![[ Back to EurekAlert! ]](http://www.eurekalert.org/images/back2e.gif){kind=small}
Public release date: 7-Apr-2013[ | E-mail |
Share ] Contact: Michael Bernstein
m_bernstein@acs.org
504-670-4707 (New Orleans Press Center, April 5-10)
202-872-6042
Michael Woods
m_woods@acs.org
504-670-4707 (New Orleans Press Center, April 5-10)
202-872-6293
American Chemical Society
NEW ORLEANS, April 7, 2013 At least nine Nobel laureates have research that will be presented here this week during the 245th National Meeting & Exposition of the American Chemical Society, the world's largest scientific society. Research from the laureates' teams will be among almost 12,000 presentations during the event, expected to attract more than 14,000 scientists and others.
They are Robert H. Grubbs, Ph.D.; Richard R Schrock, Ph.D.; Brian K. Kobilka, Ph.D.; Robert J. Lefkowitz, Ph.D.; Ei-ichi Negishi, Ph.D.; George A. Olah, Ph.D.; Karl Barry Sharpless, Ph.D.; Ada Yonath, Ph.D.; and Ahmed Zewail, Ph.D.
Grubbs, who is with the California Institute of Technology, and Schrock, who is with the Massachusetts Institute of Technology, shared the 2005 Nobel Prize in Chemistry with Yves Chauvin for the development of the "metathesis method." That new way to make plastics, medicines and other products was an advance in "green chemistry," because it reduces the production of potentially hazardous waste compared with other approaches.
Kobilka, who is with the Stanford University School of Medicine, and Lefkowitz, who is with the Howard Hughes Medical Institute and the Duke University Medical Center, shared the 2012 Nobel Prize in Chemistry "for studies of G-protein-coupled receptors." Their research showed how these receptors work to sense the environment of the cell.
Negishi, the Herbert C. Brown Distinguished Professor of Organic Chemistry at Purdue University, shared the 2010 Nobel Prize in Chemistry "for palladium-catalyzed cross couplings in organic synthesis." This helped develop techniques to synthesize complex carbon molecules that have had an enormous impact on the manufacture of medicines and other products.
Olah, who is with the University of Southern California, won the 1994 Nobel Prize in Chemistry for work on "carbocations," charged molecules that were considered too unstable to study. Olah developed a way to isolate these molecules, which was useful in the oil and coal industries.
Sharpless, who is with The Scripps Research Institute, won the 2001 Nobel Prize in Chemistry "for his work on chirally catalysed oxidation reactions." Sharpless worked on ways to synthesize just one of a set of "mirror" image molecules. This work led to advances in drug development.
Yonath, who is with the Weizmann Institute of Science, shared the 2009 Nobel Prize in Chemistry with Venkatraman Ramakrishnan and Thomas A. Steitz "for studies of the structure and function of the ribosome." They showed how the ribosome works at an atomic level to translate the information in DNA into proteins for life.
Zewail, who is with the California Institute of Technology, won the 1999 Nobel Prize in Chemistry "for his studies of the transition states of chemical reactions using femtosecond spectroscopy." Zewail showed that it was possible to watch chemical reactions in "slow-motion" using lasers to see how the molecules move.
Further information on the presentations follows.
###
The American Chemical Society is a nonprofit organization chartered by the U.S. Congress. With more than 163,000 members, ACS is the world's largest scientific society and a global leader in providing access to chemistry-related research through its multiple databases, peer-reviewed journals and scientific conferences. Its main offices are in Washington, D.C., and Columbus, Ohio.
To automatically receive news releases from the American Chemical Society, contact newsroom@acs.org.
Note to journalists: Please report that this research was presented at a meeting of the American Chemical Society. Follow us: Twitter | Facebook
Abstracts
Robert H. Grubbs, Ph.D.
Milder routes to chelated ruthenium complexes for Z-selective metathesis
Lauren E. Rosebrugh, Myles B. Herbert, Vanessa M. Marx, Benjamin K. Keitz, Robert H. Grubbs
A novel method to effect the salt metathesis and C-H activation of ruthenium-based, Z-selective metathesis catalysts containing a chelated N-heterocyclic carbene (NHC) ligand using sodium carboxylates is reported. This method allows for the successful formation of stable chelated species containing a variety of alterations to the NHC ligand that had decomposed under the previous approach. As such, several new, chelated metathesis-active ruthenium complexes are described, including a catalyst system exhibiting >95% Z-selectivity and record TONs (up to 8100) in homodimerization reactions of terminal olefins. Moreover, a catalyst has been synthesized that gives highly cis, highly tactic polymers via ring opening metathesis polymerization of strained, cyclic olefins, marking the first time tactic polymers have been made using a ruthenium-based metathesis catalysts.
Monday, April 8, 2013 08:00 PM
Sci-Mix (08:00 PM - 10:00 PM)
Location: Morial Convention Center
Room: Hall D
Tuesday, April 9, 2013 06:00 PM
Organometallic Chemistry (06:00 PM - 08:00 PM)
Location: Morial Convention Center
Room: Hall D
Methods for the cleavage of C-O bonds
Robert H Grubbs
The conversion of biorenewable resources into chemical will require the efficient removal of excess functionality. The C-O bonds in a variety of highly oxidized biomaterials can be difficult to convert into compounds of lower oxidation state. While screening a variety of catalysts, new methods for the efficient cleavage of aromatic and aliphatic C-O linkages have been developed.
Tuesday, April 9, 2013 11:25 AM
ACS Award in Pure Chemistry: Symposium in Honor of Theodor Agapie (08:30 AM - 12:30 PM)
Location: Morial Convention Center
Room: 345
Design of selective catalysts for olefin metathesis
Robert H Grubbs
Olefin metathesis has become a tool for the synthesis of a variety of molecules and materials. In the past several years the efficiency and selectivity of the catalysts have greatly improved. Catalysts are now available that allow the precise control of the double bond geometrh of the product double bond. Organometallic synthesis and computational results have resulted in new levels of selectivity and efficiency.
Tuesday, April 9, 2013 08:30 AM
Gabor A. Somorjai Award for Creative Research in Catalysis: Symposium in Honor of Tobin J. Marks (08:25 AM - 11:45 AM)
Location: Morial Convention Center
Room: 346
Design and synthesis of new ruthenium-based catalysts for improved activity in challenging Z-selective metathesis reactions
Brendan L. Quigley, Vanessa M. Marx, Robert H. Grubbs
Our group has recently reported a series of ruthenium-based metathesis catalysts that contain a chelating NHC. These catalysts demonstrate high Z-selectivity in a variety of metathesis reactions including cross metathesis, ring-closing metathesis and ring-opening metathesis polymerization. However, the substrate scope has so far been limited to relatively unhindered olefins. In order to probe the origin of this selectivity, a series of catalysts with N-heterocyclic carbene (NHC) substituents of varying steric bulk were prepared. These catalysts were subsequently examined for improved reactivity in a range of olefins that contain bulky substituents. In addition, the mechanism of the C-H-activation step in the synthesis of such catalysts was probed through variation of the sterics and electronics of both the adamantyl and aryl NHC substituents.
