Thesis advisor: Amir H. Hoveyda / Chapter 1 Enantioselective Conjugate Additions of Carbon Nucleophiles to Activated Olefins: Preparation of Enantioenriched Compounds Containing All-Carbon Quaternary Stereogenic Centers. Methods for enantioselective conjugate addition of nucleophiles to activated olefins generating products containing all-carbon quaternary stereogenic centers are critically reviewed. Enantioselective conjugate addition has been shown to be a powerful and concise approach to construct carbon-carbon bonds to prepare compounds containing sterically hindered stereogenic centers and has seen great advances in the past several years. Owing to the difficult nature of additions to relatively unreactive conjugate acceptors, compared to additions generating tertiary stereogenic centers, and construction of a sterically-hindered bond, in many cases, new and active catalysts had to be developed. The review discusses the areas where significant advances have been made as well as current limitations and future outlook. Chapter 2 Development of New and Active Catalysts for Cu-Catalyzed Enantioselective Conjugate Addition of Alkyl- and Arylzinc Reagent. Through development of new chiral catalysts, we have found an active and enantiodiscriminating bidentate, sulfonate-containing NHC-Cu catalyst that effects enantioselective conjugate addition of alkyl- and arylzinc reagents on notoriously difficult trisubstituted cyclic enones. Products are prepared with high levels of selectivity and participate in a variety of further functionalizations. The enantioselective additions are efficient and practical, not requiring rigorously anhydrous or oxygen-free conditions. Chapter 3 Cu-Catalyzed Enantioselective Conjugate Addition of Alkyl- and Arylaluminum Reagents to Trisubstituted Enones. Outlined in this chapter is the first effective solution for Cu-catalyzed enantioselective addition of alkyl and aryl nucleophiles to trisubstituted cyclopentenones generating products bearing a β-all-carbon quaternary stereogenic center. Products are obtained in up to 97% yield and 99:1 er, only requiring 5 mol % of an in situ generated Cu-NHC catalyst. The methodology was highlighted as one of the key steps in the total synthesis of clavirolide C. Not only five-membered rings, but six- and seven-membered rings serve as proficient partners in the enantioselective process. Moreover, in cases for the enantioselective aryl addition, in situ prepared Me<sub>2</sub>AlAr can be used without purification, filtration, or isolation, only requiring the corresponding aryl halides. The additions have also been extended to trisubstituted unsaturated lactones and chromones. Chapter 4 Cu-Catalyzed Enantioselective Conjugate Addition of Vinylaluminum Reagents to Cyclic Trisubstituted Enones. An enantioselective protocol for the formation of β,β-disubstituted cyclic ketones containing a synthetically versatile vinylsilane is disclosed. Enantioselective conjugate addition of in situ prepared silyl-substituted vinylaluminum reagents to β,β-unsaturated ketones promoted by 5 mol % of chiral Cu-NHC complexes delivers desired products with high efficiency (up to 95% yield after purification) and enantioselectivities (up to >98:<2 er). Several functionalizations utilizing the vinylsilanes, vicinal to an all-carbon quaternary stereogenic center, are shown, including an oxidative rearrangement, vinyl iodide formation and protodesilylation, accessing products not previously attainable. Furthermore, the enantioselective protocol is demonstrated as the key transformation in the total synthesis of riccardiphenol B. / Thesis (PhD) — Boston College, 2011. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.
| Identifer | oai:union.ndltd.org:BOSTON/oai:dlib.bc.edu:bc-ir_101471 |
| Date | January 2011 |
| Creators | May, Tricia Lee |
| Publisher | Boston College |
| Source Sets | Boston College |
| Language | English |
| Detected Language | English |
| Type | Text, thesis |
| Format | electronic, application/pdf |
| Rights | Copyright is held by the author, with all rights reserved, unless otherwise noted. |
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