Using Solvent-Free Mechanochemistry to Improve the Selectivity of Traditional Solution Based Chemical Reactions

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In this project, funded by the Chemical Synthesis Program of the Chemistry Division, Professor James Mack II of the Department of Chemistry at the University of Cincinnati is developing environmentally benign ways to conduct organic synthesis. Solvents, typically volatile organic compounds, represent roughly 85% of the total mass used in pharmaceutical manufacturing. As a result, many companies have developed guidelines to ensure the utilization of environmentally benign solvents in the synthesis of drugs. In addition to the amount of waste produced using solvents, solvents themselves are costly to acquire. The goal of this project is to understand how to conduct chemical reactions in the absence of such solvents in order to significantly reduce the total amount of harmful waste produced during a chemical reaction. The method of mechanochemistry used in this project can be performed by scientists at various levels, making it a useful tool to introduce the concepts of green chemistry to a broad audience. Professor Mack II has an excellent history of mentoring students from underrepresented minority groups and is continuously reaching out to the community and the students with the support of this grant. In addition to environmental concerns, there are other significant benefits of performing solvent free mechanochemistry. In solution, the rate and selectivity of a reaction are both tied to temperature; however, under solvent-free mechanochemical conditions the rate and temperature can be independent of each another. In this project, increased selectivity of chemical reactions will be performed through unique control over the temperature, mixing, and redox potential of reagents. In solution, there is limited control on the mixing rate of reagents which can have a significant effect on the overall kinetics and selectivity of a chemical reaction. This project seeks to understand how greater control over mixing in a solvent-free system can affect the kinetics and selectivity of various chemical reactions. Using examples of enantioselective versions of the Morita-Baylis Hillman reactions, a three-component coupling reaction and a Diels-Alder reaction, new methods of selectivity are expected to be observed under mechanochemical conditions that are not available to synthetic chemists in solution.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.