자료유형  

 학위논문

Control Number  

0017164673

International Standard Book Number  

9798346866633

Dewey Decimal Classification Number  

547

Main Entry-Personal Name  

Rubel, Camille Z.

Publication, Distribution, etc. (Imprint  

[S.l.] : The Scripps Research Institute., 2024

Publication, Distribution, etc. (Imprint  

Ann Arbor : ProQuest Dissertations & Theses, 2024

Physical Description  

794 p.

General Note  

Source: Dissertations Abstracts International, Volume: 86-06, Section: B.

General Note  

Advisor: Engle, Keary M.

Dissertation Note  

Thesis (Ph.D.)--The Scripps Research Institute, 2024.

Summary, Etc.  

요약The two main factors that govern the properties of a transition metal catalyst are its ligand environment and its oxidation state. These attributes determine not only a catalyst's geometry, but also its solubility, redox activity, speciation, and size and polarizability. We hypothesized that altering Ni's ligand environment could influence its propensity to undergo changes in oxidation state, thereby leading to greater control over its reactivity. The interplay between reactivity and selectivity was studied in three settings: (i) as a stand-alone organometallic complex; (ii) while undergoing a change in oxidation state from NiII to Ni0; and (iii) as propagating catalysts during organic transformations.As a stand-alone organometallic complex, zerovalent sources of nickel are useful because nickel can enter a catalytic cycle directly through ligand exchange, without relying on changes in oxidation state to generate the desired catalyst. However, the primary source of Ni0 is Ni(COD)2 (COD = cyclooctadiene), an air- and temperature-sensitive solid that is unamenable to use on process scale. To overcome the limitations of Ni(COD)2, we created a toolkit of ten air and silica-gel-stable Ni0 precatalysts that lie further towards the reactivity side of the stability/reactivity continuum. We demonstrated how the Ni0 toolkit overcomes the limitations of both Ni(COD)2 and Ni(COD)(DQ) in reactions from the recent literature.Reduction of high valent nickel is invoked in reductive cross coupling catalysis, in-situ reduction to initiate a redox-neutral catalytic cycle, and the preparative generation of generate Ni0 organometallic complexes. The latter two frequently require harsh reductants. We recognized that electrochemistry, which relies on electrons and holes rather than their chemical surrogates, would be a more expedient way to access Ni(COD)2 and other common Ni0 precatalysts, including our own air-stable precatalyst toolkit. Reaction conditions were developed with a standard, commercial electrochemical cell, ultimately giving up to 85% yields of Ni(COD)2. Those conditions were general for of a variety of Ni0 complexes, including the aforementioned air-stable Ni0 complexes.Alkene isomerization is the most efficient way to form internal alkenes from terminal feedstocks, but controlling regio- and stereoselectivity with transition metal catalysts remains challenging. Ni-catalyzed Z- and E-selective alkene one-carbon transposition reactions were discovered. The key to these operationally simple, regioselective and stereodivergent reactions was the ability for Ni to traverse oxidation states through interaction with electrophiles to generate selective catalysts. This work also describes a tungsten-catalyzed, positionally selective alkene isomerization reaction in which tuning the ligand environment grants access to either the E- or Z-stereoisomer. Preliminary mechanistic studies suggest that the ligand environment around 7-coordinate tungsten is crucial for stereoselectivity, and that substrate directivity prevents over-isomerization to the conjugated alkene. These features allow for exclusive formation of β,γ-unsaturated carbonyl compounds that are otherwise difficult to prepare.The nickel-catalyzed difunctionalization of alkenes is a useful synthetic strategy for the generation of two C(sp3)-X bonds (X = C- or heteroatom-based groups). However, achieving reactivity with unactivated alkenes is challenging due to their lower binding strength to transition metals. To overcome the low reactivity of unactivated alkenes, our lab has employed directing groups that recruit metals towards the alkene. As part of our group's goal of using native directing groups to control reactivity with nickel, we thought to capitalize on nickel's affinity for the C=C double bonds in 1,5-cyclooctadiene (COD) to engage olefins as directing groups. Employing COD as substrate, nickel was found to catalyze the diarylation of one of the olefins, resulting in 5,6-diphenyl cyclooctene. These products were subjected to ring opening polymerization metathesis (ROMP) to form polymers with sequences with head-to-head styrene dyads, a previously unexplored structure due to the challenge of a de-novo synthesis of 5,6-diaryl cyclooctene.

Subject Added Entry-Topical Term  

Organic chemistry.

Subject Added Entry-Topical Term  

Polymer chemistry.

Subject Added Entry-Topical Term  

Physical chemistry.

Subject Added Entry-Topical Term  

Materials science.

Index Term-Uncontrolled  

Catalysis

Index Term-Uncontrolled  

Electrochemistry

Index Term-Uncontrolled  

Isomerization

Index Term-Uncontrolled  

Nickel

Index Term-Uncontrolled  

Polymers

Index Term-Uncontrolled  

Tungsten

Added Entry-Corporate Name  

The Scripps Research Institute Chemistry

Host Item Entry  

Dissertations Abstracts International. 86-06B.

Electronic Location and Access  

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Control Number  

joongbu:656429