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Ligand Effects on Reactivity and Selectivity of Transition-Metal Catalyzed Asymmetric C-C and C-N Bond Forming Reactions

Jesikiewicz, Luke (2020) Ligand Effects on Reactivity and Selectivity of Transition-Metal Catalyzed Asymmetric C-C and C-N Bond Forming Reactions. Master's Thesis, University of Pittsburgh. (Unpublished)

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Abstract

Homogenous catalysis using transition metals has grown to be one of the most common ways of forming chemical bonds in an enantioselective and regioselective manner. The role of the ancillary ligand in these processes is crucial in determining the desired stereochemical outcome. The origins of the effects of ligands that influence reactions to yield a specific product are not yet well understood. Herein, three studies that combine density functional theory (DFT) calculations and experimental data to further understand the role of the ligand in transition metal catalyzed reactions are reported. In the first study, the mechanisms and rate- and selectivity-determining steps of the copper-catalyzed asymmetric coupling of ketones and 1,3-butadiene were examined. The product selectivity is controlled by steric interactions from a combination of chiral ligand-substrate interactions and steric repulsions about the forming carbon-carbon bond in the Zimmerman-Traxler type ketone addition transition state. Next, a mechanistic study of the copper-catalyzed coupling of 1,3-enynes and nitriles demonstrated the selectivity was determined through steric interactions in the nitrile addition and cyclization steps of the reaction. Lastly, the study of the rhodium-catalyzed Pauson-Khand reaction of 1,6-enynes identified a key steric interaction between the substrate and the ligand in the oxidative cyclization transition state that controls the enantioselectivity. Additionally, this study demonstrated the importance of accounting for experimental conditions when performing DFT calculations. Taken together, these computational studies demonstrated the effective use of DFT calculations to study mechanisms, and the effects of ligands and substrates on reactivity and selectivity in transition metal-catalyzed reactions.


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Details

Item Type: University of Pittsburgh ETD
Status: Unpublished
Creators/Authors:
CreatorsEmailPitt UsernameORCID
Jesikiewicz, Luke
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairLiu, Pengpengliu@pitt.edupengliu
Committee MemberBrummond, Kay M.brummond@pitt.edubrummond
Committee MemberLaaser, Jenniferj.laaser@pitt.eduj.laaser
Date: 31 August 2020
Defense Date: 3 December 2019
Approval Date: 20 January 2021
Submission Date: 4 October 2020
Access Restriction: 1 year -- Restrict access to University of Pittsburgh for a period of 1 year.
Number of Pages: 78
Institution: University of Pittsburgh
Schools and Programs: Dietrich School of Arts and Sciences > Chemistry
Degree: MS - Master of Science
Thesis Type: Master's Thesis
Refereed: Yes
Uncontrolled Keywords: Density Functional Theory, Computational Chemistry, Organic Chemistry, Cross-coupling reaction, Pauson-Khand reaction, Copper, Rhodium
Date Deposited: 20 Jan 2021 19:34
Last Modified: 20 Jan 2021 19:34
URI: http://d-scholarship.pitt.edu/id/eprint/39853

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  • Ligand Effects on Reactivity and Selectivity of Transition-Metal Catalyzed Asymmetric C-C and C-N Bond Forming Reactions. (deposited 20 Jan 2021 19:34) [Currently Displayed]

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