Transition metal catalysed trifluoromethylation using trifluoromethyl iodide
Described herein are a variety of experimental and computational data obtained in the exploration and optimisation of a novel trifluoromethylation reaction. This involved the palladium catalysed Suzuki cross-coupling of trifluoromethyl iodide with boronic acids to yield trifluoromethylated products. Initial efforts focused on the optimisation of reaction conditions, however, despite extensive screening, poor yields were invariably encountered. Additionally, these early experiments revealed the formation of unexpected catalyst decomposition products, as well the extensive trifluoromethylation of solvent C-H bonds. Subsequent computational analysis provided insight into the formation of various catalytic intermediates and potential decomposition pathways, and ultimately suggested catalyst decomposition was occurring via solvent C-H activation. Based on this finding, the circumvention of catalyst decomposition and unwanted side-reactivity through the use of perfluorinated solvents was trialled. While this largely eliminated unwanted reactivity, the desired Suzuki cross-coupling reaction remained sluggish. This represented an area of improvement for future work. With this considered, the striking activity of this catalyst system towards C-H bonds was also acknowledged as valuable. As such, the directing group assisted trifluoromethylation of various substrates through C-H activation was also examined. Finally, this system was extended to nickel catalysts, providing a unique and mechanistically insightful example of a nickel catalysed trifluoromethylation.