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Title: Synthesis of novel asymmetric imidazolinium libraries and applications in asymmetric catalysis
Author: Latham, Christopher Michael
ISNI:       0000 0004 6351 9467
Awarding Body: University of Nottingham
Current Institution: University of Nottingham
Date of Award: 2014
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This thesis is comprised of six chapters describing imidazolinium and imidazolium salts and their conversion into nitrogen heterocyclic carbenes (NHCs) for use in asymmetric catalysis. It is structured thus: Chapter one provides an introduction to imidazolium and imidazolinium salts, their discovery and uses; an introduction to carbenes and NHCs, discovery and utilisation with an emphasis on those NHCs derived from imidazolinium salts. Additionally, retro synthetic approaches to NHCs, imidazolium and imidazolinium salts are overviewed. Chapter two describes the synthesis of imidazolinium salts bearing pendant sulfonate groups starting with N-Boc protected chiral aminoalcohols. Oxazolines are formed in situ from the aminoalcohols by action of 2-sulfobenzoic anhydride in a Dean-Stark apparatus. Various amines are then used to open the oxazolines resulting in amidosulfonic acids. These amidosulfonic acids are formed as a result of acid› triggered SN2 attack of the amines at the electrophilic OCH2 site in the oxazoline. The amido group can be reduced with borane-dimethylsulfide, resulting in diamino sulfonic acids which were cyclised with a suitable orthoester, such as triethyl orthoformate, to provide the imidazolinium sulfonate zwitterions. Chapter three details the synthesis of various imidazolinium salts by N-alkylation of imidazolines. Amidosulfonic acids (see Chapter two) are converted into imidazolines by a serendipitous cyclisation that has advantages over other current literature routes. Alkylation of imidazolines with different benzylic halides and bromo alcohols allows a large library of imidazolinium salt to be achieved. Chapter four gives a brief outline of current literature uses of imidazolinium salts in asymmetric catalysis before detailing the synthesis of NHCs complexes and screening of the imidazolinium sulfonate zwitterions (see Chapter two) in catalysis. Specifically additions of alkyl magnesium halides to cinnamyl halide derivates were found to give mostly y-addition products that were enantiomerically emiched (up to 80% ee). The synthesis of copper-carbene-ligands complexes for catalysis of this and other reactions was also investigated. Chapter five provides overall conclusions from this thesis and future work to be carried out. Chapter six contains full experimental details and analytical data for novel compounds prepared. An index of the novel compounds and selected spectra can be found in the appendix.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available