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Title: Chiral amines via asymmetric reduction of imino bonds
Author: Villa Marcos, Bárbara
ISNI:       0000 0004 2733 6946
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2011
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Amines, in particular α-chiral amines, are highly valuable products and key intermediates of great importance in chemical synthesis. Therefore, developing new methods for the synthesis of optically pure amines is an important task in organic chemistry. Chapter 1 presents a general introduction to recent development in the asymmetric reduction of imino bonds, focusing on the metal- catalysed asymmetric hydrogenation of imines. This introduction will be followed by the presentation of several methodologies for the synthesis of amines, with an emphasis on chiral amines. Chapter 2 describes the synthesis of α-chiral amines by direct reductive amination ofketones using H2 as the hydrogen source. The catalyst is formed by the combination of a chiral Ir(III)-diamine complex and a chiral phosphate counteranion. We believe that the catalysis is brought about by the cooperative action of the metal and the counteranion, the former activating H2 whilst the latter ion-pairing with the protonated substrate. Chapter 3 describes the synthesis and characterization of several cyclometallated Ir(III)-imine complexes, and their application to imine hydrogenation. These cyclometallated iridium complexes are highly active for imine hydrogenation. Kinetic studies suggest that the hydrogen coordination to the metal centre is the rate-determining step. Chapter 4 is a natural extension of Chapter 3. Chiral cyclometallated iridium complexes containing a chiral oxazoline ligand were applied to the asymmetric hydrogenation of imines using an N-benzylimine as a model substrate. The catalysts provide enantioselectivity up to 78% ee. Chapter 5 presents the synthesis of ~-chiral amines by a metal- 'and organo- catalysed hydroaminomethylation pathway. Styrene is selectively hydroformylated to the corresponding a-branched aldehyde with a Rh(I) complex, and subsequent reductive amination occurs with Hantzsch ester as the hydrogen source and a chiral phosphoric acid as the organocatalyst. Moderate yields and good enantioselectivities have been obtained.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral