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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

Descriptions

Other title
Subject/Keyword
Nazarov reaction
Domino
Umpolung
vinylallene
Interrupted Nazarov reaction
Alternative Nazarov reaction
allenamide
Type of item
Thesis
Degree grantor
University of Alberta
Author or creator
Wu, Yen-Ku
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
Department of Chemistry
Specialization

Date accepted
2013-02-19T09:07:37Z
Graduation date
2013-06
Degree
Doctor of Philosophy
Degree level
Doctoral
Abstract
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.
Language
English
DOI
doi:10.7939/R3J960H1D
Rights
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.
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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