New Catalysts for Asymmetric Nitrene Transfer Based on Ion-Pairing Between Sulfonated Rhodium(II,II) Tetracarboxylates and Chiral Cations: Design, Synthesis and Applications to Enantioselective Carbon-Nitrogen Bond Formation – Alexander Fanourakis

The work presented in this thesis investigates a new strategy for the catalytic, asymmetric synthesis of C(sp3)–N bonds and is divided into three parts.

First, the design and synthesis of a novel class of chiral rhodium(II,II) tetracarboxylate dimer is presented. Inspired by a design strategy previously developed within the Phipps research group for bipyridine ligands, di-sulfonated variants of the Rh2(esp)2 dimer are ion-paired with two chiral cations based on quaternised cinchona alkaloids. The modular catalyst design is used to construct a large library with the aim of exerting catalyst-control over selectivity in the ensuing nitrene-transfer reactions. In the second part, proof of concept using these dimers is achieved in a challenging intermolecular enantioselective benzylic C(sp3)–H amination which was developed working with Dr Benjamin D. Williams and Kieran J. Paterson. A range of aryl alcohols are efficiently aminated with up to 93% ee and this study highlights the importance of substrate-direction by the terminal alcohol group and lays the foundation for the next stage. The final part of this thesis describes a more general reaction mediated by these catalysts: an asymmetric aziridination of alkenyl alcohols. This substrate-directed transformation was developed with Nicholas J. Hodson and Arthur R. Lit and is broad across alkene substitutions with an empirical mnemonic developed to predict substrate performance. It is hoped that this second reaction will constitute a small step in advancing asymmetric aziridination to the same level of utility as the current asymmetric epoxidation protocols.