Chemistry of Skin-Inspired Flexible and Stretchable Electronic Materials
Skin is the body’s largest organ, and is responsible for the transduction of a vast amount of information. This conformable, stretchable and biodegradable material simultaneously collects signals from external stimuli that translate into information such as pressure, pain, and temperature. The development of electronic materials, inspired by the complexity of this organ is a tremendous, unrealized materials challenge. However, the advent of organic and carbon-based electronic materials may offer a potential solution to this longstanding problem. In this talk, I will describe organic and carbon nano electronic materials to mimic skin functions. These new materials enabled unprecedented performance or functions in medical devices, energy storage and environmental applications.
Synthetic biology approaches to new chemistry
Living systems have evolved the capacity to carry out many chemical transformations of interest to synthetic chemistry if they could be redesigned for targeted purposes. However, our ability to mix and match enzymes to construct de novo pathways for the cellular production of small molecule targets is limited by insufficient understanding how chemistry works inside a living cell. Our group is interested in using synthetic biology as a platform to study how enzymes function in vivo and to use this understanding to build new synthetic pathways for the production of pharmaceuticals, nanomaterials, and fuels using living cells.
Low molecular weight, chiral organic molecules possessing distinct hydrogen-bond donor motifs have been shown to catalyze an array of C–C and C–heteroatom bond-forming reactions with high enantioselectivity and broad substrate scope. In particular, dual hydrogen bond donors such as ureas, thioureas, squaramides, and guanidinium ions have been studied in detail in the context of electrophile activation. These catalysts operate by either of two, fundamentally different modes of electrophile activation: 1) direct hydrogen bonding to a neutral electrophile, and 2) anion binding to generate chiral ion pair. We have applied the latter reactivity concept to several classes of cationic electrophiles that have presented long-standing challenges to asymmetric catalysis.
In this lecture, I will describe detailed kinetic and mechanistic studies catalytic anion-abstraction processes. These investigations have revealed unexpected cooperative mechanisms, and new strategies for the design of highly efficient catalysts. The talk will conclude with the application of these insights to the discovery of novel glycosylation catalysts.
Richard R. Schrock
Recent Advances in Olefin Metathesis by Molybdenum and Tungsten Catalyst
One of the most important developments in the last five years in olefin metathesis chemistry with high oxidation state Mo or W catalysts has been development of M(NR)(CHCMe2R')(OR)(Pyrrolide) (MonoAlkoxidePyrrolide or MAP) complexes, especially those in which OR is a sterically demanding terphenoxide such as 2,6-dimesitylphenoxide (OHMT). MAP complexes under the right circumstances have proven to be Z-selective in a variety of olefin metathesis reactions, among them enantioselective ring-opening/cross metatheses, ROMP to givehighly stereoregular polymers, ethenolysis of internal olefins such as oleates, coupling of terminal olefins, cross coupling of terminal olefins, and synthesis of macrocyclic natural products. Recent applications of metathesis in polymer chemistry includes stereoregular ring-opening metathesis polymerization to give cis,isotactic or cis,syndiotactic polymers as well as alternating AB copolymers. Tungsten oxo alkylidene complexes are a potentially important new category of catalysts because they can be "activated" by binding B(C6F5)3 to the oxo ligand and are likely to be analogs of metathesis catalysts found in classical metathesis catalyst systems. The most recent advance includes Z-selective and E-selective reactions with electron-poor olefins such as cis or trans ClCH=CHCl or (CF3)CH=CH(CF3) by Mo(NR)(CHCMe2R')(OR)(Cl)(donor) (MAX) initiators. The most desirable catalysts, dissolved in a paraffin tablet that can be handled and weighed in the air, are now commercially available in increasing variety for various applications.
Ligand-Accelerated C-H Activation Reactions: Distance and Geometry
Two different classes of novel ligands are developed to drastically accelerate Pd- catalyzed C–H activation reactions. These ligands enable the activation of C–H bonds that are near or far from a functional group, demonstrating the feasibility of achieving selectivity by recognizing the distal and geometric relationship between different C–H bonds and existing functional groups. Enantioselective C–H activation reactions are also made possible by using chiral version of these ligands, providing new disconnections for asymmetric synthesis.
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