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Permanent link (DOI): https://doi.org/10.7939/R3J960H1D
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Exploring New Aspects of the Nazarov Cyclization Open Access
- Other title
Interrupted Nazarov reaction
Alternative Nazarov reaction
- Type of item
- Degree grantor
University of Alberta
- Author or creator
- Supervisor and department
West, F. G. (Chemistry)
- Examining committee member and department
Suzuki, Keisuke (Chemistry, Tokyo Institute of Technology)
Lowary, Todd L. (Chemistry)
Campbell, Robert E. (Chemistry)
MacMillan, Andrew M. (Biochemistry)
Clive, Derrick L. J. (Chemistry)
Department of Chemistry
- Date accepted
- Graduation date
Doctor of Philosophy
- Degree level
The five-membered carbocyclic framework is a prevailing structural motif found in natural products and bioactive compounds. Over the years, the Nazarov reaction has been continuously refined as a versatile protocol to access cyclopentanoid products. In this dissertation, several projects built on Nazarov chemistry will be detailed.
Recent research activities regarding umpolung reactivity at the carbonyl α-carbon, a relatively underemphasized carbonyl umpolung, is discussed in Chapter 1. The cationic intermediates generated during the Nazarov cyclization have been shown to participate in domino or cascade sequences, thus providing a convenient entry to expeditiously increase molecular complexity from relatively simple precursors. Chapter 2 describes a comprehensive investigation of new bond-forming reactions initiated by the Nazarov reaction wherein umpolung reactivity at the α-carbon of cyclopentanones was achieved through the interception of 2-oxidocyclopentenyl cations derived from the initial electrocyclization with an array of carbon nucleophiles.
Alternative substrates to the key pentadienyl cation intermediate in the Nazarov reaction, potentially offering access to unconventional substitution patterns or milder conditions, have recently attracted considerable interest. Chapter 3 discusses the use of vinyl silyloxyallenes, which function as dienone surrogates through Brønsted acid activation, to effect the Nazarov cyclization. Additionally, a novel extension of the vinyl allene version of the Nazarov reaction, involving an interrupted Nazarov reaction employing pendent aromatic traps will be presented.
Chapter 4 recounts a novel, two-step, modular synthesis of α-amidoindanones. This process is based upon the Nazarov cyclization of 2-amido-1,4-pentadien-3-ones that were in turn prepared via a novel coupling process between α,β-unsaturated aldehydes and an α-lithiated allenamide. As supported by a deuterium labelling study, the mechanism of the coupling entails sequential carbonyl addition and 1,3-sigmatropic rearrangement.
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- Citation for previous publication
Wu, Y.-K.; Niu, T.; West, F. G.*: “Construction of α-Amido-indanones via Formal Allenamide Hydroacylation/Nazarov Cyclization,” Chem. Commun. 2012, 48, 9186-9188.Wu, Y.-K.; McDonald, R.; West, F. G.*: “Homologous Mukaiyama Reactions via Trapping of the Nazarov Intermediate with Silyloxyalkenes,” Org. Lett. 2011, 13, 3584-3587.Wu, Y.-K.; West, F. G.*: “Brønsted Acid-Mediated Nazarov Cyclization of Vinylallenes,” J. Org. Chem. 2010, 75, 5410-5413.
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