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Full text release has been delayed at the author's request until December 15, 2029

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The Development of Synthetic Electroreductive Methodologies for the Sustainable Functionalization of Small-Molecule and Macromolecular Electrophiles

Zackasee, Jordan Lawrence Stephen
http://rave.ohiolink.edu/etdc/view?acc_num=osu1723733636447374

Abstract Details

2024, Doctor of Philosophy, Ohio State University, Chemistry.
Net reductive cross-coupling reactions have gained increasing interest over the last two decades due to their ability to directly couple two electrophiles, avoiding the need to synthesize nucleophilic intermediates in turn streamlining carbon-carbon (C-C) bond formation. These cross-electrophile couplings (XEC) reactions have proven to be instrumental in the development of late-stage drug modification pathways due to their ability to easily generate Csp2-Csp3 bonds. While many of these transformations rely on the use of powdered metal reductants as a source of electrons, the heterogenous mixtures can be problematic for industrial processes due to difficulties with agitation and safety concerns over copious amounts of pyrophoric metal powders. An alternative approach that circumvents the use of metal powders is electrochemical XEC (eXEC) cross-coupling. By leveraging electrical current as a source of electrons, eXEC offers a high precision over the delivery of electrons to a system and is inherently easy to scale-up. While electroreductive cross-electrophile coupling (eXEC) represents an attractive strategy for the direct C–C coupling of two electrophiles, these reactions generally suffer from limited scope compared to reactions with chemical and metal reductants. Chapter 2 demonstrates that mediator-assisted electrocatalysis is a general strategy for the enhancement of eXEC reactions. While eXEC reactions catalyzed by a variety of widely available ligand−nickel complexes are low yielding when applied to reductive couplings of challenging substrates, reactions with the same complexes generate products in near-quantitative yield when a redox-matched mediator is included. We identify a library of catalyst−mediator systems that provide complementary reactivity and enable coupling of a range of substrate classes in high yields. These catalyst systems are applicable to both chemical and electrochemical reduction, but some require electroreduction due to the low potentials required for activation. Finally, mechanistic studies offer insights that facilitate catalyst−mediator pairing. While the success of this work is indeed a valuable improvement in the field of eXEC, alkyl chlorides remain a challenging class of electrophile to activate. The ability to functionalize carbon-chloride (C-Cl) bonds would allow a larger selection of electrophiles to be functionalized, in addition the opportunity for polychlorinated waste remediation. In particular, polyvinyl chloride (PVC) polymers are of great interest due to their larger volume of C-Cl bonds present in the polymer chains. PVC plastics require high loadings of plasticizers and stabilizers to achieve commercially useful bulk properties. However, these non-covalent additives leach from PVC over time, resulting in the loss of their tailored functionality. Chapter 3 details the electrocatalytic functionalization of PVC to covalently graft plasticizing additives directly onto the polymer backbone. Here, mechanistic insights guided the design of electrocatalysts capable of modifying C-Cl bonds of PVC under mild conditions with high selectivity while suppressing side reactions such as elimination and chain scission. Functional groups that mimic PVC plasticizers are covalently installed into the backbone of PVC to create new mate-rials with distinct bulk properties from the original polymer. The degree of polymer grafting is easily controlled by simply changing the redox capacity that is passed during electrolysis. This strategy is employed to create chemically- and leach-resistant PVC materials by directly electrolyzing mixtures of consumer PVC products. Additionally, Chapter 4 details ongoing work to expand the scope of electroreductive PVC modification has shown that borylation of the polymer is possible. Through application of surfactants, activation of C-Cl bonds in the polymer chain becomes possible, enabling direct and controllable borylation of the plastic under mild, catalyst-free conditions. With this, electroreductive methodologies have proven to be invaluable in design and execution of sustainable cross-coupling methodologies.
Christo Sevov, Dr. (Advisor)
David Nagib, Dr. (Committee Member)
Christopher Hadad, Dr. (Committee Member)
279 p.
Chemistry; Experiments; Organic Chemistry
Electrocatalysis; Polymers; Polyvinyl Chloride; Radical Chemistry; Organometallic Mechanisms; Chloroalkanes; Cross-Electrophile Coupling, Electrophiles; Ni Catalysis; Co Catalysis

Recommended Citations

Citations

  • Zackasee, J. L. S. (2024). The Development of Synthetic Electroreductive Methodologies for the Sustainable Functionalization of Small-Molecule and Macromolecular Electrophiles [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1723733636447374

    APA Style (7th edition)

  • Zackasee, Jordan. The Development of Synthetic Electroreductive Methodologies for the Sustainable Functionalization of Small-Molecule and Macromolecular Electrophiles. 2024. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1723733636447374.

    MLA Style (8th edition)

  • Zackasee, Jordan. "The Development of Synthetic Electroreductive Methodologies for the Sustainable Functionalization of Small-Molecule and Macromolecular Electrophiles." Doctoral dissertation, Ohio State University, 2024. http://rave.ohiolink.edu/etdc/view?acc_num=osu1723733636447374

    Chicago Manual of Style (17th edition)

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© 2024, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.
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