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Sample records for asymmetric ring-closing olefin

  1. Highly Active Chiral Ruthenium Catalysts for Asymmetric Ring-Closing Olefin Metathesis

    Science.gov (United States)

    Funk, Timothy W.; Berlin, Jacob M.

    2008-01-01

    The synthesis of olefin metathesis catalysts containing chiral, monodentate N-heterocyclic carbenes and their application to asymmetric ring-closing metathesis (ARCM) is reported. These catalysts retain the high levels of reactivity found in the related achiral variants (1a and 1b). Using the parent chiral catalysts 2a and 2b and derivatives that contain steric bulk in the meta positions of the N-bound aryl rings (catalysts 3-5), five- through seven-membered rings were formed in up to 92% ee. The addition of sodium iodide to catalysts 2a-4a (to form 2b-4bin situ) caused a dramatic increase in enantioselectivity for many substrates. Catalyst 5a, which gave high enantiomeric excesses for certain substrates without the addition of NaI, could be used in loadings of ≤1 mol %. Mechanistic explanations for the large sodium iodide effect as well as possible mechanistic pathways leading to the observed products are discussed. PMID:16464082

  2. Iron(III)-Catalyzed Ring-Closing Carbonyl-Olefin Metathesis.

    Science.gov (United States)

    Saá, Carlos

    2016-09-01

    Recent developments in catalytic carbonyl-olefin metathesis are summarized in this Highlight. Schindler and co-workers have reported that the environmentally benign FeCl3 catalyst promotes ring-closing carbonyl-olefin metathesis (RCCOM) in high yield under very mild conditions.

  3. FeCl3 -Catalyzed Ring-Closing Carbonyl-Olefin Metathesis.

    Science.gov (United States)

    Ma, Lina; Li, Wenjuan; Xi, Hui; Bai, Xiaohui; Ma, Enlu; Yan, Xiaoyu; Li, Zhiping

    2016-08-22

    Exploiting catalytic carbonyl-olefin metathesis is an ongoing challenge in organic synthesis. Reported herein is an FeCl3 -catalyzed ring-closing carbonyl-olefin metathesis. The protocol allows access to a range of carbo-/heterocyclic alkenes with good efficiency and excellent trans diastereoselectivity. The methodology presents one of the rare examples of catalytic ring-closing carbonyl-olefin metathesis. This process is proposed to take place by FeCl3 -catalyzed oxetane formation followed by retro-ring-opening to deliver metathesis products.

  4. Asymmetric allylic alkylation in combination with ring-closing metathesis for the preparation of chiral N-heterocycles

    NARCIS (Netherlands)

    Teichert, Johannes F.; Zhang, Suyan; Zijl, Anthoni W. van; Slaa, Jan Willem; Minnaard, Adriaan J.; Feringa, Bernard

    2010-01-01

    Asymmetric copper-catalyzed allylic substitution with methylmagnesium bromide is employed in combination with ring-closing olefin metathesis or ene-yne metathesis to achieve the synthesis of chiral, unsaturated nitrogen heterocycles. The resulting six- to eight-membered chiral heterocycles are acces

  5. Multiple Olefin Metathesis Polymerization That Combines All Three Olefin Metathesis Transformations: Ring-Opening, Ring-Closing, and Cross Metathesis.

    Science.gov (United States)

    Lee, Ho-Keun; Bang, Ki-Taek; Hess, Andreas; Grubbs, Robert H; Choi, Tae-Lim

    2015-07-29

    We demonstrated tandem ring-opening/ring-closing metathesis (RO/RCM) polymerization of monomers containing two cyclopentene moieties and postmodification via insertion polymerization. In this system, well-defined polymers were efficiently formed by tandem cascade RO/RCM reaction pathway. Furthermore, these polymers could be transformed to new A,B-alternating copolymers via a sequential cross metathesis reaction with a diacrylate. Additionally, we demonstrated the concept of multiple olefin metathesis polymerization in which the dicyclopentene and diacrylate monomers underwent all three olefin metathesis transformations (ring-opening, ring-closing, and cross metathesis) in one shot to produce A,B-alternating copolymer.

  6. Olefin Ring Closing Metathesis and Hydrosilylation Reaction in Aqueous Medium by Grubbs Second Generation Ruthenium Catalyst

    Science.gov (United States)

    The Grubbs second generation ruthenium catalyst was shown to catalyze various olefin ring closing metathesis and hydrosilylation reactions in aqueous medium. Reactions proceeded in pure water without any additives or co-solvents, in a short period of time. We found that inhomogen...

  7. Allyl sulphides in olefin metathesis: catalyst considerations and traceless promotion of ring-closing metathesis.

    Science.gov (United States)

    Edwards, Grant A; Culp, Phillip A; Chalker, Justin M

    2015-01-11

    Allyl sulphides are reactive substrates in ruthenium-catalysed olefin metathesis reactions, provided each substrate is matched with a suitable catalyst. A profile of catalyst activity is described, along with the first demonstration of allyl sulphides as traceless promoters in relayed ring-closing metathesis reactions.

  8. Construction of carbocyclic ring of indoles using ruthenium-catalyzed ring-closing olefin metathesis.

    Science.gov (United States)

    Yoshida, Kazuhiro; Hayashi, Kazushi; Yanagisawa, Akira

    2011-09-16

    The selective synthesis of substituted indoles was achieved by the ring-closing olefin metathesis (RCM)/elimination sequence or the RCM/tautomerization sequence of functionalized pyrrole precursors. The RCM/elimination sequence was also applied to double ring closure to yield a substituted carbazole.

  9. Study towards diversity oriented synthesis of optically active substituted cyclopentane fused carbocyclic and oxacyclic medium-sized rings: Competition between Grubbs-II catalyzed ring closing olefin metathesis and ring closing carbonyl-olefin metathesis

    Indian Academy of Sciences (India)

    P CHAKRABORTY; S C ROY

    2016-12-01

    A study towards diversity-oriented synthesis of optically active cyclopentane fused bicyclic frameworks has been accomplished. The common intermediate was prepared from commercially available starting material (S)-carvone. The observations on competition between Grubbs-II catalyzed ring closing metathesis (RCM) and ring closing carbonyl-olefin metathesis (RCCOM) were the key features of the study.

  10. Synthesis of all-hydrocarbon stapled α-helical peptides by ring-closing olefin metathesis.

    Science.gov (United States)

    Kim, Young-Woo; Grossmann, Tom N; Verdine, Gregory L

    2011-06-01

    This protocol provides a detailed procedure for the preparation of stapled α-helical peptides, which have proven their potential as useful molecular probes and as next-generation therapeutics. Two crucial features of this protocol are (i) the construction of peptide substrates containing hindered α-methyl, α-alkenyl amino acids and (ii) the ring-closing olefin metathesis (RCM) of the resulting resin-bound peptide substrates. The stapling systems described in this protocol, namely bridging one or two turns of an α-helix, are highly adaptable to most peptide sequences, resulting in favorable RCM kinetics, helix stabilization and promotion of cellular uptake.

  11. Orthogonal ring-closing alkyne and olefin metathesis for the synthesis of small GTPase-targeting bicyclic peptides.

    Science.gov (United States)

    Cromm, Philipp M; Schaubach, Sebastian; Spiegel, Jochen; Fürstner, Alois; Grossmann, Tom N; Waldmann, Herbert

    2016-04-14

    Bicyclic peptides are promising scaffolds for the development of inhibitors of biological targets that proved intractable by typical small molecules. So far, access to bioactive bicyclic peptide architectures is limited due to a lack of appropriate orthogonal ring-closing reactions. Here, we report chemically orthogonal ring-closing olefin (RCM) and alkyne metathesis (RCAM), which enable an efficient chemo- and regioselective synthesis of complex bicyclic peptide scaffolds with variable macrocycle geometries. We also demonstrate that the formed alkyne macrocycle can be functionalized subsequently. The orthogonal RCM/RCAM system was successfully used to evolve a monocyclic peptide inhibitor of the small GTPase Rab8 into a bicyclic ligand. This modified peptide shows the highest affinity for an activated Rab GTPase that has been reported so far. The RCM/RCAM-based formation of bicyclic peptides provides novel opportunities for the design of bioactive scaffolds suitable for the modulation of challenging protein targets.

  12. Introduction of all-hydrocarbon i,i+3 staples into alpha-helices via ring-closing olefin metathesis.

    Science.gov (United States)

    Kim, Young-Woo; Kutchukian, Peter S; Verdine, Gregory L

    2010-07-02

    The introduction of all-hydrocarbon i,i+3 staples into alpha-helical peptide scaffolds via ring-closing olefin metathesis (RCM) between two alpha-methyl,alpha-pentenylglycine residues incorporated at i and i+3 positions, which lie on the same face of the helix, has been investigated. The reactions were found to be highly dependent upon the side-chain stereochemistry of the amino acids undergoing RCM. The i,i+3 stapling system established here provides a potentially useful alternative to the well-established i,i+4 stapling system now in widespread use.

  13. Nobel Chemistry in the Laboratory: Synthesis of a Ruthenium Catalyst for Ring-Closing Olefin Metathesis--An Experiment for the Advanced Inorganic or Organic Laboratory

    Science.gov (United States)

    Greco, George E.

    2007-01-01

    An experiment for the upper-level undergraduate laboratory is described in which students synthesize a ruthenium olefin metathesis catalyst, then use the catalyst to carry out the ring-closing metathesis of diethyl diallylmalonate. The olefin metathesis reaction was the subject of the 2005 Nobel Prize in chemistry. The catalyst chosen for this…

  14. Control of olefin geometry in macrocyclic ring-closing metathesis using a removable silyl group.

    Science.gov (United States)

    Wang, Yikai; Jimenez, Miguel; Hansen, Anders S; Raiber, Eun-Ang; Schreiber, Stuart L; Young, Damian W

    2011-06-22

    Introducing a silyl group at one of the internal olefin positions in diolefinic substrates results in E-selective olefin formation in macrocyclic ring-forming metathesis. The application of this method to a range of macrocyclic (E)-alkenylsiloxanes is described. Protodesilylation of alkenylsiloxane products yields novel Z-configured macrocycles.

  15. Low Catalyst Loadings in Olefin Metathesis: Synthesis of Nitrogen Heterocycles by Ring Closing Metathesis

    Science.gov (United States)

    Kuhn, Kevin M.; Champagne, Timothy M.; Hong, Soon Hyeok; Wei, Wen-Hao; Nickel, Andrew; Lee, Choon Woo; Virgil, Scott C.; Grubbs, Robert H.; Pederson, Richard L.

    2010-01-01

    (eq 1) A series of ruthenium catalysts have been screened under ring closing metathesis (RCM) conditions to produce five-, six-, and seven-membered carbamate-protected cyclic amines. Many of these catalysts demonstrated excellent RCM activity and yields with as low as 500 ppm catalyst loadings. RCM of the five-membered carbamate-series could be run neat, the six-membered carbamate-series could be run at 1.0 M concentrations and the seven-membered carbamate-series worked best at 0.2 M to 0.05 M concentrations. PMID:20141172

  16. Low catalyst loadings in olefin metathesis: synthesis of nitrogen heterocycles by ring-closing metathesis.

    Science.gov (United States)

    Kuhn, Kevin M; Champagne, Timothy M; Hong, Soon Hyeok; Wei, Wen-Hao; Nickel, Andrew; Lee, Choon Woo; Virgil, Scott C; Grubbs, Robert H; Pederson, Richard L

    2010-03-01

    A series of ruthenium catalysts have been screened under ring-closing metathesis (RCM) conditions to produce five-, six-, and seven-membered carbamate-protected cyclic amines. Many of these catalysts demonstrated excellent RCM activity and yields with as low as 500 ppm catalyst loadings. RCM of the five-membered carbamate series could be run neat, the six-membered carbamate series could be run at 1.0 M, and the seven-membered carbamate series worked best at 0.2-0.05 M.

  17. The application of catalytic ring-closing olefin metathesis to the synthesis of unsaturated oxygen heterocycles

    Energy Technology Data Exchange (ETDEWEB)

    Fu, G.C.; Grubbs, R.H. [California Institute of Technology, Pasadena, CA (United States)

    1992-06-17

    The development of general approaches to carbon-carbon bond formation represents an important ongoing challenge for synthetic organic chemists. One efficient method for constructing carbon-carbon double bonds, the transition metal alkylidene-catalyzed olefin metathesis reaction, has been the focus of intense interest in recent years from the standpoint of both mechanism and polymer synthesis, in contrast, use of this transformation in organic synthesis has been limited. As part of a broader program directed toward establishing transition metal alkylidenes as versatile reagents for organic chemistry, the authors report the successful application of catalytic olefin methathesis to the generation of a variety of unsaturated oxygen heterocycles. 13 refs., 1 fig., 1 tab.

  18. Potent macrocyclic inhibitors of insulin-regulated aminopeptidase (IRAP) by olefin ring-closing metathesis.

    Science.gov (United States)

    Andersson, Hanna; Demaegdt, Heidi; Johnsson, Anders; Vauquelin, Georges; Lindeberg, Gunnar; Hallberg, Mathias; Erdelyi, Mate; Karlen, Anders; Hallberg, Anders

    2011-06-01

    Macrocyclic analogues of angiotensin IV (Ang IV, Val(1)-Tyr(2)-Ile(3)-His(4)-Pro(5)-Phe(6)) targeting the insulin-regulated aminopeptidase (IRAP) have been designed, synthesized, and evaluated biologically. Replacement of His(4)-Pro(5)-Phe(6) by a 2-(aminomethyl)phenylacetic acid (AMPAA) moiety and of Val(1) and Ile(3) by amino acids bearing olefinic side chains followed by macrocyclization provided potent IRAP inhibitors. The impact of the ring size and the type (saturated versus unsaturated), configuration, and position of the carbon-carbon bridge was assessed. The ring size generally affects the potency more than the carbon-carbon bond characteristics. Replacing Tyr(2) by β(3)hTyr or Phe is accepted, while N-methylation of Tyr(2) is deleterious for activity. Removal of the carboxyl group in the C-terminal slightly reduced the potency. Inhibitors 7 (K(i) = 4.1 nM) and 19 (K(i) = 1.8 nM), both encompassing 14-membered ring systems connected to AMPAA, are 10-fold more potent than Ang IV and are also more selective over aminopeptidase N (AP-N). Both compounds displayed high stability against proteolysis by metallopeptidases.

  19. New and Concise Syntheses of the Bicyclic Oxamazin Core Using an Intramolecular Nitroso Diels-Alder Reaction and Ring-Closing Olefin Metathesis

    Science.gov (United States)

    Watson, Kyle D.; Carosso, Serena

    2013-01-01

    Herein two new and concise synthetic approaches for making an unsaturated bicyclic oxamazin core are reported. The first involves the use of an intramolecular Diels-Alder reaction to form both of the fused rings in one step. The second approach incorporates ring-closing olefin metathesis in the final step to form the second fused ring of the core. The scope of the second approach was also expanded further to afford larger ringed bicyclic systems. PMID:23276301

  20. New and concise syntheses of the bicyclic oxamazin core using an intramolecular nitroso Diels-Alder reaction and ring-closing olefin metathesis.

    Science.gov (United States)

    Watson, Kyle D; Carosso, Serena; Miller, Marvin J

    2013-01-18

    Herein two new and concise synthetic approaches for making an unsaturated bicyclic oxamazin core are reported. The first involves the use of an intramolecular Diels-Alder reaction to form both of the fused rings in one step. The second approach incorporates ring-closing olefin metathesis in the final step to form the second fused ring of the core. The scope of the second approach was also expanded further to afford larger ringed bicyclic systems.

  1. Synthesis of the EF-ring of ciguatoxin 3C based on the [2,3]-Wittig rearrangement and ring-closing olefin metathesis.

    Science.gov (United States)

    Goto, Akiyoshi; Fujiwara, Kenshu; Kawai, Ayako; Kawai, Hidetoshi; Suzuki, Takanori

    2007-12-20

    The EF-ring segment of ciguatoxin 3C, a causative toxin of ciguatera fish poisoning, was synthesized in three major steps: 1,4-addition for the C20O-C27 bond connection, chirality transferring anti selective [2,3]-Wittig rearrangement for the construction of the anti-2-hydroxyalkyl ether part, and ring-closing olefin metathesis for the F-ring formation.

  2. Efficient ring-closing metathesis of alkenyl bromides: the importance of protecting the catalyst during the olefin approach.

    Science.gov (United States)

    Gatti, Michele; Drinkel, Emma; Wu, Linglin; Pusterla, Ivano; Gaggia, Fiona; Dorta, Reto

    2010-11-01

    We present the first productive ring-closing metathesis reaction that leads to the construction of cyclic alkenyl bromides. Efficient catalysis employing commercially available Grubbs II catalyst is possible through appropriate modification of the starting bromoalkene moiety.

  3. The Right Computational Recipe for Olefin Metathesis with Ru-Based Catalysts: The Whole Mechanism of Ring-Closing Olefin Metathesis.

    Science.gov (United States)

    Poater, Albert; Pump, Eva; Vummaleti, Sai Vikrama Chaitanya; Cavallo, Luigi

    2014-10-14

    The initiation mechanism of ruthenium methylidene complexes was studied detailing mechanistic insights of all involved reaction steps within a classical olefin metathesis pathway. Computational studies reached a good agreement with the rarely available experimental data and even enabled to complement them. As a result, a highly accurate computational and rather cheap recipe is presented; M06/TZVP//BP86/SVP (PCM, P = 1354 atm).

  4. The right computational recipe for olefin metathesis with ru-based catalysts: The whole mechanism of ring-closing olefin metathesis

    KAUST Repository

    Poater, Albert

    2014-10-14

    The initiation mechanism of ruthenium methylidene complexes was studied detailing mechanistic insights of all involved reaction steps within a classical olefin metathesis pathway. Computational studies reached a good agreement with the rarely available experimental data and even enabled to complement them. As a result, a highly accurate computational and rather cheap recipe is presented; M06/TZVP//BP86/SVP (PCM, P = 1354 atm).

  5. Accelerating influence of the gem-difluoromethylene group in a ring-closing olefin metathesis reaction. A Thorpe-Ingold effect?

    Science.gov (United States)

    Urbina-Blanco, César A; Skibiński, Maciej; O'Hagan, David; Nolan, Steven P

    2013-08-21

    The gem-difluoromethylene (CF2) group significantly accelerates ring-closing metathesis of 1,8-nonadienes relative to the methylene (CH2) group demonstrating similar rate accelerations to that observed for the classic Thorpe-Ingold substituents, diester malonates and ketals.

  6. Synthesis of cyclic 1-alkenylboronates via Zr-mediated double functionalization of alkynylboronates and sequential Ru-catalyzed ring-closing olefin metathesis.

    Science.gov (United States)

    Nishihara, Yasushi; Suetsugu, Masato; Saito, Daisuke; Kinoshita, Megumi; Iwasaki, Masayuki

    2013-05-17

    Synthesis of novel cyclic 1-alkenylboronates is accomplished through the zirconium-mediated regio- and stereoselective double functionalization of 1-alkynylboronates and the subsequent ruthenium-catalyzed ring-closing metathesis (RCM). The obtained substituted cyclic 1-alkenylboronates are transformed into o-terphenyl and triphenylene derivatives.

  7. Mo-catalyzed asymmetric olefin metathesis in target-oriented synthesis: Enantioselective synthesis of (+)-africanol

    Science.gov (United States)

    Weatherhead, Gabriel S.; Cortez, G. A.; Schrock, Richard R.; Hoveyda, Amir H.

    2004-01-01

    Catalytic asymmetric ring-opening metathesis (AROM) provides an efficient method for the synthesis of a variety of optically enriched small organic molecules that cannot be easily prepared by alternative methods. The development of Mo-catalyzed AROM transformations that occur in tandem with ring-closing metathesis are described. The utility of the Mo-catalyzed AROM/ring-closing metathesis is demonstrated through an enantioselective approach to the synthesis of (+)-africanol. PMID:15056762

  8. Amino acids as chiral anionic ligands for ruthenium based asymmetric olefin metathesis.

    Science.gov (United States)

    Ivry, Elisa; Ben-Asuly, Amos; Goldberg, Israel; Lemcoff, N Gabriel

    2015-03-01

    Several amino acid ligands were introduced into the Hoveyda-Grubbs 2nd generation complex by a facile anionic ligand exchange. The chiral pre-catalysts obtained displayed enantioselectivity in asymmetric ring-closing and ring-opening cross-metathesis reactions. Reduction of the lability of the carboxylate ligands was found to be cardinal for improving the observed enantiomeric product enrichment.

  9. Efficient synthesis of enantiopure conduritols by ring-closing metathesis

    DEFF Research Database (Denmark)

    Jørgensen, Morten; Iversen, Erik Høgh; Paulsen, Andreas Lundtang;

    2001-01-01

    Two short synthetic approaches to enantiopure conduritols are described starting from the chiral pool. In both cases, the cyclohexene ring is assembled via ring-closing olefin metathesis. The terminal diene precursers for the metathesis reaction are prepared either from octitols or from tartaric...

  10. An asymmetric route to 2,3-epoxy-syn-1,4-cyclohexane diol derivatives using ring closing metathesis (RCM)

    Indian Academy of Sciences (India)

    Soumitra Maity; Subrata Ghosh

    2010-11-01

    An asymmetric route for the synthesis of highly functionalized 2,3-epoxy-syn-1,4-cyclohexane diol derivatives present in some polyketide natural products has been developed. The key step involves RCM of an appropriately constructed 1,7-dienol derived from D-mannitol to cyclohexane-1,4-diol followed by its stereoselective epoxidation.

  11. Monodentate phosphoramidites : A breakthrough in rhodium-catalysed asymmetric hydrogenation of olefins

    NARCIS (Netherlands)

    Berg, Michel van den; Minnaard, Adriaan J.; Haak, Robert M.; Leeman, Michel; Schudde, Ebe P.; Meetsma, Auke; de Vries, Andre H.M.; Maljaars, C. Elizabeth P.; Willans, Charlotte E.; Hyett, David; Boogers, Jeroen A.F.; Henderickx, Hubertus; Feringa, Ben L.

    2003-01-01

    Monodentate phosphoramidites based on BINOL or substituted BINOL are excellent ligands for the rhodium-catalysed asymmetric hydrogenation of olefins. Very high enantioselectivities were obtained with MonoPhos (7a) the simplest member of this class, a ligand that is prepared in a single step from BIN

  12. Olefins-selective asymmetric carbon molecular sieve hollow fiber membranes for hybrid membrane-distillation processes for olefin/paraffin separations

    KAUST Repository

    Xu, Liren

    2012-12-01

    In this paper, the development of asymmetric carbon molecular sieve (CMS) hollow fiber membranes and advanced processes for olefin/paraffin separations based on the CMS membranes are reported. Membrane-based olefin/paraffin separations have been pursued extensively over the past decades. CMS membranes are promising to exceed the performance upper bound of polymer materials and have demonstrated excellent stability for gas separations. Previously, a substructure collapse phenomenon was found in Matrimid ® precursor derived CMS fiber. To overcome the permeance loss due to the increased separation layer thickness, 6FDA-DAM and 6FDA/BPDA-DAM precursors were selected as potential new precursors for carbon membrane formation. Defect-free asymmetric 6FDA-DAM and 6FDA/BPDA-DAM hollow fibers were successfully fabricated from a dry-jet/wet-quench spinning process. Polymer rigidity, glass-rubber transition and asymmetric morphology were correlated. CMS hollow fiber membranes produced from 6FDA-polymer precursors showed significant improvement in permeance for ethylene/ethane and propylene/propane separations. Further studies revealed that the CMS membranes are olefins-selective, which means the membranes are able to effectively separate olefins (ethylene and propylene) from paraffins (ethane and propane). This unique feature of CMS materials enables advanced hybrid membrane-distillation process designs. By using the olefins-selective membranes, these new processes may provide advantages over previously proposed retrofitting concepts. Further applications of the membranes are explored for hydrocarbons processes. Significant energy savings and even reduced footprint may be achieved in olefins production units. © 2012 Elsevier B.V.

  13. An Economical, Highly Efficient and Recyclable Catalyst System for Asymmetric Dihydroxylation of Olefins

    Institute of Scientific and Technical Information of China (English)

    金瑛; 孙晓莉; 姜茹; 张生勇

    2005-01-01

    A reusable cinchona alkaloid derivative ligand, which could be easily synthesized by two step transformation with cheap 3,6-dichloropyridazine and quinine as materials, was applied to homogeneous asymmetric dihydroxylation of olefins with NMO as co-oxidant in Me2CO-H20 system and the products could be extracted with Et2O from the recyclable catalyst system. 80%---93% yield and 51%-99% ee have been obtained. When trans-stilbene was chosen as the substrate for recycling experiment, 88%-92% yield and >99% ee have been obtained for ten recycles.

  14. Asymmetric Hydroformylation of Olefins Catalyzed by a Chiral Diphosphite-Rhodium Complex

    Institute of Scientific and Technical Information of China (English)

    YAN, Ming(鄢明); LI, Xing-Shu(黎星术); CHAN, Albert Sun-Chi(陈新滋)

    2004-01-01

    A C2-symmetrical aryl diphosphite derived from chiral binaphthol was prepared and its rhodium complex was used as catalysts in the asymmetric hydroformylation of olefins. High catalytic activity and good regioselectivity were observed. Up to 31.2% ee and 38.1% ee were achieved for the hydroformylation of 4-fluoro-styrene and vinyl acetate respectively. The influences of ligand-to-metal ratio, reaction temperature and the pressure of syn-gas on the enantioselectivity and regioselectivity were also studied.

  15. A highly efficient and recoverable bi-cinchona alkaloid ligand for the catalytic asymmetric aminohydroxylation of olefins

    Directory of Open Access Journals (Sweden)

    SHENGYONG ZHANG

    2006-10-01

    Full Text Available A new freely recyclable bi-cinchona alkaloid ligand has been developed for the homogeneous catalytic asymmetric aminohydroxylation (AA of olefins. It can be easily recovered by precipitation and reused for 5 times without any significant loss in its catalytic efficiency in AA reactions.

  16. Asymmetric Synthesis of (-)-Incarvillateine Employing an Intramolecular Alkylation via Rh-Catalyzed Olefinic C-H Bond Activation

    Energy Technology Data Exchange (ETDEWEB)

    Tsai, Andy; Bergman, Robert; Ellman, Jonathan

    2008-02-18

    An asymmetric total synthesis of (-)-incarvillateine, a natural product having potent analgesic properties, has been achieved in 11 steps and 15.4% overall yield. The key step is a rhodium-catalyzed intramolecular alkylation of an olefinic C-H bond to set two stereocenters. Additionally, this transformation produces an exocyclic, tetrasubstituted alkene through which the bicyclic piperidine moiety can readily be accessed.

  17. Synthesis of Gabosine A and N from Ribose by the Use of Ring-Closing Metathesis

    DEFF Research Database (Denmark)

    Monrad, Rune Nygaard; Fanefjord, Mette; Hansen, Flemming Gundorph;

    2009-01-01

    -methylallyl bromide. The functionalized octa-1,7-diene, thus obtained, is converted into the six-membered gabosine skeleton by ring-closing olefin metathesis. Subsequent protective group manipulations and oxidation gives rise to gabosine N in a total of 8 steps from ribose while the synthesis of gabosine...

  18. Preparation of Mesoporous SBA-16 Silica-Supported Biscinchona Alkaloid Ligand for the Asymmetric Dihydroxylation of Olefins

    Directory of Open Access Journals (Sweden)

    Shaheen M. Sarkar

    2014-01-01

    Full Text Available Optically active cinchona alkaloid was anchored onto mesoporous SBA-16 silica and the as-prepared complex was used as a heterogeneous chiral ligand of osmium tetraoxide for the asymmetric dihydroxylation of olefins. The prepared catalytic system provided 90–93% yield of vicinal diol with 92–99% enantioselectivity. The ordered mesoporous SBA-16 silica was found to be a valuable support for the cinchona alkaloid liganded osmium catalyst system which is frequently used in chemical industries and research laboratories for olefin functionalization.

  19. Tandem Ring-Opening-Ring-Closing Metathesis for Functional Metathesis Catalysts.

    Science.gov (United States)

    Nagarkar, Amit A; Yasir, Mohammad; Crochet, Aurelien; Fromm, Katharina M; Kilbinger, Andreas F M

    2016-09-26

    Use of a tandem ring-opening-ring-closing metathesis (RORCM) strategy for the synthesis of functional metathesis catalysts is reported. Ring opening of 7-substituted norbornenes and subsequent ring-closing metathesis forming a thermodynamically stable 6-membered ring lead to a very efficient synthesis of new catalysts from commercially available Grubbs' catalysts. Hydroxy functionalized Grubbs' first- as well as third-generation catalysts have been synthesized. Mechanistic studies have been performed to elucidate the order of attack of the olefinic bonds. This strategy was also used to synthesize the ruthenium methylidene complex.

  20. Enantioselective olefin metathesis with cyclometalated ruthenium complexes.

    Science.gov (United States)

    Hartung, John; Dornan, Peter K; Grubbs, Robert H

    2014-09-17

    The success of enantioselective olefin metathesis relies on the design of enantioenriched alkylidene complexes capable of transferring stereochemical information from the catalyst structure to the reactants. Cyclometalation of the NHC ligand has proven to be a successful strategy to incorporate stereogenic atoms into the catalyst structure. Enantioenriched complexes incorporating this design element catalyze highly Z- and enantioselective asymmetric ring opening/cross metathesis (AROCM) of norbornenes and cyclobutenes, and the difference in ring strain between these two substrates leads to different propagating species in the catalytic cycle. Asymmetric ring closing metathesis (ARCM) of a challenging class of prochiral trienes has also been achieved. The extent of reversibility and effect of reaction setup was also explored. Finally, promising levels of enantioselectivity in an unprecedented Z-selective asymmetric cross metathesis (ACM) of a prochiral 1,4-diene was demonstrated.

  1. Enantioselective Olefin Metathesis with Cyclometalated Ruthenium Complexes

    Science.gov (United States)

    2015-01-01

    The success of enantioselective olefin metathesis relies on the design of enantioenriched alkylidene complexes capable of transferring stereochemical information from the catalyst structure to the reactants. Cyclometalation of the NHC ligand has proven to be a successful strategy to incorporate stereogenic atoms into the catalyst structure. Enantioenriched complexes incorporating this design element catalyze highly Z- and enantioselective asymmetric ring opening/cross metathesis (AROCM) of norbornenes and cyclobutenes, and the difference in ring strain between these two substrates leads to different propagating species in the catalytic cycle. Asymmetric ring closing metathesis (ARCM) of a challenging class of prochiral trienes has also been achieved. The extent of reversibility and effect of reaction setup was also explored. Finally, promising levels of enantioselectivity in an unprecedented Z-selective asymmetric cross metathesis (ACM) of a prochiral 1,4-diene was demonstrated. PMID:25137310

  2. Syntheses of 3,4-benzotropolones by ring-closing metatheses.

    Science.gov (United States)

    Arican, Deniz; Brückner, Reinhard

    2013-06-01

    Ortho-lithiated styrenes or ortho-lithiated benzaldehyde dimethyl acetals were added to 2,2-dimethoxypent-4-enals 7. The resulting alcohols were carried on to the aromatic dienones 10. These were ring-closed by olefin metathesis. Hydrolysis of the dimethyl ketal moiety and enolization provided the 3,4-benzotropolones 5. Overall, this access comprises 4-6 steps and totaled a 22-81% yield.

  3. Kinetically E-selective macrocyclic ring-closing metathesis

    Science.gov (United States)

    Shen, Xiao; Nguyen, Thach T.; Koh, Ming Joo; Xu, Dongmin; Speed, Alexander W. H.; Schrock, Richard R.; Hoveyda, Amir H.

    2017-01-01

    Macrocyclic compounds are central to the development of new drugs, but preparing them can be challenging because of the energy barrier that must be surmounted in order to bring together and fuse the two ends of an acyclic precursor such as an alkene (also known as an olefin). To this end, the catalytic process known as ring-closing metathesis (RCM) has allowed access to countless biologically active macrocyclic organic molecules, even for large-scale production. Stereoselectivity is often critical in such cases: the potency of a macrocyclic compound can depend on the stereochemistry of its alkene; alternatively, one isomer of the compound can be subjected to stereoselective modification (such as dihydroxylation). Kinetically controlled Z-selective RCM reactions have been reported, but the only available metathesis approach for accessing macrocyclic E-olefins entails selective removal of the Z-component of a stereoisomeric mixture by ethenolysis, sacrificing substantial quantities of material if E/Z ratios are near unity. Use of ethylene can also cause adventitious olefin isomerization—a particularly serious problem when the E-alkene is energetically less favoured. Here, we show that dienes containing an E-alkenyl–B(pinacolato) group, widely used in catalytic cross-coupling, possess the requisite electronic and steric attributes to allow them to be converted stereoselectively to E-macrocyclic alkenes. The reaction is promoted by a molybdenum monoaryloxide pyrrolide complex and affords products at a yield of up to 73 per cent and an E/Z ratio greater than 98/2. We highlight the utility of the approach by preparing recifeiolide (a 12-membered-ring antibiotic) and pacritinib (an 18-membered-ring enzyme inhibitor), the Z-isomer of which is less potent than the E-isomer. Notably, the 18-membered-ring moiety of pacritinib—a potent anti-cancer agent that is in advanced clinical trials for treating lymphoma and myelofibrosis—was prepared by RCM carried out at a

  4. Axially chiral macrocyclic E-alkene bearing bisazole component formed by sequential C-H homocoupling and ring-closing metathesis.

    Science.gov (United States)

    Nishio, Shotaro; Somete, Takashi; Sugie, Atsushi; Kobayashi, Tohru; Yaita, Tsuyoshi; Mori, Atsunori

    2012-05-18

    Clipping by ring-closing metathesis freezes rotation of a C-C bond to result in forming axial chirality. Treatment of bisbenzimidazole bearing an N-(3-butenyl) substituent with a Grubbs' catalyst undergoes ring-closing metathesis, in which the stereochemistry of the thus formed olefin was exclusively E-form. Analysis by HPLC with a chiral stationary column confirmed clear baseline separation of each enantiomer.

  5. Preparation of MCM-41-supported chiral Salen Mn (Ⅲ) catalysts and their catalytic properties in the asymmetric epoxidation of olefins

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A secondary amino-modified mesoporous molecular sieve MCM-41 was obtained by reaction of bis(3-(triethoxysilyl)propyl)amine with MCM-41. The chiral Salen-Mn (Ⅲ) complex was anchored onto the modified MCM-41 by a multi-step grafting method and two heterogenized catalysts with different Mn contents were obtained. The catalysts were characterized by XRD, N2 adsorption, ICP, FT-IR and DR UV-Vis. Their catalysis on asymmetric epoxidation of several olefins was studied with NaClO and m-CPBA as oxidants respectively. It was found that both the activity and enantioselectivity of the catalysts decreased after the homogeneous catalyst was heterogenized. The reasons resulting in the decrease of catalytic performance were discussed.

  6. Mechanochemical ruthenium-catalyzed olefin metathesis.

    Science.gov (United States)

    Do, Jean-Louis; Mottillo, Cristina; Tan, Davin; Štrukil, Vjekoslav; Friščić, Tomislav

    2015-02-25

    We describe the development of a mechanochemical approach for Ru-catalyzed olefin metathesis, including cross-metathesis and ring-closing metathesis. The method uses commercially available catalysts to achieve high-yielding, rapid, room-temperature metathesis of solid or liquid olefins on a multigram scale using either no or only a catalytic amount of a liquid.

  7. Asymmetric Epoxidation of Terminal Olefins with Binaphthyl Strapped Porphyrin Catalysts: π-π Stacking Interaction and Steric Effects on the Enantioselectivities

    Institute of Scientific and Technical Information of China (English)

    REN,Qizhi; WANG,Aiqing; LIU,Shuangyan; DING,XIaojian

    2009-01-01

    Two binaphthyl strapped porphyrins with similar chiral auxiliaries 1b and 2b were used as efficient catalysts for asymmetric epoxidation of both styrene derivatives and non-aromatic olefin substrates. Theoretical calculation of styrene approach to both catalysts has been performed. The subtle difference of the chiral cavities between two por-phyrins has been analyzed by 1H NMR. The π-π stacking interaction between aromatic substrates and catalysts might be one factor for the dramatic different enantioselectivities. Besides, the steric effect of the binaphthyl handle of lb and 2b also causes the high ee values for non-aromatic olefin epoxidations.

  8. Recent applications of ring-closing metathesis in the synthesis of lactams and macrolactams.

    Science.gov (United States)

    Hassan, Hani Mutlak A

    2010-12-28

    Lactams are an important class of compounds owing to their presence in numerous biologically active molecules of natural and unnatural nature. They are also highly versatile intermediates that can be elaborated into interesting compounds for potential use in organic and medicinal chemistry endeavors. In this feature article, the reader will be given a background to olefin metathesis followed by concise discussions (with selected examples) to report recent applications of ring-closing metathesis to form lactams and macrolactams from acyclic diene precursors, an area which continues to deposit attractive applications in the chemical literature en route or in the final step to the target molecules.

  9. Ruthenium Olefin Metathesis Catalysts Bearing Carbohydrate-Based N-Heterocyclic Carbenes

    Science.gov (United States)

    Keitz, Benjamin K.; Grubbs, Robert H.

    2010-01-01

    Ru-based olefin metathesis catalysts containing carbohydrate-derived NHCs from glucose and galactose were synthesized and characterized by NMR spectroscopy. 2D-NMR spectroscopy revealed the presence of Ru-C (benzylidene) rotamers at RT and the rate of rotation was measured using magnetization transfer and VT-NMR spectroscopy. The catalysts were found to be effective at ring-opening metathesis polymerization (ROMP), ring closing metathesis (RCM), cross metathesis (CM), and asymmetric ring opening cross metathesis (AROCM) and showed surprising selectivity in both CM and AROCM. PMID:21603126

  10. Total Synthesis and Stereochemical Assignment of Delavatine A: Rh-Catalyzed Asymmetric Hydrogenation of Indene-Type Tetrasubstituted Olefins and Kinetic Resolution through Pd-Catalyzed Triflamide-Directed C-H Olefination.

    Science.gov (United States)

    Zhang, Zhongyin; Wang, Jinxin; Li, Jian; Yang, Fan; Liu, Guodu; Tang, Wenjun; He, Weiwei; Fu, Jian-Jun; Shen, Yun-Heng; Li, Ang; Zhang, Wei-Dong

    2017-03-08

    Delavatine A (1) is a structurally unusual isoquinoline alkaloid isolated from Incarvillea delavayi. The first and gram-scale total synthesis of 1 was accomplished in 13 steps (the longest linear sequence) from commercially available starting materials. We exploited an isoquinoline construction strategy and developed two reactions, namely Rh-catalyzed asymmetric hydrogenation of indene-type tetrasubstituted olefins and kinetic resolution of β-alkyl phenylethylamine derivatives through Pd-catalyzed triflamide-directed C-H olefination. The substrate scope of the first reaction covered unfunctionalized olefins and those containing polar functionalities such as sulfonamides. The kinetic resolution provided a collection of enantioenriched indane and tetralin-based triflamides, including those bearing quaternary chiral centers. The selectivity factor (s) exceeded 100 for a number of substrates. These reactions enabled two different yet related approaches to a key intermediate 28 in excellent enantiopurity. In the synthesis, the triflamide served as not only an effective directing group for C-H bond activation but also a versatile functional group for further elaborations. The relative and absolute configurations of delavatine A were unambiguously assigned by the syntheses of the natural product and its three stereoisomers. Their cytotoxicity against a series of cancer cell lines were evaluated.

  11. Synthesis of Calystegine A(3) from Glucose by the Use of Ring-Closing Metathesis

    DEFF Research Database (Denmark)

    Monrad, Rune Nygaard; Pipper, Charlotte Bressen; Madsen, Robert

    2009-01-01

    A synthesis of the nortropane alkaloid calystegine A(3) is described from D-glucose. The key step employs a zinc-mediated tandem reaction where a benzyl-protected methyl 6-iodo glucoside is fragmented to give an unsaturated aldehyde, which is then transformed into the corresponding benzylimine...... and allylated in the same pot. The functionalized nona-1,8-diene, thus obtained, is converted into the seven-membered carbon skeleton in calystegine A(3) by ring-closing olefin metathesis. Subsequent deoxygenation by the Barton-McCombie protocol, hydroboration and oxidative workup followed by hydrogenolysis...... affords calystegine A(3). The synthesis uses a total of 13 steps from glucose and confirms the absolute configuration of the natural product....

  12. Light-induced olefin metathesis

    Directory of Open Access Journals (Sweden)

    Yuval Vidavsky

    2010-11-01

    Full Text Available Light activation is a most desirable property for catalysis control. Among the many catalytic processes that may be activated by light, olefin metathesis stands out as both academically motivating and practically useful. Starting from early tungsten heterogeneous photoinitiated metathesis, up to modern ruthenium methods based on complex photoisomerisation or indirect photoactivation, this survey of the relevant literature summarises past and present developments in the use of light to expedite olefin ring-closing, ring-opening polymerisation and cross-metathesis reactions.

  13. Light-induced olefin metathesis

    Science.gov (United States)

    Vidavsky, Yuval

    2010-01-01

    Summary Light activation is a most desirable property for catalysis control. Among the many catalytic processes that may be activated by light, olefin metathesis stands out as both academically motivating and practically useful. Starting from early tungsten heterogeneous photoinitiated metathesis, up to modern ruthenium methods based on complex photoisomerisation or indirect photoactivation, this survey of the relevant literature summarises past and present developments in the use of light to expedite olefin ring-closing, ring-opening polymerisation and cross-metathesis reactions. PMID:21160912

  14. Catenation through a Combination of Radical Templation and Ring-Closing Metathesis.

    Science.gov (United States)

    Gibbs-Hall, Ian C; Vermeulen, Nicolaas A; Dale, Edward J; Henkelis, James J; Blackburn, Anthea K; Barnes, Jonathan C; Stoddart, J Fraser

    2015-12-23

    Synthesis of an electrochemically addressable [2]catenane has been achieved following formation by templation of a [2]pseudorotaxane employing radically enhanced molecular recognition between the bisradical dication obtained on reduction of the tetracationic cyclophane, cyclobis(paraquat-p-phenylene), and the radical cation generated on reduction of a viologen disubstituted with p-xylylene units, both carrying tetraethylene glycol chains terminated by allyl groups. This inclusion complex was subjected to olefin ring-closing metathesis, which was observed to proceed under reduced conditions, to mechanically interlock the two components. Upon oxidation, Coulombic repulsion between the positively charged and mechanically interlocked components results in the adoption of a co-conformation where the newly formed alkene resides inside the cavity of the tetracationic cyclophane. (1)H NMR spectroscopic analysis of this hexacationic [2]catenane shows a dramatic upfield shift of the resonances associated with the olefinic and allylic protons as a result of them residing inside the tetracationic component. Further analysis shows high diastereoselectivity during catenation, as only a single (Z)-isomer is formed.

  15. On the relationship between structure and reaction rate in olefin ring-closing metathesis.

    Science.gov (United States)

    Ashworth, Ian W; Carboni, Davide; Hillier, Ian H; Nelson, David J; Percy, Jonathan M; Rinaudo, Giuseppe; Vincent, Mark A

    2010-10-14

    In the RCM reactions of a series of simple α,ω-dienes, the relative order of reactivity has been unambiguously determined showing that cyclohexene forms faster than cyclopentene or cycloheptene. 1,5-Hexadiene inhibits the RCM of 1,7-octadiene; 1,5-hexadiene cannot progress to the RCM product (cyclobutene) but forms an unexpectedly stable cyclic η(2)-complex.

  16. Tandem ring-opening/ring-closing metathesis polymerization: relationship between monomer structure and reactivity.

    Science.gov (United States)

    Park, Hyeon; Lee, Ho-Keun; Choi, Tae-Lim

    2013-07-24

    Monomers containing either cycloalkenes with low ring strain or 1-alkynes are poor monomers for olefin metathesis polymerization. Ironically, keeping two inactive functional groups in proximity within one molecule can make it an excellent monomer for metathesis polymerization. Recently, we demonstrated that monomer 1 having cyclohexene and propargyl moieties underwent rapid tandem ring-opening/ring-closing metathesis (RO/RCM) polymerization via relay-type mechanism. Furthermore, living polymerization was achieved when a third-generation Grubbs catalyst was used. Here, we present a full account on this tandem polymerization by investigating how various structural modifications of the monomers affected the reactivity of the tandem polymerization. We observed that changing the ring size of the cycloalkene moieties, the length of the alkynes, and linker units influenced not only the polymerization rates but also the reactivities of Diels-Alder reaction, which is a post-modification reaction of the resulting polymers. Also, the mechanism of tandem polymerization was studied by conducting end-group analysis using (1)H NMR analysis, thereby concluding that the polymerization occurred by the alkyne-first pathway. With this mechanistic conclusion, factors responsible for the dramatic structure-reactivity relationship were proposed. Lastly, tandem RO/RCM polymerization of monomers containing sterically challenging trisubstituted cycloalkenes was successfully carried out to give polymer repeat units having tetrasubstituted cycloalkenes.

  17. Nonproductive events in ring-closing metathesis using ruthenium catalysts.

    Science.gov (United States)

    Stewart, Ian C; Keitz, Benjamin K; Kuhn, Kevin M; Thomas, Renee M; Grubbs, Robert H

    2010-06-30

    The relative TONs of productive and nonproductive metathesis reactions of diethyl diallylmalonate are compared for eight different ruthenium-based catalysts. Nonproductive cross metathesis is proposed to involve a chain-carrying ruthenium methylidene. A second more-challenging substrate (dimethyl allylmethylallylmalonate) that forms a trisubstituted olefin product is used to further delineate the effect of catalyst structure on the relative efficiencies of these processes. A steric model is proposed to explain the observed trends.

  18. Olefin metathesis in nano-sized systems

    Directory of Open Access Journals (Sweden)

    Denise Méry

    2011-01-01

    Full Text Available The interplay between olefin metathesis and dendrimers and other nano systems is addressed in this mini review mostly based on the authors’ own contributions over the last decade. Two subjects are presented and discussed: (i The catalysis of olefin metathesis by dendritic nano-catalysts via either covalent attachment (ROMP or, more usefully, dendrimer encapsulation – ring closing metathesis (RCM, cross metathesis (CM, enyne metathesis reactions (EYM – for reactions in water without a co-solvent and (ii construction and functionalization of dendrimers by CM reactions.

  19. Olefin metathesis in nano-sized systems

    Science.gov (United States)

    Diallo, Abdou K; Gatard, Sylvain; Liang, Liyuan; Ornelas, Cátia; Martinez, Victor; Méry, Denise; Ruiz, Jaime

    2011-01-01

    Summary The interplay between olefin metathesis and dendrimers and other nano systems is addressed in this mini review mostly based on the authors’ own contributions over the last decade. Two subjects are presented and discussed: (i) The catalysis of olefin metathesis by dendritic nano-catalysts via either covalent attachment (ROMP) or, more usefully, dendrimer encapsulation – ring closing metathesis (RCM), cross metathesis (CM), enyne metathesis reactions (EYM) – for reactions in water without a co-solvent and (ii) construction and functionalization of dendrimers by CM reactions. PMID:21286399

  20. Halide exchanged Hoveyda-type complexes in olefin metathesis

    Directory of Open Access Journals (Sweden)

    Julia Wappel

    2010-11-01

    Full Text Available The aims of this contribution are to present a straightforward synthesis of 2nd generation Hoveyda-type olefin metathesis catalysts bearing bromo and iodo ligands, and to disclose the subtle influence of the different anionic co-ligands on the catalytic performance of the complexes in ring opening metathesis polymerisation, ring closing metathesis, enyne cycloisomerisation and cross metathesis reactions.

  1. Halide exchanged Hoveyda-type complexes in olefin metathesis

    Science.gov (United States)

    Wappel, Julia; Urbina-Blanco, César A; Abbas, Mudassar; Albering, Jörg H; Saf, Robert; Nolan, Steven P

    2010-01-01

    Summary The aims of this contribution are to present a straightforward synthesis of 2nd generation Hoveyda-type olefin metathesis catalysts bearing bromo and iodo ligands, and to disclose the subtle influence of the different anionic co-ligands on the catalytic performance of the complexes in ring opening metathesis polymerisation, ring closing metathesis, enyne cycloisomerisation and cross metathesis reactions. PMID:21160566

  2. Ruthenium-based four-coordinate olefin metathesis catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Sanford, M.S.; Henling, L.M.; Day, M.W.; Grubbs, R.H. [California Inst. of Tech., Pasadena (United States). Div. of Chemistry and Chemical Engineering

    2000-10-02

    A series of four-coordinate Ru{sup II} alkylidenes has been prepared as analogues of the proposed olefin metathesis intermediate [(PCy{sub 3})Cl{sub 2}Ru=CHPh]. These complexes exhibit unusual trigonal-pyramidal solid-state geometries, and are rendered highly active for ring-closing metathesis by the addition of HCl. (orig.)

  3. Transition metal complexes of oxazolinylboranes and cyclopentadienyl-bis(oxazolinyl)borates: Catalysts for asymmetric olefin hydroamination and acceptorless alcohol decarbonylation

    Energy Technology Data Exchange (ETDEWEB)

    Manna, Kuntal [Ames Lab., Ames, IA (United States)

    2012-12-17

    The research presented and discussed in this dissertation involves the synthesis of transition metal complexes of oxazolinylboranes and cyclopentadienyl-bis(oxazolinyl)borates, and their application in catalytic enantioselective olefin hydroamination and acceptorless alcohol decarbonylation. Neutral oxazolinylboranes are excellent synthetic intermediates for preparing new borate ligands and also developing organometallic complexes. Achiral and optically active bis(oxazolinyl)phenylboranes are synthesized by reaction of 2-lithio-2-oxazolide and 0.50 equiv of dichlorophenylborane. These bis(oxazolinyl)phenylboranes are oligomeric species in solid state resulting from the coordination of an oxazoline to the boron center of another borane monomer. The treatment of chiral bis(oxazolinyl)phenylboranes with sodium cyclopentadienide provide optically active cyclopentadienyl-bis(oxazolinyl)borates H[PhB(C5H5)(OxR)2] [OxR = Ox4S-iPr,Me2, Ox4R-iPr,Me2, Ox4S-tBu]. These optically active proligands react with an equivalent of M(NMe2)4 (M = Ti, Zr, Hf) to afford corresponding cyclopentadienyl-bis(oxazolinyl)borato group 4 complexes {PhB(C5H4)(OxR)2}M(NMe2)2 in high yields. These group 4 compounds catalyze cyclization of aminoalkenes at room temperature or below, providing pyrrolidine, piperidine, and azepane with enantiomeric excesses up to 99%. Our mechanistic investigations suggest a non-insertive mechanism involving concerted C-N/C-H bond formation in the turnover limiting step of the catalytic cycle. Among cyclopentadienyl-bis(oxazolinyl)borato group 4 catalysts, the zirconium complex {PhB(C5H4)(Ox4S-iPr,Me2)2}Zr(NMe2)2 ({S-2}Zr(NMe2)2) displays highest activity and enantioselectivity. Interestingly, S-2

  4. Full ring closing in a diarylethene hexamer : insights from theory

    NARCIS (Netherlands)

    Perrier, Aurelie; Maurel, Francois; Browne, Wesley R.; Jacquemin, Denis

    2013-01-01

    First principle simulations of an extended hexameric molecular switch are reported. The full switching of the system is explained by investigating the nature of the excited states of all possible isomers. A new multi-addressable asymmetric structure is proposed.

