Chemical Catalysis

Special Seminar: Eleni Katifori, MPI-Goettingen

Thu, 2013-01-17 10:00
Speaker: 

Dr. Eleni Katifori

Max Planck Institute - Goettingen

 

The evolution of leaf vasculature: deciphering the design of optimal loopy architectures

 

Host: Douglas Jerolmack (Earth and Environmental Sciences)

Location: 

Lynch Lecture Hall

 

2013 Edgar Fahs Smith Lecture - Josef Michl, Univ. of Colorado

Thu, 2013-03-14 18:00
Speaker: 

Josef Michl, University of Colorado

 

Singlet Fission for Solar Cells

Location: 

Carolyn Lynch Lecture Hall

Inaugural Aldrich Distinguished Lecture

Mon, 2012-10-15 16:00
Speaker: 

Stephen L. Buchwald
Camille Dreyfus Professor of Chemistry
Massachusetts Institute of Technology

Location: 

Carolyn Lynch Lecture Hall

Palladium-Catalyzed Carbon-Nitrogen and Carbon-Carbon Bond-Forming Reactions: Progress, Applications and Mechanistic Studies

Patrick J. Walsh

Photo: 
First Name: 
Patrick J.
Last Name: 
Walsh
Official Title: 
Professor of Chemistry

Inorganic Chemistry, Organic Chemistry, Chemical Catalysis

Contact Information
Office Location: 
3001 IAST
Email: 
pwalsh@sas.upenn.edu
Phone: 
(215) 573-2875
Fax: 
(215) 573-6743
Admin Support: 
Education: 
  • Advisor Prof. K. Barry Sharpless
  • 1986 B.A. in Chemistry, University of California, San Diego
  • 1991 Ph.D in Chemistry, University of California, Berkeley
  • 1991-1994 NSF Postdoctoral Fellow Postdoctoral, The Scripps Research Institute
Research Interests: 

Research in the Walsh group merges the fields of catalysis and organic and inorganic synthesis with the goal of achieving new catalytic asymmetric transformations for the synthesis of chiral building blocks. The transformations we have chosen to study are asymmetric C-C and C-O bond forming reactions, because construction of these bonds lies at the very heart of organic synthesis. We are also interested in the development of tandem reactions that combine several steps in a single reaction vessel. By introducing tandem reactions, we can increase synthetic efficiency while reducing the number of purification steps necessary. 

 

Shown below are examples of tandem reactions developed in the Walsh group:

 

We are also interested in reaction mechanisms, which gives us the opportunity to synthesize some interesting catalysts. Shibasaki's M3(THF)n(BINOLate)3Ln (Ln = lanthanide, M = Li, Na, K) catalyst are among the most efficient known in asymmetric catalysis. We have studied the structure and reactivity of these amazing catalysts, one of which is shown below.4-6 

We are also interested in structural organozinc chemistry. The first example of zinc coordinated to C-C double bond was recently reported from our group.7 

In 2006 the Walsh group crystallographically characterized about 40 compounds, most of which contained metals.

Eric J. Schelter

Photo: 
First Name: 
Eric J.
Last Name: 
Schelter
Official Title: 
Associate Professor of Chemistry

Inorganic and Materials Chemistry

Contact Information
Office Location: 
3003 IAST
Email: 
schelter@sas.upenn.edu
Phone: 
(215) 898-8633
Fax: 
(215) 573-6743
Twitter: 
@SchelterGroup
Admin Support: 
Education: 
  • B.S. Michigan Technological University (1999)
  • Ph.D. Texas A&M University, Advisor: Kim R. Dunbar (2004)
  • Glenn T. Seaborg Postdoctoral Fellow, Los Alamos National Laboratory (2004-2005)
  • Director's Postdoctoral Fellow, Los Alamos National Laboratory (2006)
  • Frederick Reines Postdoctoral Fellow in Experimental Sciences, Los Alamos National Laboratory (2006-2009)
Research Interests: 

 

Projects in the Schelter Group involve inert atmosphere/Schlenk line synthesis of inorganic and organometallic complexes. Rigorous characterization of new compounds is achieved through X-ray crystallography, NMR, FTIR, and UV-Visible absorption spectroscopies, electrochemistry and magnetic susceptibility studies. Current projects are focused on the chemistries and electronic structure effects of the lanthanides, uranium and main group elements

Advanced Rare Earths Separations Chemistry

The rare earth elements: La-Lu, Y and Sc are used in critical renewable energy applications including wind turbine generators and hybrid electric vehicle batteries. These modern applications require pure rare earth elements that must be separated from their composite mineral sources. The Peoples Republic of China currently holds ~97% of the international rare earths market comprising nearly all aspects of the (environmentally taxing) supply chain. To develop other sources of rare earths and reduce the environmental impact of their isolation, there is a clear need for new separations chemistry that reduces the cost of industrial-scale rare earths separations. This project seeks to develop a totally new extractant strategy by harnessing the physicochemical distinctiveness of certain high-value rare earths. New designer rare earth extractants will enable selective separations chemistry for these technologically critical elements.

