Synthesis of planar chiral rhodium(II) paddlewheel catalysts : a thesis presented in partial fulfillment of the requirements for the degree of Master of Science in Chemistry at Massey University, Manawatū, New Zealand

Abstract

Catalysts are the most efficient tools for the construction of large complex molecules. They offer an unparalleled way to solve problems and new ways to build molecules. Site-selective catalysts control the site of reaction in molecules that contain multiple sites with similar reactivity. C-H groups are the most abundant sites in all organic molecules but are very unreactive and difficult to functionalise. C-H functionalisation catalysis aims to install functionality at these sites by replacing the C-H bond with a C-C, C-O, C-N or C-X bond. Controlling the selectivity of these reactions is extremely difficult but highly rewarding, as it allows complex molecules to be made from very simple starting materials. Rh(II) paddlewheels are a class of selective C-H functionalisation catalysts that are capable of highly site-selective and enantioselective transformations. The organic ligands of the complex create different shapes around the catalyst active site that force a single C-H site to be targeted. This project aimed to synthesise a new class of Rh(II) paddlewheel catalysts that possess a planar chiral ligand and to investigate their activity and selectivity in C-H insertion reactions. In this work a novel resolution route for dibromide [2.2]paracyclophane carboxylic acids was developed. The carboxylic acids ligands were then used to synthesise three Rh(II) catalysts. Two of these paddlewheels were used to develop a late-stage catalyst functionalisation method through Suzuki-Miyaura coupling. In total, five Rh(II) catalysts were synthesised, of which four were assessed in both intermolecular and intramolecular nitrene insertion reactions.