  5. Ring-closing metathesis reactions: interpretation of conversion-time data.

    Science.gov (United States)

    Thiel, Vasco; Wannowius, Klaus-Jürgen; Wolff, Christiane; Thiele, Christina M; Plenio, Herbert

    2013-11-25

    Conversion-time data were recorded for various ring-closing metathesis (RCM) reactions that lead to five- or six-membered cyclic olefins by using different precatalysts of the Hoveyda type. Slowly activated precatalysts were found to produce more RCM product than rapidly activated complexes, but this comes at the price of slower product formation. A kinetic model for the analysis of the conversion-time data was derived, which is based on the conversion of the precatalyst (Pcat) into the active species (Acat), with the rate constant k(act), followed by two parallel reactions: 1) the catalytic reaction, which utilizes Acat to convert reactants into products, with the rate k(cat), and 2) the conversion of Acat into the inactive species (Dcat), with the rate k(dec). The calculations employ two experimental parameters: the concentration of the substrate (c(S)) at a given time and the rate of substrate conversion (-dc(S)/dt). This provides a direct measure of the concentration of Acat and enables the calculation of the pseudo-first-order rate constants k(act), k(cat), and k(dec) and of k(S) (for the RCM conversion of the respective substrate by Acat). Most of the RCM reactions studied with different precatalysts are characterized by fast k(cat) rates and by the k(dec) value being greater than the k(act) value, which leads to quasistationarity for Acat. The active species formed during the activation step was shown to be the same, regardless of the nature of different Pcats. The decomposition of Acat occurs along two parallel pathways, a unimolecular (or pseudo-first-order) reaction and a bimolecular reaction involving two ruthenium complexes. Electron-deficient precatalysts display higher rates of catalyst deactivation than their electron-rich relatives. Slowly initiating Pcats act as a reservoir, by generating small stationary concentrations of Acat. Based on this, it can be understood why the use of different precatalysts results in different substrate conversions in

  6. Transition metal complexes of oxazolinylboranes and cyclopentadienyl-bis(oxazolinyl)borates: Catalysts for asymmetric olefin hydroamination and acceptorless alcohol decarbonylation

    Energy Technology Data Exchange (ETDEWEB)

    Manna, Kuntal [Ames Lab., Ames, IA (United States)

    2012-12-17

    The research presented and discussed in this dissertation involves the synthesis of transition metal complexes of oxazolinylboranes and cyclopentadienyl-bis(oxazolinyl)borates, and their application in catalytic enantioselective olefin hydroamination and acceptorless alcohol decarbonylation. Neutral oxazolinylboranes are excellent synthetic intermediates for preparing new borate ligands and also developing organometallic complexes. Achiral and optically active bis(oxazolinyl)phenylboranes are synthesized by reaction of 2-lithio-2-oxazolide and 0.50 equiv of dichlorophenylborane. These bis(oxazolinyl)phenylboranes are oligomeric species in solid state resulting from the coordination of an oxazoline to the boron center of another borane monomer. The treatment of chiral bis(oxazolinyl)phenylboranes with sodium cyclopentadienide provide optically active cyclopentadienyl-bis(oxazolinyl)borates H[PhB(C5H5)(OxR)2] [OxR = Ox4S-iPr,Me2, Ox4R-iPr,Me2, Ox4S-tBu]. These optically active proligands react with an equivalent of M(NMe2)4 (M = Ti, Zr, Hf) to afford corresponding cyclopentadienyl-bis(oxazolinyl)borato group 4 complexes {PhB(C5H4)(OxR)2}M(NMe2)2 in high yields. These group 4 compounds catalyze cyclization of aminoalkenes at room temperature or below, providing pyrrolidine, piperidine, and azepane with enantiomeric excesses up to 99%. Our mechanistic investigations suggest a non-insertive mechanism involving concerted C-N/C-H bond formation in the turnover limiting step of the catalytic cycle. Among cyclopentadienyl-bis(oxazolinyl)borato group 4 catalysts, the zirconium complex {PhB(C5H4)(Ox4S-iPr,Me2)2}Zr(NMe2)2 ({S-2}Zr(NMe2)2) displays highest activity and enantioselectivity. Interestingly, S-2

  7. Phosphate Tether-Mediated Ring-Closing Metathesis for the Generation of P-Stereogenic, Z-Configured Bicyclo[7.3.1]- and Bicyclo[8.3.1]phosphates.

    Science.gov (United States)

    Markley, Jana L; Maitra, Soma; Hanson, Paul R

    2016-02-05

    A phosphate tether-mediated ring-closing metathesis (RCM) study to the synthesis of Z-configured, P-stereogenic bicyclo[7.3.1]- and bicyclo[8.3.1]phosphates is reported. Investigations suggest that C3-substitution, olefin substitution, and proximity of the forming olefin to the bridgehead carbon of the bicyclic affect the efficiency and stereochemical outcome of the RCM event. This study demonstrates the utility of phosphate tether-mediated desymmetrization of C2-symmetric, 1,3-anti-diol-containing dienes in the generation of macrocyclic phosphates with potential synthetic and biological utility.

  8. The Olefin Metathesis Reactions in Dendrimers

    Science.gov (United States)

    Astruc, Didier

    Dendrimers containing terminal olefins or ruthenium-benzylidene terminal groups undergo olefin metathesis reactions (RCM and ROMP types), and essentially results from our group are reviewed here. Dendrimers have been loaded at their periphery with ruthenium-chelating bis-phosphines, which leads to the formation of dendrimer-cored stars by ring-opening-metathesis polymerization (ROMP). CpFe+-induced perallylation of polymethylaromatics (Cp = η5-C5H5) followed by ring-closing metathesis (RCM) and/or cross metathesis (CM) leads to poly-ring, cage, oligomeric and polymeric architectures. In the presence of acrylic acid or metha-crylate, stereospecific CM inhibits oligomerization, and dendritic olefins yield polyacid dendrimers. Finally, cros-metahesis reactions with dendronic acrylate allow dendritic construction and growth.

  9. Target Specific Tactics in Olefin Metathesis: Synthetic Approach to cis-syn-cis-Triquinanes and -Propellanes.

    Science.gov (United States)

    Kotha, Sambasivarao; Aswar, Vikas R

    2016-04-15

    A concise and simple synthetic approach to cis-syn-cis-triquinanes and -propellanes has been demonstrated via olefin metathesis starting with exo-nadic anhydride. This approach involves a ring-opening and ring-closing metathesis sequence of norbornene derivatives using Grubb's catalyst. Early-stage diallylation of norbornene derivatives is demonstrated followed by ring-closing metathesis that delivers propellanes exclusively. Surprisingly, ring-opening metathesis, late-stage diallylation, followed by ring-closing metathesis delivers triquinane as well as propellane derivatives.

  10. Ruthenium olefin metathesis catalysts featuring unsymmetrical N-heterocyclic carbenes.

    Science.gov (United States)

    Paradiso, Veronica; Bertolasi, Valerio; Costabile, Chiara; Grisi, Fabia

    2016-01-14

    New ruthenium Grubbs' and Hoveyda-Grubbs' second generation catalysts bearing N-alkyl/N-isopropylphenyl N-heterocyclic carbene (NHC) ligands with syn or anti backbone configuration were obtained and compared in model olefin metathesis reactions. Different catalytic efficiencies were observed depending on the size of the N-alkyl group (methyl or cyclohexyl) and on the backbone configuration. The presence of an N-cyclohexyl substituent determined the most significant reactivity differences between catalysts with syn or anti phenyl groups on the backbone. In particular, anti catalysts proved highly efficient, especially in the ring-closing metathesis (RCM) of encumbered diolefins, while syn catalysts showed low efficiency in the RCM of less hindered diolefins. This peculiar behavior, rationalized through DFT studies, was found to be related to the high propensity of these catalysts to give nonproductive metathesis events. Enantiopure anti catalysts were also tested in asymmetric metathesis reactions, where moderate enantioselectivities were observed. The steric and electronic properties of unsymmetrical NHCs with the N-cyclohexyl group were then evaluated using the corresponding rhodium complexes. While steric factors proved unimportant for both syn and anti NHCs, a major electron-donating character was found for the unsymmetrical NHC with anti phenyl substituents on the backbone.

  11. Olefin Metathesis for Chemical Biology

    Science.gov (United States)

    Binder, Joseph B; Raines, Ronald T

    2009-01-01

    Summary Chemical biology relies on effective synthetic chemistry for building molecules to probe and modulate biological function. Olefin metathesis in organic solvents is a valuable addition to this armamentarium, and developments during the previous decade are enabling metathesis in aqueous solvents for the manipulation of biomolecules. Functional group-tolerant ruthenium metathesis catalysts modified with charged moieties or hydrophilic polymers are soluble and active in water, enabling ring-opening metathesis polymerization, cross metathesis, and ring-closing metathesis. Alternatively, conventional hydrophobic ruthenium complexes catalyze a similar array of metathesis reactions in mixtures of water and organic solvents. This strategy has enabled cross metathesis on the surface of a protein. Continuing developments in catalyst design and methodology will popularize the bioorthogonal reactivity of metathesis. PMID:18935975

  12. Ruthenium-Aryloxide Catalysts for Olefin Metathesis

    Science.gov (United States)

    Monfette, Sebastien; Blacquiere, Johanna M.; Conrad, Jay C.; Beach, Nicholas J.; Fogg, Deryn E.

    : Advances in design of ruthenium aryloxide catalysts for olefin metathesis are described. The target complexes are accessible on reaction of RuCl2(NHC)(py)2 (CHPh) (NHC - N-heterocyclic carbene) with electron-deficient, monodentate aryl- oxides, or aryloxides that yield small, rigid chelate rings. The best of these catalysts offer activity comparable to or greater than that of the parent chloride (Grubbs) systems in ring-closing metathesis (RCM). Preliminary studies of the electronic nature of the Ru-X bond suggest that the metal center is more electropositive in the aryloxide complexes than in the Grubbs systems.

  13. Reactivation of a Ruthenium-Based Olefin Metathesis Catalyst

    Science.gov (United States)

    Tabari, Daniel S.; Tolentino, Daniel R.; Schrodi, Yann

    2013-01-01

    1st Generation Hoveyda-Grubbs olefin metathesis catalyst was purposely decomposed in the presence of ethylene yielding inorganic species that are inactive in the ring-closing metathesis (RCM) of benchmark substrate diethyldiallyl malonate (DEDAM). The decomposed catalyst was treated with 1-(3,5-diisopropoxyphenyl)-1-phenylprop-2-yn-1-ol (3) to generate an olefin metathesis active ruthenium indenylidene-ether complex in 43 % yield. This complex was also prepared independently by reacting RuCl2(p-cymene)(PCy3) with organic precursor 3. The activity of the isolated reactivated catalyst in the RCM of DEDAM is similar to that of the independently prepared complex. PMID:23355756

  14. Application of olefin metathesis in the synthesis of steroids.

    Science.gov (United States)

    Morzycki, Jacek W

    2011-01-01

    Over the past decade, ruthenium-mediated metathesis transformations, including cross-metathesis, ring-closing metathesis, enyne metathesis, ring-opening metathesis polymerization, and also tandem processes, belong to the most intensively studied reactions. Many applications of olefin metathesis in the synthesis of natural products have been recently described. Also in the field of steroid chemistry new methods of total synthesis and hemisynthesis based on metathesis reactions have been elaborated. Various biologically active compounds, e.g. vitamin D and hormone analogues, steroid dimers and macrocycles, etc. have been prepared using a variety of olefin-metathesis protocols.

  15. Reactivation of a Ruthenium-Based Olefin Metathesis Catalyst.

    Science.gov (United States)

    Tabari, Daniel S; Tolentino, Daniel R; Schrodi, Yann

    2013-01-14

    1(st) Generation Hoveyda-Grubbs olefin metathesis catalyst was purposely decomposed in the presence of ethylene yielding inorganic species that are inactive in the ring-closing metathesis (RCM) of benchmark substrate diethyldiallyl malonate (DEDAM). The decomposed catalyst was treated with 1-(3,5-diisopropoxyphenyl)-1-phenylprop-2-yn-1-ol (3) to generate an olefin metathesis active ruthenium indenylidene-ether complex in 43 % yield. This complex was also prepared independently by reacting RuCl(2)(p-cymene)(PCy(3)) with organic precursor 3. The activity of the isolated reactivated catalyst in the RCM of DEDAM is similar to that of the independently prepared complex.

  16. Ring-Closing and Cross-Metathesis with Artificial Metalloenzymes Created by Covalent Active Site-Directed Hybridization of a Lipase.

    Science.gov (United States)

    Basauri-Molina, Manuel; Verhoeven, Dide G A; van Schaik, Arnoldus J; Kleijn, Henk; Klein Gebbink, Robertus J M

    2015-10-26

    A series of Grubbs-type catalysts that contain lipase-inhibiting phosphoester functionalities have been synthesized and reacted with the lipase cutinase, which leads to artificial metalloenzymes for olefin metathesis. The resulting hybrids comprise the organometallic fragment that is covalently bound to the active amino acid residue of the enzyme host in an orthogonal orientation. Differences in reactivity as well as accessibility of the active site by the functionalized inhibitor became evident through variation of the anchoring motif and substituents on the N-heterocyclic carbene ligand. Such observations led to the design of a hybrid that is active in the ring-closing metathesis and the cross-metathesis of N,N-diallyl-p-toluenesulfonamide and allylbenzene, respectively, the latter being the first example of its kind in the field of artificial metalloenzymes.

  17. Organic synthesis with olefin metathesis catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Grubbs, R.H. [California Institute of Technology, Pasadena, CA (United States)

    1995-12-31

    Over the past nine years, early transition metal catalysts for the ring opening metathesis polymerization of cyclic olefins have been developed. These catalysts are simple organometallic complexes containing metal carbon multiple bonds that in most cases polymerize olefins by a living process. These catalysts have been used to prepare a family of near monodispersed and structurally homogeneous polymers. A series of group VII ROMP catalysts that allow a wide range of functionality to be incorporated into the polymer side chains have been prepared. The most important member of this family of complexes are the bisphosphinedihalo-ruthenium carbene complexes. These polymerization catalysts can also be used in the synthesis of fine chemicals by ring closing (RCM) and vinyl coupling reactions. The availability of the group VII catalysts allow metathesis to be carried out on highly functionalized substrates such as polypeptides and in unusual environments such as in aqueous emulsions.

  18. Synthesis of anti-tumour phosphatidylinositol analogues from glucose by the use of ring-closing olefin metathesis

    DEFF Research Database (Denmark)

    Andresen, Thomas Lars; Skytte, Dorthe M.; Madsen, Robert

    2004-01-01

    -closing metathesis to afford the key conduritol B intermediate 7. This can trifurcate to form three different benzyl-protected myo-inositol headgroups 4-6, which after phosphorylation and attachment of the glycerolipid part give phosphatidylinositols 1-3. Preliminary biological testing against human colon...

  19. Ultrafast ring-closing reaction dynamics of a photochromic furan-based difurylethene

    Science.gov (United States)

    Khodko, A.; Khomenko, V.; Shynkarenko, Y.; Mamuta, O.; Kapitanchuk, O.; Sysoiev, D.; Kachalova, N.; Huhn, T.; Snegir, S.

    2017-02-01

    The ultrafast photoinduced ring-closing dynamics of a furan-based difurylethene (YnPhT) has been investigated by femtosecond transient absorption spectroscopy. We performed time-dependent density functional theory (TD-DFT) calculations to explain the experimental results in detail. The sub-picosecond time scale of the ring-closing reaction is comparable with thiophene-based analogues, but oxygen atoms at the photochromic core can avoid adverse interaction between switches and metal contacts in further applications. This observation proves that furan-based diarylethenes are potential optoelectronic elements with an ultrafast optical response.

  20. NHC Backbone Configuration in Ruthenium-Catalyzed Olefin Metathesis

    Directory of Open Access Journals (Sweden)

    Veronica Paradiso

    2016-01-01

    Full Text Available The catalytic properties of olefin metathesis ruthenium complexes bearing N-heterocyclic carbene ligands with stereogenic centers on the backbone are described. Differences in catalytic behavior depending on the backbone configurations of symmetrical and unsymmetrical NHCs are discussed. In addition, an overview on asymmetric olefin metathesis promoted by chiral catalysts bearing C2-symmetric and C1-symmetric NHCs is provided.

  1. Total Synthesis of Mycalolides A and B through Olefin Metathesis.

    Science.gov (United States)

    Kita, Masaki; Oka, Hirotaka; Usui, Akihiro; Ishitsuka, Tomoya; Mogi, Yuzo; Watanabe, Hidekazu; Tsunoda, Masaki; Kigoshi, Hideo

    2015-11-16

    An asymmetric total synthesis of the trisoxazole marine macrolides mycalolides A and B is described. This synthesis involves the convergent assembly of highly functionalized C1-C19 trisoxazole and C20-C35 side-chain segments through the use of olefin metathesis and esterification as well as Julia-Kocienski olefination and enamide formation as key steps.

  2. NHC Backbone Configuration in Ruthenium-Catalyzed Olefin Metathesis.

    Science.gov (United States)

    Paradiso, Veronica; Costabile, Chiara; Grisi, Fabia

    2016-01-20

    The catalytic properties of olefin metathesis ruthenium complexes bearing N-heterocyclic carbene ligands with stereogenic centers on the backbone are described. Differences in catalytic behavior depending on the backbone configurations of symmetrical and unsymmetrical NHCs are discussed. In addition, an overview on asymmetric olefin metathesis promoted by chiral catalysts bearing C₂-symmetric and C₁-symmetric NHCs is provided.

  3. Stereoselective Synthesis of trans-Olefins by the Copper-Mediated SN2′ Reaction of Vinyl Oxazines with Grignard Reagents. Asymmetric Synthesis of D-threo-Sphingosines

    OpenAIRE

    Singh, Om V; Han, Hyunsoo

    2007-01-01

    The SN2′ reaction of 6-vinyl-5,6-dihydro-4H-[1,3]oxazines with Grignard reagents in the presence of CuCN was studied, and high trans selectivity for the formation of double bond was observed with a variety of RMgX. The SN2′ reaction, coupled with regioselective asymmetric aminohydroxylation reaction, provided a highly efficient route for the asymmetric synthesis of D-threo-N-acetylsphingosine.

  4. Asymmetric synthesis of (-)-adaline.

    Science.gov (United States)

    Itoh, Toshimasa; Yamazaki, Naoki; Kibayashi, Chihiro

    2002-07-25

    [reaction: see text] An enantioselective total synthesis of (-)-adaline has been achieved starting from a chiral 6,6-disubstituted piperidone derivative previously prepared by diastereoselective allylation of a chiral tricyclic N-acyl-N,O-acetal. The key steps include lithium ion-activated SN2-type alkynylation of the tricyclic N,O-acetal leading to exclusive formation of the (6S)-ethynylpiperidine and ring-closing olefin metathesis of the (2R,6S)-cis-2,6-dialkenylpiperidine for constructing the bridged azabicyclononane.

  5. Iron(III)-catalysed carbonyl-olefin metathesis.

    Science.gov (United States)

    Ludwig, Jacob R; Zimmerman, Paul M; Gianino, Joseph B; Schindler, Corinna S

    2016-04-27

    The olefin metathesis reaction of two unsaturated substrates is one of the most powerful carbon-carbon-bond-forming reactions in organic chemistry. Specifically, the catalytic olefin metathesis reaction has led to profound developments in the synthesis of molecules relevant to the petroleum, materials, agricultural and pharmaceutical industries. These reactions are characterized by their use of discrete metal alkylidene catalysts that operate via a well-established mechanism. While the corresponding carbonyl-olefin metathesis reaction can also be used to construct carbon-carbon bonds, currently available methods are scarce and severely hampered by either harsh reaction conditions or the required use of stoichiometric transition metals as reagents. To date, no general protocol for catalytic carbonyl-olefin metathesis has been reported. Here we demonstrate a catalytic carbonyl-olefin ring-closing metathesis reaction that uses iron, an Earth-abundant and environmentally benign transition metal, as a catalyst. This transformation accommodates a variety of substrates and is distinguished by its operational simplicity, mild reaction conditions, high functional-group tolerance, and amenability to gram-scale synthesis. We anticipate that these characteristics, coupled with the efficiency of this reaction, will allow for further advances in areas that have historically been enhanced by olefin metathesis.

  6. Iron(III)-catalysed carbonyl-olefin metathesis

    Science.gov (United States)

    Ludwig, Jacob R.; Zimmerman, Paul M.; Gianino, Joseph B.; Schindler, Corinna S.

    2016-05-01

    The olefin metathesis reaction of two unsaturated substrates is one of the most powerful carbon-carbon-bond-forming reactions in organic chemistry. Specifically, the catalytic olefin metathesis reaction has led to profound developments in the synthesis of molecules relevant to the petroleum, materials, agricultural and pharmaceutical industries. These reactions are characterized by their use of discrete metal alkylidene catalysts that operate via a well-established mechanism. While the corresponding carbonyl-olefin metathesis reaction can also be used to construct carbon-carbon bonds, currently available methods are scarce and severely hampered by either harsh reaction conditions or the required use of stoichiometric transition metals as reagents. To date, no general protocol for catalytic carbonyl-olefin metathesis has been reported. Here we demonstrate a catalytic carbonyl-olefin ring-closing metathesis reaction that uses iron, an Earth-abundant and environmentally benign transition metal, as a catalyst. This transformation accommodates a variety of substrates and is distinguished by its operational simplicity, mild reaction conditions, high functional-group tolerance, and amenability to gram-scale synthesis. We anticipate that these characteristics, coupled with the efficiency of this reaction, will allow for further advances in areas that have historically been enhanced by olefin metathesis.

  7. Recent Advances in Rh-Catalyzed Asymmetric Hydroformylation of Olefins%铑催化的烯烃不对称氢甲酰化反应研究进展

    Institute of Scientific and Technical Information of China (English)

    贾肖飞; 王正; 夏春谷; 丁奎岭

    2013-01-01

    烯烃的氢甲酰化反应是工业上最重要的均相催化反应之一,而通过烯烃的不对称氢甲酰化反应合成光学活性醛,对于药物、农药、香料和天然产物合成方面具有重要的意义.近年来,由于铑与膦配体形成的络合物在催化烯烃的不对称氢甲酰化反应中具有反应活性高、选择性好等优点而引起广泛关注.通过调控铑络合物中手性膦配体的电子与立体化学环境,已经成为实现不对称氢甲酰化反应高活性和高选择性最主要的方法.主要介绍了近期在铑催化的不对称氢甲酰化反应研究方面取得的进展,重点介绍几类代表性的手性膦配体在此类反应中的应用.%Hydroformylation is one of the most important processes of homogeneous catalysis in industry.Asymmetric hydroformylation (AHF) of prochiral alkenes provides an efficient way to the synthesis of optically active aldehydes,which are versatile chiral intermediates for pharmaceuticals,agrochemicals,and other fine chemicals.So far,most of methods reported were focused on the use of Rh(I)-based catalysts,by virtue of their high catalytic activity and excellent chemoselectivity for the aldehydes.A key issue in searching for efficient asymmetric hydroformylation catalysts is the development of new chiral ligands.A number of chiral phosphorus ligands have been successfully developed for Rh(I)-catalyzed AHF reactions.In this review,the recent advances in the development of chiral ligands for the Rh-catalyzed asymmetric hydroformylaion of olefins have been surveyed.

  8. Spiro annulation of cage polycycles via Grignard reaction and ring-closing metathesis as key steps

    Directory of Open Access Journals (Sweden)

    Sambasivarao Kotha

    2015-08-01

    Full Text Available A simple synthetic strategy to C2-symmetric bis-spiro-pyrano cage compound 7 involving ring-closing metathesis is reported. The hexacyclic dione 10 was prepared from simple and readily available starting materials such as 1,4-naphthoquinone and cyclopentadiene. The synthesis of an unprecedented octacyclic cage compound through intramolecular Diels–Alder (DA reaction as a key step is described. The structures of three new cage compounds 7, 12 and 18 were confirmed by single crystal X-ray diffraction studies.

  9. N-Heterocyclic Carbene Complexes in Olefin Metathesis

    Science.gov (United States)

    Luan, Xinjun; Dorta, Reto; Leitgeb, Anita; Slugovc, Christian; Tiede, Sascha; Blechert, Siegfried

    Olefin metathesis is now a synthetic tool found ubiquitously in various fields involving synthesis. Of its many variations, three are prominently used: (1) catalytic ring closing metathesis (RCM) is an extremely powerful method for the construction of carbon-carbon double bonds in organic chemistry; (2) ring opening metathesis polymerisation (ROMP) where polymers are formed by use of the energy released from cyclic strain; and (3) cross metathesis (CM) where non-cyclic partners are coupled through C-C double bond formation. These important transformations and variations on these themes mediated by second generation ruthenium complexes bearing a NHC ligand will be presented in the following sections.

  10. Aromatizing olefin metathesis by ligand isolation inside a metal-organic framework.

    Science.gov (United States)

    Vermeulen, Nicolaas A; Karagiaridi, Olga; Sarjeant, Amy A; Stern, Charlotte L; Hupp, Joseph T; Farha, Omar K; Stoddart, J Fraser

    2013-10-01

    The aromatizing ring-closing metathesis has been shown to take place inside an extended porous framework. Employing a combination of solvent-assisted linker exchange and postsynthesis modification using olefin metathesis, the noninterpenetrated SALEM-14 was formed and converted catalytically into PAH-MOF-1 with polycyclic aromatic hydrocarbon (PAH) pillars. The metal-organic framework in SALEM-14 prevents "intermolecular" olefin metathesis from occurring between the pillars in the presence of the first generation Hoveyda-Grubbs catalyst, while favoring the production of a PAH, which can be released from the framework under acidic conditions in dimethylsulfoxide.

  11. Stitched α-helical peptides via bis ring-closing metathesis.

    Science.gov (United States)

    Hilinski, Gerard J; Kim, Young-Woo; Hong, Jooyeon; Kutchukian, Peter S; Crenshaw, Charisse M; Berkovitch, Shaunna S; Chang, Andrew; Ham, Sihyun; Verdine, Gregory L

    2014-09-03

    Conformationally stabilized α-helical peptides are capable of inhibiting disease-relevant intracellular or extracellular protein-protein interactions in vivo. We have previously reported that the employment of ring-closing metathesis to introduce a single all-hydrocarbon staple along one face of an α-helical peptide greatly increases α-helical content, binding affinity to a target protein, cell penetration through active transport, and resistance to proteolytic degradation. In an effort to improve upon this technology for stabilizing a peptide in a bioactive α-helical conformation, we report the discovery of an efficient and selective bis ring-closing metathesis reaction leading to peptides bearing multiple contiguous staples connected by a central spiro ring junction. Circular dichroism spectroscopy, NMR, and computational analyses have been used to investigate the conformation of these "stitched" peptides, which are shown to exhibit remarkable thermal stabilities. Likewise, trypsin proteolysis assays confirm the achievement of a structural rigidity unmatched by peptides bearing a single staple. Furthermore, fluorescence-activated cell sorting (FACS) and confocal microscopy assays demonstrate that stitched peptides display superior cell penetrating ability compared to their stapled counterparts, suggesting that this technology may be useful not only in the context of enhancing the drug-like properties of α-helical peptides but also in producing potent agents for the intracellular delivery of proteins and oligonucleotides.

  12. Chelating ruthenium phenolate complexes: synthesis, general catalytic activity, and applications in olefin metathesis polymerization.

    Science.gov (United States)

    Kozłowska, Anna; Dranka, Maciej; Zachara, Janusz; Pump, Eva; Slugovc, Christian; Skowerski, Krzysztof; Grela, Karol

    2014-10-20

    Cyclic Ru-phenolates were synthesized, and these compounds were used as olefin metathesis catalysts. Investigation of their catalytic activity pointed out that, after activation with chemical agents, these catalysts promote ring-closing metathesis (RCM), enyne and cross-metathesis (CM) reactions, including butenolysis, with good results. Importantly, these latent catalysts are soluble in neat dicyclopentadiene (DCPD) and show good applicability in ring-opening metathesis polymeriyation (ROMP) of this monomer.

  13. Olefin Metathesis Reaction in Water and in Air Improved by Supramolecular Additives.

    Science.gov (United States)

    Tomasek, Jasmine; Seßler, Miriam; Gröger, Harald; Schatz, Jürgen

    2015-10-21

    A range of water-immiscible commercially available Grubbs-type precatalysts can be used in ring-closing olefin metathesis reaction in high yields. The synthetic transformation is possible in pure water under ambient conditions. Sulfocalixarenes can help to boost the reactivity of the metathesis reaction by catalyst activation, improved mass transfer, and solubility of reactants in the aqueous reaction media. Additionally, the use of supramolecular additives allows lower catalyst loadings, but still high activity in pure water under aerobic conditions.

  14. Supported Catalysts Useful in Ring-Closing Metathesis, Cross Metathesis, and Ring-Opening Metathesis Polymerization

    Directory of Open Access Journals (Sweden)

    Jakkrit Suriboot

    2016-04-01

    Full Text Available Ruthenium and molybdenum catalysts are widely used in synthesis of both small molecules and macromolecules. While major developments have led to new increasingly active catalysts that have high functional group compatibility and stereoselectivity, catalyst/product separation, catalyst recycling, and/or catalyst residue/product separation remain an issue in some applications of these catalysts. This review highlights some of the history of efforts to address these problems, first discussing the problem in the context of reactions like ring-closing metathesis and cross metathesis catalysis used in the synthesis of low molecular weight compounds. It then discusses in more detail progress in dealing with these issues in ring opening metathesis polymerization chemistry. Such approaches depend on a biphasic solid/liquid or liquid separation and can use either always biphasic or sometimes biphasic systems and approaches to this problem using insoluble inorganic supports, insoluble crosslinked polymeric organic supports, soluble polymeric supports, ionic liquids and fluorous phases are discussed.

  15. Synthetic strategy for bicyclic tetrapeptides HDAC inhibitors using ring closing metathesis

    Indian Academy of Sciences (India)

    Md Nurul Islam; Md Shahidul Islam; Md Ashraful Hoque; Tamaki Kato; Norikazu Nishino

    2015-09-01

    Cyclic peptides show diverse biological activities and are considered as good therapeutic agents due to structural rigidity, receptor selectivity and biochemical stability. We have developed bicyclic tetrapeptide HDAC inhibitors based on different cyclic tetrapeptide scaffolds. For the synthesis of these bicyclic tetrapeptides, two cyclization steps, namely, peptide cyclization and fusion of aliphatic side chains by ring closing metathesis (RCM) were involved. In the course of these syntheses, we have established two facts: a lower limit of aliphatic loop length and better synthetic route for bicyclic tetrapeptide synthesis. It was found that nine methylene loop length is the lower limit for aliphatic loop and the synthetic route selection depended on the configuration of amino acids in the cyclic tetrapeptide scaffold. RCM followed by peptide cyclization was the proper route for LDLD configuration and the reverse route was suitable for LLLD configuration.

  16. Stereoselective synthesis of the C1-C13 fragment of (+)-discodermolide using asymmetric allyltitanations.

    Science.gov (United States)

    BouzBouz, Samir; Cossy, Janine

    2003-08-21

    [reaction: see text] The synthesis of the C1-C13 fragment of (+)-discodermolide has been achieved. The configurations of the stereogenic centers have been controlled by enantioselective allyl- and crotyltitanations of aldehydes, and the Z configuration of the olefin at C8-C9 was controlled by a ring-closing metathesis.

  17. Olefin metathesis and catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Kukes, S. G.; Banks, R. L.

    1985-05-14

    Olefins are converted into other olefins having different numbers of carbon atoms by contact with a catalyst comprising an inorganic refractory oxide support containing at least one of tungsten oxide and molybdenum oxide and a promoting amount of at least one methylating agent under conditions suitable for the methylating agent compounds to promote the activity of tungsten and molybdenum oxides for the disproportionation reaction.

  18. Z-Selective olefin metathesis on peptides: investigation of side-chain influence, preorganization, and guidelines in substrate selection.

    Science.gov (United States)

    Mangold, Shane L; O'Leary, Daniel J; Grubbs, Robert H

    2014-09-01

    Olefin metathesis has emerged as a promising strategy for modulating the stability and activity of biologically relevant compounds; however, the ability to control olefin geometry in the product remains a challenge. Recent advances in the design of cyclometalated ruthenium catalysts has led to new strategies for achieving such control with high fidelity and Z selectivity, but the scope and limitations of these catalysts on substrates bearing multiple functionalities, including peptides, remained unexplored. Herein, we report an assessment of various factors that contribute to both productive and nonproductive Z-selective metathesis on peptides. The influence of sterics, side-chain identity, and preorganization through peptide secondary structure are explored by homodimerization, cross metathesis, and ring-closing metathesis. Our results indicate that the amino acid side chain and identity of the olefin profoundly influence the activity of cyclometalated ruthenium catalysts in Z-selective metathesis. The criteria set forth for achieving high conversion and Z selectivity are highlighted by cross metathesis and ring-closing metathesis on diverse peptide substrates. The principles outlined in this report are important not only for expanding the scope of Z-selective olefin metathesis to peptides but also for applying stereoselective olefin metathesis in general synthetic endeavors.

  19. Z-Selective Olefin Metathesis on Peptides: Investigation of Side-Chain Influence, Preorganization, and Guidelines in Substrate Selection

    Science.gov (United States)

    2015-01-01

    Olefin metathesis has emerged as a promising strategy for modulating the stability and activity of biologically relevant compounds; however, the ability to control olefin geometry in the product remains a challenge. Recent advances in the design of cyclometalated ruthenium catalysts has led to new strategies for achieving such control with high fidelity and Z selectivity, but the scope and limitations of these catalysts on substrates bearing multiple functionalities, including peptides, remained unexplored. Herein, we report an assessment of various factors that contribute to both productive and nonproductive Z-selective metathesis on peptides. The influence of sterics, side-chain identity, and preorganization through peptide secondary structure are explored by homodimerization, cross metathesis, and ring-closing metathesis. Our results indicate that the amino acid side chain and identity of the olefin profoundly influence the activity of cyclometalated ruthenium catalysts in Z-selective metathesis. The criteria set forth for achieving high conversion and Z selectivity are highlighted by cross metathesis and ring-closing metathesis on diverse peptide substrates. The principles outlined in this report are important not only for expanding the scope of Z-selective olefin metathesis to peptides but also for applying stereoselective olefin metathesis in general synthetic endeavors. PMID:25102124

  20. Synthesis of interlocked molecules by olefin metathesis

    Science.gov (United States)

    Clark, Paul Gregory

    A large body of work in the Grubbs group has focused on the development of functional-group tolerant ruthenium alkylidene catalysts that perform a number of olefin metathesis reactions. These catalysts have seen application in a wide range of fields, including classic total synthesis as well as polymer and materials chemistry. One particular family of compounds, interlocked molecules, has benefitted greatly from these advances in catalyst stability and activity. This thesis describes several elusive and challenging interlocked architectures whose syntheses have been realized through the utilization of different types of ruthenium-catalyzed olefin metathesis reactions. Ring-closing olefin metathesis has enabled the synthesis of a [c2]daisy-chain dimer with the ammonium binding site near the cap of the dimer. A deprotonated DCD possessing such a structural attribute will more forcefully seek to restore coordinating interactions upon reprotonation, enhancing its utility as a synthetic molecular actuator. Dimer functionalization facilitated incorporation into linear polymers, with a 48% size increase of an unbound, extended analogue of the polymer demonstrating slippage of the dimer units. Ongoing work is directed at further materials studies, in particular, exploring the synthesis of macroscopic networks containing the DCD units and analyzing the correlation between molecular-scale extension-contraction manipulations and resulting macro-scale changes. A "clipping" approach to a polycatenated cyclic polymer, a structure that resembles a molecular "charm bracelet", has been described. The use of ring-opening metathesis polymerization of a carbamate monomer in the presence of a chain transfer agent allowed for the synthesis of a linear polymer that was subsequently functionalized and cyclized to the corresponding cyclic analogue. This cyclic polymer was characterized through a variety of techniques, and subjected to further functionalization reactions, affording a cyclic

  1. Synthesis of a novel uridine analogue and its use in attempts to form new cyclonucleosides using ring-closing metathesis

    Institute of Scientific and Technical Information of China (English)

    MONDON; Martine; LEN; Christophe

    2010-01-01

    One novel nucleoside analogue having a hex-5-enyl group and an allyl group in the 5’-C and 3-N position was synthesized regioand diastereoselectively from D-glucose in twelve steps.In order to reach a particular conformation of nucleosides the nucleoside formation of restricted cyclonucleoside analogues was studied via Ring-Closing Metathesis.

  2. Olefin metathesis and catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Kukes, S. G.; Banks, R. L.

    1985-03-12

    Olefins are converted into other olefins having different numbers of carbon atoms by contact with a catalyst comprising an inorganic refractory material containing at least one of tungsten oxide and molybdenum oxide and a promoting amount of at least one treating agent selected from chlorinated silicon compounds, thionyl chloride, and sulfuryl chloride under conditions suitable for the treating agent to promote the activity of tungsten and molybdenum oxides for the disporoportionation reaction.

  3. Ring-closing metathesis for the synthesis of a highly G-quadruplex selective macrocyclic hexaoxazole having enhanced cytotoxic potency.

    Science.gov (United States)

    Satyanarayana, Mavurapu; Rzuczek, Suzanne G; Lavoie, Edmond J; Pilch, Daniel S; Liu, Angela; Liu, Leroy F; Rice, Joseph E

    2008-07-01

    The synthesis of a 24-membered macrocyclic hexaoxazole via ring-closing metathesis is described. The target compound selectively stabilizes G-quadruplex DNA with no detectable stabilization of duplex DNA. An MTT cytotoxicity assay indicated that this unsaturated macrocyclic hexaoxazole exhibits significant cytotoxicity toward P388, RPMI 8402, and KB3-1 cell lines with IC50 values of 45, 25, and 38 nM, respectively.

  4. A bis-calixarene from olefin metathesis

    Directory of Open Access Journals (Sweden)

    Shimelis T. Hailu

    2012-06-01

    Full Text Available A ring-closing olefin metathesis reaction of tetrakis(allyloxycalix[4]arene gave the bis calixarene, (15E,40E,60E-65,74-bis(prop-2-en-1-yloxy-13,18,38,43,58,63-hexaoxadodecacyclo[28.26.8.720,36.111,45.151,55.05,57.07,12.019,24.026,64.032,37.044,49.168,72]tetraheptaconta-1,3,5(57,7,9,11,15,19(24,20,22,26,28,30(64,32,34,36,40,44(49,45,47,51,53,55(65,60,68,70,72(74-heptacosaene, C74H68O8. It is a cage formed from two calix[4]arene units joined by butenyl groups at three of the O atoms on the narrow rim. The fourth O atom on each calixarene unit is joined with an allyl group. Each of the calix[4]arene units has a flattened cone conformation in which the allyloxy-substituted aryl group and the opposite aryl group are close together and almost parallel [dihedral angle between planes = 1.09 (11°], and the other two aryl groups are splayed outward [dihedral angle between planes = 79.53 (11°]. No guest molecule (e.g. solvent was observed within the cage. The alkene C atoms of one of the links between the calixarene moieties are disordered over two orientations with occupancies of 0.533 (9 and 0.467 (9.

  5. Photolithographic olefin metathesis polymerization.

    Science.gov (United States)

    Weitekamp, Raymond A; Atwater, Harry A; Grubbs, Robert H

    2013-11-13

    Patterning functional materials is a central challenge across many fields of science. The ability to lithographically fabricate micro- and nanostructures has been one of the most impactful technological breakthroughs of the last century. In part due to the complexity of the chemical processes in photoresists, there is a limited variety of materials that can currently be patterned by photolithography. We report a negative tone photoresist using a photoactivated olefin metathesis catalyst, which can be quickly prepared in a one-pot synthesis from commercially available starting materials. The resist is based on a ruthenium vinyl ether complex, widely regarded as inactive toward olefin metathesis. The combination of this photoactivated catalyst with the fidelity and functional group tolerance of ruthenium-mediated olefin metathesis enables a host of new possibilities for photopatterned materials.

  6. Recovery of olefin monomers

    Science.gov (United States)

    Golden, Timothy Christoph; Weist, Jr., Edward Landis; Johnson, Charles Henry

    2004-03-16

    In a process for the production of a polyolefin, an olefin monomer is polymerised said polyolefin and residual monomer is recovered. A gas stream comprising the monomer and nitrogen is subjected to a PSA process in which said monomer is adsorbed on a periodically regenerated silica gel or alumina adsorbent to recover a purified gas stream containing said olefin and a nitrogen rich stream containing no less than 99% nitrogen and containing no less than 50% of the nitrogen content of the gas feed to the PSA process.

  7. Living olefin polymerization processes

    Science.gov (United States)

    Schrock, Richard R.; Baumann, Robert

    1999-01-01

    Processes for the living polymerization of olefin monomers with terminal carbon-carbon double bonds are disclosed. The processes employ initiators that include a metal atom and a ligand having two group 15 atoms and a group 16 atom or three group 15 atoms. The ligand is bonded to the metal atom through two anionic or covalent bonds and a dative bond. The initiators are particularly stable under reaction conditions in the absence of olefin monomer. The processes provide polymers having low polydispersities, especially block copolymers having low polydispersities. It is an additional advantage of these processes that, during block copolymer synthesis, a relatively small amount of homopolymer is formed.

  8. Synthesis of Electronically Modified Ru-Based Neutral 16 VE Allenylidene Olefin Metathesis Precatalysts

    Directory of Open Access Journals (Sweden)

    Siegfried Blechert

    2012-05-01

    Full Text Available Electronic modifications within Ru-based olefin metathesis precatalysts have provided a number of new complexes with significant differences in reactivity profiles. So far, this aspect has not been studied for neutral 16 VE allenylidenes. The first synthesis of electronically altered complexes of this type is reported. Following the classical dehydration approach (vide infra modified propargyl alcohols were transformed to the targeted allenylidene systems in the presence of PCy3. The catalytic performance was investigated in RCM reaction (ring closing metathesis of benchmark substrates such as diallyltosylamide (6 and diethyl diallylmalonate (7.

  9. A Thermo- and Photo-Switchable Ruthenium Initiator For Olefin Metathesis.

    Science.gov (United States)

    Sashuk, Volodymyr; Danylyuk, Oksana

    2016-05-01

    A ruthenium carbene complex bearing azobenzene functionality is reported. The complex exists in the form of two isomers differing by the size of the chelate ring. Both isomers were isolated by applying kinetic or thermodynamic control during the synthesis and characterized by X-ray diffraction analysis. The isomerization of the complex was studied by UV/Vis spectroscopy. The stable isomer was tested as a catalyst in olefin metathesis. The complex was activated at about 100 °C to promote ring-closing and ring-opening polymerization metathesis reactions. The activation took place also at room temperature under middle ultraviolet radiation.

  10. Beyond catalyst deactivation: cross-metathesis involving olefins containing N-heteroaromatics

    Science.gov (United States)

    Lafaye, Kevin; Bosset, Cyril; Nicolas, Lionel

    2015-01-01

    Summary Alkenes containing N-heteroaromatics are known to be poor partners in cross-metathesis reactions, probably due to catalyst deactivation caused by the presence of a nitrogen atom. However, some examples of ring-closing and cross-metathesis involving alkenes that incorporate N-heteroaromatics can be found in the literature. In addition, recent mechanistic studies have focused on the rationalization of nitrogen-induced catalysts deactivation. The purpose of this mini-review is to give a brief overview of successful metathesis reactions involving olefins containing N-heteroaromatics in order to delineate some guidelines for the use of these challenging substrates in metathesis reactions. PMID:26664645

  11. Olefin Metathesis in Homogeneous Aqueous Media Catalyzed by Conventional Ruthenium Catalysts

    Science.gov (United States)

    Binder, Joseph B.; Blank, Jacqueline J.; Raines, Ronald T.

    2008-01-01

    Olefin metathesis in aqueous solvents is sought for applications in green chemistry and with the hydrophilic substrates of chemical biology, such as proteins and polysaccharides. Most demonstrations of metathesis in water, however, utilize exotic complexes. We have examined the performance of conventional catalysts in homogeneous water–organic mixtures, finding that the second-generation Hoveyda–Grubbs catalyst has extraordinary efficiency in aqueous dimethoxyethane and aqueous acetone. High (71–95%) conversions are achieved for ring-closing and cross metathesis of a variety of substrates in these solvent systems. PMID:17949009

  12. Biopolymer-supported ionic-liquid-phase ruthenium catalysts for olefin metathesis.

    Science.gov (United States)

    Clousier, Nathalie; Filippi, Alexandra; Borré, Etienne; Guibal, Eric; Crévisy, Christophe; Caijo, Fréderic; Mauduit, Marc; Dez, Isabelle; Gaumont, Annie-Claude

    2014-04-01

    Original ruthenium supported ionic liquid phase (SILP) catalysts based on alginates as supports were developed for olefin metathesis reactions. The marine biopolymer, which fulfills most of the requisite properties for a support such as widespread abundance, insolubility in the majority of organic solvents, a high affinity for ionic liquids, high chemical stability, biodegradability, low cost, and easy processing, was impregnated by [bmim][PF6 ] containing an ionically tagged ruthenium catalyst. These biosourced catalysts show promising performances in ring-closing metathesis (RCM) and cross-metathesis (CM) reactions, with a high level of recyclability and reusability combined with a good reactivity.

  13. Beyond catalyst deactivation: cross-metathesis involving olefins containing N-heteroaromatics.

    Science.gov (United States)

    Lafaye, Kevin; Bosset, Cyril; Nicolas, Lionel; Guérinot, Amandine; Cossy, Janine

    2015-01-01

    Alkenes containing N-heteroaromatics are known to be poor partners in cross-metathesis reactions, probably due to catalyst deactivation caused by the presence of a nitrogen atom. However, some examples of ring-closing and cross-metathesis involving alkenes that incorporate N-heteroaromatics can be found in the literature. In addition, recent mechanistic studies have focused on the rationalization of nitrogen-induced catalysts deactivation. The purpose of this mini-review is to give a brief overview of successful metathesis reactions involving olefins containing N-heteroaromatics in order to delineate some guidelines for the use of these challenging substrates in metathesis reactions.

  14. Olefin Metathesis Reaction in Water and in Air Improved by Supramolecular Additives

    Directory of Open Access Journals (Sweden)

    Jasmine Tomasek

    2015-10-01

    Full Text Available A range of water-immiscible commercially available Grubbs-type precatalysts can be used in ring-closing olefin metathesis reaction in high yields. The synthetic transformation is possible in pure water under ambient conditions. Sulfocalixarenes can help to boost the reactivity of the metathesis reaction by catalyst activation, improved mass transfer, and solubility of reactants in the aqueous reaction media. Additionally, the use of supramolecular additives allows lower catalyst loadings, but still high activity in pure water under aerobic conditions.

  15. Beyond catalyst deactivation: cross-metathesis involving olefins containing N-heteroaromatics

    Directory of Open Access Journals (Sweden)

    Kevin Lafaye

    2015-11-01

    Full Text Available Alkenes containing N-heteroaromatics are known to be poor partners in cross-metathesis reactions, probably due to catalyst deactivation caused by the presence of a nitrogen atom. However, some examples of ring-closing and cross-metathesis involving alkenes that incorporate N-heteroaromatics can be found in the literature. In addition, recent mechanistic studies have focused on the rationalization of nitrogen-induced catalysts deactivation. The purpose of this mini-review is to give a brief overview of successful metathesis reactions involving olefins containing N-heteroaromatics in order to delineate some guidelines for the use of these challenging substrates in metathesis reactions.

  16. Bulky N-Phosphino-Functionalized N-Heterocyclic Carbene Ligands: Synthesis, Ruthenium Coordination Chemistry, and Ruthenium Alkylidene Complexes for Olefin Metathesis.

    Science.gov (United States)

    Brown, Christopher C; Rominger, Frank; Limbach, Michael; Hofmann, Peter

    2015-11-01

    Ruthenium chemistry and applications in catalytic olefin metathesis based on N-phosphino-functionalized N-heterocyclic carbene ligands (NHCPs) are presented. Alkyl NHCP Ru coordination chemistry is described, and access to several potential synthetic precursors for ruthenium alkylidene complexes is outlined, incorporating both trimethylsilyl and phenyl alkylidenes. The Ru alkylidene complexes are evaluated as potential olefin metathesis catalysts and were shown to behave in a latent fashion. They displayed catalytic activity at elevated temperatures for both ring closing metathesis and ring opening metathesis polymerization.

  17. A facile synthetic route to diazepinone derivatives via ring closing metathesis and its application for human cytidine deaminase inhibitors.

    Science.gov (United States)

    Kim, Minkyoung; Gajulapati, Kondaji; Kim, Chorong; Jung, Hwa Young; Goo, Jail; Lee, Kyeong; Kaur, Navneet; Kang, Hyo Jin; Chung, Sang J; Choi, Yongseok

    2012-12-04

    A variety of diazepinone derivatives were prepared from α-amino acids and amino alcohols by a new synthetic methodology based on ring closing metathesis as a key step. The diazepinones were coupled with ribose derivatives to afford novel diazepinone nucleosides. Among them, (4R)-1-ribosyl-4-methyl-3,4-dihydro-1H-1,3-diazepin-2(7H)-one (3) showed a potent inhibitory effect (K(i) = 145.97 ± 4.87 nM) against human cytidine deaminase.

  18. A tandem Mannich addition–palladium catalyzed ring-closing route toward 4-substituted-3(2H-furanones

    Directory of Open Access Journals (Sweden)

    Jubi John

    2014-06-01

    Full Text Available A facile route towards highly functionalized 3(2H-furanones via a sequential Mannich addition–palladium catalyzed ring closing has been elaborated. The reaction of 4-chloroacetoacetate esters with imines derived from aliphatic and aromatic aldehydes under palladium catalysis afforded 4-substituted furanones in good to excellent yields. 4-Hydrazino-3(2H-furanones could also be synthesized from diazo esters in excellent yields by utilising the developed strategy. We could also efficiently transform the substituted furanones to aza-prostaglandin analogues.

  19. Homobimetallic Ruthenium-N-Heterocyclic Carbene Complexes For Olefin Metathesis

    Science.gov (United States)

    Sauvage, Xavier; Demonceau, Albert; Delaude, Lionel

    In this chapter, the synthesis and catalytic activity towards olefin metathesis of homobimetallic ruthenium (Ru)-alkylidene, -cyclodiene or -arene complexes bearing phosphine or N-heterocyclic carbene (NHC) ligands are reviewed. Emphasis is placed on the last category of bimetallic compounds. Three representatives of this new type of molecular scaffold were investigated. Thus, [(p-cymene)Ru(m-Cl)3RuCl (h2-C2H4)(L)] complexes with L = PCy3 (15a), IMes (16a), or IMesCl2 (16b) were prepared. They served as catalyst precursors for cross-metathesis (CM) of various styrene derivatives. These experiments revealed the outstanding aptitude of complex 16a (and to a lesser extent of 16b) to catalyze olefin metathesis reactions. Contrary to monometallic Ru-arene complexes of the [RuCl2(p-cymene)(L)] type, the new homobimetallic species did not require the addition of a diazo compound nor visible light illumination to initiate the ring-opening metathesis of norbornene or cyclooctene. When diethyl 2,2-diallylmalonate and N,N-diallyltosylamide were exposed to 16a,b, a mixture of cycloisomerization and ring-closing metathesis (RCM) products was obtained in a nonselective way. Addition of phenylacetylene enhanced the metathetical activity while completely repressing the cycloisomerization process.

  20. New pseudohalide ligands in Ru-catalyzed olefin metathesis : a robust, air-activated iminopyrrolato catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Drouin, S.D.; Foucault, H.M.; Yap, G.P.A.; Fogg, D.E. [Ottawa Univ., ON (Canada). Dept. of Chemistry, Center for Catalysis Research and Innovation

    2005-07-01

    This study demonstrated the feasibility of using iminopyrrolatos as a new pseudohalide ligand in Ru-catalyzed olefin metathesis, particularly in terms of stereo control and anchoring. Ring-closing metathesis (RCM) and cross-metathesis reactions hold promise for pharmaceutical synthesis, as well as green chemistry initiatives to transform seed oils into olefin feedstocks. The advent of robust, functional-group tolerant ruthenium (Ru) catalysts has expanded the deployment of olefin metathesis methodologies by the organic community. Despite recent advances in metathesis activity, major issues remain to be addressed, particularly the problem of short catalyst lifetimes which increase catalyst loading requirements, as well as heavy metal contamination of the organic products. This study revealed that chelation does not prevent isomerization of aryloxide ligands that form larger, seven-membered chelate rings. Complex 5 proved to be a robust olefin metathesis catalyst, effecting RCM of the benchmark substrate diethyl diallylmalonate at 70 degrees C in air, in nondistilled and nondegassed solvent. The reaction revealed complete selectivity for RCM over intermolecular acyclic diene metathesis processes, even in the absence of a solvent. It was shown that RuCl(NN')(Pcy{sub 3})(CHPh) (5) is activated via loss of phosphine. As a result, the catalyst achieves maximum activity in the presence of air, providing a good experimental protocol for metathesis chemistry.

  1. Olefin metathesis in air.

    Science.gov (United States)

    Piola, Lorenzo; Nahra, Fady; Nolan, Steven P

    2015-01-01

    Since the discovery and now widespread use of olefin metathesis, the evolution of metathesis catalysts towards air stability has become an area of significant interest. In this fascinating area of study, beginning with early systems making use of high oxidation state early transition metal centers that required strict exclusion of water and air, advances have been made to render catalysts more stable and yet more functional group tolerant. This review summarizes the major developments concerning catalytic systems directed towards water and air tolerance.

