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Title: Transition metal oxazoline complexes : synthesis and applications in asymmetric catalysis
Author: Garratt, Shaun Anthony
Awarding Body: University of Leicester
Current Institution: University of Leicester
Date of Award: 1998
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This thesis describes the synthesis and chemistry of "(arene)Ru" and "Cp*Rh" complexes of chiral oxazoline-containing ligands and their use as asymmetric Lewis-acid catalysts. Chapter One introduces important aspects of asymmetric catalysis, then describes in more detail the use of chiral oxazoline ligands to induce high levels of stereocontrol in many important catalytic reactions. Chapter Two initially introduces the area of chiral half-sandwich complexes, describing their chemistry and their use in asymmetric synthesis. The synthesis and characterisation of half-sandwich ruthenium and rhodium complexes of C2-symmetric bis-oxazoline ligands is then described (these complexes are chiral at ligand only). The complex solution behaviour of the aqua species [M(OH2)(N-N)(ring)]2+ was extensively investigated. In the latter part of the chapter, the synthesis of half-sandwich complexes of unsymmetrical oxazoline ligands is described. In this case, the complexes are chiral-at-metal and the relative diastereoselectivities of formation and configurational stabilities in solution are discussed in detail and were generally found to be very high. Numerous X-ray structures have been obtained and variable temperature and 2D NMR techniques have been employed to study the solution behaviour of the complexes. Chapter Three describes the use of the half-sandwich complexes as asymmetric Lewis-acid catalysts. Complexes [Ru(OH2)(N-N)(mes)](SbF6)2 (N-N = pymox, benbox) were found to be efficient and enantioselective catalysts for the Diels-Alder reaction of acrylic dienophiles with simple dienes. A selection of different catalysts and substrates were used, with varying results. Other Lewis-acid catalysed reactions (including the Hetero-Diels Alder and Mukaiyama Aldol) were studied, but with less success. The inverse electron-demand Hetero Diels-Alder reaction was identified as an area worthy of further study.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available