They are Robert H. Grubbs, Ph.D.; Richard R. Schrock, Ph.D.; Stanley B. Prusiner, M.D.; George A. Olah, Ph.D.; Alan J. Heeger, Ph.D.; and Mario J. Molina, 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.
Prusiner, who is with the University of California, San Francisco, won the 1997 Nobel Prize in Physiology or Medicine for the discovery of prions. Those infectious proteins cause a degenerative brain disorder in humans called Creutzfeldt-Jakob disease, "mad cow" disease in cattle, and related diseases in sheep and deer.
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.
Heeger, who is with the University of California, Santa Barbara, shared the 2000 Nobel Prize in Chemistry with Alan G. MacDiarmid, Ph.D., and Hideki Shirakawa, Ph.D., for the revolutionary discovery that plastics, after certain modifications, can conduct electricity. The discovery opened the way for plastic batteries, roll-up solar cells and other potential products.
Molina, who is with the University of California, San Diego, shared the 1995 Nobel Prize in Chemistry with F. Sherwood Rowland, Ph.D., and Paul J. Crutzen, Ph.D., for discovering that substances called CFCs in aerosol spray cans and other products were destroying the ozone layer. The ozone layer is crucial to life on Earth, forming a protective shield high in the atmosphere that blocks potentially harmful ultraviolet rays in sunlight.
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Abstracts
Robert H. Grubbs, Ph.D.
Biodegradable polymer scaffolds for stem-cell based treatment of age-related macular degeneration
Victoria Piunova, Paresma Patel, Chonwoo Lee, Marlene Tsie, Robert H Grubbs, Dennis O Clegg
This presentation will describe the formulation and biocompatibility testing of biodegradable polymer substrates for the treatment of age-related macular degeneration. As potential candidates two systems have been exploited: blends of poly-lactic-co-glycolic acid (PLGA)/poly-e-caprolactone (PCL) of various compositions and a random terpolymer of poly-lactide-co-glicolide-co-caprolactone (PLGC). The choice of potential substrates was governed by several criteria, excellent biocompatibility, controlled biodegradability and the presence of functionality, suitable for further modification. Scaffolds were formulated by preparing thin films of PLGA/PCL or PLGC followed by surface modification with a cyclic RGD peptide. To determine if the substrates can be applied as scaffolds for tissue engineering, their biocompatibility was examined using in vitro experiments.
Monday, August 20, 2012 8 p.m.
Sci-Mix (08:00 PM - 10:00 PM)
Location: Pennsylvania Convention Center
Room: Hall D
Tuesday, August 21, 2012 8 p.m.
Location: Pennsylvania Convention Center
Room: Hall D
Polynorbornene-polyethylene glycol based polymers as electrolyte materials for rechargeable lithium batteries
Dr. Nanditha G Nair, Dr Simon C Jones, Dr. Robert H Grubbs, Dr. Isabelle Darolles
Polymer electrolytes are a promising alternate to flammable liquid polymer electrolytes. Their use in lithium based rechargeable batteries is limited by low ion conductivity (< 10-5 S/cm) and mechanical stability. There has been considerable effort to develop dry solid polymer electrolyte materials with higher conductivities (10-4 S/cm) at room temperatures. Achieving both high conductivity and mechanical stability in a polymer is challenging. Towards that goal we have synthesized polynorbornene-polyethylene glycol based copolymers. Conductivity and mechanical properties of these materials were explored towards their use in lithum rechargeable batteries
Tuesday, August 21, 2012 05:30 p.m.
Location: Sheraton Philadelphia City Center Hotel
Room: Liberty Ballroom C/D
Rapidly crosslinkerable bio-inspired adhesives for biomedical applications
Hoyong Chung, Robert H. Grubbs
A new three component bio-inspired adhesive was synthesized. The new adhesive is a terpolymer composed of water soluble segment, interfacial segment and crosslinking segment. Strong wet adhesion properties are obtained utilizing 3,4-dihydroxy-L-phenylalanine (DOPA) moiety as the interfacial segment. Polyacrylic acid provides high water solubility, thanks to strong ionic interactions with water. Acrylic acid N-hydroxysuccinimide ester (NHS) was included in the adhesive polymer to allow rapid crosslinking with thiol terminated, 3-armed polyethylene glycol crosslinking agents. Thiol terminal PEG was designed to have bulky volume to avoid possible penetration of molecules to the cell and tissue. NHS and thiol group react very rapidly within 30 seconds to form covalent bonds. This rapid NHS-thiol group reaction formed mechanically stable crosslinked adhesives which have strong wet adhesion properties. Lap shear strength test on wet porcine skin demonstrated a 190 % increased value in adhesion strength for adhesives having the DOPA moiety. After crosslinking, adhesion enhanced by 450 % over poly(acrylic acid-co-acrylic acid NHS) and 240 % higher than uncrosslinked poly(acrylic acid-co-acrylic acid NHS-co-DOPA).