  2. A bis-calixarene from olefin metathesis

    Science.gov (United States)

    Hailu, Shimelis T.; Butcher, Ray J.; Hudrlik, Paul F.; Hudrlik, Anne M.

    2012-01-01

    A ring-closing olefin metathesis reaction of tetra­kis­(all­yl­oxy)calix[4]arene gave the bis­ calixarene, (15E,40E,60E)-65,74-bis­(prop-2-en-1-yl­oxy)-13,18,38,43,58,63-hexa­oxado­deca­cyclo­[28.26.8.720,36.111,45.151,55.05,57.07,12.019,24.026,64.032,37.044,49.168,72]tetra­hepta­conta-1,3,5(57),7,9,11,15,19(24),20,22,26,28,30(64),32,34,36,40,44(49),45,47,51,53,55(65),60,68,70,72(74)-hepta­cosa­ene, C74H68O8. It is a cage formed from two calix[4]arene units joined by butenyl groups at three of the O atoms on the narrow rim. The fourth O atom on each calixarene unit is joined with an allyl group. Each of the calix[4]arene units has a flattened cone conformation in which the all­yloxy-substituted aryl group and the opposite aryl group are close together and almost parallel [dihedral angle between planes = 1.09 (11)°], and the other two aryl groups are splayed outward [dihedral angle between planes = 79.53 (11)°]. No guest mol­ecule (e.g. solvent) was observed within the cage. The alkene C atoms of one of the links between the calixarene moieties are disordered over two orientations with occupancies of 0.533 (9) and 0.467 (9). PMID:22719604

  3. A bis-calixarene from olefin metathesis.

    Science.gov (United States)

    Hailu, Shimelis T; Butcher, Ray J; Hudrlik, Paul F; Hudrlik, Anne M

    2012-06-01

    A ring-closing olefin metathesis reaction of tetra-kis-(all-yl-oxy)calix[4]arene gave the bis- calixarene, (15E,40E,60E)-65,74-bis-(prop-2-en-1-yl-oxy)-13,18,38,43,58,63-hexa-oxado-deca-cyclo-[28.26.8.7(20,36).1(11,45).1(51,55).0(5,57).0(7,12).0(19,24).0(26,64).0(32,37).0(44,49).1(68,72)]tetra-hepta-conta-1,3,5(57),7,9,11,15,19(24),20,22,26,28,30(64),32,34,36,40,44(49),45,47,51,53,55(65),60,68,70,72(74)-hepta-cosa-ene, C(74)H(68)O(8). It is a cage formed from two calix[4]arene units joined by butenyl groups at three of the O atoms on the narrow rim. The fourth O atom on each calixarene unit is joined with an allyl group. Each of the calix[4]arene units has a flattened cone conformation in which the all-yloxy-substituted aryl group and the opposite aryl group are close together and almost parallel [dihedral angle between planes = 1.09 (11)°], and the other two aryl groups are splayed outward [dihedral angle between planes = 79.53 (11)°]. No guest mol-ecule (e.g. solvent) was observed within the cage. The alkene C atoms of one of the links between the calixarene moieties are disordered over two orientations with occupancies of 0.533 (9) and 0.467 (9).

  4. A new convenient asymmetric approach to herbarumin Ⅲ

    Institute of Scientific and Technical Information of China (English)

    Xue Song Chen; Shi Jun Da; Li Hong Yang; Bo Yan Xu; Zhi Xiang Xie; Ying Li

    2007-01-01

    The asymmetric total synthesis of herbarumin Ⅲ 3, a naturally occurred phytotoxin, along with 8-epi-herbarumin Ⅲ 22, was succeeded in 12 steps from n-butyraldehyde based on Brown's asymmetric allylation, taking modified Julia olefination and Yamaguchi's macro-lactonization as key steps.

  5. Design,Synthesis of Chiral Ketone and Application in Asymmetric Epoxidation

    Institute of Scientific and Technical Information of China (English)

    She Xue-gong; Tian Hong-qi; Shi Yi-an

    2004-01-01

    A class of chiral ketone was synthesized for asymmetric epoxidation. High ee values have been obtained for a number of cis olefin and trans olefin. The epoxidation was stereospecific with no isomerizatiom observed in the epoxidation of acyclic system. Encourageingly high ee value has also been obtained for a number of terminal olefins. Mechanistic studies show that electronic interactions play an important role in the stereodifferentiation.

  6. Ruthenium-catalyzed metathesis reactions of ortho- and meta-dialkenyl-carboranes: efficient ring-closing and acyclic diene polymerization reactions.

    Science.gov (United States)

    Guron, Marta; Wei, Xiaolan; Carroll, Patrick J; Sneddon, Larry G

    2010-07-05

    The ruthenium-catalyzed metathesis reactions of dialkenyl-substituted ortho- and meta-carboranes provide excellent routes to both cyclic-substituted o-carboranes and new types of main-chain m-carborane polymers. The adjacent positions of the two olefins in the 1,2-(alkenyl)(2)-o-carboranes strongly favor the formation of ring-closed (RCM) products with the reactions of 1,2-(CH(2)=CHCH(2))(2)-1,2-C(2)B(10)H(10) (1), 1,2-(CH(2)=CH(CH(2))(3)CH(2))(2)-1,2-C(2)B(10)H(10) (2), 1,2-(CH(2)=CHSiMe(2))(2)-1,2-C(2)B(10)H(10) (3), 1,2-(CH(2)=CHCH(2)SiMe(2))(2)-1,2-C(2)B(10)H(10) (4), and 1,2-[CH(2)=CH(CH(2))(4)SiMe(2)](2)-1,2-C(2)B(10)H(10) (5) affording 1,2-(-CH(2)CH=CHCH(2)-)-C(2)B(10)H(10) (10), 1,2-[-CH(2)(CH(2))(3)CH=CH(CH(2))(3)CH(2)-]-1,2-C(2)B(10)H(10) (11), 1,2-[-SiMe(2)CH=CHSiMe(2)-]-1,2-C(2)B(10)H(10) (12), 1,2-[-SiMe(2)CH(2)CH=CHCH(2)SMe(2)-]-C(2)B(10)H(10) (13), and 1,2-[-SiMe(2)(CH(2))(4)CH=CH(CH(2))(4)SiMe(2)-]-C(2)B(10)H(10) (14), respectively, in 72-97% yields. On the other hand, the reaction of 1,2-(CH(2)-CHCH(2)OC(=O))(2)-1,2-C(2)B(10)H(10) (6) gave cyclo-[1,2-(1',8'-C(=O)OCH(2)CH=CHCH(2)OC(=O))-1,2-C(2)B(10)H(10)](2) (15a) and polymer 15b resulting from intermolecular metathesis reactions. The nonadjacent positions of the alkenyl groups in the 1,7-(alkenyl)(2)-m-carboranes, 1,7-(CH(2)=CHCH(2))(2)-1,7-C(2)B(10)H(10) (7), 1,7-(CH(2)=CH(CH(2))(3)CH(2))(2)-1,7-C(2)B(10)H(10) (8), and 1,7-(CH(2)=CHCH(2)SiMe(2))(2)-1,7-C(2)B(10)H(10) (9), disfavor the formation of RCM products, and in these cases, acyclic diene metathesis polymerizations (ADMET) produced new types of main chain m-carborane polymers. The structures of 3, 9, 11, 12, 13, and 15a were crystallographically confirmed.

  7. Industrial processes of olefin metathesis. Pt. 1

    Energy Technology Data Exchange (ETDEWEB)

    Warwel, S.

    1987-05-01

    Olefin metathesis opens new synthetic routes to typical petrochemicals (ethylene, propylene, n-butenes), special olefins (neohexene, higher molecular linear olefins, , -dienes) and unsaturated polymers (polynorbornene, -cyclooctene, -dicyclopentadiene) in an industrial scale. The 8 metathesis processes used in industry and further possible applications of olefin metathesis are reviewed.

  8. Olefin metathesis in air

    Directory of Open Access Journals (Sweden)

    Lorenzo Piola

    2015-10-01

    Full Text Available Since the discovery and now widespread use of olefin metathesis, the evolution of metathesis catalysts towards air stability has become an area of significant interest. In this fascinating area of study, beginning with early systems making use of high oxidation state early transition metal centers that required strict exclusion of water and air, advances have been made to render catalysts more stable and yet more functional group tolerant. This review summarizes the major developments concerning catalytic systems directed towards water and air tolerance.

  9. Olefin metathesis catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Kukes, S.G.; Banks, R.L.

    1986-05-20

    A process is described for preparing a disproportionation catalyst comprising admixing a catalytically effective amount of a calcined and activated catalyst consisting essentially of at least one metal oxide selected from molybdenum oxide and tungsten oxide and a support containing a major proportion of silica or alumina with a promoting amount of a methylating agent selected from the group consisting of dimethyl sulfate, dimethylsulfoxide, trimethyloxonium tetrafluorborate, methyl iodide, and methyl bromide, and subjecting same to inert atmospheric conditions for the methylating agent to promote the activity of the calcined molybdenum and tungsten oxides for the disproportionation of olefins.

  10. Olefin metathesis in air

    Science.gov (United States)

    Piola, Lorenzo; Nahra, Fady

    2015-01-01

    Summary Since the discovery and now widespread use of olefin metathesis, the evolution of metathesis catalysts towards air stability has become an area of significant interest. In this fascinating area of study, beginning with early systems making use of high oxidation state early transition metal centers that required strict exclusion of water and air, advances have been made to render catalysts more stable and yet more functional group tolerant. This review summarizes the major developments concerning catalytic systems directed towards water and air tolerance. PMID:26664625

  11. Study on the Asymmetric Aminohydroxylation of Olefins Catalyzed by a Free Recoverable and Reusable Ligand%可回收手性配体催化烯烃不对称氨羟化反应研究

    Institute of Scientific and Technical Information of China (English)

    南鹏娟; 陈晶; 孙晓莉

    2011-01-01

    A reusable free cinchona alkaloid derivative ligand was applied to asymmetric aminohydroxylation (AA) of 5 five methyl cinnamates with 91%-96% e.e. and 52%-72% yields. In the AA reaction of methyl cinnamates,this ligand can be easily recovered and reused without any significant loss in its catalytic efficiency by two defferent methods. this ligand was applied to the catalytic asymmetric aminohydroxylation to produce enantioselective α-aminoacid esters.%一种可重复使用的非支载型金鸡纳生物碱衍生物配体与金属锇形成原位催化剂用于催化5种肉桂酸甲酯类烯烃的不对称氨羟化(AA)反应,表现了好的对映选择性(91%~96%)和反应活性(52%~72%).在以对甲基肉桂酸甲酯为底物的AA反应中,采用了两种不同的回收方法,均能有效地进行配体的回收和再利用,配体的催化活性和对映选择性基本保持不变.该手性配体用于催化AA反应,可以制备光学活性的α-氨基酸酯类化合物.

  12. Tandem catalysis of ring-closing metathesis/atom transfer radical reactions with homobimetallic ruthenium–arene complexes

    Directory of Open Access Journals (Sweden)

    Yannick Borguet

    2010-12-01

    Full Text Available The tandem catalysis of ring-closing metathesis/atom transfer radical reactions was investigated with the homobimetallic ruthenium–indenylidene complex [(p-cymeneRu(μ-Cl3RuCl(3-phenyl-1-indenylidene(PCy3] (1 to generate active species in situ. The two catalytic processes were first carried out independently in a case study before the whole sequence was optimized and applied to the synthesis of several polyhalogenated bicyclic γ-lactams and lactones from α,ω-diene substrates bearing trihaloacetamide or trichloroacetate functionalities. The individual steps were carefully monitored by 1H and 31P NMR spectroscopies in order to understand the intimate details of the catalytic cycles. Polyhalogenated substrates and the ethylene released upon metathesis induced the clean transformation of catalyst precursor 1 into the Ru(II–Ru(III mixed-valence compound [(p-cymeneRu(μ-Cl3RuCl2(PCy3], which was found to be an efficient promoter for atom transfer radical reactions under the adopted experimental conditions.

  13. Recycling asymmetric hydrogenation catalysts by their immobilisation onto ion-exchange resins.

    Science.gov (United States)

    Barbaro, Pierluigi; Bianchini, Claudio; Giambastiani, Giuliano; Oberhauser, Werner; Bonzi, Laura Morassi; Rossi, Filippo; Dal Santo, Vladimiro

    2004-06-21

    New systems based on cationic chiral phosphine-rhodium complexes anchored to a commercial cation-exchange gel-type resin showed high efficiency and easy recycling in the asymmetric hydrogenation of prochiral olefins.

  14. Elaboration of Sterically Hindered δ-Lactones through Ring-Closing Metathesis: Application to the Synthesis of the C1-C27 Fragment of Hemicalide.

    Science.gov (United States)

    Lecourt, Camille; Boinapally, Srikanth; Dhambri, Sabrina; Boissonnat, Guillaume; Meyer, Christophe; Cossy, Janine; Sautel, François; Massiot, Georges; Ardisson, Janick; Sorin, Geoffroy; Lannou, Marie-Isabelle

    2016-12-16

    The synthesis of the C1-C27 fragment of hemicalide, a marine metabolite displaying a unique potent antiproliferative activity, has been accomplished. The synthetic approach highlights a remarkably efficient ring-closing metathesis reaction catalyzed by Nolan ruthenium indenylidene complexes to elaborate the highly substituted δ-lactone framework.

  15. A new type of self-supported, polymeric Ru-carbene complex for homogeneous catalysis and heterogeneous recovery: synthesis and catalytic activities for ring-closing metathesis.

    Science.gov (United States)

    Chen, Shu-Wei; Kim, Ju Hyun; Shin, Hyunik; Lee, Sang-Gi

    2008-08-01

    A novel 2nd generation Grubbs-type catalyst tethering an isopropoxystyrene has been synthesized and automatically polymerized in solution to form a self-supported polymeric Ru-carbene complex, which catalyzed ring-closing metathesis homogeneously, but was recovered heterogeneously.

  16. Silver(I)-catalyzed dual activation of propargylic alcohol and aziridine/azetidine: triggering ring-opening and endo-selective ring-closing in a cascade.

    Science.gov (United States)

    Bera, Milan; Roy, Sujit

    2009-11-20

    [Ag(COD)(2)]PF(6) catalyzes the reaction between propargyl alcohols and N-tosylaziridines/azetidines leading to a diverse range of N,O-heterocycles, namely, oxazines, oxazepines, and oxazocines via ring-opening and ring-closing in a cascade.

  17. Mechanistic studies of olefin metathesis

    Energy Technology Data Exchange (ETDEWEB)

    Grubbs, R.H.

    1979-03-01

    A review covers studies of the olefin metathesis mechanism which indicated that the reaction proceeds by a non-pairwise mechanism; detailed mechanistic studies on the homogeneously and heterogeneously catalyzed metathesis; and stereochemical investigations.

  18. Stereospecific olefin polymerization catalysts

    Science.gov (United States)

    Bercaw, John E.; Herzog, Timothy A.

    1998-01-01

    A metallocene catalyst system for the polymerization of .alpha.-olefins to yield stereospecific polymers including syndiotactic, and isotactic polymers. The catalyst system includes a metal and a ligand of the formula ##STR1## wherein: R.sup.1, R.sup.2, and R.sup.3 are independently selected from the group consisting of hydrogen, C.sub.1 to C.sub.10 alkyl, 5 to 7 membered cycloalkyl, which in turn may have from 1 to 3 C.sub.1 to C.sub.10 alkyls as a substituent, C.sub.6 to C.sub.15 aryl or arylalkyl in which two adjacent radicals may together stand for cyclic groups having 4 to 15 carbon atoms which in turn may be substituted, or Si(R.sup.8).sub.3 where R.sup.8 is selected from the group consisting of C.sub.1 to C.sub.10 alkyl, C.sub.6 to C.sub.15 aryl or C.sub.3 to C.sub.10 cycloalkyl; R.sup.4 and R.sup.6 are substituents both having van der Waals radii larger than the van der Waals radii of groups R.sup.1 and R.sup.3 ; R.sup.5 is a substituent having a van der Waals radius less than about the van der Waals radius of a methyl group; E.sup.1, E.sup.2 are independently selected from the group consisting of Si(R.sup.9).sub.2, Si(R.sup.9).sub.2 --Si(R.sup.9).sub.2, Ge(R.sup.9).sub.2, Sn(R.sup.9).sub.2, C(R.sup.9).sub.2, C(R.sup.9).sub.2 --C(R.sup.9).sub.2, where R.sup.9 is C.sub.1 to C.sub.10 alkyl, C.sub.6 to C.sub.15 aryl or C.sub.3 to C.sub.10 cycloalkyl; and the ligand may have C.sub.S or C.sub.1 -symmetry. Preferred metals are selected from the group consisting of group III, group IV, group V or lanthanide group elements. The catalysts are used to prepare stereoregular polymers including polypropylene from .alpha.-olefin monomers.

  19. Hydride Olefin complexes of tantalum and niobium

    NARCIS (Netherlands)

    Klazinga, Aan Hendrik

    1979-01-01

    This thesis describes investigations on low-valent tantalum and niobium hydride and alkyl complexes, particularly the dicyclopentadienyl tantalum hydride olefin complexes Cp2Ta(H)L (L=olefin). ... Zie: Summary

  20. Build/Couple/Pair Strategy Combining the Petasis 3-Component Reaction with Ru-Catalyzed Ring-Closing Metathesis and Isomerization

    DEFF Research Database (Denmark)

    Ascic, Erhad; Le Quement, Sebastian Thordal; Ishøy, Mette;

    2012-01-01

    A “build/couple/pair” pathway for the systematic synthesis of structurally diverse small molecules is presented. The Petasis 3-component reaction was used to synthesize anti-amino alcohols displaying pairwise reactive combinations of alkene moieties. Upon treatment with a ruthenium alkylidene-cat......-catalyst, these dienes selectively underwent ring-closing metathesis reactions to form 5- and 7-membered heterocycles and cyclic aminals via a tandem isomerization/N-alkyliminium cyclization sequence....

  1. A straightforward synthetic entry to cleavamine-type indole alkaloids by a ring-closing metathesis-vinyl halide Heck cyclization strategy.

    Science.gov (United States)

    Bennasar, M-Lluïsa; Solé, Daniel; Zulaica, Ester; Alonso, Sandra

    2011-04-15

    An indole-templated ring-closing metathesis has been used to create the central nine-membered ring of the cleavamine-type alkaloids. A subsequent intramolecular vinyl halide Heck reaction upon the resulting azacyclononene ring completes the assembly of the strained 1-azabicyclo[6.3.1]dodecane framework of the alkaloids. The usefulness of the approach is illustrated with the synthesis of (±)-cleavamine and (±)-dihydrocleavamine.

  2. Ru complexes of Hoveyda–Grubbs type immobilized on lamellar zeolites: activity in olefin metathesis reactions

    Directory of Open Access Journals (Sweden)

    Hynek Balcar

    2015-11-01

    Full Text Available Hoveyda–Grubbs type catalysts with cationic tags on NHC ligands were linker-free immobilized on the surface of lamellar zeolitic supports (MCM-22, MCM-56, MCM-36 and on mesoporous molecular sieves SBA-15. The activity of prepared hybrid catalysts was tested in olefin metathesis reactions: the activity in ring-closing metathesis of citronellene and N,N-diallyltrifluoroacetamide decreased in the order of support MCM-22 ≈ MCM-56 > SBA-15 > MCM-36; the hybrid catalyst based on SBA-15 was found the most active in self-metathesis of methyl oleate. All catalysts were reusable and exhibited low Ru leaching (− counter anion; in contrast, PF6− counter anion underwent partial decomposition.

  3. Ru complexes of Hoveyda-Grubbs type immobilized on lamellar zeolites: activity in olefin metathesis reactions.

    Science.gov (United States)

    Balcar, Hynek; Žilková, Naděžda; Kubů, Martin; Mazur, Michal; Bastl, Zdeněk; Čejka, Jiří

    2015-01-01

    Hoveyda-Grubbs type catalysts with cationic tags on NHC ligands were linker-free immobilized on the surface of lamellar zeolitic supports (MCM-22, MCM-56, MCM-36) and on mesoporous molecular sieves SBA-15. The activity of prepared hybrid catalysts was tested in olefin metathesis reactions: the activity in ring-closing metathesis of citronellene and N,N-diallyltrifluoroacetamide decreased in the order of support MCM-22 ≈ MCM-56 > SBA-15 > MCM-36; the hybrid catalyst based on SBA-15 was found the most active in self-metathesis of methyl oleate. All catalysts were reusable and exhibited low Ru leaching (<1% of Ru content). XPS analysis revealed that during immobilization ion exchange between Hoveyda-Grubbs type catalyst and zeolitic support occurred in the case of Cl(-) counter anion; in contrast, PF6 (-) counter anion underwent partial decomposition.

  4. Ru complexes of Hoveyda–Grubbs type immobilized on lamellar zeolites: activity in olefin metathesis reactions

    Science.gov (United States)

    Žilková, Naděžda; Kubů, Martin; Mazur, Michal; Bastl, Zdeněk; Čejka, Jiří

    2015-01-01

    Summary Hoveyda–Grubbs type catalysts with cationic tags on NHC ligands were linker-free immobilized on the surface of lamellar zeolitic supports (MCM-22, MCM-56, MCM-36) and on mesoporous molecular sieves SBA-15. The activity of prepared hybrid catalysts was tested in olefin metathesis reactions: the activity in ring-closing metathesis of citronellene and N,N-diallyltrifluoroacetamide decreased in the order of support MCM-22 ≈ MCM-56 > SBA-15 > MCM-36; the hybrid catalyst based on SBA-15 was found the most active in self-metathesis of methyl oleate. All catalysts were reusable and exhibited low Ru leaching (<1% of Ru content). XPS analysis revealed that during immobilization ion exchange between Hoveyda–Grubbs type catalyst and zeolitic support occurred in the case of Cl− counter anion; in contrast, PF6 − counter anion underwent partial decomposition. PMID:26664629

  5. The Effects of NHC-Backbone Substitution on Efficiency in Ruthenium-based Olefin Metathesis

    Science.gov (United States)

    Kuhn, Kevin M.; Bourg, Jean-Baptiste; Chung, Cheol K.; Virgil, Scott C.; Grubbs, Robert H.

    2009-01-01

    A series of ruthenium olefin metathesis catalysts bearing N-heterocyclic carbene (NHC) ligands with varying degrees of backbone and N-aryl substitution have been prepared. These complexes show greater resistance to decomposition through C–H activation of the N-aryl group, resulting in increased catalyst lifetimes. This work has utilized robotic technology to examine the activity and stability of each catalyst in metathesis, providing insights into the relationship between ligand architecture and enhanced efficiency. The development of this robotic methodology has also shown that, under optimized conditions, catalyst loadings as low as 25 ppm can lead to 100% conversion in the ring-closing metathesis of diethyl diallylmalonate. PMID:19351207

  6. Linker-free, silica-bound olefin-metathesis catalysts: applications in heterogeneous catalysis.

    Science.gov (United States)

    Cabrera, José; Padilla, Robin; Bru, Miriam; Lindner, Ronald; Kageyama, Takeharu; Wilckens, Kristina; Balof, Shawna L; Schanz, Hans-Jörg; Dehn, Richard; Teles, J Henrique; Deuerlein, Stephan; Müller, Kevin; Rominger, Frank; Limbach, Michael

    2012-11-12

    A set of heterogenized olefin-metathesis catalysts, which consisted of Ru complexes with the H(2)ITap ligand (1,3-bis(2',6'-dimethyl-4'dimethyl aminophenyl)-4,5-dihydroimidazol-2-ylidene) that had been adsorbed onto a silica support, has been prepared. These complexes showed strong binding to the solid support without the need for tethering groups on the complex or functionalized silica. The catalysts were tested in the ring-opening-ring-closing-metathesis (RO-RCM) of cyclooctene (COE) and the self-metathesis of methyl oleate under continuous-flow conditions. The best complexes showed a TON>4000, which surpasses the previously reported materials that were either based on the Grubbs-Hoveyda II complex on silica or on the classical heterogeneous Re(2)O(7)/B(2)O(3) catalyst.

  7. Synthesis of 7-Deoxypancratistatin from Carbohydrates by the Use of Olefin Metathesis

    DEFF Research Database (Denmark)

    Håkansson, Anders Eckart; Palmelund, Anders; Holm, H.;

    2006-01-01

    -deoxy-5-iodo-D-ribofuranoside in the presence of zinc metal. The first strategy involves a total of only 13 steps from D-ribose and piperonal, but suffers from a low yield in the zinc-mediated reaction between ribofuranoside 9, benzylamine, and bromide 7. The second strategy involves a total of 18 steps......The stereocontrolled synthesis of (+)-7-deoxypancratistatin is described. The convergent synthesis has been achieved by two different strategies, both of which commence from a pentose and piperonal. The latter is converted into allylic bromide 7, which is then coupled with a protected methyl 5...... from D-xylose and piperonal. The former is converted into ribofuranoside 28, which is coupled with bromide 7 in the presence of zinc, and this is followed by ring-closing olefin metathesis. Subsequent Overman rearrangement, dihydroxylation, and deprotection then affords the natural product....

  8. Enantioselective Cyclopropanation of a Wide Variety of Olefins Catalyzed by Ru(II)-Pheox Complexes.

    Science.gov (United States)

    Chanthamath, Soda; Iwasa, Seiji

    2016-10-18

    The transition-metal-catalyzed asymmetric cyclopropanation of olefins with diazoacetates has become one of the most important methods for the synthesis of optically active cyclopropane derivatives, which are key pharmaceutical building blocks and present in a large number of natural products. To date, significant progress has been made in this area of research, and efficient stereocontrolled synthetic approaches to cyclopropane derivatives have been developed using rhodium, ruthenium, copper, and cobalt catalysts. However, the vast majority of these strategies are limited to electron-rich olefins, such as styrene derivatives, due to the electrophilicity of the metal-carbene intermediates generated from the reaction of the metal with the diazo compound. Recently, the D2-symmetric Co(II)-phophyrin complexes developed by Zhang et al. were shown to be the most efficient catalysts for the asymmetric cyclopropanation of electron-deficient olefins. This catalytic system is mechanistically distinct from the previous rhodium and copper catalytic systems, proceeding via radical intermediates. However, the asymmetric cyclopropanation of vinyl carbamates, allenes, and α,β-unsaturated carbonyl compounds has rarely been reported. Therefore, the development of new powerful catalysts for the asymmetric cyclopropanation of a wide range of olefinic substrates is the next challenge in this field. In this Account, we summarize our recent studies on the Ru(II)-Pheox-catalyzed asymmetric cyclopropanation of various olefins, including vinyl carbamates, allenes, and α,β-unsaturated carbonyl compounds. We demonstrate that the developed catalytic system effectively promotes the asymmetric cyclopropanation of a wide variety of olefins to produce the desired cyclopropane products in high yields with excellent stereocontrol. The use of succinimidyl-, ketone-, and ester-functionalized diazoacetates as carbene sources was found to be crucial for the high stereoselectivity of the

  9. Synthesis of Highly Stable 1,3-Diaryl-1H-1,2,3-triazol-5-ylidenes and their Applications in Ruthenium-Catalyzed Olefin Metathesis

    Science.gov (United States)

    Bouffard, Jean; Keitz, Benjamin K.; Tonner, Ralf; Lavallo, Vincent; Guisado-Barrios, Gregorio; Frenking, Gernot

    2011-01-01

    The formal cycloaddition between 1,3-diaza-2-azoniaallene salts and alkynes or alkyne equivalents provides an efficient synthesis of 1,3-diaryl-1H-1,2,3-triazolium salts, the direct precursors of 1,2,3-triazol-5-ylidenes. These N,N-diarylated mesoionic carbenes (MICs) exhibit enhanced stability in comparison to their alkylated counterparts. Experimental and computational results confirm that these MICs act as strongly electron-donating ligands. Their increased stability allows for the preparation of ruthenium olefin metathesis catalysts that are efficient in both ring-opening and ring-closing reactions. PMID:21572542

  10. Application of olefin metathesis in petrochemistry

    Energy Technology Data Exchange (ETDEWEB)

    Warwel, S.

    1979-01-01

    A survey covers the catalysts used in olefin metathesis; olefin types which undergo metathesis, e.g., ring-opening metathetic polymerization of cycloolefins; equilibria and side reactions; the Phillips Triolefin process for 2-butene production; the Shell Higher Olefin Process (SHOP) for the production of C/sub 11/-C/sub 14/ ..cap alpha..-olefins; the Phillips Petroleum 225 ton/yr process for the conversion of trimethylpentane to neohexene, which is used in gasoline and pharmaceutical manufacture; the production of isoprene precursors; and various other metathesis reactions used in synthesizing specific olefins.

  11. Quinone diazides for olefin functionalization.

    Science.gov (United States)

    Dao, Hai T; Baran, Phil S

    2014-12-22

    The utility of quinone diazides in materials science is vast and well-documented, yet this potentially useful motif has languished in the annals of organic synthesis. Herein we show that modern tools of catalysis can be employed with free or suitably masked quinone diazides to unleash the power of these classic diazo compounds in the context of both inter- and intramolecular olefin cyclopropanation.

  12. Homogeneous asymmetric catalysis in fragrance chemistry.

    Science.gov (United States)

    Ciappa, Alessandra; Bovo, Sara; Bertoldini, Matteo; Scrivanti, Alberto; Matteoli, Ugo

    2008-06-01

    Opposite enantiomers of a chiral fragrance may exhibit different olfactory activities making a synthesis in high enantiomeric purity commercially and scientifically interesting. Accordingly, the asymmetric synthesis of four chiral odorants, Fixolide, Phenoxanol, Citralis, and Citralis Nitrile, has been investigated with the aim to develop practically feasible processes. In the devised synthetic schemes, the key step that leads to the formation of the stereogenic center is the homogeneous asymmetric hydrogenation of a prochiral olefin. By an appropriate choice of the catalyst and the reaction conditions, Phenoxanol, Citralis, and Citralis Nitrile were obtained in high enantiomeric purity, and odor profiles of the single enantiomers were determined.

  13. Ring-Closing and Cross-Metathesis with Artificial Metalloenzymes Created by Covalent Active Site-Directed Hybridization of a Lipase

    NARCIS (Netherlands)

    Basauri-Molina, Manuel; Verhoeven, Dide G A; Van Schaik, Arnoldus J.; Kleijn, H; Klein Gebbink, Robertus J M

    2015-01-01

    A series of Grubbs-type catalysts that contain lipase-inhibiting phosphoester functionalities have been synthesized and reacted with the lipase cutinase, which leads to artificial metalloenzymes for olefin metathesis. The resulting hybrids comprise the organometallic fragment that is covalently boun

  14. Microwave-Assisted Olefin Metathesis

    Science.gov (United States)

    Nicks, François; Borguet, Yannick; Sauvage, Xavier; Bicchielli, Dario; Delfosse, Sébastien; Delaude, Lionel; Demonceau, Albert

    Since the first reports on the use of microwave irradiation to accelerate organic chemical transformations, a plethora of papers have been published in this field. In most examples, microwave heating has been shown to dramatically reduce reaction times, increase product yields, and enhance product purity by reducing unwanted side reactions compared to conventional heating methods. The present contribution aims at illustrating the advantages of this technology in olefin metathesis and, when data are available, at comparing microwave-heated and conventionally heated experiments

  15. Design and Stereoselective Preparation of a New Class of Chiral Olefin Metathesis Catalysts and Application to Enantioselective Synthesis of Quebrachamine: Catalyst Development Inspired by Natural Product Synthesis

    Science.gov (United States)

    Sattely, Elizabeth S.; Meek, Simon J.; Malcolmson, Steven J.; Schrock, Richard R.; Hoveyda, Amir H.

    2010-01-01

    A total synthesis of the Aspidosperma alkaloid quebrachamine in racemic form is first described. A key catalytic ring-closing metathesis of an achiral triene is used to establish the all-carbon quaternary stereogenic center and the tetracyclic structure of the natural product; the catalytic transformation proceeds with reasonable efficiency through the use of existing achiral Ru or Mo catalysts. Ru- or Mo-based chiral olefin metathesis catalysts have proven to be inefficient and entirely nonselective in cases where the desired product is observed. In the present study, the synthesis route thus serves as a platform for the discovery of new olefin metathesis catalysts that allow for efficient completion of an enantioselective synthesis of quebrachamine. Accordingly, on the basis of mechanistic principles, stereogenic-at-Mo complexes bearing only monodentate ligands have been designed. The new catalysts provide significantly higher levels of activity than observed with the previously reported Ru- or Mo-based complexes. Enantiomerically enriched chiral alkylidenes are generated through diastereoselective reactions involving achiral Mo-based bispyrrolides and enantiomerically pure silyl-protected binaphthols. Such chiral catalysts initiate the key enantioselective ring-closing metathesis step in the total synthesis of quebrachamine efficiently (1 mol % loading, 22 °C, 1 h, >98% conversion, 84% yield) and with high selectivity (98:2 er, 96% ee). PMID:19113867

  16. Synthesis of Dialkyl-substituted Terminal Olefin

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Dialkyl-substituted terminal olefins were synthesized from the coupling reaction of αt-olefins which were catalyzed by zirconocene dichloride/methylalumoxane (MAO) catalyst system under mild condition. High yield was gained and no other oligmer was detected. It was found that the ratio of Al/Zr is responsible for the selectivity of product.

  17. Catalyst-controlled stereoselective olefin metathesis as a principal strategy in multistep synthesis design: a concise route to (+)-neopeltolide.

    Science.gov (United States)

    Yu, Miao; Schrock, Richard R; Hoveyda, Amir H

    2015-01-01

    Molybdenum-, tungsten-, and ruthenium-based complexes that control the stereochemical outcome of olefin metathesis reactions have been recently introduced. However, the complementary nature of these systems through their combined use in multistep complex molecule synthesis has not been illustrated. A concise diastereo- and enantioselective route that furnishes the anti-proliferative natural product neopeltolide is now disclosed. Catalytic transformations are employed to address every stereochemical issue. Among the featured processes are an enantioselective ring-opening/cross-metathesis promoted by a Mo monoaryloxide pyrrolide (MAP) complex and a macrocyclic ring-closing metathesis that affords a trisubstituted alkene and is catalyzed by a Mo bis(aryloxide) species. Furthermore, Z-selective cross-metathesis reactions, facilitated by Mo and Ru complexes, have been employed in the stereoselective synthesis of the acyclic dienyl moiety of the target molecule.

  18. New Enantiomerically Pure Alkylimido Mo-Based Complexes. Synthesis, Characterization, and Activity as Chiral Olefin Metathesis Catalysts

    Science.gov (United States)

    Pilyugina, Tatiana S.; Schrock, Richard R.; Müller, Peter; Hoveyda, Amir H.

    2008-01-01

    Molybdenum olefin metathesis catalysts that contain aliphatic 1-phenylcyclohexylimido (NPhCy) and 2-phenyl-2-adamantylimido (NPhAd) groups and (S)-Biphen or (R)-Trip)(THF) ligands (Biphen = 3,3′-di-tert-butyl-5,5′,6,6′-tetramethyl-1,1′-biphenyl-2,2′-diolate; Trip = 3,3′-bis(2,4,6-triisopropylphenyl)-2,2′-binaphtholate) have been prepared. Their catalytic activity and enantioselectivity in desymmetrization reactions such as ring-closing metathesis of amines and lactams and ring-opening/cross-metathesis of substituted norborneols with styrene were compared to the results obtained with the only known alkylimido catalyst Mo(NAd)(CHCMe2Ph)[(S)-Biphen]. The activities and enantioselectivities provided by these new chiral complexes vary significantly, but in virtually all instances explored were not superior to the adamantylimido analogs. PMID:19079732

  19. Team for Research on Methanol-to-Olefins Technology

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    Olefins, traditionally derived from oil, are important basic materials for the modern chemical industry. To make olefins from coal rather than oil has been a dream and also a big challenge for scientists all over the world. The step from methanol to olefins is vital in the transformation from coal or natural gas to olefins,

  20. Metátese de olefinas aplicada ao fechamento de anéis: uma ferramenta poderosa para a síntese de macrociclos naturais Ring-closing olefin metathesis: a powerful tool for the synthesis of natural macrocycles

    Directory of Open Access Journals (Sweden)

    Anderson Rouge dos Santos

    2008-01-01

    Full Text Available For a quarter of a century, metathesis has become indispensable for the synthesis of natural and non-natural products, particularly of biologically active compounds. This review illustrates through a maximum of appropriate examples the power and the versatility of the metathesis ring-closure (RCM reaction as a key ring-closure methodology for the synthesis of natural macrocycles. Its high functional group compatibility as well as the possibility of further transformations makes this reaction a powerful tool in the cases where the structural framework and function requirements are difficult to meet.

  1. Asymmetric synthesis of a functionalized tricyclo[6.2.0.02,6]decane ring system present in kelsoene and poduran

    Indian Academy of Sciences (India)

    Amrita Ghosh; Subrata Ghosh

    2014-11-01

    Synthesis of a functionalized tricyclo[6.2.0.02,6]decane derivative in enantiomerically pure form, the core structure present in the natural products kelsoene and poduran, is described. The key steps involve a stereocontrolled copper (I)-catalyzed intramolecular [2+2] photocycloaddition of a 1, 6-diene prepared from D-mannitol to form a substituted bicyclo[3.2.0]heptane derivative and a ring closing olefin metathesis involving the vicinal substituents on the five-membered ring of the bicyclo[3.2.0]heptane derivative.

  2. Bidirectional cross metathesis and ring-closing metathesis/ring opening of a C2-symmetric building block: a strategy for the synthesis of decanolide natural products

    Directory of Open Access Journals (Sweden)

    Bernd Schmidt

    2013-11-01

    Full Text Available Starting from the conveniently available ex-chiral pool building block (R,R-hexa-1,5-diene-3,4-diol, the ten-membered ring lactones stagonolide E and curvulide A were synthesized using a bidirectional olefin-metathesis functionalization of the terminal double bonds. Key steps are (i a site-selective cross metathesis, (ii a highly diastereoselective extended tethered RCM to furnish a (Z,E-configured dienyl carboxylic acid and (iii a Ru–lipase-catalyzed dynamic kinetic resolution to establish the desired configuration at C9. Ring closure was accomplished by macrolactonization. Curvulide A was synthesized from stagonolide E through Sharpless epoxidation.

  3. Bidirectional cross metathesis and ring-closing metathesis/ring opening of a C 2-symmetric building block: a strategy for the synthesis of decanolide natural products.

    Science.gov (United States)

    Schmidt, Bernd; Kunz, Oliver

    2013-01-01

    Starting from the conveniently available ex-chiral pool building block (R,R)-hexa-1,5-diene-3,4-diol, the ten-membered ring lactones stagonolide E and curvulide A were synthesized using a bidirectional olefin-metathesis functionalization of the terminal double bonds. Key steps are (i) a site-selective cross metathesis, (ii) a highly diastereoselective extended tethered RCM to furnish a (Z,E)-configured dienyl carboxylic acid and (iii) a Ru-lipase-catalyzed dynamic kinetic resolution to establish the desired configuration at C9. Ring closure was accomplished by macrolactonization. Curvulide A was synthesized from stagonolide E through Sharpless epoxidation.

  4. The allylic chalcogen effect in olefin metathesis

    Directory of Open Access Journals (Sweden)

    Yuya A. Lin

    2010-12-01

    Full Text Available Olefin metathesis has emerged as a powerful tool in organic synthesis. The activating effect of an allylic hydroxy group in metathesis has been known for more than 10 years, and many organic chemists have taken advantage of this positive influence for efficient synthesis of natural products. Recently, the discovery of the rate enhancement by allyl sulfides in aqueous cross-metathesis has allowed the first examples of such a reaction on proteins. This led to a new benchmark in substrate complexity for cross-metathesis and expanded the potential of olefin metathesis for other applications in chemical biology. The enhanced reactivity of allyl sulfide, along with earlier reports of a similar effect by allylic hydroxy groups, suggests that allyl chalcogens generally play an important role in modulating the rate of olefin metathesis. In this review, we discuss the effect of allylic chalcogens in olefin metathesis and highlight its most recent applications in synthetic chemistry and protein modifications.

  5. Tandem Catalysis Utilizing Olefin Metathesis Reactions.

    Science.gov (United States)

    Zieliński, Grzegorz K; Grela, Karol

    2016-07-01

    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.

  6. The allylic chalcogen effect in olefin metathesis

    Science.gov (United States)

    Lin, Yuya A

    2010-01-01

    Summary Olefin metathesis has emerged as a powerful tool in organic synthesis. The activating effect of an allylic hydroxy group in metathesis has been known for more than 10 years, and many organic chemists have taken advantage of this positive influence for efficient synthesis of natural products. Recently, the discovery of the rate enhancement by allyl sulfides in aqueous cross-metathesis has allowed the first examples of such a reaction on proteins. This led to a new benchmark in substrate complexity for cross-metathesis and expanded the potential of olefin metathesis for other applications in chemical biology. The enhanced reactivity of allyl sulfide, along with earlier reports of a similar effect by allylic hydroxy groups, suggests that allyl chalcogens generally play an important role in modulating the rate of olefin metathesis. In this review, we discuss the effect of allylic chalcogens in olefin metathesis and highlight its most recent applications in synthetic chemistry and protein modifications. PMID:21283554

  7. (Z)-Selective Takai olefination of salicylaldehydes

    Science.gov (United States)

    Galloway, Warren R J D; Sore, Hannah F; Goodman, Jonathan M

    2017-01-01

    The Takai olefination (or Takai reaction) is a method for the conversion of aldehydes to vinyl iodides, and has seen widespread implementation in organic synthesis. The reaction is usually noted for its high (E)-selectivity; however, herein we report the highly (Z)-selective Takai olefination of salicylaldehyde derivatives. Systematic screening of related substrates led to the identification of key factors responsible for this surprising inversion of selectivity, and enabled the development of a modified mechanistic model to rationalise these observations.

  8. Light olefins - challenges from new production routes?

    Energy Technology Data Exchange (ETDEWEB)

    Zimmermann, H. [Linde Engineering, Pullach (Germany)

    2007-07-01

    Light Olefins are the building blocks for many modern plastic products and are produced in large quantities. Driven by high crude oil prices, production is shifted to regions with low cost raw materials. Alternatives to the traditional production from Naphta, AGO and other crude products are becoming attractive. This paper evaluates several methods Ethylene and Pro-pylene production economically and also the regional advantageous routes. The analysis includes Steamcracking, dehydrogenation, dehydration of Ethanol, Methanol based routes and olefin conversion by Metathesis. (orig.)

  9. Hybrid macrocycle formation and spiro annulation on cis-syn-cis-tricyclo[6.3.0.02,6]undeca-3,11-dione and its congeners via ring-closing metathesis

    Directory of Open Access Journals (Sweden)

    Sambasivarao Kotha

    2015-07-01

    Full Text Available We have developed a simple methodology to transform cis-syn-cis-triquinane derivative 2 into the diindole based macrocycle 6 involving Fischer indolization and ring-closing metathesis (RCM. Various spiro-polyquinane derivatives have been assembled via RCM as a key step.

  10. Synthesis of gamma- and delta-lactones from 1alpha-hydroxy-5,6-trans-vitamin D3 by ring-closing metathesis route and their reduction with metal hydrides.

    Science.gov (United States)

    Wojtkielewicz, Agnieszka; Morzycki, Jacek W

    2007-06-01

    New synthetic pathway towards 19-functionalized derivatives of 1alpha-hydroxy-5,6-trans-vitamin D3 was described. Ring-closing metathesis (RCM) of 1alpha-hydroxy-5,6-trans-vitamin D3 1-omega-alkenoates was a key-step. Hydride reduction of resulting lactones led to the new vitamin D3 analogues.

  11. Asymmetric hydrogenation with highly active IndolPhos-Rh catalysts: kinetics and reaction mechanism

    NARCIS (Netherlands)

    Wassenaar, J.; Kuil, M.; Lutz, M.; Spek, A.L.; Reek, J.N.H.

    2010-01-01

    The mechanism of the Indol- Phos–Rh-catalyzed asymmetric hydrogenation of prochiral olefins has been investigated by means of X-ray crystal structure determination, kinetic measurements, high-pressure NMR spectroscopy, and DFT calculations. The mechanistic study indicates that the reaction follows a

  12. Asymmetric hydrogenation with highly active IndolPhos-Rh catalysts: kinetics and reaction mechanism

    NARCIS (Netherlands)

    Wassenaar, J.; Kuil, M.; Lutz, M.; Spek, A.L.; Reek, J.N.H.

    2010-01-01

    The mechanism of the IndolPhos-Rh-catalyzed asymmetric hydrogenation of prochiral olefins has been investigated by means of X-ray crystal structure determination, kinetic measurements, high-pressure NMR spectroscopy, and DFT calculations. The mechanistic study indicates that the reaction follows an

  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 ruth

  14. Olefin metathesis : tapping into breakthrough chemical technology

    Energy Technology Data Exchange (ETDEWEB)

    Granson, E.

    2010-06-15

    Olefin metathesis is a catalyst technology where 2 double bond-containing molecules or olefins are split in order to exchange atoms and result in the formation of 2 new molecules or substances. Earlier researchers used a variety of materials to convert propylene into a mixture of butenes and ethylenes. A method developed by Shell researchers produces linear olefins used as detergent feedstocks. In 1971, scientists used a metal-carbene catalyst to react with the olefins to produce both a new olefin and a new metal carbene in order to perpetuate the process. In 2002, a new metathesis technology was developed using renewable natural oils as a feedstock. The catalyst is introduced as a solid into the oil, and then agitated by stirring. The modified oil is then reacted with hydrogen to remove the double bonds and filter off the catalyst. The method is offered on a contract basis by Elevance Renewable Sciences in a variety of application. The process was designed to take place at lower temperatures with the release of fewer greenhouse gases (GHGs). New metathesis technologies are also being developed to reduce the molecular weight of polymers in order to reduce viscosity and increase flow. 3 figs.

  15. Catalyst-Controlled Stereoselective Olefin Metathesis as a Principal Strategy in Multi-Step Synthesis Design. A Concise Route to (+)-Neopeltolide**

    Science.gov (United States)

    Yu, Miao; Schrock, Richard R.

    2014-01-01

    Mo-, W- and Ru-based complexes that control the stereochemical outcome of olefin metathesis reactions have been recently introduced. However, the complementary nature of these systems through their combined use in multistep complex molecule synthesis has not been illustrated. Here, we disclose a concise diastereo- and enantioselective route that furnishes the anti-proliferative natural product neopeltolide. Catalytic transformations are employed to address every stereochemical issue. Among the featured processes are an enantioselective ring-opening/cross-metathesis promoted by a Mo monopyrrolide aryloxide (MAP) complex and a macrocyclic ring-closing metathesis affording a trisubstituted alkene catalyzed by a Mo bis-aryloxide species. Furthermore, Z-selective cross-metathesis reactions, facilitated by Mo and Ru complexes, have been employed in stereoselective synthesis of the acyclic dienyl moiety of the target molecule. PMID:25377347

  16. Tandem Olefin Metathesis/Oxidative Cyclization: Synthesis of Tetrahydrofuran Diols from Simple Olefins.

    Science.gov (United States)

    Dornan, Peter K; Lee, Daniel; Grubbs, Robert H

    2016-05-25

    A tandem olefin metathesis/oxidative cyclization has been developed to synthesize 2,5-disubstituted tetrahydrofuran (THF) diols in a stereocontrolled fashion from simple olefin precursors. The ruthenium metathesis catalyst is converted into an oxidation catalyst in the second step and is thus responsible for both catalytic steps. The stereochemistry of the 1,5-diene intermediate can be controlled through the choice of catalyst and the type of metathesis conducted. This olefin stereochemistry then controls the THF diol stereochemistry through a highly stereospecific oxidative cyclization.

  17. Diphenylamido Precursors to Bisalkoxide Molybdenum Olefin Metathesis Catalysts

    Science.gov (United States)

    Sinha, Amritanshu; Müller, Peter; Hoveyda, Amir H.

    2008-01-01

    We have found that Mo(NAr)(CHR′)(NPh2)2 (R′ = t-Bu or CMe2Ph) and Mo(NAr′)(CHCMe2Ph)(NPh2)2 (Ar = 2,6-i-Pr2C6H3; Ar′ = 2,6-Me2C6H3) can be prepared through addition of two equivalents of LiNPh2 to Mo(NR″)(CHR′)(OTf)2(dme) species (R″ = Ar or Ar′ dme = 1,2-dimethoxyethane), although yields are low. A high yield route consists of addition of LiNPh2 to bishexafluro-t-butoxide species. An X-ray structure of Mo(NAr)(CHCMe2Ph)(NPh2)2 reveals that the two diphenylamido groups are oriented in a manner that allows an 18 electron count to be achieved. The diphenylamido complexes react readily with t-BuOH and (CF3)2MeCOH, but not readily with the sterically demanding biphenol H2[Biphen] (Biphen2- = 3,3′-Di-t-butyl-5,5′,6,6′-tetramethyl-1,1′-Biphenyl-2,2′-diolate). The diphenylamido complexes do react with various 3,3′-disubstituted binaphthols to yield binaphtholate catalysts that can be prepared in situ and employed for a simple asymmetric ring-closing metathesis reaction. In several cases conversions and enantioselectivities were comparable to reactions in which isolated catalysts were employed. PMID:19030118

  18. Metathesis process for preparing an alpha, omega-functionalized olefin

    Energy Technology Data Exchange (ETDEWEB)

    Burdett, Kenneth A. (Midland, MI); Mokhtarzadeh, Morteza (Charleston, WV); Timmers, Francis J. (Midland, MI)

    2010-10-12

    A cross-metathesis process for preparing an .alpha.,.omega.-functionalized olefin, such as methyl 9-decenoate, and an .alpha.-olefin having three or more carbon atoms, such as 1-decene. The process involves contacting in a first reaction zone an .alpha.-functionalized internal olefin, such as methyl oleate, and an .alpha.-olefinic monomer having three or more carbon atoms, such as 1-decene, with a first metathesis catalyst to prepare an effluent stream containing the .alpha.,.omega.-functionalized olefin, such as methyl 9-decenoate, an unfunctionalized internal olefin, such as 9-octadecene, unconverted reactant olefins, and optionally, an .alpha.,.omega.-difunctionalized internal olefinic dimer, such as dimethyl 9-octadecen-1,18-dioate; separating said effluent streams; then contacting in a second reaction zone the unfunctionalized internal olefin with ethylene in the presence of a second metathesis catalyst to obtain a second product effluent containing the .alpha.-olefinic monomer having three or more carbon atoms; and cycling a portion of the .alpha.-olefinic monomer stream(s) to the first zone.

  19. Rhodium olefin complexes of diiminate type ligands

    NARCIS (Netherlands)

    Willems, Sander Theodorus Hermanus

    2003-01-01

    The mono-anionic beta-diiminate ligand (ArNC(CH3)CHC(CH3)NAr) on several previous occasions proved useful in stabilising low coordination numbers for both early and late transition metals. In this thesis the reactivity of the rhodium olefin complexes of one of these beta-diiminate ligands (Ar = 2,6-

  20. Olefin Recovery from Chemical Industry Waste Streams

    Energy Technology Data Exchange (ETDEWEB)

    A.R. Da Costa; R. Daniels; A. Jariwala; Z. He; A. Morisato; I. Pinnau; J.G. Wijmans

    2003-11-21

    The objective of this project was to develop a membrane process to separate olefins from paraffins in waste gas streams as an alternative to flaring or distillation. Flaring these streams wastes their chemical feedstock value; distillation is energy and capital cost intensive, particularly for small waste streams.

  1. Synthesis of pterostilbene by Julie Olefination

    Science.gov (United States)

    A simple, stereoselective route for the synthesis of the biologically active compounds trans-pterostilbene and tetramethoxy stilbene from the readily available starting materials 3,5-dimethoxy benzyl alcohol and 4-hydroxy benzaldehyde was developed using Julia olefination as a key reaction....

  2. High Trans Kinetic Selectivity in Ruthenium-Based Olefin Cross-Metathesis through Stereoretention.

    Science.gov (United States)

    Johns, Adam M; Ahmed, Tonia S; Jackson, Bradford W; Grubbs, Robert H; Pederson, Richard L

    2016-02-19

    The first kinetically controlled, highly trans-selective (>98%) olefin cross-metathesis reaction is demonstrated using Ru-based catalysts. Reactions with either trans or cis olefins afford products with highly trans or cis stereochemistry, respectively. This E-selective olefin cross-metathesis is shown to occur between two trans olefins and between a trans olefin and a terminal olefin. Additionally, new stereoretentive catalysts have been synthesized for improved reactivity.

  3. Alkene Chemoselectivity in Ruthenium-Catalyzed Z-Selective Olefin Metathesis

    Science.gov (United States)

    Cannon, Jeffrey S.

