM compounds show noteworthy catalytic performance in acid, oxidation, and even in asymmetric catalytic reactions. This review summarizes the design and synthesis of organic-inorganic hybrid POM compounds and particularly highlights their recent progress in heterogeneous catalysis.

  5. Asymmetric Ashes

    Science.gov (United States)

    2006-11-01

    that oscillate in certain directions. Reflection or scattering of light favours certain orientations of the electric and magnetic fields over others. This is why polarising sunglasses can filter out the glint of sunlight reflected off a pond. When light scatters through the expanding debris of a supernova, it retains information about the orientation of the scattering layers. If the supernova is spherically symmetric, all orientations will be present equally and will average out, so there will be no net polarisation. If, however, the gas shell is not round, a slight net polarisation will be imprinted on the light. This is what broad-band polarimetry can accomplish. If additional spectral information is available ('spectro-polarimetry'), one can determine whether the asymmetry is in the continuum light or in some spectral lines. In the case of the Type Ia supernovae, the astronomers found that the continuum polarisation is very small so that the overall shape of the explosion is crudely spherical. But the much larger polarization in strongly blue-shifted spectral lines evidences the presence, in the outer regions, of fast moving clumps with peculiar chemical composition. "Our study reveals that explosions of Type Ia supernovae are really three-dimensional phenomena," says Dietrich Baade. "The outer regions of the blast cloud is asymmetric, with different materials found in 'clumps', while the inner regions are smooth." "This study was possible because polarimetry could unfold its full strength thanks to the light-collecting power of the Very Large Telescope and the very precise calibration of the FORS instrument," he adds. The research team first spotted this asymmetry in 2003, as part of the same observational campaign (ESO PR 23/03 and ESO PR Photo 26/05). The new, more extensive results show that the degree of polarisation and, hence, the asphericity, correlates with the intrinsic brightness of the explosion. The brighter the supernova, the smoother, or less clumpy

  6. Optimisation and Characterisation of Lipase-Catalysed Synthesis of a Kojic Monooleate Ester in a Solvent-Free System by Response Surface Methodology.

    Science.gov (United States)

    Jumbri, Khairulazhar; Al-Haniff Rozy, Mohd Fahruddin; Ashari, Siti Efliza; Mohamad, Rosfarizan; Basri, Mahiran; Fard Masoumi, Hamid Reza

    2015-01-01

    Kojic acid is widely used to inhibit the browning effect of tyrosinase in cosmetic and food industries. In this work, synthesis of kojic monooleate ester (KMO) was carried out using lipase-catalysed esterification of kojic acid and oleic acid in a solvent-free system. Response Surface Methodology (RSM) based on central composite rotatable design (CCRD) was used to optimise the main important reaction variables, such as enzyme amount, reaction temperature, substrate molar ratio, and reaction time along with immobilised lipase from Candida Antarctica (Novozym 435) as a biocatalyst. The RSM data indicated that the reaction temperature was less significant in comparison to other factors for the production of a KMO ester. By using this statistical analysis, a quadratic model was developed in order to correlate the preparation variable to the response (reaction yield). The optimum conditions for the enzymatic synthesis of KMO were as follows: an enzyme amount of 2.0 wt%, reaction temperature of 83.69°C, substrate molar ratio of 1:2.37 (mmole kojic acid:oleic acid) and a reaction time of 300.0 min. Under these conditions, the actual yield percentage obtained was 42.09%, which is comparably well with the maximum predicted value of 44.46%. Under the optimal conditions, Novozym 435 could be reused for 5 cycles for KMO production percentage yield of at least 40%. The results demonstrated that statistical analysis using RSM can be used efficiently to optimise the production of a KMO ester. Moreover, the optimum conditions obtained can be applied to scale-up the process and minimise the cost.

  7. Optimisation and Characterisation of Lipase-Catalysed Synthesis of a Kojic Monooleate Ester in a Solvent-Free System by Response Surface Methodology.

    Directory of Open Access Journals (Sweden)

    Khairulazhar Jumbri

    Full Text Available Kojic acid is widely used to inhibit the browning effect of tyrosinase in cosmetic and food industries. In this work, synthesis of kojic monooleate ester (KMO was carried out using lipase-catalysed esterification of kojic acid and oleic acid in a solvent-free system. Response Surface Methodology (RSM based on central composite rotatable design (CCRD was used to optimise the main important reaction variables, such as enzyme amount, reaction temperature, substrate molar ratio, and reaction time along with immobilised lipase from Candida Antarctica (Novozym 435 as a biocatalyst. The RSM data indicated that the reaction temperature was less significant in comparison to other factors for the production of a KMO ester. By using this statistical analysis, a quadratic model was developed in order to correlate the preparation variable to the response (reaction yield. The optimum conditions for the enzymatic synthesis of KMO were as follows: an enzyme amount of 2.0 wt%, reaction temperature of 83.69°C, substrate molar ratio of 1:2.37 (mmole kojic acid:oleic acid and a reaction time of 300.0 min. Under these conditions, the actual yield percentage obtained was 42.09%, which is comparably well with the maximum predicted value of 44.46%. Under the optimal conditions, Novozym 435 could be reused for 5 cycles for KMO production percentage yield of at least 40%. The results demonstrated that statistical analysis using RSM can be used efficiently to optimise the production of a KMO ester. Moreover, the optimum conditions obtained can be applied to scale-up the process and minimise the cost.

  8. Solvent-Free Synthesis of Uniform MOF Shell-Derived Carbon Confined SnO2/Co Nanocubes for Highly Reversible Lithium Storage.

    Science.gov (United States)

    He, Qiu; Liu, Jinshuai; Li, Zhaohuai; Li, Qi; Xu, Lin; Zhang, Baoxuan; Meng, Jiashen; Wu, Yuzhu; Mai, Liqiang

    2017-10-01

    Tin dioxide (SnO 2 ) has attracted much attention in lithium-ion batteries (LIBs) due to its abundant source, low cost, and high theoretical capacity. However, the large volume variation, irreversible conversion reaction limit its further practical application in next-generation LIBs. Here, a novel solvent-free approach to construct uniform metal-organic framework (MOF) shell-derived carbon confined SnO 2 /Co (SnO 2 /Co@C) nanocubes via a two-step heat treatment is developed. In particular, MOF-coated CoSnO 3 hollow nanocubes are for the first time synthesized as the intermediate product by an extremely simple thermal solid-phase reaction, which is further developed as a general strategy to successfully obtain other uniform MOF-coated metal oxides. The as-synthesized SnO 2 /Co@C nanocubes, when tested as LIB anodes, exhibit a highly reversible discharge capacity of 800 mAh g -1 after 100 cycles at 200 mA g -1 and excellent cycling stability with a retained capacity of 400 mAh g -1 after 1800 cycles at 5 A g -1 . The experimental analyses demonstrate that these excellent performances are mainly ascribed to the delicate structure and a synergistic effect between Co and SnO 2 . This facile synthetic approach will greatly contribute to the development of functional metal oxide-based and MOF-assisted nanostructures in many frontier applications. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Utilization of dynamic light scattering to evaluate Pterodon emarginatus oleoresin-based nanoemulsion formation by non-heating and solvent-free method

    Directory of Open Access Journals (Sweden)

    Anna E.M.F.M. Oliveira

    Full Text Available Abstract Pterodon emarginatus Vogel, Fabaceae, is a great source of bioactive compounds. The most known and studied herbal derivative from this species is an ambar-colored oleoresin that contains vouacapane diterpenes and volatile terpenoids, such as β-caryophyllene. Some recent papers aimed to generate nanoemulsions using this oleoresin for biological applications. However, they used high-energy methods that elevate costs of the process or heating procedures, which offer the disadvantage of possible volatile substances loss. Thus, as part of our ongoing studies with nanobiotechnology of natural products, especially regarding preparation of nanoemulsions with promising plant-based oils by low cost and low energy methods, we decided to evaluate the ability of non-heating and solvent-free method to generate P. emarginatus oleoresin-based nanoemulsions. Two non-ionic surfactants were used to generate the nanoemulsions by a simple homogenization method with vortex stirrer. Low mean droplet size (<180 nm and low polydispersity index (<0.200 were observed even after one day of preparation. The low coefficient of variation for the analyzed parameters of different batches and similar profile for droplet size distribution suggested reproducibility of the method. After 30 days, some degree of droplet growth was observed on nanoemulsion prepared with polyethyleneglycol 400 monooleate, while almost no alteration was observed for nanoemulsion prepared with polysorbate 85. Programmed temperature ramp analysis revealed that no major effects on droplet size and polydispersity index were observed, suggesting the robustness of formed nanoemulsions. Thus, the present study shows for the first time the formation of sucupira-based nanoemulsions by a simple, low cost and ecofriendly method. This study opens new perspectives for bioactive evaluation of this novel nano-product.

  10. Structure factor of blends of solvent-free nanoparticle–organic hybrid materials: density-functional theory and small angle X-ray scattering

    KAUST Repository

    Yu, Hsiu-Yu

    2014-09-15

    © the Partner Organisations 2014. We investigate the static structure factor S(q) of solvent-free nanoparticle-organic hybrid materials consisting of silica nanocores and space-filling polyethylene glycol coronas using a density-functional theory and small angle X-ray scattering measurements. The theory considers a bidisperse suspension of hard spheres with different radii and tethered bead-spring oligomers with different grafting densities to approximate the polydispersity effects in experiments. The experimental systems studied include pure samples with different silica core volume fractions and the associated mean corona grafting densities, and blends with different mixing ratios of the pure samples, in order to introduce varying polydispersity of corona grafting density. Our scattering experiments and theory show that, compared to the hard-sphere suspension with the same core volume fraction, S(q) for pure samples exhibit both substantially smaller values at small q and stronger particle correlations corresponding to a larger effective hard core at large q, indicating that the tethered incompressible oligomers enforce a more uniform particle distribution, and the densely grafted brush gives rise to an additional exclusionary effect between the nanoparticles. According to the theory, polydispersity in the oligomer grafting density controls the deviation of S(q) from the monodisperse system at smaller q, and the interplay of the enhanced effective core size and the entropic attraction among the particles is responsible for complex variations in the particle correlations at larger q. The successful comparison between the predictions and the measurements for the blends further suggests that S(q) can be used to assess the uniformity of grafting density in polymer-grafted nanoparticle materials. This journal is

  11. Controlled Solvent-Free Formation of Embedded PDMS-Derived Carbon Nanodomains with Tunable Fluorescence Using Selective Laser Ablation with A Low-Power CD Laser

    Directory of Open Access Journals (Sweden)

    María José González-Vázquez

    2017-10-01

    Full Text Available We present a study of the application of a single-step and solvent-free laser-based strategy to control the formation of polymer-derived fluorescent carbon nanodomains embedded in poly-dimethylsiloxane (PDMS microchannels. A low-power, laser-induced microplasma was used to produce a localised combustion of a PDMS surface and confine nanocarbon byproducts within the exposed microregions. Patterns with on-demand geometries were achieved under dry environmental conditions thanks to a low-cost 3-axis CD-DVD platform motorised in a selective laser ablation fashion. The high temperature required for combustion of PDMS was achieved locally by strongly focusing the laser spot on the desired areas, and the need for high-power laser was bypassed by coating the surface with an absorbing carbon additive layer, hence making the etching of a transparent material possible. The simple and repeatable fabrication process and the spectroscopic characterisation of resulting fluorescent microregions are reported. In situ Raman and fluorescence spectroscopy were used to identify the nature of the nanoclusters left inside the modified areas and their fluorescence spectra as a function of excitation wavelength. Interestingly, the carbon nanodomains left inside the etched micropatterns showed a strong dependency on the additive materials and laser energy that were used to achieve the incandescence and etch microchannels on the surface of the polymer. This dependence on the lasing conditions indicates that our cost-effective laser ablation technique may be used to tune the nature of the polymer-derived nanocarbons, useful for photonics applications in transparent silicones in a rapid-prototyping fashion.

  12. Simultaneously fabrication of free and solidified N, S-doped graphene quantum dots via a facile solvent-free synthesis route for fluorescent detection.

    Science.gov (United States)

    Xia, Chang; Hai, Xin; Chen, Xu-Wei; Wang, Jian-Hua

    2017-06-01

    A facile one-step solvent-free synthesis approach is proposed for the simultaneous fabrication of free and solidified N, S-doped graphene quantum dots (N, S-GQDs) by using citric acid as precursor and L-cysteine as dopant. Graphene nucleus is firstly formed via the intermolecular dehydration of citric acid. N and S are then incorporated into the graphene structure by attacking the margin of graphene nucleus. The cross-linking among the graphene nucleus via the intermolecular condensation leads to the generation of free N, S-GQDs, while the intermolecular amidation between L-cysteine molecules and graphene nucleuses contributes to the solid-state fluorescence graphene quantum dots (SSF-GQDs). The free N, S-GQDs exhibit favorable photoluminescence behaviors such as high fluorescent quantum yield of 74.5%, stable photoluminescence within a wide range of pH and high tolerance to external ionic strength of up to 1.0molL-1 NaCl, making it excellent fluorescence probe for the sensitive detection of Fe3+ with a linear range of 0.01-3μM and a detection limit of 3.3nM. The solidification of GQDs prevents the aggregation of GQDs efficiently and offers the solidified N, S-GQDs yellow-green fluorescence, with a fluorescence quantum yield of 10.6%. This proposed protocol provides a novel avenue to fabricate diverse fluorescent graphene materials for different practical applications. Copyright © 2017 Elsevier B.V. All rights reserved.

  13. Simulations of chemical catalysis

    Science.gov (United States)

    Smith, Gregory K.

    This dissertation contains simulations of chemical catalysis in both biological and heterogeneous contexts. A mixture of classical, quantum, and hybrid techniques are applied to explore the energy profiles and compare possible chemical mechanisms both within the context of human and bacterial enzymes, as well as exploring surface reactions on a metal catalyst. A brief summary of each project follows. Project 1 - Bacterial Enzyme SpvC The newly discovered SpvC effector protein from Salmonella typhimurium interferes with the host immune response by dephosphorylating mitogen-activated protein kinases (MAPKs) with a beta-elimination mechanism. The dynamics of the enzyme substrate complex of the SpvC effector is investigated with a 3.2 ns molecular dynamics simulation, which reveals that the phosphorylated peptide substrate is tightly held in the active site by a hydrogen bond network and the lysine general base is positioned for the abstraction of the alpha hydrogen. The catalysis is further modeled with density functional theory (DFT) in a truncated active-site model at the B3LYP/6-31 G(d,p) level of theory. The truncated model suggested the reaction proceeds via a single transition state. After including the enzyme environment in ab initio QM/MM studies, it was found to proceed via an E1cB-like pathway, in which the carbanion intermediate is stabilized by an enzyme oxyanion hole provided by Lys104 and Tyr158 of SpvC. Project 2 - Human Enzyme CDK2 Phosphorylation reactions catalyzed by kinases and phosphatases play an indispensable role in cellular signaling, and their malfunctioning is implicated in many diseases. Ab initio quantum mechanical/molecular mechanical studies are reported for the phosphoryl transfer reaction catalyzed by a cyclin-dependent kinase, CDK2. Our results suggest that an active-site Asp residue, rather than ATP as previously proposed, serves as the general base to activate the Ser nucleophile. The corresponding transition state features a

  14. Oxy-Allyl Cation Catalysis: An Enantioselective Electrophilic Activation Mode

    Science.gov (United States)

    Liu, Chun; Oblak, E. Zachary; Vander Wal, Mark N.; Dilger, Andrew K.; Almstead, Danielle K.; MacMillan, David W. C.

    2016-01-01

    A generic activation mode for asymmetric LUMO-lowering catalysis has been developed using the long-established principles of oxy-allyl cation chemistry. Here, the enantioselective conversion of racemic α-tosyloxy ketones to optically enriched α-indolic carbonyls has been accomplished using a new amino alcohol catalyst in the presence of electron-rich indole nucleophiles. Kinetic studies reveal that the rate-determining step in this SN1 pathway is the catalyst-mediated α-tosyloxy ketone deprotonation step to form an enantiodiscriminant oxy-allyl cation prior to the stereodefining nucleophilic addition event. PMID:26797012

  15. Microwave Assisted Convenient One-Pot Synthesis of Coumarin Derivatives via Pechmann Condensation Catalyzed by FeF3 under Solvent-Free Conditions and Antimicrobial Activities of the Products

    Directory of Open Access Journals (Sweden)

    Vahid Vahabi

    2014-08-01

    Full Text Available A rapid and efficient solvent-free one-pot synthesis of coumarin derivatives by Pechmann condensation reactions of phenols with ethyl acetoacetate using FeF3 as a catalyst under microwave irradiation is described. This one-pot synthesis on a solid inorganic support provides the products in good yields. The newly synthesized compounds were systematically characterized by IR, 1H-NMR, 13C-NMR, MS and elemental CHN analyses. The proposed solvent-free microwave irradiation method using the environmentally friendly catalyst FeF3 offers the unique advantages of high yields, shorter reaction times, easy and quick isolation of the products, excellent chemoselectivity, and a one-pot, green synthesis. The products were screened for antimicrobial activity, and the results showed that the compounds reacted against all the tested bacteria.

  16. A combined continuous microflow photochemistry and asymmetric organocatalysis approach for the enantioselective synthesis of tetrahydroquinolines

    OpenAIRE

    Erli Sugiono; Magnus Rueping

    2013-01-01

    Summary A continuous-flow asymmetric organocatalytic photocyclization?transfer hydrogenation cascade reaction has been developed. The new protocol allows the synthesis of tetrahydroquinolines from readily available 2-aminochalcones using a combination of photochemistry and asymmetric Br?nsted acid catalysis. The photocylization and subsequent reduction was performed with catalytic amount of chiral BINOL derived phosphoric acid diester and Hantzsch dihydropyridine as hydrogen source providing ...

  17. A combined continuous microflow photochemistry and asymmetric organocatalysis approach for the enantioselective synthesis of tetrahydroquinolines.

    Science.gov (United States)

    Sugiono, Erli; Rueping, Magnus

    2013-01-01

    A continuous-flow asymmetric organocatalytic photocyclization-transfer hydrogenation cascade reaction has been developed. The new protocol allows the synthesis of tetrahydroquinolines from readily available 2-aminochalcones using a combination of photochemistry and asymmetric Brønsted acid catalysis. The photocylization and subsequent reduction was performed with catalytic amount of chiral BINOL derived phosphoric acid diester and Hantzsch dihydropyridine as hydrogen source providing the desired products in good yields and with excellent enantioselectivities.

  18. A combined continuous microflow photochemistry and asymmetric organocatalysis approach for the enantioselective synthesis of tetrahydroquinolines

    Directory of Open Access Journals (Sweden)

    Erli Sugiono

    2013-11-01

    Full Text Available A continuous-flow asymmetric organocatalytic photocyclization–transfer hydrogenation cascade reaction has been developed. The new protocol allows the synthesis of tetrahydroquinolines from readily available 2-aminochalcones using a combination of photochemistry and asymmetric Brønsted acid catalysis. The photocylization and subsequent reduction was performed with catalytic amount of chiral BINOL derived phosphoric acid diester and Hantzsch dihydropyridine as hydrogen source providing the desired products in good yields and with excellent enantioselectivities.

  19. Nano Fe2O3, clinoptilolite and H3PW12O40 as efficient catalysts for solvent-free synthesis of 5(4H)-isoxazolone under microwave irradiation conditions

    OpenAIRE

    Fozooni, Samieh; Hosseinzadeh, Nasrin Gholam; Hamidian, Hooshang; Akhgar, Mohammad Reza

    2013-01-01

    A quick and solvent-free approach involving the exposure of neat reactants to microwave irradiation in conjunction with the use of clinoptilolite, H3PW12O40 and Fe2O3 nanoparticle catalysts is described. In this work, condensation of hydroxylamine hydrochloride, sodium acetate, acetoacetic or benzoyl acetic ethyl ester and appropriate aldehydes by employing catalysts gave 5(4H)-isoxazolone only in one step. Catalyst amount, temperature effects and catalysts reusability were monitored. Among t...

  20. B2O3/Al2O3 as a new, highly efficient and reusable heterogeneous catalyst for the selective synthesis of β-enamino ketones and esters under solvent-free conditions

    OpenAIRE

    Chen,Jiu-Xi; Zhang,Chang-Fu; Gao,Wen-Xia; Jin,Hui-Le; Ding,Jin-Chang; Wu,Hua-Yue

    2010-01-01

    Boron oxide adsorbed on alumina (B2O3/Al2O3 ) has been found to be a new and highly efficient heterogeneous catalyst for the synthesis of β-enamino ketones and esters by the enamination of various primary and secondary amines with β-dicarbonyl compounds under solvent-free conditions. The important features of this methodology are broad substrate scope, high yield, no requirement of metal catalysts, high regio- and chemoselectivity and environmental friendliness. In addition, the cat...

  1. An Efficient Synthesis of 3,4-Dihydropyrimidin-2(1H-Ones and Thiones Catalyzed by a Novel Brønsted Acidic Ionic Liquid under Solvent-Free Conditions

    Directory of Open Access Journals (Sweden)

    Yonghong Zhang

    2015-02-01

    Full Text Available We report here an efficient and green method for Biginelli condensation reaction of aldehydes, β-ketoesters and urea or thiourea catalyzed by Brønsted acidic ionic liquid [Btto][p-TSA] under solvent-free conditions. Compared to the classical Biginelli reaction conditions, the present method has the advantages of giving good yields, short reaction times, near room temperature conditions and the avoidance of the use of organic solvents and metal catalyst.

