Developments in sustainable C-C bond forming reactions

Bates, Samuel 2022. Developments in sustainable C-C bond forming reactions. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

This thesis focuses on the development of two sustainable C-C bond forming reactions, which would be useful in potential borrowing hydrogen carboxylation reactions. One project involves the development of a novel CO2 utilisation process. The other projects consist of development of novel catalytic systems for the upgrading of ethanol, via the Guerbet reaction, into butanol, a potential drop-in replacement for petrol. The aim of the first project was to develop a Kolbe-Schmitt type carboxylation process, which operated under mild conditions in organic solvents. Triazabicyclodecene (TBD) was discovered to improve the carboxylation of sodium 2-naphthoxide in toluene. TBD also mediated the selective carboxylation of 2-naphthol under mild conditions in THF, which was the first discovery of a metal-free carboxylation of naphthol. After extensive condition and organic base screening, curiously, the only organic base found to mediate 2-naphthol carboxylation was TBD. A range of novel ruthenium PN catalysts were designed and tested within ethanol/methanol heterocoupling to isobutanol. In depth analysis of post reaction mixtures revealed previously unknown side products of the Guerbet reaction. Careful analysis of catalyst transformations revealed insights into catalyst activation and degradation. A series of ruthenium phosphinophenoxide pre-catalysts were developed for isobutanol and n-butanol synthesis. One of the pre-catalysts designed was the most productive within the literature for ethanol homocoupling to n-butanol. Ruthenium complex transformations and mechanistic information were found by studying base-free reactions using these novel pre-catalysts. It was proposed quaternary ammonium hydroxides (QOH) could replace alkali metal alkoxides, within the Guerbet reaction, to reduce the amount of solid waste by-products. Studies involved development of QOH synthetic methods and QOH degradation analysis as well as cation, condition and pre-catalyst screening. Across most QOH-containing systems, the post reaction mixtures were homogeneous solutions therefore solid waste was not produced.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Chemistry
Date of First Compliant Deposit:	25 April 2023
Last Modified:	25 Apr 2024 01:30
URI:	https://orca.cardiff.ac.uk/id/eprint/159034

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