Graduation Year

2023

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Chemistry

Major Professor

Wenqi Liu, Ph.D.

Co-Major Professor

Jianfeng Cai, Ph.D.

Committee Member

Kirpal Bisht, Ph.D.

Committee Member

Lei Wang, Ph.D.

Keywords

Ruthenium Carbene Catalysis, Metathesis, Au (I/III) catalysis, Asymmetric, Ligand Assisted Oxidative Addition, Alkene Oxyarylation

Abstract

This dissertation mainly contains three parts: 1) The discovery of triazole-modified Ru carbene catalysts for alkene metathesis and dynamic covalent chemistry; 2) The study of ligand assisted gold oxidative addition toward aryl iodide to achieve the alkene difunctionalization; 3) Gold redox catalysis via chiral P,N-chelating ligands. In the first part, the 1,2,3-triazole coordinated ruthenium carbene complexes (TA-Ru) were reported for the first time as a new class of modified Grubbs catalyst to achieve challenging olefin metathesis at higher temperatures without catalyst decomposition. With this new TA-Ru catalyst, cross-metathesis (CM), ring-closing metathesis (RCM) and dynamic covalent chemistry (DCvC) were achieved. The reactivity of TA-Ru prevails all previously reported N-coordinated Ru-carbene pre-catalysts, Grubbs II, and Hoveyda-Grubbs, making the TA-Ru a transformative catalytic system in olefin catalysis. The second study presents the intermolecular oxyarylation of alkenes catalyzed by gold. This research involved the oxidative coupling of aryl iodides with Me-DalphosAu+ to generate Au(III)-aryl intermediates. The superior affinity of alkenes for binding compared to oxygen nucleophiles ensured the effective execution of intermolecular oxyarylation, yielding the desired products across a wide range of substrates with impressive efficiency. This approach also enabled the one-pot transformation of methoxy groups into various other nucleophiles, facilitating alkene difunctionalization with the creation of C-N, C-S, and C-C bonds under mild reaction conditions. In the third part, enantioselective, intermolecular alkene arylamination was achieved through gold redox catalysis. Screening of ligands revealed chiral P,N ligands as the optimal choice, giving alkene aminoarylation with good yields (up to 80 %) and excellent stereoselectivity (up to 99 : 1 er). As the first example of enantioselective gold redox catalysis, this work confirmed the feasibility of applying a chiral ligand at the gold(I) stage, with the stereo-determining step (SDS) at the gold (III) intermediate, thus opening a new way to conduct gold redox catalysis with stereochemistry control. In summary, we not only developed a new catalytic system for olefin metathesis reaction but also explored a new strategy to achieve gold redox catalysis in catalytic version. Through careful design of the ligands, the first example of enantioselective Au (III) catalysis was reported.

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