Cascade Reactions for the Synthesis of Polycyclic Aromatic Hydrocarbons and Carbon Nanoribbons

• Other Authors: Byers, Philip M. (authoraut)
• Format: Others
• Language: English; English
• Published: Florida State University
• Subjects: Chemistry; Biochemistry
• Online Access: http://purl.flvc.org/fsu/fd/FSU_migr_etd-7737

Radical and electrophile-promoted nucleophilic closure cascade reactions have been used for the synthesis of polycyclic aromatic hydrocarbons (PAHs) and carbon nanoribbons. Chapter 1 provides a discussion on radical cascade reactions, with a brief history and examples of well documented radical cascade reactions. Investigations into radical chain processes as well as redox processes are discussed. There is much development in these cascades currently due to the complex products that can be formed in a minimal amount of synthetic steps. Chapter 2 discusses the radical cascade that we developed, using a radical chain process. Selective radical generation in conjugated oligomeric o-aryleneethynylenes initiates a cascade which involves five fast radical cyclizations followed by aromatization via a 1,5-H shift to yield PAHs. Computation and 2D NMR studies were performed to determine the final cascade products. Chapter 3 discusses the growing trend in which gold catalysts are used to initiate cascade reactions through an electrophile-promoted nucleophilic closure mechanism. A number of current examples are also provided which demonstrate how gold catalyzed cascade reactions can efficiently synthesize complex PAH molecules. Chapeter 4 demonstrates our approach for the synthesis of fused benzofuran structures through gold catalysis. Through a gold catalyzed electrophile-promoted nucleophilic closure, PAHs containing benzofuran units with a polycyclic aromatic backbone were synthesized through a Sonogashira/5-endo-dig/6-endo-dig cascade. Depending on which mechanism is used, all exo cyclizations can be achieved (radical), or all endo cyclizations (electrophile-promoted nucleophilic closure). Starting materials for either cascade mechanism can be synthesized in a modular fashion, allowing for the systematic and controlled preparation of functionalized PAHs and carbon nanoribbons where, potentially, each of the peripheral aromatic rings can be different. The materials synthesized have future applications in the nano-materials and -electronics industries. Chapter 5 discusses future work in the field of gold catalyzed cascade reactions and provides conclusions on the work presented here within. === A Dissertation submitted to the Department of Chemistry and Biochemistry in partial fulfillment of the requirements for the degree of Doctor of Philosophy. === Summer Semester, 2013. === June 17, 2013. === Carbon, Cascades, Gold, Nanoribbons, PAH, Radicals === Includes bibliographical references. === Igor V. Alabugin, Professor Directing Dissertation; Rufina Alamo, University Representative; Geoffrey Strouse, Committee Member; Sourav Saha, Committee Member.