Enantioselective conjugate addition (ECA) reactions between organometallic reagents and cyclohexadienone 165 are being investigated. Previous studies have shown that ECAs, of organometallic reagents to á,â-unsaturated cyclohexadienones, are useful in many natural product syntheses. The substrates used in earlier studies were simple 2,5-cyclohexadienones, with a proton at the C-3 position, resulting in the synthesis of a trisubstituted C-3 atom. ECAs that afford all-carbon quaternary stereogenic centers are a much more challenging problem and few examples have been reported. Some natural products contain a ã-hydroxy group, however, no ECA substrates have incorporated this motif. ECAs have been accomplished with substrates having a g-ether substituent. The cyclohexadienone 165 system presents three challenging problems to overcome for an ECA reaction: the tertiary methyl substituents at the 3 and 5 positions, facial selectivity and enantioselectivity. An ECA to 165 using an organoaluminum reagent and an external chiral ligand 26 was successful in producing a product that showed the reaction was moderately stereoselective. A diastereoselective conjugate addition reaction (DCA) to 165 using a chiral auxiliary 68 was also successful in producing a product that showed the reaction was moderately enantioenriched. Lastly, a variable temperature NMR study was performed to establish the presence of dynamic motions of the C=N bond present in sulfinyl imines 229 and 230. As a result, the sulfinyl imines 229 and 230 were found to be interconverting at -78°C.
| Identifer | oai:union.ndltd.org:USASK/oai:usask.ca:etd-11282007-103240 |
| Date | 03 December 2007 |
| Creators | Mulligan, Kirk Michael |
| Contributors | Majewski, Marek, Gravel, Michel, Abrams, Sue |
| Publisher | University of Saskatchewan |
| Source Sets | University of Saskatchewan Library |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://library.usask.ca/theses/available/etd-11282007-103240/ |
| Rights | restricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Saskatchewan or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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