  2. Two New 1,1,3,3-Tetramethylguanidinium Halochromates (C5H14N3CrO3X (X: Cl, F: Efficient Reagents for Oxidation of Organic Substrates under Solvent-Free Conditions and Microwave Irradiation

    Directory of Open Access Journals (Sweden)

    Kıvılcım Şendıl

    2016-01-01

    Full Text Available Two new mild oxidizing agents 1,1,3,3-tetramethylguanidinium fluorochromate (TMGFC and 1,1,3,3-tetramethylguanidinium chlorochromate (TMGCC were prepared in high yields by reacting tetramethylguanidine with CrO3 and related acid. These reagents are suitable to oxidize various primary and secondary alcohols and oximes to the corresponding carbonyl compounds under solvent-free conditions and microwave irradiation.

  3. A Survey Course in Catalysis.

    Science.gov (United States)

    Skaates, J. M.

    1982-01-01

    Describes a 10-week survey course in catalysis for chemical engineering and chemistry students designed to show how modern chemistry and chemical engineering interact in the ongoing development of industrial catalysts. Includes course outline and instructional strategies. (Author/JN)

  4. Editorial: Nanoscience makes catalysis greener

    KAUST Repository

    Polshettiwar, Vivek

    2012-01-09

    Green chemistry by nanocatalysis: Catalysis is a strategic field of science because it involves new ways of meeting energy and sustainability challenges. The concept of green chemistry, which makes the science of catalysis even more creative, has become an integral part of sustainability. This special issue is at the interface of green chemistry and nanocatalysis, and features excellent background articles as well as the latest research results. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Enhanced Micellar Catalysis LDRD.

    Energy Technology Data Exchange (ETDEWEB)

    Betty, Rita G.; Tucker, Mark D; Taggart, Gretchen; Kinnan, Mark K.; Glen, Crystal Chanea; Rivera, Danielle; Sanchez, Andres; Alam, Todd Michael

    2012-12-01

    The primary goals of the Enhanced Micellar Catalysis project were to gain an understanding of the micellar environment of DF-200, or similar liquid CBW surfactant-based decontaminants, as well as characterize the aerosolized DF-200 droplet distribution and droplet chemistry under baseline ITW rotary atomization conditions. Micellar characterization of limited surfactant solutions was performed externally through the collection and measurement of Small Angle X-Ray Scattering (SAXS) images and Cryo-Transmission Electron Microscopy (cryo-TEM) images. Micellar characterization was performed externally at the University of Minnesotas Characterization Facility Center, and at the Argonne National Laboratory Advanced Photon Source facility. A micellar diffusion study was conducted internally at Sandia to measure diffusion constants of surfactants over a concentration range, to estimate the effective micelle diameter, to determine the impact of individual components to the micellar environment in solution, and the impact of combined components to surfactant phase behavior. Aerosolized DF-200 sprays were characterized for particle size and distribution and limited chemical composition. Evaporation rates of aerosolized DF-200 sprays were estimated under a set of baseline ITW nozzle test system parameters.

  6. The Combinatorial Approach to Asymmetric Hydrogenation : Phosphoramidite Libraries, Ruthenacycles, and Artificial Enzymes

    NARCIS (Netherlands)

    Vries, Johannes G. de; Lefort, Laurent

    2006-01-01

    For a more general implementation of asymmetric catalysis in the production of fine chemicals, the screening for new catalysts and ligands must be dramatically accelerated. This is possible with a high-throughput experimentation (HTE) approach. However, implementation of this technology requires the

  7. Magnetic catalysis in flavored ABJM

    Energy Technology Data Exchange (ETDEWEB)

    Jokela, Niko; Ramallo, Alfonso V. [Departamento de Física de Partículas, Universidade de Santiago de Compostela and Instituto Galego de Física de Altas Enerxías (IGFAE), E-15782 Santiago de Compostela (Spain); Zoakos, Dimitrios [Centro de Física do Porto and Departamento de Física e Astronomia, Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto (Portugal)

    2014-02-05

    We study the magnetic catalysis of chiral symmetry breaking in the ABJM Chern-Simons matter theory with unquenched flavors in the Veneziano limit. We consider a magnetized D6-brane probe in the background of a flavored black hole which includes the backreaction of massless smeared flavors in the ABJM geometry. We find a holographic realization for the running of the quark mass due to the dynamical flavors. We compute several thermodynamic quantities of the brane probe and analyze the effects of the dynamical quarks on the fundamental condensate and on the phase diagram of the model. The dynamical flavors have an interesting effect on the magnetic catalysis. At zero temperature and fixed magnetic field, the magnetic catalysis is suppressed for small bare quark masses whereas it is enhanced for large values of the mass. When the temperature is non-zero there is a critical magnetic field, above which the magnetic catalysis takes place. This critical magnetic field decreases with the number of flavors, which we interpret as an enhancement of the catalysis.

  8. Enantioselective Synthesis of Isoquinolines: Merging Chiral-Phosphine and Gold Catalysis.

    Science.gov (United States)

    Gao, Yu-Ning; Shi, Feng-Chen; Xu, Qin; Shi, Min

    2016-05-10

    The highly enantioselective synthesis of dihydroisoquinoline derivatives from aromatic sulfonated imines tethered with an alkyne moiety, through a one-pot asymmetric relay catalysis of chiral-phosphine and gold catalysts, is reported. Enantiomerically enriched dihydroisoquinoline derivatives were afforded in good yields and good-to-excellent ee values under mild conditions, based on the asymmetric aza-Morita-Baylis-Hillman reaction. Dihydroisoquinoline derivatives containing two chiral centers were also synthesized through further transformations. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Fundamental insights into interfacial catalysis.

    Science.gov (United States)

    Gong, Jinlong; Bao, Xinhe

    2017-04-03

    Surface and interfacial catalysis plays a vital role in chemical industries, electrochemistry and photochemical reactions. The challenges of modern chemistry are to optimize the chemical reaction processes and understand the detailed mechanism of chemical reactions. Since the early 1960s, the foundation of surface science systems has allowed the study of surface and interfacial phenomena on atomic/molecular level, and thus brought a number of significant developments to fundamental and technological processes, such as catalysis, material science and biochemistry, just to name a few. This themed issue describes the recent advances and developments in the fundamental understanding of surface and interfacial catalysis, encompassing areas of knowledge from metal to metal oxide, carbide, graphene, hexagonal boron nitride, and transition metal dichalcogenides under ultrahigh vacuum conditions, as well as under realistic reaction conditions.

  10. Operando research in heterogeneous catalysis

    CERN Document Server

    Groot, Irene

    2017-01-01

    This book is devoted to the emerging field of techniques for visualizing atomic-scale properties of active catalysts under actual working conditions, i.e. high gas pressures and high temperatures. It explains how to understand these observations in terms of the surface structures and dynamics and their detailed interplay with the gas phase. This provides an important new link between fundamental surface physics and chemistry, and applied catalysis. The book explains the motivation and the necessity of operando studies, and positions these with respect to the more traditional low-pressure investigations on the one hand and the reality of industrial catalysis on the other. The last decade has witnessed a rapid development of new experimental and theoretical tools for operando studies of heterogeneous catalysis. The book has a strong emphasis on the new techniques and illustrates how the challenges introduced by the harsh, operando conditions are faced for each of these new tools. Therefore, one can also read th...

  11. Stress Controlled Catalysis via Engineered Nanostructures

    Science.gov (United States)

    2016-03-02

    fields on catalysis : “Stress Controlled Catalysis via Engineered Nanostructures.” For this effort a workshop was organized and held at Brown... Catalysis via Engineered Nanostructures" The views, opinions and/or findings contained in this report are those of the author(s) and should not contrued...Support for current award "Stress Controlled Catalysis via Engineered Nanostructures" Report Title This is the final report of the ARO project of

  12. Catalysis and sustainable (green) chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Centi, Gabriele; Perathoner, Siglinda [Dipartimento di Chimica Industriale ed Ingegneria dei Materiali, University of Messina, Salita Sperone 31, 98166 Messina (Italy)

    2003-01-15

    Catalysis is a key technology to achieve the objectives of sustainable (green) chemistry. After introducing the concepts of sustainable (green) chemistry and a brief assessment of new sustainable chemical technologies, the relationship between catalysis and sustainable (green) chemistry is discussed and illustrated via an analysis of some selected and relevant examples. Emphasis is also given to the concept of catalytic technologies for scaling-down chemical processes, in order to develop sustainable production processes which reduce the impact on the environment to an acceptable level that allows self-depuration processes of the living environment.

  13. Photoredox Catalysis in Organic Chemistry

    Science.gov (United States)

    2016-01-01

    In recent years, photoredox catalysis has come to the forefront in organic chemistry as a powerful strategy for the activation of small molecules. In a general sense, these approaches rely on the ability of metal complexes and organic dyes to convert visible light into chemical energy by engaging in single-electron transfer with organic substrates, thereby generating reactive intermediates. In this Perspective, we highlight the unique ability of photoredox catalysis to expedite the development of completely new reaction mechanisms, with particular emphasis placed on multicatalytic strategies that enable the construction of challenging carbon–carbon and carbon–heteroatom bonds. PMID:27477076

  14. Aromatic Chlorosulfonylation by Photoredox Catalysis.

    Science.gov (United States)

    Májek, Michal; Neumeier, Michael; Jacobi von Wangelin, Axel

    2017-01-10

    Visible-light photoredox catalysis enables the efficient synthesis of arenesulfonyl chlorides from anilines. The new protocol involves the convenient in situ preparation of arenediazonium salts (from anilines) and the reactive gases SO 2 and HCl (from aqueous SOCl 2 ). The photocatalytic chlorosulfonylation operates at mild conditions (room temperature, acetonitrile/water) with low catalyst loading. Various functional groups are tolerated (e.g., halides, azides, nitro groups, CF 3 , SF 5 , esters, heteroarenes). Theoretical and experimental studies support a photoredox-catalysis mechanism. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. β-cyclodextrin-polyurethane polymer: A neutral and eco-friendly heterogeneous catalyst for the one-pot synthesis of 1,4-dihydropyridine and polyhydroquinolien derivatives via Hantzsch reaction under solvent-free conditions

    Directory of Open Access Journals (Sweden)

    Kiasat Ali Reza

    2014-01-01

    Full Text Available An efficient synthesis of 1,4-dihydropyridine & polyhydroquinolien derivatives using b-Cyclodextrin-polyurethane polymer (β-CDPU as a stationary microvessel and neutral heterogeneous catalyst via a four component coupling of aldehydes, β-ketoester (2 mol and ammonium acetate under solvent-free conditions is described. Compared with the classical Hantzsch reaction, this new method has the advantages of good yield, short reaction time and methodological simplicity. β-CDPU was proved to be an efficient heterogeneous catalyst which could be easily handled and removed from the reaction mixture by simple filtration, and also recovered and reused without loss of reactivity.

  16. Synthesis, characterization and catalytic application of silica supported tin oxide nanoparticles for synthesis of 2,4,5-tri and 1,2,4,5-tetrasubstituted imidazoles under solvent-free conditions

    Directory of Open Access Journals (Sweden)

    Ashok V. Borhade

    2017-02-01

    Full Text Available Highly efficient and eco-friendly, one pot synthesis of 1,2,4,5-tetra substituted imidazoles and 2,4,5-trisubstituted imidazoles was reported under solvent free conditions using nanocrystalline silica supported tin oxide (SiO2:SnO2 as a catalyst with excellent yield. The present methodology offers several advantages such as mild reaction conditions, short reaction time, good yield, high purity of product, recyclable catalyst without a noticeable decrease in catalytic activity and can be used for large scale synthesis. The synthesized SiO2:SnO2 nanocrystalline catalyst was characterized by XRD, BET surface area and TEM techniques.

  17. Solvent free one-pot multi-component synthesis of 3,4-dihydropyrimidin-2(1H-ones catalyzed by mesoporous NH4H2PO4/MCM-41 as an environmentally friendly, cheap, and effective catalyst

    Directory of Open Access Journals (Sweden)

    R. Tayebee

    2017-02-01

    Full Text Available A green and efficient method is described for the solvent free synthesis of 3,4-dihydropyrimidin-2(1H-ones through one-pot three-component condensation of ethyl acetoacetate, an aryl aldehyde, and urea using mesoporous MCM-41 supported ammonium dihydrogen phosphate (NH4H2PO4/MCM-41 as catalyst. The present methodology offers several advantages such as high yields, relatively short reaction times, mild reaction condition, easy work up, and using a highly recyclable catalyst. Some mechanistic studies revealed that the reaction would be achieved via formation of an acyliminium ion, followed by an acid-catalyzed cyclodehydration step.

  18. Synthesis and QSAR Study of (4-Oxo-3-aryl-3,4-dihydro-quinazolin-2-ylsulfanyl-propionic Acid arylidene/aryl-ethylidene-hydrazides via Microwave Assisted Solvent Free Reations

    Directory of Open Access Journals (Sweden)

    M. B. Deshmukh

    2004-01-01

    Full Text Available In the present work, s-alkylated derivatives of thio-quinazolinone were obtained using Methyl 2-chloro propionate via a solvent-free microwave-assisted method. The alkylated thio quinazolinones were further sequentially condensed with hydrazine hydrate and different aromatic aldehydes to get the hydrazides, which were studied for QSAR. The synthesized compounds were subjected to a prediction of biological activities. A software application (PASS was used for this purpose. . The relationship between structure and different biological activities was studied and the different derivatives were recommended for the screening of some specific activities like anti-tuberculosic, anti-mycobacterial & HDL cholesterol increasing activities.

  19. Molecular Mechanism of Heterogeneous Catalysis

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 13; Issue 6. Molecular Mechanism of Heterogeneous Catalysis - The 2007 Nobel Prize in Chemistry. R S Swathi K L Sebastian. General Article Volume 13 Issue 6 June 2008 pp 548-560 ...

  20. Catalysis in Molten Ionic Media

    DEFF Research Database (Denmark)

    Boghosian, Soghomon; Fehrmann, Rasmus

    2013-01-01

    This chapter deals with catalysis in molten salts and ionic liquids, which are introduced and reviewed briefly, while an in-depth review of the oxidation catalyst used for the manufacturing of sulfuric acid and cleaning of flue gas from electrical power plants is the main topic of the chapter...

  1. Cyclopalladated complexes in enantioselective catalysis

    Science.gov (United States)

    Dunina, Valeria V.; Gorunova, Olga N.; Zykov, P. A.; Kochetkov, Konstantin A.

    2011-01-01

    The results of the use of optically active palladacycles in enantioselective catalysis of [3,3]-sigmatropic rearrangements, aldol condensation, the Michael reaction and cross-coupling are analyzed. Reactions with allylic substrates or reagents and some other transformations are considered.

  2. Transition Metal Complexes and Catalysis

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 4; Issue 9. Transition Metal Complexes and Catalysis. Balaji R Jagirdar. General Article Volume 4 Issue 9 September 1999 pp 63-81. Fulltext. Click here to view fulltext PDF. Permanent link: http://www.ias.ac.in/article/fulltext/reso/004/09/0063-0081 ...

  3. Asymmetric Divisions in Oogenesis.

    Science.gov (United States)

    Bilinski, Szczepan M; Kubiak, Jacek Z; Kloc, Malgorzata

    In the majority of animals, the oocyte/egg is structurally, molecularly, and functionally asymmetric. Such asymmetry is a prerequisite for a flawless fertilization and faithful segregation of maternal determinants during subsequent embryonic development. The oocyte asymmetry develops during oogenesis and must be maintained during consecutive and obligatorily asymmetric oogonial divisions, which depending on the species lead to the formation of either oocyte alone or oocyte and nurse cell complex. In the following chapter, we summarize current knowledge on the asymmetric oogonial divisions in invertebrate (insects) and vertebrate (Xenopus) species.

  4. Solvent-free dry powder coating process for low-cost manufacturing of LiNi1/3Mn1/3Co1/3O2 cathodes in lithium-ion batteries

    Science.gov (United States)

    Al-Shroofy, Mohanad; Zhang, Qinglin; Xu, Jiagang; Chen, Tao; Kaur, Aman Preet; Cheng, Yang-Tse

    2017-06-01

    We report a solvent-free dry powder coating process for making LiNi1/3Mn1/3Co1/3O2 (NMC) positive electrodes in lithium-ion batteries. This process eliminates volatile organic compound emission and reduces thermal curing time from hours to minutes. A mixture of NMC, carbon black, and poly(vinylidene difluoride) was electrostatically sprayed onto an aluminum current collector, forming a uniformly distributed electrode with controllable thickness and porosity. Charge/discharge cycling of the dry-powder-coated electrodes in lithium-ion half cells yielded a discharge specific capacity of 155 mAh g-1 and capacity retention of 80% for more than 300 cycles when the electrodes were tested between 3.0 and 4.3 V at a rate of C/5. The long-term cycling performance and durability of dry-powder coated electrodes are similar to those made by the conventional wet slurry-based method. This solvent-free dry powder coating process is a potentially lower-cost, higher-throughput, and more environmentally friendly manufacturing process compared with the conventional wet slurry-based electrode manufacturing method.

  5. Organocatalyzed asymmetric Michael addition by an efficient bifunctional carbohydrate-thiourea hybrid with mechanistic DFT analysis.

    Science.gov (United States)

    Azad, Chandra S; Khan, Imran A; Narula, Anudeep K

    2016-12-28

    A series of thiourea based bifunctional organocatalysts having d-glucose as a core scaffold were synthesized and examined as catalysts for the asymmetric Michael addition reaction of aryl/alkyl trans-β-nitrostyrenes over cyclohexanone and other Michael donors having active methylene. Excellent enantioselectivities (<95%), diastereoselectivities (<99%), and yields (<99%) were attained under solvent free conditions using 10 mol% of 1d0. The obtained results were explained through DFT calculations using the B3LYP/6-311G(d,p)//B3LYP/6-31G(d) basic set. The QM/MM calculations revealed the role of cyclohexanone as a solvent as well as reactant in the rate determining step imparting 31.91 kcal mol(-1) of energy towards the product formation.

  6. Molecular catalysis science: Perspective on unifying the fields of catalysis.

    Science.gov (United States)

    Ye, Rong; Hurlburt, Tyler J; Sabyrov, Kairat; Alayoglu, Selim; Somorjai, Gabor A

    2016-05-10

    Colloidal chemistry is used to control the size, shape, morphology, and composition of metal nanoparticles. Model catalysts as such are applied to catalytic transformations in the three types of catalysts: heterogeneous, homogeneous, and enzymatic. Real-time dynamics of oxidation state, coordination, and bonding of nanoparticle catalysts are put under the microscope using surface techniques such as sum-frequency generation vibrational spectroscopy and ambient pressure X-ray photoelectron spectroscopy under catalytically relevant conditions. It was demonstrated that catalytic behavior and trends are strongly tied to oxidation state, the coordination number and crystallographic orientation of metal sites, and bonding and orientation of surface adsorbates. It was also found that catalytic performance can be tuned by carefully designing and fabricating catalysts from the bottom up. Homogeneous and heterogeneous catalysts, and likely enzymes, behave similarly at the molecular level. Unifying the fields of catalysis is the key to achieving the goal of 100% selectivity in catalysis.

  7. Electric Fields and Enzyme Catalysis.

    Science.gov (United States)

    Fried, Stephen D; Boxer, Steven G

    2017-06-20

    What happens inside an enzyme's active site to allow slow and difficult chemical reactions to occur so rapidly? This question has occupied biochemists' attention for a long time. Computer models of increasing sophistication have predicted an important role for electrostatic interactions in enzymatic reactions, yet this hypothesis has proved vexingly difficult to test experimentally. Recent experiments utilizing the vibrational Stark effect make it possible to measure the electric field a substrate molecule experiences when bound inside its enzyme's active site. These experiments have provided compelling evidence supporting a major electrostatic contribution to enzymatic catalysis. Here, we review these results and develop a simple model for electrostatic catalysis that enables us to incorporate disparate concepts introduced by many investigators to describe how enzymes work into a more unified framework stressing the importance of electric fields at the active site.

  8. Catalysis in the Primordial World

    Directory of Open Access Journals (Sweden)

    Nenad Raos

    2017-11-01

    Full Text Available Catalysis provides orderly prebiotic synthesis and eventually its evolution into autocatalytic (self-reproduction systems. Research on homogeneous catalysis is concerned mostly with random peptide synthesis and the chances to produce catalytic peptide oligomers. Synthesis of ribose via formose reaction was found to be catalysed by B(OH4−, presumably released by weathering of borate minerals. Oxide and clay mineral surfaces provide catalytic sites for the synthesis of oligopeptides and oligonucleotides. Chemoautotrophic or iron-sulphur-world theory assumes that the first (pioneer organisms developed by catalytic processes on (Fe/NiS particles formed near/close hydrothermal vents. The review provides an overlay of possible catalytic reactions in prebiotic environment, discussing their selectivity (regioselectivity, stereoselectivity as well as geological availability of catalytic minerals and geochemical conditions enabling catalytic reactions on early Earth.

