Catalytic transformations enabled by dual nickel-photoredox manifolds

Identifier:  TDX:4158

Handle: https://hdl.handle.net/20.500.11797/TDX4158

Authors:  Higginson, Bradley

Abstract:
It has opened numerous pathways to access previously difficult transformations, whilst offering a greener synthetic approach to long-standing challenges. Carbon-Hydrogen functionalisation is a highly sought-after transformation and is an area which photoredox catalysis has had a profound impact upon. To this end, this thesis will focus on the development of nickel-photoredox platforms for the construction of C-C bonds from inert C(sp3)-H bonds. The functionalisation of C(sp3)-H bonds is a very challenging transformation due to the high thermodynamic stability of the C-H bond. Additionally, the ubiquitous nature of the C-H bond means that site selectivity issues can occur. However, by exploiting the thermodynamic and kinetic parameters of hydrogen atom transfer (HAT) selectivity can be realized and specific C-H bonds functionalised from an array of potential sites. Combination of C-H functionalisation with metal catalysis is an incredibly versatile platform and is exploited within this thesis. Additionally, a method for the hydrodehalogenation of arylbromides under visible light irradiation is developed. The reaction exploits the highly reactive nature of excited state species to use THF, a benign solvent, as the hydrogen source. The work is then applied to the hydrodehalogenation of polybrominated diphenyl ethers, a class of persistent organic pollutants that have been banned by the Stockholm convention due to their problematic nature.