Tuesday, August 21, 2012 05:30 p.m.
Location: Sheraton Philadelphia City Center Hotel
Room: Liberty Ballroom C/D
Synthesis of large and small molecules using olefin metathesis catalysts
Robert H. Grubbs
Ruthenium based olefin metathesis catalysts have provided new routes to olefins that appear in a variety of structures. Their functional group tolerance and ease of use allow their application in the synthesis of multifunctional bioactive molecules that are being explored as pharmaceutical agents. The same systems are also useful for the synthesis of an array of new materials from multifunctional polymers to supramolecular systems. Of particular interest are brush polymer systems that phase separate into ordered structures. The long-range order of these periodic structures is controlled by the selection and ordering of the block components. We are exploring the factors that control the spacing and attempting to develop a detailed picture of the phase separation process. The catalysts can also be used to construct telechelic polymers and in the production of composite materials. Underlying these developments has been the discovery of active catalysts with controlled selectivity through the synthesis of new ligands that control the geometry of the intermediate carbene and metallacycle complexes. A recent finding has been a ligand system that controls the geometry of the double bond that is formed in the metathesis process. A particularly efficient catalyst that will dimerize olefins to the Z geometry in high yields has been developed. These systems also generate a family of high Z polymers.
Monday, August 20, 2012 04:30 p.m.
Location: Sheraton Philadelphia City Center Hotel
Room: Horizon's Rooftop Ballroom
Biodegradable polymer scaffolds for stem-cell based treatment of age-related macular degeneration
Victoria Piunova, Paresma Patel, Chonwoo Lee, Marlene Tsie, Robert H Grubbs, Dennis O Clegg
This presentation will describe the formulation and biocompatibility testing of biodegradable polymer substrates for the treatment of age-related macular degeneration. As potential candidates two systems have been exploited: blends of poly-lactic-co-glycolic acid (PLGA)/poly-e-caprolactone (PCL) of various compositions and a random terpolymer of poly-lactide-co-glicolide-co-caprolactone (PLGC). The choice of potential substrates was governed by several criteria, excellent biocompatibility, controlled biodegradability and the presence of functionality, suitable for further modification. Scaffolds were formulated by preparing thin films of PLGA/PCL or PLGC followed by surface modification with a cyclic RGD peptide. To determine if the substrates can be applied as scaffolds for tissue engineering, their biocompatibility was examined using in vitro experiments.
Monday, August 20, 2012 08:00 p.m.
Sci-Mix (08:00 PM - 10:00 PM)
Location: Pennsylvania Convention Center
Room: Hall D
Tuesday, August 21, 2012 08:00 p.m.
Location: Pennsylvania Convention Center
Room: Hall D
Design of olefin metathesis catalysts for the stereoselective ROMP of cyclic olefins
Robert H. Grubbs
The ROMP of cyclic olefins using well defined metathesis catalysts provides a route for the living synthesis of an array of functional polymers. For example, block polymers for the synthesis of nanoparticles and in applications for new bioactive materials have resulted from the control and functional group tolerance of these initiators. With the proper control of the initiating species, the polydispersity and molecular weight of the polymers can be carefully controlled. The control of the tacticity and double bond geometry have been more difficult. Recent advances in the synthesis of molybdenum, tungsten and ruthenium based Z selective catalysts has opened the possibility of excellent control of these features as well. The factors that control tacticity and double bond geometry is an old topic in ROMP. The new systems will allow the factors that control these features to be examined.
Monday, August 20, 2012 10:25 a.m.
Location: Sheraton Philadelphia City Center Hotel
Room: Horizon's Rooftop Ballroom
Richard R. Schrock, Ph.D.
Convergent total synthesis of (+)–neopeltolide
Miao Yu, Richard Schrock, Amir Hoveyda
(+)-Neopeltolide is a marine macrolide that exhibits potent in vitro antiproliferative activity against several cancer cell lines as well as a potent antifungal activity. A concise and convergent total synthesis of (+)-neopeltolide macrolactone is achieved (the longest linear sequence 9 steps, 14 steps from commercially available compounds, shorter than other reported routes). The synthesis involves an N-heterocyclic carbene-catalyzed enantioselective boron addition and a Mo-catalyzed enantioselective ring-opening/cross-metathesis as key steps. Different from strategies in previous reports of neopeltolide and leucascandrolide syntheses, the oxazole-containing side chain of the natural product is constructed by two sequential Mo-catalyzed Z-selective alkene cross-metathesis reactions.
Sunday, August 19, 2012 08:00 p.m.