  9. A new magnetically recoverable catalyst promoting the synthesis of 1,4-dihydropyridine and polyhydroquinoline derivatives via the Hantzsch condensation under solvent-free conditions

    Energy Technology Data Exchange (ETDEWEB)

    Taheri, Narges; Heidarizadeh, Fariba; Kiasat, Alireza

    2017-04-15

    In the current study, 1,4-dihydropyridine and polyhydroquinoline derivatives were efficiently synthesized under solvent-less conditions with a magnetic catalyst containing novel acidic ionic liquid functionalized silica modified Fe{sub 3}O{sub 4} nanoparticles through a four component combination of β-ketoester, aldehydes and ammonium acetate (1, 2, 2). Several approaches have been reported for synthesizing these derivatives, while each of these approaches have some weaknesses including long time of reaction, excess of volatile organic solvent, low efficiency, costly reagents, complex operation, high temperatures, production of a number of side products, and difficult catalyst recovery. The simple operation, short time of reaction (5–30 min) and the high efficiency (80–94%) are the special advantages of this technique. The immobilized catalyst exhibited an appropriate thermal stability and excellent recyclability. Different methods such as FT-IR, SEM, EDX, TGA-DTA, and VSM were used to confirm and characterize the catalyst. - Highlights: • A new acidic ionic liquid were first synthesized and applied in both symmetric and asymmetric hantzsch reactions for preparing 1, 4-dihydropyridine and polyhydroquinoline derivatives with high efficiencies under solvent-less conditions. • The immobilized catalyst exhibited an appropriate thermal stability and excellent recyclability. • The nanomagnetic catalyst could be recovered from solution with an external magnet at once, allowing undemanding recovery and reuse. • The catalyst was reused for five times with no considerable decrease in catalytic activity.

  10. Reaction Selectivity in Heterogeneous Catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Somorjai, Gabor A.; Kliewer, Christopher J.

    2009-02-02

    The understanding of selectivity in heterogeneous catalysis is of paramount importance to our society today. In this review we outline the current state of the art in research on selectivity in heterogeneous catalysis. Current in-situ surface science techniques have revealed several important features of catalytic selectivity. Sum frequency generation vibrational spectroscopy has shown us the importance of understanding the reaction intermediates and mechanism of a heterogeneous reaction, and can readily yield information as to the effect of temperature, pressure, catalyst geometry, surface promoters, and catalyst composition on the reaction mechanism. DFT calculations are quickly approaching the ability to assist in the interpretation of observed surface spectra, thereby making surface spectroscopy an even more powerful tool. HP-STM has revealed three vitally important parameters in heterogeneous selectivity: adsorbate mobility, catalyst mobility, and selective site-blocking. The development of size controlled nanoparticles from 0.8 to 10 nm, of controlled shape, and of controlled bimetallic composition has revealed several important variables for catalytic selectivity. Lastly, DFT calculations may be paving the way to guiding the composition choice for multi-metallic heterogeneous catalysis for the intelligent design of catalysts incorporating the many factors of selectivity we have learned.

  11. Dynamic control of chirality in phosphine ligands for enantioselective catalysis.

    Science.gov (United States)

    Zhao, Depeng; Neubauer, Thomas M; Feringa, Ben L

    2015-03-25

    Chirality plays a fundamental role in biology and chemistry and the precise control of chirality in a catalytic conversion is a key to modern synthesis most prominently seen in the production of pharmaceuticals. In enantioselective metal-based catalysis, access to each product enantiomer is commonly achieved through ligand design with chiral bisphosphines being widely applied as privileged ligands. Switchable phosphine ligands, in which chirality is modulated through an external trigger signal, might offer attractive possibilities to change enantioselectivity in a catalytic process in a non-invasive manner avoiding renewed ligand synthesis. Here we demonstrate that a photoswitchable chiral bisphosphine based on a unidirectional light-driven molecular motor, can be used to invert the stereoselectivity of a palladium-catalysed asymmetric transformation. It is shown that light-induced changes in geometry and helicity of the switchable ligand enable excellent selectivity towards the racemic or individual enantiomers of the product in a Pd-catalysed desymmetrization reaction.

  12. Collective synthesis of natural products by means of organocascade catalysis

    Science.gov (United States)

    Jones, Spencer B.; Simmons, Bryon; Mastracchio, Anthony; MacMillan, David W. C.

    2012-01-01

    Organic chemists are now able to synthesize small quantities of almost any known natural product, given sufficient time, resources and effort. However, translation of the academic successes in total synthesis to the large-scale construction of complex natural products and the development of large collections of biologically relevant molecules present significant challenges to synthetic chemists. Here we show that the application of two nature-inspired techniques, namely organocascade catalysis and collective natural product synthesis, can facilitate the preparation of useful quantities of a range of structurally diverse natural products from a common molecular scaffold. The power of this concept has been demonstrated through the expedient, asymmetric total syntheses of six well-known alkaloid natural products: strychnine, aspidospermidine, vincadifformine, akuammicine, kopsanone and kopsinine. PMID:21753848

  13. Nanometallic chemistry: deciphering nanoparticle catalysis from the perspective of organometallic chemistry and homogeneous catalysis.

    Science.gov (United States)

    Yan, Ning; Yuan, Yuan; Dyson, Paul J

    2013-10-07

    Nanoparticle (NP) catalysis is traditionally viewed as a sub-section of heterogeneous catalysis. However, certain properties of NP catalysts, especially NPs dispersed in solvents, indicate that there could be benefits from viewing them from the perspective of homogeneous catalysis. By applying the fundamental approaches and concepts routinely used in homogeneous catalysis to NP catalysts it should be possible to rationally design new nanocatalysts with superior properties to those currently in use.

  14. Cosmic strings and baryon decay catalysis

    Science.gov (United States)

    Gregory, Ruth; Perkins, W. B.; Davis, A.-C.; Brandenberger, R. H.

    1989-01-01

    Cosmic strings, like monopoles, can catalyze proton decay. For integer charged fermions, the cross section for catalysis is not amplified, unlike in the case of monopoles. The catalysis processes are reviewed both in the free quark and skyrmion pictures and the implications for baryogenesis are discussed. A computation of the cross section for monopole catalyzed skyrmion decay is presented using classical physics. Also discussed are some effects which can screen catalysis processes.

  15. Solid acid catalysis from fundamentals to applications

    CERN Document Server

    Hattori, Hideshi

    2014-01-01

    IntroductionTypes of solid acid catalystsAdvantages of solid acid catalysts Historical overviews of solid acid catalystsFuture outlookSolid Acids CatalysisDefinition of acid and base -Brnsted acid and Lewis acid-Acid sites on surfacesAcid strengthRole of acid sites in catalysisBifunctional catalysisPore size effect on catalysis -shape selectivity-Characterization of Solid Acid Catalysts Indicator methodTemperature programmed desorption (TPD) of ammoniaCalorimetry of adsorption of basic moleculesInfrare

  16. Asymmetrical field emitter

    Science.gov (United States)

    Fleming, J.G.; Smith, B.K.

    1995-10-10

    A method is disclosed for providing a field emitter with an asymmetrical emitter structure having a very sharp tip in close proximity to its gate. One preferred embodiment of the present invention includes an asymmetrical emitter and a gate. The emitter having a tip and a side is coupled to a substrate. The gate is connected to a step in the substrate. The step has a top surface and a side wall that is substantially parallel to the side of the emitter. The tip of the emitter is in close proximity to the gate. The emitter is at an emitter potential, and the gate is at a gate potential such that with the two potentials at appropriate values, electrons are emitted from the emitter. In one embodiment, the gate is separated from the emitter by an oxide layer, and the emitter is etched anisotropically to form its tip and its asymmetrical structure. 17 figs.

  17. Ni2+ supported on hydroxyapatite-core@shell γ-Fe2O3 nanoparticles as new and green catalyst for the synthesis of 3,4-dihydropyrimidin-2(1H-ones under solvent-free condition

    Directory of Open Access Journals (Sweden)

    Eshagh Rezaee Nezhad

    2013-10-01

    Full Text Available The aim of this research is to study Ni2+ supported on hydroxyapatite-core-shell magnetic γ-Fe2O3 nanoparticles (γ-Fe2O3@HAp-Ni2+ as a green and recyclable catalyst for the Biginelli reaction under solvent-free conditions. One-pot multi-component condensation of 1,3-dicarbonyl compounds, urea and aldehydes at 80 oC affords the corresponding compounds in high yields and in short reaction times using γ-Fe2O3@HAp-Ni2+. The catalyst can be readily isolated using an external magnet and no obvious loss of activity was observed when the catalyst was reused in seven consecutive runs. The mean size and the surface morphology of the nanoparticles were characterized by transmission electron microscopy, scanning electron microscope, vibrating sample magnetometry, X-ray powder diffraction and Fourier transform infrared techniques.

  18. Molybdenum oxide supported on silica (MoO{sub 3}/SiO{sub 2}): an efficient and reusable catalyst for the synthesis of 1,8-dioxodecahydroacridines under solvent-free conditions

    Energy Technology Data Exchange (ETDEWEB)

    Khojastehnezhad, A.; Vafaei, M. [Islamic Azad University, Mashhad Branch, Department of Chemistry, Mashhad (Iran, Islamic Republic of); Moeinpour, F., E-mail: akhojastehnezhad@yahoo.com [Islamic Azad University, Bandar Abbas Branch, Department of Chemistry, Bandar Abbas (Iran, Islamic Republic of)

    2014-07-01

    Silica supported molybdenum oxide (MoO{sub 3}/SiO{sub 2}) was found to be and efficient, eco-friendly and heterogeneous catalyst for the multicomponent reaction of aromatic aldehydes, dimedone and ammonium acetate or aromatic amines under solvent-free conditions to afford the corresponding 1,8-dioxodecahydroacridines in high yields. The catalyst can be easily recovered and reused for several times without considerable loss of activity. Furthermore, the present method offers several advantages, such as an easy experimental and work-up procedures, short reaction times and good to excellent yields. For the characterization were used: Fourier transform infrared spectroscopy (Ft-IR), X-ray diffraction and scanning electron microscopy analyses. (Author)

  19. A Simple and Efficient Synthesis of 4-Arylacridinediones and 6-Aryldiindeno[1,2-b:2,1-e]pyridinediones Using CuI Nanoparticles as Catalyst under Solvent-Free Conditions.

    Science.gov (United States)

    Abdolmohammadi, Shahrzad; Hosseinian, Akram; Dahi-Azar, Saman; Mohammadnejad, Mahdieh

    2017-10-02

    The importance of acridine core structure and other heterocycles containing its framework is well known, as they are found in numerous compounds with a variety of biological effects. Pyridine is also an important solvent and heterocyclic nucleus for the design and synthesis of novel molecules with biological properties. It occurs in several natural compounds which are used as a precursor in agrochemicals and pharmaceuticals. The utility of nanostructured metal salts because of their small size and high surface area as catalysts in organic synthesis has drawn special attention due to their better properties such as slower reaction rate, reusability of the catalyst, and higher yields of products compared to the bulk size. Nanosized copper iodide is one reusable Lewis acid catalyst which has revealed several catalytic activities for the synthesis of organic compounds and others. As part of our recent study to develop heterocyclic syntheses using nanostructured catalysts, we now report an efficient and clean synthetic route to 4-arylacridinediones and 6-aryldiindeno[1,2-b:2,1-e]pyridinediones via a condensation reaction catalyzed by CuI nanoparticles under solvent-free conditions. The present work deals with the condensation reaction of aromatic aldehydes, ammonium acetate and active methylene compounds comprising dimedone or 1,3-indanedione in the presence of a catalytic amount of the synthesized CuI nanoparticles could be applied for the solvent-free preparation of 4-arylacridinediones and 6-aryldiindeno[1,2-b:2,1-e]pyridinediones at 70 ˚C within 60 min. A series of 9-aryl-3,3,6,6-tetramethyl-3,4,6,7,9,10-hexahydro-1,8(2H,5H)-acridinediones and 6-aryldiindeno[1,2-b:2,1-e]pyridine-5,7-diones were synthesized in high to excellent yields via a simple one-pot three-component coupling reaction using the synthesized CuI nanoparticles as an efficient and recyclable catalyst. All synthesized compounds were well characterized by their satisfactory elemental analyses, IR, 1H

  20. A solvent free, four-component synthesis and 1,3-dipolar cycloaddition of 4(H)-pyrans with nitrile oxides: synthesis and discovery of antimycobacterial activity of enantiomerically pure 1,2,4-oxadiazoles.

    Science.gov (United States)

    Almansour, Abdulrahman I; Suresh Kumar, Raju; Arumugam, Natarajan; Sriram, Dharmarajan

    2012-07-01

    Four-component reactions of (R)-1-(1-phenylethyl)tetrahydro-4(1H)-pyridinone, aromatic aldehydes and malononitrile in a 1:2:1 molar ratio in the presence of solid sodium ethoxide under solvent free conditions afforded an inseparable mixture of two diastereomeric 4(H)-pyrans in near quantitative yields. These compounds upon 1,3-dipolar cycloaddition with nitrile oxides furnished two enantiomerically pure 1,2,4-oxadiazoles in moderate yields, which were screened for in vitro activity against Mycobacterium tuberculosis H37Rv (MTB) and multi-drug resistant M. tuberculosis (MDR-TB). Among the compounds screened, compound 10h was found to be the most active in vitro with a MIC value of 0.07 and 0.14 μM against MTB and MDR-TB respectively. Copyright © 2012 Elsevier Masson SAS. All rights reserved.

  1. Green synthesis, characterization and catalytic activity of natural bentonite-supported copper nanoparticles for the solvent-free synthesis of 1-substituted 1H-1,2,3,4-tetrazoles and reduction of 4-nitrophenol

    Directory of Open Access Journals (Sweden)

    Akbar Rostami-Vartooni

    2015-12-01

    Full Text Available In this study, Cu nanoparticles were immobilized on the surface of natural bentonite using Thymus vulgaris extract as a reducing and stabilizing agent. The natural bentonite-supported copper nanoparticles (Cu NPs/bentonite were characterized by FTIR spectroscopy, X-ray diffraction (XRD, X-ray fluorescence (XRF, field emission scanning electron microscopy (FE-SEM, energy dispersive X-ray spectroscopy (EDS, transmission electron microscopy (TEM, selected area electron diffraction (SAED and Brunauer–Emmett–Teller (BET analysis. Afterward, the catalytic performance of the prepared catalyst was investigated for the solvent-free synthesis of 1-substituted 1H-1,2,3,4-tetrazoles and reduction of 4-nitrophenol (4-NP in water. It was found that the Cu NPs/bentonite is a highly active and recyclable catalyst for related reactions.

  2. The upside of downsizing: asymmetric trifunctional organocatalysts as small enzyme mimics for cooperative enhancement of both rate and enantioselectivity with regulation.

    Science.gov (United States)

    Liu, Fei

    2013-11-01

    Small molecule organic catalysts (organocatalysts) are widely used in asymmetric catalysis and synthesis. Compared to their enzymatic and transition-metal counterparts, organocatalysts have advantages in catalytic scope and efficiency but are more limited in proficiency. Chiral trifunctional organocatalysts, in which multiple catalytic motifs act cooperatively on a chiral scaffold, are an emerging class of organocatalysts with improved proficiency. Cooperativity design that enables both enantioselectivity and rate enhancement is essential to developing future generations of organocatalysts in biomimetic asymmetric catalysis. © 2013 Wiley Periodicals, Inc.

  3. Fundamental concepts in heterogeneous catalysis

    CERN Document Server

    Norskov, Jens K; Abild-Pedersen, Frank; Bligaard, Thomas

    2014-01-01

    This book is based on a graduate course and suitable as a primer for any newcomer to the field, this book is a detailed introduction to the experimental and computational methods that are used to study how solid surfaces act as catalysts.   Features include:First comprehensive description of modern theory of heterogeneous catalysisBasis for understanding and designing experiments in the field   Allows reader to understand catalyst design principlesIntroduction to important elements of energy transformation technologyTest driven at Stanford University over several semesters

  4. Asymmetrical international attitudes

    NARCIS (Netherlands)

    Van Oudenhoven, JP; Askevis-Leherpeux, F; Hannover, B; Jaarsma, R; Dardenne, B

    2002-01-01

    In general, attitudes towards nations have a fair amount of reciprocity: nations either like each other are relatively indifferent to each other or dislike each other Sometimes, however international attitudes are asymmetrical. In this study, we use social identity theory in order to explain

  5. How Is Nature Asymmetric?

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 7; Issue 6. How Is Nature Asymmetric? - Discrete Symmetries in Particle Physics and their Violation ... Indian Institute of Technology, Chennai. Aligarh Muslim University. University of Rajasthan, Jaipur. Indian Institute of Science, Bangalore 560012, India.

  6. catalysis of chemical processes: particular teaching aspects

    African Journals Online (AJOL)

    IICBA01

    ABSTRACT. The paper is devoted to two main issues of catalysis from the viewpoint of teaching and learning activities. The first part deals with positive catalysis which treats the general features of catalytic processes and textbook imperfections. The second part focuses on decelerating or stopping-down chemical processes ...

  7. DOE Laboratory Catalysis Research Symposium - Abstracts

    Energy Technology Data Exchange (ETDEWEB)

    Dunham, T.

    1999-02-01

    The conference consisted of two sessions with the following subtopics: (1) Heterogeneous Session: Novel Catalytic Materials; Photocatalysis; Novel Processing Conditions; Metals and Sulfides; Nuclear Magnetic Resonance; Metal Oxides and Partial Oxidation; Electrocatalysis; and Automotive Catalysis. (2) Homogeneous Catalysis: H-Transfer and Alkane Functionalization; Biocatalysis; Oxidation and Photocatalysis; and Novel Medical, Methods, and Catalyzed Reactions.

  8. Highly asymmetric rice genomes

    Directory of Open Access Journals (Sweden)

    Chen Jian-Qun

    2007-06-01

    Full Text Available Abstract Background Individuals in the same species are assumed to share the same genomic set. However, it is not unusual to find an orthologous gene only in small subset of the species, and recent genomic studies suggest that structural rearrangements are very frequent between genomes in the same species. Two recently sequenced rice genomes Oryza sativa L. var. Nipponbare and O. sativa L. var. 93-11 provide an opportunity to systematically investigate the extent of the gene repertoire polymorphism, even though the genomic data of 93-11 derived from whole-short-gun sequencing is not yet as complete as that of Nipponbare. Results We compared gene contents and the genomic locations between two rice genomes. Our conservative estimates suggest that at least 10% of the genes in the genomes were either under presence/absence polymorphism (5.2% or asymmetrically located between genomes (4.7%. The proportion of these "asymmetric genes" varied largely among gene groups, in which disease resistance (R genes and the RLK kinase gene group had 11.6 and 7.8 times higher proportion of asymmetric genes than housekeeping genes (Myb and MADS. The significant difference in the proportion of asymmetric genes among gene groups suggests that natural selection is responsible for maintaining genomic asymmetry. On the other hand, the nucleotide diversity in 17 R genes under presence/absence polymorphism was generally low (average nucleotide diversity = 0.0051. Conclusion The genomic symmetry was disrupted by 10% of asymmetric genes, which could cause genetic variation through more unequal crossing over, because these genes had no allelic counterparts to pair and then they were free to pair with homologues at non-allelic loci, during meiosis in heterozygotes. It might be a consequence of diversifying selection that increased the structural divergence among genomes, and of purifying selection that decreased nucleotide divergence in each R gene locus.

  9. "Nanocrystal bilayer for tandem catalysis"

    Energy Technology Data Exchange (ETDEWEB)

    Yamada, Yusuke; Tsung, Chia Kuang; Huang, Wenyu; Huo, Ziyang; E.Habas, Susan E; Soejima, Tetsuro; Aliaga, Cesar E; Samorjai, Gabor A; Yang, Peidong

    2011-01-24

    Supported catalysts are widely used in industry and can be optimized by tuning the composition and interface of the metal nanoparticles and oxide supports. Rational design of metal-metal oxide interfaces in nanostructured catalysts is critical to achieve better reaction activities and selectivities. We introduce here a new class of nanocrystal tandem catalysts that have multiple metal-metal oxide interfaces for the catalysis of sequential reactions. We utilized a nanocrystal bilayer structure formed by assembling platinum and cerium oxide nanocube monolayers of less than 10 nm on a silica substrate. The two distinct metal-metal oxide interfaces, CeO2-Pt and Pt-SiO2, can be used to catalyse two distinct sequential reactions. The CeO2-Pt interface catalysed methanol decomposition to produce CO and H2, which were subsequently used for ethylene hydroformylation catalysed by the nearby Pt-SiO2 interface. Consequently, propanal was produced selectively from methanol and ethylene on the nanocrystal bilayer tandem catalyst. This new concept of nanocrystal tandem catalysis represents a powerful approach towards designing high-performance, multifunctional nanostructured catalysts

  10. Asymmetric extractions in orthodontics

    Directory of Open Access Journals (Sweden)

    Camilo Aquino Melgaço

    2012-04-01

    Full Text Available INTRODUCTION: Extraction decisions are extremely important in during treatment planning. In addition to the extraction decision orthodontists have to choose what tooth should be extracted for the best solution of the problem and the esthetic/functional benefit of the patient. OBJECTIVE: This article aims at reviewing the literature relating the advantages, disadvantages and clinical implications of asymmetric extractions to orthodontics. METHODS: Keywords were selected in English and Portuguese and the EndNote 9 program was used for data base search in PubMed, Web of Science (WSc and LILACS. The selected articles were case reports, original articles and prospective or retrospective case-control studies concerning asymmetrical extractions of permanent teeth for the treatment of malocclusions. CONCLUSION: According to the literature reviewed asymmetric extractions can make some specific treatment mechanics easier. Cases finished with first permanent molars in Class II or III relationship in one or both sides seem not to cause esthetic or functional problems. However, diagnosis knowledge and mechanics control are essential for treatment success.

