Asymmetric epoxidation of various olefins catalyzed by fructose- and glucose-derived ketones
| dc.contributor.author | Wong, On Lo Andrea, author | |
| dc.contributor.author | Shi, Yian, advisor | |
| dc.date.accessioned | 2024-03-13T20:28:05Z | |
| dc.date.available | 2024-03-13T20:28:05Z | |
| dc.date.issued | 2009 | |
| dc.description.abstract | Numerous laboratories have studied dioxirane- and oxaziridinium-mediated epoxidations during the past two decades. Many chiral ketone and iminium salt catalysts, bearing a wide variety of structural features, have been investigated. Out of the systems studied a fructose-derived ketone has been proven to be one of the most general and practical catalysts. This catalyst epoxidizes trans- and trisubstituted olefins in good yield and enantioselectivity, and it has been employed in the syntheses of many complex molecules. In efforts to expand the substrate scope a series of glucose-derived, oxazinolidine-bearing ketones were reported to be excellent catalysts for the epoxidation of conjugated cis-olefins. The stereodifferentiation in the epoxidation transition state originates from the attraction between the N-substituent of the oxazolidinone and the Rπ substituent on the olefin. The existence of this interaction was supported by the observation that 6-substituted chromenes were epoxidized with higher enantioselectivities than 8-substituted chromenes. Using this glucose-derived ketone system, substituted chiral styrene oxides could be obtained in 80-92% ee. Fluoroolefins were investigated as epoxidation substrates with several fructose- and glucose-derived ketone catalysts. A fluorine substituent was found to improve enantioselectivity in some cases but was detrimental to enantioselectivity in others. The substrate scope of a diacetate-containing ketone was expanded. High enantioselectivities were obtained for the epoxidation of trans- and trisubstituted olefins, and cis-olefins bearing a bulky substituent. The optical rotations of the resulting cis-epoxides were opposite to those obtained using glucose-derived ketones. 1,1-Disubstituted terminal olefins were epoxidized in good enantioselectivities with a glucose-derived morpholinone ketone. From the absolute configuration of the resulting epoxides, the major transition state appears to be a planar-like transition state. Also studied was a glucose-derived dimethylmorpholinone ketone that has the combined features of several of the previously studied ketones. This catalyst epoxidizes trans- and trisubstituted olefins in high enantoselectivities, but compared to the oxazolidinone-containing ketones gives slightly lower enantioselectivities with cis- and 1,1-disubstituted olefin substrates. Lastly, the epoxidation transition state model was studied using 18O-labeled ketone catalysts, and the results support the currently accepted transition state model. | |
| dc.format.medium | born digital | |
| dc.format.medium | doctoral dissertations | |
| dc.identifier | ETDF_Wong_2009_3401031.pdf | |
| dc.identifier.uri | https://hdl.handle.net/10217/238026 | |
| 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.rights.license | Per the terms of a contractual agreement, all use of this item is limited to the non-commercial use of Colorado State University and its authorized users. | |
| dc.subject | dioxirane | |
| dc.subject | epoxidation | |
| dc.subject | fructose | |
| dc.subject | glucose | |
| dc.subject | ketones | |
| dc.subject | olefins | |
| dc.subject | organic chemistry | |
| dc.title | Asymmetric epoxidation of various olefins catalyzed by fructose- and glucose-derived ketones | |
| 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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