 

Capturing Heavy-Fermion Type Electron Correlations in Molecular Complexes

The intermetallic heavy-fermion materials, comprising intermediate valence f-elements such as cerium, are characterized by exotic emergent phenomena including unconventional superconductivity. Recent results on these materials suggest a common energy scale for the emergence of the superconducting state, dependent on the local magnetic interaction of f-moments with conduction electrons. Local electron correlations are also believed to underpin the high Tc superconductivity of other families of materials. Parallel studies in molecular chemistry have begun to show inorganic and organometallic complexes are capable of exhibiting the same type of mixed-valency and correlations found in the heavy-fermion materials.

This project will generalize the requirements for emergence of Kondo-like phenomena in magnetically-dilute molecular complexes. New materials will be synthesized from fundamental units of electron correlation to three-dimensional molecular phases.

 

 

 

Exploring the Inverse Trans Influence in the Chemistry of Uranium

Antithetical to the trans influence in transition metal chemistry, which results in a weakening of metal-ligand bonds trans to strongly-bound groups, is the inverse trans influence in the chemistry of the actinides. Semi-core p-orbital mixing with valence d- or f-orbitals gives rise to the influence, however, the presence of both orbital types in the actinide valence shell precludes its simple description. The large thermodynamic stability of the ubiquitous linear, trans-dioxo uranyl cation, UO22+ is one important consequence of this influence.

This project will develop new complexes in varying geometries and coordination environments to systematically study the inverse trans influence in the structural chemistry of uranium. These results will have direct relevance to the bio-remediation of actinide contaminated ground waters, for which the thermodynamic driving force of the influence plays an important role.

Virgil Percec

Photo: 
First Name: 
Virgil
Last Name: 
Percec
Official Title: 
P. Roy Vagelos Professor of Chemistry

Organic, Supramolecular and Macromolecular Chemistry

Contact Information
Office Location: 
4003 IAST, Lab: 4160 IAST
Email: 
percec@sas.upenn.edu
Phone: 
(215) 573-5527
Fax: 
(215) 573-7888
Admin Support: 
Education: 
  • B.S. 1969 Department of Organic and Macromolecular Chemistry, Polytechnic Institute of Jassy, Romania
  • Ph.D. 1976 Institute of Macromolecular Chemistry, Jassy, Romania
  • Postdoctoral July-August 1981 Hermann Staudinger Hause, University of Freiburg, Germany
  • Postdoctoral September 1981 - March 1982 Institute of Polymer Science, University of Akron, U.S.A.
Research Interests: 

Our research group is involved in the elaboration of synthetic methods, strategies and architectural concepts, as well as in the understanding of the fundamental principles that govern the rational design and synthesis of complex molecular, macromolecular, and supramolecular nonbiological systems that exhibit biological functions. Biological systems are employed as models to develop the synthetic architectural motifs and to control their self-assembly and self-organization during the creation of ordered systems. Our research strikes a balance among a diversity of interrelated disciplines, such as organic, bioorganic, macromolecular, and supramolecular synthesis and catalysis, seeking to understand, mimic, and extend Nature's solutions to the design of synthetic functional nanosystems. 

 

Hierarchical folding, supramolecular chirality, nonbiological ionic and electronic channels and nanowires, nanostructured supramolecular membranes, externally regulated drug release mechanisms, enzyme-like catalytic systems, and self-interrupted organic and macromolecular synthesis are examples of new concepts that are under investigation. Central to the capacity of biological molecules to perform critical functions is their ability to form highly organized and stable 3-D structures using a combination of molecular recognition processes. Therefore, the combinatorial libraries of synthetic building blocks required in our strategies consist of combinations of macrocyclic, dendritic, and other primary sequences that are able to fold into well-defined conformations and also contain all the information required to control and self-repair their secondary, tertiary, and quaternary structure at the same level of precision as in biological molecules. To what extent the delicate balance between the structures and functions evolved in Nature during billions of years can be transplanted to synthetic molecules is a fascinating question.

 

Towards these goals, we also develop new synthetic methods for the formation of carbon-carbon and carbon-heteroatom bonds using metal-catalyzed homo- and cross-coupling, radical, and various ionic and ion-radical reactions. Living and non-statistically self-interrupted polymerization methods are elaborated based on these organic reactions. The design of the internal structure of complex single molecules and the elucidation of the reactivity principles induced by the controlled environment confined within a single molecule or supramolecule are actively pursued. This research involves collaborations with structural and computational chemists and biochemists.

Gary A. Molander

Photo: 
First Name: 
Gary A.
Last Name: 
Molander
Official Title: 
Hirschmann-Makineni Professor of Chemistry and Department Chair
Contact Information
Office Location: 
4001 IAST
Email: 
gmolandr@sas.upenn.edu
Phone: 
(215) 573-8604
Fax: 
(215) 573-7165
Twitter: 
@molandergroup
Admin Support: 
Research Interests: 

 

The central theme of the Molander group's research is the development of new synthetic methods and their application to the synthesis of organic molecules. The group's focus is to expand and improve the Suzuki coupling reaction for organoboron compounds. Robust, air- and water-stable potassium organotrifluoroborates (R-BF3K), are employed to carry out couplings under relatively mild conditions using non-toxic components.