  11. Asymmetric Evolutionary Games.

    Directory of Open Access Journals (Sweden)

    Alex McAvoy

    2015-08-01

    Full Text Available Evolutionary game theory is a powerful framework for studying evolution in populations of interacting individuals. A common assumption in evolutionary game theory is that interactions are symmetric, which means that the players are distinguished by only their strategies. In nature, however, the microscopic interactions between players are nearly always asymmetric due to environmental effects, differing baseline characteristics, and other possible sources of heterogeneity. To model these phenomena, we introduce into evolutionary game theory two broad classes of asymmetric interactions: ecological and genotypic. Ecological asymmetry results from variation in the environments of the players, while genotypic asymmetry is a consequence of the players having differing baseline genotypes. We develop a theory of these forms of asymmetry for games in structured populations and use the classical social dilemmas, the Prisoner's Dilemma and the Snowdrift Game, for illustrations. Interestingly, asymmetric games reveal essential differences between models of genetic evolution based on reproduction and models of cultural evolution based on imitation that are not apparent in symmetric games.

  12. Asymmetric Evolutionary Games.

    Science.gov (United States)

    McAvoy, Alex; Hauert, Christoph

    2015-08-01

    Evolutionary game theory is a powerful framework for studying evolution in populations of interacting individuals. A common assumption in evolutionary game theory is that interactions are symmetric, which means that the players are distinguished by only their strategies. In nature, however, the microscopic interactions between players are nearly always asymmetric due to environmental effects, differing baseline characteristics, and other possible sources of heterogeneity. To model these phenomena, we introduce into evolutionary game theory two broad classes of asymmetric interactions: ecological and genotypic. Ecological asymmetry results from variation in the environments of the players, while genotypic asymmetry is a consequence of the players having differing baseline genotypes. We develop a theory of these forms of asymmetry for games in structured populations and use the classical social dilemmas, the Prisoner's Dilemma and the Snowdrift Game, for illustrations. Interestingly, asymmetric games reveal essential differences between models of genetic evolution based on reproduction and models of cultural evolution based on imitation that are not apparent in symmetric games.

  13. Palladium catalysis for energy applications

    Energy Technology Data Exchange (ETDEWEB)

    Pfefferle, L. D.; Datye, Abhaya

    2001-03-01

    Palladium (Pd) is an attractive catalyst for a range of new combustion applications comprising primary new technologies for future industrial energy needs, including gas turbine catalytic combustion, auto exhaust catalysts, heating and fuel cells. Pd poses particular challenges because it changes both chemical state and morphology as a function of temperature and reactant environment and those changes result in positive and negative changes in activity. Interactions with the support, additives, water, and contaminants as well as carbon formation have also been observed to affect Pd catalyst performance. This report describes the results of a 3.5 year project that resolves some of the conflicting reports in the literature about the performance of Pd-based catalysis.

  14. Nanocrystal assembly for tandem catalysis

    Science.gov (United States)

    Yang, Peidong; Somorjai, Gabor; Yamada, Yusuke; Tsung, Chia-Kuang; Huang, Wenyu

    2014-10-14

    The present invention provides a nanocrystal tandem catalyst comprising at least two metal-metal oxide interfaces for the catalysis of sequential reactions. One embodiment utilizes a nanocrystal bilayer structure formed by assembling sub-10 nm platinum and cerium oxide nanocube monolayers on a silica substrate. The two distinct metal-metal oxide interfaces, CeO.sub.2--Pt and Pt--SiO.sub.2, can be used to catalyze two distinct sequential reactions. The CeO.sub.2--Pt interface catalyzed methanol decomposition to produce CO and H.sub.2, which were then subsequently used for ethylene hydroformylation catalyzed by the nearby Pt--SiO.sub.2 interface. Consequently, propanal was selectively produced on this nanocrystal bilayer tandem catalyst.

  15. Aminomethylation of enals through carbene and acid cooperative catalysis: concise access to β(2)-amino acids.

    Science.gov (United States)

    Xu, Jianfeng; Chen, Xingkuan; Wang, Ming; Zheng, Pengcheng; Song, Bao-An; Chi, Yonggui Robin

    2015-04-20

    A convergent, organocatalytic asymmetric aminomethylation of α,β-unsaturated aldehydes by N-heterocyclic carbene (NHC) and (in situ generated) Brønsted acid cooperative catalysis is disclosed. The catalytically generated conjugated acid from the base plays dual roles in promoting the formation of azolium enolate intermediate, formaldehyde-derived iminium ion (as an electrophilic reactant), and methanol (as a nucleophilic reactant). This redox-neutral strategy is suitable for the scalable synthesis of enantiomerically enriched β(2) -amino acids bearing various substituents. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Relation between Hydrogen Evolution and Hydrodesulfurization Catalysis

    DEFF Research Database (Denmark)

    Šaric, Manuel; Moses, Poul Georg; Rossmeisl, Jan

    2016-01-01

    A relation between hydrogen evolution and hydrodesulfurization catalysis was found by density functional theory calculations. The hydrogen evolution reaction and the hydrogenation reaction in hydrodesulfurization share hydrogen as a surface intermediate and, thus, have a common elementary step...

  17. Current trends of surface science and catalysis

    CERN Document Server

    Park, Jeong Young

    2014-01-01

    Including detail on applying surface science in renewable energy conversion, this book covers the latest results on model catalysts including single crystals, bridging "materials and pressure gaps", and hot electron flows in heterogeneous catalysis.

  18. Special section on Nano-Catalysis

    CSIR Research Space (South Africa)

    Makgwane, PR

    2013-01-01

    Full Text Available This special issue on nano-catalysis was devoted to the development and application of nanosized structured catalysts materials in various fields such as chemical transformation, environmental cleaning and energy generation supply as a concept tool...

  19. Faraday Discussions meeting Catalysis for Fuels.

    Science.gov (United States)

    Fischer, Nico; Kondrat, Simon A; Shozi, Mzamo

    2017-05-02

    Welcome to Africa was the motto when after more than 100 years the flag ship conference series of the Royal Society of Chemistry, the Faraday Discussions was hosted for the first time on the African Continent. Under the fitting topic 'Catalysis for Fuels' over 120 delegates followed the invitation by the conference chair Prof. Graham Hutchings FRS (Cardiff Catalysis Institute), his organizing committee and the co-organizing DST-NRF Centre of Excellence in Catalysis c*change (). In the presentations of 21 invited speakers and 59 posters, cutting edge research in the field of catalysis for fuels, designing new catalysts for synthetic fuels, hydrocarbon conversion in the production of synthetic fuels and novel photocatalysis was presented over the two-day meeting. The scene was set by the opening lecture of Prof. Enrique Iglesias (UC Berkeley) and wrapped-up with the concluding remarks by Philip Gibson (SASOL).

  20. Loop residues and catalysis in OMP synthase

    DEFF Research Database (Denmark)

    Wang, Gary P.; Hansen, Michael Riis; Grubmeyer, Charles

    2012-01-01

    (preceding paper in this issue, DOI 10.1021/bi300083p)]. The full expression of KIEs by H105A and E107A may result from a less secure closure of the catalytic loop. The lower level of expression of the KIE by K103A suggests that in these mutant proteins the major barrier to catalysis is successful closure...... of the catalytic loop, which when closed, produces rapid and reversible catalysis....

  1. Advancing Sustainable Catalysis with Magnetite Surface ...

    Science.gov (United States)

    This article surveys the recent developments in the synthesis, surface modification, and synthetic applications of magnetitenanoparticles. The emergence of iron(II,III) oxide (triiron tetraoxide or magnetite; Fe3O4, or FeO•Fe2O3) nanoparticles as a sustainable support in heterogeneous catalysis is highlighted. Use of an oxide of earth-abundant iron for various applications in catalysis and environmental remediation.

  2. Lithium-Acetate-Mediated Biginelli One-Pot Multicomponent Synthesis under Solvent-Free Conditions and Cytotoxic Activity against the Human Lung Cancer Cell Line A549 and Breast Cancer Cell Line MCF7

    Directory of Open Access Journals (Sweden)

    Harshita Sachdeva

    2012-01-01

    Full Text Available Various Biginelli compounds (dihydropyrimidinones have been synthesized efficiently and in high yields under mild, solvent-free, and eco-friendly conditions in a one-pot reaction of 1,3-dicarbonyl compounds, aldehydes, and urea/thiourea/acetyl thiourea using lithium-acetate as a novel catalyst without the addition of any proton source. Comparative catalytic efficiency of lithium-acetate and polyphosphoric acid to catalyze Biginelli condensation is also studied under neat conditions. The reaction is carried out in the absence of any solvent and represents an improvement of the classical Biginelli protocol and an advantage in comparison with FeCl3·6H2O, NiCl2·6H2O and CoCl2·6H2O that were used with HCl as a cocatalyst. Compared to classical Biginelli reaction conditions, the present method has advantages of good yields, short reaction times, and experimental simplicity. The obtained products have been identified by spectral (1H NMR and IR data and their melting points. The prepared compounds are evaluated for anticancer activity against two human cancer cell lines (lung cancer cell line A549 and breast cancer cell line MCF7.

  3. Rapid analysis of the essential oils from dried Illicium verum Hook. f. and Zingiber officinale Rosc. by improved solvent-free microwave extraction with three types of microwave-absorption medium.

    Science.gov (United States)

    Wang, Ziming; Wang, Lu; Li, Tiechun; Zhou, Xin; Ding, Lan; Yu, Yong; Yu, Aimin; Zhang, Hanqi

    2006-11-01

    A new method of extracting essential oils from dried plant materials has been studied. By adding a microwave-absorption medium (MAM) to a reactor, solvent-free microwave extraction (SFME) was improved and can be used to extract essential oils from dried plant material without pretreatment. With a microwave irradiation power of 85 W it took only approximately 30 min to extract the essential oils completely. The whole extraction process is simple, rapid, and economical. Three types of MAM, iron carbonyl powder (ICP), graphite powder (GP), and activated carbon powder (ACP), and two types of dried plant material, Illicium verum Hook. f. and Zingiber officinale Rosc., were studied. The results were compared with those obtained by use of conventional SFME, microwave-assisted hydrodistillation (MAHD), and conventional hydrodistillation (HD), and the conclusion drawn was that improved SFME was a feasible means of extracting essential oils from dried plant materials, because there were few differences between the composition of the essential oils extracted by improved SFME and by the other methods.

  4. Catalytic asymmetric fluorinations.

    Science.gov (United States)

    Bobbio, Carla; Gouverneur, Véronique

    2006-06-07

    The appearance of structurally diverse fluorinating reagents displaying a large spectrum of reactivity has been critical to the development of the catalytic asymmetric fluorination processes known to date. In this article, we discuss how this area of research emerged and which strategies have allowed for the successful development of both nucleophilic and electrophilic catalytic enantioselective fluorinations. We also present the fundamental understanding of catalytic activity and enantioselectivity for the most efficient processes and highlight the first synthetic application with the preparation of a complex fluorinated target.

  5. Asymmetric synthesis v.4

    CERN Document Server

    Morrison, James

    1984-01-01

    Asymmetric Synthesis, Volume 4: The Chiral Carbon Pool and Chiral Sulfur, Nitrogen, Phosphorus, and Silicon Centers describes the practical methods of obtaining chiral fragments. Divided into five chapters, this book specifically examines initial chiral transmission and extension. The opening chapter describes the so-called chiral carbon pool, the readily available chiral carbon fragments used as building blocks in synthesis. This chapter also provides a list of 375 chiral building blocks, along with their commercial sources, approximate prices, and methods of synthesis. Schemes involving

  6. Asymmetric Organocatalytic Cycloadditions

    DEFF Research Database (Denmark)

    Mose, Rasmus

    2016-01-01

    were pioneered by Otto Paul Hermann Diels and Kurt Alder who discovered what later became known as the Diels Alder reaction. The Diels Alder reaction is a [4+2] cycloaddition in which a π4 component reacts with a π2 component via a cyclic transition state to generate a 6 membered ring. This reaction...... undergo cascade reactions with different electron deficient dienophiles in Diels Alder – nucleophilic ring closing reactions. This methodology opens up for the direct asymmetric formation of hydroisochromenes and hydroisoquinolines which may possess interesting biological activities. It is also...

  7. Constructing Asymmetric Polyion Complex Vesicles via Template Assembling Strategy: Formulation Control and Tunable Permeability

    Directory of Open Access Journals (Sweden)

    Junbo Li

    2017-11-01

    Full Text Available A strategy for constructing polyion complex vesicles (PICsomes with asymmetric structure is described. Poly(methylacrylic acid-block-poly(N-isopropylacrylamide modified gold nanoparticles (PMAA-b-PNIPAm-@-Au NPs were prepared and then assembled with poly(ethylene glycol-block-poly[1-methyl-3-(2-methacryloyloxy propylimidazolium bromine] (PEG-b-PMMPImB via polyion complex of PMMA and PMMPImB. After removing the Au NPs template, asymmetric PICsomes composed of a PNIPAm inner-shell, PIC wall, and PEG outer-corona were obtained. These PICsomes have low protein absorption and thermally tunable permeability, provided by the PEG outer-corona and the PNIPAm inner-shell, respectively. Moreover, PICsome size can be tailored by using templates of predetermined sizes. This novel strategy for constructing asymmetric PICsomes with well-defined properties and controllable size is valuable for applications such as drug delivery, catalysis and monitoring of chemical reactions, and biomimetics.

  8. Asymmetric inclusion process.

    Science.gov (United States)

    Reuveni, Shlomi; Eliazar, Iddo; Yechiali, Uri

    2011-10-01

    We introduce and explore the asymmetric inclusion process (ASIP), an exactly solvable bosonic counterpart of the fermionic asymmetric exclusion process (ASEP). In both processes, random events cause particles to propagate unidirectionally along a one-dimensional lattice of n sites. In the ASEP, particles are subject to exclusion interactions, whereas in the ASIP, particles are subject to inclusion interactions that coalesce them into inseparable clusters. We study the dynamics of the ASIP, derive evolution equations for the mean and probability generating function (PGF) of the sites' occupancy vector, obtain explicit results for the above mean at steady state, and describe an iterative scheme for the computation of the PGF at steady state. We further obtain explicit results for the load distribution in steady state, with the load being the total number of particles present in all lattice sites. Finally, we address the problem of load optimization, and solve it under various criteria. The ASIP model establishes bridges between statistical physics and queueing theory as it represents a tandem array of queueing systems with (unlimited) batch service, and a tandem array of growth-collapse processes.

  9. Kinetics of transesterification of palm oil and dimethyl carbonate for biodiesel production at the catalysis of heterogeneous base catalyst.

    Science.gov (United States)

    Zhang, Liping; Sheng, Boyang; Xin, Zhong; Liu, Qun; Sun, Shuzhen

    2010-11-01

    The transesterification of palm oil with dimethyl carbonate (DMC) for preparing biodiesel has been studied in solvent-free system at the catalysis of potassium hydroxide (KOH) as heterogeneous catalyst. Fatty acid methyl esters (FAMEs) were analyzed by GC with internal standard method. The effects of reaction conditions (molar ratio of DMC and palm oil, catalyst amount and time) on FAMEs yield were investigated. The highest FAMEs yield could reach 96.2% at refluxing temperature for 8h with molar ratio of DMC and oil 9:1 and 8.5% KOH (based on oil weight). Kinetics of the KOH-catalyzed transesterification of palm oil and DMC was researched over a temperature range of 65-75 degrees C. A pseudo first-order model was proposed. The activation energy (E(a)) was 79.1 kJ mo1(-1) and the pre-exponential factor (k(o)) was 1.26 x 10(9) min(-1) from Arrhenius equation. Further, a plausible reaction mechanism for the catalytic process with DMC as acyl acceptor was proposed. Copyright 2010 Elsevier Ltd. All rights reserved.

  10. Specific acid catalysis and Lewis acid catalysis of Diels-Alder reactions in aqueous media

    NARCIS (Netherlands)

    Mubofu, E.B.; Engberts, J.B.F.N.

    A comparative study of specific acid catalysis and Lewis acid catalysis of Diells-Alder reactions between dienophiles (1, 4 and 6) and cyclopentadiene (2) in water and mixed aqueous media is reported. The reactions were performed in water with copper(II) nitrate as the Lewis acid catalyst whereas

  11. Specific acid catalysis and Lewis acid catalysis of Diels–Alder reactions in aqueous media

    NARCIS (Netherlands)

    Mubofu, Egid B.; Engberts, Jan B.F.N.

    2004-01-01

    A comparative study of specific acid catalysis and Lewis acid catalysis of Diels–Alder reactions between dienophiles (1, 4 and 6) and cyclopentadiene (2) in water and mixed aqueous media is reported. The reactions were performed in water with copper(II) nitrate as the Lewis acid catalyst whereas

  12. ISOTOPE METHODS IN HOMOGENEOUS CATALYSIS.

    Energy Technology Data Exchange (ETDEWEB)

    BULLOCK,R.M.; BENDER,B.R.

    2000-12-01

    The use of isotope labels has had a fundamentally important role in the determination of mechanisms of homogeneously catalyzed reactions. Mechanistic data is valuable since it can assist in the design and rational improvement of homogeneous catalysts. There are several ways to use isotopes in mechanistic chemistry. Isotopes can be introduced into controlled experiments and followed where they go or don't go; in this way, Libby, Calvin, Taube and others used isotopes to elucidate mechanistic pathways for very different, yet important chemistries. Another important isotope method is the study of kinetic isotope effects (KIEs) and equilibrium isotope effect (EIEs). Here the mere observation of where a label winds up is no longer enough - what matters is how much slower (or faster) a labeled molecule reacts than the unlabeled material. The most careti studies essentially involve the measurement of isotope fractionation between a reference ground state and the transition state. Thus kinetic isotope effects provide unique data unavailable from other methods, since information about the transition state of a reaction is obtained. Because getting an experimental glimpse of transition states is really tantamount to understanding catalysis, kinetic isotope effects are very powerful.

  13. Advanced Resources for Catalysis Science; Recommendations for a National Catalysis Research Institute

    Energy Technology Data Exchange (ETDEWEB)

    Peden, Charles HF.; Ray, Douglas

    2005-10-05

    Catalysis is one of the most valuable contributors to our economy and historically an area where the United States has enjoyed, but is now losing, international leadership. While other countries are stepping up their work in this area, support for advanced catalysis research and development in the U.S. has diminished. Yet, more than ever, innovative and improved catalyst technologies are imperative for new energy production processes to ease our dependence on imported resources, for new energy-efficient and environmentally benign chemical production processes, and for new emission reduction technologies to minimize the environmental impact of an active and growing economy. Addressing growing concerns about the future direction of U.S. catalysis science, experts from the catalysis community met at a workshop to determine and recommend advanced resources needed to address the grand challenges for catalysis research and development. The workshop's primary conclusion: To recapture our position as the leader in catalysis innovation and practice, and promote crucial breakthroughs, the U.S. must establish one or more well-funded and well-equipped National Catalysis Research Institutes competitively selected, centered in the national laboratories and, by charter, networked to other national laboratories, universities, and industry. The Institute(s) will be the center of a national collaboratory that gives catalysis researchers access to the most advanced techniques available in the scientific enterprise. The importance of catalysis to our energy, economic, and environmental security cannot be overemphasized. Catalysis is a vital part of our core industrial infrastructure, as it is integral to chemical processing and petroleum refining, and is critical to proposed advances needed to secure a sustainable energy future. Advances in catalysis could reduce our need for foreign oil by making better use of domestic carbon resources, for example, allowing cost-effective and

  14. Enantioselective solvent-free Robinson annulation reactions

    Indian Academy of Sciences (India)

    Unknown

    initial formation of an acid-base complex followed by a Michael reaction and then an enantioselective cyclization. Such enantioselective cyclizations probably occur on the surface of S-proline crystals. Keywords. Enantioselective annulation; cyclization; S-proline; S-phenylalanine; d-camphorsulphonic acid. 1. Introduction.

  15. SHORT COMMUNICATION A SOLVENT FREE AND SELECTIVE ...

    African Journals Online (AJOL)

    Preferred Customer

    dimethoxytrityl (DMT) group is an exceedingly useful control element in organic synthesis [1, 13]. In a study on the selective protection of hydroxyl groups in ribonucleosides, 4,4´-dimethoxytrityl chloride reacts almost exclusively with the primary 5´-hydroxyl ...

  16. Enantioselective solvent-free Robinson annulation reactions

    Indian Academy of Sciences (India)

    The enantioselective cyclization of the prochiral cyclic substrates 1 to 7 and 26, can be carried out in the neat using -proline as catalyst. The substrates 18 to 22 and 27 could not be cyclized with S-proline but could be cyclized with a mixture of -phenylalanine and -camphorsulphonic acid. The enantioselective ...

  17. SHORT COMMUNICATION A SOLVENT FREE AND SELECTIVE ...

    African Journals Online (AJOL)

    Preferred Customer

    1Department of Chemistry and Chemical Engineering, Faculty of Material and Chemical. Engineering ... microwave irradiation in organic reactions is rapidly increasing, because of its short reaction times and .... a mild and efficient method for hydroxyl group protection by reaction of 1°, 2° and 3° alcohols with trityl chloride ...

  18. SHORT COMMUNICATION SOLVENT FREE PREPARATION OF N ...

    African Journals Online (AJOL)

    Preferred Customer

    vibration, also referred to as the amide II bands and are characterized to primary and secondary amide [16]. The bands at 1392 cm-1 are assigned to the O-H bending of the carboxylic acid. The. CO stretching at 1317 cm-1 are those associated with the OC-OH carboxylic group. The stretching absorption at 1088 cm-1 has ...

  19. Solvent-Free Synthesis of Chalcones

    Science.gov (United States)

    Palleros, Daniel R.

    2004-01-01

    The synthesis of twenty different chalcones in the absence of solvent is presented. The results indicated that out of the twenty different chalcones investigated seventeen can be obtained in a matter of minutes by mixing the corresponding benzaldehyde and acetophenone in the presence of solid NaOH in a mortar with pestle.