    2013-01-01

    Chelated ruthenium catalysts have achieved highly chemoselective olefin metathesis reactions. Terminal and internal Z olefins were selectively reacted in the presence of internal E olefins. Products were produced in good yield and high stereoselectivity for formation of a new Z olefin. No products of metathesis with the internal E olefin were observed. Chemoselectivity for terminal olefins was also observed over both sterically hindered and electronically deactivated alkenes. PMID:23832646

  4. Olefin hydroformylation catalysis with RuCl2(DMSO4.

    Directory of Open Access Journals (Sweden)

    Marisela Reyes*

    2008-05-01

    Full Text Available The RuCl2(DMSO4 complex was used as catalytic precursor in olefin hydroformylation reactions, giving good percent yield and better selectivity for linear aldehydes. The reactions were tested in homogeneous medium and biphasic organic solvent/ water systems. The substrates tried were 1-hexene, cyclohexene, 2-methyl-2-pentene, 2,3-dimethyl-2-butene; binary mixtures and synthetic naphtha and real naphtha. The activity is better for linear olefins compared with substituted olefins.

  5. Integrated process and dual-function catalyst for olefin epoxidation

    Science.gov (United States)

    Zhou, Bing; Rueter, Michael

    2003-01-01

    The invention discloses a dual-functional catalyst composition and an integrated process for production of olefin epoxides including propylene oxide by catalytic reaction of hydrogen peroxide from hydrogen and oxygen with olefin feeds such as propylene. The epoxides and hydrogen peroxide are preferably produced simultaneously in situ. The dual-functional catalyst comprises noble metal crystallites with dimensions on the nanometer scale (on the order of olefin oxides such as propylene oxide without formation of undesired co-products.

  6. A chameleon catalyst for nonheme iron-promoted olefin oxidation.

    Science.gov (United States)

    Iyer, Shyam R; Javadi, Maedeh Moshref; Feng, Yan; Hyun, Min Young; Oloo, Williamson N; Kim, Cheal; Que, Lawrence

    2014-11-18

    We report the chameleonic reactivity of two nonheme iron catalysts for olefin oxidation with H2O2 that switch from nearly exclusive cis-dihydroxylation of electron-poor olefins to the exclusive epoxidation of electron-rich olefins upon addition of acetic acid. This switching suggests a common precursor to the nucleophilic oxidant proposed to Fe(III)-η(2)-OOH and electrophilic oxidant proposed to Fe(V)(O)(OAc), and reversible coordination of acetic acid as a switching pathway.

  7. Organic chemistry. Practical olefin hydroamination with nitroarenes.

    Science.gov (United States)

    Gui, Jinghan; Pan, Chung-Mao; Jin, Ying; Qin, Tian; Lo, Julian C; Lee, Bryan J; Spergel, Steven H; Mertzman, Michael E; Pitts, William J; La Cruz, Thomas E; Schmidt, Michael A; Darvatkar, Nitin; Natarajan, Swaminathan R; Baran, Phil S

    2015-05-22

    The synthesis and functionalization of amines are fundamentally important in a vast range of chemical contexts. We present an amine synthesis that repurposes two simple feedstock building blocks: olefins and nitro(hetero)arenes. Using readily available reactants in an operationally simple procedure, the protocol smoothly yields secondary amines in a formal olefin hydroamination. Because of the presumed radical nature of the process, hindered amines can easily be accessed in a highly chemoselective transformation. A screen of more than 100 substrate combinations showcases tolerance of numerous unprotected functional groups such as alcohols, amines, and even boronic acids. This process is orthogonal to other aryl amine syntheses, such as the Buchwald-Hartwig, Ullmann, and classical amine-carbonyl reductive aminations, as it tolerates aryl halides and carbonyl compounds.

  8. Synthetic Studies on Bioactive Natural Polyketides: Intramolecular Nitrile Oxide-Olefin Cycloaddition Approach for Construction of a Macrolactone Skeleton of Macrosphelide B

    Directory of Open Access Journals (Sweden)

    Seung-Mann Paek

    2011-06-01

    Full Text Available Studies on the synthesis of macrosphelide B via an intramolecular nitrile oxide-olefin cycloaddition (INOC is described. In particular, an asymmetric INOC approach using phase transfer catalysts seems to be a potentially efficient and versatile procedure for the construction of the macrolactone skeleton of macrosphelide B in terms of facial selectivity. Our preliminary and unprecedented stereoselective procedure is anticipated to be usefully applied through further studies for the synthesis of the macrosphelide family.

  9. Homogeneous catalysts for stereoregular olefin polymerization

    Science.gov (United States)

    Marks, Tobin J.; Eisen, Moris S.; Giardello, Michael A.

    1994-01-01

    The synthesis, and use as precatalysts of chiral organozirconium complexes for olefin polymerization are disclosed, having the structure (C.sub.5 R'.sub.4-x R*.sub.x) A (C.sub.5 R".sub.4-y R'".sub.y) M Q.sub.p, where x and y represent the number of unsubstituted locations on the cyclopentadienyl ring; R', R", R'", and R* represent substituted and unsubstituted alkyl groups having 1-30 carbon atoms and R* is a chiral ligand; A is a fragment containing a Group 13, 14, 15, or 16 element of the Periodic Table; M is a Group 3, 4, or 5 metal of the Periodic Table; and Q is a hydrocarbyl radical, or halogen radical, with 3.ltoreq.p.ltoreq.o. Related complexes may be prepared by alkylation of the corresponding dichorides. In the presence of methylalumoxane or triarylborane cocatalysts, these complexes form "cation-like" species which are highly active for olefin polymerization. In combination with a Lewis acid cocatalyst, propylene or other .alpha.-olefin polymerization can be effected with very high efficiency and isospecificity.

  10. Alternative routes to olefins. Chances and challenges

    Energy Technology Data Exchange (ETDEWEB)

    Meiswinkel, A.; Delhomme, C.; Ponceau, M. [Linde AG, Pullach (Germany)

    2013-11-01

    In the future, conventional raw materials which are used for the production of olefins will get shorter and more expensive and alternative raw materials and production routes will gain importance. Natural gas, coal, shale oil or bio-mass are potential sources for the production of olefins, especially ethylene and propylene, as major base chemicals. Several potential production routes were already developed in the past, but cost, energy and environmental considerations might make these unattractive or unfeasible in comparison to traditional processes (e.g. steam cracking). Other processes such as methanol to olefins processes were successfully developed and first commercial units are running. In addition, combination of traditional processes (e.g. coal/biomass gasification, Fischer-Tropsch and steam cracking) might enable new pathways. Besides, dehydration of ethanol is opening direct routes from biomass to 'green' ethylene. However, for these 'bio-routes', feedstock availability and potential land use conflict with food production (sugar cane, wheat,..) still need to be evaluated. finally, new oxidative routes, including processes such as oxidative coupling of methane or oxidative dehydrogenation, are still at an early development stage but present potential for future industrial applications. (orig.) (Published in summary form only)

  11. Supported organometallic catalysts for hydrogenation and Olefin Polymerization

    Science.gov (United States)

    Marks, Tobin J.; Ahn, Hongsang

    2001-01-01

    Novel heterogeneous catalysts for the which hydrogenation of olefins and arenes with high conversion rates under ambient conditions and the polymerization of olefins have been developed. The catalysts are synthesized from Ziegler-type precatalysts by supporting them on sulfate-modified zirconia.

  12. Cobalt carbonyl catalyzed olefin hydroformylation in supercritical carbon dioxide

    Science.gov (United States)

    Rathke, Jerome W.; Klingler, Robert J.

    1993-01-01

    A method of olefin hydroformylation is provided wherein an olefin reacts with a carbonyl catalyst and with reaction gases such as hydrogen and carbon monoxide in the presence of a supercritical reaction solvent, such as carbon dioxide. The invention provides higher yields of n-isomer product without the gas-liquid mixing rate limitation seen in conventional Oxo processes using liquid media.

  13. Analysis of Factors Affecting Olefin Content in FCC Gasoline

    Institute of Scientific and Technical Information of China (English)

    Wang Tao

    2005-01-01

    In order to meet the urgent need for reducing olefin content in cracked naphtha, the influence of feedstock characteristics on the olefin content was discussed. The different types and performance of catalysts developed by RIPP were introduced. Moreover, some effective operation approaches in commercial units were presented to serve as a reference to the refiners for catalyst selection.

  14. Carbonyl-Olefin Exchange Reaction: Present State and Outlook

    Science.gov (United States)

    Kalinova, Radostina; Jossifov, Christo

    The carbonyl-olefin exchange reaction (COER) is a new reaction between carbonyl group and olefin double bond, which has a formal similarity with the olefin metathesis (OM) - one carbon atom in the latter is replaced with an oxygen atom. Till now the new reaction is performed successfully only when the two functional groups (carbonyl group and olefin double bond) are in one molecule and are conjugated. The α, β-unsaturated carbonyl compounds (substituted propenones) are the compounds with such a structure. They polymerize giving substituted polyacetylenes. The chain propagation step of this polymerization is in fact the COER. The question arises: is it possible the COER to take place when the two functional groups are not in one molecule and are not conjugated, and could this reaction became an alternative of the existing carbonyl olefination reactions?

  15. Ruthenium-based olefin metathesis catalysts bearing pH-responsive ligands: External control of catalyst solubility and activity

    Science.gov (United States)

    Balof, Shawna Lynn

    2011-12-01

    Sixteen novel, Ru-based olefin metathesis catalysts bearing pH responsive ligands were synthesized. The pH-responsive groups employed with these catalysts included dimethylamino (NMe2) modified NHC ligands as well as N-donor dimethylaminopyridine (DMAP) and 3-(o-pyridyl)propylidene ligands. These pH-responsive ligands provided the means by which the solubility and/or activity profiles of the catalysts produced could be controlled via acid addition. The main goal of this dissertation was to design catalyst systems capable of performing ring opening metathesis (ROMP) and ring closing metathesis (RCM) reactions in both organic and aqueous media. In an effort to quickly gain access to new catalyst structures, a template synthesis for functionalized NHC ligand precursors was designed, in addition to other strategies, to obtain ligand precursors with ancillary NMe2 groups. Kinetic studies for the catalysts produced from these precursors showed external control of catalyst solubility was afforded via protonation of the NMe2 groups of their NHC ligands. Additionally, this protonation afforded external control of catalyst propagation rates for several catalysts. This is the first known independent external control for the propagation rates of ROMP catalysts. The incorporation of pH-responsive N-donor ligands into catalyst structures also provided the means for the external control of metathesis activity, as the protonation of these ligands resulted in an increased initiation rate based on their fast and irreversible dissociation from the metal center. The enhanced external control makes these catalysts applicable to a wide range of applications, some of which have been explored by us and/or through collaboration. Three of the catalysts designed showed remarkable metathesis activity in aqueous media. These catalysts displayed comparable RCM activity in aqueous media to a class of water-soluble catalysts reported by Grubbs et al., considered to be the most active catalyst for

  16. Olefin metathesis over UV-irradiated silica

    Science.gov (United States)

    Tanaka, Tsunehiro; Matsuo, Shigehiro; Maeda, Takashi; Yoshida, Hisao; Funabiki, Takuzo; Yoshida, Satohiro

    1997-11-01

    Photoirradiated silica evacuated at temperatures higher than 800 K was found to be active for olefin metathesis reactions. The analysis of products shows that the metalacyclobutane intermediate is likely. The instantaneous response of the reaction to the irradiation and the activity change with various UV filter showed that the reaction is induced by UV-excitation of silica. The correlation between the evacuation temperature and the activity showed that the surface free from water molecules plays a role in the reaction and the removal of isolated OH groups strongly relates to the generation of active sites.

  17. Methyltrioxorhenium as catalyst for olefin metathesis

    Energy Technology Data Exchange (ETDEWEB)

    Herrmann, W.A. (Technische Univ. Muenchen, Garching (Germany). Anorganisch-Chemisches Inst.); Wagner, W. (Consortium fuer Elektrochemische Industrie GmbH, Muenchen (Germany)); Flessner, U.N.; Volkhardt, U.; Komber, H. (Institut fuer Technologie der Polymere, Dresden (Germany))

    1991-12-01

    No cocatalysts are needed as additives when methyltrioxorhenium (MTO) supported on acidic carriers is employed to catalyze the metathesis of functionalized olefins. A typical system is MTO/Al{sub 2}O{sub 3}-SiO{sub 2}, which is active, for instance, in the metathesis of allyl halides, allylsilanes, unsaturated carboxylates, and nitriles. MTO in combination with R{sub n}AlCl{sub 3-n} is a homogeneous catalyst in ring-opening polymerizations (R = CH{sub 3}, C{sub 2}H{sub 5}; n = 1,2). (orig.).

  18. Profluorescent substrates for the screening of olefin metathesis catalysts.

    Science.gov (United States)

    Reuter, Raphael; Ward, Thomas R

    2015-01-01

    Herein we report on a 96-well plate assay based on the fluorescence resulting from the ring-closing metathesis of two profluorophoric substrates. To demonstrate the validity of the approach, four commercially available ruthenium-metathesis catalysts were evaluated in six different solvents. The results from the fluorescent assay agree well with HPLC conversions, validating the usefulness of the approach.

  19. Profluorescent substrates for the screening of olefin metathesis catalysts

    Directory of Open Access Journals (Sweden)

    Raphael Reuter

    2015-10-01

    Full Text Available Herein we report on a 96-well plate assay based on the fluorescence resulting from the ring-closing metathesis of two profluorophoric substrates. To demonstrate the validity of the approach, four commercially available ruthenium-metathesis catalysts were evaluated in six different solvents. The results from the fluorescent assay agree well with HPLC conversions, validating the usefulness of the approach.

  20. Profluorescent substrates for the screening of olefin metathesis catalysts

    Science.gov (United States)

    Reuter, Raphael

    2015-01-01

    Summary Herein we report on a 96-well plate assay based on the fluorescence resulting from the ring-closing metathesis of two profluorophoric substrates. To demonstrate the validity of the approach, four commercially available ruthenium-metathesis catalysts were evaluated in six different solvents. The results from the fluorescent assay agree well with HPLC conversions, validating the usefulness of the approach. PMID:26664607

  1. 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

  2. Production and use of light olefins. Preprints of the conference

    Energy Technology Data Exchange (ETDEWEB)

    Ernst, S.; Buzzoni, R.; Leitner, W.; Lercher, J.A.; Lichtscheidl, J.; Nees, F.; Santacesaria, E. (eds.)

    2009-07-01

    Within the conference of the German Society for Petroleum and Coal Science and Technology e.V. (Hamburg, Federal Republic of Germany) in Berlin (Federal Republic of Germany) at 28th to 30th September, 2009, the following lectures were held: (1) Steamcracking - State of the Art (H. Zimmermann); (2) Diversify Feedstock Options to Olefin Production (Q. Ling et al.); (3) Syngas to lower olefins (E. Schwab et al.); (4) STAR process registered for the on-purpose production of propylene (K. Bueker); (5) The catalytic activity of zinc oxide supported on aerosil for C-H activation of light alkanes (S. Arndt et al.); (6) Novel catalytic approaches for the oxidative dehydrogenation of ethane (D. Hartmann); (7) A comparison of the active sites structures of homogeneous and heterogeneous olefin polymerisation catalysts (A. Zecchina); (8) Catalytic strategies in metathesis (C. Coperet); (9) Multi-technology integrated production and consumption of olefins (J. Popp et al.); (10) Olefin oligomerization for the production of fuels and petrochemicals (H. Olivier-Bourbigou et al.); (11) Dieselization of the world - How to increase diesel yield in a refinery (A. Dueker); (12) Isomerization of butenes: LyondellBasell's Isomplus technology development (T. Zak et al.); (13) Valuable products from butadiene, carbon dioxide and further base chemicals (A. Behr); (14) The partial oxidation of propene to propylene oxide using N{sub 2}O as an oxidant (T. Thoemmes); (15) Alternative feedstocks for olefin production: What role will ethanol play? (B.R. Maughon); (16) Production of light olefins from renewable resources - The effect of deoxygenation degree on yields of light olefins (D. Kubicka et al.); (17) Recovery of low olefins from refinery offgases (M. Bender).

  3. Rational design of cyclopropane-based chiral PHOX ligands for intermolecular asymmetric Heck reaction

    Directory of Open Access Journals (Sweden)

    Marina Rubina

    2014-07-01

    Full Text Available A novel class of chiral phosphanyl-oxazoline (PHOX ligands with a conformationally rigid cyclopropyl backbone was synthesized and tested in the intermolecular asymmetric Heck reaction. Mechanistic modelling and crystallographic studies were used to predict the optimal ligand structure and helped to design a very efficient and highly selective catalytic system. Employment of the optimized ligands in the asymmetric arylation of cyclic olefins allowed for achieving high enantioselectivities and significantly suppressing product isomerization. Factors affecting the selectivity and the rate of the isomerization were identified. It was shown that the nature of this isomerization is different from that demonstrated previously using chiral diphosphine ligands.

  4. Selective Oxidation and Ammoxidation of Olefins by Heterogeneous Catalysis.

    Science.gov (United States)

    Grasselli, Robert K.

    1986-01-01

    Shows how the ammoxidation of olefins can be understood in terms of free radicals and surface bound organometallic intermediates. Also illustrates the close intellectual relationships between heterogeneous catalysis and organometallic chemistry. (JN)

  5. Cobalt catalyzed hydroesterification of a wide range of olefins

    Energy Technology Data Exchange (ETDEWEB)

    Van Rensburg, H.; Hanton, M.; Tooze, R.P.; Foster, D.F. [Sasol Technology UK, St Andrews (United Kingdom)

    2011-07-01

    Petrochemical raw materials are an essential raw material for the production of detergents with a substantial portion of synthetic fatty alcohols being produced via hydroformylation of oil or coal derived olefins. Carbonylation processes other than hydroformylation have to date not been commercially employed for the production of fatty esters or alcohols. In this document we highlight the opportunities of converting olefins to esters using cobalt catalyzed alkoxycarbonylation. This process is highly versatile and applicable to a wide range of olefins, linear or branched, alpha or internal in combination with virtually any chain length primary or secondary alcohol allowing the synthesis of a diverse array of compounds such as ester ethoxylated surfactants, methyl branched detergents, lubricants and alkyl propanoates. Furthermore, alkoxycarbonylation of a broad olefin/paraffin hydrocarbon range could be used to produce the corresponding broad cut detergent alcohols. (orig.)

  6. Theoretical investigations of olefin metathesis catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Cundari, T.R.; Gordon, M.S. [North Dakota State Univ., Fargo, ND (United States)

    1992-01-01

    An ab initio analysis of the electronic structure of high-valent, transition-metal alkylidenes as models for olefin metathesis catalysts is presented. The catalyst models studied fall into three categories: {open_quotes}new{close_quotes} metathesis catalyst models-tetrahedral M(OH){sup 2}(XH)(CH{sub 2}) complexes; {open_quotes}old{close_quotes} metathesis catalyst models-tetrahedral MCl{sub 2}(Y)(CH{sub 2}) complexes and alkylidene-substituted Mo metathesis catalysts, Mo(OH){sub 2}(NH)(=C(H)Z). The effect on the bonding caused by modification of either the metal, ligands, or alkylidene substitutents is considered. 21 refs., 2 figs., 5 tabs.

  7. Olefins and chemical regulation in Europe: REACH.

    Science.gov (United States)

    Penman, Mike; Banton, Marcy; Erler, Steffen; Moore, Nigel; Semmler, Klaus

    2015-11-05

    REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals) is the European Union's chemical regulation for the management of risk to human health and the environment (European Chemicals Agency, 2006). This regulation entered into force in June 2007 and required manufacturers and importers to register substances produced in annual quantities of 1000 tonnes or more by December 2010, with further deadlines for lower tonnages in 2013 and 2018. Depending on the type of registration, required information included the substance's identification, the hazards of the substance, the potential exposure arising from the manufacture or import, the identified uses of the substance, and the operational conditions and risk management measures applied or recommended to downstream users. Among the content developed to support this information were Derived No-Effect Levels or Derived Minimal Effect Levels (DNELs/DMELs) for human health hazard assessment, Predicted No Effect Concentrations (PNECs) for environmental hazard assessment, and exposure scenarios for exposure and risk assessment. Once registered, substances may undergo evaluation by the European Chemicals Agency (ECHA) or Member State authorities and be subject to requests for additional information or testing as well as additional risk reduction measures. To manage the REACH registration and related activities for the European olefins and aromatics industry, the Lower Olefins and Aromatics REACH Consortium was formed in 2008 with administrative and technical support provided by Penman Consulting. A total of 135 substances are managed by this group including 26 individual chemical registrations (e.g. benzene, 1,3-butadiene) and 13 categories consisting of 5-26 substances. This presentation will describe the content of selected registrations prepared for 2010 in addition to the significant post-2010 activities. Beyond REACH, content of the registrations may also be relevant to other European activities, for

  8. Analysis of olefinic hydrocarbons in cracked petroleum stocks: a review

    Energy Technology Data Exchange (ETDEWEB)

    Badoni, R.P.; Bhagat, S.D.; Joshi, G.C. (Indian Institute of Petroleum, Dehradun (India))

    1992-05-01

    The present review surveys the existing methods of analysis, both chemical and instrumental techniques applicable for the determination of olefinic unsaturation in petroleum products ranging from gases to high molecular weight complex residues. The scope and limitation of each method in relation to its applicability to specific petroleum products is critically discussed. Standardized methods of olefin analysis covered by ASTM, IP and UOP test procedures have also been compiled. 123 refs., 1 tab.

  9. Carbonyl-Olefin Exchange Reaction and Related Chemistry

    Science.gov (United States)

    Jossifov, Christo; Kalinova, Radostina

    A new carbon—carbon double bond forming reaction (carbonyl olefin exchange reaction) mediated by transition metal catalytic systems has been discovered. The catalytic systems used (transition metal halides or oxohalides alone or in combination with Lewis acids) are active only in the case when the two reacting groups are in one molecules and are conjugated. In addition these systems accelerate other reactions which run simultaneously with the carbonyl olefin metathesis rendering a detailed investigation of the process very complicated.

  10. Methods for suppressing isomerization of olefin metathesis products

    Energy Technology Data Exchange (ETDEWEB)

    Firth, Bruce E.; Kirk, Sharon E.

    2015-10-27

    A method for suppressing isomerization of an olefin metathesis product produced in a metathesis reaction includes adding an isomerization suppression agent that includes nitric acid to a mixture that includes the olefin metathesis product and residual metathesis catalyst from the metathesis reaction under conditions that are sufficient to passivate at least a portion of the residual metathesis catalyst. Methods of refining a natural oil are described.

  11. Methods for suppressing isomerization of olefin metathesis products

    Energy Technology Data Exchange (ETDEWEB)

    Firth, Bruce E.; Kirk, Sharon E.; Gavaskar, Vasudeo S.

    2015-09-22

    A method for suppressing isomerization of an olefin metathesis product produced in a metathesis reaction includes adding an isomerization suppression agent to a mixture that includes the olefin metathesis product and residual metathesis catalyst from the metathesis reaction under conditions that are sufficient to passivate at least a portion of the residual metathesis catalyst. The isomerization suppression agent is phosphorous acid, a phosphorous acid ester, phosphinic acid, a phosphinic acid ester or combinations thereof. Methods of refining natural oils are described.

  12. Consideration of applications of olefin metathesis in synthetic fuel production

    Energy Technology Data Exchange (ETDEWEB)

    Heveling, J.

    1984-07-01

    One of the characteristics of Fischer-Tropsch synthesis and many oligomerization processes, is insufficient selectivity. Efforts have to be made to bring the products obtained in line with the market requirements. The olefin metathesis reaction has the potential to convert less desirable olefins to more useful ones and provides new ways of producing petrochemicals. Based on existing and suggested process technologies, applications of this reaction for the production of synthetic liquid fuels are discussed.

  13. Comparing Ru and Fe-catalyzed olefin metathesis.

    Science.gov (United States)

    Poater, Albert; Chaitanya Vummaleti, Sai Vikrama; Pump, Eva; Cavallo, Luigi

    2014-08-01

    Density functional theory calculations have been used to explore the potential of Fe-based complexes with an N-heterocyclic carbene ligand, as olefin metathesis catalysts. Apart from a less endothermic reaction energy profile, a small reduction in the predicted upper energy barriers (≈ 2 kcal mol(-1)) is calculated in the Fe catalyzed profile with respect to the Ru catalysed profile. Overall, this study indicates that Fe-based catalysts have the potential to be very effective olefin metathesis catalysts.

  14. Chelated Ruthenium Catalysts for Z-Selective Olefin Metathesis

    Science.gov (United States)

    Endo, Koji; Grubbs, Robert H.

    2011-01-01

    We report the development of ruthenium-based metathesis catalysts with chelating N-heterocyclic carbene (NHC) ligands which catalyze highly Z-selective olefin metathesis. A very simple and convenient synthetic procedure of such a catalyst has been developed. An intramolecular C-H bond activation of the NHC ligand, which is promoted by anion ligand substitution, forms the appropriate chelate for stereo- controlled olefin metathesis. PMID:21563826

  15. Zwitterionic Group VIII transition metal initiators supported by olefin ligands

    Science.gov (United States)

    Bazan, Guillermo C.; Chen, Yaofeng

    2011-10-25

    A zwitterionic Group VIII transition metal complex containing the simple and relatively small 3-(arylimino)-but-1-en-2-olato ligand that catalyzes the formation of polypropylene and high molecular weight polyethylene. A novel feature of this catalyst is that the active species is stabilized by a chelated olefin adduct. The present invention also provides methods of polymerizing olefin monomers using zwitterionic catalysts, particularly polypropylene and high molecular weight polyethylene.

  16. Coordinatively unsaturated metal organic frameworks for olefin separations

    OpenAIRE

    Renouf, Catherine Louise

    2013-01-01

    The research presented in this thesis aims to assess the capacity of metal organic frameworks with open metal sites for the separation of olefin mixtures. Chapter 1 provides a background to the field, including industrial separation techniques, metal organic frameworks and their applications and the current state-of-the- art for olefin separation. Chapter 3 describes the experimental techniques used in this research. Ethylene and propylene adsorption and desorption isotherms...

  17. Fast olefin metathesis at low catalyst loading.

    Science.gov (United States)

    Peeck, Lars H; Savka, Roman D; Plenio, Herbert

    2012-10-01

    Reactions of the Grubbs 3rd generation complexes [RuCl(2)(NHC)(Ind)(Py)] (N-heterocyclic carbene (NHC)=1,3-bis(2,4,6-trimethylphenylimidazolin)-2-ylidene (SIMes), 1,3-bis(2,6-diisopropylphenylimidazolin)-2-ylidene (SIPr), or 1,3-bis(2,6-diisopropylphenylimidazol)-2-ylidene (IPr); Ind=3-phenylindenylid-1-ene, Py=pyridine) with 2-ethenyl-N-alkylaniline (alkyl=Me, Et) result in the formation of the new N-Grubbs-Hoveyda-type complexes 5 (NHC=SIMes, alkyl=Me), 6 (SIMes, Et), 7 (IPr, Me), 8 (SIPr, Me), and 9 (SIPr, Et) with N-chelating benzylidene ligands in yields of 50-75 %. Compared to their respective, conventional, O-Grubbs-Hoveyda complexes, the new complexes are characterized by fast catalyst activation, which translates into fast and efficient ring-closing metathesis (RCM) reactivity. Catalyst loadings of 15-150 ppm (0.0015-0.015 mol %) are sufficient for the conversion of a wide range of diolefinic substrates into the respective RCM products after 15 min at 50 °C in toluene; compounds 8 and 9 are the most catalytically active complexes. The use of complex 8 in RCM reactions enables the formation of N-protected 2,5-dihydropyrroles with turnover numbers (TONs) of up to 58,000 and turnover frequencies (TOFs) of up to 232,000 h(-1); the use of the N-protected 1,2,3,6-tetrahydropyridines proceeds with TONs of up to 37,000 and TOFs of up to 147,000 h(-1); and the use of the N-protected 2,3,6,7-tetrahydroazepines proceeds with TONs of up to 19,000 and TOFs of up to 76,000 h(-1), with yields for these reactions ranging from 83-92 %.

  18. Electron transfer-induced four-membered cyclic intermediate formation: Olefin cross-coupling vs. olefin cross-metathesis

    Energy Technology Data Exchange (ETDEWEB)

    Okada, Yohei [Department of Applied Life Science, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo 183-8509 (Japan); Chiba, Kazuhiro, E-mail: chiba@cc.tuat.ac.j [Department of Applied Life Science, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo 183-8509 (Japan)

    2011-01-01

    An electron transfer-induced four-membered cyclic intermediate, formed between a radical cation of an enol ether and an unactivated olefin, played a key role in the pathway toward either cross-coupling or cross-metathesis. The presence of an alkoxy group on the phenyl ring of the olefin entirely determined the synthetic outcome of the reaction, which mirrored the efficiency of the intramolecular electron transfer.

  19. High-Yield Process for Selectively Converting CO2 to Aromatics and Olefins Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This proposed Phase I addresses the selective conversion of CO2 to hydrocarbons via integrated CO2-to-methanol, methanol-to-olefins, and olefins-to-aromatics...

  20. The intriguing modeling of cis–trans selectivity in ruthenium-catalyzed olefin metathesis

    Directory of Open Access Journals (Sweden)

    Luigi Cavallo

    2011-01-01

    Full Text Available In this study we have investigated computationally the origin of the cis–trans selectivity in the Ru-catalyzed cross metathesis (CM of a prototype monosubstituted olefin, i.e., propene. Our calculations suggest that the origin of the preferential formation of trans-olefins is in the product release step, which prevents the initially formed cis-olefin from escaping the metal, and returns it to the reaction pool until the trans-olefin is formed.

  1. The intriguing modeling of cis–trans selectivity in ruthenium-catalyzed olefin metathesis

    Science.gov (United States)

    Bahri-Laleh, Naeimeh; Credendino, Raffaele

    2011-01-01

    Summary In this study we have investigated computationally the origin of the cis–trans selectivity in the Ru-catalyzed cross metathesis (CM) of a prototype monosubstituted olefin, i.e., propene. Our calculations suggest that the origin of the preferential formation of trans-olefins is in the product release step, which prevents the initially formed cis-olefin from escaping the metal, and returns it to the reaction pool until the trans-olefin is formed. PMID:21286393

  2. High performance cyclo olefin polymer ZEONEX

    Science.gov (United States)

    Konishi, Yuichiro; Sawaguchi, Taichi; Kubomura, Kyoichi; Minami, Koji

    2005-09-01

    Zeon Corporation developed quite new optical plastic Cyclo Olefin Polymer; COP(ZEONEX) with own technology in 1990 then started sales for ZEONEX for optical application with its very unique properties such as low birefringence, low water absorption, high glass-transition temperature 136 °C and high light transmission etc. Currently, ZEONEX is well known in optical market and used widely as optical plastic for pick up lens and other many kinds of optical parts for laser beam printer and digital camera. Addition to those ZEONEX grades, in last year, Zeon Corporation developed a new ZEONEX grade called ZEONEX340R, which was designed for blue laser devices requiring more severe specification. ZEONEX340R has high transmission at 405nm which is used laser wavelength for Blu-ray Disk / HD-DVD as well as enough durability under exposure of 405nm laser, addition to those new properties, keeps other optical properties such as low birefringence and very low water absorption.

  3. Thermally Stable, Latent Olefin Metathesis Catalysts

    Science.gov (United States)

    Thomas, Renee M.; Fedorov, Alexey; Keitz, Benjamin K.

    2011-01-01

    Highly thermally stable N-aryl,N-alkyl N-heterocyclic carbene (NHC) ruthenium catalysts were designed and synthesized for latent olefin metathesis. These catalysts showed excellent latent behavior toward metathesis reactions, whereby the complexes were inactive at ambient temperature and initiated at elevated temperatures, a challenging property to achieve with second generation catalysts. A sterically hindered N-tert-butyl substituent on the NHC ligand of the ruthenium complex was found to induce latent behavior toward cross-metathesis reactions, and exchange of the chloride ligands for iodide ligands was necessary to attain latent behavior during ring-opening metathesis polymerization (ROMP). Iodide-based catalysts showed no reactivity toward ROMP of norbornene-derived monomers at 25 °C, and upon heating to 85 °C gave complete conversion of monomer to polymer in less than 2 hours. All of the complexes were very stable to air, moisture, and elevated temperatures up to at least 90 °C, and exhibited a long catalyst lifetime in solution at elevated temperatures. PMID:22282652

  4. A fast-initiating ionically tagged ruthenium complex: a robust supported pre-catalyst for batch-process and continuous-flow olefin metathesis.

    Science.gov (United States)

    Borré, Etienne; Rouen, Mathieu; Laurent, Isabelle; Magrez, Magaly; Caijo, Fréderic; Crévisy, Christophe; Solodenko, Wladimir; Toupet, Loic; Frankfurter, René; Vogt, Carla; Kirschning, Andreas; Mauduit, Marc

    2012-12-14

    In this study, a new pyridinium-tagged Ru complex was designed and anchored onto sulfonated silica, thereby forming a robust and highly active supported olefin-metathesis pre-catalyst for applications under batch and continuous-flow conditions. The involvement of an oxazine-benzylidene ligand allowed the reactivity of the formed Ru pre-catalyst to be efficiently controlled through both steric and electronic activation. The oxazine scaffold facilitated the introduction of the pyridinium tag, thereby affording the corresponding cationic pre-catalyst in good yield. Excellent activities in ring-closing (RCM), cross (CM), and enyne metathesis were observed with only 0.5 mol % loading of the pre-catalyst. When this powerful pre-catalyst was immobilized onto a silica-based cationic-exchange resin, a versatile catalytically active material for batch reactions was generated that also served as fixed-bed material for flow reactors. This system could be reused at 1 mol % loading to afford metathesis products in high purity with very low ruthenium contamination under batch conditions (below 5 ppm). Scavenging procedures for both batch and flow processes were conducted, which led to a lowering of the ruthenium content to as little as one tenth of the original values.

  5. Synthesis of nisin AB dicarba analogs using ring-closing metathesis: influence of sp(3) versus sp(2) hybridization of the α-carbon atom of residues dehydrobutyrine-2 and dehydroalanine-5 on the lipid II binding affinity.

    Science.gov (United States)

    Slootweg, Jack C; van Herwerden, Eric F; van Doremalen, Mark F M; Breukink, Eefjan; Liskamp, Rob M J; Rijkers, Dirk T S

    2015-06-01

    Herein the synthesis of two nisin AB dicarba analogs is described, focusing on amino acid modifications at positions 2 and 5. The nisin mimics were synthesized by a combination of solid phase synthesis of the linear peptides, followed by macrocyclization via ring-closing metathesis and fragment assembly by means of solution phase chemistry. The two N-terminal nisin AB-fragment mimics contain either the native dehydrobutyrine (Dhb)/dehydroalanine (Dha) amino acid residues or alanine at position 2 and 5, respectively. The native dehydrobutyrine at position 2 and dehydroalanine at position 5 were introduced as their precursors, namely threonine and serine, respectively, and subsequent dehydration was carried out by EDCI/CuCl as the condensing agent. Both AB-fragment mimics were analyzed in a lipid II binding assay and it was found that the Ala2/Ala5 AB-mimic (2) showed a reduced activity, while the Dhb2/Dha5 AB-mimic (3) was as active as the native AB-fragment (1).

  6. A well-defined rhenium(VII) olefin metathesis catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Toreki, R.; Schrock, R.R. (Massachusetts Institute of Technology, Cambridge (USA))

    1990-03-14

    Molybdenum tungsten, and rhenium are the three most active metals in classical olefin metathesis systems. Molybdenum (VI){sup 2} and tungsten(VI){sup 3} alkylidene complexes of the type M-(CHR{prime})(NAr)(OR){sub 2} (Ar = 2,6-C{sub 6}H{sub 3}-i-Pr{sub 2}) have been shown to be well-behaved olefin metathesis catalysts with an activity that can be controlled through the choice of OR. Although several rhenium alkylidene complexes have been reported, none has shown any confirmable metathesis activity, even toward strained cyclic olefins such as norbornene. Since Re{triple bond}CR{double prime} and M{double bond}NR{double prime} (M = Mo or W) can be regarded as isoelectronic units, plausible candidates as olefin metathesis catalysts are complexes of the type Re(CHR{prime})(CR{double prime})(OR){sub 2}. The authors report here that such a complex in which OR = OCMe(CF{sub 3}){sub 2} is a well-behaved olefin metathesis catalyst.

  7. Low severity coal liquefaction promoted by cyclic olefins

    Energy Technology Data Exchange (ETDEWEB)

    Curtis, C.W.

    1992-01-01

    Low severity coal liquefaction promoted by cyclic olefins offers a means of liquefying coal at low severity conditions. Lower temperature, 350[degrees]C, and lower hydrogen pressure, 500 psi, have been used to perform liquefaction reactions. The presence of the cyclic olefin, hexahydroanthracene, made a substantial difference in the conversion of Illinois No. 6 coal at these low severity conditions. The Researchperformed this quarter was a parametric evaluation of the effect of different parameters on the coal conversion and product distribution from coal. The effect of the parameters on product distribution from hexahydroanthracene was also determined. The work planned for next quarter includes combining the most effective parametric conditions for the low severity reactions and determining their effect. The second part ofthe research performed this quarter involved performing Fourier transform infrared (FTIR) spectroscopy using cyclic olefins. The objective of this study was to determine the feasibility of using FTIR and a heated cell to determine the reaction pathway that occurs in the hydrogen donation reactions from cyclic olefins. The progress made to date includes evaluating the FTIR spectra of cyclic olefins and their expected reaction products. This work is included in this progress report.

  8. 40 CFR 721.5425 - α-Olefin sulfonate, potassium salts.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false α-Olefin sulfonate, potassium salts... Substances § 721.5425 α-Olefin sulfonate, potassium salts. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as an α-olefin sulfonate, potassium salt...

  9. 40 CFR 721.5450 - α-Olefin sulfonate, sodium salt.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false α-Olefin sulfonate, sodium salt. 721... Substances § 721.5450 α-Olefin sulfonate, sodium salt. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as α-olefin sulfonate, sodium...

  10. ORGANIC CHEMISTRY. Catalytic asymmetric hydroamination of unactivated internal olefins to aliphatic amines.

    Science.gov (United States)

    Yang, Yang; Shi, Shi-Liang; Niu, Dawen; Liu, Peng; Buchwald, Stephen L

    2015-07-01

    Catalytic assembly of enantiopure aliphatic amines from abundant and readily available precursors has long been recognized as a paramount challenge in synthetic chemistry. Here, we describe a mild and general copper-catalyzed hydroamination that effectively converts unactivated internal olefins—an important yet unexploited class of abundant feedstock chemicals—into highly enantioenriched α-branched amines (≥96% enantiomeric excess) featuring two minimally differentiated aliphatic substituents. This method provides a powerful means to access a broad range of advanced, highly functionalized enantioenriched amines of interest in pharmaceutical research and other areas.

  11. Green chemistry: C-C coupling and asymmetric reduction by innovative catalysis

    Institute of Scientific and Technical Information of China (English)

    Xiaofeng Wu; Jun Mo; Xiaohong Li; Zeyn Hyder; Jianliang Xiao

    2008-01-01

    A catalytic method has been developed, which allows aryl halides to couple with various electron-rich olefins to give 1, 1'-substituted olefins. The palladium-catalysed coupling in ionic liquid solvent proceeds with high efficiency and remarkable regioselectivity without the need for any costly or toxic halide scavengers. Parallel to this, an environmentally-appealing method for the asymmetric reduction of ketones has been established, with which a variety of chiral alcohols can be accessed with high enantioselectivity in water with no need for any organic solvents. The same chemistry has been explored for the reduction of aldehydes, which is shown to be fast and highly chemoselective. These methods add new tools to the armoury of synthetic chemists.

  12. Efficient Removal of Ruthenium Byproducts from Olefin Metathesis Products by Simple Aqueous Extraction

    Science.gov (United States)

    Hong, Soon Hyeok; Grubbs, Robert H.

    2008-01-01

    Simple aqueous extraction removed ruthenium byproducts efficiently from ring-closing metathesis (RCM) reactions catalyzed by a PEG-supported N-heterocyclic carbene-based ruthenium complex. PMID:17428062

  13. Ionic liquids for separation of olefin-paraffin mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Sheng; Luo, Huimin; Huang, Jing-Fang

    2014-07-15

    The invention is directed to an ionic liquid comprising (i) a cationic portion containing a complex of a silver (I) ion and one or more neutral ligands selected from organoamides, organoamines, olefins, and organonitriles, and (ii) an anionic portion having the chemical formula ##STR00001## wherein m and n are independently 0 or an integer of 1 or above, and p is 0 or 1, provided that when p is 0, the group --N--SO.sub.2--(CF.sub.2).sub.nCF.sub.3 subtended by p is replaced with an oxide atom connected to the shown sulfur atom. The invention is also directed to a method for separating an olefin from an olefin-paraffin mixture by passing the mixture through a layer of the ionic liquid described above.

  14. Low Severity Coal Liquefaction Promoted by Cyclic Olefins

    Energy Technology Data Exchange (ETDEWEB)

    Christine W. Curtis

    1998-04-09

    The development of the donor solvent technology for coal liquefaction has drawn a good deal of attention over the last three decades. The search for better hydrogen donors led investigators to a class of compounds known as cyclic olefins. Cyclic olefins are analogues of the conventional hydroaromatic donor species but do not contain aromatic rings. The cyclic olefins are highly reactive compounds which readily release their hydrogen at temperatures of 200 C or higher. Considerable effort has been o expended toward understanding the process of hydrogen donation. Most of this work was conducted in bomb reactors, with product analysis being carried out after the reaction was complete. Efforts directed towards fundamental studies of these reactions in situ are rare. The current work employs a high temperature and high pressure infrared cell to monitor in situ the concentrations of reactants and products during hydrogen release from hydrogen donor compounds.

  15. Review of Directly Producing Light Olefins via CO Hydrogenation

    Institute of Scientific and Technical Information of China (English)

    Chong Wang; Longya Xu; Qingxia Wang

    2003-01-01

    Directly making light olefins via CO hydrogenation is a promising process to obtain a non-petroleum based supply of alkenes. Limited by the ASF distribution function of Fischer-Tropsch synthesis,the yield of light olefins (C2-C4) can not reach the desired levels, which is a great challenge to overcome.Beginning with a brief introduction of F-T synthesis, this paper provides a review of current research,including thermodynamic analysis, the ASF distribution function, the reaction performance of CO hydro-genation and slurry reactor studies. The problems currently faced by this research area are presented atthe end of the article.

  16. The activation mechanism of Fe-based olefin metathesis catalysts

    Science.gov (United States)

    Poater, Albert; Pump, Eva; Vummaleti, Sai Vikrama Chaitanya; Cavallo, Luigi

    2014-08-01

    Density functional theory calculations have been used to describe the first turnover for olefin metathesis reaction of a homogenous Fe-based catalyst bearing a N-heterocyclic carbene ligand with methoxyethene as a substrate. Equal to conventional Ru-based catalysts, the activation of its Fe congener occurs through a dissociative mechanism, however with a more exothermic reaction energy profile. Predicted upper energy barriers were calculated to be on average ∼2 kcal/mol more beneficial for Fe catalyzed metathesis. Overall, this present computational study emphasises on advantages of Fe-based metathesis and gives a potential recipe for the design of an efficient Fe-based olefin metathesis catalysts.

  17. Cardanol-Based Materials as Natural Precursors for Olefin Metathesis

    Directory of Open Access Journals (Sweden)

    Giuseppe Vasapollo

    2011-08-01

    Full Text Available Cardanol is a renewable, low cost natural material, widely available as a by-product of the cashew industry. It is a mixture of 3-n-pentadecylphenol, 3-(pentadeca-8-enylphenol, 3-(pentadeca-8,11-dienylphenol and 3-(pentadeca-8,11,14-trienylphenol. Olefin metathesis (OM reaction on cardanol is an important class of reactions that allows for the synthesis of new olefins that are sometime impossible to prepare via other methods. The application of this natural and renewable material to both academic and industrial research will be discussed.

  18. Enhanced Olefin Cross Metathesis Reactions: The Copper Iodide Effect

    Science.gov (United States)

    Voigtritter, Karl; Ghorai, Subir

    2011-01-01

    Copper iodide has been shown to be an effective co-catalyst for the olefin cross metathesis reaction. In particular, it has both a catalyst stabilizing effect due to iodide ion, as well as copper(I)-based phosphine-scavenging properties that apply to use of the Grubbs-2 catalyst. A variety of Michael acceptors and olefinic partners can be cross-coupled under mild conditions in refluxing diethyl ether that avoid chlorinated solvents. This effect has also been applied to chemistry in water at room temperature using the new surfactant TPGS-750-M. PMID:21528868

  19. Comparing Ru and Fe-catalyzed olefin metathesis

    KAUST Repository

    Poater, Albert

    2014-01-01

    Density functional theory calculations have been used to explore the potential of Fe-based complexes with an N-heterocyclic carbene ligand, as olefin metathesis catalysts. Apart from a less endothermic reaction energy profile, a small reduction in the predicted upper energy barriers (≈ 2 kcal mol -1) is calculated in the Fe catalyzed profile with respect to the Ru catalysed profile. Overall, this study indicates that Fe-based catalysts have the potential to be very effective olefin metathesis catalysts. This journal is © the Partner Organisations 2014.

  20. Electrochemistry for biofuel generation: transformation of fatty acids and triglycerides to diesel-like olefin/ether mixtures and olefins.

    Science.gov (United States)

    dos Santos, Tatiane R; Harnisch, Falk; Nilges, Peter; Schröder, Uwe

    2015-03-01

    Electroorganic synthesis can be exploited for the production of biofuels from fatty acids and triglycerides. With Coulomb efficiencies (CE) of up to 50 %, the electrochemical decarboxylation of fatty acids in methanolic and ethanolic solutions leads to the formation of diesel-like olefin/ether mixtures. Triglycerides can be directly converted in aqueous solutions by using sonoelectrochemistry, with olefins as the main products (with a CE of more than 20 %). The latter reaction, however, is terminated at around 50 % substrate conversion by the produced side-product glycerol. An energy analysis shows that the electrochemical olefin synthesis can be an energetically competitive, sustainable, and--in comparison with established processes--economically feasible alternative for the exploitation of fats and oils for biofuel production.

  1. Synthetic Applications of Chiral Unsaturated Epoxy Alcohols Prepared by Sharpless Asymmetric Epoxidation

    Directory of Open Access Journals (Sweden)

    María Moreno

    2010-02-01

    Full Text Available An overview of the synthesis and applications of chiral 2,3-epoxy alcohols containing unsaturated chains is presented. One of the fundamental synthetic routes to these compounds is Sharpless asymmetric epoxidation, which is reliable, highly chemoselective and enables easy prediction of the product enantioselectivity. Thus, unsaturated epoxy alcohols are readily obtained by selective oxidation of the allylic double bond in the presence of other carbon-carbon double or triple bonds. The wide availability of epoxy alcohols with unsaturated chains, the versatility of the epoxy alcohol functionality (e.g. regio- and stereo-selective ring opening; oxidation; and reduction, and the arsenal of established alkene chemistries, make unsaturated epoxy alcohols powerful starting materials for the synthesis of complex targets such as biologically active molecules. The popularization of ring-closing metathesis has further increased their value, making them excellent precursors to cyclic compounds.

  2. Enantiopure C1-symmetric N-Heterocyclic Carbene Ligands from Desymmetrized meso-1,2-Diphenylethylenediamine: Application in Ruthenium-Catalyzed Olefin Metathesis

    Directory of Open Access Journals (Sweden)

    Veronica Paradiso

    2016-11-01

    Full Text Available In order to design improved chiral ruthenium catalysts for asymmetric olefin metathesis, enantiomeric catalysts incorporating C1-symmetric N-Heterocyclic carbenes (NHC ligands with syn-related substituents on the backbone were synthesized starting from meso-1,2-diphenylethylenediamine. The absolute configuration of the enantiomers of the desymmetrized meso diamine was assigned by optical rotation analysis and in silico calculations, and was found to be maintained in their respective ruthenium catalysts by comparison of the relative electronic circular dichroism (ECD spectra. The catalytic behaviour of the enantiomeric ruthenium complexes was investigated in model asymmetric metathesis transformations and compared to that of analogous complexes bearing C1-symmetric NHC ligands with an anti backbone. Modest enantioselectivities were registered and different catalyst properties depending on the nature of stereochemical relationship of substituents on the backbone were observed.

  3. Factors influencing ring closure through olefin metathesis - A perspective

    Indian Academy of Sciences (India)

    Subrata Ghosh; Sarita Ghosh; Niladri Sarkar

    2006-05-01

    Success of ring closure reactions of substrates having two terminal alkenes through olefin metathesis depends on a number of factors such as catalysts, nature and size of the rings to be formed and the substituents/functional groups present on the alkenes as well as at the allylic position. This article presents an overview of these influencing factors with illustrative examples.

  4. Sterically shielded diboron-containing metallocene olefin polymerization catalysts

    Science.gov (United States)

    Marks, Tobin J.; Ja, Li; Yang, Xinmin

    1995-09-05

    A non-coordinating anion, preferably containing a sterically shielded diboron hydride, if combined with a cyclopenta-dienyl-substituted metallocene cation component, such as a zirconocene metallocene, is a useful olefin polymerization catalyst component. The anion preferably has the formula ##STR1## where R is branched lower alkyl, such as t-butyl.

  5. Study on Olefins Yield from Methanol Conversion over Different Catalysts

    Institute of Scientific and Technical Information of China (English)

    Munib Shahda; Yan Dengchao; Wang Zhihe; Wen Huixin

    2006-01-01

    Conversion of Methanol to Olefins (MTO) under different reaction conditions was experimentally investigated over different catalysts, and comparison was made between the SAPO-34 and GOR-MLC catalysts. Optimization of reaction conditions has been explored. Conversion of methanol to olefins over these catalysts under different reaction temperatures was experimentally studied. In a fixed bed micro-reactor, the influence of temperature was found to be one of the major factors. For both catalysts the olefins yield was increased significantly when water was added to the methanol feed. A temperature range of 460-480 ℃ appeared to be the optimum range suitable for methanol conversion with appropriate catalyst activity and C2-C3 olefins yield. Some other hydrocarbons appeared during the MTO reaction in the presence of the SAPO-34 catalyst, while a lot of dimethylether was formed when the GOR-MLC catalyst was used. In the course of the MTO reaction, the GOR-MLC catalyst was found to have a faster catalyst deactivation rate compared to the SAPO-34 catalyst.

  6. ULTRASOUND-ASSISTED ORGANIC SYNTHESIS: ALCOHOL OXIDATION AND OLEFIN EPOXIDATION

    Science.gov (United States)

    Ultrasound-assisted Organic Synthesis: Alcohol Oxidation and Olefin EpoxidationUnnikrishnan R Pillai, Endalkachew Sahle-Demessie , Vasudevan Namboodiri, Quiming Zhao, Juluis EnriquezU.S. EPA , 26 W. Martin Luther King Dr. , Cincinnati, OH 45268 Phone: 513-569-773...

  7. Bio-olefins from unsaturated fatty acids via tandem catalysis

    Science.gov (United States)

    A new catalytic route to bio-olefins from unsaturated fatty acids will be described. At the heart of the process, the catalyst apparently functions in a tandem mode by both dynamically isomerizing the positions of double bonds in an aliphatic chain and, subsequently, decarboxylating specific isomers...

  8. Optical fibre Bragg grating recorded in TOPAS cyclic olefin copolymer

    DEFF Research Database (Denmark)

    Johnson, I.P.; Yuan, Scott Wu; Stefani, Alessio

    2011-01-01

    A report is presented on the inscription of a fibre Bragg grating into a microstructured polymer optical fibre fabricated from TOPAS cyclic olefin copolymer. This material offers two important advantages over poly (methyl methacrylate), which up to now has formed the basis for polymer fibre Bragg...

  9. Electrochemical Allylic Oxidation of Olefins: Sustainable and Safe.

    Science.gov (United States)

    Waldvogel, Siegfried R; Selt, Maximilian

    2016-10-01

    The power you're supplying: With the application of an optimized electrochemical approach, the allylic oxidation of olefins, which is an important C-H activation process that provides access to enones, becomes a sustainable, versatile, and potent key reaction for organic synthesis.

