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Title: Linear allylic halides in metal-catalysed asymmetric substitutions
Author: Mistry, Nisha
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2018
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This thesis describes the use of linear allylic halides in transition metal catalysed asymmetric reactions. In the first chapter we report the development of a copper-catalysed hetero-asymmetric allylic alkylation reaction of ester-containing allylic bromides. Despite the synthesis of a number of phosphoramidite ligands based on a bis-phenol backbone, we achieve only a 44% yield and 73% ee in this challenging reaction. Application of our reaction conditions to other linear allylic halides that do not bear the ester group resulted in only moderate results. In the second chapter we describe new phosphoramidite ligands based on (S,S)-trans-cyclohexanediol and (R,R)-(+)-1,2-diphenyl-1,2-ethanediol. The ligands were examined in 3 different copper-catalysed asymmetric reactions and enantioselectivity of up to 89% ee was observed. Using the meso-diols with a chiral non-racemic amine gave diastereomeric ligands bearing achirotopic stereogenic phosphorus atoms, which were characterised with the assistance of X-ray crystallography and VT NMR studies. In the last chapter we discuss the development of a rhodium-catalysed asymmetric carboxylation of ester-containing allylic bromides to form stereogenic carbon centres bearing two different carboxylates. The method uses common carboxylic acids as nucleophiles to form new C-O bonds in high yields and excellent enantioselectivities. We also demonstrate that the products can be used to form other chiral acetal derivatives, including valuable γ butenolides, in subsequent RCM reactions. The ease of synthesis and stability of the products suggests that a broad range of new chemical species may be accessible by developing strategies to form stereogenic carbon centres featuring different combinations of multiple heteroatoms. We have begun to demonstrate this by using this method for the formation of O,N-aminals.
Supervisor: Fletcher, Stephen P. Sponsor: Engineering and Physical Sciences Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Chemistry, Organic