Graduation Semester and Year
Spring 2026
Language
English
Document Type
Dissertation
Degree Name
Doctor of Philosophy in Chemistry
Department
Chemistry and Biochemistry
First Advisor
Junha Jeon
Second Advisor
Frank Foss
Third Advisor
Joseph Buonomo
Fourth Advisor
Kwangho Nam
Abstract
The research described in this dissertation is on three different projects namely i) aryne formation through single electron transfer–coupled hydrogen atom transfer: C–N cross- coupling, ii) enantioselective lewis based-catalyzed, branch-selective hydrogen atom transfer hydrosilylation iii) C–N cross-coupling of aryl fluoride via single electron transfer in the absence of transition metal catalyst.
The first chapter is focused on synthesis and mechanism investigation of new type of aryne formation through single electron transfer–coupled hydrogen atom transfer. Aryne, characterized by its high reactivity arising from a strained triple bond in aromatic systems, stands as one of the most versatile reactive intermediates in synthetic chemistry. Here, we introduce a main-group metal approach in which arynes are generated from readily available monohaloarenes through single-electron transfer (SET)–coupled hydrogen atom transfer (HAT), mediated by earth-abundant alkali metal hypercoordinate hydridoaminosilicon species ligated by a second equivalent of Lewis base. Mechanistic studies establish the dual role of hypercoordinate silicon as both a stepwise single-electron donor to aryl halides and a hydrogen atom acceptor from aryl radicals, offering rare insights into its reactivity. Building on these iiimechanistic insights, the synthetic impact of this work extends to the development of a transition metal free C–N cross-coupling platform that yields high-value synthetic building blocks, biomedically relevant targets, and functional materials. The second chapter is focus on design and synthesis chiral potassium binding lewis base catalyst. Transition metal–catalyzed enantioselective and branch-selective hydrosilylation of vinylarenes has been well established. In our previous work, we developed Lewis based- catalyzed, complexation-induced HAT (LBCI-HAT) using hydrosilane and KOtBu as Lewis base catalyst to give highly regioselective, Markovnikov products. In chapter, we envisioned developing as enantioselective branch-selective hydrosilylation of alkenes using a chiral Lewis base potassium-binding catalyst. The catalyst was designed to integrate a Lewis base, a potassium-binding site, and a chiral element to control enantioselectivity. However, the potassium-binding unit, 1-aza-18-crown-6 ether, did not exhibit sufficient nucleophilicity due to steric hindrance during synthesis. We eventually succeeded in connecting 1-aza-18-crown- 6 ether with (R)-BINOL through amide bond formation. However, the resulting chiral catalyst showed low selectivity, likely due to reduction of the amide and release the 1-aza-18-crown-6 ether during the reaction process. Attempts to reduce the amide or apply alternative coupling strategies also failed to establish a stable linkage between 1-aza-18-crown-6 ether and (R)- BINOL. Therefore, a new type of catalyst has been proposed and is ready to be synthesized and evaluated.
The third chapter is focus on C–N cross-coupling of aryl fluoride with transition metal free conditions. Halides are typically regarded as effective leaving groups in cross-coupling reactions due to their bond dissociation energies, whereas fluorine is difficult to activate. In our previous studies, aryl bromides and aryl chlorides undergo aryne formation through a single- electron transfer (SET)–coupled hydrogen atom transfer (HAT) process mediated by earth abundant alkali metal hypercoordinate hydridoaminosilicon species ligated by a second equivalent of Lewis base. An extended study involving aryl fluorides has also been considered. Preliminary scope studies suggest that a different reaction pathway should be considered. Reoptimization and reaction-order studies indicate mechanistic differences between aryl bromides/chlorides and aryl fluorides. Future work will focus on more detailed mechanistic investigations and expansion to a broader substrate scope.
Keywords
Cross coupling, Hydrosilylation, Aryne, Lewis Base catalyzed reaction
Disciplines
Organic Chemistry
License
This work is licensed under a Creative Commons Attribution-NonCommercial-Share Alike 4.0 International License.
Recommended Citation
Chang, Yao Chung, "STUDIES ON CATALYTIC C–SI AND C–N-FORMING REACTIONS USING ORGANOSILANES" (2026). Chemistry & Biochemistry Dissertations. 7.
https://mavmatrix.uta.edu/chemistry_dissertations2/7
Comments
I would like to express my profound gratitude to my research advisor, Dr. Junha Jeon, for his unwavering guidance, patience, and support throughout the past several years, all of which were indispensable to the successful completion of this work. From the moment I joined his research group six years ago as a master’s student at the University of Texas at Arlington, he provided me with a welcoming and intellectually stimulating environment that allowed me to grow both scientifically and personally. Dr. Jeon is an exceptional mentor whose dedication to teaching, research, and student development has left a lasting impression on me. Under his supervision, I gained extensive hands-on experience in synthetic organic chemistry, including reaction design, mechanistic analysis, and advanced purification techniques, far beyond what could be obtained through coursework or textbooks alone. His thoughtful guidance during both successful and challenging periods of my research was invaluable, and I am especially inspired by his disciplined approach to experimental planning, data interpretation, and scientific writing. I am deeply thankful for his encouragement, trust, and mentorship, and I am truly honored to have worked under his supervision.
I would also like to sincerely thank my committee members, Dr. Frank Foss, Dr. Joseph Buonomo, and Dr. Kwangho Nam, for their time, expertise, and insightful feedback, all of which significantly strengthened this work. Their thoughtful comments and constructive criticism greatly improved both the scientific quality and clarity of this dissertation. I am also grateful to former committee member Dr. Carl Lovely for his early guidance and valuable contributions to my academic development. In addition, I would like to thank the graduate students in the organic chemistry division for their helpful discussions, technical assistance, and collegial support throughout my studies.
I am deeply appreciative of my research group members—Dr. Saerona Kim, Dr. Buddhadeb Pal, Dr. Suman Das Adhikary, Neetesh Yadav, Linda Lillawmsangi, John Jackson, and Isurika Wattegedara, as well as our undergraduate researchers—whose dedication, teamwork, and friendship made the laboratory a productive, collaborative, and inspiring environment. Their willingness to share knowledge, troubleshoot experiments, and support one another played an essential role in both my research progress and my overall experience in the program.
I would also like to extend my sincere thanks to Dr. Brian Edwards and Dr. Roy McDougald or their expert training and guidance on a wide range of analytical and spectroscopic instruments. Their assistance greatly enhanced my ability to conduct high-quality and reliable research. I am equally grateful to Stephanie Henry, Debbie Cooke, and Shelby Adams for their exceptional administrative and personal support. Their kindness, encouragement, and willingness to help with matters beyond chemistry made a significant difference during my time in the program.
Finally, I would like to acknowledge all those who contributed, directly or indirectly, to my academic and personal development throughout this journey. The support, mentorship, and collaboration I received have been invaluable, and this work would not have been possible without the collective efforts of these individuals.