  10. Utilization of α-olefins obtained by pyrolysis of waste high density polyethylene to synthesize α-olefin-succinic-anhydride based cold flow improvers

    Institute of Scientific and Technical Information of China (English)

    Norbert MISKOLCZI; Richard SAGI; László BARTHA; Lívia FORCEK

    2009-01-01

    A new route of utilization of α-olefin rich hydrocarbon fractions obtained by waste polymer pyrolysis was investigated. α-olefin-succinic-anhydride intermediate-based pour point depressant additives for diesel fuel were synthesized, in which reactions needed α-olefins were obtained by pyrolysis of waste high-density polyethylene (HDPE). Fraction of α-olefins was produced by the de-polymerization of plastic waste in a tube reactor at 500℃ in the absence of catalysts and air. C17~22 range of mixtures of olefins and paraffins were separated for synthesis and then, these hydrocarbons were reacted with maleic-anhydride (MA) for formation of α-olefin-succinic-anhydride intermediates. The olefin-rich hydrocarbon fraction contained approximately 60% of olefins, including 90%~95% α-olefins. Other intermediates were produced in the same way by using commercial C20 α-olefin instead of C17~22 olefin mixture. The two different experimental intermediates with number average molecular weights of 1850g/mol and 1760g/mol were reacted with different alcohols: 1-butanol, 1-hexanol, 1-octanol, i-butanol, and c-hexanol to produce their ester derivatives. The synthesized ten experimental pour point depressants were added in different concentrations to conventional diesel fuel, which had no other additive content before. The structure and efficiency of experimental additives were followed by different standardized and non-standardized methods. Results showed that the experimental additives on the basis of the product of waste pyrolysis were able to decrease not only the pour but also the cloud point and cold filter plugging point (CFPP) of diesel fuel, whose effects could be observed even if the concentration of additives was low. Furthermore, all additives had anti-wear and anti-friction effects in diesel fuel.

  11. 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.

  12. 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 asymmet

  13. Asymmetric reactions in continuous flow

    Directory of Open Access Journals (Sweden)

    Xiao Yin Mak

    2009-04-01

    Full Text Available An overview of asymmetric synthesis in continuous flow and microreactors is presented in this review. Applications of homogeneous and heterogeneous asymmetric catalysis as well as biocatalysis in flow are discussed.

  14. Asymmetric catalysis with helical polymers

    NARCIS (Netherlands)

    Megens, Rik P.; Roelfes, Gerard

    2011-01-01

    Inspired by nature, the use of helical biopolymer catalysts has emerged over the last years as a new approach to asymmetric catalysis. In this Concept article the various approaches and designs and their application in asymmetric catalysis will be discussed.

  15. Synthesis of terminal alkenes from internal alkenes and ethylene via olefin metathesis

    Energy Technology Data Exchange (ETDEWEB)

    Schrodi, Yann (Agoura Hills, CA)

    2011-11-29

    This invention relates generally to olefin metathesis, and more particularly relates to the synthesis of terminal alkenes from internal alkenes using a cross-metathesis reaction catalyzed by a selected olefin metathesis catalyst. In one embodiment of the invention, for example, a method is provided for synthesizing a terminal olefin, the method comprising contacting an olefinic substrate comprised of at least one internal olefin with ethylene, in the presence of a metathesis catalyst, wherein the catalyst is present in an amount that is less than about 1000 ppm relative to the olefinic substrate, and wherein the metathesis catalyst has the structure of formula (II) ##STR00001## wherein the various substituents are as defined herein. The invention has utility, for example, in the fields of catalysis, organic synthesis, and industrial chemistry.

  16. Synthesis of terminal alkenes from internal alkenes and ethylene via olefin metathesis

    Energy Technology Data Exchange (ETDEWEB)

    Schrodi, Yann

    2015-09-22

    This invention relates generally to olefin metathesis, and more particularly relates to the synthesis of terminal alkenes from internal alkenes using a cross-metathesis reaction catalyzed by a selected olefin metathesis catalyst. In one embodiment of the invention, for example, a method is provided for synthesizing a terminal olefin, the method comprising contacting an olefinic substrate comprised of at least one internal olefin with ethylene, in the presence of a metathesis catalyst, wherein the catalyst is present in an amount that is less than about 1000 ppm relative to the olefinic substrate, and wherein the metathesis catalyst has the structure of formula (II) ##STR00001## wherein the various substituents are as defined herein. The invention has utility, for example, in the fields of catalysis, organic synthesis, and industrial chemistry.

  17. Synthesis of terminal alkenes from internal alkenes and ethylene via olefin metathesis

    Energy Technology Data Exchange (ETDEWEB)

    Schrodi, Yann

    2013-07-09

    This invention relates generally to olefin metathesis, and more particularly relates to the synthesis of terminal alkenes from internal alkenes using a cross-metathesis reaction catalyzed by a selected olefin metathesis catalyst. In one embodiment of the invention, for example, a method is provided for synthesizing a terminal olefin, the method comprising contacting an olefinic substrate comprised of at least one internal olefin with ethylene, in the presence of a metathesis catalyst, wherein the catalyst is present in an amount that is less than about 1000 ppm relative to the olefinic substrate, and wherein the metathesis catalyst has the structure of formula (II) ##STR00001## wherein the various substituents are as defined herein. The invention has utility, for example, in the fields of catalysis, organic synthesis, and industrial chemistry.

  18. Analysis of Measures and Effect on Reducing Olefin Content in Gasoline

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    This article refers to major measures for reducing olefin content of automotive gasoline and the effect after adoption of these measures. The key for reducing olefin content in China's automotive gasoline pool is to reduce the olefin content of FCC naphtha. The domestic refiners apply the olefinreducing catalyst to decrease the olefin content of FCC gasoline as a convenient and cheap means to meet the national standard for automotive gasoline at the present phase. Furthermore, the novel domestic FCC reaction processes, such as the MIP, MGD, FDFCC and other processes can also apparently reduce olefin content in FCC gasoline. In order to further reduce the olefin content in gasoline to meet more stringent standard for automotive gasoline, Chinese refiners should optimize the processing scheme while aggressively disseminating hydrogenation process along with development of catalytic reforming,alkylation, etherification and other processes to completely change the simplistic composition of domestic gasoline pool.

  19. Study on reformulation of fluid catalytic cracking gasoline and increasing production of light olefins

    Institute of Scientific and Technical Information of China (English)

    Pingxiang YAN; Xianghai MENG; Jinsen GAO; Chunmin XU; Zhiyu SUI

    2008-01-01

    The effects of reaction temperature, mass ratio of catalyst to oil, space velocity, and mass ratio of water to oil on the product distribution, the yields of light olefins (light olefins including ethylene, propylene and butylene) and the composition of the fluid catalytic cracking (FCC) gasoline upgraded over the self-made catalyst GL in a confined fluidized bed reactor were investigated. The experimental results showed that FCC gasoline was obviously reformulated under appropriate reaction con-ditions. The olefins (olefins with C atom number above 4) content of FCC gasoline was markedly reduced, and the aromatics content and octane number were increased. The upgraded gasoline met the new standard of gasoline, and meanwhile, higher yields of light olefins were obtained. Furthermore, higher reaction temperature, higher mass ratio of catalyst to oil, higher mass ratio of water to oil, and lower space velocity were found to be beneficial to FCC gasoline reformulation and light olefins production.

  20. Synthesis of terminal alkenes from internal alkenes and ethylene via olefin metathesis

    Energy Technology Data Exchange (ETDEWEB)

    Schrodi, Yann

    2016-02-09

    This invention relates generally to olefin metathesis, and more particularly relates to the synthesis of terminal alkenes from internal alkenes using a cross-metathesis reaction catalyzed by a selected olefin metathesis catalyst. In one embodiment of the invention, for example, a method is provided for synthesizing a terminal olefin, the method comprising contacting an olefinic substrate comprised of at least one internal olefin with ethylene, in the presence of a metathesis catalyst, wherein the catalyst is present in an amount that is less than about 1000 ppm relative to the olefinic substrate, and wherein the metathesis catalyst has the structure of formula (II) ##STR00001## wherein the various substituents are as defined herein. The invention has utility, for example, in the fields of catalysis, organic synthesis, and industrial chemistry.

  1. Ruthenium-Catalyzed Olefin Metathesis after Tetra-n-butylammonium Fluoride-Mediated Desilylation

    Science.gov (United States)

    Osman, Sami

    2012-01-01

    One-pot procedures expedite organic synthesis but pose challenges in that many reagents must be compatible with each other. We discovered that the presence of nBu4NF hindered rutheniumcatalyzed olefin metathesis when nBu4NF-mediated desilylation and olefin metathesis were performed in one pot. This problem could be solved by the addition of (TMS)2O to remove fluoride anions in order to facilitate the ruthenium-catalyzed olefin metathesis. PMID:23269856

  2. Copper-catalyzed intermolecular oxyamination of olefins using carboxylic acids and O-benzoylhydroxylamines

    Directory of Open Access Journals (Sweden)

    Brett N. Hemric

    2016-01-01

    Full Text Available This paper reports a novel approach for the direct and facile synthesis of 1,2-oxyamino moieties via an intermolecular copper-catalyzed oxyamination of olefins. This strategy utilizes O-benzoylhydroxylamines as an electrophilic amine source and carboxylic acids as a nucleophilic oxygen source to achieve a modular difunctionalization of olefins. The reaction proceeded in a regioselective manner with moderate to good yields, exhibiting a broad scope of carboxylic acid, amine, and olefin substrates.

  3. A latent ruthenium based olefin metathesis catalyst with a sterically demanding NHC ligand

    KAUST Repository

    Leitgeb, Anita

    2012-01-01

    An olefin metathesis catalyst featuring a SIPr NHC and an ester chelating carbene ligand is introduced. In contrast to its previously published SIMes analogue, only the trans dichloro configurated isomer was obtained. The two counterparts are tested in various olefin metathesis reactions, revealing a striking superiority of the new complex in the cross metathesis of olefins with methyl vinyl ketone allowing for full conversion with only 500 ppm catalyst loading. © 2012 The Royal Society of Chemistry.

  4. The activation mechanism of Fe-based olefin metathesis catalysts

    KAUST Repository

    Poater, Albert

    2014-08-01

    Density functional theory calculations have been used to describe the first turnover for olefin metathesis reaction of a homogenous Fe-based catalyst bearing a N-heterocyclic carbene ligand with methoxyethene as a substrate. Equal to conventional Ru-based catalysts, the activation of its Fe congener occurs through a dissociative mechanism, however with a more exothermic reaction energy profile. Predicted upper energy barriers were calculated to be on average ∼2 kcal/mol more beneficial for Fe catalyzed metathesis. Overall, this present computational study emphasises on advantages of Fe-based metathesis and gives a potential recipe for the design of an efficient Fe-based olefin metathesis catalysts. © 2014 Elsevier B.V.

  5. Methanol conversion to lower olefins over RHO type zeolite

    KAUST Repository

    Masih, Dilshad

    2013-07-01

    Eight-membered ring small-pore zeolite of RHO-type topology has been synthesized, characterized and tested for methanol-to-olefin (MTO) reaction. The zeolite was hydrothermally crystallized from the gel with Si/Al ratio of 5.0. It showed a high BET specific surface area (812 m2 g-1), micropore volume (0.429 cm3 g-1), and acid amount (2.53 mmol g-1). Scanning electron microscopy observations showed small crystallites of about 1 μm. The zeolite was active for MTO reaction with 100% methanol conversions at 623-723 K, whereas selectivity to lower olefins changed with time. © 2013 Elsevier B.V.

  6. Vanadyl cationic complexes as catalysts in olefin oxidation.

    Science.gov (United States)

    Nunes, Carla D; Vaz, Pedro D; Félix, Vítor; Veiros, Luis F; Moniz, Tânia; Rangel, Maria; Realista, Sara; Mourato, Ana C; Calhorda, Maria José

    2015-03-21

    Three new mononuclear oxovanadium(IV) complexes [VO(acac)(R-BIAN)]Cl (BIAN = 1,2-bis{(R-phenyl)imino}acenaphthene, R = H, 1; CH3, 2; Cl, 3) were prepared and characterized. They promoted the catalytic oxidation of olefins such as cyclohexene, cis-cyclooctene, and styrene with both tbhp (tert-butylhydroperoxide) and H2O2, and of enantiopure olefins (S(-)- and R(+)-pinene, and S(-)- and R(+)-limonene) selectively to their epoxides, with tbhp as the oxidant. The TOFs for styrene epoxidation promoted by complex 3 with H2O2 (290 mol mol(-1)V h(-1)) and for cis-cyclooctene epoxidation by 2 with tbhp (248 mol mol(-1)V h(-1)) are particularly good. Conversions reached 90% for several systems with tbhp, and were lower with H2O2. A preference for the internal C=C bond, rather than the terminal one, was found for limonene. Kinetic data indicate an associative process as the first step of the reaction and complex [VO(acac)(H-BIAN)](+) (1(+)) was isolated in an FTICR cell after adding tbhp to 1. EPR studies provide evidence for the presence of a V(IV) species in solution, until at least 48 hours after the addition of tbhp and cis-cyclooctene, and cyclic voltammetry studies revealed an oxidation potential above 1 V for complex 1. DFT calculations suggest that a [VO(H-BIAN)(MeOO)](+) complex is the likely active V(IV) species in the catalytic cycle from which two competitive mechanisms for the reaction proceed, an outer sphere path with an external attack of the olefin at the coordinated peroxide, and an inner sphere mechanism starting with a complex with the olefin coordinated to vanadium.

  7. 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

  8. Retrofit with membrane the Paraffin/Olefin separation

    Energy Technology Data Exchange (ETDEWEB)

    Motelica, A.; Bruinsma, O.S.L.; Kreiter, R.; Den Exter, M.J.; Vente, J.F. [ECN Biomass and Energy Efficiency, Petten (Netherlands)

    2012-10-15

    Olefins, such as ethylene, propylene, and butadiene, are among the most produced intermediates in petrochemical industry. They are produced from a wide range of hydrocarbon feedstocks (ethane, propane, butane, naphtha, gas oil) via a cracking process. The last step in this process is the separation of olefins from other hydrocarbons, which is traditionally performed with distillation. As the physicochemical properties, such as volatility and boiling point, of the compounds are very similar, the purification becomes capital and energy intensive. For example, the top of an ethylene/ethane distillation column needs to be chilled to -30C and this requires large amount of electric energy consumption. The separation of butadiene from the C4-fraction is performed with the aid of an additional solvent. This solvent has to be regenerated at the cost of additional high temperature steam. To overcome these separation disadvantages of olefin/paraffin separation, different separation methods have been investigated and proposed in recent years. Suggested options are based on better heat integration of the overall process, or on novel separation systems such as Heat Integrated Distillation Columns, membrane separation, adsorption-desorption systems or on hybrid separation methods, for example, distillation combined with membrane separation.

  9. A diversity-oriented approach to spirocyclic and fused hydantoins via olefin metathesis.

    Science.gov (United States)

    Dhara, Kalyan; Midya, Ganesh Chandra; Dash, Jyotirmayee

    2012-09-21

    An efficient and general method is reported to prepare a diverse series of 5,5-spirocyclic and 1,5-, 4,5-, and 3,4-fused bicyclic imidazolidinone derivatives based on selective alkylation and ring closing metathesis (RCM) by exploiting the four possible points of diversity in the hydantoin ring. Hydantoins containing trienes and tetraenes undergo selective RCM and cross metathesis to afford functionalized spirohydantoins. A tandem metathesis sequence involving ring closing-ring opening-ring closing and cross metathesis (RC-RO-RC-CM) occurred with a hydantoin triene to give a bicyclic hydantoin dimer in high yield. The fused bicylic dimer could participate in cross metathesis to produce a functionalized fused hydantoin derivative. The methodology establishes novel routes to unnatural amino acids, proline homologues, and cyclic vicinal diamines.

  10. Asymmetric Hydrogenation of Ketones-Design of Chiral Catalysts

    Institute of Scientific and Technical Information of China (English)

    Takeshi Ohkuma

    2005-01-01

    @@ 1Introduction Asymmetric hydrogenation of ketones is one of the most reliable methods for obtaining chiral secondary alcohols. This transformation is not only of academic interest, but also of industrial significance because of its simplicity, environmental friendliness, and economic viability. Chiral RuXY(binap)(1,2-diamine) complexes (BINAP = 2,2'-bis(diphenyl-phosphino)-1, 1'-binaphthyl,X = Y = C1 or X = H, Y = BH4) with[1] or without[2] a strong base catalyze rapid, highly productive asymmetric hydrogenation of various simple ketones in 2-propanol. This reaction, unlike conventional hydrogenation, proceeds selectively at a C = O bond leaving coexisting C = C linkages intact. A range of chiral alcohols are accessible in high enantiomeric purity from aromatic,heteroaromatic, olefinic, and amino ketones by this method[1,2]. However, no universal chiral catalysts exist due to the structural diversity of ketonic substrates. Thus, tert-alkyl ketones and 1-tetralones have remained difficult to be hydrogenated with high reactivity and enantioselectivity. We here report that this problem can be resolved by the use of BINAP/PICA-Ru (PICA = α-picolylamine)[3] or BINAP/1,4-diamine-Ru[4] complexes as catalysts.

  11. Observation of Different Catalytic Activity of Various 1-Olefins during Ethylene/1-Olefin Copolymerization with Homogeneous Metallocene Catalysts

    Directory of Open Access Journals (Sweden)

    Mingkwan Wannaborworn

    2011-01-01

    Full Text Available This research aimed to investigate the copolymerization of ethylene and various 1-olefins. The comonomer lengths were varied from 1-hexene (1-C6 up to 1-octadecene (1-C18 in order to study the effect of comonomer chain length on the activity and properties of the polymer in the metallocene/MAO catalyst system. The results indicated that two distinct cases can be described for the effect of 1-olefin chain length on the activity. Considering the short chain length comonomers, such as 1-hexene, 1-octene and 1-decene, it is obvious that the polymerization activity decreased when the length of comonomer was higher, which is probably due to increased steric hindrance at the catalytic center hindering the insertion of ethylene monomer to the active sites, hence, the polymerization rate decreased. On the contrary, for the longer chain 1-olefins, namely 1-dodecene, 1-tetradecene and 1-octadecene, an increase in the comonomer chain length resulted in better activity due to the opening of the gap aperture between Cp(centroid-M-Cp-(centroid, which forced the coordination site to open more. This effect facilitated the polymerization of the ethylene monomer at the catalytic sites, and thus, the activity increased. The copolymers obtained were further characterized using thermal analysis, X-ray diffraction spectroscopy and 13C-NMR techniques. It could be seen that the melting temperature and comonomer distribution were not affected by the 1-olefin chain length. The polymer crystallinity decreased slightly with increasing comonomer chain length. Moreover, all the synthesized polymers were typical LLDPE having random comonomer distribution.

  12. Asymmetric information and economics

    Science.gov (United States)

    Frieden, B. Roy; Hawkins, Raymond J.

    2010-01-01

    We present an expression of the economic concept of asymmetric information with which it is possible to derive the dynamical laws of an economy. To illustrate the utility of this approach we show how the assumption of optimal information flow leads to a general class of investment strategies including the well-known Q theory of Tobin. Novel consequences of this formalism include a natural definition of market efficiency and an uncertainty principle relating capital stock and investment flow.

  13. Asymmetric extractions in orthodontics

    OpenAIRE

    Camilo Aquino Melgaço; Mônica Tirre de Souza Araújo

    2012-01-01

    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 Portugue...

  14. 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.

  15. 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.

  16. Synthetic Strategies for Converting Carbohydrates into Carbocycles by the Use of Olefin Metathesis

    DEFF Research Database (Denmark)

    Madsen, Robert

    2007-01-01

    , protecting groups and substituents. Subsequent ring-closing metathesis with a ruthenium carbene complex affords highly functionalized carbocycles with ring-sizes ranging from five- to eight-membered rings. The application of these methods for the synthesis of carbocyclic natural products from carbohydrates......This microreview covers recent advances in the use of ring-closing metathesis for the synthesis of carbocycles from carbohydrates. Various strategies for the synthesis of a,w-dienes from carbohydrates are presented, which give rise to a large variety of dienes with different stereochemistry...

  17. Redox-Neutral Rh(III)-Catalyzed Olefination of Carboxamides with Trifluoromethyl Allylic Carbonate.

    Science.gov (United States)

    Park, Jihye; Han, Sangil; Jeon, Mijin; Mishra, Neeraj Kumar; Lee, Seok-Yong; Lee, Jong Suk; Kwak, Jong Hwan; Um, Sung Hee; Kim, In Su

    2016-11-18

    The rhodium(III)-catalyzed olefination of various carboxamides with α-CF3-substituted allylic carbonate is described. This reaction provides direct access to linear CF3-allyl frameworks with complete trans-selectivity. In particular, a rhodium catalyst provided Heck-type γ-CF3-allylation products via the β-O-elimination of rhodacycle intermediate and subsequent olefin migration process.

  18. Olefin cross-metathesis for the synthesis of alkenyl acyclonucleoside phosphonates.

    Science.gov (United States)

    Bessières, Maxime; De Schutter, Coralie; Roy, Vincent; Agofoglio, Luigi A

    2014-12-12

    The detailed synthetic protocol for the straightforward, efficient synthesis of various alkenyl acyclonucleosides, including challenging trisubstituted alkenyl acyclonucleoside phosphonates, is described. The key step of those syntheses is an olefin cross-metathesis reaction between two olefins selected based on their reactivity using well-defined ruthenium alkylidene catalysts.

  19. Design and Application of Latent Olefin Metathesis Catalysts Featuring S-Chelating Alkylidene Ligands

    Science.gov (United States)

    Szadkowska, Anna; Grela, Karol

    This review article is devoted to recent advances in the design and application of so-called “dormant” or “latent” ruthenium olefin metathesis catalysts bearing S-chelating alkylidene ligands. Selected ruthenium complexes containing S-donor ligands, which possess controllable initiation behaviour are presented. Applications of these complexes in olefin metathesis are described.

  20. PRECISE SYNTHESIS OF OLEFIN BLOCK COPOLYMERS USING A SYNDIOSPECIFIC LIVING POLYMERIZATION SYSTEM

    Institute of Scientific and Technical Information of China (English)

    Zheng-guo Cai; Hai-hui Su; Takeshi Shiono

    2013-01-01

    This feature article summarizes the synthesis of novel olefin block copolymers using fast syndiospecific living homo-and copolymerization of propylene,higher 1-alkene,and norbomene with ansa-fluorenylamidodimethyltitaniumbased catalyst according to the authors' recent results.The catalytic synthesis of monodisperse polyolefin and olefin block copolymer was also described using this living system.

  1. Beyond ketonization: selective conversion of carboxylic acids to olefins over balanced Lewis acid-base pairs.

    Science.gov (United States)

    Baylon, Rebecca A L; Sun, Junming; Martin, Kevin J; Venkitasubramanian, Padmesh; Wang, Yong

    2016-04-11

    We report the direct conversion of mixed carboxylic acids to C-C olefins with up to 60 mol% carbon yield through cascade (cross) ketonization, (cross) aldolization and self-deoxygenation reactions. Co-feeding hydrogen provides an additional ketone hydrogenation/dehydration pathway to a wider range of olefins.

  2. Application of olefin cross-metathesis to organometallics. Synthesis of unsaturated ferrocenyl alcohols and ketones

    Science.gov (United States)

    Seshadri; Lovely

    2000-02-10

    [reaction: see text] The application of olefin cross-metathesis to terminally unsaturated alpha-hydroxy- and alpha-ketoferrocenes is reported. Both substrates provided the terminally functionalized olefins in moderate to good yield. These examples represent the first cases of cross-metathesis of substrates containing an organometallic functional group.

  3. Oxidative cracking of n-Hexane : a catalytic pathway to olefins

    NARCIS (Netherlands)

    Boyadjian, Cassia

    2010-01-01

    Steam cracking, the major, current existing route for light olefin production, is the most energy consuming process in the chemical industry. The need for an energy efficient processes, urged substantial research work for the development of new catalytic technologies for light olefin production. Ste

  4. Direct production of lower olefins from synthesis gas using supported iron catalysts

    NARCIS (Netherlands)

    Torres Galvis, H.M.

    2013-01-01

    Lower olefins (ethylene, propylene and butylenes) are important commodity chemicals used for the manufacture of, amongst others, plastics, solvents and lubricants to cosmetics and drugs. C2 to C4 olefins are conventionally produced by steam cracking of naphtha. In view of economic, strategic, and en

  5. Studies on Catalyst Deactivation Rate and Byproducts Yield during Conversion of Methanol to Olefins

    Institute of Scientific and Technical Information of China (English)

    Yan Dengchao; Munib Shahda; Weng Huixin

    2006-01-01

    The conversion of methanol to olefins (MTO) over the SAPO-34 catalyst in fixed-bed microreactor was studied. The effect of reaction temperatures for methanol conversion to olefins and byproducts was investigated. A temperature of 425 ℃ appeared to be the optimum one suitable for conversion of methanol to olefins. Since the presence of water could increase the olefins selectivity, the methanol conversion reactions with mixed water/methanol feed were also studied. The effect of weight hourly space velocity on conversion of methanol was also studied. The results indicated that the olefins selectivity was significantly increased as WHSV increased till approximately 7.69 h-1 then it began to level off. Different factors affecting the catalyst deactivation rate was studied, showing that the catalyst deactivation time was dependent on reaction conditions, and temperatures higher and lower than the optimal one made the catalyst deactivation faster.Adding water to methanol could slow down the catalyst deactivation rate.

  6. Highly Selective Conversion of Olefin Components in FCC Gasoline to Propylene in Monolithic Catalytic Reactors

    Institute of Scientific and Technical Information of China (English)

    Li Yang; Shao Qian; He Zhenfu; Tian Huiping; Long Jun

    2006-01-01

    The demand for propylene has been growing recently. The concentration of olefins in the gasoline is strictly limited by the related environmental regulations. The olefins contained in the gasoline used as the feed could be cracked into light olefins to slash the olefin concentration in the gasoline to yield more propylene at the same time. The monolithic catalyst washcoated on the modified ZSM-5 zeolite was used in the experiments. The effect of the temperature, the Si/A1 ratio in ZSM-5 and the addition of the rare earth elements on the selectivities and the yields of the light olefins were studied. The high yields of propylene and butene could be obtained under the experimental conditions of a higher temperature and Si/A1 ratio with the addition of rare earth elements.

  7. Catalytic Transformation of Bio-oil to Olefins with Molecular Sieve Catalysts

    Science.gov (United States)

    Huang, Wei-wei; Gong, Fei-yan; Zhai, Qi; Li, Quan-xin

    2012-08-01

    Catalytic conversion of bio-oil into light olefins was performed by a series of molecular sieve catalysts, including HZSM-5, MCM-41, SAPO-34 and Y-zeolite. Based on the light olefins yield and its carbon selectivity, the production of light olefins decreased in the following order: HZSM-5>SAPO-34>MCM-41> Y-zeolite. The highest olefins yield from bio-oil using HZSM-5 catalyst reached 0.22 kg/kgbio-oil with carbon selectivity of 50.7% and a nearly complete bio-oil conversion. The reaction conditions and catalyst characterization were investigated in detail to reveal the relationship between the catalyst structure and the production of olefins. The comparison between the pyrolysis and catalytic pyrolysis of bio-oil was also performed.

  8. 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

  9. Asymmetric flow networks

    OpenAIRE

    Olaizola Ortega, María Norma; Valenciano Llovera, Federico

    2012-01-01

    This paper provides a new model of network formation that bridges the gap between the two benchmark models by Bala and Goyal, the one-way flow model, and the two-way flow model, and includes both as particular extreme cases. As in both benchmark models, in what we call an "asymmetric flow" network a link can be initiated unilaterally by any player with any other, and the flow through a link towards the player who supports it is perfect. Unlike those models, in the opposite direction there is ...

  10. Reversible and irreversible processing of biogenic olefins on acidic aerosols

    Directory of Open Access Journals (Sweden)

    J. Liggio

    2008-04-01

    Full Text Available Recent evidence has suggested that heterogeneous chemistry of oxygenated hydrocarbons, primarily carbonyls, plays a role in the formation of secondary organic aerosol (SOA; however, evidence is emerging that direct uptake of alkenes on acidic aerosols does occur and can contribute to SOA formation. In the present study, significant uptake of monoterpenes, oxygenated monoterpenes and sesquiterpenes to acidic sulfate aerosols is found under various conditions in a reaction chamber. Proton transfer mass spectrometry is used to quantify the organic gases, while an aerosol mass spectrometer is used to quantify the organic mass uptake and obtain structural information for heterogeneous products. Aerosol mass spectra are consistent with several mechanisms including acid catalyzed olefin hydration, cationic polymerization and organic ether formation, while measurable decreases in the sulfate mass on a per particle basis suggest that the formation of organosulfate compounds is also likely. A portion of the heterogeneous reactions appears to be reversible, consistent with reversible olefin hydration reactions. A slow increase in the organic mass after a fast initial uptake is attributed to irreversible reactions, consistent with polymerization and organosulfate formation. Uptake coefficients (γ were estimated for a fast initial uptake governed by the mass accommodation coefficient (α and ranged from 1×10-6-2.5×10-2. Uptake coefficients for a subsequent slower reactive uptake ranged from 1×10-7-1×10-4. These processes may potentially lead to a considerable amount of SOA from the various biogenic hydrocarbons under acidic conditions, which can be highly significant for freshly nucleated aerosols, particularly given the large array of atmospheric olefins.

  11. Reversible and irreversible processing of biogenic olefins on acidic aerosols

    Directory of Open Access Journals (Sweden)

    J. Liggio

    2007-08-01

    Full Text Available Recent evidence has suggested that heterogeneous chemistry of oxygenated hydrocarbons, primarily carbonyls, plays a role in the formation of secondary organic aerosol (SOA; however, evidence is emerging that direct uptake of alkenes on acidic aerosols does occur and can contribute to SOA formation. In the present study, significant uptake of monoterpenes, oxygenated monoterpenes and sesquiterpenes to acidic sulfate aerosols is found under various conditions in a reaction chamber. Proton transfer mass spectrometry is used to quantify the organic gases, while an aerosol mass spectrometer is used to quantify the organic mass uptake and obtain structural information for heterogeneous products. Aerosol mass spectra are consistent with several mechanisms including acid catalyzed olefin hydration, cationic polymerization and organic ester formation, while measurable decreases in the sulfate mass on a per particle basis suggest that the formation of organosulfate compounds is also likely. A portion of the heterogeneous reactions appears to be reversible, consistent with reversible olefin hydration reactions. A slow increase in the organic mass after a fast initial uptake is attributed to irreversible reactions, consistent with polymerization and organosulfate formation. Uptake coefficients (γ were estimated for a fast initial uptake governed by the mass accommodation coefficient (α and ranged from 1×10-6–2.5×10−2. Uptake coefficients for a subsequent slower reactive uptake ranged from 1×10-7–1×10-4. These processes are estimated to potentially produce greater than 2.5 μg m−3 of SOA from the various biogenic hydrocarbons under atmospheric conditions, which can be highly significant given the large array of atmospheric olefins.

  12. Reversible and irreversible processing of biogenic olefins on acidic aerosols

    Science.gov (United States)

    Liggio, J.; Li, S.-M.

    2008-04-01

    Recent evidence has suggested that heterogeneous chemistry of oxygenated hydrocarbons, primarily carbonyls, plays a role in the formation of secondary organic aerosol (SOA); however, evidence is emerging that direct uptake of alkenes on acidic aerosols does occur and can contribute to SOA formation. In the present study, significant uptake of monoterpenes, oxygenated monoterpenes and sesquiterpenes to acidic sulfate aerosols is found under various conditions in a reaction chamber. Proton transfer mass spectrometry is used to quantify the organic gases, while an aerosol mass spectrometer is used to quantify the organic mass uptake and obtain structural information for heterogeneous products. Aerosol mass spectra are consistent with several mechanisms including acid catalyzed olefin hydration, cationic polymerization and organic ether formation, while measurable decreases in the sulfate mass on a per particle basis suggest that the formation of organosulfate compounds is also likely. A portion of the heterogeneous reactions appears to be reversible, consistent with reversible olefin hydration reactions. A slow increase in the organic mass after a fast initial uptake is attributed to irreversible reactions, consistent with polymerization and organosulfate formation. Uptake coefficients (γ) were estimated for a fast initial uptake governed by the mass accommodation coefficient (α) and ranged from 1×10-6-2.5×10-2. Uptake coefficients for a subsequent slower reactive uptake ranged from 1×10-7-1×10-4. These processes may potentially lead to a considerable amount of SOA from the various biogenic hydrocarbons under acidic conditions, which can be highly significant for freshly nucleated aerosols, particularly given the large array of atmospheric olefins.

  13. Synthesis of thermoplastic poly(ester-olefin elastomers

    Directory of Open Access Journals (Sweden)

    Tanasijević Branka

    2004-01-01

    Full Text Available A series of thermoplastic poly(ester-olefin elastomers, based on poly(ethylene-stat-butylene, HO-PEB-OH, as the soft segment and poly (butylene terephthalate, PBT, as the hard segment, were synthesized by a catalyzed transesterification reaction in solution. The incorporation of soft hydrogenated poly(butadiene segments into the copolyester backbone was accomplished by the polycondensation of α, ω-dihydroxyl telechelic HO-PEB-OH, (PEB Mn = 3092 g/mol with 1,4-butanediol (BD and dimethyl terephthalate (DMT in the presence of a 50 wt-% high boiling solvent i.e., 1,2,4-trichlorobenzene. The molar ratio of the starting comonomers was selected to result in a constant hard to soft weight ratio of 60:40. The synthesis was optimized in terms of both the concentration of catalyst, tetra-n-butyl-titanate (Ti(OBu4, and stabilizer, N,N'-diphenyl-p-phenylenediamine (DPPD, as well as the reaction time. It was found that the optimal catalyst concentration (Ti(OBu4 for the synthesis of these thermoplastic elastomers was 1.0 mmol/mol ester and the optimal DPPD concentration was 1.0 wt-%. The extent of the reaction was followed by measuring the inherent viscosity of the reaction mixture. The effectiveness of the incorporation of the soft segments into the copolymer chains was proved by Soxhlet extraction with chloroform. The molecular structures, composition and the size of the synthesized poly(ester-butylenes were verified by 1H NMR spectroscopy, viscometry of dilute solutions and the complex dynamic melt viscosity. The thermal properties of poly(ester-olefins were investigated by differential scanning calorimetry (DSC. The degree of crystallinity was also determined by DSC. The thermal and thermo-oxidative stability were investigated by thermogravimetric analysis (TGA. The rheological properties of poly(ester-olefins were investigated by dynamic mechanical spectroscopy in the melt and solid state.

  14. Thermoplastic Adhesives based on polyolefin and olefinic copolymers

    Science.gov (United States)

    Paul, Rituparna

    2014-03-01

    H.B. Fuller has been a leading global industrial adhesive manufacturer for over 125 years. It is a company with a rich history of consistently delivering adhesive innovations for enhancing product performance in the market place. H.B. Fuller technologies/products find application in several markets including packaging, personal hygiene and nonwovens, durable assembly and electronics. In this presentation, H. B. Fuller's technology innovation journey will be shared with emphasis on groundbreaking technologies/products based on polyolefin and olefin copolymers.

  15. Alkyl and Hydride-Olefin Complexes of Niobocene

    NARCIS (Netherlands)

    Klazinga, A.H.; Teuben, J.H.

    1980-01-01

    Reactions of Cp2NbCl2 with RMgCl (R = n-C3H7, i-C3H7, n-C4H9, s-C4H9 and n-C5H11) give niobocene hydride olefin complexes Cp2Nb(H)L (L = C3H6, C4H8 and C5H10). The last step of the reaction probably proceeds via a stereospecific β-H elimination from the monoalkyl species Cp2NbR. Decomposition of n-a

  16. Separation of Olefin/Paraffin Mixtures with Carrier Facilitated Membrane Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Merkel, T.C.; Blanc, R.; Zeid, J.; Suwarlim, A.; Firat, B.; Wijmans, H.; Asaro, M. (SRI); Greene, M.(Lummus)

    2007-03-12

    This document describes the results of a DOE funded joint effort of Membrane Technology and Research Inc. (MTR), SRI International (SRI), and ABB Lummus (ABB) to develop facilitated transport membranes for olefin/paraffin separations. Currently, olefin/paraffin separation is done by distillation—an extremely energy-intensive process because of the low relative volatilities of olefins and paraffins. If facilitated transport membranes could be successfully commercialized, the potential energy savings achievable with this membrane technology are estimated to be 48 trillion Btu per year by the year 2020. We discovered in this work that silver salt-based facilitated transport membranes are not stable even in the presence of ideal olefin/paraffin mixtures. This decline in membrane performance appears to be caused by a previously unrecognized phenomenon that we have named olefin conditioning. As the name implies, this mechanism of performance degradation becomes operative once a membrane starts permeating olefins. This project is the first study to identify olefin conditioning as a significant factor impacting the performance of facilitated olefin transport membranes. To date, we have not identified an effective strategy to mitigate the impact of olefin conditioning. other than running at low temperatures or with low olefin feed pressures. In our opinion, this issue must be addressed before further development of facilitated olefin transport membranes can proceed. In addition to olefin conditioning, traditional carrier poisoning challenges must also be overcome. Light, hydrogen, hydrogen sulfide, and acetylene exposure adversely affect membrane performance through unwanted reaction with silver ions. Harsh poisoning tests with these species showed useful membrane lifetimes of only one week. These tests demonstrate a need to improve the stability of the olefin complexing agent to develop membranes with lifetimes satisfactory for commercial application. A successful effort

  17. Additive Effects on Asymmetric Catalysis.

    Science.gov (United States)

    Hong, Liang; Sun, Wangsheng; Yang, Dongxu; Li, Guofeng; Wang, Rui

    2016-03-23

    This review highlights a number of additives that can be used to make asymmetric reactions perfect. Without changing other reaction conditions, simply adding additives can lead to improved asymmetric catalysis, such as reduced reaction time, improved yield, or/and increased selectivity.

  18. Z-Selective Catalytic Olefin Cross-Metathesis

    Science.gov (United States)

    Meek, Simon J.; O’Brien, Robert V.; Llaveria, Josep; Schrock, Richard R.; Hoveyda, Amir H.

    2011-01-01

    Alkenes are found in a great number of biologically active molecules and are employed in numerous transformations in organic chemistry. Many olefins exist as E or higher energy Z isomers. Catalytic procedures for stereoselective formation of alkenes are therefore valuable; nonetheless, methods for synthesis of 1,2-disubstituted Z olefins are scarce. Here we report catalytic Z-selective cross-metathesis reactions of terminal enol ethers, which have not been reported previously, and allylic amides, employed thus far only in E-selective processes; the corresponding disubstituted alkenes are formed in up to >98% Z selectivity and 97% yield. Transformations, promoted by catalysts that contain the highly abundant and inexpensive molybdenum, are amenable to gram scale operations. Use of reduced pressure is introduced as a simple and effective strategy for achieving high stereoselectivity. Utility is demonstrated by syntheses of anti-oxidant C18 (plasm)-16:0 (PC), found in electrically active tissues and implicated in Alzheimer’s disease, and the potent immunostimulant KRN7000. PMID:21430774

  19. Effect of Olefins on Formation of Sulfur Compounds in FCC Gasoline

    Institute of Scientific and Technical Information of China (English)

    Tang Jinlian; Xu Youhao; Gong Jianhong; Wang Xieqing

    2008-01-01

    The effect of olefins on formation of sulfur compounds in FCC gasoline was studied in a small-scale fixed fluidized bed (FFB) unit at temperatures ranging from 400℃ to 500℃, a weight hourly space velocity (WHSV) of 10 h-1, and a catalyst/oil ratio of 6. The results showed that C4-C6 olefins contained in the FCC gasoline could react with H2S to form predominantly thiophenes, alkyl-thiophenes as well as a fractional amount of thiols, while large molecular olefins such as heptene could react with hydrogen sulfide to form benzothiophenes. The amount of sulfur compounds formed at different tem-peratures over different catalysts were in proportion to the mass fractions of olefins in the feedstock,with the amount of sulfur compounds formed over REUSY catalyst exceeding those formed over the shape selective zeolite catalyst owing to the effect of catalyst performance and the impact of catalyst on the degree of olefin conversion. The amount of sulfur compounds generated and their increase reached a maximum at 450℃ and a minimum at 400℃ because of the influence of temperature on the thermody-namic and kinetic constants for formation of sulfur compound as well as on the olefin conversion degree.Based on the above-mentioned study, a reaction network and a model for prediction of sulfur com-pounds generated upon reaction of olefins in FCC gasoline with H2S were established.

  20. Production of Low-carbon Light Olefins from Catalytic Cracking of Crude Bio-oil

    Institute of Scientific and Technical Information of China (English)

    Yan-ni Yuan; Tie-jun Wang; Quan-xin Li

    2013-01-01

    Low-carbon light olefins are the basic feedstocks for the petrochemical industry.Catalytic cracking of crude bio-oil and its model compounds (including methanol,ethanol,acetic acid,acetone,and phenol) to light olefins were performed by using the La/HZSM-5 catalyst.The highest olefins yield from crude bio-oil reached 0.19 kg/(kg crude bio-oil).The reaction conditions including temperature,weight hourly space velocity,and addition of La into the HZSM-5 zeolite can be used to control both olefins yield and selectivity.Moderate adjusting the acidity with a suitable ratio between the strong acid and weak acid sites through adding La to the zeolite effectively enhanced the olefins selectivity and improved the catalyst stability.The production of light olefins from crude bio-oil is closely associated with the chemical composition and hydrogen to carbon effective ratios of feedstock.The comparison between the catalytic cracking and pyrolysis of bio-oil was studied.The mechanism of the bio-oil conversion to light olefins was also discussed.

  1. 长链烯烃的应用%The Application of Long Chain Olefins

    Institute of Scientific and Technical Information of China (English)

    姜秋实; 赵萌; 刘姝

    2013-01-01

    概述了长链烯烃的生产工艺,石蜡裂解和低碳烯烃齐聚.详述了长链烯烃的应用,可生产烯烃共聚体、润滑油、表面活性剂、油田化学品等.通过对它们需求量和生产能力数据进行分析,得出国内外对长链烯烃需求量日益增大,开发生产长链烯烃具有重要意义.%An overview of the production process of long chain olefins, paraffin cracking and low-carbon olefin oligomerization was given. The applications of long chain olefins were detailed, such as producing olefin copolymer, lubricants, surfactants and oil field chemicals, etc. Through the data analysis of demand for long chain olefins and production capacity, it was concluded that the demand for long chain olefins at home and abroad was increasing; the development and production of long chain olefins had a great significance.

  2. Fe-Catalyzed C–C Bond Construction from Olefins via Radicals

    Science.gov (United States)

    2017-01-01

    This Article details the development of the iron-catalyzed conversion of olefins to radicals and their subsequent use in the construction of C–C bonds. Optimization of a reductive diene cyclization led to the development of an intermolecular cross-coupling of electronically-differentiated donor and acceptor olefins. Although the substitution on the donor olefins was initially limited to alkyl and aryl groups, additional efforts culminated in the expansion of the scope of the substitution to various heteroatom-based functionalities, providing a unified olefin reactivity. A vinyl sulfone acceptor olefin was developed, which allowed for the efficient synthesis of sulfone adducts that could be used as branch points for further diversification. Moreover, this reactivity was extended into an olefin-based Minisci reaction to functionalize heterocyclic scaffolds. Finally, mechanistic studies resulted in a more thorough understanding of the reaction, giving rise to the development of a more efficient second-generation set of olefin cross-coupling conditions. PMID:28094980

  3. The asymmetric sandwich theorem

    CERN Document Server

    Simons, Stephen

    2011-01-01

    We discuss the asymmetric sandwich theorem, a generalization of the Hahn-Banach theorem. As applications, we derive various results on the existence of linear functionals that include bivariate, trivariate and quadrivariate generalizations of the Fenchel duality theorem. Most of the results are about affine functions defined on convex subsets of vector spaces, rather than linear functions defined on vector spaces. We consider both results that use a simple boundedness hypothesis (as in Rockafellar's version of the Fenchel duality theorem) and also results that use Baire's theorem (as in the Robinson-Attouch-Brezis version of the Fenchel duality theorem). This paper also contains some new results about metrizable topological vector spaces that are not necessarily locally convex.

  4. 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.

  5. Correlation Models for Light Olefin Yields from Catalytic Pyrolysis of Petroleum Residue

    Institute of Scientific and Technical Information of China (English)

    DongXiaoli; MengXianghai; GaoJinsen; XuChunming

    2005-01-01

    Correlation models for light olefin yields from residue catalytic pyrolysis are studied. Experiments are carried out in a confined fluidized bed reactor for Daqing (China) atmospheric residue catalytic pyrolysis over LCM-5 pyrolyzing catalyst. The influences of reaction temperature, residence time and the weight ratios of catalyst-to-oil and steam-to-oil on light olefin yields are researched. Correlation models for light olefin yields are established, and the model parameters obtained, with the least square method. Results for error analysis and the F-statistical test show that the correlation models have high calculation precision.

  6. Simple and highly Z-selective ruthenium-based olefin metathesis catalyst.

    Science.gov (United States)

    Occhipinti, Giovanni; Hansen, Fredrik R; Törnroos, Karl W; Jensen, Vidar R

    2013-03-01

    A one-step substitution of a single chloride anion of the Grubbs-Hoveyda second-generation catalyst with a 2,4,6-triphenylbenzenethiolate ligand resulted in an active olefin metathesis catalyst with remarkable Z selectivity, reaching 96% in metathesis homocoupling of terminal olefins. High turnover numbers (up to 2000 for homocoupling of 1-octene) were obtained along with sustained appreciable Z selectivity (>85%). Apart from the Z selectivity, many properties of the new catalyst, such as robustness toward oxygen and water as well as a tendency to isomerize substrates and react with internal olefin products, resemble those of the parent catalyst.

  7. Primary Alcohols from Terminal Olefins: Formal Anti-Markovnikov Hydration via Triple Relay Catalysis

    KAUST Repository

    Dong, G.

    2011-09-15

    Alcohol synthesis is critical to the chemical and pharmaceutical industries. The addition of water across olefins to form primary alcohols (anti-Markovnikov olefin hydration) would be a broadly useful reaction but has largely proven elusive; an indirect hydroboration/oxidation sequence requiring stoichiometric borane and oxidant is currently the most practical methodology. Here, we report a more direct approach with the use of a triple relay catalysis system that couples palladium-catalyzed oxidation, acid-catalyzed hydrolysis, and ruthenium-catalyzed reduction cycles. Aryl-substituted terminal olefins are converted to primary alcohols by net reaction with water in good yield and excellent regioselectivity.

  8. In vivo and in vitro olefin cyclopropanation catalyzed by heme enzymes

    Energy Technology Data Exchange (ETDEWEB)

    Coelho, Pedro S.; Brustad, Eric M.; Arnold, Frances H.; Wang, Zhan; Lewis, Jared C.

    2016-11-15

    The present invention provides methods for catalyzing the conversion of an olefin to any compound containing one or more cyclopropane functional groups using heme enzymes. In certain aspects, the present invention provides a method for producing a cyclopropanation product comprising providing an olefinic substrate, a diazo reagent, and a heme enzyme; and admixing the components in a reaction for a time sufficient to produce a cyclopropanation product. In other aspects, the present invention provides heme enzymes including variants and fragments thereof that are capable of carrying out in vivo and in vitro olefin cyclopropanation reactions. Expression vectors and host cells expressing the heme enzymes are also provided by the present invention.

  9. In vivo and in vitro olefin cyclopropanation catalyzed by heme enzymes

    Energy Technology Data Exchange (ETDEWEB)

    Coelho, Pedro S; Brustad, Eric M; Arnold, Frances H; Wang, Zhan; Lewis, Jared C

    2015-03-31

    The present invention provides methods for catalyzing the conversion of an olefin to any compound containing one or more cyclopropane functional groups using heme enzymes. In certain aspects, the present invention provides a method for producing a cyclopropanation product comprising providing an olefinic substrate, a diazo reagent, and a heme enzyme; and admixing the components in a reaction for a time sufficient to produce a cyclopropanation product. In other aspects, the present invention provides heme enzymes including variants and fragments thereof that are capable of carrying out in vivo and in vitro olefin cyclopropanation reactions. Expression vectors and host cells expressing the heme enzymes are also provided by the present invention.

  10. A new method for preparation of α-olefin olefin metathesis%烯烃歧化制备α-烯烃新方法研究

    Institute of Scientific and Technical Information of China (English)

    王如文; 郑来昌; 杨小辉; 杨克

    2012-01-01

    制备了一种负载型Re基催化剂Re2O7/γ-Al2O3,用于直链内烯烃与乙烯歧化制备α-烯烃.结果表明,以C11~C12直链内烯烃为原料,反应温度60 ℃,反应体积空速1 h-1,反应压力3 MPa的条件下,C11~C12烯烃的单程转化率达到90.0%,歧化选择性达到85.98%.%Preparation of supported Re based catalysts modified Re2O7/λ-Al2O3 ,used in the preparation of a-olefin metathesis of olefins with ethylene in the straight chain internal olefins process. The results showed that to C11,to C12,a straight chain internal olefin as raw material, the reaction temperature of 60 ℃ ,the reaction volume airspeed 1 h-1, C11~C12 ,olefin-way conversion rate of 90.0% under the conditions of the reaction pressure 3 MPa,metathesis selectivity 85.98%.

  11. Asymmetric Gepner Models (Revisited)

    CERN Document Server

    Gato-Rivera, B

    2010-01-01

    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 th...

  12. Enantioselective Rh-Catalyzed Hydroacylation of Olefins: From Serendipitous Discovery to Rational Design

    Science.gov (United States)

    Murphy, Stephen K.

    2015-01-01

    Rh-catalysed hydroacylation allows the construction of chiral ketones from olefins and aldehydes. Since James' and Young's serendipitous discovery of the enantioselective 4-pentenal cyclisation, both intra and intermolecular variants have emerged that enable broader applications. PMID:25277153

  13. MICROWAVE-EXPEDITED OLEFIN EPOXIDATION OVER HYDROTALCITES USING HYDROGEN PEROXIDE AND ACETONITRILE

    Science.gov (United States)

    An efficient microwave-assisted expoxidation of olefins is described over hydrotalcite catalysts in the presence of hydrogen peroxide and acetonitrile. This general and selective protocol is extremely fast and is applicable to a wide variety of subtrates.

  14. Polystyrene-supported Benzyl Selenide: An Efficient Reagent for Highly Stereocontrolled Synthesis of Substituted Olefins

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Polystyrene-supported benzyl selenide has been prepared. This novel reagent was treated with LDA to produce a selenium stabilized carbanion, which reacted with alkyl halide, followed by selenoxide syn-elimination, to give substituted olefins stereospecificly.

  15. COMMERCIAL TEST OF OLEFIN REDUCTION CATALYST AND NEW STANDARD GASOLINE PRODUCTION

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    To minimize air pollution, Beijing began to use new gasoline standard from July 1, 2000. To meet market need, the refinery of Beijing Yanshan Petrochemical Group Co. Ltd. performed the first commercial test of olefin reduction catalyst in 3# FCC unit. The test result shows that catalyst GOR-DQ can obviously reduce olefin content of FCC gasoline. With the test going on, olefin content in products decreased by 10%, little change in total liquid yield, but yield of gasoline and LCO slightly decreased, octane number, yields of LPG and coke increased. With FCC gesoline olefin reduction and the start up of CCR reforming unit, supply of qualified new standard gasoline has grown in this refinery.

  16. The preparation of trisubstituted alkenyl nucleoside phosphonates under ultrasound-assisted olefin cross-metathesis.

    Science.gov (United States)

    Sari, Ozkan; Hamada, Manabu; Roy, Vincent; Nolan, Steven P; Agrofoglio, Luigi A

    2013-09-01

    Intermolecular ultrasound-assisted olefin cross-metathesis is reported. This approach allows an easy access to challenging trisubstituted alkenyl nucleoside phosphonates. Regioselective chemoenzymatic deacetylation and Mitsunobu coupling are also described.

  17. Organo-Lewis acid as cocatalyst for cationic homogenous metallocene Ziegler-Natta olefin polymerizations

    Science.gov (United States)

    Marks, Tobin J.; Chen, You-Xian

    2000-01-01

    The synthesis of the organo-Lewis acid perfluorobiphenylborane (PBB) and the activation of metallocenes for the formation of a variety of highly active homogeneous Ziegler-Natta metallocene olefin polymerization, copolymerization and ring-opening polymerization catalysts is described.

