NHC-catalyzed transformations: Stetter, benzoin, and ring expansion reactions
| dc.contributor.advisor | Gravel, Michel | en_US |
| dc.contributor.committeeMember | Majewski, Marek | en_US |
| dc.contributor.committeeMember | Wilson, Lee | en_US |
| dc.contributor.committeeMember | Attah-Poku, Sam | en_US |
| dc.contributor.committeeMember | Pedras, Soledade M. | en_US |
| dc.creator | Thai, Karen | en_US |
| dc.date.accessioned | 2013-09-16T19:52:16Z | |
| dc.date.available | 2013-09-16T19:52:16Z | |
| dc.date.created | 2012-06 | en_US |
| dc.date.issued | 2013-07-29 | en_US |
| dc.date.submitted | June 2012 | en_US |
| dc.description.abstract | N-Hetereocyclic carbenes (NHC) have been intensively investigated since Ukai et al had reported the first NHC-catalyzed coupling of two equivalents of benzaldehyde, to form what is known as the benzoin product. A plethora of reports have since been published on NHC-catalyzed reactions, such as the cross-benzoin, Stetter, redox reactions, and many others. An attractive feature of NHCs is their ability to effect the umpolung (inversion of reactivity) of aldehydes. The efforts in the introduction of β,γ-unsaturated-α-ketoesters as acceptors for the Stetter reaction have led to the first highly enantioselective intermolecular Stetter reaction with β-aryl substituted Stetter acceptors (up to >99% ee). The synthetic applications of the Stetter adducts generated from the α-ketoester acceptors were demonstrated to give access to a diverse number of useful building blocks. Furthermore, the α-ketoester substrates were found to also be applicable for the cross-benzoin reaction. Through the development of a new electron-deficient, morpholine-based triazolium-derived carbene, a highly chemo- and enantioselective cross-benzoin reaction was achieved using aliphatic aldehydes and α-ketoesters. This methodology constitutes as the first highly enantioselective intermolecular cross-benzoin reaction with aliphatic aldehydes (up to 93% ee). In addition, a highly divergent synthesis of Stetter adducts and cross-benzoin products could be achieved in excellent regioselectivity. Interested in utilizing NHCs as organocatalysts for the development of new reactions, tetrahydrofuran and prolinal derivatives were found to undergo efficient ring-expansions. This methodology gives access to highly functionalized lactones and lactams, which could serve as synthetically useful building blocks for the synthesis of natural products and biologically active compounds. | en_US |
| dc.identifier.uri | http://hdl.handle.net/10388/ETD-2012-06-489 | en_US |
| dc.language.iso | eng | en_US |
| dc.subject | organocatalysis, carbenes, umpolung | en_US |
| dc.title | NHC-catalyzed transformations: Stetter, benzoin, and ring expansion reactions | en_US |
| dc.type.genre | Thesis | en_US |
| dc.type.material | text | en_US |
| thesis.degree.department | Chemistry | en_US |
| thesis.degree.discipline | Chemistry | en_US |
| thesis.degree.grantor | University of Saskatchewan | en_US |
| thesis.degree.level | Doctoral | en_US |
| thesis.degree.name | Doctor of Philosophy (Ph.D.) | en_US |