Gold-Mediated C–H Functionalisation

Abstract

The transition metal–catalysed direct functionalisation of C–H bonds is an increasingly viable alternative to the multi–step strategies traditionally employed. The use of powerful and environmentally benign gold species in such transformations has highlighted their remarkable reactivity and led to a significant increase in their utilisation. This thesis provides an overview of our efforts to contribute to the rapidly expanding area of gold–catalysed C–H functionalisation. The introductory chapter will review existing methodologies, looking at transformations which rely on the ability of gold to perform C–H activation, as well as those exploiting its potent π-acidity. The development of a gold(I) C–H activation of electron-deficient arenes will be described. Proceeding under very mild reaction conditions, the corresponding aryl gold(I) species are generated in excellent yields. The auration is highly regioselective, invariably activating the position with two ortho- electronwithdrawing groups. Our efforts to perform this auration in the absence of a silver source will then be discussed. The unwavering fidelity of gold(I) to activation of electron-deficient arenes is counter to the established preference of gold(III) towards the activation of electron-rich arenes. We sought to exploit these contrasting modes of reactivity in the development of an oxidative gold(I)/gold(III) cross-coupling process. The scope and mechanism of this process will be discussed. An alternative method of generating aryl gold(I) species, relying on the capability of gold(I) to perform the decarboxylative activation of a number of benzoic acids, allowed us access to a wider substrate scope for the oxidative cross-coupling, than the C–H activation alone. This expansion of the scope will also be discussed in this final chapter.