  18. Olefin metathesis for effective polymer healing via dynamic exchange of strong carbon-carbon bonds

    Energy Technology Data Exchange (ETDEWEB)

    Guan, Zhibin; Lu, Yixuan

    2015-09-15

    A method of preparing a malleable and/or self-healing polymeric or composite material is provided. The method includes providing a polymeric or composite material comprising at least one alkene-containing polymer, combining the polymer with at least one homogeneous or heterogeneous transition metal olefin metathesis catalyst to form a polymeric or composite material, and performing an olefin metathesis reaction on the polymer so as to form reversible carbon-carbon double bonds in the polymer. Also provided is a method of healing a fractured surface of a polymeric material. The method includes bringing a fractured surface of a first polymeric material into contact with a second polymeric material, and performing an olefin metathesis reaction in the presence of a transition metal olefin metathesis catalyst such that the first polymeric material forms reversible carbon-carbon double bonds with the second polymeric material. Compositions comprising malleable and/or self-healing polymeric or composite material are also provided.

  19. Selective Metathesis of α-Olefins from Bio-Sourced Fischer–Tropsch Feeds

    KAUST Repository

    Rouen, Mathieu

    2016-10-14

    The search for a low-cost process for the valorization of linear alpha-olefins combining high productivity and high selectivity is a longstanding goal for chemists. Herein, we report a soluble ruthenium olefin metathesis catalyst that performs the conversion of linear alpha-olefins to longer internal linear olefins with high selectivity (>99%) under neat conditions at low loadings (50 ppm) and without the need of expensive additives. This robust catalytic process allowed us to efficiently and selectively re-equilibrate the naphtha fraction (C-5-C-8) of a Fischer-Tropsch feed derived from non petroleum resources to a higher-value product range (C-9-C-14), useful as detergent and plasticizer precursors.

  20. Kinetically controlled E-selective catalytic olefin metathesis.

    Science.gov (United States)

    Nguyen, Thach T; Koh, Ming Joo; Shen, Xiao; Romiti, Filippo; Schrock, Richard R; Hoveyda, Amir H

    2016-04-29

    A major shortcoming in olefin metathesis, a chemical process that is central to research in several branches of chemistry, is the lack of efficient methods that kinetically favor E isomers in the product distribution. Here we show that kinetically E-selective cross-metathesis reactions may be designed to generate thermodynamically disfavored alkenyl chlorides and fluorides in high yield and with exceptional stereoselectivity. With 1.0 to 5.0 mole % of a molybdenum-based catalyst, which may be delivered in the form of air- and moisture-stable paraffin pellets, reactions typically proceed to completion within 4 hours at ambient temperature. Many isomerically pure E-alkenyl chlorides, applicable to catalytic cross-coupling transformations and found in biologically active entities, thus become easily and directly accessible. Similarly, E-alkenyl fluorides can be synthesized from simpler compounds or more complex molecules.

  1. Nanoporous poly(lactide) by olefin metathesis degradation.

    Science.gov (United States)

    Bertrand, Arthur; Hillmyer, Marc A

    2013-07-31

    We describe an approach to ordered nanoporous poly(lactide) that relies on self-assembly of poly(butadiene)-poly(lactide) (PB-PLA) diblock copolymers followed by selective degradation of PB using olefin metathesis. The block copolymers were obtained by a combination of anionic and ring-opening transesterification polymerizations. The molar mass of each block was tailored to target materials with either a lamellar or cylindrical microphase-separated morphology. Orientation of these nanoscale domains was induced in thin films and monolithic samples through solvent annealing and mechanical deformation, respectively. Selective degradation of PB was achieved by immersing the samples in a solution of Grubbs first-generation catalyst in cyclohexane, a nonsolvent for PLA. Successful elimination of PB was confirmed by size-exclusion chromatography and (1)H NMR spectroscopy. Direct imaging of the resulting nanoporous PLA was obtained by scanning electron microscopy.

  2. Improved Ruthenium Catalysts for Z-Selective Olefin Metathesis

    Science.gov (United States)

    Keitz, Benjamin K.; Endo, Koji; Patel, Paresma R.; Herbert, Myles B.; Grubbs, Robert H.

    2011-01-01

    Several new C-H activated ruthenium catalysts for Z-selective olefin metathesis have been synthesized. Both the carboxylate ligand and the aryl group of the N-heterocyclic carbene have been altered and the resulting catalysts were evaluated using a range of metathesis reactions. Substitution of bidentate with monodentate X-type ligands led to a severe attenuation of metathesis activity and selectivity, while minor differences were observed between bidentate ligands within the same family (e.g. carboxylates). The use of nitrato-type ligands, in place of carboxylates, afforded a significant improvement in metathesis activity and selectivity. With these catalysts, turnover numbers approaching 1000 were possible for a variety of cross-metathesis reactions, including the synthesis of industrially-relevant products. PMID:22097946

  3. Catalytic Olefin Hydroamidation Enabled by Proton-Coupled Electron Transfer.

    Science.gov (United States)

    Miller, David C; Choi, Gilbert J; Orbe, Hudson S; Knowles, Robert R

    2015-10-28

    Here we report a ternary catalyst system for the intramolecular hydroamidation of unactivated olefins using simple N-aryl amide derivatives. Amide activation in these reactions occurs via concerted proton-coupled electron transfer (PCET) mediated by an excited state iridium complex and weak phosphate base to furnish a reactive amidyl radical that readily adds to pendant alkenes. A series of H-atom, electron, and proton transfer events with a thiophenol cocatalyst furnish the product and regenerate the active forms of the photocatalyst and base. Mechanistic studies indicate that the amide substrate can be selectively homolyzed via PCET in the presence of the thiophenol, despite a large difference in bond dissociation free energies between these functional groups.

  4. Separation of C6-Olefin Isomers in Reactive Extractants

    Institute of Scientific and Technical Information of China (English)

    SONG Fengxia; YU Yanmei; CHEN Jian

    2008-01-01

    Chemical complexation,in which certain metal ions (especially Ag+ and Cu+) reversibly and selectively complex olefin isomers,was used to separate 1-hexene from a mixture of intemal hexenes as an attractive alternative to traditional distillation.Several potential reactive extractants were investigated for their selectivity of both 1-hexene to 2-hexene and 1-hexene to 3-hexene.With 3 mol/L AgNO3-N-methyl-pyrrolidone (NMP) solution as extractant,the selectivity of 1-hexene to 3-hexane was increased to about 2.0 and the selectivity of 1-hexene to 2-hexene reached 1.5.Both the raffinate phase and the extracted phase were analyzed using a gas chromatograph equipped with a flame ionization detector and a 50-m capillary column.The experimental results show that the silver nitrate NMP solution has the better selectivity than other reactive extractions.

  5. Olefin Epoxidation in Aqueous Phase Using Ionic-Liquid Catalysts.

    Science.gov (United States)

    Cokoja, Mirza; Reich, Robert M; Wilhelm, Michael E; Kaposi, Marlene; Schäffer, Johannes; Morris, Danny S; Münchmeyer, Christian J; Anthofer, Michael H; Markovits, Iulius I E; Kühn, Fritz E; Herrmann, Wolfgang A; Jess, Andreas; Love, Jason B

    2016-07-21

    Hydrophobic imidazolium-based ionic liquids (IL) act as catalysts for the epoxidation of unfunctionalized olefins in water using hydrogen peroxide as oxidant. Although the catalysts are insoluble in both the substrate and in water, surprisingly, they are very well soluble in aqueous H2 O2 solution, owing to perrhenate-H2 O2 interactions. Even more remarkably, the presence of the catalyst also boosts the solubility of substrate in water. This effect is crucially dependent on the cation design. Hence, the imidazolium perrhenates enable both the transfer of hydrophobic substrate into the aqueous phase, and serve as actual catalysts, which is unprecedented. At the end of the reaction and in absence of H2 O2 the IL catalyst forms a third phase next to the lipophilic product and water and can easily be recycled.

  6. Catalyst for converting synthesis gas to light olefins

    Science.gov (United States)

    Rao, V. Udaya S.; Gormley, Robert J.

    1982-01-01

    A catalyst and process for making same useful in the catalytic hydrogenation of carbon monoxide in which a silicalite support substantially free of aluminum is soaked in an aqueous solution of iron and potassium salts wherein the iron and potassium are present in concentrations such that the dried silicalite has iron present in the range of from about 5 to about 25 percent by weight and has potassium present in an amount not less than about 0.2 percent by weight, and thereafter the silicalite is dried and combined with amorphous silica as a binder for pellets, the catalytic pellets are used to convert synthesis gas to C.sub.2 -C.sub.4 olefins.

  7. Molybdenum chloride catalysts for Z-selective olefin metathesis reactions

    Science.gov (United States)

    Koh, Ming Joo; Nguyen, Thach T.; Lam, Jonathan K.; Torker, Sebastian; Hyvl, Jakub; Schrock, Richard R.; Hoveyda, Amir H.

    2017-01-01

    The development of catalyst-controlled stereoselective olefin metathesis processes has been a pivotal recent advance in chemistry. The incorporation of appropriate ligands within complexes based on molybdenum, tungsten and ruthenium has led to reactivity and selectivity levels that were previously inaccessible. Here we show that molybdenum monoaryloxide chloride complexes furnish higher-energy (Z) isomers of trifluoromethyl-substituted alkenes through cross-metathesis reactions with the commercially available, inexpensive and typically inert Z-1,1,1,4,4,4-hexafluoro-2-butene. Furthermore, otherwise inefficient and non-stereoselective transformations with Z-1,2-dichloroethene and 1,2-dibromoethene can be effected with substantially improved efficiency and Z selectivity. The use of such molybdenum monoaryloxide chloride complexes enables the synthesis of representative biologically active molecules and trifluoromethyl analogues of medicinally relevant compounds. The origins of the activity and selectivity levels observed, which contradict previously proposed principles, are elucidated with the aid of density functional theory calculations.

  8. Capturing of the monoterpene olefin limonene produced in Saccharomyces cerevisiae.

    Science.gov (United States)

    Jongedijk, Esmer; Cankar, Katarina; Ranzijn, Jorn; van der Krol, Sander; Bouwmeester, Harro; Beekwilder, Jules

    2015-01-01

    Monoterpene olefins such as limonene are plant compounds with applications as flavouring and fragrance agents, as solvents and potentially also in polymer and fuel chemistry. We engineered baker's yeast Saccharomyces cerevisiae to express a (-)-limonene synthase from Perilla frutescens and a (+)-limonene synthase from Citrus limon. Both proteins were expressed either with their native plastid targeting signal or in a truncated form in which the plastidial sorting signal was removed. The yeast host strain for expression was AE9 K197G, which expresses a mutant Erg20 enzyme. This enzyme catalyses the formation of geranyl diphosphate, which is the precursor for monoterpenes. Several methods were tested to capture limonene produced by the yeast. Extraction from the culture medium by pentane, or by the addition of CaCl2 followed by solid-phase micro-extraction, did not lead to detectable limonene, indicating that limonene is rapidly lost from the culture medium. Volatile terpenes such as limonene may also be trapped in a dodecane phase added to the medium during fermentation. This method resulted in recovery of 0.028 mg/l (+)-limonene and 0.060 mg/l (-)-limonene in strains using the truncated Citrus and Perilla synthases, respectively. Trapping the headspace during culture of the limonene synthase-expressing strains resulted in higher titres, at 0.12 mg/l (+)-limonene and 0.49 mg/l (-)-limonene. These results show that the volatile properties of the olefins produced require specific methods for efficient recovery of these molecules from biotechnological production systems.

  9. 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....

  10. An Improved Protocol for the Aldehyde Olefination Reaction Using (bmim ( as Reaction Medium

    Directory of Open Access Journals (Sweden)

    Vivek Srivastava

    2013-01-01

    Full Text Available [Ru(CODCl2]/CuCl2·2H2O/LiCl catalytic system works efficiently in ionic liquid media for aldehyde olefination reaction. It offers good yield and selectivity with the added advantage of 5 times recyclability for [Ru(CODCl2] /CuCl2·2H2O/LiCl catalytic system. We also successfully reduced the reaction time from 12 hours to 9 hours for the aldehyde olefination reaction.

  11. Macrocyclic olefin metathesis at high concentrations by using a phase-separation strategy.

    Science.gov (United States)

    Raymond, Michaël; Holtz-Mulholland, Michael; Collins, Shawn K

    2014-09-26

    Macrocyclic olefin metathesis has seen advances in the areas of stereochemistry, chemoselectivity, and catalyst stability, but strategies aimed at controlling dilution effects in macrocyclizations are rare. Herein, a protocol to promote macrocyclic olefin metathesis, one of the most common synthetic tools used to prepare macrocycles, at relatively high concentrations (up to 60 mM) is described by exploitation of a phase-separation strategy. A variety of macrocyclic skeletons could be prepared having either different alkyl, aryl, or amino acids spacers.

  12. Ruthenium-Catalyzed Olefin Cross-Metathesis with Tetrafluoroethylene and Analogous Fluoroolefins.

    Science.gov (United States)

    Takahira, Yusuke; Morizawa, Yoshitomi

    2015-06-10

    This Communication describes a successful olefin cross-metathesis with tetrafluoroethylene and its analogues. A key to the efficient catalytic cycle is interconversion between two thermodynamically stable, generally considered sluggish, Fischer carbenes. This newly demonstrated catalytic transformation enables easy and short-step synthesis of a new class of partially fluorinated olefins bearing plural fluorine atoms, which are particularly important and valuable compounds in organic synthesis and medicinal chemistry as well as the materials and polymer industries.

  13. Catalytic Enantioselective Allylic Amination of Olefins for the Synthesis of ent-Sitagliptin.

    Science.gov (United States)

    Bao, Hongli; Bayeh, Liela; Tambar, Uttam K

    2013-11-01

    The presence of nitrogen atoms in most chiral pharmaceutical drugs has motivated the development of numerous strategies for the synthesis of enantioenriched amines. Current methods are based on the multi-step transformation of pre-functionalized allylic electrophiles into chiral allylic amines. The enantioselective allylic amination of unactivated olefins represents a more direct and attractive strategy. We report the enantioselective synthesis of ent-sitagliptin via an allylic amination of an unactivated terminal olefin.

  14. Pd(II/HPMoV-Catalyzed Direct Oxidative Coupling Reaction of Benzenes with Olefins

    Directory of Open Access Journals (Sweden)

    Yasutaka Ishii

    2010-03-01

    Full Text Available The direct aerobic coupling reaction of arenes with olefins was successfully achieved by the use of Pd(OAc2/molybdovanadophosphoric acid (HPMoV as a key catalyst under 1 atm of dioxygen. This catalytic system could be extended to the coupling reaction of various substituted benzenes with olefins such as acrylates, aclrolein, and ethylene through the direct aromatic C-H bond activation.

  15. 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

  16. On Asymmetric Quantum MDS Codes

    CERN Document Server

    Ezerman, Martianus Frederic; Ling, San

    2010-01-01

    Assuming the validity of the MDS Conjecture, the weight distribution of all MDS codes is known. Using a recently-established characterization of asymmetric quantum error-correcting codes, linear MDS codes can be used to construct asymmetric quantum MDS codes with $d_{z} \\geq d_{x}\\geq 2$ for all possible values of length $n$ for which linear MDS codes over $\\F_{q}$ are known to exist.

  17. Asymmetric cation-binding catalysis

    DEFF Research Database (Denmark)

    Oliveira, Maria Teresa; Lee, Jiwoong

    2017-01-01

    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...... 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...

  18. 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.

  19. Rh(I)–Bisphosphine-Catalyzed Asymmetric, Intermolecular Hydroheteroarylation of α-Substituted Acrylate Derivatives

    Science.gov (United States)

    2015-01-01

    Asymmetric hydroheteroarylation of alkenes represents a convenient entry to elaborated heterocyclic motifs. While chiral acids are known to mediate asymmetric addition of electron-rich heteroarenes to Michael acceptors, very few methods exploit transition metals to catalyze alkylation of heterocycles with olefins via a C–H activation, migratory insertion sequence. Herein, we describe the development of an asymmetric, intermolecular hydroheteroarylation reaction of α-substituted acrylates with benzoxazoles. The reaction provides 2-substitued benzoxazoles in moderate to excellent yields and good to excellent enantioselectivities. Notably, a series of mechanistic studies appears to contradict a pathway involving enantioselective protonation of a Rh(I)–enolate, despite the fact that such a mechanism is invoked almost unanimously in the related addition of aryl boronic acids to methacrylate derivatives. Evidence suggests instead that migratory insertion or beta-hydride elimination is enantiodetermining and that isomerization of a Rh(I)–enolate to a Rh(I)–heterobenzyl species insulates the resultant α-stereocenter from epimerization. A bulky ligand, CTH-(R)-Xylyl-P-Phos, is crucial for reactivity and enantioselectivity, as it likely discourages undesired ligation of benzoxazole substrates or intermediates to on- or off-cycle rhodium complexes and attenuates coordination-promoted product epimerization. PMID:25545834

  20. Supported ruthenium-carbene catalyst on ionic magnetic nanoparticles for olefin metathesis.

    Science.gov (United States)

    Chen, Shu-Wei; Zhang, Zhi-Cheng; Ma, Miaofeng; Zhong, Chong-Min; Lee, Sang-gi

    2014-10-01

    The Grubbs-Hoveyda ruthenium-carbene complex has been covalently immobilized on ionic magnetic nanoparticles utilizing an imidazolium salt linker. The supported catalyst exhibited excellent catalytic activity for ring-closing metathesis (RCM) and cross-metathesis (CM) in the presence of less than 1 mol % of ruthenium. The catalysts can easily be recovered magnetically and reused up to seven times with minimal leaching of ruthenium species.

  1. Isomerizing olefin metathesis as a strategy to access defined distributions of unsaturated compounds from fatty acids.

    Science.gov (United States)

    Ohlmann, Dominik M; Tschauder, Nicole; Stockis, Jean-Pierre; Goossen, Käthe; Dierker, Markus; Goossen, Lukas J

    2012-08-22

    The dimeric palladium(I) complex [Pd(μ-Br)(t)Bu(3)P](2) was found to possess unique activity for the catalytic double-bond migration within unsaturated compounds. This isomerization catalyst is fully compatible with state-of-the-art olefin metathesis catalysts. In the presence of bifunctional catalyst systems consisting of [Pd(μ-Br)(t)Bu(3)P](2) and NHC-indylidene ruthenium complexes, unsaturated compounds are continuously converted into equilibrium mixtures of double-bond isomers, which concurrently undergo catalytic olefin metathesis. Using such highly active catalyst systems, the isomerizing olefin metathesis becomes an efficient way to access defined distributions of unsaturated compounds from olefinic substrates. Computational models were designed to predict the outcome of such reactions. The synthetic utility of isomerizing metatheses is demonstrated by various new applications. Thus, the isomerizing self-metathesis of oleic and other fatty acids and esters provides olefins along with unsaturated mono- and dicarboxylates in distributions with adjustable widths. The cross-metathesis of two olefins with different chain lengths leads to regular distributions with a mean chain length that depends on the chain length of both starting materials and their ratio. The cross-metathesis of oleic acid with ethylene serves to access olefin blends with mean chain lengths below 18 carbons, while its analogous reaction with hex-3-enedioic acid gives unsaturated dicarboxylic acids with adjustable mean chain lengths as major products. Overall, the concept of isomerizing metatheses promises to open up new synthetic opportunities for the incorporation of oleochemicals as renewable feedstocks into the chemical value chain.

  2. Cobalt carbide nanoprisms for direct production of lower olefins from syngas.

    Science.gov (United States)

    Zhong, Liangshu; Yu, Fei; An, Yunlei; Zhao, Yonghui; Sun, Yuhan; Li, Zhengjia; Lin, Tiejun; Lin, Yanjun; Qi, Xingzhen; Dai, Yuanyuan; Gu, Lin; Hu, Jinsong; Jin, Shifeng; Shen, Qun; Wang, Hui

    2016-10-06

    Lower olefins-generally referring to ethylene, propylene and butylene-are basic carbon-based building blocks that are widely used in the chemical industry, and are traditionally produced through thermal or catalytic cracking of a range of hydrocarbon feedstocks, such as naphtha, gas oil, condensates and light alkanes. With the rapid depletion of the limited petroleum reserves that serve as the source of these hydrocarbons, there is an urgent need for processes that can produce lower olefins from alternative feedstocks. The 'Fischer-Tropsch to olefins' (FTO) process has long offered a way of producing lower olefins directly from syngas-a mixture of hydrogen and carbon monoxide that is readily derived from coal, biomass and natural gas. But the hydrocarbons obtained with the FTO process typically follow the so-called Anderson-Schulz-Flory distribution, which is characterized by a maximum C2-C4 hydrocarbon fraction of about 56.7 per cent and an undesired methane fraction of about 29.2 per cent (refs 1, 10, 11, 12). Here we show that, under mild reaction conditions, cobalt carbide quadrangular nanoprisms catalyse the FTO conversion of syngas with high selectivity for the production of lower olefins (constituting around 60.8 per cent of the carbon products), while generating little methane (about 5.0 per cent), with the ratio of desired unsaturated hydrocarbons to less valuable saturated hydrocarbons amongst the C2-C4 products being as high as 30. Detailed catalyst characterization during the initial reaction stage and theoretical calculations indicate that preferentially exposed {101} and {020} facets play a pivotal role during syngas conversion, in that they favour olefin production and inhibit methane formation, and thereby render cobalt carbide nanoprisms a promising new catalyst system for directly converting syngas into lower olefins.

  3. Nonlinear effects in asymmetric catalysis.

    Science.gov (United States)

    Satyanarayana, Tummanapalli; Abraham, Susan; Kagan, Henri B

    2009-01-01

    There is a need for the preparation of enantiomerically pure compounds for various applications. An efficient approach to achieve this goal is asymmetric catalysis. The chiral catalyst is usually prepared from a chiral auxiliary, which itself is derived from a natural product or by resolution of a racemic precursor. The use of non-enantiopure chiral auxiliaries in asymmetric catalysis seems unattractive to preparative chemists, since the anticipated enantiomeric excess (ee) of the reaction product should be proportional to the ee value of the chiral auxiliary (linearity). In fact, some deviation from linearity may arise. Such nonlinear effects can be rich in mechanistic information and can be synthetically useful (asymmetric amplification). This Review documents the advances made during the last decade in the use of nonlinear effects in the area of organometallic and organic catalysis.

  4. 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.

  5. Proceedings of the DGMK-Conference 'Creating value from light olefins - production and conversion'. Authors' manuscripts

    Energy Technology Data Exchange (ETDEWEB)

    Emig, G.; Kraemer, H.J.; Weitkamp, J. (eds.)

    2001-07-01

    Main topics of the conference were: production of light olefin by steamcracking and catalytic cracking processes, catalysts, methanol to olefin processes, oxidative dehydrogenation, partial oxidation, selective oxidation of alkanes with various catalysts. (uke)

  6. 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......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...

  7. Engineering a dirhodium artificial metalloenzyme for selective olefin cyclopropanation.

    Science.gov (United States)

    Srivastava, Poonam; Yang, Hao; Ellis-Guardiola, Ken; Lewis, Jared C

    2015-07-24

    Artificial metalloenzymes (ArMs) formed by incorporating synthetic metal catalysts into protein scaffolds have the potential to impart to chemical reactions selectivity that would be difficult to achieve using metal catalysts alone. In this work, we covalently link an alkyne-substituted dirhodium catalyst to a prolyl oligopeptidase containing a genetically encoded L-4-azidophenylalanine residue to create an ArM that catalyses olefin cyclopropanation. Scaffold mutagenesis is then used to improve the enantioselectivity of this reaction, and cyclopropanation of a range of styrenes and donor-acceptor carbene precursors were accepted. The ArM reduces the formation of byproducts, including those resulting from the reaction of dirhodium-carbene intermediates with water. This shows that an ArM can improve the substrate specificity of a catalyst and, for the first time, the water tolerance of a metal-catalysed reaction. Given the diversity of reactions catalysed by dirhodium complexes, we anticipate that dirhodium ArMs will provide many unique opportunities for selective catalysis.

  8. Low severity coal liquefaction promoted by cyclic olefins. Quarterly report, October--December 1992

    Energy Technology Data Exchange (ETDEWEB)

    Curtis, C.W.

    1992-12-31

    Low severity coal liquefaction promoted by cyclic olefins offers a means of liquefying coal at low severity conditions. Lower temperature, 350{degrees}C, and lower hydrogen pressure, 500 psi, have been used to perform liquefaction reactions. The presence of the cyclic olefin, hexahydroanthracene, made a substantial difference in the conversion of Illinois No. 6 coal at these low severity conditions. The Researchperformed this quarter was a parametric evaluation of the effect of different parameters on the coal conversion and product distribution from coal. The effect of the parameters on product distribution from hexahydroanthracene was also determined. The work planned for next quarter includes combining the most effective parametric conditions for the low severity reactions and determining their effect. The second part ofthe research performed this quarter involved performing Fourier transform infrared (FTIR) spectroscopy using cyclic olefins. The objective of this study was to determine the feasibility of using FTIR and a heated cell to determine the reaction pathway that occurs in the hydrogen donation reactions from cyclic olefins. The progress made to date includes evaluating the FTIR spectra of cyclic olefins and their expected reaction products. This work is included in this progress report.

  9. Effect of C6-olefin isomers on π-complexation for purification of 1-hexene by reactive extractive distillation

    NARCIS (Netherlands)

    Wentink, A.E.; Kockmann, D.; Kuipers, N.J.M.; Haan, de A.B.; Scholz, J.; Mulder, H.

    2002-01-01

    Separation of α-olefins from other olefin isomers is a difficult and expensive operation because of the low selectivities encountered. A promising alternative is π-complexation in combination with extractive distillation: reactive extractive distillation (RED). In this paper, silver nitrate dissolve

  10. Straightforward synthesis of alpha,beta-unsaturated thioesters via ruthenium-catalyzed olefin cross-metathesis with thioacrylate

    NARCIS (Netherlands)

    van Zijl, Anthoni W.; Minnaard, Adriaan J.; Feringa, Ben L.

    2008-01-01

    The cross-metathesis reaction of S-ethyl thioacrylate with a variety of olefins is effectively catalyzed by using a ruthenium benzylidene olefin metathesis catalyst. This reaction provides a convenient and versatile route to substituted alpha,beta-unsaturated thioesters, key building blocks in organ

  11. Single-catalyst particle spectroscopy of alcohol-to-olefins conversions : Comparison between SAPO-34 and SSZ-13

    NARCIS (Netherlands)

    Qian, Qingyun; Ruiz-Martinez, Javier; Mokhtar, Mohamed; Asiri, Abdullah M.; Al-Thabaiti, Shaeel A.; Basahel, Suliman N.; Weckhuysen, Bert M.

    2014-01-01

    The formation of distinct hydrocarbon pool (HCP) species on individual micron-sized SAPO-34 and SSZ-13 crystals have been compared during methanol-to-olefins (MTO) and ethanol-to-olefins (ETO) conversion processes. In situ UV-vis micro-spectroscopy reveals the formation of 400 nm and 580 nm absorpti

  12. 78 FR 49749 - Williams Olefins Feedstock Pipelines, L.L.C.; Notice of Petition for Declaratory Order

    Science.gov (United States)

    2013-08-15

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF ENERGY Federal Energy Regulatory Commission Williams Olefins Feedstock Pipelines, L.L.C.; Notice of Petition for... Practices and Procedure, 18 CFR 385.207(a)(2)(2012), Williams Olefins Feedstock Pipelines, L.L.C., filed...

  13. Synthesis of Asymmetric Propanetriol Analogues

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    From natural tartaric acid, (R)-2-benzyloxy-3-(2-tetrahydropyranyloxy) propanol 3 was designed and synthesized, and (R)-2-benzyloxy-3-(4-methoxybenzyloxy) propanol 7 was prepared in a new method. They can be used as chiral synthons of lysophosphatidic acid and other compounds with asymmetric propanetriol backbone.

  14. Catalytic Asymmetric Bromocyclization of Polyenes.

    Science.gov (United States)

    Samanta, Ramesh C; Yamamoto, Hisashi

    2017-02-01

    The first catalytic asymmetric bromonium ion-induced polyene cyclization has been achieved by using a chiral BINOL-derived thiophosphoramide catalyst and 1,3-dibromo-5,5-dimethylhydantoin as an electrophilic bromine source. Bromocyclization products are obtained in high yields, with good enantiomeric ratios and high diastereoselectivity, and are abundantly found as scaffolds in natural products.

  15. At the frontier between heterogeneous and homogeneous catalysis: hydrogenation of olefins and alkynes with soluble iron nanoparticles.

    Science.gov (United States)

    Rangheard, Claudine; de Julián Fernández, César; Phua, Pim-Huat; Hoorn, Johan; Lefort, Laurent; de Vries, Johannes G

    2010-09-28

    The use of non-supported Fe nanoparticles in the hydrogenation of unsaturated C-C bonds is a green catalytic concept at the frontier between homogeneous and heterogeneous catalysis. Iron nanoparticles can be obtained by reducing Fe salts with strong reductants in various solvents. FeCl(3) reduced by 3 equivalents of EtMgCl forms an active catalyst for the hydrogenation of a range of olefins and alkynes. Olefin hydrogenation is relatively fast at 5 bar using 5 mol% of catalyst. The catalyst is also active for terminal olefins and 1,1' and 1,2-cis disubstituted olefins while trans-olefins react much slower. 1-Octyne is hydrogenated to mixtures of 1-octene and octane. Kinetic studies led us to propose a mechanism for this latter transformation where octane is obtained by two different pathways. Characterization of the nanoparticles via TEM, magnetic measurements and poisoning experiments were undertaken to understand the true nature of our catalyst.

  16. Diversity-oriented approach to macrocyclic cyclophane derivatives by Suzuki-Miyaura cross-coupling and olefin metathesis as key steps.

    Science.gov (United States)

    Kotha, Sambasivarao; Chavan, Arjun S; Shaikh, Mobin

    2012-01-01

    Palladium-catalyzed Suzuki-Miyaura (SM) cross-coupling reaction with allylboronic acid pinacol ester and titanium assisted cross-metathesis (CM)/ring-closing metathesis (RCM) cascade has been used to synthesize macrocyclic cyclophane derivatives.

  17. Application of Olefin-Reducing Catalyst in FCC Unit at Daqing Petrochemical Company

    Institute of Scientific and Technical Information of China (English)

    Liu Xinfeng; Yang Daoxue; Zhang Guojing; Yao Hua

    2003-01-01

    This article refers to the application of DOCO olefin-reducing catalyst developed by RIPP and manufactured by the Catalyst Factory of Changling Refining and Chemical Company in the 1.4 Mt/a RFCCU at Daqing Petrochemical Company. Results of operation over two months had revealed that this catalyst had good olefin-reducing ability and heavy oil converting ability adapted to paraffinic feedstock. The gasoline olefin yield had been reduced to 36.1 v% from 54.2 v% with gasoline RON rating decreased by 1.4 units. The induction period of gasoline had significantly increased to 952 mm, while the coke yield was increased by 0.05 percentage point with light oil yield dropping by only 0.02 percentage point. The FCC product distribution is favorable.

  18. Study on Removing Trace Olefins in Aromatic Hydrocarbons with HPMo-loaded Y Zeolites

    Institute of Scientific and Technical Information of China (English)

    Jiang Zhenghong; Zeng Haiping; Shi Li

    2008-01-01

    HPMo-loaded Y-zeolites were prepared for the removal of trace olefins from aromatic hydrocarbons.The temperature of calcination and the proportion of phospho-molybdic acid in the catalyst were studied. The catalytic activity for olefins removal and the service life of the catalyst were tested in a fixed bed microreactor. The results showed that the catalyst containing 3% phospho-molybdic acid, which was calcined at 550℃,demonstrated the best activity for olefins removal. The catalyst could be regenerated and could perform still very well. Catalyst characterization was performed by XRD and measured by pyridine-FTIR spectrometry. The test results indicated that the activity of the catalyst was related with the effect of acid concentration and acid strength. Besides, the deactivation of the catalyst was associated with the formation of coke deposits and the deactivated catalyst could recover its activity by oxidation with air under a proper temperature.

  19. Divergent dendrimer synthesis via the Passerini three-component reaction and olefin cross-metathesis.

    Science.gov (United States)

    Kreye, Oliver; Kugele, Dennis; Faust, Lorenz; Meier, Michael A R

    2014-02-01

    The combination of the Passerini reaction and olefin cross-metathesis is shown to be a very useful approach for the divergent synthesis of dendrimers. Castor oil-derived platform chemicals, such as 10-undecenoic acid and 10-undecenal, are reacted in a Passerini reaction with an unsaturated isocyanide to obtain a core unit having three terminal double bonds. Subsequent olefin cross-metathesis with tert-butyl acrylate, followed by hydrogenation of the double bonds and hydrolysis of the tert-butyl ester, leads to an active core unit bearing three carboxylic acid groups as reactive sites. Iterative steps of the Passerini reaction with 10-undecenal and 10-isocyanodec-1-ene for branching, and olefin cross-metathesis with tert-butyl acrylate, followed by hydrogenation and hydrolysis allow the synthesis of a third-generation dendrimer. All steps of the synthesis are carefully characterized by NMR, GPC, MS, and IR.

  20. A comprehensive study of olefin metathesis catalyzed by Ru-based catalysts.

    Science.gov (United States)

    Poater, Albert; Cavallo, Luigi

    2015-01-01

    During a Ru-catalyzed reaction of an olefin with an alkylidene moiety that leads to a metallacycle intermediate, the cis insertion of the olefin can occur from two different directions, namely side and bottom with respect to the phosphine or N-heterocyclic ligand (NHC), depending on the first or second generation Grubbs catalyst. Here, DFT calculations unravel to which extent the bottom coordination of olefins with respect is favored over the side coordination through screening a wide range of catalysts, including first and second generation Grubbs catalysts as well as the subsequent Hoveyda derivatives. The equilibrium between bottom and side coordination is influenced by sterics, electronics, and polarity of the solvent. The side attack is favored for sterically less demanding NHC and/or alkylidene ligands. Moreover the generation of a 14-electron species is also discussed, with either pyridine or phosphine ligands to dissociate.

  1. A comprehensive study of olefin metathesis catalyzed by Ru-based catalysts

    Science.gov (United States)

    2015-01-01

    Summary During a Ru-catalyzed reaction of an olefin with an alkylidene moiety that leads to a metallacycle intermediate, the cis insertion of the olefin can occur from two different directions, namely side and bottom with respect to the phosphine or N-heterocyclic ligand (NHC), depending on the first or second generation Grubbs catalyst. Here, DFT calculations unravel to which extent the bottom coordination of olefins with respect is favored over the side coordination through screening a wide range of catalysts, including first and second generation Grubbs catalysts as well as the subsequent Hoveyda derivatives. The equilibrium between bottom and side coordination is influenced by sterics, electronics, and polarity of the solvent. The side attack is favored for sterically less demanding NHC and/or alkylidene ligands. Moreover the generation of a 14-electron species is also discussed, with either pyridine or phosphine ligands to dissociate. PMID:26664596

  2. Kinetic Selectivity of Olefin Metathesis Catalysts Bearing Cyclic (Alkyl)(Amino)Carbenes

    Science.gov (United States)

    Anderson, Donde R.; Ung, Thay; Mkrtumyan, Garik; Bertrand, Guy; Grubbs, Robert H.; Schrodi, Yann

    2008-01-01

    The evaluation of ruthenium olefin metathesis catalysts 4–6 bearing cyclic (alkyl)(amino)carbenes (CAACs) in the cross-metathesis of cis-1,4-diacetoxy-2-butene (7) with allylbenzene (8) and the ethenolysis of methyl oleate (11) is reported. Relative to most NHC-substituted complexes, CAAC-substituted catalysts exhibit lower E/Z ratios (3:1 at 70% conversion) in the cross-metathesis of 7 and 8. Additionally, complexes 4–6 demonstrate good selectivity for the formation of terminal olefins versus internal olefins in the ethenolysis of 11. Indeed, complex 6 achieved 35 000 TONs, the highest recorded to date. CAAC-substituted complexes exhibit markedly different kinetic selectivity than most NHC-substituted complexes. PMID:18584055

  3. A comprehensive study of olefin metathesis catalyzed by Ru-based catalysts

    KAUST Repository

    Poater, Albert

    2015-09-29

    During a Ru-catalyzed reaction of an olefin with an alkylidene moiety that leads to a metallacycle intermediate, the cis insertion of the olefin can occur from two different directions, namely side and bottom with respect to the phosphine or N-heterocyclic ligand (NHC), depending on the first or second generation Grubbs catalyst. Here, DFT calculations unravel to which extent the bottom coordination of olefins with respect is favored over the side coordination through screening a wide range of catalysts, including first and second generation Grubbs catalysts as well as the subsequent Hoveyda derivatives. The equilibrium between bottom and side coordination is influenced by sterics, electronics, and polarity of the solvent. The side attack is favored for sterically less demanding NHC and/or alkylidene ligands. Moreover the generation of a 14-electron species is also discussed, with either pyridine or phosphine ligands to dissociate.

  4. A comprehensive study of olefin metathesis catalyzed by Ru-based catalysts

    Directory of Open Access Journals (Sweden)

    Albert Poater

    2015-09-01

    Full Text Available During a Ru-catalyzed reaction of an olefin with an alkylidene moiety that leads to a metallacycle intermediate, the cis insertion of the olefin can occur from two different directions, namely side and bottom with respect to the phosphine or N-heterocyclic ligand (NHC, depending on the first or second generation Grubbs catalyst. Here, DFT calculations unravel to which extent the bottom coordination of olefins with respect is favored over the side coordination through screening a wide range of catalysts, including first and second generation Grubbs catalysts as well as the subsequent Hoveyda derivatives. The equilibrium between bottom and side coordination is influenced by sterics, electronics, and polarity of the solvent. The side attack is favored for sterically less demanding NHC and/or alkylidene ligands. Moreover the generation of a 14-electron species is also discussed, with either pyridine or phosphine ligands to dissociate.

  5. First examples of intramolecular addition of primary amidyl radicals to olefins

    Energy Technology Data Exchange (ETDEWEB)

    Gaudreault, P.; Drouin, C.; Lessard, J. [Sherbrooke Univ., PQ (Canada). Dept. de Chimie

    2005-07-01

    This paper presents the first examples of radical cyclization involving a primary amidyl radical and a pendant olefin. Amidyl radicals have attracted interest in terms of their structure, reactivity, and ways to generate them. The intramolecular addition of an amidyl radical on a pendant olefin appears to be a powerful synthetic tool for creating nitrogen-containing heterocycles. Although several examples of cyclization involving secondary amidyl radicals are cited in the the literature, there are no examples of a successful cyclization involving a primary amidyl radical. This is because all attempts to prepare the usual radical precursors have failed when applied to olefinic primary amides. This study reveals that N-(phenylthio) derivatives of olefinic primary amides can be easily prepared and that nitrogen heterocycles resulting from their radical cyclization can be obtained in good to very good yields. Four olefinic primary amides were chosen as models for radical cyclization of primary amidyl radicals. They were prepared from the corresponding carboxylic acids via the acid chlorides. Conversion of primary amides into suitable amidyl radical precursors was also examined. The study showed that N-(phenylthio) amides could be easily prepared by following a slightly modified protocol developed by Esker and Newcomb, by reacting the anion of the amide with phenylsulfenyl chloride. In particular, olefinic N-(phenylthio) amides were prepared and used as primary amidyl radical precursors in a reaction with a solution of 2,2'-azobis(isobutyronitrile) in catalytic quantities and tributyltin hydride in benzene. The resulting yields of cyclic products ranged from 63 to 85 per cent. The intent of the study was to demonstrate that it is no longer necessary to prepare an N-protected precursor and then remove the protecting group after cyclization. Further studies are currently underway. 10 refs., 1 tab.

  6. The progress of SINOPEC methanol-to-olefins (S-MTO) technology

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Hongxing; Xie, Zaiku; Zhao, Guoliang [SINOPEC Shanghai Research Institute of Petrochemical Technology (China)

    2013-11-01

    It is widely recognized that naphtha steam crackers and FCC units are the main current sources of ethylene and propylene. On the condition of high oil price, olefin producers are striving to develop new economical routes to produce ethylene and propylene with low-cost feedstocks. Methanol to olefins (MTO) has aroused great attention in recent years, and SINOPEC has developed a new kind of MTO process named S-MTO which features high olefins selectivity, high methanol conversion and low catalyst consumption. Puyang Zhongyuan 200 KTA S-MTO has been in steady operation for more than 17 months. The catalyst used in the process is based on a silicoaluminophosphate, SAPO-34, which has very high carbon selectivity to low carbon olefins. Results from the commercial plant show that S-MTO process converts methanol to ethylene and propylene at about 81% carbon selectivity. The carbon selectivity approaches 92% if butenes are also accounted for as part of the product. Typically, the ratio of propylene to ethylene can range from 0.6 to 1.3. When combined with OCC (Olefin Catalytic Cracking) process to convert the heavier olefins, the overall yield of ethylene and propylene can increase to 85% {proportional_to} 87% and propylene-ethylene ratios of more than 1.5 are achievable. Other co-products include very small amounts of C1-C4 paraffins, hydrogen, CO and CO{sub 2}, as well as heavier oxygenates only with ppm level. Because of the quick deactivation of MTO catalyst, a kind of high efficiency fast fluidized bed reactor is adopted. The activity of deactivated catalyst is recovered by burning the coke in the regenerator. This paper gives an updated introduction of S-MTO technology developed by SINOPEC SRIPT. (orig.)

  7. Template-directed synthesis of flexible porphyrin nanocage and nanorings via one-step olefin metathesis.

    Science.gov (United States)

    Zhu, Bin; Chen, Huanxin; Lin, Wei; Ye, Yang; Wu, Jing; Li, Shijun

    2014-10-29

    We describe the fabrication of a suite of flexible porphyrin cages and nanorings from a simple tetraalkene-derived zinc porphyrin monomer via a highly efficient template-directed strategy. The zinc porphyrin monomers were preorganized together by coordination with N atoms of multidentate ligands. Subsequent one-step olefin metathesis furnished a bisporphyrin cage, a triporphyrin nanoring, and a hexaporphyrin nanoring. In the case of the hexaporphyrin nanoring, 24 terminal olefins from six porphyrin monomers reacted with each other to form 12 new double bonds, delivering the final product. The triporphyrin and hexaporphyrin nanorings were further employed as hosts to encapsulate C60 and C70.

  8. A Light-Activated Olefin Metathesis Catalyst Equipped with a Chromatic Orthogonal Self-Destruct Function.

    Science.gov (United States)

    Sutar, Revannath L; Levin, Efrat; Butilkov, Danielle; Goldberg, Israel; Reany, Ofer; Lemcoff, N Gabriel

    2016-01-11

    A sulfur-chelated photolatent ruthenium olefin metathesis catalyst has been equipped with supersilyl protecting groups on the N-heterocyclic carbene ligand. The silyl groups function as an irreversible chromatic kill switch, thus decomposing the catalyst when it is irradiated with 254 nm UV light. Therefore, different types of olefin metathesis reactions may be started by irradiation with 350 nm UV light and prevented by irradiation with shorter wavelengths. The possibility to induce and impede catalysis just by using light of different frequencies opens the pathway for stereolithographic applications and novel light-guided chemical sequences.

  9. Desymmetrization of 7-azabicycloalkenes by tandem olefin metathesis for the preparation of natural product scaffolds

    Directory of Open Access Journals (Sweden)

    Deppermann Nina

    2007-12-01

    Full Text Available Abstract Background Tandem olefin metathesis sequences are known to be versatile for the generation of natural product scaffolds and have also been used for ring opening of strained carbo- and heterocycles. In this paper we demonstrate the potential of these reactions for the desymmetrization of 7-azabicycloalkenes. Results We have established efficient protocols for the desymmetrization of different 7-azabicycloalkenes by intra- and intermolecular tandem metathesis sequences with ruthenium based catalysts. Conclusion Desymmetrization of 7-azabicycloalkenes by olefin metathesis is an efficient process for the preparation of common natural product scaffolds such as pyrrolidines, indolizidines and isoindoles.

  10. Desymmetrization of 7-azabicycloalkenes by tandem olefin metathesis for the preparation of natural product scaffolds

    Science.gov (United States)

    Maison, Wolfgang; Büchert, Marina; Deppermann, Nina

    2007-01-01

    Background Tandem olefin metathesis sequences are known to be versatile for the generation of natural product scaffolds and have also been used for ring opening of strained carbo- and heterocycles. In this paper we demonstrate the potential of these reactions for the desymmetrization of 7-azabicycloalkenes. Results We have established efficient protocols for the desymmetrization of different 7-azabicycloalkenes by intra- and intermolecular tandem metathesis sequences with ruthenium based catalysts. Conclusion Desymmetrization of 7-azabicycloalkenes by olefin metathesis is an efficient process for the preparation of common natural product scaffolds such as pyrrolidines, indolizidines and isoindoles. PMID:18088413

  11. Sunflower-based Feedstocks in Nonfood Applications: Perspectives from Olefin Metathesis

    Science.gov (United States)

    Marvey, Bassie B.

    2008-01-01

    Sunflower (Helianthus annuus L.) oil remains under-utilised albeit one of the major seed oils produced world-wide. Moreover, the high oleic sunflower varieties make the oil attractive for applications requiring high temperature processes and those targeting the C=C double bond functionality. Herein an overview of the recent developments in olefin metathesis of sunflower-based feedstocks is presented. The improved performance of olefin metathesis catalysts leading to high turnover numbers, high selectivity and catalyst recyclability, opens new opportunities for tailoring sunflower-based feedstocks into products required for possible new niche market applications. Promising results in biofuel, biopolymers, fragrances and fine chemicals applications have been reported. PMID:19325810

  12. Olefin Hydroborations with Diamidocarbene–BH3 Adducts at Room Temperature

    Directory of Open Access Journals (Sweden)

    Dominika N. Lastovickova

    2016-09-01

    Full Text Available An isolable N,N’-diamidocarbene (DAC was previously shown to promote the B–H bond activation of various BH3 complexes. The resultant DAC–BH3 adducts facilitated olefin hydroborations under mild conditions and in the absence of exogenous initiators. The substrate scope for such transformations was further explored and is described herein. While organoboranes were obtained in quantitative yields from various terminal and internal olefins, use of the latter substrates resulted in intramolecular ring-expansion of the newly formed DAC–borane adducts.

  13. Photopromoted methoxycarbonylation of olefin with methyl formate by Co(OAc)2

    Institute of Scientific and Technical Information of China (English)

    Ying Na Cui; Jing Mei Yin; Da Bin Gao; Ying Ping Jia; Guang Yun Zhou; Shen Min Li

    2007-01-01

    The photopromoted methoxycarbonylation of olefin with methyl formate catalyzed by Co(OAc)2 at ambient conditions has been carried out. The results indicated that the reaction activity increased with the increasing temperature. Methyl formate decomposed into CO and CH3OH firstly under irradiation, and then the methoxycarbonylation of olefin proceeded under catalysis of Co(OAc)2.The mechanism of methyl formate participating in the methoxycarbonylation is verified by the IR analysis and the labeling experiments of CD3OD and CH318OH.

  14. Magnetically stabilized bed reactor for selective hydrogenation of olefins in reformate with amorphous nickel alloy catalyst

    Institute of Scientific and Technical Information of China (English)

    Xuhong Mu; Enze Min

    2007-01-01

    A magnetically stabilized bed (MSB) reactor for selective hydrogenation of olefins in reformate was developed by combining the advantages of MSB and amorphous nickel alloy catalyst. The effects of operating conditions, such as temperature, pressure, liquid space velocity, hydrogen-to-oil ratio, and magnetic field intensity on the reaction were studied. A mathematical model of MSB reactor for hydrogenation of olefins in reformate was established. A reforming flow scheme with a post-hydrogenation MSB reactor was proposed. Finally, MSB hydrogenation was compared with clay treatment and conventional post-hydrogenation.

  15. Cis/trans Coordination in olefin metathesis by static and molecular dynamic DFT calculations

    KAUST Repository

    Poater, Albert

    2014-05-25

    In regard to [(N-heterocyclic carbene)Ru]-based catalysts, it is still a matter of debate if the substrate binding is preferentially cis or trans to the N-heterocyclic carbene ligand. By means of static and molecular dynamic DFT calculations, a simple olefin, like ethylene, is shown to be prone to the trans binding. Bearing in mind the higher reactivity of trans isomers in olefin metathesis, this insight helps to construct small alkene substrates with increased reactivity. © 2014 Springer Science+Business Media New York.

  16. Asymmetric Multilevel Diversity Coding and Asymmetric Gaussian Multiple Descriptions

    CERN Document Server

    Mohajer, Soheil; Diggavi, Suhas N

    2009-01-01

    We consider the asymmetric multilevel diversity (A-MLD) coding problem, where a set of $2^K-1$ information sources, ordered in a decreasing level of importance, is encoded into $K$ messages (or descriptions). There are $2^K-1$ decoders, each of which has access to a non-empty subset of the encoded messages. Each decoder is required to reproduce the information sources up to a certain importance level depending on the combination of descriptions available to it. We obtain a single letter characterization of the achievable rate region for the 3-description problem. In contrast to symmetric multilevel diversity coding, source-separation coding is not sufficient in the asymmetric case, and ideas akin to network coding need to be used strategically. Based on the intuitions gained in treating the A-MLD problem, we derive inner and outer bounds for the rate region of the asymmetric Gaussian multiple description (MD) problem with three descriptions. Both the inner and outer bounds have a similar geometric structure t...

  17. New library of aminosulfonyl-tagged Hoveyda–Grubbs type complexes: Synthesis, kinetic studies and activity in olefin metathesis transformations

    Directory of Open Access Journals (Sweden)

    Etienne Borré

    2010-12-01

    Full Text Available Seven novel Hoveyda–Grubbs precatalysts bearing an aminosulfonyl function are reported. Kinetic studies indicate an activity enhancement compared to Hoveyda’s precatalyst. A selection of these catalysts was investigated with various substrates in ring-closing metathesis of dienes or enynes and cross metathesis. The results demonstrate that these catalysts show a good tolerance to various chemical functions.

  18. New library of aminosulfonyl-tagged Hoveyda–Grubbs type complexes: Synthesis, kinetic studies and activity in olefin metathesis transformations

    Science.gov (United States)

    Borré, Etienne; Caijo, Frederic

    2010-01-01

    Summary Seven novel Hoveyda–Grubbs precatalysts bearing an aminosulfonyl function are reported. Kinetic studies indicate an activity enhancement compared to Hoveyda’s precatalyst. A selection of these catalysts was investigated with various substrates in ring-closing metathesis of dienes or enynes and cross metathesis. The results demonstrate that these catalysts show a good tolerance to various chemical functions. PMID:21165173

  19. Modelling asymmetric growth in crowded plant communities

    DEFF Research Database (Denmark)

    Damgaard, Christian

    2010-01-01

    A class of models that may be used to quantify the effect of size-asymmetric competition in crowded plant communities by estimating a community specific degree of size-asymmetric growth for each species in the community is suggested. The model consists of two parts: an individual size-asymmetric ......A class of models that may be used to quantify the effect of size-asymmetric competition in crowded plant communities by estimating a community specific degree of size-asymmetric growth for each species in the community is suggested. The model consists of two parts: an individual size...

  20. 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.

  1. 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.

  2. Terahertz metamaterial with asymmetric transmission

    CERN Document Server

    Singh, R; Menzel, C; Rockstuhl, C; Azad, A K; Cheville, R A; Lederer, F; Zhang, W; Zheludev, N I

    2009-01-01

    We show for the first time that a planar metamaterial, an array of coupled metal split-ring resonators with a unit cell lacking mirror symmetry, exhibits asymmetric transmission of terahertz radiation propagating through it in opposite directions. This intriguing effect, that is compatible with Lorentz reciprocity and time-reversal, depends on a directional difference in conversion efficiency of the incident circularly polarized wave into one of opposite handedness, that is only possible in lossy low-symmetry planar chiral metamaterials. We show that asymmetric transmission is linked to excitation of enantiomerically sensitive plasmons, these are induced charge-field excitations that depend on the mutual handedness of incident wave and metamaterial pattern. Various bands of positive, negative and zero phase and group velocities have been identified indicating the opportunity to develop polarization sensitive negative index and slow light media based on such metamaterials.

  3. Efficient and selective formation of macrocyclic disubstituted Z alkenes by ring-closing metathesis (RCM) reactions catalyzed by Mo- or W-based monoaryloxide pyrrolide (MAP) complexes: applications to total syntheses of epilachnene, yuzu lactone, ambrettolide, epothilone C, and nakadomarin A.