Tuesday, April 9, 2013 08:00 PM
Graphene Chemistry, Metal-Mediated Reactions and Syntheses, Molecular Recognition and Self-Assembly, Physical Organic Chemistry, Materials Devices and
Switches (08:00 PM - 10:00 PM)
Location: Morial Convention Center
Room: Hall D
Transition-metal-free reductive cleavage of lignin-related C-O bonds by an activated silane
Anton A Toutov, Alexey Fedorov, Nicholas Swisher, Robert H. Grubbs
Reported herein is a transition-metal-free protocol for the efficient reductive cleavage of diaryl and aryl alkyl ethers. The combination of triethylsilane with simple bases forms an unusually powerful reductive couple that affords regioselective rupture of lignin- and coal-related C-O bonds in aromatic ethers. Interestingly, this is accompanied by ortho-directed C-H silylation that be-comes preferred with certain bases and temperature re-gimes. However, the tuning of selectivity proved possible thus enabling the development of a practical method for the title transformation, as illustrated by the reduction of lignin model compounds to their corresponding phenolic and aromatic constituents.
Monday, April 8, 2013 08:00 PM
Sci-Mix (08:00 PM - 10:00 PM)
Location: Morial Convention Center
Room: Hall D
Tuesday, April 9, 2013 02:00 PM
Advances in Energy and Fuels Processes, Systems, Materials and Utilization (02:00 PM - 04:00 PM)
Location: Morial Convention Center
Room: Hall D
Preparation of rapidly initiating ruthenium based olefin metathesis catalysts
Alexandra H. Sullivan, Benjamin K. Keitz, Robert H. Grubbs
Z-selective olefin metathesis ruthenium catalysts are highly sought after, due to their wide applications in both pharmaceuticals and materials science. A crucial step towards the preparation of rapidly initiating, Z-selective, olefin metathesis catalysts was found to be the addition of sodium pivalate to phosphonium alkyidene catalyst 1, resulting in the formation of the C-H activated complex 2 after two days of heating. Preparation of 2, a close analog to the target catalyst 4, promises that future synthesis of 4 should be facile.
Sunday, April 7, 2013 06:00 PM
Undergraduate Research at the Frontiers of Inorganic Chemistry (06:00 PM - 08:00 PM)
Location: Morial Convention Center
Room: Hall D
Catalyst-controlled anti-Markovnikov palladium-catalyzed oxidation of aliphatic olefins
Zachary K Wickens, Bill Morandi, Robert H Grubbs
The Wacker oxidation, or the palladium-catalyzed oxidation of olefins to carbonyls, is one of the most well-known palladium-catalyzed reactions and has extensive synthetic applications. Traditional Wacker oxidation conditions obey Markonikov's rule and thus yield methyl ketones with high selectivity from the majority of terminal olefins. A Wacker oxidation capable of producing aldehydes from unbiased terminal olefins would be synthetically useful and is a long-standing challenge in palladium oxidation chemistry. A palladium-catalyzed oxidation system capable of providing synthetic access to aldehydes from unbiased terminal olefins will be discussed.
Tuesday, April 9, 2013 08:20 AM
Metal Mediated Reactions (08:00 AM - 12:00 PM)
Location: Morial Convention Center
Room: 256/257
Synthetic applications of Z-selective ruthenium-based olefin metathesis catalysts
Vanessa M Marx, Myles B Herbert, Benjamin K Keitz, Robert H Grubbs
The first report of Z-selective macrocyclizations using a ruthenium-based metathesis catalyst is described. Selectivity for Z-macrocycles is consistently high for a diverse set of substrates bearing different functional groups and comprised of various ring sizes. The same catalyst was employed for the Z-selective ethenolysis of a mixture of E and Z macrocycles, providing the pure E-isomers. These methodologies were successfully applied to the construction of several olfactory macrocycles, as well as the backbone of cytotoxic alkaloid natural products. Conditions were also optimized for a series of challenging cross metathesis reactions using the same catalyst system, and subsequently exploited in the synthesis of a family of lepidopteran insect pheromones. A detailed mechanistic study probing the origin of the stereoselectivity in these challenging transformations is currently underway, and will also be discussed in detail.
Monday, April 8, 2013 01:00 PM
Metal Mediated Reactions (01:00 PM - 05:00 PM)
Location: Morial Convention Center
Room: 256/257
Functionalized corroles as diatherapeutic, multi-modal imaging agents
Melanie A Pribisko, Punnajit Lim, John Termini, Robert H Grubbs, Joshua H Palmer, Harry B Gray
Recent synthetic advancements have made it possible to produce substituted derivatives of meso-5,10,15-(tris)pentafluorophenylcorrole (H3tpfc) in reasonable yields. We present the scalable syntheses of new H3tpfc derivatives, and a few of their metal complexes, through nucleophilic aromatic substitution on the pentafluorophenyl substituents. These complexes have potential applications both as imaging agents and chemotherapeutic drugs.
Sunday, April 7, 2013 06:00 PM
Metals in Medicine: Diagnostic and Therapeutic Applications (06:00 PM - 08:00 PM)
Location: Morial Convention Center
Room: Hall D
ROMP with stable initiators
Robert Howard Grubbs
Tim Swager introduced the name ROMP for ring opening metathesis polymerization when he was a a graduate student. Since that time, many new initiators for the ROMP of strained olefins have been developed. Recent advances now allow polymers with precise chain length and composition to be prepared. The synthesis of brush polymers demonstrates the control of polymeric structures that are now possible with modern initiators.
Tuesday, April 9, 2013 02:50 PM
ACS Award for Creative Invention: Symposium in Honor of Timothy M. Swager (01:15 PM - 05:30 PM)
Location: Hilton Riverside
Room: HEC C
Z-selective ethenolysis using a ruthenium catalyst: Applications and mechanistic implications
Myles B Herbert, Hiroshi Miyazaki, Peng Liu, Vanessa M Marx, Benjamin K. Keitz, Robert H Grubbs
Unique ethenolysis reactivity has been uncovered with a new family of chelated ruthenium alkylidene catalysts that have exhibited high Z-selectivity in cross metathesis, ring opening metathesis polymerization, and macrocyclic ring closure reactions. Exposure of a mixture of cis- and trans-internal olefins to ethylene and a chelated ruthenium catalyst results in the selective ethenolysis of only the cis-isomer; this phenomenon was first reported for a Z-selective molybdenum metathesis catalyst. Applications for the resolution of trans-internal olefins have been explored particularly in the isolation of purely trans-olefin containing macrocyclic rings. Additionally, Z-selective ethenolysis is being explored as an important process in the mechanism and behavior of this family of chelated Z-selective catalysts.
