Chirality-Driven Self-Assembly of Dual Catalytic Dendrimers: Application Toward One-Pot Tandem Reactions

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In living cells many simultaneous chemical transformations occur with no interference between the enzymes that catalyze them. To accomplish this Nature has evolved to incorporate catalyst sites within enzyme pockets or by physical separation using membranes. The successful construction of artificial analogues of such frameworks would reduce catalyst deactivation and eliminate undesirable side reactions. These are important goals in catalysis with many potential practical applications. With funding from the Chemical Catalysis Program of the Chemistry Division, Dr. Moteki of the University of Missouri Kansas City is developing synthetic materials possessing multiple types of incompatible catalyst sites where the sites are spatially isolated. Together with Dr. Palencia of the University of Nebraska Kearney, the catalytic efficiency and reaction scope of these catalysts are being tested. Drs. Moteki and Palencia are actively recruiting students from local high schools and community colleges, targeting underrepresented minority students, and providing them with early research experience. The research experience will increasing retention, and enhancement of underserved populations in STEM field. Summer workshops for community and small college faculty are also being conducted. Such efforts are crucial in forming new generations of young research scientists.Tandem-catalyzed reactions have been widely recognized as one of the most efficient atom economical and environmentally friendly processes, due to minimization of waste generation. In particular, orthogonal tandem catalysis, which features two or more distinct catalysts with differing mechanisms, offers potential for higher process efficiency. Over the past few decades only a handful of successful examples have been reported primarily due to the difficulty in creating compartmented macro-structures that spatially separate incompatible catalysts. This proposal aims at building a multi-component catalytic dendrimer complex via chiral self-discrimination, which enables the in situ quantitative assembly of various multi-domain dendrimers through metal-chiral ligand interactions. This allows tuning of the microenvironment far easier than conventional covalently assembled systems, making it a more attractive system for reaction screening targeting various multi-step tandem chemical transformations. Our research team aims to understand the underlying catalyst structure-function relationship of the dual catalytic dendrimer by varying polarity as well as architectural design of each catalytic domains. In addition, the efficiency and versatility of dual catalytic dendrimers will be investigated, by using three different types of tandem reactions as models; i) substrate-selective tandem catalysis, ii) tandem reaction involving a catalytically reversible step, and iii) tandem reaction involving competitive catalytic pathways. The operational simplicity in reaction screening and the dendron preparation synthetic steps is ideal for training the next generation of synthetic chemists. Dr. Moteki and Dr. Palencia are actively engaged in outreach activity, they will host an annual workshop as means of recruiting of underserved minority students from local high schools and community colleges for summer research internship in their research groups.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.