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Formal radical cyclization onto aromatic rings, cascade intramolecular conjugate displacement and synthetic studies on marinopyrroles Open Access

Descriptions

Other title
Subject/Keyword
ICD
radical cyclization
marinopyrroles
Type of item
Thesis
Degree grantor
University of Alberta
Author or creator
Chen, Zhenhua
Supervisor and department
Clive, D.L.J. (Chemistry)
Examining committee member and department
Bergens, Steven H. (Chemistry)
Wee, Andrew (Chemistry and Biochemistry, University of Regina)
Clive, D.L.J. (Chemistry)
Schieber, Andreas (Agricultural Food and Nutritional Science)
West, Frederick G. (Chemistry)
Vederas, John C. (Chemistry)
Department
Department of Chemistry
Specialization

Date accepted
2012-05-31T11:49:09Z
Graduation date
2011-11
Degree
Doctor of Philosophy
Degree level
Doctoral
Abstract
The first chapter of this thesis describes the development of a general method for indirectly effecting radical carbocyclization of an alkyl chain onto an aromatic ring. This process involves a Birch reductive alkylation of aromatic tert-butyl esters, chromium(VI)-mediated oxidation and radical cyclization. The cyclized products are easily oxidized to the corresponding cross-conjugated ketones via Saegusa oxidation. Addition of organolithium or Grignard reagents and treatment with bismuth trichloride affords aromatized benzo-fused carbocycles. The second chapter describes a method for converting Morita-Baylis-Hillman acetates into unusual seven-membered heterocycles containing both nitrogen and sulfur. N-Deprotection of the MBH acetates and trapping with CS2 affords the desired 2-thioxo-1,3-thiazepines. In a modification of this process, when the original nitrogen is substituted with a carbon chain, an azepine derivative is generated. The ring closures occur by intramolecular conjugate displacement. The last chapter of this thesis describes synthetic studies towards the marine antibiotic alkaloid, marinopyrrole B. Due to the difficulty of bromination of the pyrrole system, it is known that marinopyrrole B cannot be directly made from marinopyrrole A. Our plan was based on brominating the bottom pyrrole at an early stage and constructing the top pyrrole ring later. Previous studies towards the core structure of marinopyrrole A suggested that the Paal-Knorr reaction is an ideal method for construction of the top ring. Preparation of the precursor for the Paal-Knorr reaction was planned via an intermolecular conjugate displacement between a densely halogenated pyrrole and a Morita-Baylis-Hillman carbonate. However, this approach was unsuccessful and further studies are in hand.
Language
English
DOI
doi:10.7939/R3VM3Z
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
Chen, Zhenhua (2011) American Chemical Society,  http://pubs.acs.org/doi/abs/10.1021/jo101539m?journalCode=joceah&quickLinkVolume=75&quickLinkPage=7014&volume=75Chen
, Zhenhua (2008) Royal Society of Chemistry,  http://pubs.rsc.org/en/content/articlelanding/2008/ob/b803308k

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File title: Zhenhua's Thesis Final 2011 September 25e
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