Thursday, April 11, 2013 12:20 PM
Organometallic Chemistry (08:30 AM - 12:40 PM)
Location: Morial Convention Center
Room: 335/336
Asymmetric cyclic alkyl amino carbene (CAAC) ruthenium complexes as improved catalysts for ethenolysis
Vanessa M Marx, Mohand Melaimi, Robert H Grubbs, Guy Bertrand
Ethenolysis, the cross metathesis reaction of an internal olefin with ethylene to generate two terminal olefin products, has long been proposed as a method for the rapid production of commodity, value-added products from inexpensive, readily-available seed oil derivatives. For application to commodity chemicals, the TON should be at least 50,000. Prior to this report, such a catalyst system had yet to be developed. Herein, we disclose ruthenium complexes of cyclic alkyl amino carbene (CAAC) ligands bearing asymmetric ortho substitution on the N-aryl ring, as potentially viable catalyst systems for ethenolysis reactions on an industrial scale. In the ethenolysis of methyl oleate, these catalyst systems exhibit TONs > 100,000 and >90% selectivity for terminal olefins, at a loading of 3 ppm. Mechanistic investigations probing this remarkable activity are ongoing, and will also be presented in detail.
Wednesday, April 10, 2013 02:10 PM
Organometallic Chemistry (01:30 PM - 05:40 PM)
Location: Morial Convention Center
Room: 342
Initiator control of the tacticity of ROMP polymers
Robert Howard Grubbs
A variety of metal based ROMP initiators have been developed over the past several years that allow precise control of polymer structure. Recently initiators based on molybdenum and ruthenium that provide control of the double bond geometry of the resulting polymers. Many of these also provide precise control of the tacticity of the backbone. Metallocene catalysts provide good models for this control
Monday, April 8, 2013 10:00 AM
ACS Award in Applied Polymer Science: Symposium in Honor of Mitchell A. Winnik (08:55 AM - 12:00 PM)
Location: Hilton Riverside
Room: Grand Ballroom B
Milder routes to chelated ruthenium complexes for Z-selective metathesis
Lauren E. Rosebrugh, Myles B. Herbert, Vanessa M. Marx, Benjamin K. Keitz, Robert H. Grubbs
A novel method to effect the salt metathesis and C-H activation of ruthenium-based, Z-selective metathesis catalysts containing a chelated N-heterocyclic carbene (NHC) ligand using sodium carboxylates is reported. This method allows for the successful formation of stable chelated species containing a variety of alterations to the NHC ligand that had decomposed under the previous approach. As such, several new, chelated metathesis-active ruthenium complexes are described, including a catalyst system exhibiting >95% Z-selectivity and record TONs (up to 8100) in homodimerization reactions of terminal olefins. Moreover, a catalyst has been synthesized that gives highly cis, highly tactic polymers via ring opening metathesis polymerization of strained, cyclic olefins, marking the first time tactic polymers have been made using a ruthenium-based metathesis catalysts.
Monday, April 8, 2013 08:00 PM
Sci-Mix (08:00 PM - 10:00 PM)
Location: Morial Convention Center
Room: Hall D
Tuesday, April 9, 2013 06:00 PM
Organometallic Chemistry (06:00 PM - 08:00 PM)
Location: Morial Convention Center
Room: Hall D
Richard R Schrock, Ph.D.
Highly Z-selective and chemoselective olefin metathesis of 1,3-dienes: Catalytic studies and exploration of unusual intermediates
Erik M Townsend, Amir H Hoveyda, Richard R Schrock
Molybdenum and tungsten monoaryloxide pyrrolide (MAP) alkylidene complexes catalyze the Z-selective metathesis homocoupling of (E)-1,3-diene substrates to give (E,Z,E) conjugated trienes in high yield. The most effective catalysts highly prefer reaction with the terminal alkene functionality of the dienes, limiting the formation of unwanted side products. Cross metathesis of (E)-1,3-dienes with various olefinic substrates (including vinyl ethers) using the same catalyst systems selectively furnishes products containing the (E,Z) conjugated diene motif. These reactions proceed through unusual alkylidene intermediates, such as vinylalkylidenes and alkoxyalkylidenes. Isolation and characterization of vinylalkylidene and alkoxyalkylidene MAP species are reported along with investigations of their stability and reactivity.
Wednesday, April 10, 2013 12:20 PM
Organometallic Chemistry (08:30 AM - 12:40 PM)
Location: Morial Convention Center
Room: 344
Energetics and dynamics of the low-lying electronic states of constrained polyenes: Implications for infinite polyenes
Ronald L Christensen, Miriam M Enriquez, Nicole L Wagner, Alexandra Y Peacock-Villada, Corina Scriban, Richard R Schrock, Tom Polvka, Harry A Frank, Robert R Birge
Steady-state and ultrafast transient absorption spectra have been recorded for a series of conformationally-constrained, isomerically pure polyenes with 5?23 conjugated double bonds (N). These data and fluorescence spectra of the shorter polyenes reveal the N dependence of the energies of several 1Bu+ and 1Ag? excited states. The 1Bu+ states converge to a common long polyene asymptotic limit of 15,900 100 cm-1. On the other hand, the excited 1Ag? states exhibit a large (~9000 cm-1) energy difference in their long polyene limits, in contrast to the common value previously predicted by theory. EOM-CCSD ab-initio and MNDO-PSDCI semi-empirical MO theories account for the experimental transition energies and intensities. The complex, multistep dynamics of the 11Bu+ ? 21Ag? ? 11Ag? excited state decay pathways as a function of N have been compared with kinetic data from several natural and synthetic carotenoids. Analysis of the lifetimes of the 21Ag? states, using the energy gap law for nonradiative decay, reveals remarkable similarities in the N dependence of the 21Ag? decay kinetics of carotenoid and polyene systems. These data are important for understanding the mechanisms by which carotenoids carry out their roles as light-harvesting molecules and photoprotective agents in biological systems.
