SusChEM: CAREER: Synthesis of Macrocyclic Carbene Complexes for Catalytic Aziridination

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The Chemical Catalysis Program of the NSF Division of Chemistry supports the research efforts of Professor David M. Jenkins of the University of Tennessee at Knoxville (UTK) to explore new aziridination reactions using organic azides (both aryl and alkyl variants) as the nitrene source and alkenes as the carbon source. This innovative reaction involves novel transition metal complexes supported by strong sigma-donor macrocyclic tetra-N-heterocyclic carbenes (NHCs) as auxiliary ligands which act as homogeneous azirdination catalysts. The research is accomplished in four steps: ligation of tetracarbenes to first and second row transition metals (especially iron), catalytic studies of aziridination reactions between organic azides and alkenes, mechanistic studies of the reaction through probes of intermediates (i.e., metal imide complexes), and expansion of substrate scope to make the reactions relevant to industrial, pharmaceutical, and biological applications. The broader impacts of this work include providing opportunities for pre-college scholars from Central High School (CHS), an economically-disadvantaged high school in Knoxville, TN, to perform research at the UTK. With the assistance of high school teachers at CHS and collaborators in the Knox County School District, new Advanced Placement (AP) laboratories that match Professor Jenkins's research interests are being developed within the guidelines of the AP Chemistry curriculum. The laboratory capabilities at CHS are being upgraded in order to support the new experiments. Finally, in addition to the typical technical presentations and publications, these research results are being disseminated though the Pre-Game Showcase at UTK football games.Aziridine compounds are found in natural products, such as mitomycins and azinomycins, that have antitumor and antibiotic properties crucial to the development of new pharmaceutical products. Despite the myriad of uses, the synthesis of aziridine compounds has been wasteful and expensive due to the need for additional reagents that are not fully used in the final products. This CAREER project utilizes less expensive metal-based catalytic processes to avoid the need for expensive reagents. The improved reactions are expected to have impact in biology and synthetic organic chemistry, particularly in the preparation of new medicines. In his work with teachers and administrators at Central High School in Knoxville, Tennessee, Professor Jenkins stresses the use of sustainable processes in the development of new laboratories for the Advanced Placement (AP) Chemistry courses. Professor Jenkins publishes his work in technical journals but also disseminates his group's results in non-traditional forums, such as the Pre-Game Showcase at the University of Tennessee Knoxville football games.