  20. Symmetric Decomposition of Asymmetric Games.

    Science.gov (United States)

    Tuyls, Karl; Pérolat, Julien; Lanctot, Marc; Ostrovski, Georg; Savani, Rahul; Leibo, Joel Z; Ord, Toby; Graepel, Thore; Legg, Shane

    2018-01-17

    We introduce new theoretical insights into two-population asymmetric games allowing for an elegant symmetric decomposition into two single population symmetric games. Specifically, we show how an asymmetric bimatrix game (A,B) can be decomposed into its symmetric counterparts by envisioning and investigating the payoff tables (A and B) that constitute the asymmetric game, as two independent, single population, symmetric games. We reveal several surprising formal relationships between an asymmetric two-population game and its symmetric single population counterparts, which facilitate a convenient analysis of the original asymmetric game due to the dimensionality reduction of the decomposition. The main finding reveals that if (x,y) is a Nash equilibrium of an asymmetric game (A,B), this implies that y is a Nash equilibrium of the symmetric counterpart game determined by payoff table A, and x is a Nash equilibrium of the symmetric counterpart game determined by payoff table B. Also the reverse holds and combinations of Nash equilibria of the counterpart games form Nash equilibria of the asymmetric game. We illustrate how these formal relationships aid in identifying and analysing the Nash structure of asymmetric games, by examining the evolutionary dynamics of the simpler counterpart games in several canonical examples.

  1. Minimal asymmetric dark matter

    Directory of Open Access Journals (Sweden)

    Sofiane M. Boucenna

    2015-09-01

    Full Text Available In the early Universe, any particle carrying a conserved quantum number and in chemical equilibrium with the thermal bath will unavoidably inherit a particle–antiparticle asymmetry. A new particle of this type, if stable, would represent a candidate for asymmetric dark matter (DM with an asymmetry directly related to the baryon asymmetry. We study this possibility for a minimal DM sector constituted by just one (generic SU(2L multiplet χ carrying hypercharge, assuming that at temperatures above the electroweak phase transition an effective operator enforces chemical equilibrium between χ and the Higgs boson. We argue that limits from DM direct detection searches severely constrain this scenario, leaving as the only possibilities scalar or fermion multiplets with hypercharge y=1, preferentially quintuplets or larger SU(2 representations, and with a mass in the few TeV range.

  2. Asymmetric black dyonic holes

    Directory of Open Access Journals (Sweden)

    I. Cabrera-Munguia

    2015-04-01

    Full Text Available A 6-parametric asymptotically flat exact solution, describing a two-body system of asymmetric black dyons, is studied. The system consists of two unequal counterrotating Kerr–Newman black holes, endowed with electric and magnetic charges which are equal but opposite in sign, separated by a massless strut. The Smarr formula is generalized in order to take into account their contribution to the mass. The expressions for the horizon half-length parameters σ1 and σ2, as functions of the Komar parameters and of the coordinate distance, are displayed, and the thermodynamic properties of the two-body system are studied. Furthermore, the seven physical parameters satisfy a simple algebraic relation which can be understood as a dynamical scenario, in which the physical properties of one body are affected by the ones of the other body.

  3. Asymmetric Realized Volatility Risk

    Directory of Open Access Journals (Sweden)

    David E. Allen

    2014-06-01

    Full Text Available In this paper, we document that realized variation measures constructed from high-frequency returns reveal a large degree of volatility risk in stock and index returns, where we characterize volatility risk by the extent to which forecasting errors in realized volatility are substantive. Even though returns standardized by ex post quadratic variation measures are nearly Gaussian, this unpredictability brings considerably more uncertainty to the empirically relevant ex ante distribution of returns. Explicitly modeling this volatility risk is fundamental. We propose a dually asymmetric realized volatility model, which incorporates the fact that realized volatility series are systematically more volatile in high volatility periods. Returns in this framework display time varying volatility, skewness and kurtosis. We provide a detailed account of the empirical advantages of the model using data on the S&P 500 index and eight other indexes and stocks.

  4. Operando chemistry of catalyst surfaces during catalysis.

    Science.gov (United States)

    Dou, Jian; Sun, Zaicheng; Opalade, Adedamola A; Wang, Nan; Fu, Wensheng; Tao, Franklin Feng

    2017-04-03

    Chemistry of a catalyst surface during catalysis is crucial for a fundamental understanding of mechanism of a catalytic reaction performed on the catalyst in the gas or liquid phase. Due to the pressure- or molecular density-dependent entropy contribution of gas or liquid phase of the reactants and the potential formation of a catalyst surface during catalysis different from that observed in an ex situ condition, the characterization of the surface of a catalyst under reaction conditions and during catalysis can be significant and even necessary for understanding the catalytic mechanism at a molecular level. Electron-based analytical techniques are challenging for studying catalyst nanoparticles in the gas or liquid phase although they are necessary techniques to employ. Instrumentation and further development of these electron-based techniques have now made in situ/operando studies of catalysts possible. New insights into the chemistry and structure of catalyst nanoparticles have been uncovered over the last decades. Herein, the origin of the differences between ex situ and in situ/operando studies of catalysts, and the technical challenges faced as well as the corresponding instrumentation and innovations utilized for characterizing catalysts under reaction conditions and during catalysis, are discussed. The restructuring of catalyst surfaces driven by the pressure of reactant(s) around a catalyst, restructuring in reactant(s) driven by reaction temperature and restructuring during catalysis are also reviewed herein. The remaining challenges and possible solutions are briefly discussed.

  5. Application of Artificial Neural Networks for Catalysis: A Review

    National Research Council Canada - National Science Library

    Hao Li; Zhien Zhang; Zhijian Liu

    2017-01-01

    .... However, their applications for catalysis were not well-studied until recent decades. In this review, we aim to summarize the applications of ANNs for catalysis research reported in the literature...

  6. Green chemistry by nano-catalysis

    KAUST Repository

    Polshettiwar, Vivek

    2010-01-01

    Nano-materials are important in many diverse areas, from basic research to various applications in electronics, biochemical sensors, catalysis and energy. They have emerged as sustainable alternatives to conventional materials, as robust high surface area heterogeneous catalysts and catalyst supports. The nano-sized particles increase the exposed surface area of the active component of the catalyst, thereby enhancing the contact between reactants and catalyst dramatically and mimicking the homogeneous catalysts. This review focuses on the use of nano-catalysis for green chemistry development including the strategy of using microwave heating with nano-catalysis in benign aqueous reaction media which offers an extraordinary synergistic effect with greater potential than these three components in isolation. To illustrate the proof-of-concept of this "green and sustainable" approach, representative examples are discussed in this article. © 2010 The Royal Society of Chemistry.

  7. Progress towards bioorthogonal catalysis with organometallic compounds.

    Science.gov (United States)

    Völker, Timo; Dempwolff, Felix; Graumann, Peter L; Meggers, Eric

    2014-09-22

    The catalysis of bioorthogonal transformations inside living organisms is a formidable challenge--yet bears great potential for future applications in chemical biology and medicinal chemistry. We herein disclose highly active organometallic ruthenium complexes for bioorthogonal catalysis under biologically relevant conditions and inside living cells. The catalysts uncage allyl carbamate protected amines with unprecedented high turnover numbers of up to 270 cycles in the presence of water, air, and millimolar concentrations of thiols. By live-cell imaging of HeLa cells and with the aid of a caged fluorescent probe we could reveal a rapid development of intense fluorescence within the cellular cytoplasm and therefore support the proposed bioorthogonality of the catalysts. In addition, to illustrate the manifold applications of bioorthogonal catalysis, we developed a method for catalytic in-cell activation of a caged anticancer drug, which efficiently induced apoptosis in HeLa cells. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Request for Symposia Support: Advances in Olefin Polymerization Catalysis

    Science.gov (United States)

    2014-11-24

    included, but were not limited to, heterogeneous catalysis , homogeneous catalysis , advances in catalyst activation, methods for polymer topological...SECURITY CLASSIFICATION OF: This Advances in Olefin Polymerization Catalysis symposium was held at the 247th ACS National Meeting and Exposition...March 19, 2014 in Dallas, Texas and consisted of twelve (12) invited/contributed talks. The hosting ACS division was the Division of Catalysis Science

  9. Next-Generation Catalysis for Renewables: Combining Enzymatic with Inorganic Heterogeneous Catalysis for Bulk Chemical Production

    DEFF Research Database (Denmark)

    Vennestrøm, Peter Nicolai Ravnborg; Christensen, C.H.; Pedersen, S.

    2010-01-01

    chemical platform under different conditions than those conventionally employed. Indeed, new process and catalyst concepts need to be established. Both enzymatic catalysis (biocatalysis) and heterogeneous inorganic catalysis are likely to play a major role and, potentially, be combined. One type...... of combination involves one-pot cascade catalysis with active sites from bio- and inorganic catalysts. In this article the emphasis is placed specifically on oxidase systems involving the coproduction of hydrogen peroxide, which can be used to create new in situ collaborative oxidation reactions for bulk...

  10. Ionic Liquids: Synthesis and Applications in Catalysis

    Directory of Open Access Journals (Sweden)

    Rajni Ratti

    2014-01-01

    Full Text Available Ionic liquids have emerged as an environmentally friendly alternative to the volatile organic solvents. Being designer solvents, they can be modulated to suit the reaction conditions, therefore earning the name “task specific ionic liquids.” Though primarily used as solvents, they are now finding applications in various fields like catalysis, electrochemistry, spectroscopy, and material science to mention a few. The present review is aimed at exploring the applications of ionic liquids in catalysis as acid, base, and organocatalysts and as soluble supports for catalysts.

  11. RNA catalysis and the origins of life

    Science.gov (United States)

    Orgel, Leslie E.

    1986-01-01

    The role of RNA catalysis in the origins of life is considered in connection with the discovery of riboszymes, which are RNA molecules that catalyze sequence-specific hydrolysis and transesterification reactions of RNA substrates. Due to this discovery, theories positing protein-free replication as preceding the appearance of the genetic code are more plausible. The scope of RNA catalysis in biology and chemistry is discussed, and it is noted that the development of methods to select (or predict) RNA sequences with preassigned catalytic functions would be a major contribution to the study of life's origins.

  12. A molecular view of heterogeneous catalysis

    DEFF Research Database (Denmark)

    Christensen, Claus H.; Nørskov, Jens Kehlet

    2008-01-01

    The establishment of a molecular view of heterogeneous catalysis has been hampered for a number of reasons. There are, however, recent developments, which show that we are now on the way towards reaching a molecular-scale picture of the way solids work as catalysts. By a combination of new...... by enabling a rational design of new catalysts. We illustrate this important development in heterogeneous catalysis by highlighting recent examples of catalyst systems for which it has been possible to achieve such a detailed understanding. In particular, we emphasize examples where this progress has made...

  13. Keynotes in energy-related catalysis

    CERN Document Server

    Kaliaguine, S

    2011-01-01

    Catalysis by solid acids, which includes (modified) zeolites, is of special relevance to energy applications. Acid catalysis is highly important in modern petroleum refining operations - large-scale processes such as fluid catalytic cracking, catalytic reforming, alkylation and olefin oligomerization rely on the transformation of hydrocarbons by acid catalysts. (Modified) zeolites are therefore essential for the improvement of existing processes and for technical innovations in the conversion of crude. There can be little doubt that zeolite-based catalysts will play a major role in the futu

  14. Catalysis by nonmetals rules for catalyst selection

    CERN Document Server

    Krylov, Oleg V

    1970-01-01

    Catalysis by Non-metals: Rules of Catalyst Selection presents the development of scientific principles for the collection of catalysts. It discusses the investigation of the mechanism of chemosorption and catalysis. It addresses a series of properties of solid with catalytic activity. Some of the topics covered in the book are the properties of a solid and catalytic activity in oxidation-reduction reactions; the difference of electronegativities and the effective charges of atoms; the role of d-electrons in the catalytic properties of a solid; the color of solids; and proton-acid and proton-ba

  15. Heterogeneous catalysis at nanoscale for energy applications

    CERN Document Server

    Tao, Franklin (Feng); Kamat, Prashant V

    2015-01-01

    This book presents both the fundamentals concepts and latest achievements of a field that is growing in importance since it represents a possible solution for global energy problems.  It focuses on an atomic-level understanding of heterogeneous catalysis involved in important energy conversion processes. It presents a concise picture for the entire area of heterogeneous catalysis with vision at the atomic- and nano- scales, from synthesis, ex-situ and in-situ characterization, catalytic activity and selectivity, to mechanistic understanding based on experimental exploration and theoretical si

  16. Intermetallic: A Pseudoelement for Catalysis.

    Science.gov (United States)

    Tsai, A P; Kameoka, S; Nozawa, K; Shimoda, M; Ishii, Y

    2017-12-19

    A clear correlation between electronic structure and CO2 selectivity for steam reforming of methanol (SRM) was obtained with PdZn, PtZn, NiZn, and PdCd intermetallics on the basis of experiments and calculations. In order to rule out the effects of oxide supports, the intermetallic powders were simply prepared by alloying in an arc furnace followed by crushing in a mortar. PdZn and PdCd exhibit valence electronic densities of states similar to that of Cu and significant chemical shifts (larger than 1 eV) of Pd 3d states with respect to pure Pd, as verified by high-resolution hard X-ray photoelectron spectroscopy (HXPS) measurements and density functional theory (DFT) calculations. Consequently, they show the similar high selectivity of CO2 for the SRM reaction. However, this is not the case for PtZn and NiZn because of the slight differences in their valence electronic structures from that of PdZn. The interval between the Fermi level and the top of the d band is closely related to the selectivity of CO2 for the SRM: the larger the interval is, the higher is the selectivity of CO2. According to DFT calculations for bulk PdZn performed by Chen et al. ( Phys. Rev. B 2003 , 68 , 075417 ), the (111) and (100) surfaces exposing Zn and Pd in an equimolar ratio are more stable than the (001) or (110) surfaces terminated by alternative Zn or Pd layers. First-principles slab calculations for PdZn, PtZn, and NiZn show that bond breaking on the surface leads to a reduction in the d bandwidth but that the d band for stable (111) or (100) surfaces remains essentially unchanged from that of the bulk. It is intriguing that PdZn and PdCd do not contain Cu but show similar valence electronic structure and catalytic selectivity, and hence, a concept is proposed where PdZn and PdCd are regarded as pseudoelements of Cu. The basis of this concept is like electronic structure, like catalysis, which has been demonstrated by experiments and calculations. This is a logical way to enable us

  17. A new oxovanadium(IV) complex containing an O,N-bidentate Schiff base ligand: Synthesis at ambient temperature, characterization, crystal structure and catalytic performance in selective oxidation of sulfides to sulfones using H2O2 under solvent-free conditions

    Science.gov (United States)

    Menati, Saeid; Rudbari, Hadi Amiri; Khorshidifard, Mahsa; Jalilian, Fariba

    2016-01-01

    A new bidentate ON Schiff base ligand, HL, was synthesized by simple condensation reaction of isopropylamine and salicylaldehyde. Then by reaction of HL and VO(acac)2 in the ratio of 2:1 at ambient temperature, a new oxovanadium(IV) Schiff base complex, VOL2, was synthesized. The Schiff base ligand and its oxovanadium(IV) complex were characterized by elemental analyses, FT-IR, 1H NMR, 13C NMR and UV-visible spectroscopies. The crystal structure of oxovanadium(IV) complex, VOL2, was also determined by single crystal X-ray analysis. The vanadium center in this structure is coordinated to two bidentate Schiff base ligands with the two nitrogen and two phenolate oxygen atoms in equatorial positions and one oxo oxygen in the axial position to complete the distorted trigonal bipyramidal N2O3 coordination sphere. Catalytic performance of the VOL2 complex was studied in the selective oxidation of thioanisole with the green oxidant 35% aqueous H2O2 under solvent-free conditions and under organic solvents (EtOH, CHCl3, CH2Cl2, DMF, CH3CN, EtOAc) as a model. Due to better catalytic performance of the VOL2 complex under solvent-free conditions, this complex used for the oxidation of the different sulfides to the corresponding sulfones under solvent-free conditions. The use of hydrogen peroxide as oxidant and the absence of solvent makes these reactions interesting from environmental and economic points of view.

  18. Asymmetric bifurcated halogen bonds.

    Science.gov (United States)

    Novák, Martin; Foroutan-Nejad, Cina; Marek, Radek

    2015-03-07

    Halogen bonding (XB) is being extensively explored for its potential use in advanced materials and drug design. Despite significant progress in describing this interaction by theoretical and experimental methods, the chemical nature remains somewhat elusive, and it seems to vary with the selected system. In this work we present a detailed DFT analysis of three-center asymmetric halogen bond (XB) formed between dihalogen molecules and variously 4-substituted 1,2-dimethoxybenzene. The energy decomposition, orbital, and electron density analyses suggest that the contribution of electrostatic stabilization is comparable with that of non-electrostatic factors. Both terms increase parallel with increasing negative charge of the electron donor molecule in our model systems. Depending on the orientation of the dihalogen molecules, this bifurcated interaction may be classified as 'σ-hole - lone pair' or 'σ-hole - π' halogen bonds. Arrangement of the XB investigated here deviates significantly from a recent IUPAC definition of XB and, in analogy to the hydrogen bonding, the term bifurcated halogen bond (BXB) seems to be appropriate for this type of interaction.

  19. Magnetically Modified Asymmetric Supercapacitors Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This Small Business Innovation Research Phase I project is for the development of an asymmetric supercapacitor that will have improved energy density and cycle life....

  20. Imidazole-based Potential Bi- and Tridentate Nitrogen Ligands: Synthesis, Characterization and Application in Asymmetric Catalysis

    Directory of Open Access Journals (Sweden)

    Jiří Kulhánek

    2008-09-01

    Full Text Available Twelve new imidazole-based potential bi- and tridentate ligands were synthesized and characterized. Whereas in the first series the α-amino acid and imidazole moieties were linked by an amino bond, in the second series the tridentate ligands, containing two imidazole groups, were separated by an amide bond. The first series was obtained by the reductive amination of 2-phenylimidazole-4-carboxaldehyde with α-amino acid esters. The tridentate ligands were prepared from 2-phenylimidazole-4-carboxylic acid and chiral amines. In the Henry reaction, the amines were revealed as a more reactive species than the less nucleophilic amides, however the enantiomeric excesses were generally poor.

  1. Primary amine/CSA ion pair: A powerful catalytic system for the asymmetric enamine catalysis

    KAUST Repository

    Liu, Chen

    2011-05-20

    A novel ion pair catalyst containing a chiral counteranion can be readily derived by simply mixing cinchona alkaloid-derived diamine with chiral camphorsulfonic acid (CSA). A mixture of 9-amino(9-deoxy)epi-quinine 8 and (-)-CSA was found to be the best catalyst with matching chirality, enabling the direct amination of α-branched aldehydes to proceed in quantitative yields and with nearly perfect enantioselectivities. A 0.5 mol % catalyst loading was sufficient to catalyze the reaction, and a gram scale enantioselective synthesis of biologically important α-methyl phenylglycine has been successfully demonstrated. © 2011 American Chemical Society.

  2. Asymmetric Mannich synthesis of α-amino esters by anion-binding catalysis.

    Science.gov (United States)

    Wasa, Masayuki; Liu, Richard Y; Roche, Stéphane P; Jacobsen, Eric N

    2014-09-17

    We report a scalable, one-pot Mannich route to enantioenriched α-amino esters by direct reaction of α-chloroglycine ester as a practical imino ester surrogate. The reaction is promoted by a chiral aminothiourea, which is proposed to operate cooperatively by generating an iminium ion by chloride abstraction and an enolate by deprotonation, followed by highly stereoselective C-C bond formation between both reactive intermediates associated non-covalently within the catalyst framework.

  3. Asymmetric catalysis at a distance: catalytic, site-selective phosphorylation of teicoplanin.

    Science.gov (United States)

    Han, Sunkyu; Miller, Scott J

    2013-08-21

    We report three distinct, peptide-based catalysts that enable site-selective phosphorylation of three distinct hydroxyl groups within the complex glycopeptide antibiotic teicoplanin A2-2. Two of the catalysts are based on a design that capitalizes on a catalyst-substrate interaction that mimics the biological mechanism of action for teicoplanin. These catalysts are based on a DXaa-DXaa peptide motif that is known to target the teicoplanin structure in a specific manner. The third was identified through evaluation of a set of catalysts that had been developed for historically distinct projects. Each catalyst contains additional functionality designed to dispose a catalytic moiety (a nucleophilic alkylimidazole) at a different region of the glycopeptide structure. A combination of mass spectrometry and 2D-NMR spectroscopy allowed structural assignment of the distinct phosphorylated teicoplanin derivatives. Mechanistic studies are also reported that support the hypotheses that led to the discovery of the catalysts. In this manner, small molecule catalysts have been achieved that allow rational, catalytic control over reactions at sites that are separated by 11.6, 16.5, and nearly 17.7 Å, based on the X-ray crystal structure of teicoplanin A2-2. Finally, we report the biological activity of the new phosphorylated teicoplanin analogs and compare the results to the natural product itself.