Wednesday, April 10, 2013 06:00 PM
PHYS Poster Session (06:00 PM - 09:00 PM)
Location: Morial Convention Center
Room: Hall D
Dehydrogenation and metathesis of alkanes catalyzed by pincer-iridium complexes: Mechanistic studies and catalyst design
Soumik Biswas, Tian Zhou, David Y. Wang, Jason Hackenberg, Agnieszka Nawara-Hultzsch, Richard R. Schrock, Maurice Brookhart, Karsten Krogh-Jespersen, Alan S. Goldman
Pincer-iridium complexes have been reported to catalyze the dehydrogenation of alkanes and these catalyst have been combined with olefin metathesis catalysts to give a tandem catalytic system for alkane metathesis. A major challenge in dehydrogenation, and in alkane metathesis in particular, is to achieve regioselectivity for the terminal position of n-alkane substrates. We report combined computational and experimental studies which have elucidated the factors that determine the regioselectivity of dehydrogenation. In particular, we find that various pincer-iridium complexes will react with n-alkanes to initially give the 1-alkene dihydride. However, in some cases, e.g. (tBuPOCOP)Ir, the barrier to loss of olefin is high and the coordinated 1-alkene re-inserts into an Ir-H bond and ultimately gives internal olefin as a major kinetic product. We also report the rational development of pincer-iridium complexes that are more effective for alkane metathesis than the parent complexes (tBuPOCOP)Ir and (tBuPCP)Ir.
Tuesday, April 9, 2013 04:35 PM
Organometallic Developments in C-H Bond Activation (01:30 PM - 05:00 PM)
Location: Morial Convention Center
Room: 343
Brian K. Kobilka, Ph.D. and Robert J Lefkowitz, Ph.D.
G-protein coupled receptors in virtual screening: Functional fidelity and selectivity
Dahlia R Weiss, SeungKirl Ahn, Maria F Sassano, Andrew C Kruse, Joel Karpiak, Bryan L Roth, Brian K Kobilka, Brian K Shoichet, Robert J Lefkowitz
A prospective, large library virtual screen against an activated 2-adrenergic receptor structure returned potent agonists, essentially to the exclusion of antagonists. In addition, two hits recapitulated the arrestin signaling bias of the co-crystal ligand. This functional fidelity has important implications in drug-design, as the ability to predict ligands with predefined signaling properties is highly desirable. Furthermore, we use virtual screening to predict ligands of pre-defined selectivity. We are searching for ligands with high affinity for dopamine and serotonin receptors, which mediate the therapeutic effects of anti-psychotic medications, and poor affinity for histamine receptor, which mediates serious metabolic side effects. This has led to selective molecules, but also to molecules with high affinity for the "anti-target" histamine receptor, raising important questions about false negatives in docking. Finally, using docking against structures of the M2 and M3 muscarinic receptor subtypes, we have identified novel binding chemotypes, some which show a functional selectivity.
Wednesday, April 10, 2013 02:00 PM
Protein-Ligand Interactions: Insights, New Tools and Applications in Drug Design (01:30 PM - 05:15 PM)
Location: Morial Convention Center
Room: 355
Ei-ichi Negishi, Ph.D.
Widely applicable, catalytic, and asymmetric method for the synthesis of enantiomerically pure (99%) tertiary alkyl-containing 1-alkanols via ZACA-Pd- or Cu-catalyzed cross-coupling
Shiqing Xu, Hirofumi Kamada, Akimichi Oda, Ei-ichi Negishi
Despite recent major advances in the synthesis of chiral tertiary alkyl-containing compounds including a large number of those with biologically and medicinally important properties, e.g., isoprenoids, deoxypolypropionates, and others, through the development of catalytic asymmetric alkene hydrogenation, epoxidation, carboalumination, and so on, it still remains very challenging to prepare these classes of compounds, especially of feeble chirality, as isomerically pure (>99%) substances. To overcome these problems, a widely applicable, catalytic, and asymmetric method for the synthesis of enantiomerically pure (>99%) various tertiary alkyl-containing 1-alkanols, especially of feeble chirality, via ziconium-catalyzed asymmetric carboalumination of alkenes (ZACA)-Pd- or Cu-catalyzed cross-coupling tandem processes has been developed. The utility of this new synthetic method for the total synthesis of natural productsof biological and medicinal importance will also be discussed.
Sunday, April 7, 2013 08:00 PM
Chemistry of Energy and Food, Asymmetric Reactions and Syntheses, Total Synthesis of Complex Molecules, Biologically-Related Molecules and Processes (08:00 PM - 10:00 PM)
Location: Morial Convention Center
Room: Hall D
George A. Olah, Ph.D.
N-difluoromethylation of heterocyclic aromatic compounds using Ruppert-Prakash reagent
G. K. Surya Prakash, Sankarganesh Krishnamoorthy, Aditya Kulkarni, Somesh Kumar Ganesh, George A Olah
Organofluorine compounds possess interesting biological properties such as enhanced metabolic stability, lipophilicity and bioavailability as compared to the nonfluorinated analogs. Difluoromethylated organofluorine compounds are of particular interest since the CF2H group is known to be isosteric and isopolar with the hydroxyl group. N-heterocycles containing CF2H group at the N atom are important drug candidates and agrochemicals. Herein, we report direct difluoromethylation of heterocycles such as imidiazoles, benzimidazoles and indoles using the Ruppert-Prakash reagent (Scheme 1). The reactions were initiated under neutral conditions in presence of catalytic amount of fluoride initiators. The difluoromethylated products were formed in moderate to good yields through CF2carbene insertion in the N-H bond. Inexpensive and commercially available starting materials and ambient reaction conditions are the highlights of this methodology.
Monday, April 8, 2013 08:00 PM
Sci-Mix (08:00 PM - 10:00 PM)
Location: Morial Convention Center
Room: Hall D
Wednesday, April 10, 2013 07:00 PM
New Reactions and Methodology, Heterocycles and Aromatics (07:00 PM - 10:00 PM)
Location: Morial Convention Center
Room: Hall A
Regenerable polyamine bbased solid adsorbents for CO2 capture from the air
Hang Zhang, Alain Goeppert, Miklos Czaun, Robert B May, G. K. Surya Prakash, George A. Olah, S R Narayanan
Fumed silica supported PEI adsorbents are promising candidates for capturing CO2 directly from air. They have high CO2 adsorption capacity and can be regenerated under mild conditions over repeated adsorption/desorption cycles. They are easy to prepare from readily available and inexpensive materials. Being solids these adsorbents avoid many of the problems associated with existing CO2 separation technologies based on liquid amine based scrubbers. Once capture, the CO2 could be recycled to fuels and materials representing essentially a first step in an anthropogenic carbon cycle. More immediate applications include the scrubbing of CO2 from closed environments such as space stations and submarines. Supplying of CO2 free air is also important for the operation of inexpensive and robust iron-air batteries using alkaline electrolytes for large scale energy storage in grid applications.
