Development of Efficient Homogeneous Gold Catalysis

University Of California-Santa Barbara, Santa Barbara CA

Investigators

Abstract

With support from the Chemical Catalysis Program of the Division of Chemistry, Dr. Liming Zhang of the University of California at Santa Barbara is developing new catalysts derived from gold. These catalysts are used to speed up chemical reactions on organic molecules with very precise control of the products formed. These catalysis reactions convert simple molecules to those of greater complexity that can then be used as building blocks in drug discovery, biomedical research, and materials science. The building these target molecules is often the most difficult part of the entire synthetic process. The research described is conducted by undergraduate and graduate students and prepares them as the next generation of the STEM workforce. Dr. Zhang is also involved in outreach efforts targeting underrepresented minorities and high school students. In addition, Dr. Zhang is incorporating gold catalysis into undergraduate laboratory courses, so that his students know of the industrial benefits of their research. This work advances the prosperity of the US by promoting innovation in industry and training of a highly technical workforce. The functionalization of C(sp3)-H bonds, especially those that are unactivated, is of great synthetic utility as it enables the streamlined synthesis of molecules of medicinal- or materials-relevance without substrate pre-functionalization. This strategy, however, is challenging to implement due to issues of reactivity and selectivity, and remains underdeveloped. Dr. Zhang is studying the chemistry of gold vinylidenes generated from the reaction of terminal ynones with gold catalysts in the presence of an electrophilic bromination reagent. These vinylidene complexes then insert into a C-H bond to form a 5- or 6-membered bromocyclopentenone or bromocyclohexenone. The use of other electrophilic reagents, the tuning of the vinylidene reactivity, and the insertion into more remote C-H bonds are also studied as these alterations provide synthetic flexibility and access to a range of valuable structures. Dr. Zhang is also studying the activation of alkynes or allenes towards electrophilic attack by gold catalysts. These are either intermolecular reactions with challenging nucleophiles, or in intramolecular reactions with heteroatom nucleophiles that produce valuable heterocycles. Enantioselective catalysis with catalysts that bear chiral phosphine or N-heterocyclic carbene ligands specifically tailored to the linear structures of gold(I) complexes are also of interest. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.