  4. DNA-based asymmetric catalysis : Sequence-dependent rate acceleration and enantioselectivity

    NARCIS (Netherlands)

    Boersma, Arnold J.; Klijn, Jaap E.; Feringa, Ben L.; Roelfes, Gerard

    2008-01-01

    This study shows that the role of DNA in the DNA-based enantioselective Diels-Alder reaction of azachalcone with cyclopentadiene is not limited to that of a chiral scaffold. DNA in combination with the copper complex of 4,4'-dimethyl-2,2'-bipyridine (Cu-L1) gives rise to a rate acceleration of up to

  5. Asymmetric catalysis and molecular recognition using different platforms: homogeneous systems, functionalized polymers and magnetic nanoparticles

    OpenAIRE

    Mendoza Muniz, Carolina

    2011-01-01

    In this work three new di-platinum(II) thiolato-bridged complexes [(dppp)Pt{-S(CH2)nNHC(=O)NHR}]2(OTf)2 (n = 2, 3; R = Et, Ph) have been synthesized, fully characterized and studied as synthetic receptors for anionic species. The binding of anions has been quantitatively determined by 1H NMR spectroscopy and in a qualitative fashion by an indicator displacement assays. These studies have shown the receptors to be selective for H2PO4-. Cobalt and magnetite magnetic nanoparticles have been pr...

  6. Homogeneous and heterogeneous catalysis production and ...

    African Journals Online (AJOL)

    Temperature and methanol characteristics (oil molar ratio; catalyst type, concentration and agitation) controlled the ester convers-ion. ... The fuel properties of biodiesels and blends were analysed quantitati-vely, and the biodiesel produced by homogeneous catalysis compared favourably with conventional diesel fuel.

  7. µ-reactors for Heterogeneous Catalysis

    DEFF Research Database (Denmark)

    Jensen, Robert

    is described in detail. Since heating and temperature measurement is an extremely important point in heterogeneous catalysis an entire chapter is dedicated to this subject. Three different types of heaters have been implemented and tested both for repeatability and homogeneity of the heating as well...

  8. Supported ionic liquid-phase (SILP) catalysis

    DEFF Research Database (Denmark)

    Riisager, Anders; Fehrmann, Rasmus; Wasserscheid, P.

    2005-01-01

    The concept of supported ionic liquid-phase (SILP) catalysis has been demonstrated for gas- and liquid-phase continuous fixed-bed reactions using rhodium phosphine catalyzed hydroformylation of propene and 1-octene as examples. The nature of the support had important influence on both the catalytic...

  9. Diffusion and Surface Reaction in Heterogeneous Catalysis

    Science.gov (United States)

    Baiker, A.; Richarz, W.

    1978-01-01

    Ethylene hydrogenation on a platinum catalyst, electrolytically applied to a tube wall, is a good system for the study of the interactions between diffusion and surface reaction in heterogeneous catalysis. Theoretical background, apparatus, procedure, and student performance of this experiment are discussed. (BB)

  10. Confined catalysis under two-dimensional materials

    Science.gov (United States)

    Li, Haobo; Xiao, Jianping; Bao, Xinhe

    2017-01-01

    Confined microenvironments formed in heterogeneous catalysts have recently been recognized as equally important as catalytically active sites. Understanding the fundamentals of confined catalysis has become an important topic in heterogeneous catalysis. Well-defined 2D space between a catalyst surface and a 2D material overlayer provides an ideal microenvironment to explore the confined catalysis experimentally and theoretically. Using density functional theory calculations, we reveal that adsorption of atoms and molecules on a Pt(111) surface always has been weakened under monolayer graphene, which is attributed to the geometric constraint and confinement field in the 2D space between the graphene overlayer and the Pt(111) surface. A similar result has been found on Pt(110) and Pt(100) surfaces covered with graphene. The microenvironment created by coating a catalyst surface with 2D material overlayer can be used to modulate surface reactivity, which has been illustrated by optimizing oxygen reduction reaction activity on Pt(111) covered by various 2D materials. We demonstrate a concept of confined catalysis under 2D cover based on a weak van der Waals interaction between 2D material overlayers and underlying catalyst surfaces. PMID:28533413

  11. Predictive modeling in homogeneous catalysis: a tutorial

    NARCIS (Netherlands)

    Maldonado, A.G.; Rothenberg, G.

    2010-01-01

    Predictive modeling has become a practical research tool in homogeneous catalysis. It can help to pinpoint ‘good regions’ in the catalyst space, narrowing the search for the optimal catalyst for a given reaction. Just like any other new idea, in silico catalyst optimization is accepted by some

  12. Hydroxide catalysis bonding of silicon carbide

    NARCIS (Netherlands)

    Veggel, A.A. van; Ende, D.A. van den; Bogenstahl, J.; Rowan, S.; Cunningham, W.; Gubbels, G.H.M.; Nijmeijer, H.

    2008-01-01

    For bonding silicon carbide optics, which require extreme stability, hydroxide catalysis bonding is considered [Rowan, S., Hough, J. and Elliffe, E., Silicon carbide bonding. UK Patent 040 7953.9, 2004. Please contact Mr. D. Whiteford for further information: D.Whiteford@admin.gla.ac.uk]. This

  13. Supported Ionic Liquid Phase (SILP) catalysis

    DEFF Research Database (Denmark)

    Riisager, Anders; Fehrmann, Rasmus; Haumann, Marco

    2006-01-01

    Applications of ionic liquids to replace conventional solvents in homogeneous transition-metal catalysis have increased significantly during the last decade. Biphasic ionic liquid/organic liquid systems offer advantages with regard to product separation, catalyst stability, and recycling but util...

  14. Surface temperature excess in heterogeneous catalysis

    NARCIS (Netherlands)

    Zhu, L.

    2005-01-01

    In this dissertation we study the surface temperature excess in heterogeneous catalysis. For heterogeneous reactions, such as gas-solid catalytic reactions, the reactions take place at the interfaces between the two phases: the gas and the solid catalyst. Large amount of reaction heats are released

  15. Asymmetric Gepner models (revisited)

    Energy Technology Data Exchange (ETDEWEB)

    Gato-Rivera, B. [NIKHEF Theory Group, Kruislaan 409, 1098 SJ Amsterdam (Netherlands)] [Instituto de Fisica Fundamental, CSIC, Serrano 123, Madrid 28006 (Spain); Schellekens, A.N., E-mail: t58@nikhef.n [NIKHEF Theory Group, Kruislaan 409, 1098 SJ Amsterdam (Netherlands)] [Instituto de Fisica Fundamental, CSIC, Serrano 123, Madrid 28006 (Spain)] [IMAPP, Radboud Universiteit, Nijmegen (Netherlands)

    2010-12-11

    We reconsider a class of heterotic string theories studied in 1989, based on tensor products of N=2 minimal models with asymmetric simple current invariants. We extend this analysis from (2,2) and (1,2) spectra to (0,2) spectra with SO(10) broken to the Standard Model. In the latter case the spectrum must contain fractionally charged particles. We find that in nearly all cases at least some of them are massless. However, we identify a large subclass where the fractional charges are at worst half-integer, and often vector-like. The number of families is very often reduced in comparison to the 1989 results, but there are no new tensor combinations yielding three families. All tensor combinations turn out to fall into two classes: those where the number of families is always divisible by three, and those where it is never divisible by three. We find an empirical rule to determine the class, which appears to extend beyond minimal N=2 tensor products. We observe that distributions of physical quantities such as the number of families, singlets and mirrors have an interesting tendency towards smaller values as the gauge groups approaches the Standard Model. We compare our results with an analogous class of free fermionic models. This displays similar features, but with less resolution. Finally we present a complete scan of the three family models based on the triply-exceptional combination (1,16{sup *},16{sup *},16{sup *}) identified originally by Gepner. We find 1220 distinct three family spectra in this case, forming 610 mirror pairs. About half of them have the gauge group SU(3)xSU(2){sub L}xSU(2){sub R}xU(1){sup 5}, the theoretical minimum, and many others are trinification models.

  16. Polyimides Based on Asymmetric Dianhydrides (II) (a-BPDA vs a-BTDA) for Resin Transfer Molding (RTM)

    Science.gov (United States)

    Chuang, Kathy C.; Criss, Jim M.; Mintz, Eric A.

    2010-01-01

    A new series of low-melt viscosity imide resins (10-20 poise at 280 C) were formulated from asymmetric 2,3,3',4' -benzophenone dianhydride (a-BTDA) and 4-phenylethynylphthalic endcaps, along with 3,4' -oxydianiline, 3,3' -methylenedianiline and 3,3'- diaminobenzophenone, using a solvent-free melt process. a-BTDA RTM resins exhibited higher glass transition temperatures (Tg's = 330-400 C) compared to those prepared by asymmetric 2,3,3',4' -biphenyl dianhydride, (a-BPDA, Tg's = 320-370 C). These low-melt viscosity imide resins were fabricated into polyimide/T650-35 carbon fiber composites by a RTM process. Composites properties of a-BTDA resins, such as open-hole compression and short-beam shear strength, are compared to those of composites made from a-BPDA based resin at room temperature, 288 C and 315 C. These novel, high temperature RTM imide resins exhibit outstanding properties beyond the performance of conventional RTM resins, such as epoxy and BMI resins which have use-temperatures around 177 C and 232 C for aerospace applications.

  17. Bimetallic redox synergy in oxidative palladium catalysis.

    Science.gov (United States)

    Powers, David C; Ritter, Tobias

    2012-06-19

    Polynuclear transition metal complexes, which are embedded in the active sites of many metalloenzymes, are responsible for effecting a diverse array of oxidation reactions in nature. The range of chemical transformations remains unparalleled in the laboratory. With few noteworthy exceptions, chemists have primarily focused on mononuclear transition metal complexes in developing homogeneous catalysis. Our group is interested in the development of carbon-heteroatom bond-forming reactions, with a particular focus on identifying reactions that can be applied to the synthesis of complex molecules. In this context, we have hypothesized that bimetallic redox chemistry, in which two metals participate synergistically, may lower the activation barriers to redox transformations relevant to catalysis. In this Account, we discuss redox chemistry of binuclear Pd complexes and examine the role of binuclear intermediates in Pd-catalyzed oxidation reactions. Stoichiometric organometallic studies of the oxidation of binuclear Pd(II) complexes to binuclear Pd(III) complexes and subsequent C-X reductive elimination from the resulting binuclear Pd(III) complexes have confirmed the viability of C-X bond-forming reactions mediated by binuclear Pd(III) complexes. Metal-metal bond formation, which proceeds concurrently with oxidation of binuclear Pd(II) complexes, can lower the activation barrier for oxidation. We also discuss experimental and theoretical work that suggests that C-X reductive elimination is also facilitated by redox cooperation of both metals during reductive elimination. The effect of ligand modification on the structure and reactivity of binuclear Pd(III) complexes will be presented in light of the impact that ligand structure can exert on the structure and reactivity of binuclear Pd(III) complexes. Historically, oxidation reactions similar to those discussed here have been proposed to proceed via mononuclear Pd(IV) intermediates, and the hypothesis of mononuclear Pd

  18. Catalytic asymmetric carbon-carbon bond formation via allylic alkylations with organolithium compounds.

    Science.gov (United States)

    Pérez, Manuel; Fañanás-Mastral, Martín; Bos, Pieter H; Rudolph, Alena; Harutyunyan, Syuzanna R; Feringa, Ben L

    2011-05-01

    Carbon-carbon bond formation is the basis for the biogenesis of nature's essential molecules. Consequently, it lies at the heart of the chemical sciences. Chiral catalysts have been developed for asymmetric C-C bond formation to yield single enantiomers from several organometallic reagents. Remarkably, for extremely reactive organolithium compounds, which are among the most broadly used reagents in chemical synthesis, a general catalytic methodology for enantioselective C-C formation has proven elusive, until now. Here, we report a copper-based chiral catalytic system that allows carbon-carbon bond formation via allylic alkylation with alkyllithium reagents, with extremely high enantioselectivities and able to tolerate several functional groups. We have found that both the solvent used and the structure of the active chiral catalyst are the most critical factors in achieving successful asymmetric catalysis with alkyllithium reagents. The active form of the chiral catalyst has been identified through spectroscopic studies as a diphosphine copper monoalkyl species.

  19. Asymmetric distances for binary embeddings.

    Science.gov (United States)

    Gordo, Albert; Perronnin, Florent; Gong, Yunchao; Lazebnik, Svetlana

    2014-01-01

    In large-scale query-by-example retrieval, embedding image signatures in a binary space offers two benefits: data compression and search efficiency. While most embedding algorithms binarize both query and database signatures, it has been noted that this is not strictly a requirement. Indeed, asymmetric schemes that binarize the database signatures but not the query still enjoy the same two benefits but may provide superior accuracy. In this work, we propose two general asymmetric distances that are applicable to a wide variety of embedding techniques including locality sensitive hashing (LSH), locality sensitive binary codes (LSBC), spectral hashing (SH), PCA embedding (PCAE), PCAE with random rotations (PCAE-RR), and PCAE with iterative quantization (PCAE-ITQ). We experiment on four public benchmarks containing up to 1M images and show that the proposed asymmetric distances consistently lead to large improvements over the symmetric Hamming distance for all binary embedding techniques.

  20. Does asymmetric correlation affect portfolio optimization?

    Science.gov (United States)

    Fryd, Lukas

    2017-07-01

    The classical portfolio optimization problem does not assume asymmetric behavior of relationship among asset returns. The existence of asymmetric response in correlation on the bad news could be important information in portfolio optimization. The paper applies Dynamic conditional correlation model (DCC) and his asymmetric version (ADCC) to propose asymmetric behavior of conditional correlation. We analyse asymmetric correlation among S&P index, bonds index and spot gold price before mortgage crisis in 2008. We evaluate forecast ability of the models during and after mortgage crisis and demonstrate the impact of asymmetric correlation on the reduction of portfolio variance.

  1. Transition metal catalysis in confined spaces.

    Science.gov (United States)

    Leenders, Stefan H A M; Gramage-Doria, Rafael; de Bruin, Bas; Reek, Joost N H

    2015-01-21

    Transition metal catalysis plays an important role in both industry and in academia where selectivity, activity and stability are crucial parameters to control. Next to changing the structure of the ligand, introducing a confined space as a second coordination sphere around a metal catalyst has recently been shown to be a viable method to induce new selectivity and activity in transition metal catalysis. In this review we focus on supramolecular strategies to encapsulate transition metal complexes with the aim of controlling the selectivity via the second coordination sphere. As we will discuss, catalyst confinement can result in selective processes that are impossible or difficult to achieve by traditional methods. We will describe the template-ligand approach as well as the host-guest approach to arrive at such supramolecular systems and discuss how the performance of the catalyst is enhanced by confining it in a molecular container.

  2. ELECTROCHEMICAL PROMOTED CATALYSIS: TOWARDS PRACTICAL UTILIZATION

    Directory of Open Access Journals (Sweden)

    DIMITRIOS TSIPLAKIDES

    2008-07-01

    Full Text Available Electrochemical promotion (EP of catalysis has already been recognized as “a valuable development in catalytic research” (J. Pritchard, 1990 and as “one of the most remarkable advances in electrochemistry since 1950” (J. O’M. Bockris, 1996. Laboratory studies have clearly elucidated the phenomenology of electrochemical promotion and have proven that EP is a general phenomenon at the interface of catalysis and electrochemistry. The major progress toward practical utilization of EP is surveyed in this paper. The focus is given on the electropromotion of industrial ammonia synthesis catalyst, the bipolar EP and the development of a novel monolithic electropromoted reactor (MEPR in conjunction with the electropromotion of thin sputtered metal films. Future perspectives of electrochemical promotion applications in the field of hydrogen technologies are discussed.

  3. Predictive Modeling in Actinide Chemistry and Catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Ping [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-05-16

    These are slides from a presentation on predictive modeling in actinide chemistry and catalysis. The following topics are covered in these slides: Structures, bonding, and reactivity (bonding can be quantified by optical probes and theory, and electronic structures and reaction mechanisms of actinide complexes); Magnetic resonance properties (transition metal catalysts with multi-nuclear centers, and NMR/EPR parameters); Moving to more complex systems (surface chemistry of nanomaterials, and interactions of ligands with nanoparticles); Path forward and conclusions.

  4. Catalysis in micellar and macromoleular systems

    CERN Document Server

    Fendler, Janos

    1975-01-01

    Catalysis in Micellar and Macromolecular Systems provides a comprehensive monograph on the catalyses elicited by aqueous and nonaqueous micelles, synthetic and naturally occurring polymers, and phase-transfer catalysts. It delineates the principles involved in designing appropriate catalytic systems throughout. Additionally, an attempt has been made to tabulate the available data exhaustively. The book discusses the preparation and purification of surfactants; the physical and chemical properties of surfactants and micelles; solubilization in aqueous micellar systems; and the principles of

  5. Cosmic string catalysis of skyrmion decay

    Science.gov (United States)

    Gregory, Ruth; Davis, Anne-Christine; Brandenberger, Robert

    1988-01-01

    The Callan-Witten picture is developed for monopole catalyzed skyrmion decay in order to analyze the corresponding cosmic string scenario. It is discovered that cosmic strings (both ordinary and superconducting) can catalyze proton decay, but that this catalysis only occurs on the scale of the core of the string. In order to do this we have to develop a vortex model for the superconducting string. An argument is also given for the difference in the enhancement factors for monopoles and strings.

  6. Nanoheterogeneous catalysis in electrochemically induced olefin perfluoroalkylation.

    Science.gov (United States)

    Dudkina, Yulia B; Gryaznova, Tatyana V; Osin, Yuri N; Salnikov, Vadim V; Davydov, Nikolay A; Fedorenko, Svetlana V; Mustafina, Asia R; Vicic, David A; Sinyashin, Oleg G; Budnikova, Yulia H

    2015-05-21

    Ni-catalyzed electroreductive olefin perfluoroalkylation affords both monomeric and dimeric products depending on the reaction media. Recycling of the catalyst can be achieved by immobilization of a (bpy)NiBr2 complex on silica nanoparticles decorated with anchoring amino-groups. Switching the homogeneous and heterogeneous catalysts is found to be one more factor to control the product ratio. This catalytic technique is both green and atom economical and combines the advantages of nanoheterogeneous catalysis and electrocatalysis.

  7. Nanoscale Advances in Catalysis and Energy Applications

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yimin; Somorjai, Gabor A.

    2010-05-12

    In this perspective, we present an overview of nanoscience applications in catalysis, energy conversion, and energy conservation technologies. We discuss how novel physical and chemical properties of nanomaterials can be applied and engineered to meet the advanced material requirements in the new generation of chemical and energy conversion devices. We highlight some of the latest advances in these nanotechnologies and provide an outlook at the major challenges for further developments.

  8. USD Catalysis Group for Alternative Energy

    Energy Technology Data Exchange (ETDEWEB)

    Hoefelmeyer, James D.; Koodali, Ranjit; Sereda, Grigoriy; Engebretson, Dan; Fong, Hao; Puszynski, Jan; Shende, Rajesh; Ahrenkiel, Phil

    2012-03-13

    The South Dakota Catalysis Group (SDCG) is a collaborative project with mission to develop advanced catalysts for energy conversion with two primary goals: (1) develop photocatalytic systems in which polyfunctionalized TiO2 are the basis for hydrogen/oxygen synthesis from water and sunlight (solar fuels group), (2) develop new materials for hydrogen utilization in fuel cells (fuel cell group). In tandem, these technologies complete a closed chemical cycle with zero emissions.

  9. Hybrid Amyloid Membranes for Continuous Flow Catalysis.

    Science.gov (United States)

    Bolisetty, Sreenath; Arcari, Mario; Adamcik, Jozef; Mezzenga, Raffaele

    2015-12-29

    Amyloid fibrils are promising nanomaterials for technological applications such as biosensors, tissue engineering, drug delivery, and optoelectronics. Here we show that amyloid-metal nanoparticle hybrids can be used both as efficient active materials for wet catalysis and as membranes for continuous flow catalysis applications. Initially, amyloid fibrils generated in vitro from the nontoxic β-lactoglobulin protein act as templates for the synthesis of gold and palladium metal nanoparticles from salt precursors. The resulting hybrids possess catalytic features as demonstrated by evaluating their activity in a model catalytic reaction in water, e.g., the reduction of 4-nitrophenol into 4-aminophenol, with the rate constant of the reduction increasing with the concentration of amyloid-nanoparticle hybrids. Importantly, the same nanoparticles adsorbed onto fibrils surface show improved catalytic efficiency compared to the same unattached particles, pointing at the important role played by the amyloid fibril templates. Then, filter membranes are prepared from the metal nanoparticle-decorated amyloid fibrils by vacuum filtration. The resulting membranes serve as efficient flow catalysis active materials, with a complete catalytic conversion achieved within a single flow passage of a feeding solution through the membrane.

  10. Neutrons for Catalysis: A Workshop on Neutron Scattering Techniques for Studies in Catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Overbury, Steven {Steve} H [ORNL; Coates, Leighton [ORNL; Herwig, Kenneth W [ORNL; Kidder, Michelle [ORNL

    2011-10-01

    This report summarizes the Workshop on Neutron Scattering Techniques for Studies in Catalysis, held at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL) on September 16 and 17, 2010. The goal of the Workshop was to bring experts in heterogeneous catalysis and biocatalysis together with neutron scattering experimenters to identify ways to attack new problems, especially Grand Challenge problems in catalysis, using neutron scattering. The Workshop locale was motivated by the neutron capabilities at ORNL, including the High Flux Isotope Reactor (HFIR) and the new and developing instrumentation at the SNS. Approximately 90 researchers met for 1 1/2 days with oral presentations and breakout sessions. Oral presentations were divided into five topical sessions aimed at a discussion of Grand Challenge problems in catalysis, dynamics studies, structure characterization, biocatalysis, and computational methods. Eleven internationally known invited experts spoke in these sessions. The Workshop was intended both to educate catalyst experts about the methods and possibilities of neutron methods and to educate the neutron community about the methods and scientific challenges in catalysis. Above all, it was intended to inspire new research ideas among the attendees. All attendees were asked to participate in one or more of three breakout sessions to share ideas and propose new experiments that could be performed using the ORNL neutron facilities. The Workshop was expected to lead to proposals for beam time at either the HFIR or the SNS; therefore, it was expected that each breakout session would identify a few experiments or proof-of-principle experiments and a leader who would pursue a proposal after the Workshop. Also, a refereed review article will be submitted to a prominent journal to present research and ideas illustrating the benefits and possibilities of neutron methods for catalysis research.

