INDIANAPOLIS, Sept. 8, 2013 — New discoveries from the labs of several Nobel laureates will be presented here this week during the 246th National Meeting & Exposition of the American Chemical Society (ACS), the world's largest scientific society. Research from the laureates' teams will be among almost 7,000 presentations during the event.
They are Ei-ichi Negishi, Ph.D.; Richard Schrock, Ph.D.; George A. Olah, Ph.D.; and Roald Hoffmann, Ph.D.
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.
Schrock, who is with the Massachusetts Institute of Technology, shared the 2005 Nobel Prize in Chemistry with Yves Chauvin and Robert H. Grubbs, Ph.D., 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.
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.
Hoffmann, who is with Cornell University, shared the 1981 Nobel Prize in Chemistry with Kenichi Fukui, Ph.D., for their theories on how chemicals combine and form different substances. Such changes play a vital role in forming new compounds from natural raw materials, such as using petroleum to make plastics.
Press conferences on this topic will be held Sunday, Sept. 8, at 9 a.m., and on Monday, Sept. 9, at 10 a.m. in the ACS Press Center, Room 211, in the Indiana Convention Center. Reporters can attend in person or access live audio and video of the event and ask questions at http://www.ustream.tv/channel/acslive.
Abstracts of the presentations appear below.
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.
Abstracts
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, xu197@purdue.edu, Akimichi Oda, Hirofumi Kamada, Ei-ichi Negishi. Department of Chemistry, Purdue University, West Lafayette, IN 47907, United States
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 strategyhas been developed. The utility of this new synthetic method for the total synthesis of natural products of biological and medicinal importance will also be discussed.
Richard Schrock, Ph.D.
Fundamental studies of the rearrangement and isomerization of high oxidation state Mo compounds relevant to ring-opening metathesis polymerization
Stefan M Kilyanek, smkilyanek@gmail.com, Richard R Schrock. Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, United States
The structures of Mo alkylidene initiators for ring-opening metathesis polymerization (ROMP) have a drastic impact on the structure and properties of the polymers formed. The mechanisms of ROMP initiation and propagation have been studied for both Mo monoaryloxide pyrrolide (MAP) imido alkylidenes and Mo bis-alkoxide imido alkylidenes. The mechanism for isomerization / rearrangement of the intermediate species during propagation was found to have a dramatic effect on the polymer structure. The structure and reactivity of disubstituted alkylidenes was investigated to identify the species that are relevant to the rearrangement mechanism of Mo(IV) species that initiate ROMP.
Synthesis of new Mo and W olefin metathesis catalysts
Richard R Schrock, rrs@mit.edu, Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
BisDFTO alkylidene complexes of molybdenum Mo(NR)(CHCMe2Ph)(DFTO) 2 (R = 2,6-i-Pr2C6H3, 2,6-Me2C6H3, C6F5 and 1-Adamantyl; DFTO = 2,6-(C6F5)2C6H3O) and monoaryloxide monopyrrolide complexes Mo(NR)(CHCMe2Ph)(Me2Pyr)(OAr) (R = C6F5, OAr = DFTO and 2,6-dimesitylphenoxide (HMTO); R = 2,6-Me2C6H3, OAr = DFTO) have been prepared in good yields. Addition of dicarbomethoxynorbornadiene (DCMNBD) to bisDFTO complexes led to the formation of polymers that have a cis,isotactic structure. Polymerization of DCMNBD by Mo(NC6F5)(CHCMe2Ph)(Me2Pyr)(HMTO) gives a polymer that contains the expected cis,syndiotactic structure, but polymerization of DCMNBD by Mo(NR)(CHCMe2Ph)(Me2Pyr)(DFTO) (R = C6F5 or 2,6-Me2C6H3) generates a polymer that has a cis,isotactic structure, the first observation of a cis,isotactic structure employing a MAP initiator. Mo(NR)(CHCMe2Ph)(DFTO) 2 also generates cis,isotactic-polyDCMNBD. Norbornene is polymerized to give highly tactic cis-polyNBE. Addition of ethylene to Mo(NR)(CHCMe2Ph)(DFTO) 2 leads to formation of Mo(NR)(CH2CH2)(DFTO) 2, which also behaves as an initiator for polymerization of DCMNBD to cis,isotactic-polyDCMNBD and norbornene to cis highly tactic polyNBE. Mo(NR)(CH2CH2)(DFTO) 2 reacts with 3-methyl-3-phenylcyclopropene (MPCP) to give Mo(NR)(CHCHCMePh)(DFTO) 2 which behaves as an ROMP initiator for MPCP.
Synthesis of precision ROMP polymers
Richard R Schrock, rrs@mit.edu, Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
Mo and W catalysts can be designed for synthesis of ROMP polymers with a single structure. Some recent advances in this area will be presented.
