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Title: Stereochemically Well-Defined Ruthenium (II) TetheredCatalysts for Asymmetric Transfer Hydrogenation
Author: Cheung , Fung Kei
ISNI:       0000 0004 2669 635X
Awarding Body: The University of Warwick
Current Institution: University of Warwick
Date of Award: 2008
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A series of novel ether-linked tethered catalysts were synthesised based on fJ-amino alcohol and monotosylated diamine. This type of catalysts allow modifications of the chiral space in the region of the transition state which lies below the Ru-H bond, without destroying the diastereoselectivity observed for the formation of Ru-Hydride from the 16 electron intermediate. This modification is hoped to increase the sensitivity towards unsymmetrical dialkyl ketone reductions. A 4-methyl analogue of the recently developed reverse tethered catalyst was synthesised where the tether chain is incorporated between the basic amine of the ligand and the 116-arene ring. This catalyst showed decreased reactivity and similar enantioselectivity for a range of simple ketone reductions. However, the reduction of challenging dialkyl ketones such as cyclohexyl methyl ketone gave up to 75 % e.e. Detailed kinetic studies were conducted for a series or'reverse tethered catalysts. Kinetic models were proposed, and rate constants were calculated for each catalyst. Further studies were conducted using the most active complex at various ketone concentration, different ketone substrates and various temperatures.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available