Elucidation of Radical Cation Trapping Chemistry: Using Electrochemical and Photochemical Techniques to Qualitatively Assess the Kinetics behind Anodic Oxidative Cyclizations
Date of Award
Doctor of Philosophy (PhD)
While the field of organic chemistry has grown throughout the decades, its primary concern has always been on the generation, conversion, and study of molecular structures. Within that philosophy, the development of new reactions affords chemists the ability to overcome previous synthetic barriers or develop more elegant and simple synthetic routes to difficult-to-construct molecules. Within that realm, electrochemistry is seeing increased attention due its ability to generate highly reactive intermediates, recycle chemical reagents, and reverse the polarity of known functional groups. One example of such an application is the use of electrochemistry to form radical cations. While radical cations have a relatively small history of use within organic chemistry, they are central to our understanding of the oxidation reactions that allow us to increase the functionality of a molecule, and how we can take maximum advantage of them. Accordingly, this dissertation examines the mechanistic pathways through which radical cation initiated reactions proceed. Chapter 2 begins with competition studies that were initially used to probe the mechanism of radical cation trapping between two nucleophiles. By tethering two nucleophilic trappings groups to an electron rich olefin, we were able to deduce the relative reactivity of various trapping groups, which included sulfonamides, alcohols, enol ethers, and allyl silanes, toward a ketene dithioacetal derived radical cation (a commonly used synthetic intermediate in our group). The use of cyclic voltammetry aided our efforts in understanding the rate of the initial cyclization and in so doing the larger mechanistic paramaters at play. Chapter 3 explores the relationship between electrochemical and photochemical methods for the generation of radical cations. While both methods generate radical cation intermediates, they differ in the number of electrons removed from the substrate. Hence, the downstream chemistry is significantly different. We hoped to use the studies to show the generality of the conclusions reached using electrochemical competition studies. Instead, we found that the complimentary methods were both important for getting a complete picture of the reactions. This surprising result is shaping current efforts aimed toward the development of new, synthetically relevant oxidative cyclization reactions.
Chair and Committee
Kevin D. Moeller
Vladimir Birman, James Janetka, John-Stephen Taylor, Timothy Wencewicz,
Gonzalez, Luisalberto, "Elucidation of Radical Cation Trapping Chemistry: Using Electrochemical and Photochemical Techniques to Qualitatively Assess the Kinetics behind Anodic Oxidative Cyclizations" (2020). Arts & Sciences Electronic Theses and Dissertations. 2191.