RUI: Phosphine-Directed Carbon-Hydrogen Borylation to Access Ambiphilic Phosphine Boronates

University Of San Diego, San Diego CA

Investigators

Abstract

With funding from the Chemical Catalysis program of the Division of Chemistry, Dr. Timothy Clark of the University of San Diego is developing metal-catalyzed reactions that convert a carbon-hydrogen ("C-H") bond to a carbon-boron bond. These reactions are "directed" by a phosphorus atom (called a "phosphine") on the target molecule. This chemical reaction is unusual as C-H bonds are rather unreactive and will not undergo this change without the phosphine. The focus of this project is on using the phosphine to direct the metal catalyst to a particular C-H bond in the molecule, providing compounds that have a specific spatial relationships. By incorporating boronates into these phosphines, new reactions are developed that leverage the complementary reactivity of the phosphine and boronates. The Clark group is accessing a large variety of phosphine boronates and applying them to reactions in organic chemistry that can facilitate the synthesis of organic molecules, including those of relevance to medicinal or energy-related applications. Dr. Clark works primarily with undergraduate students. This project provide undergraduate students with research experiences, preparing them for careers in STEM fields. This research also advances the national interest by providing innovation in chemical synthesis and pharmaceutical design and development. Dr. Timothy Clark is developing phosphine-directed C-H borylation reactions and using the resulting ambiphilic phosphine boronates toward new organic and organometallic transformations. The C-H borylation reaction uses a unique cationic iridium system to catalyze the directed C-H functionalization. A detailed mechanistic study is underway to further understand the catalytic cycle and improve the system. The phosphine substrates utilized in this transformation are being expanded to include sp3-hybridized C-H bonds and to access chiral phosphine boronates. The resulting phosphine boronates are being examined as ambiphilic ligands in challenging catalytic transformations. Further functionalization of the C-B bond is also being explored to access highly-functionalized phosphines as ligands in catalysis. In addition to developing high-impact processes in the area of catalysis, a primary focus of this grant is on mentoring undergraduate students in metal-catalyzed reactions, improving the pipeline of future STEM scientists in this important area of chemistry. 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.