Monday, April 8, 2013 08:00 PM
Sci-Mix (08:00 PM - 10:00 PM)
Location: Morial Convention Center
Room: Hall D
Tuesday, April 9, 2013 02:00 PM
Advances in Energy and Fuels Processes, Systems, Materials and Utilization (02:00 PM - 04:00 PM)
Location: Morial Convention Center
Room: Hall D
Ruthenium-catalyzed hydrogen generation from formic acid
Miklos Czaun, Alain Goeppert, Jenny Yun Yue Zhang, Robert B. May, Michael Sax, G. K. Surya Prakash, George A. Olah
As our rising energy demand is met with limited fossil fuel resources, energy contribution from renewables has to be increased. Due to the intermittent and fluctuating nature of renewable energy and the variations in energy consumption, energy storage has gained increasing attention. Hydrogen can be generated from water, converted to formic acid (FA) using renewable electricity and then used as a fuel in hydrogen-air fuel cells to produce electricity on demand. A carbon neutral energy storage cycle using FA as a storage medium is depicted in Figure 1.
Decomposition of FA to H2 and CO2 in the presence of RuCl3 resulted in the formation of [H4Ru4(CO)12] in situ in high yield indicating that this cluster complex is an active catalyst or its direct precursor. X-ray diffraction, FTIR, 1H, and 13C NMR measurements confirmed the presence of a tetrahedral Ru core with terminal carbonyl and bridging hydride ligands.
On the basis of kinetic and spectroscopic measurements, we suggest a reaction mechanism for the decomposition of FA involving a dissociative rate limiting step.
Tuesday, April 9, 2013 06:00 PM
Organometallic Chemistry (06:00 PM - 08:00 PM)
Location: Morial Convention Center
Room: Hall D
Development of safe and efficient catalysts for organic transformations
G. K. Surya Prakash, Thomas Mathew, George A. Olah
Development of efficient and recyclable catalysts and their use in various organic transformations with emphasizing the need for reducing the toxic wastes and solvents, thereby conducting the reactions under green conditions become the main focus of recent research in sustainable development. Lewis and metal based catalysts such as gallium tetraflate and related systems were prepared and used for a series of organic reactions in our laboratories. They are found to be stable, often recyclable and require very low catalyst loadings.
Monday, April 8, 2013 02:20 PM
New Reactions and Methodology (01:00 PM - 05:00 PM)
Location: Morial Convention Center
Room: 245
Hydrogen generation by selective decomposition of formic acid in the presence of ruthenium pincer ligand complexes
Jotheeswari Kothandaraman, Miklos Czaun, Alain Goeppert, Robert B. May, G. K. Surya Prakash, George A. Olah
Selective decomposition of formic acid (FA) to H2 and CO2 mixture with no trace of CO has gained increasing attention as the gas stream can be directly used in a H2/air fuel cell without poisoning of the anode catalyst. The commercially available pincer ligand complex, carbonylchlorohydrido[bis(2-(diphenylphosphinoethyl)amino]ruthenium(II)(Ru-MACHOTM) was investigated as a potential catalyst for the decarboxylation of FA.. The in situ formed new hydrido carbonyl species were explored by the spectroscopic methods, such as, FTIR, 1H NMR, 13C NMR, COSY, HMBC, HSQC, 2D NOESY and 31P NMR. In addition, the gas evolved in the course of the reaction was studied by GC and FTIR in order to determine the selectivity of the catalyst. Based on the spectroscopic studies, a plausible mechanism was suggested for the catalytic decomposition of FA to H2 and CO2. The isolation and structural characterization of the intermediate complexes by single crystal X-ray diffraction further supports the mechanism.
Tuesday, April 9, 2013 06:00 PM
Organometallic Chemistry (06:00 PM - 08:00 PM)
Location: Morial Convention Center
Room: Hall D
Regenerable polyamine bbased solid adsorbents for CO2 capture from the air
Hang Zhang, Alain Goeppert, Miklos Czaun, Robert B May, G. K. Surya Prakash, George A. Olah, S R Narayanan
Fumed silica supported PEI adsorbents are promising candidates for capturing CO2 directly from air. They have high CO2 adsorption capacity and can be regenerated under mild conditions over repeated adsorption/desorption cycles. They are easy to prepare from readily available and inexpensive materials. Being solids these adsorbents avoid many of the problems associated with existing CO2 separation technologies based on liquid amine based scrubbers. Once capture, the CO2 could be recycled to fuels and materials representing essentially a first step in an anthropogenic carbon cycle. More immediate applications include the scrubbing of CO2 from closed environments such as space stations and submarines. Supplying of CO2 free air is also important for the operation of inexpensive and robust iron-air batteries using alkaline electrolytes for large scale energy storage in grid applications.
Monday, April 8, 2013 08:00 PM
Sci-Mix (08:00 PM - 10:00 PM)
Location: Morial Convention Center
Room: Hall D
Tuesday, April 9, 2013 02:00 PM
Advances in Energy and Fuels Processes, Systems, Materials and Utilization (02:00 PM - 04:00 PM)
Location: Morial Convention Center
Room: Hall D
Karl Barry Sharpless, Ph.D.
Click chemistry today
Karl Barry Sharpless
The rapid discovery of new and/or desirable function, and that function's equally rapid development into superior chemical products--that's what click chemistry was created to do.
Click chemistry's method is linking up super-smart modules via a few near-quantitative steps; click chemistry's reach and power are a factor of how nearly those linking reactions approach perfection. In 2001 this radical strategy was proposed to the world's chemists on the strength of a few good reactions--and it was not well received! However, click chemistry took off after the discovery (and rediscovery) of two or three near-perfect click reactions. These best reactions' best applications will be presented. The fact of their overnight adoption in nearly all fields of chemistry surprised us along with everyone. In hindsight, until witnessing at least one perfect linkage process in action, unstoppable under terrestrial conditions, how could anyone imagine what it would do for chemical technology.
Sunday, April 7, 2013 03:05 PM
Isbell Award and Gin New Investigator Award Symposium (01:00 PM - 04:50 PM)
Location: New Orleans Downtown Marriott at the Convention Center
Room: Blaine Kern A
Ada Yonath, Ph.D.
From basic science to advanced medicine
Ada Yonath
Ribosomes, the universal cellular machines that translate the genetic code into proteins, are targeted by many antibiotics that paralyze them by binding to their functional sites. Antibiotics binding modes, inhibitory action and synergism pathways have been determined for almost all ribosomal antibiotics. These show the principles of differentiate between patients and pathogens, suggest mechanisms leading to bacterial resistance and paved ways to design advanced therapeutics capable of minimizing antibiotics resistance.
