Research Expertise and Interest
organometallic chemistry, organic, development of new synthetic methods, enantioselective catalysts, strategies for the synthesis of natural products, synthesis of complex molecules, formation of carbon-carbon and carbon-heteroatom bonds, olefins, Supramolecular Chemistry, redox flow batteries, medicinal chemistry, bioconjugation, homogeneous catalysis, heterogeneous catalysis, biomass, fluorination
Research Description
Gold Catalysis
Our research efforts have profoundly impacted the development of gold(I)-catalyzed reactions. We enumerated the concept of addition/back-donation that is now heavily employed as a method to generate gold-carbenoid reactivity from alkynes and we described the dual activation paradigm that forms the basis many gold-catalyzed reactions currently being explored by many groups. We have played a leading role in the development of enantioselective catalysis with gold(I) and were among the first to employ gold complexes as catalysts for the oxidative functionalization reactions. We demonstrated that reductive elimination from diarylgold(III) complexes can be remarkably fast and subsequently applied our findings to a non-oxidative gold-catalyzed cross-coupling reaction. More recently, we reported the oxidative addition of gold(I) to strained carbon-carbon bonds giving tunable, stable gold(III) complexes. Moreover, during the exploration of reductive elimination of trifluoromethylgold(III) complexes, the we uncovered a new mechanism for the formation of trifluoromethyl-carbon bonds that allows for the introduction of an 18F-radiolabel
Chiral Anion Catalysis.
In 2007, we reported the first highly enantioselective transition metal-catalyzed reaction in which a chiral anion was solely responsible for the enantioinduction. This concept was subsequently applied to an enantioselective addition to cationic intermediates. Building on these concepts, in 2011, we applied chiral anions to the first highly enantioselective fluorination of alkenes. In this work, we illustrated a conceptually novel approach to asymmetric catalysis using anionic solid-to-liquid phase transfer catalysis. We have also developed a conceptually novel approach for the enantioselective functionalization of carbon-carbon π-bonds using chiral dithiophosphoric acids as Brønsted acid catalysts. This approach provides the first examples of enantiocontrol of Markovnikov addition to olefins without the use transition metal catalysts. Additionally, we established a collaboration with the Sigman group (University of Utah) to use these reactions as a launching point for our work in data driven discovery of catalysts and reactions.
Supramolecular Catalysis
In collaboration with Profs. Raymond and Bergman (UC Berkeley) , we have demonstrated that reactions can be carried out in water (and accelerated) by encapsulation of the catalyst in an anionic M4L6-type supramolecular assembly (ref 4a). We have also shown that encapsulation increases the stability of the catalysts in the presence of biological catalysts and therefore provides a strategy for carrying out tandem gold-enzyme catalyzed processes. Additionally, we have shown that supramolecular catalysis can accelerate elementary steps important in homogeneous catalysis and showed for the that these two types of catalysis can be combined to generate new reactivity. More recently, we have demonstrated that catalysis in the supramolecular host confers unique selectivity on traditional homogeneous catalyzed reactions, such as hydrogenation.
Heterogeneous Catalysis
In 2010, in collaboration with the Somorjai group (UC Berkeley) , we reported one of the first examples of in situ modification of heterogeneous transition catalyst to provide electrophilic heterogeneous catalysts for the addition of nucleophiles. We have gone onto develop tools for the in situ study of these and other heterogeneous catalysts, including a collaboration with Elad Gross (Hebrew University) developing AFM-IR for studying heterogeneous catalysis. We have also integrated heterogeneous catalyst with biological catalysts to generate process for the conversion of biomass to fuels and chemicals.
Bioconjugation
We are interested in the devlelopment of catalysts and reagents for the selective functionalization of complex biological molecules. To this end, we collaborated with the Chang group (UC Berkeley) to develop a reagent for selective functionalization of methionine residues in proteins. We have applied these reactions to the formation of antibody-drug conjugates (ADCs) and to proteomics.
