Thesis
Studies toward the development of novel coupling reactions
- Creator
- Rights statement
- Awarding institution
- University of Strathclyde
- Date of award
- 2023
- Thesis identifier
- T16675
- Person Identifier (Local)
- 201971963
- Qualification Level
- Qualification Name
- Department, School or Faculty
- Abstract
- This thesis contains three chapters of results. The aim across all three chapters is to better understand the mechanisms of novel reactions discovered in the Murphy Group. Ground State Electron Transfer from KOtBu in the Reduction of Aryl Halides (Chapter 2) Transition metal-free coupling reactions of aryl halides to arenes have received much attention in recent years. The coupling reaction, which involves alkali metal alkoxides as base and is better known as base-promoted homolytic aromatic substitution, or BHAS, involves an alkali metal butoxide base and is initiated by electron transfer. Some literature reports have proposed that the alkoxides can provide the initiating electrons, but to date there is little evidence provided in support of such proposals. To directly address this, this thesis reports findings with substrates such as (i) (Scheme IV-I). Efficient coupling was observed. In addition, methylation afforded (ii). The methylation is strong evidence for the formation of methyl radicals (vi) via the fragmentation of tertbutoxyl radicals (iv). The identity of the species that facilitates the initial electron transfer from KOtBu that leads to tert-butoxyl radicals was explored. [See thesis text for Figure Scheme IV-I. The methylation of arenes supports ground-state electron transfer from KOtBu]. Novel Reactions of Benzyne (Chapter 3) Few reports in the early literature propose radicals when interpreting the outcomes of reactions of benzyne. This thesis provides unambiguous evidence for diradical intermediates in reactions of benzyne for the first time (Scheme IV-II). Furthermore, benzyne can initiate such chemistry via a molecule-induced radical formation (MIRF) reaction. The findings in this thesis add to the collection of novel and emerging reactivity observed for benzynes. This thesis also reports pericyclic reactions of benzyne with benzenes. [See thesis text for Figure Scheme IV-II. Evidence of diradical intermediates via MIRF reactions of benzyne.] The KOtBu-Et3SiH Reagent System (Chapter 4) The combination of KOtBu and Et3SiH, known as the Grubbs-Stoltz reagent, mediates many transformations by a range of mechanisms. To account for such diversity, key reactive species have previously been proposed. Silicate intermediate (ix) has been proposed to mediate hydride transfer mechanisms, in equilibrium with KH (x) and silyl ether (xi) (Figure IV-I). Radical and single electron transfer pathways have also been proposed to involve triethylsilyl radicals (xii) and tert-butoxytriethylsilyl radical anion (xiii). [See thesis text for Figure Figure IV-I. Proposed species that are involved in the reactions of KOtBu-Et3SiH]. Studies of the reagent system have uncovered a novel intermolecular alkylation reaction with ether solvents (Scheme IV-III). The mechanism of the reaction was thoroughly studied and the methodology developed to incorporate intramolecular alkylations of alcohols and ethers that afforded cyclopentane and cyclopropane products. A novel SN2-type substitution of ethers was proposed as part of the mechanism that cleaves C-O bonds. [See thesis text for Figure Scheme IV-III. A novel intermolecular alkylation reaction with tetrahydrofuran as an alkylating agent uncovered a new methodology to produce cyclopentanes and cyclopropanes].
- Advisor / supervisor
- Murphy, John A., 1948-
- Resource Type
- Note
- This thesis was previously held under moratorium from 17th August 2023 until 17th August 2025.
- DOI
- Funder
- Embargo Note
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File | 2023-08-18 | Embargo |