Sunday, April 7, 2013 01:30 PM
Global Health Challenges: The Need for New Anti-Infectives and Antivirals (01:30 PM - 05:10 PM)
Location: Morial Convention Center
Room: R08/R09
Ahmed Zewail, Ph.D.
Single-nanoparticle switching dynamics visualized by 4D electron microscopy
Renske M van der Veen, Sang Tae Park, Oh-Hoon Kwon, Antoine Tissot, Andreas Hauser, Ahmed Zewail
4D electron microscopy enables simultaneous real- and reciprocal-space imaging of nanostructured materials with unprecedented spatio-temporal resolutions. Here we apply it to visualize the photoswitching dynamics of single spin-crossover nanocrystals. The nanoparticles are largely influenced by the frictional and thermal characteristics of the interface, which are unique on the level of a single nanoparticle, while averaged out in conventional studies on nanoparticles ensembles. Theoretical modeling reveals the non-equilibrium thermoswitching pathways in the phase diagram of the spin transition.
Tuesday, April 9, 2013 02:30 PM
Ultrafast Excited-State Dynamics in Transition Metal-Containing Systems (01:30 PM - 04:30 PM)
Location: Morial Convention Center
Room: 346
[ | E-mail | Share ] ?
AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert! system.
Public release date: 7-Apr-2013[ | E-mail |
Share ] Contact: Michael Bernstein
m_bernstein@acs.org
504-670-4707 (New Orleans Press Center, April 5-10)
202-872-6042
Michael Woods
m_woods@acs.org
504-670-4707 (New Orleans Press Center, April 5-10)
202-872-6293
American Chemical Society
NEW ORLEANS, April 7, 2013 At least nine Nobel laureates have research that will be presented here this week during the 245th National Meeting & Exposition of the American Chemical Society, the world's largest scientific society. Research from the laureates' teams will be among almost 12,000 presentations during the event, expected to attract more than 14,000 scientists and others.
They are Robert H. Grubbs, Ph.D.; Richard R Schrock, Ph.D.; Brian K. Kobilka, Ph.D.; Robert J. Lefkowitz, Ph.D.; Ei-ichi Negishi, Ph.D.; George A. Olah, Ph.D.; Karl Barry Sharpless, Ph.D.; Ada Yonath, Ph.D.; and Ahmed Zewail, Ph.D.
Grubbs, who is with the California Institute of Technology, and Schrock, who is with the Massachusetts Institute of Technology, shared the 2005 Nobel Prize in Chemistry with Yves Chauvin for the development of the "metathesis method." That new way to make plastics, medicines and other products was an advance in "green chemistry," because it reduces the production of potentially hazardous waste compared with other approaches.
Kobilka, who is with the Stanford University School of Medicine, and Lefkowitz, who is with the Howard Hughes Medical Institute and the Duke University Medical Center, shared the 2012 Nobel Prize in Chemistry "for studies of G-protein-coupled receptors." Their research showed how these receptors work to sense the environment of the cell.
Negishi, the Herbert C. Brown Distinguished Professor of Organic Chemistry at Purdue University, shared the 2010 Nobel Prize in Chemistry "for palladium-catalyzed cross couplings in organic synthesis." This helped develop techniques to synthesize complex carbon molecules that have had an enormous impact on the manufacture of medicines and other products.
Olah, who is with the University of Southern California, won the 1994 Nobel Prize in Chemistry for work on "carbocations," charged molecules that were considered too unstable to study. Olah developed a way to isolate these molecules, which was useful in the oil and coal industries.
Sharpless, who is with The Scripps Research Institute, won the 2001 Nobel Prize in Chemistry "for his work on chirally catalysed oxidation reactions." Sharpless worked on ways to synthesize just one of a set of "mirror" image molecules. This work led to advances in drug development.
Yonath, who is with the Weizmann Institute of Science, shared the 2009 Nobel Prize in Chemistry with Venkatraman Ramakrishnan and Thomas A. Steitz "for studies of the structure and function of the ribosome." They showed how the ribosome works at an atomic level to translate the information in DNA into proteins for life.
Zewail, who is with the California Institute of Technology, won the 1999 Nobel Prize in Chemistry "for his studies of the transition states of chemical reactions using femtosecond spectroscopy." Zewail showed that it was possible to watch chemical reactions in "slow-motion" using lasers to see how the molecules move.
Further information on the presentations follows.
###
The American Chemical Society is a nonprofit organization chartered by the U.S. Congress. With more than 163,000 members, ACS is the world's largest scientific society and a global leader in providing access to chemistry-related research through its multiple databases, peer-reviewed journals and scientific conferences. Its main offices are in Washington, D.C., and Columbus, Ohio.
To automatically receive news releases from the American Chemical Society, contact newsroom@acs.org.
Note to journalists: Please report that this research was presented at a meeting of the American Chemical Society. Follow us: Twitter | Facebook
Abstracts
Robert H. Grubbs, Ph.D.
Milder routes to chelated ruthenium complexes for Z-selective metathesis
Lauren E. Rosebrugh, Myles B. Herbert, Vanessa M. Marx, Benjamin K. Keitz, Robert H. Grubbs
A novel method to effect the salt metathesis and C-H activation of ruthenium-based, Z-selective metathesis catalysts containing a chelated N-heterocyclic carbene (NHC) ligand using sodium carboxylates is reported. This method allows for the successful formation of stable chelated species containing a variety of alterations to the NHC ligand that had decomposed under the previous approach. As such, several new, chelated metathesis-active ruthenium complexes are described, including a catalyst system exhibiting >95% Z-selectivity and record TONs (up to 8100) in homodimerization reactions of terminal olefins. Moreover, a catalyst has been synthesized that gives highly cis, highly tactic polymers via ring opening metathesis polymerization of strained, cyclic olefins, marking the first time tactic polymers have been made using a ruthenium-based metathesis catalysts.
Monday, April 8, 2013 08:00 PM
Sci-Mix (08:00 PM - 10:00 PM)
Location: Morial Convention Center
Room: Hall D
Tuesday, April 9, 2013 06:00 PM
Organometallic Chemistry (06:00 PM - 08:00 PM)
Location: Morial Convention Center
Room: Hall D
Methods for the cleavage of C-O bonds
Robert H Grubbs
The conversion of biorenewable resources into chemical will require the efficient removal of excess functionality. The C-O bonds in a variety of highly oxidized biomaterials can be difficult to convert into compounds of lower oxidation state. While screening a variety of catalysts, new methods for the efficient cleavage of aromatic and aliphatic C-O linkages have been developed.