  11. Special Issue: Coinage Metal (Copper, Silver, and Gold Catalysis

    Directory of Open Access Journals (Sweden)

    Sónia Alexandra Correia Carabineiro

    2016-06-01

    Full Text Available The subject of catalysis by coinage metals (copper, silver, and gold comes up increasingly day-by-day. This Special Issue aims to cover the numerous aspects of the use of these metals as catalysts for several reactions. It deals with synthesis and characterization of copper, silver and gold based catalysis, their characterization and use, both for heterogeneous and homogeneous catalysis, and some of their potential applications.

  12. Special Issue: Coinage Metal (Copper, Silver, and Gold) Catalysis

    OpenAIRE

    Sónia Alexandra Correia Carabineiro

    2016-01-01

    The subject of catalysis by coinage metals (copper, silver, and gold) comes up increasingly day-by-day. This Special Issue aims to cover the numerous aspects of the use of these metals as catalysts for several reactions. It deals with synthesis and characterization of copper, silver and gold based catalysis, their characterization and use, both for heterogeneous and homogeneous catalysis, and some of their potential applications.

  13. Exactly Embedded Wavefunction Methods for Characterizing Nitrogen Reduction Catalysis

    Science.gov (United States)

    2015-01-15

    SUBTITLE Exactly Embedded Wavefunction Methods for Characterizing Nitrogen Reduction Catalysis 5a. CONTRACT NUMBER N/A 5b. GRANT NUMBER FA9550... catalysis , such as hydrogen and nitrogen reduction. In a significant methodological advance from the past year, we developed an accurate and...1-0288), the Miller group developed new electronic structure embedding methods for the investigation of small- molecular activation catalysis , such as

  14. Special Issue: Coinage Metal (Copper, Silver, and Gold) Catalysis.

    Science.gov (United States)

    Carabineiro, Sónia Alexandra Correia

    2016-06-08

    The subject of catalysis by coinage metals (copper, silver, and gold) comes up increasingly day-by-day. This Special Issue aims to cover the numerous aspects of the use of these metals as catalysts for several reactions. It deals with synthesis and characterization of copper, silver and gold based catalysis, their characterization and use, both for heterogeneous and homogeneous catalysis, and some of their potential applications.

  15. Asymmetric hydrogenation using monodentate phosphoramidite ligands

    NARCIS (Netherlands)

    Minnaard, Adriaan J.; Feringa, Ben L.; Lefort, Laurent; De Vries, Johannes G.

    2007-01-01

    Monodentate phosphoramidites are excellent ligands for Rh-catalyzed asymmetric hydrogenations of substituted olefins. Enantioselectivities between 95 and 99% were obtained in the asymmetric hydrogenation of protected alpha- and beta-dehydroamino acids and esters, itaconic acid and esters, aromatic

  16. Zr(HSO{sub 4}){sub 4} as an efficient catalyst for the preparation of 10-aryl-6,8-dimethyl-6,10dihydro-5-oxa-6,8-diazaanthra[2,3-d][1,3]dioxole-7 ,9-diones under solvent-free conditions

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Jiangli [Xinxiang Medical University, Xinxiang, Henan (China). Dept. Psychology of the Second Affiliated; Li, Wei Lin; Wu, Li Qiang [Xinxiang Medical University, Xinxiang, Henan (China). School of Pharmacy

    2011-07-01

    A one-pot three-component condensation of 3,4-methylenedioxyphenol, aromatic aldehydes, and 1,3-dimethylbarbituric acid, efficiently promoted in the presence of Zr(HSO{sub 4}){sub 4} under solvent free conditions, produced 10-aryl-6,8-dimethyl-6,10-dihydro-5-oxa-6,8-diazaanthra[2,3-d][1,3] dioxole-7,9-diones. The method offers several advantages including simple, easy and clean work-up procedure, relatively short reaction times and good to high yields of the products. (author)

  17. An Efficient and Environmentally Friendly Procedure for the Synthesis of Some Novel 8-Benzylidene-4-phenyl-3,4,5,6,7,8-hexahydro-1H-quinazolin-2-ones/thiones using Tetrabutylammonium Hexatungstate as a Reusable Heterogeneous Catalyst under Solvent-Free Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Ghashang, Majid [Islamic Azad Univ., Najafabad (Iran, Islamic Republic of); Mansoor, Syed Sheik; Aswin, Krishnamoorthy [Research Department of Chemistry, Tamil Nadu (India)

    2013-11-15

    An efficient method for the preparation of 8-benzylidene-4-phenyl-3,4,5,6,7,8-hexahydro-1H-quinazolin-2-ones/thiones from the reaction of aromatic aldehydes with cyclohexanone and urea or thiourea in the presence of Tetrabutylammonium hexatungstate, [TBA]{sub 2}[W{sub 6}O{sub 19}], as an efficient, inexpensive catalyst under thermal and solvent-free conditions has been developed. Good yields, short reaction times, straightforward workup, reusability of the catalyst, and green conditions are the most obvious advantages of this procedure.

  18. B{sub 2}O{sub 3}/Al{sub 2}O{sub 3} as a new, highly efficient and reusable heterogeneous catalyst for the selective synthesis of {beta}-enamino ketones and esters under solvent-free conditions

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Jiu-Xi; Gao, Wen-Xia; Jin, Hui-Le; Ding, Jin-Chang; Wu, Hua-Yue, E-mail: huayuewu@wzu.edu.c [Wenzhou University, Wenzhou (China). Coll. of Chemistry and Materials Engineering; Zhang, Chang-Fu [Wenzhou Vocational and Technical College, Wenzhou (China)

    2010-07-01

    Boron oxide adsorbed on alumina (B{sub 2}O{sub 3}/Al{sub 2}O{sub 3}) has been found to be a new and highly efficient heterogeneous catalyst for the synthesis of {beta}-enamino ketones and esters by the enamination of various primary and secondary amines with {beta}-dicarbonyl compounds under solvent-free conditions. The important features of this methodology are broad substrate scope, high yield, no requirement of metal catalysts, high regio- and chemoselectivity and environmental friendliness. In addition, the catalyst could be recovered easily after the reactions and reused without evident loss of reactivity. (author)

  19. Asymmetric Synthesis via Chiral Aziridines

    DEFF Research Database (Denmark)

    Tanner, David Ackland; Harden, Adrian; Wyatt, Paul

    1996-01-01

    A series of chiral bis(aziridines) has been synthesised and evaluated as chelating ligands for a variety of asymmetric transformations mediated by metals [Os (dihydroxylation), Pd (allylic alkylation) Cu (cyclopropanation and aziridination, Li (1,2-addition of organolithiums to imines)]. In the b...

  20. Structure of asymmetrical peptide dendrimers

    NARCIS (Netherlands)

    Okrugin, B.M.; Neelov, I.M.; Leermakers, F.A.M.; Borisov, Oleg V.

    2017-01-01

    Structural properties of asymmetric peptide dendrimers up to the 11th generation are studied on the basis of the self-consistent field Scheutjens-Fleer numerical approach. It is demonstrated that large scale properties such as, e.g., the gyration radius, are relatively weakly affected by the

  1. Controllable Catalysis with Nanoparticles: Bimetallic Alloy Systems and Surface Adsorbates

    KAUST Repository

    Chen, Tianyou

    2016-05-16

    Transition metal nanoparticles are privileged materials in catalysis due to their high specific surface areas and abundance of active catalytic sites. While many of these catalysts are quite useful, we are only beginning to understand the underlying catalytic mechanisms. Opening the “black box” of nanoparticle catalysis is essential to achieve the ultimate goal of catalysis by design. In this Perspective we highlight recent work addressing the topic of controlled catalysis with bimetallic alloy and “designer” adsorbate-stabilized metal nanoparticles.

  2. Synergistic Catalysis: A Powerful Synthetic Strategy for New Reaction Development

    Science.gov (United States)

    Allen, Anna E.; MacMillan, David W. C.

    2012-01-01

    Synergistic catalysis is a synthetic strategy wherein both the nucleophile and the electrophile are simultaneously activated by two separate and distinct catalysts to afford a single chemical transformation. This powerful catalysis strategy leads to several benefits, specifically synergistic catalysis can (i) introduce new, previously unattainable chemical transformations, (ii) improve the efficiency of existing transformations, and (iii) create or improve catalytic enantioselectivity where stereocontrol was previously absent or challenging. This perspective aims to highlight these benefits using many of the successful examples of synergistic catalysis found in the literature. PMID:22518271

  3. A Note on Asymmetric Thick Branes

    Directory of Open Access Journals (Sweden)

    D. Bazeia

    2014-01-01

    Full Text Available We study asymmetric thick braneworld scenarios, generated after adding a constant to the superpotential associated with the scalar field. We study in particular models with odd and even polynomial superpotentials, and we show that asymmetric brane can be generated irrespective of the potential being symmetric or asymmetric. We study in addition the nonpolynomial sine-Gordon like model, also constructed with the inclusion of a constant in the standard superpotential, and we investigate gravitational stability of the asymmetric brane. The results suggest robustness of the new braneworld scenarios and add further possibilities of the construction of asymmetric branes.

  4. Catalysis in electrochemistry: from fundamentals to strategies for fuel cell development

    National Research Council Canada - National Science Library

    Santos, Elizabeth; Schmickler, Wolfgang

    2011-01-01

    "Catalysis in Electrochemistry: From Fundamentals to Strategies for Fuel Cell Development is a modern, comprehensive reference work on catalysis in electrochemistry, including principles, methods, strategies, and applications...

  5. Shape-controlled nanostructures in heterogeneous catalysis.

    Science.gov (United States)

    Zaera, Francisco

    2013-10-01

    Nanotechnologies have provided new methods for the preparation of nanomaterials with well-defined sizes and shapes, and many of those procedures have been recently implemented for applications in heterogeneous catalysis. The control of nanoparticle shape in particular offers the promise of a better definition of catalytic activity and selectivity through the optimization of the structure of the catalytic active site. This extension of new nanoparticle synthetic procedures to catalysis is in its early stages, but has shown some promising leads already. Here, we survey the major issues associated with this nanotechnology-catalysis synergy. First, we discuss new possibilities associated with distinguishing between the effects originating from nanoparticle size versus those originating from nanoparticle shape. Next, we survey the information available to date on the use of well-shaped metal and non-metal nanoparticles as active phases to control the surface atom ensembles that define the catalytic site in different catalytic applications. We follow with a brief review of the use of well-defined porous materials for the control of the shape of the space around that catalytic site. A specific example is provided to illustrate how new selective catalysts based on shape-defined nanoparticles can be designed from first principles by using fundamental mechanistic information on the reaction of interest obtained from surface-science experiments and quantum-mechanics calculations. Finally, we conclude with some thoughts on the state of the field in terms of the advances already made, the future potentials, and the possible limitations to be overcome. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Perlite-SO3H nanoparticles as an efficient and reusable catalyst for one-pot three-component synthesis of 1,2-dihydro-1-aryl-naphtho[1,2-e][1,3]oxazine-3-one derivatives under both microwave-assisted and thermal solvent-free conditions: Single crystal X-ray structure analysis and theoretical study

    Directory of Open Access Journals (Sweden)

    Ali Ramazani

    2016-01-01

    Full Text Available A general synthetic route for the synthesis of 1,2-dihydro-1-aryl-naphtho[1,2-e][1,3]oxazine-3-one derivatives has been developed using perlite-SO3H nanoparticles as efficient catalyst under both microwave-assisted and thermal solvent-free conditions. The combination of 2-naphthol, aldehyde and urea enabled the synthesis of 1,2-dihydro-1-aryl-naphtho[1,2-e][1,3]oxazine-3-one derivatives in the presence of perlite-SO3H nanoparticles in good to excellent yields. This method provides several advantages like simple work-up, environmentally benign, and shorter reaction times along with high yields. In order to explore the recyclability of the catalyst, the perlite-SO3H nanoparticles in solvent-free conditions were used as catalyst for the same reaction repeatedly and the change in their catalytic activity was studied. It was found that perlite-SO3H nanoparticles could be reused for four cycles with negligible loss of their activity. Single crystal X-ray structure analysis and theoretical studies also were investigated for 4i product. The electronic properties of the compound have been analyzed using DFT calculations (B3LYP/6-311+G*. The FMO analysis suggests that charge transfer takes place within the molecule and the HOMO is localized mainly on naphthalene and oxazinone rings whereas the LUMO resides on the naphthalene ring.

  7. Surface Science Foundations of Catalysis and Nanoscience

    CERN Document Server

    Kolasinski, Kurt K

    2012-01-01

    Surface science has evolved from being a sub-field of chemistry or physics, and has now established itself as an interdisciplinary topic. Knowledge has developed sufficiently that we can now understand catalysis from a surface science perspective. No-where is the underpinning nature of surface science better illustrated than with nanoscience. Now in its third edition, this successful textbook aims to provide students with an understanding of chemical transformations and the formation of structures at surfaces. The chapters build from simple to more advanced principles with each featuring exerc

  8. Concepts of Modern Catalysis and Kinetics

    CERN Document Server

    Chorkendorff, I

    2003-01-01

    Until now, the literature has offered a rather limited approach to the use of fundamental kinetics and their application to catalytic reactions. Subsequently, this book spans the full range from fundamentals of kinetics and heterogeneous catalysis via modern experimental and theoretical results of model studies to their equivalent large-scale industrial production processes. The result is key knowledge for students at technical universities and professionals already working in industry. "...such an enterprise will be of great value to the community, to professionals as well as graduate an

  9. Geodesics in Asymmetric Metric Spaces

    Directory of Open Access Journals (Sweden)

    Mennucci Andrea C. G.

    2014-01-01

    Full Text Available In a recent paper [17] we studied asymmetric metric spaces; in this context we studied the length of paths, introduced the class of run-continuous paths; and noted that there are different definitions of “length spaces” (also known as “path-metric spaces” or “intrinsic spaces”. In this paper we continue the analysis of asymmetric metric spaces.We propose possible definitions of completeness and (local compactness.We define the geodesics using as admissible paths the class of run-continuous paths.We define midpoints, convexity, and quasi-midpoints, but without assuming the space be intrinsic.We distinguish all along those results that need a stronger separation hypothesis. Eventually we discuss how the newly developed theory impacts the most important results, such as the existence of geodesics, and the renowned Hopf-Rinow (or Cohn-Vossen theorem.

  10. Electron Jet of Asymmetric Reconnection

    Science.gov (United States)

    Khotyaintsev, Yu. V.; Graham, D. B.; Norgren, C.; Eriksson, E.; Li, W.; Johlander, A.; Vaivads, A.; Andre, M.; Pritchett, P. L.; Retino, A.; hide

    2016-01-01

    We present Magnetospheric Multiscale observations of an electron-scale current sheet and electron outflow jet for asymmetric reconnection with guide field at the subsolar magnetopause. The electron jet observed within the reconnection region has an electron Mach number of 0.35 and is associated with electron agyrotropy. The jet is unstable to an electrostatic instability which generates intense waves with E(sub parallel lines) amplitudes reaching up to 300 mV/m and potentials up to 20% of the electron thermal energy. We see evidence of interaction between the waves and the electron beam, leading to quick thermalization of the beam and stabilization of the instability. The wave phase speed is comparable to the ion thermal speed, suggesting that the instability is of Buneman type, and therefore introduces electron-ion drag and leads to braking of the electron flow. Our observations demonstrate that electrostatic turbulence plays an important role in the electron-scale physics of asymmetric reconnection.

  11. Asymmetric information and macroeconomic dynamics

    Science.gov (United States)

    Hawkins, Raymond J.; Aoki, Masanao; Roy Frieden, B.

    2010-09-01

    We show how macroeconomic dynamics can be derived from asymmetric information. As an illustration of the utility of this approach we derive the equilibrium density, non-equilibrium densities and the equation of motion for the response to a demand shock for productivity in a simple economy. Novel consequences of this approach include a natural incorporation of time dependence into macroeconomics and a common information-theoretic basis for economics and other fields seeking to link micro-dynamics and macro-observables.

  12. Comprehensive asymmetric dark matter model

    OpenAIRE

    Lonsdale, Stephen J.; Volkas, Raymond R.

    2018-01-01

    Asymmetric dark matter (ADM) is motivated by the similar cosmological mass densities measured for ordinary and dark matter. We present a comprehensive theory for ADM that addresses the mass density similarity, going beyond the usual ADM explanations of similar number densities. It features an explicit matter-antimatter asymmetry generation mechanism, has one fully worked out thermal history and suggestions for other possibilities, and meets all phenomenological, cosmological and astrophysical...

  13. Heterogeneous Catalysis with Renewed Attention: Principles, Theories, and Concepts

    Science.gov (United States)

    Dumeignil, Franck; Paul, Jean-Francois; Paul, Sebastien

    2017-01-01

    With the development of a strong bioeconomy sector related to the creation of next-generation biorefineries, heterogeneous catalysis is receiving renewed attention. Indeed, catalysis is at the core of biorefinery design, and many new catalysts and catalytic processes are being developed. On the one hand, they are based on knowledge acquired during…

  14. The nature of the active site in heterogeneous metal catalysis

    DEFF Research Database (Denmark)

    Nørskov, Jens Kehlet; Bligaard, Thomas; Larsen, Britt Hvolbæk

    2008-01-01

    This tutorial review, of relevance for the surface science and heterogeneous catalysis communities, provides a molecular-level discussion of the nature of the active sites in metal catalysis. Fundamental concepts such as "Bronsted-Evans-Polanyi relations'' and "volcano curves'' are introduced...

  15. Comparative study of acid and basic catalysis in microwave ...

    African Journals Online (AJOL)

    Furthermore, yields of 81% and 74% respectively for the synthesis of thioamides 1 and 2 in basic catalysis with 4-methylmorpholine allows to confirm that this reaction is more advantageous in basic catalysis. The structures of thioamides synthesized were characterized and confirmed by spectroscopy Infrared (IR), nuclear ...

  16. Chemical Synthesis of Complex Molecules Using Nanoparticle Catalysis

    OpenAIRE

    Cong, Huan; Porco, John A.

    2012-01-01

    Nanoparticle catalysis has emerged as an active topic in organic synthesis. Of particular interest is the development of enabling methodologies to efficiently assemble complex molecules using nanoparticle catalysis. This Viewpoint highlights recent developments and discusses future perspectives in this emerging field.

  17. Up-down asymmetric tokamaks

    CERN Document Server

    Ball, Justin

    2016-01-01

    Bulk toroidal rotation has proven capable of stabilising both dangerous MHD modes and turbulence. In this thesis, we explore a method to drive rotation in large tokamaks: up-down asymmetry in the magnetic equilibrium. We seek to maximise this rotation by finding optimal up-down asymmetric flux surface shapes. First, we use the ideal MHD model to show that low order external shaping (e.g. elongation) is best for creating up-down asymmetric flux surfaces throughout the device. Then, we calculate realistic up-down asymmetric equilibria for input into nonlinear gyrokinetic turbulence analysis. Analytic gyrokinetics shows that, in the limit of fast shaping effects, a poloidal tilt of the flux surface shaping has little effect on turbulent transport. Since up-down symmetric surfaces do not transport momentum, this invariance to tilt implies that devices with mirror symmetry about any line in the poloidal plane will drive minimal rotation. Accordingly, further analytic investigation suggests that non-mirror symmetri...

  18. Stereoselective α-fluoroamide and α-fluoro-γ-lactone synthesis by an asymmetric zwitterionic aza-Claisen rearrangement

    Directory of Open Access Journals (Sweden)

    O'Hagan David

    2005-10-01

    Full Text Available Text Abstract Background Asymmetric introduction of fluorine α-to a carbonyl has become popular recently, largely because the direct fluorination of enolates by asymmetric electrophilic fluorinating reagents has improved, and as a result such compounds are becoming attractive synthons. We have sought an alternative but straightforward asymmetric method to this class of compounds, utilising the zwitterionic aza-Claisen rearrangement by reacting α-fluoroacid chlorides and homochiral N-allylpyrrolidines as starting materials. Results Treatment of N-allylmorpholine with 2-fluoropropionyl chloride under Yb(OTf3 catalysis generated the zwitterionic aza-Claisen rearrangement product in good yield and demonstrated the chemical feasibility of the approach. For the asymmetric reaction, N-allyl-(S-2-(methoxymethylpyrrolidine was treated with either 2-fluoropropionyl chloride or 2-fluorophenylacetic acid chloride under similar conditions and resulted in N-(α-fluoro-γ-vinylamidepyrrolidine products as homochiral materials in 99% de. These products were readily converted to their corresponding α-fluoro-γ-lactones by iodolactonisation and in good diastereoselectivity. Conclusion Molecules which have fluorine at a stereogeneic centre are finding increasing utility in pharmaceutical, fine chemicals and materials research. The zwitterionic aza-Claisen rearrangement proved to be an effective and competitive complement to asymmetric electrophilic fluorination strategies and provides access to versatile synthetic intermediates with fluorine at the stereogenic centre.

