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Rhodium-catalyzed cycloadditions between alkenyl isocyanates and alkynes: study of scope, mechanism and applications toward total synthesis

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dc.contributor.authorFriedman, Rebecca Ann Keller, author
dc.contributor.authorRovis, Tomislav, 1968-, advisor
dc.contributor.authorKennan, Alan J., committee member
dc.contributor.authorPrieto, Amy L. (Amy Lucia), committee member
dc.contributor.authorShi, Yian, committee member
dc.contributor.authorMcNeil, Michael R., committee member
dc.date.accessioned2007-01-03T04:52:09Z
dc.date.available2007-01-03T04:52:09Z
dc.date.issued2010
dc.description.abstractRhodium-catalyzed cycloadditions between alkenyl isocyanates and unsymmetrical, internal alkynes has been studied. A wide variety of alkynes have proven successful components in the [2+2+2] cycloaddition. Excellent yields and enantioselectivities have been achieved in the resulting indolizidinone products. Furthermore, a single regioisomer is obtained for the vast majority of alkynes subjected to reaction conditions. A logical explanation for the highly regioselective insertion for internal, unsymmetrical alkynes was provided. Small variations in the electronics and/or steric bulk of the alkyne substitution were sufficient to predictably control the insertion of the alkyne into the initial rhodacycle. Mechanistic insight into the rhodium-catalyzed [4+2+2] cycloaddition between dienyl isocyanates and alkynes has been achieved. A series of competition and slow addition experiments, alongside analysis of enantioselectivity and product formation, provided evidence for a proposed mechanism of the [4+2+2] cycloaddition. It was determined that the diene preferentially coordinates to the rhodium, in the presence of a terminal alkyne, to provide eight-membered bicyclic azocene products. Steps towards the total synthesis of natural product Secu'amamine A have been made. The bicyclic core of the molecule has been successfully synthesized utilizing rhodium-catalyzed [2+2+2] methodology developed within the Rovis group. Additionally, a successful, diastereoselective 1,4-reduction of the resulting vinylogous amide product and subsequent deprotection of an enyne side-chain provided an intermediate that is hypothetically two steps (an alpha-oxidation and 2+2+1 cycloaddition) away from Secu'amamine A.
dc.format.mediumborn digital
dc.format.mediumdoctoral dissertations
dc.identifierFriedman_colostate_0053A_10119.pdf
dc.identifier.urihttp://hdl.handle.net/10217/44960
dc.languageEnglish
dc.language.isoeng
dc.publisherColorado State University. Libraries
dc.relation.ispartof2000-2019
dc.rightsCopyright and other restrictions may apply. User is responsible for compliance with all applicable laws. For information about copyright law, please see https://libguides.colostate.edu/copyright.
dc.subjectorganometallic
dc.subjectmethodology
dc.subjectcycloaddition
dc.subjectAlkynes
dc.subjectRhodium catalysts
dc.subjectRing formation (Chemistry)
dc.subjectCombinatorial chemistry
dc.titleRhodium-catalyzed cycloadditions between alkenyl isocyanates and alkynes: study of scope, mechanism and applications toward total synthesis
dc.typeText
dcterms.rights.dplaThis Item is protected by copyright and/or related rights (https://rightsstatements.org/vocab/InC/1.0/). You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).
thesis.degree.disciplineChemistry
thesis.degree.grantorColorado State University
thesis.degree.levelDoctoral
thesis.degree.nameDoctor of Philosophy (Ph.D.)

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