Tuesday, April 9, 2013 11:25 AM
ACS Award in Pure Chemistry: Symposium in Honor of Theodor Agapie (08:30 AM - 12:30 PM)
Location: Morial Convention Center
Room: 345
Design of selective catalysts for olefin metathesis
Robert H Grubbs
Olefin metathesis has become a tool for the synthesis of a variety of molecules and materials. In the past several years the efficiency and selectivity of the catalysts have greatly improved. Catalysts are now available that allow the precise control of the double bond geometrh of the product double bond. Organometallic synthesis and computational results have resulted in new levels of selectivity and efficiency.
Tuesday, April 9, 2013 08:30 AM
Gabor A. Somorjai Award for Creative Research in Catalysis: Symposium in Honor of Tobin J. Marks (08:25 AM - 11:45 AM)
Location: Morial Convention Center
Room: 346
Design and synthesis of new ruthenium-based catalysts for improved activity in challenging Z-selective metathesis reactions
Brendan L. Quigley, Vanessa M. Marx, Robert H. Grubbs
Our group has recently reported a series of ruthenium-based metathesis catalysts that contain a chelating NHC. These catalysts demonstrate high Z-selectivity in a variety of metathesis reactions including cross metathesis, ring-closing metathesis and ring-opening metathesis polymerization. However, the substrate scope has so far been limited to relatively unhindered olefins. In order to probe the origin of this selectivity, a series of catalysts with N-heterocyclic carbene (NHC) substituents of varying steric bulk were prepared. These catalysts were subsequently examined for improved reactivity in a range of olefins that contain bulky substituents. In addition, the mechanism of the C-H-activation step in the synthesis of such catalysts was probed through variation of the sterics and electronics of both the adamantyl and aryl NHC substituents.
Tuesday, April 9, 2013 08:00 PM
Graphene Chemistry, Metal-Mediated Reactions and Syntheses, Molecular Recognition and Self-Assembly, Physical Organic Chemistry, Materials Devices and
Switches (08:00 PM - 10:00 PM)
Location: Morial Convention Center
Room: Hall D
Transition-metal-free reductive cleavage of lignin-related C-O bonds by an activated silane
Anton A Toutov, Alexey Fedorov, Nicholas Swisher, Robert H. Grubbs
Reported herein is a transition-metal-free protocol for the efficient reductive cleavage of diaryl and aryl alkyl ethers. The combination of triethylsilane with simple bases forms an unusually powerful reductive couple that affords regioselective rupture of lignin- and coal-related C-O bonds in aromatic ethers. Interestingly, this is accompanied by ortho-directed C-H silylation that be-comes preferred with certain bases and temperature re-gimes. However, the tuning of selectivity proved possible thus enabling the development of a practical method for the title transformation, as illustrated by the reduction of lignin model compounds to their corresponding phenolic and aromatic constituents.
Monday, April 8, 2013 08:00 PM
Sci-Mix (08:00 PM - 10:00 PM)
Location: Morial Convention Center
Room: Hall D
Tuesday, April 9, 2013 02:00 PM
Advances in Energy and Fuels Processes, Systems, Materials and Utilization (02:00 PM - 04:00 PM)
Location: Morial Convention Center
Room: Hall D
Preparation of rapidly initiating ruthenium based olefin metathesis catalysts
Alexandra H. Sullivan, Benjamin K. Keitz, Robert H. Grubbs
Z-selective olefin metathesis ruthenium catalysts are highly sought after, due to their wide applications in both pharmaceuticals and materials science. A crucial step towards the preparation of rapidly initiating, Z-selective, olefin metathesis catalysts was found to be the addition of sodium pivalate to phosphonium alkyidene catalyst 1, resulting in the formation of the C-H activated complex 2 after two days of heating. Preparation of 2, a close analog to the target catalyst 4, promises that future synthesis of 4 should be facile.
Sunday, April 7, 2013 06:00 PM
Undergraduate Research at the Frontiers of Inorganic Chemistry (06:00 PM - 08:00 PM)
Location: Morial Convention Center
Room: Hall D
Catalyst-controlled anti-Markovnikov palladium-catalyzed oxidation of aliphatic olefins
Zachary K Wickens, Bill Morandi, Robert H Grubbs
The Wacker oxidation, or the palladium-catalyzed oxidation of olefins to carbonyls, is one of the most well-known palladium-catalyzed reactions and has extensive synthetic applications. Traditional Wacker oxidation conditions obey Markonikov's rule and thus yield methyl ketones with high selectivity from the majority of terminal olefins. A Wacker oxidation capable of producing aldehydes from unbiased terminal olefins would be synthetically useful and is a long-standing challenge in palladium oxidation chemistry. A palladium-catalyzed oxidation system capable of providing synthetic access to aldehydes from unbiased terminal olefins will be discussed.
Tuesday, April 9, 2013 08:20 AM
Metal Mediated Reactions (08:00 AM - 12:00 PM)
Location: Morial Convention Center
Room: 256/257
Synthetic applications of Z-selective ruthenium-based olefin metathesis catalysts
Vanessa M Marx, Myles B Herbert, Benjamin K Keitz, Robert H Grubbs
The first report of Z-selective macrocyclizations using a ruthenium-based metathesis catalyst is described. Selectivity for Z-macrocycles is consistently high for a diverse set of substrates bearing different functional groups and comprised of various ring sizes. The same catalyst was employed for the Z-selective ethenolysis of a mixture of E and Z macrocycles, providing the pure E-isomers. These methodologies were successfully applied to the construction of several olfactory macrocycles, as well as the backbone of cytotoxic alkaloid natural products. Conditions were also optimized for a series of challenging cross metathesis reactions using the same catalyst system, and subsequently exploited in the synthesis of a family of lepidopteran insect pheromones. A detailed mechanistic study probing the origin of the stereoselectivity in these challenging transformations is currently underway, and will also be discussed in detail.
Monday, April 8, 2013 01:00 PM
Metal Mediated Reactions (01:00 PM - 05:00 PM)
Location: Morial Convention Center
Room: 256/257
Functionalized corroles as diatherapeutic, multi-modal imaging agents
Melanie A Pribisko, Punnajit Lim, John Termini, Robert H Grubbs, Joshua H Palmer, Harry B Gray
Recent synthetic advancements have made it possible to produce substituted derivatives of meso-5,10,15-(tris)pentafluorophenylcorrole (H3tpfc) in reasonable yields. We present the scalable syntheses of new H3tpfc derivatives, and a few of their metal complexes, through nucleophilic aromatic substitution on the pentafluorophenyl substituents. These complexes have potential applications both as imaging agents and chemotherapeutic drugs.
