Dunbabin, Alice; (2018) Integrated heterogeneous catalysis and biocatalysis for sustainable synthesis. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

The development of sustainable methods with applications in synthetic organic chemistry has been investigated widely in recent years. Catalytic processes often provide sustainable strategies with high efficiency, high selectivity and low environmental impact in terms of energy consumption and waste production. In this project, heterogeneous catalysis and biocatalysis have been investigated separately and combined into a two-step process. Gold nanoparticle catalysts supported on inert bulk materials have been applied in the oxidation of alcohol feedstocks as an alternative to stoichiometric oxidation techniques. Synthesis of a range of gold nanoparticle catalysts has been undertaken with variation in support materials and preparation methods. These catalysts have been tested in the oxidation of the benchmark substrate benzyl alcohol, and the substrate scope also extended to include secondary alcohols. The low gold loading and reusability of these heterogeneous catalysts coupled with the use of water as the solvent has provided a sustainable oxidation method for primary and secondary alcohols. Transaminases are enzymes which catalyse the transfer of an amino group to the carbonyl group of an aldehyde or ketone. Screening of transaminases from the UCL transaminase library was undertaken to identify enzymes for application in this project. These enzymes have been applied in the synthesis of furfurylamines from furfurals, in a one-step biocatalytic reaction under mild conditions on a preparative scale. The transaminases were also applied in the synthesis of chiral amines from ketone precursors, with high yields and stereoselectivities achieved. Heterogeneous catalysis and biocatalysis have been coupled together into a novel two-step cascade to produce chiral amines from secondary alcohol feedstocks. The oxidation of secondary alcohols using gold nanoparticle catalysts was followed by the transamination of the ketone intermediates. This process was conducted in one pot, with water as the solvent and no isolation or purification of the ketone intermediate.

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