Graduation Year

2022

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Chemistry

Major Professor

Xiaodong Micheal Shi, Ph.D.

Committee Member

Jianfeng Cai, Ph.D.

Committee Member

Kirpal Bisht, Ph.D.

Committee Member

Libin Ye, Ph.D.

Keywords

asymmetric, Au (I/III) catalysis, HFIP, mild oxidant, Pd/Amine catalysis

Abstract

This dissertation mainly contains three parts: 1) The synergistic Pd/enamine catalysis for asymmetric hydrocarbon functionalization of unactivated alkenes with ketones; 2) Gold redox catalysis with a selenium cation as mild oxidant; 3) HFIP promoted disulfidation and diselenation of alkyne, alkene, and allene.

Palladium-catalyzed alkene activation has its intrinsic limitation: 1) the requirement of a pre-functionalized alkene to form a Pd π-allyl complex; 2) problematic reversible β-H elimination. It always leads to limited reaction scope and losing of the stereochemical control. Synergistic palladium and enamine catalysis was conducted to promote ketone addition to unactivated olefins. A secondary amine-based organocatalyst was identified as the optimal co-catalyst for the directed Pd-catalyzed alkene activation. Furthermore, asymmetric hydrocarbofunctionalization of unactivated alkenes was also achieved with good to excellent yield and stereoselectivity.

Au redox catalysis always requires strong oxidants or delicate ligand design, which largely limites the reaction scope. In this part, we utilized selenide cation as mild oxidant to achieve Au oxidation. Excellent regioselectivity (trans) and good to excellent yields were achieved (up to 98% with 2% catalyst loading) with a wide range of substrates. Mechanistic investigation revealed a gold (I/III) redox process was successfully implemented under mild conditions.

Among various factors that can affect reactions, the solvent is the one that can dramatically impact the reaction performance. We accidentally observed Hexafluoro-2-propanol (HFIP), as a unique polar organic solvent that can promote the diselenation and disulfidation of C-C unsaturated bonds successfully. In contrast, other solvents, such as isopropanol and dichloroethane, could not promote the same reaction. This method revealed an example of HFIP promoted transformations under mild conditions, which greatly highlighted the unique reactivity of this special solvent.

In sum, the combination of transition metal catalyst and organic catalyst can promote a reaction in a highly efficient process and greatly extend the reaction scope, even providing stereoselectivity successfully. Appling mild oxidant in Au redox catalysis is able to achieve Au (III) and holds promise for generating synthetically valuable building blocks, which also enhance the basic understand of this rapidly growing field. HFIP as a magic solvent exhibits the stability to activate diselenides and disulfides to accomplish addition to C-C unsaturated bonds.

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