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Title: Novel iridicycles for the asymmetric reduction of C=N bonds
Author: Smith, Jennifer
ISNI:       0000 0004 6058 1185
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2015
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The asymmetric reduction of imino bonds is a well known and utilised method of chiral amine synthesis. Chapter 1 gives an insight into the published methods for a range of substrates via hydrogenation and transfer hydrogention systems. This thesis presents a range of novel iridicycles, all of which contain chiral oxazoline and imidazoline ligands. The synthesised complexes demonstrate a variety of electronic and steric properties. Their activities are presented in the latter chapters for the asymmetric reduction of C=N bonds. Chapter 3 demonstrates the activity of the 4,5,6-trimethoxyimidazoline iridium complex for direct asymmetric reductive amination. High activity, yielding up to quantitative product is reported, under unusually mild conditions, in both aqueous and organic solvent systems. The enantioselectivites achieved were moderate to high for the substrates screened. The use of a bulky 2,4,6-tri-iso-propyloxazoline iridium complex is reported for the asymmetric reduction of quinolines, via transfer hydrogenation conditions. The tetrahydroquinolines were produced in high yields and moderate enantioselectivities. The addition of co-solvents to the aqueous system yielded improved enantioselectivies and conversions. For the reduction of pyridinium salts a bromo-dioxole imidazoline iridium complex presented high activity. This presents unprecedentedly mild conditions via a transfer hydrogenation system, producing high yields of N-benzyl piperidines. The enantioselectivites determined were high, although some could not be measured by the available means. The 2,4,6-tri-iso-propyloxazoline iridium complex further demonstrates high activity and enantioselectivity for the asymmetric hydrogenation of acyclic imines. An NMR and mechanistic study revealed the in-situ formation of a new iridium species present only in TFE.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QD Chemistry