Location: Pennsylvania Convention Center
Room: Hall D
Efficient Z- and enantioselective ring-opening/cross-metathesis (ROCM) reactions promoted by stereogenic-at-Mo complexes
Miao Yu, Ismail Ibrahem, Masayuki Hasegawa, Richard R Schrock, Amir H Hoveyda
The first examples of catalytic enantioselective ring-opening/cross-metathesis (EROCM) reactions with enol ethers are reported. Efficient EROCM reactions of several oxa- and azabicycles, cyclobutenes and a cyclopropene proceed readily in the presence of 0.15-3 mol % of a stereogenic-at-Mo complex. The enantiomerically enriched disubstituted enol ethers are generated in high Z-selectivity. Functionalization of the enol ether can be easily differentiated from the terminal alkenes, which affords useful intermediates for chemical synthesis. In certain cases, enantioselectivity depends on cross partner concentration: larger equivalents of enol ethers generate the product with high enantioselectivity (versus near racemic products with one equivalent). Further mechanistic studies reveal that the length of reaction time can be critical to product enantiopurity: high selectivity obtained after 30 seconds can be nearly eroded within 30 minutes.
Sunday, August 19, 2012 01:20 p.m.
Location: Pennsylvania Convention Center
Room: 204 A
Stereoselective ROMP by Mo and W monoalkoxide pyrrolide (MAP) initiators
Professor Richard R Schrock
Ring-opening metathesis polymerization by monoalkoxide pyrrolide (MAP) initiators of Mo and W produces both cis,syndiotactic and trans,isotactic polymer sequences from enantiomerically pure monomers. Cis,syndiotactic and trans,isotactic structures for (+)-DCMNBE (2,3-dicarbomethoxynorbornene) made with Mo(NAd)(CHCMe2Ph)(pyr)(HMTO) (1a ) as the initiator (Ad = 1-adamantyl, HMTO = 2,6-dimesitylphenoxide, Pyr- = NC4H4-) arise from two mechanisms. Formation of trans,isotactic-poly[(+)-DCMNBE] can best be rationalized by invoking a fluxional process in the five-coordinate intermediate metallacyclobutane that consists of a turnstile pseudorotation in which the configuration at the metal center is retained. In other circumstances pseudorotation exchanges aryloxide and pyrrolide ligands and accounts for formation of cis,syndiotactic structures with inversion at the metal center.
Monday, August 20, 2012 01:45 p.m.
Location: Doubletree by Hilton Philadelphia Center City
Room: Aria A/B
Molybdenum and tungsten olefin metathesis catalysts containing a 2,6-dimesitylphenylimido ligand
Laura Gerber, Richard R Schrock
Molybdenum and tungsten alkylidene compounds containing the bulky 2,6-dimesitylphenylimido ligand have been synthesized. A novel synthetic route has been developed that utilizes intermediate species that contain two imido ligands with different substituents. Bispyrrolide species can be synthesized catalyst precursors. From the bispyrrolide compounds, monoalkoxide pyrrolide (MAP) species can be synthesized by addition of one equivalent of alcohol. Study of the effect of the 2,6-dimesitylphenylimido ligand on alkylidene isomerism and on olefin metathesis will be presented, with an emphasis on the selectivity of ring-opening metathesis polymerization.
Sunday, August 19, 2012 04:20 p.m.
Location: Pennsylvania Convention Center
Room: 202 A
Stanley B. Prusiner, M.D.
Effects of polyoxometalate speciation on infectious prion protein isolation
Dana J Levine, Lillian E Falese, Jan Stöhr, Holger Wille, Stanley B Prusiner, Jeffrey R Long
The Keggin-type polyoxometalate phosphotungstate anion (PTA) is used to isolate the infectious isoform of the prion protein (PrPSc) from brain tissue, but the mechanism behind this precipitation is not fully understood. In order to probe the nature of the PTA-PrPSc interaction under physiological conditions, solutions of PTA have been extensively characterized by electrospray-ionization mass spectrometry and nuclear magnetic resonance, revealing substantial changes in polyoxometalate speciation as a function of pH. The lacunary [PW11O39]7- complex was identified as a dominant species at neutral pH, and additional products resulting from the decomposition of the parent [PW12O40]3- anion are also under investigation, including orthotungstate ([WO4]2-) and larger paratungstates ([W7O24]6-, [H2W12O42]10-). The biological performance of the relevant polyoxometalate species has been evaluated through enzyme-linked immunosorbent assays, immunoblotting, X-ray fiber diffraction, and electron microscopy. These studies will aid in the optimization of isolation techniques for ongoing efforts to elucidate the structure of PrPSc.
Tuesday, August 21, 2012 04:00 p.m.