    Science.gov (United States)

    Wang, Chenbo; Yu, Miao; Kyle, Andrew F; Jakubec, Pavol; Dixon, Darren J; Schrock, Richard R; Hoveyda, Amir H

    2013-02-18

    The first broadly applicable set of protocols for efficient Z-selective formation of macrocyclic disubstituted alkenes through catalytic ring-closing metathesis (RCM) is described. Cyclizations are performed with 1.2-7.5 mol% of a Mo- or W-based monoaryloxide pyrrolide (MAP) complex at 22 °C and proceed to complete conversion typically within two hours. Utility is demonstrated by synthesis of representative macrocyclic alkenes, such as natural products yuzu lactone (13-membered ring: 73% Z) epilachnene (15-membered ring: 91% Z), ambrettolide (17-membered ring: 91% Z), an advanced precursor to epothilones C and A (16-membered ring: up to 97% Z), and nakadomarin A (15-membered ring: up to 97% Z). We show that catalytic Z-selective cyclizations can be performed efficiently on gram-scale with complex molecule starting materials and catalysts that can be handled in air. We elucidate several critical principles of the catalytic protocol: 1) The complementary nature of the Mo catalysts, which deliver high activity but can be more prone towards engendering post-RCM stereoisomerization, versus W variants, which furnish lower activity but are less inclined to cause loss of kinetic Z selectivity. 2) Reaction time is critical to retaining kinetic Z selectivity not only with MAP species but with the widely used Mo bis(hexafluoro-tert-butoxide) complex as well. 3) Polycyclic structures can be accessed without significant isomerization at the existing Z alkenes within the molecule.

  4. 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.

  5. Asymmetrical Γ-Source Inverters

    DEFF Research Database (Denmark)

    Wei, Mo; Poh Chiang, Loh; Blaabjerg, Frede

    2014-01-01

    , inverters with coupled transformers have been introduced, but they usually lead to high turns ratio, and hence many winding turns, at high gain. An alternative would then be the asymmetrical Γ-source inverters proposed in this paper, whose gain is raised by lowering their turns ratio toward unity. The input...... current drawn by the proposed inverters is smoother and, hence, more adaptable by the source. Theories and experimental results have been presented in this paper for validating the concepts proposed....

  6. RuCl3·3H2O Mediated Olefin Isomerizations in Ionic Liquids:A Highly Recyclable System for Olefin Isomerizations

    Institute of Scientific and Technical Information of China (English)

    SHAO Ming-bo; LIU Gui-yan; ZHAO Jing-jing; WANG Xiao-yu; WANG Jian-hui

    2012-01-01

    Herein lies a convenient and highly efficient method of olefin isomerization in the presence of RuCl3·3H2O in ionic liquid(IL).More importantly,RuCl3·3H2O is a robust and recyclable catalyst.Nine cycles of RuCl3·3H2O as the catalyst were performed for the isomerization reactions of the selected substrate in IL and MeOH.

  7. 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...

  8. RUTHENIUM-CATALYZED TANDEM OLEFIN MIGRATION-ALDOL AND MANNICH-TYPE REACTIONS IN IONIC LIQUID.

    Science.gov (United States)

    In the presence of a catalytic amount of RuCl2(PPh3)3, a cross-coupling of 3-buten-2-ol with aldehydes and imines was developed via a tandem olefin migration--aldol--Mannich reaction in bmim[PF6]. With In(OAc)3 as a co-catalyst, a-vinylbenzyl alcohol and aldehydes underwent sim...

  9. Catalyst Design and Development for the Direct Production of Lower Olefins from Synthesis Gas

    NARCIS (Netherlands)

    Xie, Jingxiu

    2017-01-01

    The increase in global demand for lower olefins (ethylene, propylene, and butylenes) coupled with the regional diversification of carbon raw materials bring about opportunities and challenges for emerging technologies. Crude oil has been the primary carbon feedstock for the past 50 years, but altern

  10. Intrinsic pressure response of a single mode cyclo olefin polymer fiber bragg grating

    DEFF Research Database (Denmark)

    Pedersen, Jens Kristian Mølgaard; Woyessa, Getinet; Nielsen, Kristian

    2016-01-01

    The intrinsic pressure response of a Fibre Bragg Grating (FBG) inscribed in a single-mode cyclo olefin polymer (COP) microstructured polymer optical fibre (mPOF) in the range 0-200 bar is investigated for the first time. In order to efficiently suppress the effects from changes in temperature and...

  11. Cationic tungsten-oxo-alkylidene-N-heterocyclic carbene complexes: highly active olefin metathesis catalysts.

    Science.gov (United States)

    Schowner, Roman; Frey, Wolfgang; Buchmeiser, Michael R

    2015-05-20

    The synthesis, structure, and olefin metathesis activity of the first neutral and cationic W-oxo-alkylidene-N-heterocyclic carbene (NHC) catalysts are reported. Neutral W-oxo-alkylidene-NHC catalysts can be prepared in up to 90% isolated yield. Depending on the ligands used, they possess either an octahedral (Oh) or trigonal bipyramidal ligand sphere. They can be activated with excess AlCl3 to form cationic olefin metathesis-active W-complexes; however, these readily convert into neutral chloro-complexes. Well-defined, stable cationic species can be prepared by stoichiometric substitution of one chloro ligand in the parent, neutral W-oxo-alkylidene-NHC complexes with Ag(MeCN)2B(Ar(F))4 or NaB(Ar(F))4; B(Ar(F))4 = B(3,5-(CF3)2-C6H3)4. They are highly active olefin metathesis catalysts, allowing for turnover numbers up to 10,000 in various olefin metathesis reactions including alkenes bearing nitrile, sec-amine, and thioether groups.

  12. Hydrogen bond templated 1:1 macrocyclization through an olefin metathesis/hydrogenation sequence.

    Science.gov (United States)

    Trita, Andrada Stefania; Roisnel, Thierry; Mongin, Florence; Chevallier, Floris

    2013-07-19

    The construction of pyridine-containing macrocyclic architectures using a nonmetallic template is described. 4,6-Dichlororesorcinol was used as an exotemplate to self-organize two aza-heterocyclic units by OH···N hydrogen bonds. Subsequent sequential double olefin metathesis/hydrogenation reactions employing a single ruthenium-alkylidene precatalyst open access to macrocyclic molecules.

  13. Olefin Metathesis Mediated By: - Schiff Base Ru-Alkylidenes -Ru-Alkylidenes Bearing Unsymmetrical NH Ligands

    Science.gov (United States)

    Monsaert, Stijn; Voort, Pascal Van Der; Ledoux, Nele; Allaert, Bart; Drozdzak, Renata; Verpoort, Francis

    The classic Grubbs second-generation complex 2 was modified through 1. The introduction of a bidentate Schiff base ligand 2. Changes in the amino side groups of the NHC ligand Representative olefin metathesis test reactions show the effects induced by the ligand modifications and demonstrate some interesting new properties of the described catalysts. catalysts.

  14. Omega-functionalized fatty acids, alcohols, and ethers via olefin metathesis

    Science.gov (United States)

    Methyl 17-hydroxy stearate was converted to methyl octadec-16-enoate using copper sulfate adsorbed on silica gel. This compound, possessing unsaturation at the opposite end of the chain from the carboxylate, served as a useful substrate for the olefin metathesis reaction. As a result, several fatt...

  15. Attractive Noncovalent Interactions in the Mechanism of Grubbs Second-Generation Ru Catalysts for Olefin Metathesis.

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Yan; Truhlar, Donald G.

    2007-05-10

    Second-generation ruthenium carbenoid catalysts for olefin metathesis are a hundred to a thousand times more active than first-generation catalysts, despite a slower initiation step. A new density functional capable of treating medium-range correlation energy shows that the relative rates of generation of the catalyst are determined by attractive noncovalent interactions.

  16. Continuous reaction performances of benzene alkylation with long chain olefins catalyzed by ionic liquid

    Institute of Scientific and Technical Information of China (English)

    Congzhen QIAO; Chengyue LI

    2008-01-01

    Based on a compulsive mixing-reacting-sepa-rating-recycling small experimental setup,the continuous reaction performances of benzene alkylation with long chain olefins catalyzed by [BMIM]Cl-AlCl3 ionic liquid were investigated. Three different situations including normal continuous operation mode (reagent materials), sidetrack feeding from different axial positions along the static mixing reactor (reagent materials) and normal con-tinuous alkylation using industrial paraffin and olefins materials were examined. Even under the relatively hype-critical reaction conditions, the single pass conversion of pure 1-dodecene could reach to nearly 100.0%, and the selectivity of 2-phenyl isomer was higher than 37.7%. Although the positions along the reactor for sidetrack feeding were different, the 100.0% single pass conversion of 1-dodecene was also attained before the outlet of the reactor. The refined industrial olefins as raw material could meet with the requirements of continuous alkyla-tion. The influences of impurities such as di-olefins and non-benzene aromatics on the catalytic activity and stability should be studied further.

  17. Zirconium-allyl complexes as resting states in zirconocene-catalyzed α-olefin polymerization.

    Science.gov (United States)

    Panchenko, Valentina N; Babushkin, Dmitrii E; Brintzinger, Hans H

    2015-01-01

    UV-vis spectroscopic data indicate that zirconocene cations with Zr-bound allylic chain ends are generally formed during olefin polymerization with zirconocene catalysts. The rates and extent of their formation and of their re-conversion to the initial pre-catalyst cations depend on the types of zirconocene complexes and activators used.

  18. Mild and Efficient Nickel-Catalyzed Heck Reactions with Electron-Rich Olefins

    DEFF Research Database (Denmark)

    Gøgsig, Thomas; Kleimark, Jonatan; Lill, Sten O. Nilsson;

    2012-01-01

    to the conventional regioselective arylation of vinyl ethers. A catalytic system comprised of Ni(COD)2 and 1,1′-bis(diphenylphosphino)ferrocene (DPPF) in combination with the tertiary amine Cy2NMe proved effective in the olefination of a wide range of aryl triflates. Both electron-deficient and electron-rich arenes...

  19. 76 FR 65382 - Regulation of Fuel and Fuel Additives: Alternative Test Method for Olefins in Gasoline

    Science.gov (United States)

    2011-10-21

    ... correlation would be consistent with that specific facility's olefin content range. \\1\\ 76 FR 5319, January 31... rule is not a ``significant regulatory action'' under the terms of Executive Order (EO) 12866 (58 FR... 13132: Federalism Executive Order 13132, entitled ``Federalism'' (64 FR 43255, August 10,...

  20. Fe-Catalyzed Olefin Hydroamination with Diazo Compounds for Hydrazone Synthesis.

    Science.gov (United States)

    Zheng, Jing; Qi, Jifeng; Cui, Sunliang

    2016-01-01

    A novel Fe-catalyzed olefin hydroamination with diazo compounds for accessing hydrazones has been developed. Diazo compounds are used as radical acceptors and can be trapped by the in situ generated alkyl radical toward C-N bond formation. The reaction conditions are mild, and the substrate scope is broad. Additionally, this hydroamination protocol is applicable for intramolecular reactions to construct diverse heterocycles.

  1. Phosphite Ligand Modified Supported Rhodium Catalyst for Hydroformylation of Internal Olefins to Linear Aldehydes

    Institute of Scientific and Technical Information of China (English)

    LI Xian-ming; DING Yun-jie; JIAO Gui-ping; LI Jing-wei; YAN Li; ZHU He-jun

    2009-01-01

    A phosphite ligand modified heterogeneous catalyst was developed for the hydroformylation of internal olefins to linear aldehydes, which showed a high activity and high regioselectivity and could be separated easily by filtration after reaction in an autoclave. Three nanoporous silica sieves were used to investigate the influence of pore structure and shape selective performance of support on the regioselectivity to the linear products.

  2. Practical and General Palladium-Catalyzed Synthesis of Ketones from Internal Olefins

    KAUST Repository

    Morandi, Bill

    2013-01-16

    Make it simple! A convenient and general palladium-catalyzed oxidation of internal olefins to ketones is reported. The transformation occurs at room temperature and shows wide substrate scope. Applications to the oxidation of seed-oil derivatives and a bioactive natural product (see scheme) are described, as well as intriguing mechanistic features.

  3. Cobalt-catalyzed C-H olefination of aromatics with unactivated alkenes.

    Science.gov (United States)

    Manoharan, Ramasamy; Sivakumar, Ganesan; Jeganmohan, Masilamani

    2016-08-18

    A cobalt-catalyzed C-H olefination of aromatic and heteroaromatic amides with unactivated alkenes, allyl acetates and allyl alcohols is described. This method offers an efficient route for the synthesis of vinyl and allyl benzamides in a highly stereoselective manner. It is observed that the ortho substituent on the benzamide moiety is crucial for the observation of allylated products in unactivated alkenes.

  4. Steam cracking and methane to olefins: Energy use, CO2 emissions and production costs

    NARCIS (Netherlands)

    Ren, T.; Patel, M.K.; Blok, K.

    2008-01-01

    While most olefins (e.g., ethylene and propylene) are currently produced through steam cracking routes, they can also possibly be produced from natural gas (i.e., methane) via methanol and oxidative coupling routes. We reviewed recent data in the literature and then compared the energy use, CO2 emis

  5. NATO Advanced Study Institute on Ring-opening Metathesis Polymerization of Olefins and Polymerization of Alkynes

    CERN Document Server

    1998-01-01

    The first NATO Advanced Study Institute on Olefin Metathesis and Polymerization Catalysts was held on September 10-22, 1989 in Akcay, Turkey. Based on the fundamental research of RRSchrock, RGrubbs and K.B.Wagener in the field of ring opening metathesis polymerization (ROMP), acyclic diene metathesis (ADMET) and alkyne polymerization, these areas gained growing interest within the last years. Therefore the second NATO-ASI held on metathesis reactions was on Ring Opening Metathesis Po­ lymerization of Olefins and Polymerization of Alkynes on September 3-16, 1995 in Akcay, Turkey. The course joined inorganic, organic and polymer chemists to exchange their knowledge in this field. This volume contains the main and short lectures held in Akcay. To include ADMET reactions better into the title of this volume we changed it into: Metathesis Polymerization of Olefins and Alkyne Polymerization. This volume is addressed to research scientists, but also to those who start to work in the area of olefin metathesis and al...

  6. Final Report: Experimental and Theoretical Studies of Surface Oxametallacycles - Connections to Heterogeneous Olefin Epoxidation

    Energy Technology Data Exchange (ETDEWEB)

    Mark A. Barteau

    2009-09-15

    This project has aimed at the rational design of catalysts for direct epoxidation of olefins. This chemistry remains one of the most challenging problems in heterogeneous catalysis. Although the epoxidation of ethylene by silver catalysts to form ethylene oxide (EO) has been practiced for decades, little progress has been made in expanding this technology to other products and processes. We have made significant advances through the combination of surface science experiments, Density Functional Theory (DFT) calculations, and catalytic reactor experiments, toward understanding the mechanism of this reaction on silver catalysts, and to the rational improvement of selectivity. The key has been our demonstration of surface oxametallacycle intermediates as the species that control reaction selectivity. This discovery permits the influence of catalyst promoters on selectivity to be probed, and new catalyst formulations to be developed. It also guides the development of new chemistry with potential for direct epoxidation of more complex olefins. During the award period we have focused on 1. the formation and reaction selectivity of complex olefin epoxides on silver surfaces, and 2. the influence of co-adsorbed oxygen atoms on the reactions of surface oxametallacycles on silver, and 3. the computational prediction, synthesis, characterization and experimental evaluation of bimetallic catalysts for ethylene epoxidation. The significance of these research thrusts is as follows. Selective epoxidation of olefins more complex than ethylene requires suppression of not only side reactions available to the olefin such as C-H bond breaking, but it requires formation and selective ring closure of the corresponding oxametallacycle intermediates. The work carried out under this grant has significantly advanced the field of catalyst design from first principles. The combination of computational tools, surface science, and catalytic reactor experiments in a single laboratory has few

  7. Mechanistic insights on platinum- and palladium-pincer catalyzed coupling and cyclopropanation reactions between olefins.

    Science.gov (United States)

    Rajeev, Ramanan; Sunoj, Raghavan B

    2012-07-21

    The mechanism of M(II)-PNP-pincer catalyzed reaction between (i) ethene, (ii) trans-butene with 2-methylbut-2-ene, 2,3-dimethylbut-2-ene and tert-butylbutene is examined by using density functional theory methods (where M = Pt or Pd). All key intermediates and transition states involved in the reaction are precisely located on the respective potential energy surfaces using the popular DFT functionals such as mPW1K, M06-2X, and B3LYP in conjunction with the 6-31+G** basis set. The reaction between these olefins can lead to a linear coupling product or a substituted cyclopropane. The energetic comparison between coupling as well as cyclopropanation pathways involving four pairs of olefins for both platinum (1-4) and palladium (5-8) catalyzed reactions is performed. The key events in the lower energy pathway in the mechanistic course involves (i) a C-C bond formation between the metal bound olefin (ethene or trans-butene) and a free olefin, and (ii) two successive [1,2] hydrogen migrations in the ensuing carbocationic intermediates (1c-4c, and 1d-4d), toward the formation of the coupling product. The computed barriers for these steps in the reaction of metal bound ethene to free tert-butylbutene (or other butenes) are found to be much lower than the corresponding steps when trans-butene is bound to the metal pincer. The Gibbs free energy differences between the transition states leading to the coupling product (TS(d-e)) and that responsible for cyclopropanated product (TS(d-g)) are found to be diminishingly closer in the case of the platinum pincer as compared to that in the palladium system. The computed energetics indicate that the coupled product prefers to remain as a metal olefin complex, consistent with the earlier experimental reports.

  8. Cobalt carbide nanoprisms for direct production of lower olefins from syngas

    Science.gov (United States)

    Zhong, Liangshu; Yu, Fei; An, Yunlei; Zhao, Yonghui; Sun, Yuhan; Li, Zhengjia; Lin, Tiejun; Lin, Yanjun; Qi, Xingzhen; Dai, Yuanyuan; Gu, Lin; Hu, Jinsong; Jin, Shifeng; Shen, Qun; Wang, Hui

    2016-10-01

    Lower olefins—generally referring to ethylene, propylene and butylene—are basic carbon-based building blocks that are widely used in the chemical industry, and are traditionally produced through thermal or catalytic cracking of a range of hydrocarbon feedstocks, such as naphtha, gas oil, condensates and light alkanes. With the rapid depletion of the limited petroleum reserves that serve as the source of these hydrocarbons, there is an urgent need for processes that can produce lower olefins from alternative feedstocks. The ‘Fischer-Tropsch to olefins’ (FTO) process has long offered a way of producing lower olefins directly from syngas—a mixture of hydrogen and carbon monoxide that is readily derived from coal, biomass and natural gas. But the hydrocarbons obtained with the FTO process typically follow the so-called Anderson-Schulz-Flory distribution, which is characterized by a maximum C2-C4 hydrocarbon fraction of about 56.7 per cent and an undesired methane fraction of about 29.2 per cent (refs 1, 10, 11, 12). Here we show that, under mild reaction conditions, cobalt carbide quadrangular nanoprisms catalyse the FTO conversion of syngas with high selectivity for the production of lower olefins (constituting around 60.8 per cent of the carbon products), while generating little methane (about 5.0 per cent), with the ratio of desired unsaturated hydrocarbons to less valuable saturated hydrocarbons amongst the C2-C4 products being as high as 30. Detailed catalyst characterization during the initial reaction stage and theoretical calculations indicate that preferentially exposed {101} and {020} facets play a pivotal role during syngas conversion, in that they favour olefin production and inhibit methane formation, and thereby render cobalt carbide nanoprisms a promising new catalyst system for directly converting syngas into lower olefins.

  9. Asymmetric Schiff bases derived from diaminomaleonitrile and their metal complexes

    Science.gov (United States)

    Yang, Jianjie; Shi, Rufei; Zhou, Pei; Qiu, Qiming; Li, Hui

    2016-02-01

    Asymmetric Schiff bases, due to its asymmetric structure, can be used as asymmetric catalyst, antibacterial, and mimic molecules during simulate biological processes, etc. In recent years, research on synthesis and properties of asymmetric Schiff bases have become an increase interest of chemists. This review summarizes asymmetric Schiff bases derived from diaminomaleonitrile (DAMN) and DAMN-based asymmetric Schiff bases metal complexes. Applications of DAMN-based asymmetric Schiff bases are also discussed in this review.

  10. Part I: Reverse-docking studies of a squaramide-catalyzed conjugate addition of a diketone to a nitro-olefin Part II: The development of ChemSort: an education game for organic chemistry

    Science.gov (United States)

    Granger, Jenna Christine

    Part 1: Reverse-docking studies of a squaramide-catalyzed conjugate addition of a diketone to a nitro-olefin. Asymmetric organocatalysis, the catalysis of asymmetric reactions by small organic molecules, is a rapidly growing field within organic synthesis. The ability to rationally design organocatalysts is therefore of increasing interest to organic chemists. Computational chemistry is quickly proving to be an extremely successful method for understanding and predicting the roles of organocatalysts, and therefore is certain to be of use in the rational design of such catalysts. A methodology for reverse-docking flexible organocatalysts to rigid transition state models of asymmetric reactions has been previously developed by the Deslongchamps group. The investigation of Rawal's squaramide-based organocatalyst for the addition of a diketone to a nitro-olefin is described, and the results of the reverse docking of Rawal's catalyst to the geometry optimized transition state models of the uncatalyzed reaction for both the R and S-product enantiomers are presented. The results of this study indicate a preference for binding of the organocatalyst to the R-enantiomer transition state model with a predicted enantiomeric excess of 99%, which is consistent with the experimental results. A plausible geometric model of the transition state for the catalyzed reaction is also presented. The success of this study demonstrates the credibility of using reverse docking methods for the rational design of asymmetric organocatalysts. Part 2: The development of ChemSort: an educational game for organic chemistry. With the advent of the millennial learner, we need to rethink traditional classroom approaches to science learning in terms of goals, approaches, and assessments. Digital simulations and games hold much promise in support of this educational shift. Although the idea of using games for education is not a new one, well-designed computer-based "serious games" are only beginning to

  11. Rapid Identification and Quantification of Linear Olefin Isomers by Online Ozonolysis-Single Photon Ionization Time-of-Flight Mass Spectrometry.

    Science.gov (United States)

    Xie, Yuanyuan; Chen, Ping; Hua, Lei; Hou, Keyong; Wang, Yongchao; Wang, Haiyan; Li, Haiyang

    2016-01-01

    The specific locations of the double bonds in linear olefins can facilitate olefin catalytic synthetic reactions to improve the quality of target olefin products. We developed a simple and efficient approach based on single photon ionization time-of-flight mass spectrometry (SPI-TOFMS) combined with online ozonolysis to identify and quantify the linear olefin double bond positional isomers. The online ozonolysis cleaved the olefins at the double bond positions that led to formation of corresponding characteristic aldehydes. The aldehydes were then detected by SPI-TOFMS to achieve unique spectrometric "fingerprints" for each linear olefin to successfully identify the isomeric ones. To accurately quantify the isomeric components in olefin mixtures, an algorithm was proposed to quantify three isomeric olefin mixtures based on characteristic ion intensities and their equivalent ionization coefficients. The relative concentration errors for the olefin components were lower than 2.5% while the total analysis time was less than 2 min. These results demonstrate that the online ozonolysis SPI-TOFMS has the potential for real-time monitoring of catalytic olefin synthetic reactions.

  12. Spontaneous baryogenesis from asymmetric inflaton

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, Fuminobu [Tohoku Univ., Sendai (Japan). Dept. of Physics; Tokyo Univ., Chiba (Japan). Kavli IPMU (WPI), UTIAS; Yamada, Masaki [Tokyo Univ., Chiba (Japan). Kavli IPMU (WPI), UTIAS; Tokyo Univ., Chiba (Japan). Inst. for Cosmic Ray Research; DESY Hamburg (Germany)

    2015-10-15

    We propose a variant scenario of spontaneous baryogenesis from asymmetric inflaton based on current-current interactions between the inflaton and matter fields with a non-zero B-L charge. When the inflaton starts to oscillate around the minimum after inflation, it may lead to excitation of a CP-odd component, which induces an effective chemical potential for the B-L number through the current-current interactions. We study concrete inflation models and show that the spontaneous baryogenesis scenario can be naturally implemented in the chaotic inflation in supergravity.

  13. The asymmetric Goos-H\\"anchen effect

    OpenAIRE

    Araujo, Manoel P.; Carvalho, Silvânia A.; De Leo, Stefano

    2013-01-01

    We show in which conditions optical gaussian beams, propagating throughout an homogeneous dielectric right angle prism, present an asymmetric Goos-H\\"anchen (GH) effect. This asymmetric behavior is seen for incidence at critical angles and happens in the propagation direction of the outgoing beam. The asymmetric GH effect can be also seen as an amplification of the standard GH shift. Due to the fact that it only depends on the ratio between the wavelength and the minimal waist size of the inc...

  14. Review of Composite Asymmetric Spur Gear

    OpenAIRE

    Sandeep C. Dhaduti; Dr. S. G. Sarganachari

    2015-01-01

    Gears made from composite materials are widely used in many power and motion transmission applications. Due to lower weight to stiffness ratio, composite gears may be replaced by conventional material gears in power transmission systems. Design of gears with asymmetric teeth enables to increase load capacity, reduce weight, size and vibration level. This article includes a summary of asymmetric gear design parameters, new developments of asymmetric spur gear and their ...

  15. The asymmetric Goos-H\\"anchen effect

    CERN Document Server

    Araujo, Manoel P; De Leo, Stefano

    2014-01-01

    We show in which conditions optical gaussian beams, propagating throughout an homogeneous dielectric right angle prism, present an asymmetric Goos-H\\"anchen (GH) effect. This asymmetric behavior is seen for incidence at critical angles and happens in the propagation direction of the outgoing beam. The asymmetric GH effect can be also seen as an amplification of the standard GH shift. Due to the fact that it only depends on the ratio between the wavelength and the minimal waist size of the incoming gaussian beam, it can be also used to determine one of these parameters. Multiple peaks interference is an additional phenomenon seen in the presence of such asymmetric effects.

  16. Efficient and Selective Formation of Macrocyclic Disubstituted Z Alkenes by Ring-Closing Metathesis (RCM) Reactions Catalyzed by Mo- or W-Based Monoaryloxide Pyrrolide (MAP) Complexes. Applications to Total Syntheses of Epilachnene, Yuzu Lactone, Ambrettolide, Epothilone C and Nakadomarin A

    Science.gov (United States)

    Wang, Chenbo; Yu, Miao; Kyle, Andrew F.; Jakubec, Jakubec; Dixon, Darren J.; Schrock, Richard R.; Hoveyda, Amir H.

    2014-01-01

    The first broadly applicable set of protocols for efficient and highly Z-selective formation of macrocyclic disubstituted alkenes through catalytic ring-closing metathesis (RCM) is described. Cyclizations are performed in the presence of 1.2–7.5 mol % of a Mo- or W-based mono-aryloxide pyrrolide (MAP) complex at 22 °C and typically proceed to complete conversion within two hours. The utility of the catalytic strategy is demonstrated by stereoselective synthesis of representative macrocyclic alkenes, including natural products yuzu lactone (13-membered ring: 73% Z) epilachnene (15-membered ring: 91% Z), ambrettolide (17-membered ring: 91% Z), an advanced precursor to epothilones C and A (16-membered ring: up to 97% Z) and nakadomarin A (polycyclic 15-membered ring: up to 97% Z). We demonstrate the complementary nature of the Mo-based catalysts, which deliver high activity but can be more prone to causing post-RCM stereoisomerization, versus W-based variants, which furnish lower activity but are less inclined towards causing loss of kinetic Z selectivity; a number of catalytic Z-selective cases are provided to elucidate which catalyst class is best suited for which substrate and particular type of alkene RCM process. Mechanistic models that rationalize the origin and the trends in Z selectivity as a function of alterations in the catalyst structure (i.e., Mo vs W and different imido and aryloxide or alkoxide ligands) are provided; we show that reaction time can be critical in retaining the Z selectivity attained not only with MAP complexes but with the original Mo-based bis-alkoxides as well. The W-based catalysts are sufficiently stable to be manipulated in air even with humidity levels of up to 80%; the catalytic Z-selective cyclizations can be performed on gram scale with complex molecule starting materials. PMID:23345004

  17. A Comparison of the Performance of the Semiempirical PM6 Method Versus DFT Methods in Ru-Catalyzed Olefin Metathesis

    Science.gov (United States)

    Correa, Andrea; Poater, Albert; Ragone, Francesco; Cavallo, Luigi

    In this work we compare the performance of the semiempirical PM6 method with a more accurate DFT method when applied to Ru-catalyzed olefin metathesis. We demonstrate that the PM6 method reproduces with interesting accuracy the geometries located with a DFT approach. As for the energetics, the relative DFT stability of the metallacycle with respect to the coordination intermediate is reproduced with reasonable accuracy by the PM6 method, whereas the olefin coordination energy and the energy barrier of the metathesis step are overestimated. Further, for the same system we performed a PM6-based meta-dynamics study of the olefin metathesis reaction, which indicated a reasonable good behavior of the system also under dynamic conditions. In conclusion, the obtained results validate the use of the semiempirical PM6 method for preliminary and computationally fast screening on new ligands/substrates in Ru catalyzed olefin metathesis.

  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. Excitons in asymmetric quantum wells

    Science.gov (United States)

    Grigoryev, P. S.; Kurdyubov, A. S.; Kuznetsova, M. S.; Ignatiev, I. V.; Efimov, Yu. P.; Eliseev, S. A.; Petrov, V. V.; Lovtcius, V. A.; Shapochkin, P. Yu.

    2016-09-01

    Resonance dielectric response of excitons is studied for the high-quality InGaAs/GaAs heterostructures with wide asymmetric quantum wells (QWs). To highlight effects of the QW asymmetry, we have grown and studied several heterostructures with nominally square QWs as well as with triangle-like QWs. Several quantum confined exciton states are experimentally observed as narrow exciton resonances. A standard approach for the phenomenological analysis of the profiles is generalized by introducing different phase shifts for the light waves reflected from the QWs at different exciton resonances. Good agreement of the phenomenological fit to the experimentally observed exciton spectra for high-quality structures allowed us to reliably obtain parameters of the exciton resonances: the exciton transition energies, the radiative broadenings, and the phase shifts. A direct numerical solution of the Schrödinger equation for the heavy-hole excitons in asymmetric QWs is used for microscopic modeling of the exciton resonances. Remarkable agreement with the experiment is achieved when the effect of indium segregation is taken into account. The segregation results in a modification of the potential profile, in particular, in an asymmetry of the nominally square QWs.

  20. 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.

  1. On the impact of olefins and aromatics in the methanol-to-hydrocarbon conversion over H-ZSM-5 catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Sun, X.; Mueller, S.; Veen, A.C. van; Lercher, J.A. [Technische Univ. Muenchen, Garching (Germany). Dept. of Chemistry

    2012-07-01

    Methanol-to-hydrocarbons processes using HZSM-5 archetype acidic zeolites or zeotype SAPO-34 catalysts are regarded as a vital suite of conversion technologies to bypass petroleum-based routes for the production of specific fuels and petrochemical commodities. Special significance of the methanol chemistry originates from its versatility enabling selective transformations towards various products. Industry demonstrated successfully implementations of Methanol-To-Gasoline, Methanol-To-Olefin, and Methanol-To-Propylene processes, although the typical single-pass selectivity remained limited and recycling is necessary. Considerable fundamental research efforts both from experimental and computational sides contributed to unravel the underlying complex reaction mechanism. The indirect hydrocarbon pool mechanism, in which Broensted acid sites combined with adsorbed light olefins or lower methylbenzenes act as active centers, is generally accepted to explain the formation of light olefins. As olefin and aromatics populated catalytic sites show different reactivity in terms of activity and selectivity to ethylene or propylene, one could envision optimizing the product distribution by suitable co-feeding of specific hydrocarbons. The present work addresses three questions with an experimental study conducted under realistic MTP operation conditions: (1) How are ethylene and propylene formed at molecular level? (2) Which reaction pathway leads to the formation of undesired hydrogen transfer products? (3) Does olefin or aromatics co-feeding change the selectivity to ethylene or propylene? Xylenes and various olefins were co-fed with methanol to achieve a detailed understanding of the reaction mechanism over acidic HZSM-5 zeolites. Results suggest, that an olefin homologation/cracking route (olefin cycle) accounts for the autocatalytic (-like) nature and the majority of methanol consumption rather than the route involving aromatic intermediates (aromatics cycle). Co

  2. Synthesis of Z-alkenes from Rh(I)-catalyzed olefin isomerization of β,γ-unsaturated ketones.

    Science.gov (United States)

    Zhuo, Lian-Gang; Yao, Zhong-Ke; Yu, Zhi-Xiang

    2013-09-20

    Developing olefin isomerization reactions to reach kinetically controlled Z-alkenes is challenging because formation of trans-alkenes is thermodynamically favored under the traditional catalytic conditions using acids, bases, or transition metals as the catalysts. A new synthesis of Z-alkenes from Rh(I)-catalyzed olefin isomerization of β,γ-unsaturated ketones to α,β-unsaturated ketones was developed, providing an easy and efficient way to access various Z-enones.

  3. Anodic aluminium oxide catalytic membranes for asymmetric epoxidation.

    Science.gov (United States)

    Cho, So-Hye; Walther, Nolan D; Nguyen, SonBinh T; Hupp, Joseph T

    2005-11-14

    Catechol-functionalized (salen)Mn complexes can be supported on mesoporous anodized aluminium oxide disks to yield catalytic membranes that are highly active in the enantioselective epoxidation of olefins when being deployed in a forced-through-flow reactor.

  4. Asymmetric catalysis : ligand design and microwave acceleration

    OpenAIRE

    Bremberg, Ulf

    2000-01-01

    This thesis deals partly with the design and synthesis ofligands for use in asymmetric catalysis, and partly with theapplication of microwave heating on metal-based asymmetriccatalytic reactions. Enantiomerically pure pyridyl alcohols and bipyridylalcohols were synthesized from the chiral pool for future usein asymmetric catalysis. Lithiated pyridines were reacted withseveral chiral electrophiles, yielding diastereomeric mixturesthat could be separated without the use of resolutiontechniques....

  5. Worst Asymmetrical Short-Circuit Current

    DEFF Research Database (Denmark)

    Arana Aristi, Iván; Holmstrøm, O; Grastrup, L

    2010-01-01

    In a typical power plant, the production scenario and the short-circuit time were found for the worst asymmetrical short-circuit current. Then, a sensitivity analysis on the missing generator values was realized in order to minimize the uncertainty of the results. Afterward the worst asymmetrical...

  6. Renewable resource management under asymmetric information

    DEFF Research Database (Denmark)

    Jensen, Frank; Andersen, Peder; Nielsen, Max

    2013-01-01

    Asymmetric information between fishermen and the regulator is important within fisheries. The regulator may have less information about stock sizes, prices, costs, effort, productivity and catches than fishermen. With asymmetric information, a strong analytical tool is principal-agent analysis. I...

  7. The Catalytic Asymmetric Intramolecular Stetter Reaction.

    Science.gov (United States)

    de Alaniz, Javier Read; Rovis, Tomislav

    2009-05-01

    This account chronicles our efforts at the development of a catalytic asymmetric Stetter reaction using chiral triazolium salts as small molecule organic catalysts. Advances in the mechanistically related azolium-catalyzed asymmetric benzoin reaction are discussed, particularly as they apply to catalyst design. A chronological treatise of reaction discovery, catalyst optimization and reactivity extension follows.

  8. Synthesis of linear [5]catenanes via olefin metathesis dimerization of pseudorotaxanes composed of a [2]catenane and a secondary ammonium salt.

    Science.gov (United States)

    Iwamoto, Hajime; Tafuku, Shinji; Sato, Yoshihiko; Takizawa, Wataru; Katagiri, Wataru; Tayama, Eiji; Hasegawa, Eietsu; Fukazawa, Yoshimasa; Haino, Takeharu

    2016-01-01

    [5]Catenanes were synthesized by olefin metathesis dimerization. The reaction of pseudorotaxanes, which were derived from a [2]catenane and one equivalent of an ammonium salt bearing two terminal olefins in dichloromethane, with a catalytic amount of Grubbs catalyst afforded linear [5]catenanes in 12% yield. Intermolecular and intramolecular olefin metathesis reactions were controlled by the length of the alkyl chain of the ammonium salts.

  9. Condensation on Slippery Asymmetric Bumps

    CERN Document Server

    Park, Kyoo-Chul; He, Neil; Aizenberg, Joanna

    2015-01-01

    Bumps are omnipresent from human skin to the geological structures on planets, which offer distinct advantages in numerous phenomena including structural color, drag reduction, and extreme wettability. Although the topographical parameters of bumps such as radius of curvature of convex regions significantly influence various phenomena including anti-reflective structures and contact time of impacting droplets, the effect of the detailed bump topography on growth and transport of condensates have not been clearly understood. Inspired by the millimetric bumps of the Namib Desert beetle, here we report the identified role of radius of curvature and width of bumps with homogeneous surface wettability in growth rate, coalescence and transport of water droplets. Further rational design of asymmetric convex topography and synergetic combination with slippery coating simultaneously enable self-transport, leading to unseen five-fold higher growth rate and an order of magnitude faster shedding time of droplets compared...

  10. Synthesis and characterization of new magnetically recoverable molybdenum nanocatalyst for epoxidation of olefins

    Energy Technology Data Exchange (ETDEWEB)

    Masteri-Farahani, M., E-mail: mfarahany@yahoo.com [Faculty of Chemistry, University of Tarbiat Moallem, Tehran (Iran, Islamic Republic of); Kashef, Z. [Faculty of Chemistry, University of Tarbiat Moallem, Tehran (Iran, Islamic Republic of)

    2012-04-15

    New heterogeneous molybdenum catalyst was prepared through covalent attachment of a Schiff base ligand on the surface of silica coated magnetite nanoparticles via aminopropyl spacer and subsequent complexation with MoO{sub 2}(acac){sub 2}. The prepared nanocatalyst was characterized with Fourier transform infrared spectroscopy, X-ray diffraction, scanning and transmission electron microscopies and vibrating sample magnetometry. Catalytic epoxidation of some olefins and allylic alcohols by prepared nanocatalyst using tert-butyl hydroperoxide and cumene hydroperoxide as oxidants was achieved with good activities and selectivities. - Highlights: Black-Right-Pointing-Pointer Silica coated magnetite nanoparticles were modified with a Schiff base ligand. Black-Right-Pointing-Pointer Next reaction with MoO{sub 2}(acac){sub 2} afforded magnetically recoverable nanocatalyst. Black-Right-Pointing-Pointer The prepared nanocatalyst catalyzed the epoxidation of olefins with TBHP.

  11. Synthesis and properties of new bolaform and macrocyclic galactose-based surfactants obtained by olefin metathesis.

    Science.gov (United States)

    Satgé, Céline; Granet, Robert; Verneuil, Bernard; Champavier, Yves; Krausz, Pierre

    2004-05-17

    A series of galactose-based surfactants with various structures likely to display new interesting properties were synthesized. Four monocatenary surfactants were elaborated by microwave-assisted galactosylation of undecanol or 10-undecenol. These compounds were slightly soluble in water. Their tensioactive properties were determined at 45 degrees C. Olefin metathesis was used to synthesize the two single-chain bolaforms from undec-10-enyl galactopyranosides; two pseudomacrocyclic bolaforms were prepared by grafting two carbamates at O-4 and O-4' sugar positions of the single-chain bolaforms. These four surfactants are insoluble in water and undergo monolayer compression. Cyclization of these bolaforms by olefin metathesis led to macrocyclic surfactant analogues of archaeobacterial membrane components.

  12. Sunflower-based Feedstocks in Nonfood Applications: Perspectives from Olefin Metathesis

    Directory of Open Access Journals (Sweden)

    Bassie B. Marvey

    2008-08-01

    Full Text Available Sunflower (Helianthus annuus L. oil remains under-utilised albeit one of the major seed oils produced world-wide. Moreover, the high oleic sunflower varieties make the oil attractive for applications requiring high temperature processes and those targeting the C=C double bond functionality. Herein an overview of the recent developments in olefin metathesis of sunflower-based feedstocks is presented. The improved performance of olefin metathesis catalysts leading to high turnover numbers, high selectivity and catalyst recyclability, opens new opportunities for tailoring sunflower-based feedstocks into products required for possible new niche market applications. Promising results in biofuel, biopolymers, fragrances and fine chemicals applications have been reported.

  13. The activation mechanism of Ru-indenylidene complexes in olefin metathesis.

    Science.gov (United States)

    Urbina-Blanco, César A; Poater, Albert; Lebl, Tomas; Manzini, Simone; Slawin, Alexandra M Z; Cavallo, Luigi; Nolan, Steven P

    2013-05-01

    Olefin metathesis is a powerful tool for the formation of carbon-carbon double bonds. Several families of well-defined ruthenium (Ru) catalysts have been developed during the past 20 years; however, the reaction mechanism for all such complexes was assumed to be the same. In the present study, the initiation mechanism of Ru-indenylidene complexes was examined and compared with that of benzylidene counterparts. It was discovered that not all indenylidene complexes followed the same mechanism, highlighting the importance of steric and electronic properties of so-called spectator ligands, and that there is no single mechanism for the Ru-based olefin metathesis reaction. The experimental findings are supported quantitatively by DFT calculations.

  14. High-Performance Isocyanide Scavengers for Use in Low-Waste Purification of Olefin Metathesis Products.

    Science.gov (United States)

    Szczepaniak, Grzegorz; Urbaniak, Katarzyna; Wierzbicka, Celina; Kosiński, Krzysztof; Skowerski, Krzysztof; Grela, Karol

    2015-12-21

    Three isocyanides containing a tertiary nitrogen atom were investigated for use as small-molecule ruthenium scavenging agents in the workup of olefin metathesis reactions. The proposed compounds are odorless, easy to obtain, and highly effective in removing metal residues, sometimes bringing the metal content below 0.0015 ppm. The most successful of the tested compounds, II, performs very well, even with challenging polar products. The performance of these scavengers is compared and contrasted with other known techniques, such as silica gel filtration and the use of self-scavenging catalysts. As a result, a new hybrid purification method is devised, which gives better results than using either a self-scavenging catalyst or a scavenger alone. Additionally, isocyanide II is shown to be a deactivating (reaction quenching) agent for olefin metathesis and superior to ethyl vinyl ether.

  15. Olefin metathesis reaction on a MoS/sub 2/ catalyst

    Energy Technology Data Exchange (ETDEWEB)

    1976-06-15

    Olefin metathesis reaction was found to take place on rather pure MoS/sub 2/ evacuated at 450/sup 0/C for several hours. Systematic studies of the isotopic scrambling in ethylene, propylene, 1-butene, and 2-butene on MoS/sub 2/ using microwave spectroscopy are reported. These studies were made using /sup 12/C- and /sup 13/C-labelled compounds and D-labelled compounds. Results indicated that the MoS/sub 2/ catalyst evacuated at 450/sup 0/C has two kinds of active sites, one is effective for the isomerization and the hydrogen isotopic mixing of olefins, and the other is effective for the hydrogenation reaction. This may be explained by assuming different degrees of coordinative unsaturation for the active sites. (BLM)

  16. An expedient route to substituted furans via olefin cross-metathesis

    Science.gov (United States)

    Donohoe, Timothy J.; Bower, John F.

    2010-01-01

    The olefin cross-metathesis (CM) reaction is used extensively in organic chemistry and represents a powerful method for the selective synthesis of differentially substituted alkene products. Surprisingly, efforts to integrate this remarkable process into strategies for aromatic and heteroaromatic construction have not been reported. Such structures represent key elements of the majority of small molecule drug compounds; methods for the controlled preparation of highly substituted derivatives are essential to medicinal chemistry. Here we show that the olefin CM reaction, in combination with an acid cocatalyst or subsequent Heck arylation, provides a concise and flexible entry to 2,5-di- or 2,3,5-tri-substituted furans. These cascade processes portend further opportunities for the regiocontrolled preparation of other highly substituted aromatic and heteroaromatic classes. PMID:20142508

  17. Highly diastereoselective and enantioselective olefin cyclopropanation using engineered myoglobin-based catalysts.

    Science.gov (United States)

    Bordeaux, Melanie; Tyagi, Vikas; Fasan, Rudi

    2015-02-01

    Using rational design, an engineered myoglobin-based catalyst capable of catalyzing the cyclopropanation of aryl-substituted olefins with catalytic proficiency (up to 46,800 turnovers) and excellent diastereo- and enantioselectivity (98-99.9%) was developed. This transformation could be carried out in the presence of up to 20 g L(-1) olefin substrate with no loss in diastereo- and/or enantioselectivity. Mutagenesis and mechanistic studies support a cyclopropanation mechanism mediated by an electrophilic, heme-bound carbene species and a model is provided to rationalize the stereopreference of the protein catalyst. This work shows that myoglobin constitutes a promising and robust scaffold for the development of biocatalysts with carbene-transfer reactivity.

  18. Substantially isotactic, linear, alternating copolymers of carbon monoxide and an olefin

    Science.gov (United States)

    Sen, Ayusman; Jiang, Zhaozhong

    1996-01-01

    The compound, [Pd(Me-DUPHOS)(MeCN).sub.2 ](BF.sub.4).sub.2, [Me-DUPHOS: 1,2-bis(2,5-dimethylphospholano)benzene] is an effective catalyst for the highly enantioselective, alternating copolymerization of olefins, such as aliphatic .alpha.-olefins, with carbon monoxide to form optically active, isotactic polymers which can serve as excellent starting materials for the synthesis of other classes of chiral polymers. For example, the complete reduction of a propylene-carbon monoxide copolymer resulted in the formation of a novel, optically active poly(1,4-alcohol). Also, the previously described catalyst is a catalyst for the novel alternating isomerization cooligomerization of 2-butene with carbon monoxide to form optically active, isotactic poly(1,5-ketone)

  19. Efficient Hydration of Olefins Catalyzed by Wool-Supported Palladium Complex

    Institute of Scientific and Technical Information of China (English)

    Dan-Ni SUI; Si-Qian WANG; Xin WANG; Mei-Yu HUANG; Ying-Yan JIANG

    2005-01-01

    @@ 1Introduction The hydration of olefins is one of the most important prxesses for the production of alcohols[1]. Both transition metal complexes[2] and enzymes[3] have been reported to catalyze the hydration of alkenes, but their catalysts are usually tither unstable or difficult to prepare, expensive and sometimes can not be easily recovered.In our previous papers, some natural biopolymer-metal complexes[4-6] have been used as effective catalysts in hydration to overcome above disadvantages. Recently, wool-Palladium complex(Wool-Pd) has been prepared and found to be able to effficiently catalyze the hydration of olefins to alcohols, such as cinnamyl alcohol(1a) to 1-phenyl-1,3-propanediol(1b), acrylic acid(2a) to lactic acid(2b), 4-vinyl pyridine(3a) to α-methyl-4-pyridinemethanol (3b) and acrylamide(4a) to 1-hydroxyethylamide(4b) respectively in high yields under mild conditions. See scheme 1.

  20. Layered transition metal carboxylates: efficient reusable heterogeneous catalyst for epoxidation of olefins.

    Science.gov (United States)

    Sen, Rupam; Bhunia, Susmita; Mal, Dasarath; Koner, Subratanath; Miyashita, Yoshitaro; Okamoto, Ken-Ichi

    2009-12-01

    Layered metal carboxylates [M(malonato)(H(2)O)(2)](n) (M = Ni(II) and Mn(II)) that have a claylike structure have been synthesized hydrothermally and characterized. The interlayer separation in these layered carboxylates is comparable to that of the intercalation distance of the naturally occurring clay materials or layered double hydroxides (LDHs). In this study, we have demonstrated that, instead of intercalating the metal complex into layers of the clay or LDH, layered transition metal carboxylates, [M(malonato)(H(2)O)(2)](n), as such can be used as a recyclable heterogeneous catalyst in olefin epoxidation reaction. Metal carboxylates [M(malonato)(H(2)O)(2)](n) exhibit excellent catalytic performance in olefin epoxidation reaction.

  1. Fe-modified HZSM-5 catalysts for ethanol conversion into light olefins

    Institute of Scientific and Technical Information of China (English)

    Jiangyin Lu; Yancong Liu; Na Li

    2011-01-01

    A series of Fe/HZSM-5 catalysts with different iron loadings were prepared by impregnation method.Characterization was performed by N2 adsorption-desorption,X-ray diffraction (XRD),NH3 temperature-programmed desorption (NH3-TPD),temperature-programmed reduction (TPR),temperature-programmed oxidation (TPO) and thermogravimetry (TG) analysis.Iron content in the synthesized samples varied from 1.1 wt% to 20 wt%.The obtained samples have been used for ethanol conversion into light olefins.It was found that the amount of strong acidity at 300-550 ℃ on Fe-modified samples was decreased,going with another new acid site appearance at 550-600 ℃ and that Fe/HZSM-5 catalysts were highly selective towards light olefins,especially the 9FZ sample.In addition,Fe-modified catalysts suppressed the conversion of ethanol to aromatics and paraffins and enhanced their anti-carbon deposit ability.

  2. The activation mechanism of Ru-indenylidene complexes in olefin metathesis

    KAUST Repository

    Urbina-Blanco, César A.

    2013-05-08

    Olefin metathesis is a powerful tool for the formation of carbon-carbon double bonds. Several families of well-defined ruthenium (Ru) catalysts have been developed during the past 20 years; however, the reaction mechanism for all such complexes was assumed to be the same. In the present study, the initiation mechanism of Ru-indenylidene complexes was examined and compared with that of benzylidene counterparts. It was discovered that not all indenylidene complexes followed the same mechanism, highlighting the importance of steric and electronic properties of so-called spectator ligands, and that there is no single mechanism for the Ru-based olefin metathesis reaction. The experimental findings are supported quantitatively by DFT calculations. © 2013 American Chemical Society.

  3. Functionalized olefin cross-coupling to construct carbon-carbon bonds

    Science.gov (United States)

    Lo, Julian C.; Gui, Jinghan; Yabe, Yuki; Pan, Chung-Mao; Baran, Phil S.

    2014-12-01

    Carbon-carbon (C-C) bonds form the backbone of many important molecules, including polymers, dyes and pharmaceutical agents. The development of new methods to create these essential connections in a rapid and practical fashion has been the focus of numerous organic chemists. This endeavour relies heavily on the ability to form C-C bonds in the presence of sensitive functional groups and congested structural environments. Here we report a chemical transformation that allows the facile construction of highly substituted and uniquely functionalized C-C bonds. Using a simple iron catalyst, an inexpensive silane and a benign solvent under ambient atmosphere, heteroatom-substituted olefins are easily reacted with electron-deficient olefins to create molecular architectures that were previously difficult or impossible to access. More than 60 examples are presented with a wide array of substrates, demonstrating the chemoselectivity and mildness of this simple reaction.

  4. Synthesis of amide-functionalized cellulose esters by olefin cross-metathesis.

    Science.gov (United States)

    Meng, Xiangtao; Edgar, Kevin J

    2015-11-05

    Cellulose esters with amide functionalities were synthesized by cross-metathesis (CM) reaction of terminally olefinic esters with different acrylamides, catalyzed by Hoveyda-Grubbs 2nd generation catalyst. Chelation by amides of the catalyst ruthenium center caused low conversions using conventional solvents. The effects of both solvent and structure of acrylamide on reaction conversion were investigated. While the inherent tendency of acrylamides to chelate Ru is governed by the acrylamide N-substituents, employing acetic acid as a solvent significantly improved the conversion of certain acrylamides, from 50% to up to 99%. Homogeneous hydrogenation using p-toluenesulfonyl hydrazide successfully eliminated the α,β-unsaturation of the CM products to give stable amide-functionalized cellulose esters. The amide-functionalized product showed higher Tg than its starting terminally olefinic counterpart, which may have resulted from strong hydrogen bonding interactions of the amide functional groups.

  5. Nitro-Grela-type complexes containing iodides – robust and selective catalysts for olefin metathesis under challenging conditions

    Directory of Open Access Journals (Sweden)

    Andrzej Tracz

    2015-10-01

    Full Text Available Iodide-containing nitro-Grela-type catalysts have been synthesized and applied to ring closing metathesis (RCM and cross metathesis (CM reactions. These new catalysts have exhibited improved efficiency in the transformation of sterically, non-demanding alkenes. Additional steric hindrance in the vicinity of ruthenium related to the presence of iodides ensures enhanced catalyst stability. The benefits are most apparent under challenging conditions, such as very low reaction concentrations, protic solvents or with the occurrence of impurities.

