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Title: Aspects of organonitrogen and organosulphur chemistry in synthesis and recognition
Author: Rasheed, Omer
ISNI:       0000 0004 6498 0378
Awarding Body: University of Manchester
Current Institution: University of Manchester
Date of Award: 2016
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Further investigations intending illucidate the mechanism of a newly discovered redox-alkylation reaction of azo dyes are presented. Preliminary results indicate that this reaction most probably proceeds via initial N-alkylation of the anion derived from an alpha-ketohydrazone. An investigation is continued to study the synthesis of macrocycle-carbohydrate-dye hybrids. The development of a modular approach to macrocycle assembly has enabled the synthesis of a library of pyridine-based macrocycles possessing multiple donor sites. A central dye scaffold, prepared from the SNAr reaction between halo-substituted azo dye and a disubstituted phenol, was decorated with a representative carbohydrate or macrocycle using Sharpless click chemistry. Also an "S3N-ligand azo-dye" conjugate has been synthesised with a view to the development of a sensor for heavy metal ions. Complexation of this system with Ag(I), Hg(II) and Cu(II) salts has been investigated. Complexation of the dye to metals results in a bathochromic shift in the absorption maximum of the azo dye, an effect which is most pronounced for Cu(II).The Kobayashi fragmentation has transformed the area of benzyne chemistry as it enables its generation from readily available precursors under mild reaction conditions. The controlled generation of benzyne in this manner has been utilised by many groups, allowing readily access to a variety of functionalised aromatic and heteroaromatic from simple precursors. During the course of a synthetic project, which was to utilise the Kobayashi fragmentation in a key intramolecular Diels-Alder reaction, we noticed that alternate modes of fragmentation/rearrangement accompanied the desired elimination reaction leading to benzyne generation. In particular, competing Fries or Smiles rearrangements became the major routes of fragmentation in appropriately functionalised substrates. The results of an investigation into the factors affecting the course of the Kobayashi fragmentation, together with the development of a novel bi-aryl synthesis are presented in this thesis.
Supervisor: Quayle, Peter Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: intramolecular Diels-Alder reaction ; Fries or Smiles rearrangements ; benzyne ; bi-aryl synthesis ; macrocycles ; Kobayashi fragmentation ; macrocycle-carbohydrate-dye hybrids