Sunday, April 7, 2013 06:00 PM
Metals in Medicine: Diagnostic and Therapeutic Applications (06:00 PM - 08:00 PM)
Location: Morial Convention Center
Room: Hall D
ROMP with stable initiators
Robert Howard Grubbs
Tim Swager introduced the name ROMP for ring opening metathesis polymerization when he was a a graduate student. Since that time, many new initiators for the ROMP of strained olefins have been developed. Recent advances now allow polymers with precise chain length and composition to be prepared. The synthesis of brush polymers demonstrates the control of polymeric structures that are now possible with modern initiators.
Tuesday, April 9, 2013 02:50 PM
ACS Award for Creative Invention: Symposium in Honor of Timothy M. Swager (01:15 PM - 05:30 PM)
Location: Hilton Riverside
Room: HEC C
Z-selective ethenolysis using a ruthenium catalyst: Applications and mechanistic implications
Myles B Herbert, Hiroshi Miyazaki, Peng Liu, Vanessa M Marx, Benjamin K. Keitz, Robert H Grubbs
Unique ethenolysis reactivity has been uncovered with a new family of chelated ruthenium alkylidene catalysts that have exhibited high Z-selectivity in cross metathesis, ring opening metathesis polymerization, and macrocyclic ring closure reactions. Exposure of a mixture of cis- and trans-internal olefins to ethylene and a chelated ruthenium catalyst results in the selective ethenolysis of only the cis-isomer; this phenomenon was first reported for a Z-selective molybdenum metathesis catalyst. Applications for the resolution of trans-internal olefins have been explored particularly in the isolation of purely trans-olefin containing macrocyclic rings. Additionally, Z-selective ethenolysis is being explored as an important process in the mechanism and behavior of this family of chelated Z-selective catalysts.
Thursday, April 11, 2013 12:20 PM
Organometallic Chemistry (08:30 AM - 12:40 PM)
Location: Morial Convention Center
Room: 335/336
Asymmetric cyclic alkyl amino carbene (CAAC) ruthenium complexes as improved catalysts for ethenolysis
Vanessa M Marx, Mohand Melaimi, Robert H Grubbs, Guy Bertrand
Ethenolysis, the cross metathesis reaction of an internal olefin with ethylene to generate two terminal olefin products, has long been proposed as a method for the rapid production of commodity, value-added products from inexpensive, readily-available seed oil derivatives. For application to commodity chemicals, the TON should be at least 50,000. Prior to this report, such a catalyst system had yet to be developed. Herein, we disclose ruthenium complexes of cyclic alkyl amino carbene (CAAC) ligands bearing asymmetric ortho substitution on the N-aryl ring, as potentially viable catalyst systems for ethenolysis reactions on an industrial scale. In the ethenolysis of methyl oleate, these catalyst systems exhibit TONs > 100,000 and >90% selectivity for terminal olefins, at a loading of 3 ppm. Mechanistic investigations probing this remarkable activity are ongoing, and will also be presented in detail.
Wednesday, April 10, 2013 02:10 PM
Organometallic Chemistry (01:30 PM - 05:40 PM)
Location: Morial Convention Center
Room: 342
Initiator control of the tacticity of ROMP polymers
Robert Howard Grubbs
A variety of metal based ROMP initiators have been developed over the past several years that allow precise control of polymer structure. Recently initiators based on molybdenum and ruthenium that provide control of the double bond geometry of the resulting polymers. Many of these also provide precise control of the tacticity of the backbone. Metallocene catalysts provide good models for this control
Monday, April 8, 2013 10:00 AM
ACS Award in Applied Polymer Science: Symposium in Honor of Mitchell A. Winnik (08:55 AM - 12:00 PM)
Location: Hilton Riverside
Room: Grand Ballroom B
Milder routes to chelated ruthenium complexes for Z-selective metathesis
Lauren E. Rosebrugh, Myles B. Herbert, Vanessa M. Marx, Benjamin K. Keitz, Robert H. Grubbs
A novel method to effect the salt metathesis and C-H activation of ruthenium-based, Z-selective metathesis catalysts containing a chelated N-heterocyclic carbene (NHC) ligand using sodium carboxylates is reported. This method allows for the successful formation of stable chelated species containing a variety of alterations to the NHC ligand that had decomposed under the previous approach. As such, several new, chelated metathesis-active ruthenium complexes are described, including a catalyst system exhibiting >95% Z-selectivity and record TONs (up to 8100) in homodimerization reactions of terminal olefins. Moreover, a catalyst has been synthesized that gives highly cis, highly tactic polymers via ring opening metathesis polymerization of strained, cyclic olefins, marking the first time tactic polymers have been made using a ruthenium-based metathesis catalysts.
Monday, April 8, 2013 08:00 PM
Sci-Mix (08:00 PM - 10:00 PM)
Location: Morial Convention Center
Room: Hall D
Tuesday, April 9, 2013 06:00 PM
Organometallic Chemistry (06:00 PM - 08:00 PM)
Location: Morial Convention Center
Room: Hall D
Richard R Schrock, Ph.D.
Highly Z-selective and chemoselective olefin metathesis of 1,3-dienes: Catalytic studies and exploration of unusual intermediates
Erik M Townsend, Amir H Hoveyda, Richard R Schrock
Molybdenum and tungsten monoaryloxide pyrrolide (MAP) alkylidene complexes catalyze the Z-selective metathesis homocoupling of (E)-1,3-diene substrates to give (E,Z,E) conjugated trienes in high yield. The most effective catalysts highly prefer reaction with the terminal alkene functionality of the dienes, limiting the formation of unwanted side products. Cross metathesis of (E)-1,3-dienes with various olefinic substrates (including vinyl ethers) using the same catalyst systems selectively furnishes products containing the (E,Z) conjugated diene motif. These reactions proceed through unusual alkylidene intermediates, such as vinylalkylidenes and alkoxyalkylidenes. Isolation and characterization of vinylalkylidene and alkoxyalkylidene MAP species are reported along with investigations of their stability and reactivity.
Wednesday, April 10, 2013 12:20 PM
Organometallic Chemistry (08:30 AM - 12:40 PM)
Location: Morial Convention Center
Room: 344
Energetics and dynamics of the low-lying electronic states of constrained polyenes: Implications for infinite polyenes
Ronald L Christensen, Miriam M Enriquez, Nicole L Wagner, Alexandra Y Peacock-Villada, Corina Scriban, Richard R Schrock, Tom Polvka, Harry A F
Source: http://www.eurekalert.org/pub_releases/2013-04/acs-nla031113.php
occupy oakland occupy oakland morgellons disease arik armstead sag awards red carpet torrey pines nhl all star game 2012
No comments:
Post a Comment
Note: Only a member of this blog may post a comment.