Development of asymmetric N-heterocyclic carbene-catalyzed reactions
| dc.contributor.author | Flanigan, Darrin Miles, author | |
| dc.contributor.author | Rovis, Tomislav, advisor | |
| dc.contributor.author | Chen, Eugene, committee member | |
| dc.contributor.author | Shi, Yian, committee member | |
| dc.contributor.author | Chatterjee, Delphi, committee member | |
| dc.date.accessioned | 2017-09-14T16:05:28Z | |
| dc.date.available | 2017-09-14T16:05:28Z | |
| dc.date.issued | 2017 | |
| dc.description.abstract | N-Heterocyclic carbenes (NHCs) are ubiquitous organocatalysts in a variety of asymmetric transformations. The benzoin and Stetter reactions, which couple aldehydes to other aldehydes or Michael acceptors, respectively are the most commonly reported reactivity manifold employing NHC catalysts. However, other umpolung reactivity pathways exist, for example, when α,β-unsaturated aldehydes are reacted with NHCs, the Breslow intermediate can react through the double bond of the aldehyde to functionalize at the beta position of the carbonyl. A process that has come to be known has homoenolate reactivity. A range of reactivity manifolds were investigated, including the asymmetric intermolecular Stetter reaction and an enantioselective NHC-catalyzed nucleophilic dearomatization of pyridiniums. In the dearomatization chemistry, a homoenolate equivalent is first generated from an enal and an NHC, which then adds to the pyridinium to generate 1,4-dihydropyridines with high enantioselectivity. This is a rare example of catalytic, asymmetric addition of a nucleophile to the activated pyridinium that prefers C-4 functionalization leading to the 1,4-dihydropyridine product. The asymmetric intermolecular Stetter reaction was also investigated in an attempt to broaden the scope of the reaction to include less activated Michael acceptors, specifically, α,β-unsaturated ketones. The coupling of heteroaryl aldehydes to enones could be achieved with appreciable levels of enantioselectivity (up to 80% ee), but reactivity remains a major challenge with this methodology. | |
| dc.format.medium | born digital | |
| dc.format.medium | doctoral dissertations | |
| dc.identifier | Flanigan_colostate_0053A_14334.pdf | |
| dc.identifier.uri | https://hdl.handle.net/10217/183966 | |
| dc.language | English | |
| dc.language.iso | eng | |
| dc.publisher | Colorado State University. Libraries | |
| dc.relation.ispartof | 2000-2019 | |
| dc.rights | Copyright 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.subject | organic chemistry | |
| dc.subject | n-heterocyclic carbenes | |
| dc.subject | organocatalysis | |
| dc.title | Development of asymmetric N-heterocyclic carbene-catalyzed reactions | |
| dc.type | Text | |
| dcterms.rights.dpla | This 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.discipline | Chemistry | |
| thesis.degree.grantor | Colorado State University | |
| thesis.degree.level | Doctoral | |
| thesis.degree.name | Doctor of Philosophy (Ph.D.) |
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