Greener Routes to Standard Reagents

The preparation of aryl- and heteroaryl potassium trifluoroborate and trihydroxyborate salts has been modified to take advantage of atom-economical boron sources, such as bis-boronic acid (BBA) and tetrakis(dimethylamino)diboron, which allow low catalyst loading and relatively mild reaction conditions. Reactive boronic acid species are generated, and subsequent coupling reactions with these substrates allow greener access to biaryl products.

 

 

Improving Transformations with More Robust Reagents

 

Organotrifluoroborates allow installation of functional groups within a molecule in the place of an existing carbon-boron bond. This allows one to prepare or purchase a simple, functionalized organotrifluoroborate and to elaborate the structure, drawing on the reactivity of the boron species. Some of the transformations carried out to date in this way are outlined below, highlighting the ability to install a cyclopropyl, hydroxymethyl, or nitroso functional group using potassium trifluoroborates.

 

 

Novel Reagents and Transformations

Some methods have been developed for the synthesis of novel reagents containing alkyltrifluoroborates, namely potassium aminomethyl-, hydroxymethyl-, and a-alkoxyalkyltrifluoroborates. The synthesis of these structures is outlined below with their applications in cross coupling illustrated.

Marisa C. Kozlowski

Photo: 
First Name: 
Marisa C.
Last Name: 
Kozlowski
Official Title: 
Professor of Chemistry

Organic and Catalysis Chemistry

Contact Information
Office Location: 
4002 IAST, Lab: 4010, 4070 IAST
Email: 
marisa@sas.upenn.edu
Phone: 
(215) 898-3048
Admin Support: 
Research Interests: 

 

The central theme of research in my laboratory is the rational design of new methods and catalysts for use in organic synthesis. As well as using traditional screening and development approaches, we employ several novel computational tools for the discovery and optimization of new reagents and catalysts. These new synthetic methods comprise the key steps in our total synthesis strategies to a variety of important pharmaceutical agents and natural products.

 

Asymmetric Oxidative C-C Bond Forming Reactions: The development of chiral catalysts for oxidative C-C bond formation is a major focus in our laboratory. In addition to the substantial potential for developing biomimetic synthetic approaches to a variety of natural products, such transformations are appealing in that C-H bonds are directly transformed to C-C bonds with an inexpensive oxidant, molecular oxygen. 

 

To this end, we developed 1,5-diaza-cis-decalin copper complexes, the catalysts of choice for the oxidative asymmetric biaryl coupling of 2-naphthol derivatives. Study of the mechanism has allowed the development of new reaction methods as well as couplings of highly functionalized 2-naphthols. With this ability, we have completed the first asymmetric synthesis of the natural product nigerone. The first total syntheses of the complex natural products cercosporin and hypocrellin have also been accomplished. These structurally novel compounds display promising photodynamic therapy profiles in cancer treatment. Future goals include exploiting the oxidative biaryl coupling method in the synthesis of chiral bisanthraquinone and naphthodianthrone natural products.

 

Reactions of α-Ketoesters and Derivatives: We have described bifunctional salen-derived catalysts that contain electronically decoupled Lewis acid and Lewis base sites. This electronic decoupling permits generation of optimally active catalysts as both the Lewis acid and Lewis base can be maximized without quenching each other. These catalysts are particularly effective for the very difficult asymmetric alkylation of α-ketoesters and α-iminoesters to yield α-hydroxy and α-amino acid adducts in enantiomerically pure form. Further studies with α-iminoesters have revealed an umpolung addition pathway allowing addition of nucleophiles to imine nitrogens. We have exploited this reactivity pattern to develop a three-component coupling that generates highly functionalized α-amino acid derivatives.

 

Computer-Aided Design of Chiral Auxiliaries and Catalysts:Diastereo- and enantioselective chemical reactions are essential components for the efficient synthesis of complex chiral targets. We have generated several computational tools to assist researchers in designing and optimizing chiral catalysts including database searching and functionality mapping. In addition, we have developed semi-empirical quantum mechanical quantitative structure selectivity (QSSR) relationships for accurate and precise enantiomeric excess predictions of chiral catalysts. In one example, we correlated the structures of various beta-amino alcohol catalysts to their enantioselectivities in the asymmetric addition of diethylzinc to benzaldehyde. With our method the selectivities of new catalysts were also calculated. Subsequent chemical synthesis and analysis of the new catalysts indicated that the model was very useful and easily distinguished catalysts of low, moderate, and high selectivity. 

Department of Chemistry

231 S. 34 Street, Philadelphia, PA 19104-6323

215.898.8317 voice | 215.573.2112 fax | web@chem.upenn.edu

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