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Boston College

1. Lee, Yunmi. Site- and Enantioselective C-C and C-B Bond Forming Reactions Catalyzed by Cu-, Mg-, Zn-, or Al-based N-Heterocyclic Carbene Complexes.

Degree: PhD, Chemistry, 2010, Boston College

Chapter 1. In this chapter, the ability of chiral bidentate N-heterocyclic carbenes (NHCs) to activate alkylmetal reagents directly in order to promote C‒C bond forming reactions in the absence of a Cu salt is presented. Highly regio- and enantioselective Cu-free allylic alkylation reactions of di- and trisubstituted allylic substrates with organomagnesium, organozinc, and organoaluminum reagents are demonstrated. Chiral bidentate sulfonate-bearing NHC-Zn and NHC-Al complexes are isolated and fully characterized. Based on crystal structures of these catalytic complexes, mechanistic details regarding Cu-free allylic alkylations with alkylmetal reagents are proposed. Chapter 2. New methods for efficient and highly enantioselective Cu-catalyzed allylic alkylation reactions of a variety of trisubstituted allylic substrates with alkylmagnesium and alkyl-, aryl-, 2-furyl-, and 2-thiophenylaluminum reagents are presented. Transformations are promoted by a chiral NHC complex in the presence of commercially available, inexpensive and air stable CuCl2*H2O. Enantiomerically enriched compounds containing difficult-to-access all-carbon quaternary stereogenic centers are obtained. Chapter 3. New methods for highly site- and enantioselective Cu-catalyzed allylic alkylation reactions of allylic phosphates with vinylaluminum reagents are presented. The requisite vinylaluminums are prepared by reaction of readily accessible terminal alkynes with DIBAL-H and used directly without further purification. Vinyl additions are promoted in the presence of a chiral bidentate sulfonate-based NHC complex and a Cu salt. The desired SN2' products are obtained in >98% E selectivities, >98% SN2' selectivities, >98% group selectivities (<2% i-Bu addition) and high enantioselectivities. The enantioselective total synthesis of the natural product bakuchiol highlights the versatility of the one-pot hydroalumination/Cu-catalyzed enantioselective allylic vinylation process. Chapter 4. Efficient and highly site-selective Cu-catalyzed hydroboration reactions of 1,2-disubstituted aryl olefins with bis(pinacolato)diboron (B2(pin)2) are presented. Transformations are promoted by an NHC-Cu complex in the presence of MeOH, affording only secondary β-boronate isomers. A Cu-catalyzed method for the synthesis of enantiomerically enriched secondary alkylboronates promoted by chiral NHC complexes is disclosed. Chapter 5. A new method for efficient and site-selective tandem Cu-catalyzed copper-boron additions to terminal alkynes with B2(pin)2 in the presence of an NHC-Cu complex is demonstrated. In a one-pot process, Cu-catalyzed hydroboration of alkynes provides vinylboronates in situ, which undergo a second site-selective hydroboration to afford vicinal diboronates. Highly Enantiomerically enriched diboronates obtained through Cu-catalyzed enantioselective dihydroboration in the presence of chiral bidentate sulfonate-based NHC-Cu complex are obtained. The control of site selectivity in the first-stage hydroboration of alkynes is critical for efficient and… Advisors/Committee Members: Amir H. Hoveyda (Thesis advisor).

Subjects/Keywords: Cu-catalyzed reaction; Dihydroboration; Enantioselective Allylic Alkylation; Hydroboration; N-Heterocyclic carbene

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Lee, Y. (2010). Site- and Enantioselective C-C and C-B Bond Forming Reactions Catalyzed by Cu-, Mg-, Zn-, or Al-based N-Heterocyclic Carbene Complexes. (Doctoral Dissertation). Boston College. Retrieved from http://dlib.bc.edu/islandora/object/bc-ir:101999

Chicago Manual of Style (16th Edition):

Lee, Yunmi. “Site- and Enantioselective C-C and C-B Bond Forming Reactions Catalyzed by Cu-, Mg-, Zn-, or Al-based N-Heterocyclic Carbene Complexes.” 2010. Doctoral Dissertation, Boston College. Accessed October 19, 2019. http://dlib.bc.edu/islandora/object/bc-ir:101999.

MLA Handbook (7th Edition):

Lee, Yunmi. “Site- and Enantioselective C-C and C-B Bond Forming Reactions Catalyzed by Cu-, Mg-, Zn-, or Al-based N-Heterocyclic Carbene Complexes.” 2010. Web. 19 Oct 2019.

Vancouver:

Lee Y. Site- and Enantioselective C-C and C-B Bond Forming Reactions Catalyzed by Cu-, Mg-, Zn-, or Al-based N-Heterocyclic Carbene Complexes. [Internet] [Doctoral dissertation]. Boston College; 2010. [cited 2019 Oct 19]. Available from: http://dlib.bc.edu/islandora/object/bc-ir:101999.

Council of Science Editors:

Lee Y. Site- and Enantioselective C-C and C-B Bond Forming Reactions Catalyzed by Cu-, Mg-, Zn-, or Al-based N-Heterocyclic Carbene Complexes. [Doctoral Dissertation]. Boston College; 2010. Available from: http://dlib.bc.edu/islandora/object/bc-ir:101999

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