The Application and Evolution of Chiral Ion-Paired Rhodium(II,II) Tetracarboxylate Catalysts for Enantioselective Nitrene Transfer

Abstract

This thesis describes the investigations into enantioselective nitrene transfer chemistry employing chiral ion-paired dirhodium catalysts. The initial development of this catalyst family was reported previously by the Phipps group and their design is based on a strategy for the combination of transition metal complexes and cinchona alkaloid-derived chiral cations. In the first section of research, an enantioselective aziridination of alkenyl alcohols using these catalysts is presented, which was conducted in collaboration with Dr. Alexander Fanourakis and Arthur R. Lit. This methodology displayed high enantioselectivities for a wide scope of substrates, covering alkene substitution patterns, lengths of the alcohol chain and aromatic substitution. The second section details the design and synthesis of next generation chiral catalysts. This work was driven by the hypothesis that alteration of the rhodium dimer structure, namely the location of the peripheral anionic group which engages in a chiral ion-pair, would enable improved metrics for highly valuable amino-alcohol products. The final section realises this hypothesis and demonstrates the highly enantioselective C−H amination of hydrocinnamyl alcohols and the aziridination of allylic alcohols for the first time, in collaboration with Dr. Shotaro Takano and Dr. Alexander Fanourakis. Control over additional aspects including site-selectivity, chemoselectivity and diastereoselectivity were also shown. As a whole, the research described in this thesis aims to expand the scope of enantioselective nitrene transfer and demonstrate the power of a chiral ion-pairing strategy utilising chiral cations.