Research

Research in the Yoon group focuses on the development of new reaction methods for organic synthesis. We are particularly interested in the use of catalysis as a strategy for increasing process efficiency, controlling reaction selectivity, and reducing the environmental impact of chemical synthesis. Representative project areas include the following.

Visible Light Photocatalysis. Photochemical reactions are intriguing from a synthetic perspective because the stereochemistry, regiochemistry, and chemoselectivity of organic reactions can differ dramatically under conditions of either thermal or photochemical activation. Yet organic chemists have long been reluctant to use photochemical reactions in complex molecule synthesis, and the properties of the structures that are uniquely accesible using photochemical activation have thus been relatively unexplored. A central goal of our research is to develop photochemical methods that can conveniently be conducted by any synthetic organic chemist, using sources of visible light that are already present in a standard chemistry lab. We focus upon the photoactivity of the transition metal chromophores that have been extensively exploited in the design of technologies for solar energy conversion. We have shown that complexes such as Ru(bpy)32+ and its derivatives can also be used to photochemically activate organic molecules towards a wide range of synthetically useful transformations.

Enantioselective Photochemistry. Photochemists have been interested in controling the stereochemistry of photochemical reactions for well over a century, but this has proven to be a remarkably challenging problem, with few general solutions. Several years ago, our laboratory introduced a concetually novel strategy that combines the robust photochemistry of transition metal photocatalysts with the well-understood stereocontrolling ability of chiral Lewis acid catalysts. This dual-catalysis strategy is highly flexible, and we have shown that it is applicable to a range of mechanistically distinct photocatalytic transformations.

Synthesis of Target Molecules. As synthetic chemists, we are inspired by the beauty of structurally complex natural products and by the need to produce complex pharmaceutical compounds using ever cleaner and more efficient synthetic processes.  Target-oriented synthesis, therefore, is an important goal of our research, both as a benchmark by which to test the methods developed in our laboratory and as an inspiration that guides our research program.

Studying the Mechanisms of Photocatalytic Reactions.  In addition to our focus on synthetic methodology development, we aim to provide insights into the common features of photocatalytic mechanisms that we hope will guide the development of new photochemical transformations. Photocatalytic reactions differ from other kinds of reactions in several important ways, and the methods applicable to studying their mechanisms can also differ.   Thus, we take a transdisciplinary approach to the study of mechanism that borrows techniques kinetic, computational, and spectroscopic techniques from a wide range of disciplines to achieve our goals.

Inorganic and Organometallic Photochemistry. The advancement of transition metal photocatalysis as a new field within synthetic organic chemistry has required us to synthesize and characterize many novel Ir and Ru complexes. We are developing practical, scalable, and flexible techniques for the synthesis of these complexes, and we are uncovering new and unexpected characteristics of known complexes that emerge only in the non-polar media that are ideal for organic synthesis.

Chemistry of Heteroatom-Centered Radicals.  We are fascinated by the chemistry of open-shelled reactive intermediates, both those produced by photochemical techniques and by non-photochemical catalytic strategies.  An ongoing interest in our research group is the design of novel oxidation reactions that involve the intermediacy of heteroatom-centered radicals.