The catalytic ortho-arylation of phenols is a reaction that has been developed by our Bedford and coworkers allowing the construction of 2-hydroxybiphenyls from aryl halides and phenols. The biaryl sub-unit is important in the formation of pharmaceutically relevant products, polymers, liquid crystals, and as ligands for homogeneous transition metal catalysts. The scope of this catalytic process has been investigated by extending the technique to tackle a more biologically and pharmaceutically relevant phenol: (L)-tvrosine. The catalysis has proven successful with range of aryl bromides including electron deficient, electron neutral, and sterically hindered species. Cleavage of the tert-butyl protecting group has given rise to successful diarylation. An elegant approach to the ortho-arylation of phenols would avoid the use of a protecting group in the 2- position. We have therefore investigated the use of carbamates as masked phenols. Our results have also shown an unprecedented level of selectivity for mono-arylated product. These results will also be presented In an aim to move away from industrially disfavoured solvents, such as chlorinated DCE, and strong acid solvents, which have poor tolerance of functional groups, solvent-free C-H activation was developed. The methodology was applied to good effect on a range of C-H functionalisation reactions- palladium- catalysed ortho-arylation of carbamates and anilides, copper-mediated meta-arylation of anilides and palladium-catalysed ortho-chlorination of anilides. During this research, it was discovered that bromination was not possible via C-H activation despite claims in the published solution-phase reaction. This final discovery prompted us to investigate mild methods for artha-halogenation, as a result pTSA- mediated artha-halogenation of anilides was developed using a palladium catalyst." During the investigation into potential reactive intermediates an unusual C-H activated pTSA complex was isolated and characterised. This species was also shown to undergo facile reduction to a Pd(I)/(II) tetramer.