Palladium-Catalyzed Aerobic Allylic Oxidations: Mechanisms and Applications

点击翻译按钮获取中文摘要

With this award, the Chemical Catalysis Program of the NSF Division of Chemistry is supporting the research of Professor Shannon Stahl to design agents that speed chemical reactions (catalysts) to perform specific chemical transformations (oxidize organic molecules with oxygen). Oxidation processes are important chemical reactions for the production of commodity chemicals, pharmaceuticals, and agrochemicals. Unfortunately, chemical oxidations usually use reagents (oxidants) that are toxic, are more powerful than needed and result in a large number of unwanted by-products, and/or generate waste that is harmful to the environment. Professor Stahl and his group at the University of Wisconsin–Madison are developing catalysts that oxidize chemical feedstocks called alkenes with oxygen; this oxidant generates only water as a by-product. These studies address the efficiency of the catalysts, trying to make them longer-lasting and more selective. This research program trains graduate and undergraduate students to become part of the chemical workforce and to recruit underrepresented minorities to STEM disciplines. In addition, important safety protocols are being designed to work with oxygen and organic molecules on large scale and thus, this research has important industrial relevance.The selective oxidation of C–H bonds is a key challenge in chemical synthesis and in the chemical industry, as it enables more efficient synthesis of novel and known chemical structures. Professor Stahl and his group are developing and characterizing palladium catalysts that mediate selective oxidation of allylic C–H bonds using molecular oxygen as the terminal oxidant. The resulting allylic carboxylate products are versatile intermediates in numerous synthetically-useful, secondary functionalization reactions. Research efforts explore strategies to enhance the stability of the Pd catalysts as a means of achieving high turnover numbers. Approaches towards this goal include the design of new ligands and the identification of reaction conditions that enable the catalysts to have intrinsic thermodynamic stability. Mechanistic studies play an important role in this effort, aided by innovative mechanistic tools such as a high-pressure NMR reactor capable of continuous on-line delivery of O2 and gas-uptake kinetic analysis. These fundamental studies focused on the achievement of practical goals, and the concomitant development of important safety protocols, provides a strong training environment for a diverse group of graduate and undergraduate students.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.