New Strategies for Synthesis with Boronate Esters

Aryl and alkyl boronic acids and their derivatives have a broad variety of applications, ranging from uses in medicines to cross-coupling partners in modern organic synthesis. This thesis presents the work undertaken in both the synthetic and application aspects of this important class of synthetic intermediates. Chapter 1 gives a brief overview on the bonding and physical properties of boronic acids, their synthesis and applications. Chapter 2 shows that the activation of C-H bonds in the iridium-catalysed borylation of arenes is contingent on C-H acidity in the absence of steric effects, allowing for the prediction of regiochemistry through a simple 1H NMR analysis of the starting material. Chapter 3 shows that the high electronic barrier hindering the borylation of C-H bonds alpha to a pyridyl nitrogen can be overcome through steric effects, and that the resultant α-pyridyl boronate can be used, in-situ, in Suzuki-Miyaura cross-coupling reactions. Chapter 4 describes the development of C-H borylation/1,4-conjugate addition sequence, for the synthesis of β-aryl ketones and the corresponding alcohols under reducing conditions. Chapter 5 describes the development of a new methodology for the preparation of alkyl boronate esters through copper-catalysed borylation of alkyl halides.