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Preparation and Synthetic Applications of Chiral Alkyl Boronates and Unsaturated Alkenyl Boronates Open Access
- Other title
Chiral alkyl boronates
Enantioselective conjugate addition
- Type of item
- Degree grantor
University of Alberta
- Author or creator
Lee, Jack C. H.
- Supervisor and department
Hall, Dennis G. (Department of Chemistry, University of Alberta)
- Examining committee member and department
West, Frederick G. (Department of Chemistry, University of Alberta)
Bergens, Steven H. (Department of Chemistry, University of Alberta)
Stryker, Jeffrey M. (Department of Chemistry, University of Alberta)
Organ, Michael G. (Department of Chemistry, York University)
Harynuk, James (Department of Chemistry, University of Alberta)
Department of Chemistry
- Date accepted
- Graduation date
Doctor of Philosophy
- Degree level
As Organic Chemistry evolves into the 21st Century, the goal of this discipline has altered dramatically from merely accessing target molecules to efficiently synthesizing these compounds with minimization of non-strategic functional group manipulations and interconversions. Organoboron reagents represent one of the potential solutions towards reaching this goal. These versatile compounds can either be used to construct the desired carbon−carbon bond through various cross-coupling reactions, or be converted directly to the desired functionality through different chemical reactions. Direct transformations make interconversions between different functional groups unnecessary, thus making the overall process step-economical. In this thesis, several synthetic methods were developed to synthesize chiral alkyl boronates or alkenyl boronates through metal-catalyzed chemical transformations. These methodologies are based on early introduction strategy which applies well-established synthetic protocols to substrates with a pre-installed boronyl moiety. The subsequent applications of these compounds were also investigated, leading to a variety of synthetically valuable adducts.
In order to access novel chiral secondary alkyl boronates, catalytic asymmetric conjugate addition reactions of 3-boronyl -unsaturated esters with Grignard reagents were developed. Chapter 2 describes the details of optimization of this methodology and the applications of the chiral alkyl boronate products.
Aiming to explore the intrinsic reactivity of enantioenriched 1,1-diboron compounds, their synthesis was accomplished for the first time by performing asymmetric conjugate borylation on 3-boronyl enoates. The resulting optically enriched 1,1-diboron compounds were found to be excellent cross-coupling partners in Suzuki-Miyaura cross-couplings, leading to chiral alkyl boronates with excellent enantioselectivity. The details of these studies are presented in Chapter 3.
In order to conduct a thorough examination of substrate scope in asymmetric conjugate reductions of 3-boronyl-3-aryl -unsaturated esters, a diastereoselective protocol for the preparation of these alkenyl boronates through Heck coupling was developed. In Chapter 4, the optimization of the coupling process, the substrate scope, and the subsequent application of these alkenyl boronates are discussed.
Due to the synthetic potential of cyclic alkenyl boronates, new methods for their efficient synthesis are desirable. In Chapter 5, the preparation of novel cyclic alkenyl boronates through gold-catalyzed enyne cycloisomerizations is presented.
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- Citation for previous publication
Lee, J. C. H.; Hall, D. G. J. Am. Chem. Soc. 2010, 132, 5544–5555.Lee, J. C. H.; McDonald, R.; Hall, D. G. Nature Chem. 2011, 3 ,894−899.Ding, J.; Lee, J. C. H.; Hall, D. G. Org. Lett. 2012, 14, 4462−4465.Lee, J. C. H.; Hall, D. G. Tetrahedron Letters 2011, 52, 321–324.
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