Browsing by Subject "Benzyne"
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Item Development and testing of a protocol for computational prediction of 1H and 13C NMR chemical shifts and thermochemistry and reaction analysis of benzyne formation and trapping(2013-01) Marell, Daniel JoshuaElucidating structures of novel compounds and investigation of new reactions are two tasks that experimental organic chemists address on a frequent basis. The pursuit of these objectives can be rigorous and time-consuming. Of the methods employed in elucidating the structure of novel compounds, nuclear magnetic resonance (NMR) is by far the most widely applied. Investigation into new reactions may require any number of techniques to understand the reaction scope, kinetics, optimal conditions, mechanisms, etc. In both cases, the use of computational methods is well-suited to augment the experimentalist's data to guide and understand the system being investigated. A protocol for facilitating computational prediction of NMR chemical shifts was developed. Application to a set of natural products previously evaluated against computed NMR shifts, showed improved accuracy, through analysis of the corrected mean-absolute error (CMAE). The protocol was further employed successfully to aid in analysis of experimental spectra for compounds synthesized by collaborators where multiple diastereomers were possible. Graphing templates were also created to allow for rapid inspection of possible structures without more in-depth statistical analysis. Thermodynamic and mechanistic analysis on the formation and reaction of benzyne was also performed. Thermodynamic restrictions on the ring-size of fused benzynocycloalkanes were investigated. Additionally, analysis of the energetics and transition state geometries for small-molecule trapping (both intra and intermolecular) of benzyne are discussed.Item The Hexadehydro-Diels–Alder (HDDA) Enabled Synthesis of Elaborated Polycyclic Aromatic Compounds(2022-02) Lee, DanielPolycyclic, highly fused/conjugated aromatic organic compounds (PACs) have intrigued chemists since the discovery of naphthalene in 1821. Given the unabated interest in such molecules, the development of new methods and strategies for the practical synthesis of PACs having new structural motifs is important. The advantage of thermally generating benzynes via the cycloisomerization of a tethered tri-yne (the hexadehydro-Diels–Alder reaction) serves as an excellent platform for chemists to discover new modes of benzyne reactivities and new synthetic approaches. This thesis describes a new complementary strategy to synthesize polycyclic aromatic products from multi-ynes via the HDDA reaction. Two aspects of the application of the HDDA reaction are discussed: (1) reaction of coumarins with HDDA-benzyne, and (2) construction of structurally complex molecular architectures via radial HDDA reactions.Item Intermolecular Nucleophilic Additions to Thermally-generated Benzynes and Mechanistic Studies(2019-08) Zhang, Juntianortho-Benzynes compose a highly versatile class of reactive intermediate in organic chemistry. They can be trapped in situ by a variety of nucleophile-electrophile pairs or enter into pericyclic reactions to generate multi-substituted arene moieties that can be further functionalized to different target molecules. Compare to traditionally generated benzynes (through elimination of arene derivatives), the thermally generated benzynes [through the hexadehydro-Diels–Alder (HDDA) reaction] provide both a synthetic approach to functionalized arene derivatives and unusual modes of reactivity. In this Thesis, I will emphasize some of the more recent aspects of HDDA reactions as a tool for synthesizing multi-functionalized arene derivatives, along with divergent reaction pathways and mechanistic insight. Details of this Thesis include (i) the phenol-ene reaction to construct biaryl moieties (Chapter 2), (ii) reaction of HDDA-generated benzynes with N-heterocycles (Chapter 3), (iii) an atypical mode of “1,3-dipolar” cycloaddition reaction between benzynes and electron-deficient thioamides (Chapter 4), (iv) divergent reactivity by glycidol analogs: ring cleavage via pinacol-like rearrangements vs. oxirane fragmentations (Chapter 5), and (v) total synthesis of isohericerin using the HDDA reaction (Chapter 6).Item Water-Triggered Benzyne Generation Using Pseudocyclic Arylbenziodoxaboroles(2018-09) Fuchs, JonathanHypervalent iodine compounds are a broad and hot topic in synthetic organic chemistry. They are much cheaper, more environmentally friendly, and safer to handle then their transition metal counterparts. The largest class of hypervalent iodine belongs to that of the diaryliodonium salts. These compounds are well known arylating reagents and exhibit a wide array of reactivity. One such reaction they are known for is the generation of benzyne, owing to phenyliodine’s leaving ability. It is reported to be a million times better leaving group then triflate. There are several ways to trigger benzyne, the most common and effective are using fluoride anion to desilylate TMS which induces triflate anion to leave. These methods provide mild and convenient methods for producing benzyne. Herein, the first ever generation and subsequent trapping of benzyne using water as trigger from novel pseudocyclic arylbenziodoxaboroles is reported.