Date of Award

10-30-2024

Author's School

Graduate School of Arts and Sciences

Author's Department

Chemistry

Degree Name

Doctor of Philosophy (PhD)

Degree Type

Dissertation

Abstract

Organic electrochemistry has proven to be an efficient and green method for synthesis. Although the reactions studied to date have been very successful, there is still much to explore including opportunities to introduce new modes for controlling the selectivity of the reactions. Normally, the selectivity of an electrolysis reaction is based on the redox potential of the substrates. The working potential of an electrode either automatically adjusts to the potential required or is manually set at that potential. This allows for the systematic oxidation or reduction of a series of substrates that have a broad range of oxidation or reduction potentials. Typically, these electrolysis reactions do not select based on the types of molecular recognition events that occur when reactions are conducted with a chemical oxidant or reductant. There are two potential methods to solve this issue. One is to mediate the electrolysis with a chemical oxidant or reductant. The method is frequently very effective. It is one of the major driving forces behind the modern resurgence in electrosynthetic methods. However, for individual reaction on a family of substrates with a wide variety of oxidation or reduction potentials, the use of a mediated process requires incorporating a molecular recognition element into a family of catalysts. Each mediator must be able to perform the reaction selectively on one of the substrates. A different reaction with the similar overall substrate structure requires screening a second family of oxidants or reductants. Because of the complexity of this approach, a better method might be to transfer the recognition scaffold from the chemical reagent to the electrode surface and then to use that surface to control the selectivity of the reaction. The goal of this thesis is to demonstrate the significance of the advancements made towards these areas. First, we prove that the surface-control strategy can be applied to obtain the chemoselectivity of a normal preparative scale electrochemical reaction. This was accomplished by using electrochemical TEMPO oxidations between benzyl alcohols as competition studies. Then, we find this chemoselectivity also exist when the recognition group is remote from reaction center, which utilizes competition studies among cyclohexanols with remote aromatic groups. Based on the results, we tried to test if we could get regioselectivity of alcohol oxidations in the same molecule by the influence of a modified electrode surface. Additionally, functionalized polymers were designed and synthesized to influence the TEMPO oxidation by interacting with certain functional groups in alcohol substrates, a move away from the charge driven selectivity used in the initial experiments. Finally, in order to have a suitable model reaction as platform to study how to induce stereoselectivity, we developed a new method that uses electrochemical cyclization to form densely functionalized synthetic building blocks. This work led to the development of a mediated strategy for conducting the cyclization reactions on a polymer coated electrode surface, and effort that has now culminated in the exciting discovery that electrochemical cyclizations can be conducted directly on polymer coated electrodes if the polymer is itself conducting.

Language

English (en)

Chair and Committee

Jonathan Barnes

Committee Members

Chengfeng Ke; Kevin Moeller; Vladimir Birman; Zhen (Jason) He

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