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Investigation of Strain-Activated Trapping Reactions of 1,2-Cyclohexadiene: Intramolecular Capture by Pendent Furans and Styrenes
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- Author / Creator
- McIntosh, Kyle
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1,2-Cyclohexadiene is a small carbocyclic allene that as a reactive intermediate can be utilized in a variety of reaction pathways. The chemical literature around this species is largely limited to various methods of generation and simple trapping reactions. Little research exists on methods to control these intermediates and enable their more prominent use in synthesis. One popular method to control a reaction is to move from an intermolecular to intramolecular framework, where more of the factors affecting a reaction can be controlled. In this thesis the development of new intramolecular trapping reactions of 1,2-cyclohexadiene will be discussed with a focus on [4+2] and [2+2] modes of cycloaddition with furans and styrenes respectively.Chapter 1 will provide a detailed overview of the origins of 1,2-cyclohexadiene including its synthesis, structural investigations, trapping reactions and mechanistic studies; modern synthetic efforts with the intermediate and similar compounds will also be described. This review of the relevant literature will serve as a primer to discuss the new results described in this thesis.Chapter 2 shows the development of a state-of-the-art intramolecular trapping reaction of 1,2-cyclohexadiene using pendent substituted furans. This [4+2]-cycloaddition reaction was enabled via a modular synthetic sequence that allowed the production of a variety of starting materials and allowed the initial scope of this new methodology to be explored. This mild cycloaddition proceeded in high regio- and diastereoselectivity and allowed access to versatile hetero-tetracycles. Efforts to manipulate these complex hetero-carbocycles were examined and a surprising retro [4+2]-cycloaddition was discovered.Chapter 3 continues the development of intramolecular trapping reactions of 1,2-cyclohexadiene with new substrates that contain a styrene moiety and undergo [2+2]-cycloaddition. The chemical nature of the double bond on the styrene was shown to be vital to reaction efficacy and interesting trends were demonstrated through carefully selected substrates. Efforts to synthesize an intermediate in the total synthesis of isocomene are also described.Chapter 4 will tie the [4+2] and [2+2]-cycloaddition reactions together and discuss exciting future directions for this chemistry. The chemical utility of 1,2-cyclohexadiene, as reported in this thesis, will be discussed and a broad overview of what the future may hold for this reactive intermediate will be evaluated.
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- Subjects / Keywords
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- Graduation date
- Fall 2020
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- Type of Item
- Thesis
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- Degree
- Doctor of Philosophy
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- License
- Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.