Special Organic Seminar: "Harnessing the Power of Non-Covalent Interaction for Organocatalysis"

Seminar series
Organic Colloquium
Mon, May 12 3:00pm
Cram Conference Room – 3440 Molecular Sciences Bldg
Speaker Professor Steven E. Wheeler
Texas A&M University
Department of Chemistry

Special Organic Seminar

"Harnessing the Power of Non-Covalent Interaction for Organocatalysis"

Abstract.  The field of organocatalysis continues to mature, and now provides efficient routes to many chiral synthetic building blocks without the need for transition-metal-based catalysts.  Often, the effectiveness of these catalysts hinges on a delicate balance between competing non-covalent interactions. I will describe our efforts to understand the activity and stereoselectivity of several organocatalytic transformations through the application of modern tools of computational quantum chemistry, with a particular focus on the role of favorable non-covalent interactions (anion/pi interactions and pi-stacking interactions, among others).  In the process, I will describe our progress unraveling the nature of these non-covalent interactions.  In particular, I will show that conventional models of substituent and heteroatom effects on many non-covalent interactions involving aromatic rings are not supported by recent computational and experimental data. I will offer a simple, alternative predictive model of these interactions.  For example, I will show that substituent effects in pi-stacking interactions can be described based on the local, direct interactions between the substituents and the other ring.  There is no need to invoke substituent-induced changes in the pi-electron-system of the substituted ring to describe these substituent effects. Similarly, favorable anion/pi interactions between simple anions and N-heterocycles (pyridine, pyrazine, s-triazine, etc) arise almost entirely from interactions of the anion with the sigma-system of the ring, not the pi-system.