  19. Tandem Catalysis Utilizing Olefin Metathesis Reactions.

    Science.gov (United States)

    Zieliński, Grzegorz K; Grela, Karol

    2016-07-04

    Since olefin metathesis transformation has become a favored synthetic tool in organic synthesis, more and more distinct non-metathetical reactions of alkylidene ruthenium complexes have been developed. Depending on the conditions applied, the same olefin metathesis catalysts can efficiently promote isomerization reactions, hydrogenation of C=C double bonds, oxidation reactions, and many others. Importantly, these transformations can be carried out in tandem with olefin metathesis reactions. Through addition of one portion of a catalyst, a tandem process provides structurally advanced products from relatively simple substrates without the need for isolation of the intermediates. These aspects not only make tandem catalysis very attractive from a practical point of view, but also open new avenues in (retro)synthetic planning. However, in the literature, the term "tandem process" is sometimes used improperly to describe other types of multi-reaction sequences. In this Concept, a number of examples of tandem catalysis involving olefin metathesis are discussed with an emphasis on their synthetic value. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Mechanical catalysis on the centimetre scale.

    Science.gov (United States)

    Miyashita, Shuhei; Audretsch, Christof; Nagy, Zoltán; Füchslin, Rudolf M; Pfeifer, Rolf

    2015-03-06

    Enzymes play important roles in catalysing biochemical transaction paths, acting as logical machines through the morphology of the processes. A key challenge in elucidating the nature of these systems, and for engineering manufacturing methods inspired by biochemical reactions, is to attain a comprehensive understanding of the stereochemical ground rules of enzymatic reactions. Here, we present a model of catalysis that can be performed magnetically by centimetre-sized passive floating units. The designed system, which is equipped with permanent magnets only, passively obeys the local causalities imposed by magnetic interactions, albeit it shows a spatial behaviour and an energy profile analogous to those of biochemical enzymes. In this process, the enzyme units trigger physical conformation changes of the target by levelling out the magnetic potential barrier (activation potential) to a funnel type and, thus, induce cascading conformation changes of the targeted substrate units reacting in parallel. The inhibitor units, conversely, suppress such changes by increasing the potential. Because the model is purely mechanical and established on a physics basis in the absence of turbulence, each performance can be explained by the morphology of the unit, extending the definition of catalysis to systems of alternative scales.

  1. Ionic Liquid Immobilized Organocatalysts for Asymmetric Reactions in Aqueous Media

    Directory of Open Access Journals (Sweden)

    Allan D. Headley

    2013-09-01

    Full Text Available Ionic liquids are organic salts with melting points typically below ambient or reaction temperature. The unique combination of physical properties of ionic liquids, such as lack of measurable vapor pressure, high thermal and chemical stability, make them ideal to be used as reusable homogenous support for catalysts. In addition, the solubility of ionic liquids in various reaction media can be controlled and easily fine-tuned by modification of the structures of their cations and anions. As a result, ionic liquid immobilized organocatalysts are very effective in aqueous media and can be separated easily from organic solvents, as well as aqueous phases by simply adjusting the polarity of the media. Ionic liquid immobilized organocatalysts are not only very versatile compounds that are effective catalysts for a wide spectrum of reactions, but are also environmentally friendly and recyclable organocatalysts. Herein, we provide a summary of the past decade in the area of asymmetric catalysis in aqueous media for a wide variety of reactions in which ionic liquid and related ammonium salt immobilized organocatalysts are used.

  2. Switchable regioselectivity in amine-catalysed asymmetric cycloadditions

    Science.gov (United States)

    Zhou, Zhi; Wang, Zhou-Xiang; Zhou, Yuan-Chun; Xiao, Wei; Ouyang, Qin; Du, Wei; Chen, Ying-Chun

    2017-06-01

    Building small-molecule libraries with structural and stereogenic diversity plays an important role in drug discovery. The development of switchable intermolecular cycloaddition reactions from identical substrates in different regioselective fashions would provide an attractive protocol. However, this also represents a challenge in organic chemistry, because it is difficult to control regioselectivity to afford the products exclusively and at the same time achieve high levels of stereoselectivity. Here, we report the diversified cycloadditions of α‧-alkylidene-2-cyclopentenones catalysed by cinchona-derived primary amines. An asymmetric γ,β‧-regioselective intermolecular [6+2] cycloaddition reaction with 3-olefinic (7-aza)oxindoles is realized through the in situ generation of formal 4-aminofulvenes, while a different β,γ-regioselective [2+2] cycloaddition reaction with maleimides to access fused cyclobutanes is disclosed. In contrast, an intriguing α,γ-regioselective [4+2] cycloaddition reaction is uncovered with the same set of substrates, by employing an unprecedented dual small-molecule catalysis of amines and thiols. All of the cycloaddition reactions exhibit excellent regio- and stereoselectivity, producing a broad spectrum of chiral architectures with high structural diversity and molecular complexity.

  3. LG tools for asymmetric wargaming

    Science.gov (United States)

    Stilman, Boris; Yakhnis, Alex; Yakhnis, Vladimir

    2002-07-01

    Asymmetric operations represent conflict where one of the sides would apply military power to influence the political and civil environment, to facilitate diplomacy, and to interrupt specified illegal activities. This is a special type of conflict where the participants do not initiate full-scale war. Instead, the sides may be engaged in a limited open conflict or one or several sides may covertly engage another side using unconventional or less conventional methods of engagement. They may include peace operations, combating terrorism, counterdrug operations, arms control, support of insurgencies or counterinsurgencies, show of force. An asymmetric conflict can be represented as several concurrent interlinked games of various kinds: military, transportation, economic, political, etc. Thus, various actions of peace violators, terrorists, drug traffickers, etc., can be expressed via moves in different interlinked games. LG tools allow us to fully capture the specificity of asymmetric conflicts employing the major LG concept of hypergame. Hypergame allows modeling concurrent interlinked processes taking place in geographically remote locations at different levels of resolution and time scale. For example, it allows us to model an antiterrorist operation taking place simultaneously in a number of countries around the globe and involving wide range of entities from individuals to combat units to governments. Additionally, LG allows us to model all sides of the conflict at their level of sophistication. Intelligent stakeholders are represented by means of LG generated intelligent strategies. TO generate those strategies, in addition to its own mathematical intelligence, the LG algorithm may incorporate the intelligence of the top-level experts in the respective problem domains. LG models the individual differences between intelligent stakeholders. The LG tools make it possible to incorporate most of the known traits of a stakeholder, i.e., real personalities involved in

  4. Loan sales under asymmetric information

    OpenAIRE

    Vargas Martínez, Mónica

    2010-01-01

    Loans are illiquid assets that can be sold in a secondary market even that buyers have no certainty about their quality. I study a model in which a lender has access to new investment opportunities when all her assets are illiquid. To raise funds, the lender may either borrow using her assets as collateral, or she can sell them in a secondary market. Given asymmetric information about assets quality, the lender cannot recover the total value of her assets. There is then a role for the governm...

  5. Electronic structure and catalysis on metal surfaces.

    Science.gov (United States)

    Greeley, Jeff; Nørskov, Jens K; Mavrikakis, Manos

    2002-01-01

    The powerful computational resources available to scientists today, together with recent improvements in electronic structure calculation algorithms, are providing important new tools for researchers in the fields of surface science and catalysis. In this review, we discuss first principles calculations that are now capable of providing qualitative and, in many cases, quantitative insights into surface chemistry. The calculations can aid in the establishment of chemisorption trends across the transition metals, in the characterization of reaction pathways on individual metals, and in the design of novel catalysts. First principles studies provide an excellent fundamental complement to experimental investigations of the above phenomena and can often allow the elucidation of important mechanistic details that would be difficult, if not impossible, to determine from experiments alone.

  6. Heterogeneous Organo-Catalysis: Sustainable Pathways to ...

    Science.gov (United States)

    Glucose and fructose are among the most abundant plant-derived materials1 and have been converted into useful building units often used in the drug discovery and polymer architecture.2 Unfortunately, most of these conversions require mineral acids and complex heterogeneous catalysis systems which suffer from the diminished activity and recyclability issues.3 Herein, we report a highly reactive and inexpensive heterogeneous sulfonated graphitic carbon nitride (Sg-CN), endowed with strong acidity that readily transforms carbohydrates to furanics. The ready availability and benign nature of the material and its stability over the several reaction cycles renders this catalyst very useful in organic synthesis, polymer industry and in the preparation of drug precursors. Poster presentation at the 253rd American Chemical Society (ACS) National meeting in San Francisco, CA

  7. Multiple roles of graphene in heterogeneous catalysis.

    Science.gov (United States)

    Fan, Xiaobin; Zhang, Guoliang; Zhang, Fengbao

    2015-05-21

    Scientific interest in graphene as a catalyst and as a catalyst support in heterogeneous catalytic reactions has grown dramatically over the past several years. The present critical review summarizes the multiple roles of graphene in heterogeneous catalysis and highlights the influence of defects, heteroatom-containing functionalities, and graphene's two-dimensional structure on catalytic performance. We first discuss the role and advantages of graphene as a catalyst support, with emphasis on its interactions with the catalytic phases and the influence of mass transfer processes. We then clarify the origin of the intrinsic catalytic activity of graphene in heterogeneous catalytic reactions. Finally we suggest challenges and potential practical applications for graphene in industrial processes.

  8. Linking Protein Motion to Enzyme Catalysis

    Directory of Open Access Journals (Sweden)

    Priyanka Singh

    2015-01-01

    Full Text Available Enzyme motions on a broad range of time scales can play an important role in various intra- and intermolecular events, including substrate binding, catalysis of the chemical conversion, and product release. The relationship between protein motions and catalytic activity is of contemporary interest in enzymology. To understand the factors influencing the rates of enzyme-catalyzed reactions, the dynamics of the protein-solvent-ligand complex must be considered. The current review presents two case studies of enzymes—dihydrofolate reductase (DHFR and thymidylate synthase (TSase—and discusses the role of protein motions in their catalyzed reactions. Specifically, we will discuss the utility of kinetic isotope effects (KIEs and their temperature dependence as tools in probing such phenomena.

  9. Microbial biofilms: a concept for industrial catalysis?

    Science.gov (United States)

    Rosche, Bettina; Li, Xuan Zhong; Hauer, Bernhard; Schmid, Andreas; Buehler, Katja

    2009-11-01

    Biofilm reactors have long been commercially used in the treatment of wastewater and off-gas. New opportunities are arising with the rapid expansion of our understanding of biofilm biology over the last few years. Biofilms have great potential as industrial workhorses for the sustainable production of chemicals because of their inherent characteristics of self-immobilization, high resistance to reactants and long-term activity, which all facilitate continuous processing. A variety of biofilm reactor configurations have been explored for productive catalysis and some reactors have been operated continuously for months. Sectors that might particularly benefit from this biofilm approach include synthetic chemistry (ranging from specialty to bulk chemicals), bioenergy, biologics and the food industry.

  10. A DFT based method for calculating the surface energies of asymmetric MoP facets

    Science.gov (United States)

    Tian, Xinxin; Wang, Tao; Fan, Lifang; Wang, Yuekui; Lu, Haigang; Mu, Yuewen

    2018-01-01

    MoP is a promising catalyst in heterogeneous catalysis. Understanding its surface stability and morphology is the first and essential step in exploring its catalytic properties. However, traditional surface energy calculation method does not work for the asymmetric termination of MoP. In this work, we reported a useful DFT based method to get the surface energies of asymmetric MoP facets. Under ideal condition, the (101) surface with mixed Mo/P termination is most stable, followed by the (100) surface, while the (001) surface is least stable. Wulff construction reveals the exposure of six surfaces on the MoP nanoparticle, where the (101) has the largest contribution. Atomistic thermodynamics results reveal the changes in surface stability orders with experimental conditions, and the (001)-P termination becomes more and more stable with increasing P chemical potential, which indicates its exposure is possible at defined conditions. Our results agree well with the previous experimental XRD and TEM data. We believe the reported method for surface energy calculation could be extended to other similar systems with asymmetric surface terminations.

  11. One-dimensional metal oxide nanostructures for heterogeneous catalysis.

    Science.gov (United States)

    Zhang, Qian; Wang, Hsin-Yi; Jia, Xinli; Liu, Bin; Yang, Yanhui

    2013-08-21

    Metal oxides are of paramount importance in heterogeneous catalysis as either supports or active phases. Controlled synthesis of one-dimensional (1D) metal oxide nanostructures has received enormous attention in heterogeneous catalysis due to the possibility of tailoring the properties of metal oxides by tuning their shapes, sizes, and compositions. This feature article highlights recent advances in shape controlled synthesis of 1D metal oxide nanostructures and their applications in heterogeneous catalysis, with the aim of introducing new insights into the heterogeneous catalyst design.

  12. Iminium and enamine catalysis in enantioselective photochemical reactions

    Science.gov (United States)

    Hörmann, Fabian M.

    2018-01-01

    Although enantioselective catalysis under thermal conditions has been well established over the last few decades, the enantioselective catalysis of photochemical reactions is still a challenging task resulting from the complex enantiotopic face differentiation in the photoexcited state. Recently, remarkable achievements have been reported by a synergistic combination of organocatalysis and photocatalysis, which have led to the expedient construction of a diverse range of enantioenriched molecules which are generally not easily accessible under thermal conditions. In this tutorial review, we summarize and highlight the most significant advances in iminium and enamine catalysis of enantioselective photochemical reactions, with an emphasis on catalytic modes and reaction types. PMID:29155908

  13. Titanium dioxide photo catalysis: present situation and future approaches

    Energy Technology Data Exchange (ETDEWEB)

    Akira, Fujishima; Xintong, Zhang [Kanagawa Academy of Science and Technology, Takatsu-ku, Kanagawa (Japan)

    2006-05-15

    Scientific studies on photo-catalysis started about three decades ago. Titanium dioxide (TiO{sub 2}), which is one of the most basic materials in our daily life, has emerged as an excellent photo-catalyst material for environmental purification. In this short account, we will briefly discuss some fundamental studies on TiO{sub 2} photo-catalysis, summarize the present commercialization of TiO{sub 2}-based products, and highlight several points for the future development of TiO{sub 2} photo-catalysis. (authors)

  14. A new era of catalysis: efficiency, value, and sustainability.

    Science.gov (United States)

    Cheng, Soofin; Lin, Shawn D

    2014-06-01

    Value proposition: Global warming and climate change urge the chemical industry to develop new processes, in which sustainability is a necessity and requirement. Catalysis is recognized to be one of the key technologies in enabling sustainability. This special issue, assembled by guest editors Soofing Chen and Shawn D. Lin, highlights some of the best work presented at "The 6th Asia-Pacific Congress on Catalysis (APCAT-6)", with as major theme "New Era of Catalysis: Efficiency, Value, and Sustainability". © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Prebiotic RNA Synthesis by Montmorillonite Catalysis

    Science.gov (United States)

    Jheeta, Sohan; Joshi, Prakash C.

    2014-08-01

    This review summarizes our recent findings on the role of mineral salts in prebiotic RNA synthesis, which is catalyzed by montmorillonite clay minerals. The clay minerals not only catalyze the synthesis of RNA but also facilitate homochiral selection. Preliminary data of these findings have been presented at the "Horizontal Gene Transfer and the Last Universal Common Ancestor (LUCA)" conference at the Open University, Milton Keynes, UK, 5-6 September 2013. The objective of this meeting was to recognize the significance of RNA in LUCA. We believe that the prebiotic RNA synthesis from its monomers must have been a simple process. As a first step, it may have required activation of the 5'-end of the mononucleotide with a leaving group, e.g., imidazole in our model reaction (Figure 1). Wide ranges of activating groups are produced from HCN under plausible prebiotic Earth conditions. The final step is clay mineral catalysis in the presence of mineral salts to facilitate selective production of functional RNA. Both the clay minerals and mineral salts would have been abundant on early Earth. We have demonstrated that while montmorillonite (pH 7) produced only dimers from its monomers in water, addition of sodium chloride (1 M) enhanced the chain length multifold, as detected by HPLC. The effect of monovalent cations on RNA synthesis was of the following order: Li+ > Na+ > K+. A similar effect was observed with the anions, enhancing catalysis in the following order: Cl- > Br- > I-. The montmorillonite-catalyzed RNA synthesis was not affected by hydrophobic or hydrophilic interactions. We thus show that prebiotic synthesis of RNA from its monomers was a simple process requiring only clay minerals and a small amount of salt.

  16. Asymmetric liberations in exterior resonances

    Science.gov (United States)

    Beauge, C.

    1994-10-01

    The purpose of this paper is to present a general analysis of the planar circular restricted problem of three bodies in the case of exterior mean-motion resonances. Particularly, our aim is to map the phase space of various commensurabilities and determine the singular solutions of the averaged system, comparing them to the well-known case of interior resonances. In some commensurabilities (e.g. 1/2, 1/3) we show the existence of asymmetric librations; that is, librations in which the stationary value of the critical angle theta = (p+q) lambda1-p lambda-q pi is not equal to either zero or pi. The origin, stability and morphogenesis of these solutions are discussed and compared to symmetric librations. However, in some other resonances (e.g. 2/3, 3/4), these fixed points of the mean system seem to be absent. Librations in such cases are restricted to theta = O mod(pi). Asymmetric singular solutions of the plane circular problem are unknown in the case of interior resonances and cannot be reproduced by the reduced Andoyer Hamiltonian known as the Second Fundamental Model for Resonance. However, we show that the extended version of this Hamiltonian function, in which harmonics up to order two are considered, can reproduce fairly well the principal topological characteristics of the phase space and thereby constitutes a simple and useful analytical approximation for these resonances.

  17. Asymmetric Laguerre-Gaussian beams

    Science.gov (United States)

    Kovalev, A. A.; Kotlyar, V. V.; Porfirev, A. P.

    2016-06-01

    We introduce a family of asymmetric Laguerre-Gaussian (aLG) laser beams. The beams have been derived via a complex-valued shift of conventional LG beams in the Cartesian plane. While propagating in a uniform medium, the first bright ring of the aLG beam becomes less asymmetric and the energy is redistributed toward peripheral diffraction rings. The projection of the orbital angular momentum (OAM) onto the optical axis is calculated. The OAM is shown to grow quadratically with increasing asymmetry parameter of the aLG beam, which equals the ratio of the shift to the waist radius. Conditions for the OAM becoming equal to the topological charge have been derived. For aLG beams with zero radial index, we have deduced an expression to define the intensity maximum coordinates and shown the crescent-shaped intensity pattern to rotate during propagation. Results of the experimental generation and rotation of aLG beams agree well with theoretical predictions.

  18. Thin lenses of asymmetric power

    Directory of Open Access Journals (Sweden)

    W. F. Harris

    2009-12-01

    Full Text Available It is generally supposed that thin systems, including refracting surfaces and thin lenses, have powers that are necessarily symmetric.  In other words they have powers which can be represented assymmetric dioptric power matrices and in the familar spherocylindrical form used in optometry and ophthalmology.  This paper shows that this is not correct and that it is indeed possible for a thin system to have a power that is not symmetric and which cannot be expressed in spherocylindrical form.  Thin systems of asymmetric power are illustratedby means of a thin lens that is modelled with small prisms and is chosen to have a dioptric power ma-trix that is antisymmetric.  Similar models can be devised for a thin system whose dioptric power matrix is any  2 2 ×  matrix.  Thus any power, symmetric, asymmetric or antisymmetric, is possible for a thin system.  In this sense our understanding of the power of thin systems is now complete.

  19. Nano Fe{sub 2}O{sub 3,} clinoptilolite and H{sub 3}PW{sub 12}O{sub 40} as efficient catalysts for solvent-free synthesis of 5(4H)-isoxazolone under microwave irradiation conditions

    Energy Technology Data Exchange (ETDEWEB)

    Fozooni, Samieh, E-mail: samieh.fozooni@uk.ac.ir, E-mail: s_fozooni@yahoo.com [Shahid Bahonar University, Kerman (Iran, Islamic Republic of). Mining Engineering Department. Zarand High Education Center; Hosseinzadeh, Nasrin Gholam; Akhgar, Mohammad Reza [Islamic Azad University, Kerman (Iran, Islamic Republic of). Department of Chemistry; Hamidian, Hooshang [Payame Noor University (PNU), Tehran (Iran, Islamic Republic of). Department of Chemistry

    2013-10-15

    A quick and solvent-free approach involving the exposure of neat reactants to microwave irradiation in conjunction with the use of clinoptilolite, H{sub 3}PW{sub 12}O{sub 40} and Fe{sub 2}O{sub 3} nanoparticle catalysts is described. In this work, condensation of hydroxylamine hydrochloride, sodium acetate, acetoacetic or benzoyl acetic ethyl ester and appropriate aldehydes by employing catalysts gave 5(4H)-isoxazolone only in one step. Catalyst amount, temperature effects and catalysts reusability were monitored. Among the catalysts, Fe{sub 2}O{sub 3} nanoparticles had better performance than other catalysts from viewpoint of yield and reaction time. The present protocol offers several advantages, such as short reaction time, reasonable yield, mild reaction condition and recycling catalysts with a very easy workup. (author)

  20. Density functional theory studies of transition metal nanoparticles in catalysis

    DEFF Research Database (Denmark)

    Greeley, Jeffrey Philip; Rankin, Rees; Zeng, Zhenhua

    2013-01-01

    Periodic Density Functional Theory calculations are capable of providing powerful insights into the structural, energetics, and electronic phenomena that underlie heterogeneous catalysis on transition metal nanoparticles. Such calculations are now routinely applied to single crystal metal surfaces...... and to subnanometer metal clusters. Descriptions of catalysis on truly nanosized structures, however, are generally not as well developed. In this talk, I will illustrate different approaches to analyzing nanocatalytic phenomena with DFT calculations. I will describe case studies from heterogeneous catalysis...... and electrocatalysis, in which single crystal models are combined with Wulff construction-based ideas to produce descriptions of average nanocatalyst behavior. Then, I will proceed to describe explicitly DFT-based descriptions of catalysis on truly nanosized particles (