Location: Pennsylvania Convention Center
Room: 126 B
George A. Olah, Ph.D.
Direct practical method for the synthesis of β-fluorinated amino esters
Professor G. K. Surya Prakash, Laxman Gurung, Thomas Mathew, Professor George A. Olah
Owing to the unique properties of the fluorine atom, fluorinated compounds have attracted much attention in the recent years. Due to their potential applications in the area of medicinal chemistry and pharmaceuticals, a number of synthetic methods have been developed for the synthesis of b-fluorinated amino acids and esters. Herein, we report a new and practical approach towards the synthesis of b-fluorinated amino esters from readily available starting materials by a multicomponent approach. This straightforward route to b-fluorinated amino esters represents an elegant method from simple molecular units. A series of b-fluorinated amino esters have been synthesized.
Wednesday, August 22, 2012 07:00 p.m.
Location: Pennsylvania Convention Center
Room: Grand Ballroom PCC
Domino approach of Heck coupling for the synthesis of fluorinated and nonfluorinated styrenes
Professor G K Surya Prakash, Dr. Parag V Jog, Ms Hema S Krishnan, Professor George A Olah
A domino approach of Heck coupling was used to synthesize various fluorinated as well as nonfluorinated styrene derivatives from aryl halides in good to excellent yields. Each of the methods discussed is an example of a "domino" approach where more than one synthetic transformation is carried out in one pot. These new synthetic methodologies have various advantages over previously known methods in terms of use of "green" solvent, water (for nonfluorinated styrenes) and absence of gaseous reagents such as 3,3,3-trifluoropropene and 1-fluoroethene (for fluorinated styrenes). In addition, these methods have phosphine-free catalytic systems, shorter reaction times and absence of any additives.
Wednesday, August 22, 2012 02:40 p.m.
Location: Pennsylvania Convention Center
Room: 204 B
Selective decomposition of formic acid to hydrogen and carbon dioxide in the presence of ruthenium hydrido carbonyl complexes
Jotheeswari Kothandaraman, Miklos Czaun, Alain Goeppert, Robert May, G. K. Surya Prakash, George A Olah
Formic acid (FA) has been suggested as a non-toxic and non-flammable hydrogen carrier material, which can be used in a carbon neutral cycle to store energy. It can be decomposed via two pathways: decarbonylation and decarboxylation. Selective decomposition of FA to H2 and CO2 mixture with no trace of CO is quite useful as the gas stream can be directly used in H2/O2 fuel cells without poisoning of the anode catalyst. In this study, the commercially available carbonylchlorohydrido[bis(2-(diphenylphosphinoethyl)amino]ruthenium(II) complex (Ru-MACHOTM) was explored as a homogenous catalyst for the selective decomposition of formic acid to H2 and CO2. The study of the reaction mixture by spectroscopic methods, such as, FTIR, 1H NMR and 13C NMR revealed the in situ formation of carbonyl and hydride species. The chemical composition of the gas evolved in the course of the reaction was determined by GC and FTIR. A plausible mechanism for the catalytic decomposition of FA to H2 and CO2 will be discussed.
Tuesday, August 21, 2012 06:00 p.m.
Location: Pennsylvania Convention Center
Room: Hall D
Alan J. Heeger, Ph.D.
Evolution of high performance organic solar cells at UCSB: From Lewis acid-base adducts to solution processed small molecule solar cells with power conversion efficiencies of 7%
Gregory C Welch, Alan J Heeger, Guillermo C Bazan
Solution processed organic photovoltaic devices (OPVs) have emerged as a promising energy technology due to their ease of fabrication, potential to enable low-cost manufacturing, and ability to be incorporated onto light-weight flexible substrates. The most successful class of OPV devices are those with active layers composed of blended molecular or polymeric electron donor and fullerene acceptor, widely known as bulk heterojunction (BHJ) solar cells. Recently, we have reported on the synthesis of a new class of molecular donors with favorable optical and electronic properties for use in OPV devices. When coupled with the electron acceptor [6,6]-phenyl-C71-butyric acid methyl esters PC71BM, record power conversion efficiencies (PCE) approaching 7% have been realized. This presentation will describe how these new molecular donor materials came to be and the key parameters for achieving high PCEs.
Sunday, August 19, 2012 09:35 a.m.
Location: Pennsylvania Convention Center
Room: 118C
Mario J. Molina, Ph.D.
Presidential Plenary Keynote: "Chemistry and Climate Change"
Mario J. Molina
Molina will speak about new scientific analysis that strengthens the view that record-breaking summer heat, crop-withering drought and other extreme weather events in recent years do, indeed, result from human activity and global warming.
Monday, August 20, 2012 11:00 a.m.
Location: Philadelphia Marriott Downtown
Room: Liberty Ballroom C (Level 3)
