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Title: Applications of tethered asymmetric hydrogenation catalysts
Author: Hall, Thomas Howard
ISNI:       0000 0004 7431 6892
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 2017
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Attempts have been made to prepare new polymer supported and maleimide functionalised ruthenium catalysts for asymmetric transfer hydrogenation. Synthetic approaches were found to be challenging but did lead to the development of a series of complexes containing the para-Iodobenzenesulfonyl group, which may potentially serve as a handle for future functionalisation. The arene exchange route to tethered complexes as previously published by Wills et al. has been refined in an attempt to improve reliability. The practical challenges of carrying out the reaction and especially purifying the resulting complexes are discussed and the use of molecular sieves as a trap for free hydrogen chloride gas is recommended. Known tethered complexes reported by Wills have been applied to the reduction of electron rich ketones, containing oxygen or nitrogen substituents on their aromatic rings. Such ketones are relatively unreactive and require higher temperatures and extended reaction times, however in most cases the chiral alcohols could still be obtained with good yield and enantioselectivity. The choice of solvent/hydrogen donor is shown to be important and substrate dependant. Finally, reduction of β-chloropropiophenone to the dehalogenated chiral alcohol prompted an investigation into the reductions of enones with tethered catalysts. Selectivity between 1,4- and 1,2- reduction products is shown to be strongly substrate dependant but can also be influenced by the choice of catalyst, with the recently developed methoxy tethered catalyst demonstrating an increased preference for 1,4- reduction in all cases.
Supervisor: Not available Sponsor: Engineering and Physical Sciences Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QD Chemistry