George A. Olah, Ph.D.
Nucleophilic trifluoromethylation of carbonyl compounds: Trifluoroacetaldehyde hydrate as a trifluoromethyl source
G. K. Surya Prakash, Zhe Zhang, zhangzhe@usc.edu, Fang Wang, Socrates Munoz, George A. Olah. Department of Chemistry, Loker Hydrocarbon Institute, Los Angeles, CA 90089, United States
A feasible nucleophilic trifluoromethylating protocol has been developed using trifluoroacetaldehyde hydrate as an atom economical trifluoromethyl source. DFT calculations have been performed to provide mechanistic insight into the present and related reactions.
Polymer based formic acid complexes: Convenient reduction systems
G K Surya Prakash, Thomas Mathew, tmathew@usc.edu, George A Olah. Loker Hydrocarbon Research Institute, University of Southern California, Los Angeles, CA 90089, United States
The solid donor-accepter complex prepared from formic acid and solid amine polymer carries a large amount of formic acid. The free flowing solid makes its practical application more convenient in various reduction processes. The reduction of phenylacetylenes, chalcones, stilbenes, ketones etc. can be efficiently carried out using solid amine based formic complexes with Pd/C. Studies on its reactivity, selectivity and its synthetic utility will be discussed.
Deoxygenation of aromatic ketones by solid formic acid equivalent with Pd/C
G K Surya Prakash, Laxman Gurung, lgurung@usc.edu, Thomas Mathew, George A Olah. Loker Hydrocarbon Research Institute, University of Southern California, Los Angeles, CA 90089, United States
The reduction of aromatic ketones to their corresponding hydrocarbons is a widely used reaction. To avoid the difficulties associated with the use of conventionally employed reagents such as concentrated HCl, hydrazines and H2gas for this transformation, we have developed a polymer based solid formic acid complex which has high formic acid content. The synthetic utility of the formic acid equivalent solid complex has been demonstrated in its application in the Pd catalyzed direct reduction of aromatic ketones to their corresponding hydrocarbons.
Insight into the hydrogen generation from formic acid in the presence of Ru-phosphine complexes
Miklos Czaun, czaun@usc.edu, Alain Goeppert, Jotheeswari Kothandaraman, Robert B. May, J. K. Surya Prakash, George A Olah. Department of Chemistry, Loker Hydrocarbon Research Institute, United States
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.
Formic acid (FA) has been proposed as a practically non-toxic, non-flammable hydrogen storage/energy storage media that can be synthesized from CO2 by direct electrochemical reduction or by catalytic hydrogenation. When energy is needed, FA can be decomposed to carbon dioxide and hydrogen and latter converted to electricity in a hydrogen/air fuel cell. When excess energy is available the recycled CO2 is converted to FA, making the energy storage cycle carbon neutral.
Combined steam and carbon dioxide reforming of methane and natural gas at high pressures: Bi-reforming
Alain Goeppert, goeppert@usc.edu, Miklos Czaun, czaun@usc.edu, Robert B May, Surya G.K. Prakash, George A Olah. Loker Hydrocarbon Research Institute, University of Southern California, Los Angeles, CA 90089, United States
A catalyst based on NiO/MgO was shown to be active for the combined steam and dry reforming of methane and natural gas at pressures up to 42 bar. By adjusting the CO2 to steam ratio in the gas feed, the H2/CO ratio in the produced syn-gas could be easily adjusted in a single step to the desired value of 2, ideal for methanol synthesis. The observed conversion of CH4/natural gas and CO2 remained very stable for extended time on stream (up to 320 hours). In accordance with the thermodynamics of the reaction, these conversions decreased with increasing pressure. Increasing the reaction temperature and/or amount of steam and CO2 in the gas feed on the other side increased the CH4/natural gas conversion, which could in part counter the effect of higher pressure.
Roald Hoffmann, Ph.D.
Old concepts, coming into focus
Roald Hoffmann, rh34@cornell.edu, Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, United States
There would seem to be nothing more basic in coordination chemistry than that a sine qua non for a ligand is that it be a Lewis base. Yes, ligands that bond just as Lewis acids -- H+, BR3, etc are known. But a simple ligand doing one and the other? A recent study by Andrey Rogachev in our group shows clearly how I2 sometimes bonds as a base, a donor, and sometimes as an acid, an acceptor (as suspected by others). With quite specific and different geometrical consequences. What other ambiphilic ligands are out there?
Another time-honored idea, of crystal field and molecular orbital theory, is that in an octahedral environment the characteristic level splitting is t2g below eg. Could one reverse this splitting, with ligands that are super σ donors? Our struggle with this idea will be discussed.