SusChem-GOALI: Sustainable C-H Borylation

Michigan State University, East Lansing MI

Investigators

Abstract

With this GOALI award, the Chemical Catalysis Program of the Division of Chemistry is funding Professors Milton Smith and Robert Maleczka of Michigan State University and Jossian Oppenheimer of Dow Chemical Company to develop new catalytic reactions that form carbon-boron bonds. Molecules with boron-carbon bonds are valuable building blocks in pharmaceutical, agrochemical, and specialty electronics industries. They can be directly synthesized by reacting boron-containing compounds and carbon-hydrogen bonds in a process called carbon-hydrogen borylation. The most efficient and robust catalysts for carbon-hydrogen borylation utilize iridium, which is the least abundant metal in the Earth's crust. For sustainable practice using iridium, it is critical to recycle the metal and the ligands involved in the catalysis. There are two challenges in improving the sustainability of this chemistry. The first pertains to the abundance of iridium, and this university-industry collaborative group is focusing on improving the iridium recycling in the catalytic process. The second challenge pertains to the boron reagents used in carbon-hydrogen borylation. These compounds are currently made using lengthy processes that utilize hazardous reagents and generate considerable chemical waste. This group is working on developing "greener" approaches to synthesizing these boron reagents with the goal of reducing waste, improving safety, and lowering costs. The chemistry developed in this research could be broadly adopted both in scientific research as well as in commercial applications. Students participating in this research project are experiencing the work environment and practices in an industrial research and development setting. The team is exploring various strategies to recycle the metal and ligand in carbon-hydrogen borylation, including supporting catalysts on surfaces with the aim of translating selectivities in homogeneous catalyst systems to heterogeneous ones. New ligands are being synthesized to modulate the reactivity and selectivity of the catalyst and to anchor catalysts on a silica surface. Catalysts are being characterized and the reaction chemistry is being quantified using an array of analytical techniques. The team is also exploring strategies to develop more facile syntheses of the boron reagents that are used in stoichiometric amounts in the carbon-hydrogen borylation chemistry. New approaches to boron-boron bond formation are being developed to minimize the number of steps and improve the scalability of current synthetic routes to this class of reagents, and smaller alkoxide ligands on the boron center are being examined in hopes of making the boron reagents cheaper and easier to obtain. Both research aims are critical to improving the sustainability of carbon-hydrogen borylation and could be broadly adopted both in scientific research as well as in commercial applications.