CAS: Catalytic Synthesis via Small Molecule Evolution

University Of Kansas Center For Research Inc, Lawrence KS

Investigators

Abstract

With the support of the Chemical Synthesis Program in the Division of Chemistry, Professor Jon Tunge of the University of Kansas is studying the development of strategies that harness the inherent energy in molecules to enable efficient and environmentally sustainable processes for chemical manufacturing. Specifically, the release of small stable molecules (carbon dioxide and/or hydrogen) from simple feedstocks, sometimes in combination with harvesting light energy, will provide the energy to drive chemical reactions without the need for traditional, more wasteful, methods of energy input. To further lessen the environmental impact of the chemistry while also allowing for the exploitation of new types of reaction pathways, catalysts based on cobalt, an earth abundant metal, rather than traditional more expensive and rare precious metals, will be employed as critical promoters. It is anticipated that the methods developed will be applicable to the synthesis of a wide variety of materials with potential applications as pharmaceutical agents, agrochemicals, and other substances of value to science, engineering, and commerce. The broader impacts of the funded project extend to the benefits accrued to society as Professor Tunge and his coworkers engage in outreach and educational activities designed to integrate the goals of this research with training and recruitment programs that incorporate the promotion of 'green chemistry' principles. A significant goal of these activities will be to attract students from diverse backgrounds, including individuals belonging to groups underrepresented in science, technology, engineering, and mathematics (STEM) fields, to address contemporary challenges in sustainable chemistry. The funded project is focused on the development of chemical transformations based on the catalytic generation of reactive intermediates via the cleavage of C–C and C–H bonds. The catalytic pathways being developed utilize decarboxylation to provide an efficient strategy for the in situ formation of synthetically useful reactive intermediates directly from inexpensive carboxylic acids. Other processes under investigation utilize the hydrogen evolution reaction (HER) for atom-economical functionalization. Cobalt catalysts replace traditional, expensive, palladium catalysts in decarboxylative coupling reactions and are anticipated to allow for new transformation types that are inaccessible using current technologies. Additionally, photoredox-catalyzed hydrogen evolution will allow for the site-specific functionalization of amino acids and peptides, while also enabling regiocontrolled decarboxylative Heck-like acylations. These studies will advance a general paradigm for synthetic chemists to use for accessing reactive species under mild conditions, while generating minimal waste using: (1) visible light photoredox catalysts for redox shuffling of transition metal catalysts, and (2) hydrogen evolution to allow oxidative couplings through liberation of the smallest molecule, hydrogen. 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.