An Investigation into the Application and Mechanisms of Manganese(I) in C–H Functionalisation and Organic Synthesis

This thesis explores through mechanistic investigation the underlying activation and relevant species involved in the manganese(I)-mediated functionalisation of small organic molecules. Supplementary focus was applied to probing the versatility of the discussed chemistry towards organic synthesis where appropriate. To explore the suitable applications of manganese(I), this thesis is divided into appropriate subsections focusing on reactions of the same classes of small molecules, namely aryl/heteroaryl diazonium salts, and 3- or 4-(2- pyridyl)coumarins. Chapter II of this thesis offers an exploratory and mechanistic driven approach at applying earth-abundant manganese towards a previously commonly applied precious metal-catalysed borylation methodology. The scope, controls and mechanistic experiments are rigorously investigated to ascertain the identity of the active Mn(I)-species encountered in the reaction. Chapter III and IV offer an investigation into the C–H activation and functionalisation of 3- and 4-N–directed coumarin derivatives under stoichiometric regimes, based upon substrate applied. The exploration is divided with Chapter III exploring the initial activation step of the coumarin derivatives including their photophysical and photochemical activation. Chapter IV then exploits the discoveries made in Chapter III and applies the C–H activation towards functionalisation with suitable alkyne coupling partners. The reactions and novel products are spectroscopically explored again, and are then further modified to isolate useful derivatives removing the anion used as the spectroscopic handle exploited in Chapter III and previous. Chapter V then offers an insight towards the future of coumarin C–H functionalisation, with tentative probing and first optimisations towards catalytic C–H transformations on the heterocyclic framework. This work again exploits the earth-abundant transition metal manganese, revealing the delicate interplay demonstrated by the structural connectivity of the (2-pyridyl)coumarin and the site of C–H functionalisation.