Thesis advisor: Shih-Yuan Liu / Described herein are three projects that derive from in-depth studies of the distinct electronic structure of monocyclic 1,2-dihydro-1,2-azaborine (heretofore referred to as simply 1,2-azaborine). In the first chapter, the first comprehensive review of the late-stage functionalization methods available for 1,2-azaborines as well as their bicyclic and polycyclic (BN-PAH) counterparts is presented. In the second chapter, the development of a general method for both C4 and C5 functionalization based on the building block approach is described. The distinct electronic structure of 1,2-azaborine enables the chemical separation and further functionalization of C4 and C5 borylated isomers. In the second part, the C4, C5, and C6 isomers of BN-styrene analogues were prepared using the newly developed azaborine building blocks. The corresponding polymers were synthesized and extensively characterized in order to compare the effects of the BN-bond positioning relative to the polymer chain. In the fourth and final chapter, 1,2-azaborine-containing phosphine ligands featuring a P-B bond are synthesized. A comparative electronic structure analysis is performed between the BN-phosphine ligands and their direct all-carbon counterparts. / Thesis (PhD) — Boston College, 2019. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

Homogenous Au(I)-catalysis has become a valuable synthetic tool to activate a host of unsaturated carbon functional groups towards nucleophilic addition. Over the course of the past two decades, many have embarked on new journeys within this field. Notably, the advancements in this field hinge on the development of new ligand systems that impart novel reactivity at the metal. Our group has focused on this area, as we have successfully demonstrated the utility of 1,2,3-triazoles as ligands for gold and a host of other transition metals and Lewis acids. With respect to gold catalysis, these ligands enhance the stability of the metal center, thus inhibiting typical reductive decomposition pathways that have plagued this field. The enhanced stability comes with a price though as higher temperatures can be required. We’ve addressed this challenge by discovering an interesting synergy between triazole-gold and Lewis acids, allowing us to overcome the lower reactivity of these catalysts. During my time as a graduate student, I have focused heavily on enlisting these catalytic systems for new reaction discovery. In my first experimental chapter, I was able to develop an interesting reaction cascade in which triazole-gold and secondary amine catalysts were used. I started with a well-known gold-catalyzed Claisen rearrangement of propargyl vinyl ether, yielding functionalized allenes. The identical oxidation state between these allenes and synthetically appealing dienals was an impetus to develop a new isomerization strategy. After screening various conditions, I was able to successfully execute this design. Most of the work I have been involved in over the past two years has surrounded a gold-catalyzed hydroboration to yield interesting hetercocycles containing a N-B bond. The N-B bond offers some unique properties as it is isoelectronic to a C-C double bond. Despite the simplicity in this design, it would become apparent early on in this research that mitigating the reducing strength of the starting materials was absolutely critical. Starting materials that were too strongly reducing led to rapid catalyst decomposition. Through thorough reaction screening, we have been able to identify a catalytic system that performs extremely well in this context. Ultimately, our goal in this work is to access 1,2-azaborines, which are isosteres of benzene. This compound exhibits aromaticity, as determined through structural and quantitative analyses by several groups. However, subtle differences in properties between the azaborine and benzene, such as its polarity, have intrigued many researchers across various disciplines. Moreover, the ubiquity of its carbonaceous parent in biological systems has prompted many to pursue new synthetic routes to access 1,2-azaborines.

xxv, 468 p. : ill. (some col.) A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. / 1,2-Dihydro-1,2-azaborine is a six-membered aromatic heterocycle that is related to the quintessential aromatic molecule, benzene, via the replacement of a CC fragment in benzene with an isoelectronic BN bond-pair. Like the benzene motif, 1,2-dihydro-1,2-azaborine derivatives could provide opportunities in fields ranging from medicine to materials. Recent breakthroughs in the synthesis of 1,2-dihydro-1,2-azaborine have led to a burgeoning interest in this relatively unexplored heterocycle. This dissertation describes the synthesis, characterization, and potential applications of novel 1,2-dihydro1,2-azaborines. Chapter I reviews the chemistry of monocyclic and polycyclic BN-heterocycles over the last fifty years. Chapter II introduces the synthesis of numerous boron-substituted 1,2-dihydro-1,2-azaborine derivatives from a versatile precursor. Chapter III discusses the first successful synthesis of the parent 1,2-dihydro-1,2-azaborine, which is isoelectronic with benzene itself. An examination of the chemistry of 1,2-dihydro-1,2-azaborine provides a direct comparison of its properties relative to benzene. Chapter IV discusses the synthesis and characterization of 1,2-dihydro-1,2-azaborines incorporated into phenylacetylenic scaffolds. Chapter V discusses unrelated work on nitrated lipids, which was performed under the guidance of Professor Bruce Branchaud. The chapter introduces the importance of nitrated lipids in a biological context and details the synthetic achievements in this field. This dissertation includes previously published and unpublished co-authored material. / Committee in charge: Michael Haley, Chairperson, Chemistry; Shih-Yuan Liu, Advisor, Chemistry; David Tyler, Member, Chemistry; Raghuveer Parthasarathy, Outside Member, Physics