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Corkovic Andrej Thesis - Final10.85 MB
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Dissertation
Activation, reduction, and halogen exchange: unconventional uses of boron trihalides
University of Iowa
Doctor of Philosophy (PhD), University of Iowa
Autumn 2025
Abstract
Boron trihalides (BX3, where X = Cl, Br, I) have long been studied for their exceptional reactivity. As adept Lewis acids, BX3 can function as strong electrophiles that can coordinate with many molecules. This reactivity is credited to boron’s empty p orbital, resulting in BX3 being potent electron acceptors. With this capability, BX3 reagents have most often been used for cleaving ethers and activating carbonyls for addition. In ether cleavage, the weaker boron-halogen bond (from the BX3) is broken while a stronger boron-oxygen bond is formed. Furthermore, the main byproducts following basic hydrolysis are halide salts and boric acid, both of which have low toxicity. Chapter 1 presents a brief overview on boron chemistry before discussing C–F halogen exchange (halex) reactions that utilize boron Lewis acids. The chapter concludes by describing mono-selective C–F activation of polyfluorinated compounds. A brief description of design of experiments (DOE) is included. The chapter concludes with our lab’s recent work on halex of aryl trifluoromethyl compounds using BX3 and an iron catalyst.
Chapters 2 and 3 focus on an underexplored BX3 agent, boron triiodide (BI3). In general, BI3 is more expensive, more reactive, and more difficult to work with compared to its lighter trihalide analogues, resulting in fewer studies describing its use. Chapter 2 describes a method to generate BI3 in situ from potassium borohydride (KBH4) and molecular iodine (I2). The in situ generated BI3 was used to reduce nitroarenes to their aniline counterparts. Chapter 3 investigates the reactivity of BI3 for reducing acenes to their dihydro equivalents. While chapter 2 presents early mechanistic tests of BI3-mediated reduction, chapter 3 more thoroughly investigates the mechanism behind the reduction of acenes and includes deuteration quenches, radical traps, and kinetic monitoring.
Chapter 4 describes efforts to apply the lab’s previous iron-catalyzed boron trihalide halex of α,α,α-trifluoroarenes on more complicated substrates and perfluorinated compounds. Use of perfluoroalkyl substances (PFAS) has dramatically increased, but there are not many practical methods available to degrade PFAS. Halex reactions of (pentafluoroethyl)benzene are performed using BCl3, BBr3, and BI3 with varying catalysts. The halex reactions are also tested on several perfluorinated compounds received from Professor Spencer Pitre’s laboratory. These compounds contain perfluorinated chains of three carbons or more in addition to aryl ethers.
Chapter 5 diverts from the themes of the previous four chapters as it concentrates on nitrenes. Nitrenes are composed of neutral and monovalent nitrogen atoms. Further, nitrenes are short-lived and very reactive, exhibiting both lone pair and diradical behavior. They are often controlled with the use of metals like ruthenium and silver. Instead of using metals, boron can also help to mediate nitrene reactions. Chapter 5 provides a brief overview on the synthetic utility of metal-mediated nitrenes. The chapter then examines borylnitrenes and highlights an example by the Bettinger group that uses borylnitrenes to insert into the C–H bond of hydrocarbon solvents. This method is then applied by our lab to valorize the chemical feedstock of amino alcohols.
Chapter 6 concludes the thesis by summarizing the unconventional uses of boron trihalides. In this chapter, ideas for the future of each project are suggested. Further investigation into BI3-mediated reduction, including application to different functional groups and additional mechanistic investigations, are planned. Additional perfluoro compounds will be tested using our lab’s optimal halex reaction conditions. Finally, other methods of generating borylnitrenes will be investigated.
Details
- Title: Subtitle
- Activation, reduction, and halogen exchange: unconventional uses of boron trihalides
- Creators
- Andrej Ćorković
- Contributors
- Florence J. Williams (Advisor)David B.C. Martin (Committee Member)Gregory K. Friestad (Committee Member)Scott R. Daly (Committee Member)James J. Shepherd (Committee Member)
- Resource Type
- Dissertation
- Degree Awarded
- Doctor of Philosophy (PhD), University of Iowa
- Degree in
- Chemistry
- Date degree season
- Autumn 2025
- Publisher
- University of Iowa
- Number of pages
- xxxvii, 276 pages
- Copyright
- Copyright 2025 Andrej Ćorković
- Language
- English
- Date submitted
- 08/06/2025
- Description illustrations
- illustrations (some color)
- Description bibliographic
- Includes bibliographical references (page 166-184).
- Public Abstract (ETD)
Boron reagents are typically used to break strong bonds. This thesis investigates the unique reactivity of boron trihalides. Boron trihalides consist of a boron atom bound to 3 other atoms (e.g. chlorine, bromine, and iodine). Chapter 1 introduces the concept of breaking strong bonds by exploring different boron reagents that have been used to break C F bonds. Chapters 2 and 3 focus on a less studied boron reagent, boron triiodide (BI3) and detail newly discovered reactivity. Chapter 2 begins by introducing a method to generate BI3 from common lab reagents and then illustrates the transformation of nitro groups ( NO2) to amino groups ( NH2) with BI3. Chapter 3 applies BI3 s new transformation to compounds which have high importance in optoelectronic materials such as OLEDs found in televisions, smart phones, and tablets. Chapter 3 further explores how BI3 accomplishes these new transformations.
In chapter 4, the boron trihalides are used to break strong C F bonds in perfluoroalkyl substances (PFAS). There has been growing public concern over PFAS because of their negative health impacts and their persistence in the environment. There has also been growing public concern over PFAS because of their health impacts. Chapter 4 applies the principles from chapter 1 to PFAS.
Nitrenes are highly reactive and short-lived nitrogen species. To control the behavior of a nitrene, metals are often used; boron can also be used and is again the subject of chapter 5.
- Academic Unit
- Chemistry
- Record Identifier
- 9985135049002771
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