  6. Nitro-Grela-type complexes containing iodides – robust and selective catalysts for olefin metathesis under challenging conditions

    Science.gov (United States)

    Tracz, Andrzej; Matczak, Mateusz; Urbaniak, Katarzyna

    2015-01-01

    Summary Iodide-containing nitro-Grela-type catalysts have been synthesized and applied to ring closing metathesis (RCM) and cross metathesis (CM) reactions. These new catalysts have exhibited improved efficiency in the transformation of sterically, non-demanding alkenes. Additional steric hindrance in the vicinity of ruthenium related to the presence of iodides ensures enhanced catalyst stability. The benefits are most apparent under challenging conditions, such as very low reaction concentrations, protic solvents or with the occurrence of impurities. PMID:26664602

  7. Nitro-Grela-type complexes containing iodides - robust and selective catalysts for olefin metathesis under challenging conditions.

    Science.gov (United States)

    Tracz, Andrzej; Matczak, Mateusz; Urbaniak, Katarzyna; Skowerski, Krzysztof

    2015-01-01

    Iodide-containing nitro-Grela-type catalysts have been synthesized and applied to ring closing metathesis (RCM) and cross metathesis (CM) reactions. These new catalysts have exhibited improved efficiency in the transformation of sterically, non-demanding alkenes. Additional steric hindrance in the vicinity of ruthenium related to the presence of iodides ensures enhanced catalyst stability. The benefits are most apparent under challenging conditions, such as very low reaction concentrations, protic solvents or with the occurrence of impurities.

  8. The olefin metathesis reaction: reorganization and cyclization of organic compounds; A reacao de metatese de olefinas: reorganizacao e ciclizacao de compostos organicos

    Energy Technology Data Exchange (ETDEWEB)

    Frederico, Daniel; Brocksom, Ursula; Brocksom, Timothy John [Sao Carlos Univ., SP (Brazil). Dept. de Quimica]. E-mail: brocksom@terra.com.br

    2005-07-15

    The olefin metathesis reaction allows the exchange of complex alkyl units between two olefins, with the formation of a new olefinic link and a sub-product olefin usually ethylene. This reaction has found extensive application in the last ten years with the development of the Grubbs and Schrock catalysts, in total synthesis of complex organic molecules, as opposed to the very important use in the petrochemical industry with relatively simple molecules. This review intends to trace a historical and mechanistic pathway from industry to academy, before illustrating the more recent advances. (author)

  9. Amphiphilic Cellulose Ethers Designed for Amorphous Solid Dispersion via Olefin Cross-Metathesis.

    Science.gov (United States)

    Dong, Yifan; Mosquera-Giraldo, Laura I; Taylor, Lynne S; Edgar, Kevin J

    2016-02-01

    The design of cellulose ether-based amphiphiles has been difficult and limited because of the harsh conditions typically required for appending ether moieties to cellulose. Olefin cross-metathesis recently has been shown to be a valuable approach for appending a variety of functional groups to cellulose ethers and esters, provided that an olefin handle for metathesis can be attached. This synthetic pathway gives access to these functional derivatives under very mild conditions and at high efficiency. Modification of ethyl cellulose by metathesis to prepare useful derivatives, for example, for solubility and bioavailability enhancement of drugs by amorphous solid dispersion (ASD), has been limited by the low DS(OH) of commercial ethyl cellulose derivatives. This is problematic because ethyl cellulose is otherwise a very attractive substrate for synthesis of amphiphilic derivatives by olefin metathesis. Herein we explore two methods for opening up this design space for ether-based amphiphiles, for example, permitting synthesis of more hydrophilic derivatives. One approach is to start with the more hydrophilic commercial methyl cellulose, which contains much higher DS(OH) and therefore is better suited for introduction of high DS of olefin metathesis "handles". In another approach, we explored a homogeneous one-pot synthesis methodology from cellulose, where controlled DS of ethyl groups was introduced at the same time as the ω-unsaturated alkyl groups, thereby permitting complete control of DS(OH), DS(Et), and ultimately DS of the functional group added by metathesis. We describe the functionalized derivatives available by these successful approaches. In addition, we explore new methods for reduction of the unsaturation in initial metathesis products to provide robust methods for enhancing product stability against further radical-catalyzed reactions. We demonstrate initial evidence that the products show strong promise as amphiphilic matrix polymers for amorphous

  10. Ruthenium indenylidene “1st generation” olefin metathesis catalysts containing triisopropyl phosphite

    Directory of Open Access Journals (Sweden)

    Stefano Guidone

    2015-09-01

    Full Text Available The reaction of triisopropyl phosphite with phosphine-based indenylidene pre-catalysts affords “1st generation” cis-complexes. These have been used in olefin metathesis reactions. The cis-Ru species exhibit noticeable differences with the trans-Ru parent complexes in terms of structure, thermal stability and reactivity. Experimental data underline the importance of synergistic effects between phosphites and L-type ligands.

  11. Ruthenium indenylidene "1(st) generation" olefin metathesis catalysts containing triisopropyl phosphite.

    Science.gov (United States)

    Guidone, Stefano; Nahra, Fady; Slawin, Alexandra M Z; Cazin, Catherine S J

    2015-01-01

    The reaction of triisopropyl phosphite with phosphine-based indenylidene pre-catalysts affords "1(st) generation" cis-complexes. These have been used in olefin metathesis reactions. The cis-Ru species exhibit noticeable differences with the trans-Ru parent complexes in terms of structure, thermal stability and reactivity. Experimental data underline the importance of synergistic effects between phosphites and L-type ligands.

  12. Ruthenium indenylidene “1st generation” olefin metathesis catalysts containing triisopropyl phosphite

    Science.gov (United States)

    Guidone, Stefano; Nahra, Fady; Slawin, Alexandra M Z

    2015-01-01

    Summary The reaction of triisopropyl phosphite with phosphine-based indenylidene pre-catalysts affords “1st generation” cis-complexes. These have been used in olefin metathesis reactions. The cis-Ru species exhibit noticeable differences with the trans-Ru parent complexes in terms of structure, thermal stability and reactivity. Experimental data underline the importance of synergistic effects between phosphites and L-type ligands. PMID:26425210

  13. Improving olefin tolerance and production in E. coli using native and evolved AcrB.

    Science.gov (United States)

    Mingardon, Florence; Clement, Camille; Hirano, Kathleen; Nhan, Melissa; Luning, Eric G; Chanal, Angelique; Mukhopadhyay, Aindrila

    2015-05-01

    Microorganisms can be engineered for the production of chemicals utilized in the polymer industry. However many such target compounds inhibit microbial growth and might correspondingly limit production levels. Here, we focus on compounds that are precursors to bioplastics, specifically styrene and representative alpha-olefins; 1-hexene, 1-octene, and 1-nonene. We evaluated the role of the Escherichia coli efflux pump, AcrAB-TolC, in enhancing tolerance towards these olefin compounds. AcrAB-TolC is involved in the tolerance towards all four compounds in E. coli. Both styrene and 1-hexene are highly toxic to E. coli. Styrene is a model plastics precursor with an established route for production in E. coli (McKenna and Nielsen, 2011). Though our data indicates that AcrAB-TolC is important for its optimal production, we observed a strong negative selection against the production of styrene in E. coli. Thus we used 1-hexene as a model compound to implement a directed evolution strategy to further improve the tolerance phenotype towards this alpha-olefin. We focused on optimization of AcrB, the inner membrane domain known to be responsible for substrate binding, and found several mutations (A279T, Q584R, F617L, L822P, F927S, and F1033Y) that resulted in improved tolerance. Several of these mutations could also be combined in a synergistic manner. Our study shows efflux pumps to be an important mechanism in host engineering for olefins, and one that can be further improved using strategies such as directed evolution, to increase tolerance and potentially production.

  14. SYNTHESIS OF POLYSILOXANE-SUPPORTED SELENAETHER PLATINUM COMPLEX AND ITS CATALYTIC PROPERTY FOR HYDROSILYLATION OF OLEFINS

    Institute of Scientific and Technical Information of China (English)

    LU Xueran; CHEN Zhen; DUAN Heping; CHEN Yifan

    1996-01-01

    A new type of selenious polymer, silica-bound polybispropoxyethyl-selenidesilsesquioxane,and its platinum complex were synthesized from bis-allyloxyethyl selenide via hydrosilylation with triethoxysilane, followed by immobilized on fumed silica, and then reacting with potassium chloroplatinite under nitrogen atmosphere in acetone. It was found that the platinum complex can catalyze the hydrosilylation of olefins with triethoxysilane effectively. The effects of the nature of the substrate, the amount of complex used, and the reaction temperature on the catalytic activity were investigated.

  15. Modular construction of a porous organometallic network based on rhodium olefin complexation.

    Science.gov (United States)

    Stoeck, Ulrich; Nickerl, Georg; Burkhardt, Ulrich; Senkovska, Irena; Kaskel, Stefan

    2012-10-24

    We describe the rational design and synthesis of the first member of a new class of microporous materials. It is built from rhodium and a polyolefinic ligand featuring a rigid tetraphenylsilane backbone via metal olefin complexation, creating a truly organometallic network. The resulting framework, denoted as DUT-37 (Dresden University of Technology no. 37) exhibits considerable porosity and unprecedented stability under ambient conditions. Furthermore, it is catalytically active in transfer hydrogenation.

  16. Effect of Heteroatom Concentration in SSZ-13 on the Methanol-to-Olefins Reaction

    OpenAIRE

    Deimund, Mark A.; Harrison, Luke; Lunn, Jonathan D.; Liu, Yu; Malek, Andrzej; Shayib, Ramzy; Davis, Mark E.

    2016-01-01

    SSZ-13 materials have been synthesized with varying amounts of Al to produce samples with different concentrations of Brønsted acid sites, and consequently, these SSZ-13 materials contain increasing numbers of paired Al heteroatoms with increasing Al content. These materials were then characterized and tested as catalysts for the methanol-to-olefins (MTO) reaction at 400 °C and 100% methanol conversion under atmospheric pressure. A SAPO-34 sample was also synthesized and tested for comparison...

  17. Photoredox-Catalyzed Ketyl–Olefin Coupling for the Synthesis of Substituted Chromanols

    KAUST Repository

    Fava, Eleonora

    2016-07-21

    A visible light photoredox-catalyzed aldehyde olefin cyclization is reported. The method represents a formal hydroacylation of alkenes and alkynes and provides chromanol derivatives in good yields. The protocol takes advantage of the double role played by trialkylamines (NR3) which act as (i) electron donors for reducing the catalyst and (ii) proton donors to activate the substrate via a proton-coupled electron transfer. © 2016 American Chemical Society.

  18. Design and synthesis of ruthenium indenylidene-based catalysts for olefin metathesis

    OpenAIRE

    Urbina-Blanco, César A

    2013-01-01

    As part of a European wide effort to develop metathesis catalysts for use in fine chemical and pharmaceutical compound synthesis, this study focuses on the design and synthesis of ruthenium based catalysts for olefin metathesis. The aim, of this work was simple: to develop new, more active, more stable, easy to synthesise and commercially viable Ruthenium based catalysts, as well trying to rationalize the effect of structural changes on reactivity. Two different approaches w...

  19. Preliminary Study on Reducing Olefin Content of FCC Gasoline over Cracking Catalyst

    Institute of Scientific and Technical Information of China (English)

    梁咏梅; 杨海峰; 刘耀芳; 徐春明

    2003-01-01

    Using fixed bed micro-reactor and cracking catalyst, re-cracking of fluid catalytic cracking (FCC) gasoline at lower temperature than conventional cracking condition has been studied. The results reveal that at lower temperature from 350℃-450℃ and catalyst to feed ratio of 3, the olefin content is reduced from 49% to 27%(by mass) over the catalyst whose micro-reacting activation index is 53, and the octane number is kept on high level.

  20. Photoredox-Catalyzed Ketyl–Olefin Coupling for the Synthesis of Substituted Chromanols

    Science.gov (United States)

    2016-01-01

    A visible light photoredox-catalyzed aldehyde olefin cyclization is reported. The method represents a formal hydroacylation of alkenes and alkynes and provides chromanol derivatives in good yields. The protocol takes advantage of the double role played by trialkylamines (NR3) which act as (i) electron donors for reducing the catalyst and (ii) proton donors to activate the substrate via a proton-coupled electron transfer. PMID:27442851

  1. Split feed injection: Another tool for increasing FCC light olefin yields and gasoline octanes

    Energy Technology Data Exchange (ETDEWEB)

    Krishna, A.S. (Chevron U.S.A., El Segundo, CA (United States)); Skocpol, R.C. (Chevron Research and Technology Co., Richmond, CA (United States)); English, A.R. (Chevron U.S.A., Philadelphia, PA (United States)); Sadeghbeigi, R. (BP Oil Co., Houston, TX (United States))

    1994-01-01

    Split Feed Injection (SFI) is Chevron's patented technology for increasing the flexibility of fluid catalytic cracking units. The process improvement, which requires a relatively simple, low-cost hardware modification, results in conversion of a portion of the gasoline into lighter products (primarily olefins), and higher gasoline research and motor octanes. The technology has been extensively tested in Chevron Research Technology Company's pilot plants, and in two commercial FCC units; additional commercial tests are planned.

  2. Asymmetric cyclopropanation of chalcones using chiral phase-transfer catalysts

    OpenAIRE

    2013-01-01

    The first phase-transfer catalyzed cyclopropanation reaction of chalcones using bromomalonates as the nucleophiles in a Michael Initiated Ring Closing reaction (MIRC) was developed. Key to success was the use of a free OH-containing cinchona alkaloid ammonium salt catalyst and carefully optimized liquid/liquid reaction conditions. The reaction performed well for electron neutral and electron deficient chalcones giving the products in yields up to 98% and with enantiomeric ratios up to 91:9.

  3. Surface functionalization of cyclic olefin copolymer (COC) with evaporated TiO{sub 2} thin film

    Energy Technology Data Exchange (ETDEWEB)

    El Fissi, Lamia, E-mail: lamia.elfissi@uclouvain.be [ICTEAM Institute, Université catholique du Louvain, place de Levant 3, 1348 Louvain-la-Neuve (Belgium); Vandormael, Denis [SIRRIS Liege Science Park, 4102 Seraing (Belgium); Houssiau, Laurent [Research Centre in Physics of Matter and Radiation (PMR), University of Namur, Rue de Bruxelles 61, B-5000 Namur (Belgium); Francis, Laurent A. [ICTEAM Institute, Université catholique du Louvain, place de Levant 3, 1348 Louvain-la-Neuve (Belgium)

    2016-02-15

    Highlights: • TiO{sub 2}/COC (cyclic olefin copolymer) hybrid material for BioMEMS applications. • Thin layer of TiO{sub 2} was deposed on cyclic olefin copolymer using physical vapor deposition (PVD) technique. • The coating possess the highest level of adhesion with an excellent morphology of the hybrid material (TiO{sub 2}/COC). - Abstract: Cyclic olefin copolymer (COC) is a new class of thermoplastic polymers used for a variety of applications ranging from bio-sensing to optics. However, the hydrophobicity of native COC hampers the further development and application of this material [1]. In this work, we report the structural, morphological, and optical properties of the TiO{sub 2}/COC hybrid material, which provides a desirable substrate for optical devices and subsequent surface modifications. The TiO{sub 2} film on COC substrate was deposited by the evaporation method, and it was characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), profilometry and atomic force microscope (AFM). Using an UV-vis spectrophotometer, we found that the transmittance of the TiO{sub 2}/COC hybrid material in the visible domain reached 80%. The TiO{sub 2}/COC hybrid appeared to be stable in most of the assessed polar solvents and acid/basic solutions. The new TiO{sub 2}/COC hybrid material and the robust fabrication method are expected to enable a variety of BioMEMS applications.

  4. Microchannel fabrication on cyclic olefin polymer substrates via 1064 nm Nd:YAG laser ablation

    Science.gov (United States)

    McCann, Ronán; Bagga, Komal; Groarke, Robert; Stalcup, Apryll; Vázquez, Mercedes; Brabazon, Dermot

    2016-11-01

    This paper presents a method for fabrication of microchannels on cyclic olefin polymer films that have application in the field of microfluidics and chemical sensing. Continuous microchannels were fabricated on 188-μm-thick cyclic olefin polymer substrates using a picosecond pulsed 1064 nm Nd:YAG laser. The effect of laser fluence on the microchannel morphology and dimensions was analysed via scanning electron microscopy and optical profilometry. Single laser passes were found to produce v-shaped microchannels with depths ranging from 12 μm to 47 μm and widths from 44 μm to 154 μm. The ablation rate during processing was lower than predicted theoretically. Multiple laser passes were applied to examine the ability for finer control over microchannel morphology with channel depths ranging from 22 μm to 77 μm and channel widths from 59 μm to 155 μm. For up to five repeat passes, acceptable reproducibility was found in the produced microchannel morphology. Infrared spectroscopy revealed oxidation and dehydrogenation of the polymer surface following laser ablation. These results were compared to other work conducted on cyclic olefin polymers.

  5. Microporous and mesoporous ZSM-5 catalyst for catalytic cracking of C5 raffinate to light olefins.

    Science.gov (United States)

    Lee, Joongwon; Hong, Ung Gi; Hwang, Sunhwan; Youn, Min Hye; Song, In Kyu

    2014-11-01

    ZSM5 catalysts (PAM(X)-ZSM5) with micropores and mesopores were prepared using polyacrylamide (PAM) as a soft template at different PAM content (X = 0, 0.12, 0.25, 0.53, 0.64, and 0.78 wt%), and they were applied to the production of light olefins (ethylene and propylene) through catalytic cracking of C5 raffinate. The effect of PAM content of PAM(X)-ZSM5 catalysts on the physicochemical properties and catalytic activities was investigated. N2 adsorption-desorption isotherms of PAM(X)-ZSM5 catalysts exhibited a broad hysteresis loop at high relative pressure, indicating the existence of mesopores in the catalysts. It was found that the catalytic performance of PAM(X)-ZSM5 catalysts was closely related to the mesoporosity of the catalysts. Conversion of C5 raffinate and yield for light olefins showed volcano-shaped trends with respect to mesopore/micropore volume ratio of the catalysts. Thus, an optimal PAM content was required to achieve maximum production of light olefins through catalytic cracking of C5 raffinate over microporous and mesoporous PAM(X)-ZSM5 catalysts.

  6. Olefin metathesis reaction on GaN (0 0 0 1) surfaces

    Science.gov (United States)

    Makowski, Matthew S.; Zemlyanov, Dmitry Y.; Ivanisevic, Albena

    2011-03-01

    Proof-of-concept reactions were performed on GaN (0 0 0 1) surfaces to demonstrate surface termination with desired chemical groups using an olefin cross-metathesis reaction. To prepare the GaN surfaces for olefin metathesis, the surfaces were hydrogen terminated with hydrogen plasma, chlorine terminated with phosphorous pentachloride, and then terminated with an alkene group via a Grignard reaction. The olefin metathesis reaction then bound 7-bromo-1-heptene. The modified surfaces were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy, and water contact angle measurements following each step in the reaction scheme. The XPS data was used to qualitatively identify surface chemical species and to quantitatively determine molecular surface coverage. The bromine atom in 7-bromo-1-heptene served as a heteroatom for identification with XPS. The reaction scheme resulted in GaN substrates with a surface coverage of 0.10 monolayers and excellent stability towards oxidation when exposed to oxygen plasma.

  7. "Click" and Olefin Metathesis Chemistry in Water at Room Temperature Enabled by Biodegradable Micelles.

    Science.gov (United States)

    Lipshutz, Bruce H; Bošković, Zarko; Crowe, Christopher S; Davis, Victoria K; Whittemore, Hannah C; Vosburg, David A; Wenzel, Anna G

    2013-11-12

    The two laboratory reactions focus on teaching several concepts associated with green chemistry. Each uses a commercial, nontoxic, and biodegradable surfactant, TPGS-750-M, to promote organic reactions within the lipophilic cores of nanoscale micelles in water. These experiments are based on work by K. Barry Sharpless (an azide-alkyne "click" reaction) and Robert Grubbs (an olefin cross-metathesis reaction); both are suitable for an undergraduate organic laboratory. The copper-catalyzed azide-alkyne [3+2] cycloaddition of benzyl azide and 4-tolylacetylene is very rapid: the triazole product is readily isolated by filtration and is characterized by thin-layer chromatography and melting point analysis. The ruthenium-catalyzed olefin cross-metathesis reaction of benzyl acrylate with 1-hexene is readily monitored by thin-layer chromatography and gas chromatography. The metathesis experiment comparatively evaluates the efficacy of a TPGS-750-M/water medium relative to a traditional reaction performed in dichloromethane (a common solvent used for olefin metathesis).

  8. “Click” and Olefin Metathesis Chemistry in Water at Room Temperature Enabled by Biodegradable Micelles

    Science.gov (United States)

    Lipshutz, Bruce H.; Bošković, Zarko; Crowe, Christopher S.; Davis, Victoria K.; Whittemore, Hannah C.; Vosburg, David A.; Wenzel, Anna G.

    2013-01-01

    The two laboratory reactions focus on teaching several concepts associated with green chemistry. Each uses a commercial, nontoxic, and biodegradable surfactant, TPGS-750-M, to promote organic reactions within the lipophilic cores of nanoscale micelles in water. These experiments are based on work by K. Barry Sharpless (an azide–alkyne “click” reaction) and Robert Grubbs (an olefin cross-metathesis reaction); both are suitable for an undergraduate organic laboratory. The copper-catalyzed azide–alkyne [3+2] cycloaddition of benzyl azide and 4-tolylacetylene is very rapid: the triazole product is readily isolated by filtration and is characterized by thin-layer chromatography and melting point analysis. The ruthenium-catalyzed olefin cross-metathesis reaction of benzyl acrylate with 1-hexene is readily monitored by thin-layer chromatography and gas chromatography. The metathesis experiment comparatively evaluates the efficacy of a TPGS-750-M/water medium relative to a traditional reaction performed in dichloromethane (a common solvent used for olefin metathesis). PMID:24324282

  9. Cyclopentadienyl-containing low-valent early transition metal olefin polymerization catalysts

    Science.gov (United States)

    Marks, Tobin J.; Luo, Lubin; Yoon, Sung Cheol

    2003-12-30

    A catalyst system useful to polymerize and co-polymerize polar and non-polar olefin monomers is formed by in situ reduction with a reducing agent of a catalyst precursor comprising wherein Cp* is a cyclopentadienyl or substituted cyclopentadienyl moiety; M is an early transition metal; R is a C.sub.1 -C.sub.20 hydrocarbyl; R' are independently selected from hydride, C.sub.1 -C.sub.20 hydrocarbyl, SiR".sub.3, NR".sub.2, OR", SR", GeR".sub.3, SnR".sub.3, and C.dbd.C containing groups (R".dbd.C.sub.1 -C.sub.10 hydrocarbyl); n is an integer selected to balance the oxidation state of M; and A is a suitable non-coordinating anionic cocatalyst or precursor. This catalyst system may form stereoregular olefin polymers including syndiotactic polymers of styrene and methylmethacrylate and isotactic copolymers of polar and nonpolar olefin monomers such as methylmethacrylate and styrene.

  10. Effects of Anions and Cations on π-Complexation Between Olefin and Metal Halide

    Institute of Scientific and Technical Information of China (English)

    ZHOU Jin-xia; ZHANG Yong-chun; GUO Xin-wen

    2005-01-01

    An ab initio molecular orbital study was performed to determine the effects of anions and cations on the π-complexation of C2H4 on MX(M=Ag, Cu; X=F, Cl). The calculated results show the following order of adsorption strength: F->Cl- for anions; Cu+>Ag+ for cations. The results can be explained by the detailed analysis of atomic charge, orbital energy and orbital population by using the natural bond orbital(NBO) theory: (1) anions with stronger electronegativity can attract more electrons from the s orbital of M, while at the same time it does not obviously weaken the d orbital occupation of M, thus the nearly vacant s orbital and the sufficiently filled d orbitals of M help with forming σ-donation and d-π* backdonation with the π orbital and the π* orbital of olefin, respectively; (2) a smaller energy gap of symmetry-adapted orbitals between olefin and a cation can favor the electron transfer, that is why Cu+ forms stronger adsorption with olefin than Ag+does.

  11. LDRD final report on new homogeneous catalysts for direct olefin epoxidation (LDRD 52591).

    Energy Technology Data Exchange (ETDEWEB)

    Goldberg, Karen (University of Washington); Smythe, Nicole A. (University of Washington); Moore, Joshua T.; Stewart, Constantine A.; Kemp, Richard Alan; Miller, James Edward; Kornienko, Alexander (New Mexico Institute of Mining and Technology); Denney, Melanie C. (University of Washington); Cetto, Kara L. (University of Washington)

    2006-02-01

    This report summarizes our findings during the study of a novel homogeneous epoxidation catalyst system that uses molecular oxygen as the oxidant, a ''Holy Grail'' in catalysis. While olefins (alkenes) that do not contain allylic hydrogens can be epoxidized directly using heterogeneous catalysts, most olefins cannot, and so a general, atom-efficient route is desired. While most of the work performed on this LDRD has been on pincer complexes of late transition metals, we also scouted out metal/ligand combinations that were significantly different, and unfortunately, less successful. Most of the work reported here deals with phosphorus-ligated Pd hydrides [(PCP)Pd-H]. We have demonstrated that molecular oxygen gas can insert into the Pd-H bond, giving a structurally characterized Pd-OOH species. This species reacts with oxygen acceptors such as olefins to donate an oxygen atom, although in various levels of selectivity, and to generate a [(PCP)Pd-OH] molecule. We discovered that the active [(PCP)Pd-H] active catalyst can be regenerated by addition of either CO or hydrogen. The demonstration of each step of the catalytic cycle is quite significant. Extensions to the pincer-Pd chemistry by attaching a fluorinated tail to the pincer designed to be used in solvents with higher oxygen solubilities are also presented.

  12. Wood-derived olefins by steam cracking of hydrodeoxygenated tall oils.

    Science.gov (United States)

    Pyl, Steven P; Dijkmans, Thomas; Antonykutty, Jinto M; Reyniers, Marie-Françoise; Harlin, Ali; Van Geem, Kevin M; Marin, Guy B

    2012-12-01

    Tall oil fractions obtained from Norwegian spruce pulping were hydrodeoxygenated (HDO) at pilot scale using a commercial NiMo hydrotreating catalyst. Comprehensive two dimensional gas chromatography (GC×GC) showed that HDO of both tall oil fatty acids (TOFA) and distilled tall oil (DTO) produced highly paraffinic hydrocarbon liquids. The hydrotreated fractions also contained fatty acid methyl esters and norabietane and norabietatriene isomers. Steam cracking of HDO-TOFA in a pilot plant revealed that high light olefin yields can be obtained, with 35.4 wt.% of ethene and 18.2 wt.% of propene at a coil outlet pressure (COP) of 1.7 bara, a dilution of 0.45 kg(steam)/kg(HDO-TOFA) and a coil outlet temperature (COT) of 820 °C. A pilot plant coking experiment indicated that cracking of HDO-TOFA at a COT of 850 °C results in limited fouling in the reactor. Co-cracking of HDO tall oil fractions with a typical fossil-based naphtha showed improved selectivity to desired light olefins, further demonstrating the potential of large scale olefin production from hydrotreated tall oil fractions in conventional crackers.

  13. A free energy approach to the prediction of olefin and epoxide mutagenicity and carcinogenicity.

    Science.gov (United States)

    Kostal, Jakub; Voutchkova-Kostal, Adelina; Weeks, Brian; Zimmerman, Julie B; Anastas, Paul T

    2012-12-17

    The mutagenic and carcinogenic effects of strong alkylating agents, such as epoxides, have been attributed to their ability to covalently bind DNA in vivo. Most olefins are readily oxidized to reactive epoxides by CytP450. In an effort to develop predictive models for olefin and epoxide mutagenicity, the ring openings of 15 halogen-, alkyl-, alkenyl-, and aryl-substituted epoxides were modeled by quantum-mechanical transition state calculations using MP2/6-31+G(d,p) in the gas phase and in aqueous solution. Free energies of activation (ΔG(‡)) and free energies of reaction (ΔG(rxn)) were computed for each epoxide in the series. This study finds that an aqueous solution ΔG(rxn) threshold value of approximately -14.7 kcal/mol can be used to discern mutagenic/carcinogenic epoxides (ΔG(rxn) -14.7 kcal/mol). The computed reaction thermodynamics are appropriate regardless of ring-opening mechanism in vivo and are thus proposed as an effective in silico screen and design guideline for decreasing potential mutagenicity and carcinogenicity of olefins and their respective epoxides.

  14. Energy and materials flows in the production of olefins and their derivatives

    Energy Technology Data Exchange (ETDEWEB)

    Gaines, L.L.; Shen, S.Y.

    1980-08-01

    Production of olefins and their derivatives uses almost 3.5% of the oil and gas consumed annually in the United States. It is estimated that their production requires an input energy of 2 Q, which is 50% of the energy used in the production of all petrochemicals. Substantial amounts of this energy could be recovered through recycling. For example, recycling of a single plastic product, polyester soft drink bottles, could have recovered about 0.014 Q in 1979. (About 1.4 Q is used to produce plastic derivatives of olefins). Petrochemical processes use fuels as feedstocks, as well as for process energy, and a portion of this energy is not foregone and can be recovered through combustion of the products. The energy foregone in the production of ethylene is estimated to be 7800 Btu/lb. The energy foregone in plastics production ranges from 12,100 Btu/lb for the new linear low-density polyethylene to 77,200 Btu/lb for nylon 66, which is about 60% of the total energy input for that product. Further investigation of the following areas could yield both material and energy savings in the olefins industry: (1) recycling of petrochemical products to recover energy in addition to that recoverable through combustion, (2) impact of feedstock substitution on utilization of available national resources, and (3) effective use of the heat embodied in process steam. This steam accounts for a major fraction of the industry's energy input.

  15. Olefin metathesis. 8. Active sites on Re/sub 2/O/sub 7//Al/sub 2/O/sub 3/ catalysts for the metathesis of olefins

    Energy Technology Data Exchange (ETDEWEB)

    Nakamura, R.; Ichikawa, K.; Echigoya, E.

    1978-01-01

    Disproportionation of propylene, 1-hexene, and 2-pentene was tested at 20/sup 0/-50/sup 0/C on rhenium oxide/alumina catalysts having 1:99 to 7:93 rhenium/aluminum atomic ratios. The catalysts were prepared and pretreated in various ways, including pretreatment with water. Comparisons of the activities with ESR and X-ray diffraction data showed that in catalysts containing < 1% rhenium (''K region''), the rhenium(VII) was strongly bonded in a distorted alumina lattice and inactive; that in catalysts containing 1-3% rhenium (''L region''), the rhenium formed Re-O-Al bonds in which the rhenium had some activity; and that in the very active catalysts with > 3% rhenium (''M region''), the rhenium formed Re-O-Re species which were weakly bonded and easily converted to an active species by reduction and complex formation with the olefin. The rhenium(VII) ions around the active center increased its positive charge and thus promoted the olefin adsorption. Catalysts containing 0.5% rhenium (K region) could be transformed into L or M region catalysts by addition of a metal ion of high electronegativity, such as tungsten or vanadium. Graphs, spectra, and 19 references.

  16. Asymmetric stem cell division: lessons from Drosophila.

    Science.gov (United States)

    Wu, Pao-Shu; Egger, Boris; Brand, Andrea H

    2008-06-01

    Asymmetric cell division is an important and conserved strategy in the generation of cellular diversity during animal development. Many of our insights into the underlying mechanisms of asymmetric cell division have been gained from Drosophila, including the establishment of polarity, orientation of mitotic spindles and segregation of cell fate determinants. Recent studies are also beginning to reveal the connection between the misregulation of asymmetric cell division and cancer. What we are learning from Drosophila as a model system has implication both for stem cell biology and also cancer research.

  17. On-chip asymmetric microcavity optomechanics.

    Science.gov (United States)

    Soltani, Soheil; Hudnut, Alexa W; Armani, Andrea M

    2016-12-26

    High quality factor (Q) optical resonators have enabled rapid growth in the field of cavity-enhanced, radiation pressure-induced optomechanics. However, because research has focused on axisymmetric devices, the observed regenerative excited mechanical modes are similar. In the present work, a strategy for fabricating high-Q whispering gallery mode microcavities with varying degrees of asymmetry is developed and demonstrated. Due to the combination of high optical Q and asymmetric device design, two previously unobserved modes, the asymmetric cantilever and asymmetric crown mode, are demonstrated with sub-mW thresholds for onset of oscillations. The experimental results are in good agreement with computational modeling predictions.

  18. Regenerating a symmetry in asymmetric dark matter.

    Science.gov (United States)

    Buckley, Matthew R; Profumo, Stefano

    2012-01-06

    Asymmetric dark matter theories generically allow for mass terms that lead to particle-antiparticle mixing. Over the age of the Universe, dark matter can thus oscillate from a purely asymmetric configuration into a symmetric mix of particles and antiparticles, allowing for pair-annihilation processes. Additionally, requiring efficient depletion of the primordial thermal (symmetric) component generically entails large annihilation rates. We show that unless some symmetry completely forbids dark matter particle-antiparticle mixing, asymmetric dark matter is effectively ruled out for a large range of masses, for almost any oscillation time scale shorter than the age of the Universe.

  19. Absolute Asymmetric Synthesis Using A Cocrystal Approach

    Institute of Scientific and Technical Information of China (English)

    H.Koshima

    2007-01-01

    1 Results Absolute asymmetric synthesis by means of solid-state reaction of chiral crystals self-assembled from achiral molecules is an attractive and promising methodology for asymmetric synthesis because it is not necessary to employ any external chiral source like a chiral catalyst.In order to design reliably absolute asymmetric syntheses in the solid state,it is inevitable to prepare and predict the formation of chiral crystals from achiral compounds.We have prepared a number of chiral cocrystals co...

  20. Asymmetric dark matter in braneworld cosmology

    Energy Technology Data Exchange (ETDEWEB)

    Meehan, Michael T.; Whittingham, Ian B., E-mail: Michael.Meehan@my.jcu.edu.au, E-mail: Ian.Whittingham@jcu.edu.au [School of Engineering and Physical Sciences, James Cook University, Townsville, 4811 Australia (Australia)

    2014-06-01

    We investigate the effect of a braneworld expansion era on the relic density of asymmetric dark matter. We find that the enhanced expansion rate in the early universe predicted by the Randall-Sundrum II (RSII) model leads to earlier particle freeze-out and an enhanced relic density. This effect has been observed previously by Okada and Seto (2004) for symmetric dark matter models and here we extend their results to the case of asymmetric dark matter. We also discuss the enhanced asymmetric annihilation rate in the braneworld scenario and its implications for indirect detection experiments.

  1. Enantiopure sulfoxides: recent applications in asymmetric synthesis.

    Science.gov (United States)

    Carreño, M Carmen; Hernández-Torres, Gloria; Ribagorda, María; Urbano, Antonio

    2009-11-07

    Sulfoxides are nowadays recognised as powerful chiral auxiliaries that may participate in a wide range of asymmetric reactions. Their high configurational stability, the existence of several efficient methods allowing the access to both configurations as well as their synthetic versatility are characteristic features offering a tremendous potential to develop new applications. Significant recent advances leading to high asymmetric inductions in carbon-carbon and carbon-oxygen bond forming reactions, and applications of homochiral sulfoxides to atroposelective synthesis and asymmetric catalysis are discussed. New uses of sulfoxides in the design of chiroptical switches are also shown.

  2. Multinuclear group 4 catalysis: olefin polymerization pathways modified by strong metal-metal cooperative effects.

    Science.gov (United States)

    McInnis, Jennifer P; Delferro, Massimiliano; Marks, Tobin J

    2014-08-19

    Polyolefins are produced today catalytically on a vast scale, and the manufactured polymers find use in everything from artificial limbs and food/medical packaging to automotive and electrical components and lubricants. Although polyolefin monomers are typically cheap (e.g., ethylene, propylene, α-olefins), the resulting polymer properties can be dramatically tuned by the particular polymerization catalyst employed, and reflect a rich interplay of macromolecular chemistry, materials science, and physics. For example, linear low-density polyethylene (LLDPE), produced by copolymerization of ethylene with linear α-olefin comonomers such as 1-butene, 1-hexene, or 1-octene, has small but significant levels of short alkyl branches (C2, C4, C6) along the polyethylene backbone, and is an important technology material due to outstanding rheological and mechanical properties. In 2013, the total world polyolefin production was approximately 211 million metric tons, of which about 11% was LLDPE. Historically, polyolefins were produced using ill-defined but highly active heterogeneous catalysts composed of supported groups 4 or 6 species (usually halides) activated by aluminum alkyls. In 1963, Karl Ziegler and Giulio Natta received the Nobel Prize for these discoveries. Beginning in the late 1980s, a new generation of group 4 molecule-based homogeneous olefin polymerization catalysts emerged from discoveries by Walter Kaminsky, a team led by James Stevens at The Dow Chemical Company, this Laboratory at Northwestern University, and a host of talented groups in Germany, Italy, Japan, the United Kingdom, and the United States. These new "single-site" catalysts and their activating cocatalysts were far better defined and more rationally tunable in terms of structure, mechanism, thermodynamics, and catalyst activity and selectivity than ever before possible. An explosion of research advances led to new catalysts, cocatalysts, deeper mechanistic understanding of both the

  3. Asymmetric dark matter bound state

    Science.gov (United States)

    Bi, Xiao-Jun; Kang, Zhaofeng; Ko, P.; Li, Jinmian; Li, Tianjun

    2017-02-01

    We propose an interesting framework for asymmetric scalar dark matter (ADM), which has novel collider phenomenology in terms of an unstable ADM bound state (ADMonium) produced via Higgs portals. ADMonium is a natural consequence of the basic features of ADM: the (complex scalar) ADM is charged under a dark local U (1 )d symmetry which is broken at a low scale and provides a light gauge boson X . The dark gauge coupling is strong and then ADM can annihilate away into X -pair effectively. Therefore, the ADM can form a bound state due to its large self-interaction via X mediation. To explore the collider signature of ADMonium, we propose that ADM has a two-Higgs doublet portal. The ADMonium can have a sizable mixing with the heavier Higgs boson, which admits a large cross section of ADMonium production associated with b b ¯. The resulting signature at the LHC depends on the decays of X . In this paper we consider a case of particular interest: p p →b b ¯ +ADMonium followed by ADMonium→2 X →2 e+e- where the electrons are identified as (un)converted photons. It may provide a competitive explanation to heavy di-photon resonance searches at the LHC.

  4. Twin Higgs Asymmetric Dark Matter.

    Science.gov (United States)

    García García, Isabel; Lasenby, Robert; March-Russell, John

    2015-09-18

    We study asymmetric dark matter (ADM) in the context of the minimal (fraternal) twin Higgs solution to the little hierarchy problem, with a twin sector with gauged SU(3)^{'}×SU(2)^{'}, a twin Higgs doublet, and only third-generation twin fermions. Naturalness requires the QCD^{'} scale Λ_{QCD}^{'}≃0.5-20  GeV, and that t^{'} is heavy. We focus on the light b^{'} quark regime, m_{b^{'}}≲Λ_{QCD}^{'}, where QCD^{'} is characterized by a single scale Λ_{QCD}^{'} with no light pions. A twin baryon number asymmetry leads to a successful dark matter (DM) candidate: the spin-3/2 twin baryon, Δ^{'}∼b^{'}b^{'}b^{'}, with a dynamically determined mass (∼5Λ_{QCD}^{'}) in the preferred range for the DM-to-baryon ratio Ω_{DM}/Ω_{baryon}≃5. Gauging the U(1)^{'} group leads to twin atoms (Δ^{'}-τ^{'}[over ¯] bound states) that are successful ADM candidates in significant regions of parameter space, sometimes with observable changes to DM halo properties. Direct detection signatures satisfy current bounds, at times modified by dark form factors.

  5. Force on an Asymmetric Capacitor

    CERN Document Server

    Bahder, T B; Bahder, Thomas B.; Fazi, Chris

    2002-01-01

    When a high voltage (~30 kV) is applied to a capacitor whose electrodes have different physical dimensions, the capacitor experiences a net force toward the smaller electrode (Biefeld-Brown effect). We have verified this effect by building four capacitors of different shapes. The effect may have applications to vehicle propulsion and dielectric pumps. We review the history of this effect briefly through the history of patents by Thomas Townsend Brown. At present, the physical basis for the Biefeld-Brown effect is not understood. The order of magnitude of the net force on the asymmetric capacitor is estimated assuming two different mechanisms of charge conduction between its electrodes: ballistic ionic wind and ionic drift. The calculations indicate that ionic wind is at least three orders of magnitude too small to explain the magnitude of the observed force on the capacitor. The ionic drift transport assumption leads to the correct order of magnitude for the force, however, it is difficult to see how ionic dr...

  6. Asymmetric total synthesis of vindoline.

    Science.gov (United States)

    Kato, Daisuke; Sasaki, Yoshikazu; Boger, Dale L

    2010-03-24

    A concise asymmetric total synthesis of (-)-vindoline (1) is detailed based on a tandem intramolecular [4+2]/[3+2] cycloaddition cascade of a 1,3,4-oxadiazole inspired by the natural product structure, in which the tether linking the initiating dienophile and oxadiazole bears a chiral substituent that controls the facial selectivity of the initiating Diels-Alder reaction and sets absolute stereochemistry of the remaining six stereocenters in the cascade cycloadduct. This key reaction introduces three rings and four C-C bonds central to the pentacyclic ring system setting all six stereocenters and introducing essentially all the functionality found in the natural product in a single step. Implementation of the approach also required the development of a unique ring expansion reaction to provide a six-membered ring suitably functionalized for introduction of the Delta (6, 7)-double bond found in the core structure of vindoline and defined our use of a protected hydroxymethyl group as the substituent used to control the stereochemical course of the cycloaddition cascade.

  7. Striking difference between alkane and olefin metathesis using the well-defined precursor [≡Si-O-WMe5]: Indirect evidence in favour of a bifunctional catalyst W alkylidene-hydride

    KAUST Repository

    Riache, Nassima

    2015-01-01

    Metathesis of linear alkanes catalyzed by the well-defined precursor (≡Si-O-WMe5) affords a wide distribution of linear alkanes from methane up to triacontane. Olefin metathesis using the same catalyst and under the same reaction conditions gives a very striking different distribution of linear α-olefins and internal olefins. This shows that olefin and alkane metathesis processes occur via very different pathways.

  8. A novel asymmetric synthesis of cinacalcet hydrochloride

    OpenAIRE

    Arava, Veera R; Laxminarasimhulu Gorentla; Pramod K. Dubey

    2012-01-01

    A novel route to asymmetric synthesis of cinacalcet hydrochloride by the application of (R)-tert-butanesulfinamide and regioselective N-alkylation of the naphthyl ethyl sulfinamide intermediate is described.

  9. A novel asymmetric synthesis of cinacalcet hydrochloride

    Directory of Open Access Journals (Sweden)

    Veera R. Arava

    2012-08-01

    Full Text Available A novel route to asymmetric synthesis of cinacalcet hydrochloride by the application of (R-tert-butanesulfinamide and regioselective N-alkylation of the naphthyl ethyl sulfinamide intermediate is described.

  10. A novel asymmetric synthesis of cinacalcet hydrochloride

    Science.gov (United States)

    Gorentla, Laxminarasimhulu; Dubey, Pramod K

    2012-01-01

    Summary A novel route to asymmetric synthesis of cinacalcet hydrochloride by the application of (R)-tert-butanesulfinamide and regioselective N-alkylation of the naphthyl ethyl sulfinamide intermediate is described. PMID:23019473

  11. Catalytic Asymmetric Synthesis of Phosphine Boronates

    NARCIS (Netherlands)

    Hornillos, Valentin; Vila, Carlos; Otten, Edwin; Feringa, Ben L.

    2015-01-01

    The first catalytic enantioselective synthesis of ambiphilic phosphine boronate esters is presented. The asymmetric boration of ,-unsaturated phosphine oxides catalyzed by a copper bisphosphine complex affords optically active organoboronate esters that bear a vicinal phosphine oxide group in good y

  12. Asymmetric Swiss-cheese brane-worlds

    CERN Document Server

    Gergely, L A; K\\'{e}p\\'{\\i}r\\'{o}, Ibolya

    2006-01-01

    We consider Swiss-cheese brane universes embedded asymmetrically into the bulk. Neither the junction conditions between the Schwarzschild spheres and the sorrounding Friedmann brane regions with cosmological constant $\\Lambda $, nor the evolution of the scale factor are changed with respect to the symmetric case. The universe expands and decelerates forever. The asymmetry however has a drastic influence on the evolution of the cosmological fluid. Instead of the two branches of the symmetric case, in the asymmetric case four branches emerge. Moreover, the future pressure singularity arising in the symmetric case only for huge values of $\\Lambda $ becomes quite generic in the asymmetric case. Such pressure singularities emerge also when $\\Lambda=0$ is set. Then they are due entirely to the asymmetric embedding. For generic values of $\\Lambda $ we introduce a critical value of a suitably defined asymmetry parameter, which separates Swiss-cheese cosmologies with and without pressure singularities.

  13. Congenital asymmetric crying face: a case report

    Directory of Open Access Journals (Sweden)

    Semra Kara

    2011-12-01

    Full Text Available Congenital asymmetric crying face is an anomalia caused by unilateral absence or weakness of depressor anguli oris muscle The major finding of the disease is the absence or weakness in the outer and lower movement of the commissure during crying. The other expression muscles are normal and the face is symmetric at rest. The asymmetry in congenital asymmetric crying face is most evident during infancy but decreases by age. Congenital asymmetric crying face can be associated with cervicofacial, musclebone, respiratory, genitourinary and central nervous system anomalia. It is diagnosed by physical examination. This paper presents a six days old infant with Congenital asymmetric crying face and discusses the case in terms of diagnosis and disease features.

  14. Asymmetric cryptography based on wavefront sensing.

    Science.gov (United States)

    Peng, Xiang; Wei, Hengzheng; Zhang, Peng

    2006-12-15

    A system of asymmetric cryptography based on wavefront sensing (ACWS) is proposed for the first time to our knowledge. One of the most significant features of the asymmetric cryptography is that a trapdoor one-way function is required and constructed by analogy to wavefront sensing, in which the public key may be derived from optical parameters, such as the wavelength or the focal length, while the private key may be obtained from a kind of regular point array. The ciphertext is generated by the encoded wavefront and represented with an irregular array. In such an ACWS system, the encryption key is not identical to the decryption key, which is another important feature of an asymmetric cryptographic system. The processes of asymmetric encryption and decryption are formulized mathematically and demonstrated with a set of numerical experiments.

  15. Alkane production by the marine cyanobacterium Synechococcus sp. NKBG15041c possessing the α-olefin biosynthesis pathway.

    Science.gov (United States)

    Yoshino, Tomoko; Liang, Yue; Arai, Daichi; Maeda, Yoshiaki; Honda, Toru; Muto, Masaki; Kakunaka, Natsumi; Tanaka, Tsuyoshi

    2015-02-01

    The production of alkanes in a marine cyanobacterium possessing the α-olefin biosynthesis pathway was achieved by introducing an exogenous alkane biosynthesis pathway. Cyanobacterial hydrocarbons are synthesized via two separate pathways: the acyl-acyl carrier protein (ACP) reductase/aldehyde-deformylating oxygenase (AAR/ADO) pathway for the alkane biosynthesis and the α-olefin synthase (OLS) pathway for the α-olefin biosynthesis. Coexistence of these pathways has not yet been reported. In this study, the marine cyanobacterium Synechococcus sp. NKBG15041c was shown to produce α-olefins similar to those of Synechococcus sp. PCC7002 via the α-olefin biosynthesis pathway. The production of heptadecane in Synechococcus sp. NKBG15041c was achieved by expressing the AAR/ADO pathway genes from Synechococcus elongatus PCC 7942. The production yields of heptadecane in Synechococcus sp. NKBG15041c varied with the expression level of the aar and ado genes. The maximal yield of heptadecane was 4.2 ± 1.2 μg/g of dried cell weight in the transformant carrying a homologous promoter. Our results also suggested that the effective activation of ADO may be more important for the enhancement of alkane production by cyanobacteria.

  16. Maximizing light olefins production in fluid catalytic cracking (FCC) units; Maximizacao de olefinas leves em unidades de craqueamento catalitico fluido

    Energy Technology Data Exchange (ETDEWEB)

    Pimenta, Ricardo D.M.; Pinho, Andrea de Rezende [PETROBRAS, Rio de Janeiro, RJ (Brazil)

    2004-07-01

    The Fluid Catalytic Cracking (FCC) process is widely spread over the ten PETROBRAS refineries in its thirteen industrial units. The importance of the FCC process resides on its high gasoline output, being the main supplier of this important product to the system. Additionally, FCC process is the main source of light hydrocarbons in the LPG range, including light olefins. The increasing demand for ethylene, propylene and butylenes was encouraging to concentrate the research efforts on studies about alternatives for the traditional FCC process. In the present work, the proposals from main licensors (UOP, KBR, Stone and Webster) for a light-olefins-driven FCC process (Petrochemical FCC) will be compared. Furthermore, the catalytic route for light olefins production in FCC units is also described. An additive based on ZSM- 5 zeolite, which is produced following a PETROBRAS proprietary technology, is being largely applied into the catalyst inventories of all FCC units. An analysis of different scenarios was performed to estimate the maximum potential of light olefins production from the highest possible ZSM-5 additive usage. More specifically for the case of ethylene, which production is also boosted by the same type of additive, studies are being conducted with the objective of recovering it from a C2 stream using specific units to do the splitting (UPGR). The search for increasing light olefins production in the refining processes is in line with PETROBRAS strategic plan which targeted for the company a more intense activity in the Brazilian petrochemical market (author)

  17. Catalytic pyrolysis of model compounds and waste cooking oil for production of light olefins over La/ZSM-5 catalysts

    Science.gov (United States)

    Li, F. W.; Ding, S. L.; Li, L.; Gao, C.; Zhong, Z.; Wang, S. X.; Li, Z. X.

    2016-08-01

    Waste cooking oil (WCO) and its model compounds (oleic acid and methyl laurate) are catalytically pyrolyzed in a fixed-bed reactor over La modified ZSM-5 catalysts (La/ZSM-5) aiming for production of C2-C4 light olefins. The LaO content in catalysts was set at 0, 2, 6, 10 and 14 wt%. The gas and liquid products are analyzed. The La/ZSM-5 catalyst with 6% LaO showed higher selectivity to light olefins when WCO and methyl laurate were pyrolyzed, and olefin content was 26% for WCO and 21% for methyl laurate. The catalyst with 10% LaO showed high selectivity to light olefins (28.5%) when oleic acid was pyrolyzed. The liquid products from WCO and model compounds mainly contain esters and aromatic hydrocarbons. More esters were observed in liquid products from methyl laurate and WCO pyrolysis, indicating that it is more difficult to pyrolyze esters and WCO than oleic acid. The coked catalysts were analyzed by temperature-programmed oxidation. The result shows that graphite is the main component of coke. The conversion of WCO to light olefins potentially provides an alternative and sustainable route for production of the key petrochemicals.

  18. Total Syntheses of Cyanthiwigins B, F, and G

    KAUST Repository

    Enquist, John A.

    2011-07-18

    A concise and versatile approach toward the preparation of the cyanthiwigin family of cyathane natural products is described. By leveraging a unique double asymmetric catalytic alkylation procedure it is possible to quickly establish two of the most critical stereocenters of the cyanthiwigin framework with high levels of selectivity and expediency. The synthetic route additionally employs both a tandem ring-closing cross-metathesis reaction, and an aldehyde-olefin radical cyclization process, in order to rapidly arrive at the tricyclic cyathane core of the cyanthiwigin molecules. From this unifying intermediate, the preparations of cyanthiwigins B, F, and G are attained swiftly and without the need for protecting groups.

  19. DOES VOLATILITY RESPOND ASYMMETRIC TO PAST SHOCKS?

    OpenAIRE

    Claudiu Botoc

    2014-01-01

    The main aim of the paper is to examine if the stock market volatility exhibits asymmetric or an asymmetric response to past shocks, for certain CEE countries (Romania,Hungary, Bulgaria, Poland) over the period May 2004 - September 2014. For the stock marketsfrom East Europe the results are in line with the symmetric volatility, i.e. volatility is similaraffected by both positive and negative returns with the same magnitude. For the stock marketsfrom Central Europe the results are consistent ...

  20. Systematic variation of the sodium/sulfur promoter content on carbon-supported iron catalysts for the Fischer-Tropsch to olefins reaction

    NARCIS (Netherlands)

    Oschatz, M.; Krans, N.A.; Xie, J.; de Jong, K.P.

    2016-01-01

    The Fischer–Tropsch to olefins (FTO) process is a method for the direct conversion of synthesis gas to lower C2–C4 olefins. Carbon-supported iron carbide nanoparticles are attractive catalysts for this reaction. The catalytic activity can be improved and undesired formation of alkanes can be suppres