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1,3-dipolar cycloaddition reactions in aqueous media and investigations into solid phase ether synthesis

Bala, Kason; (2003) 1,3-dipolar cycloaddition reactions in aqueous media and investigations into solid phase ether synthesis. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Abstract

The first aim of this project was to explore the feasibility of using water as a solvent for azomethine ylide and nitrile oxide 1,3-dipolar cycloaddition reactions and to synthesise heterocycles incorporating masked functionalities. The second theme of the project investigated the synthesis of oxetanes and pentaerythritol oligomers for applications within the explosives industry. The first chapter describes the use of aqueous media for cycloaddition reactions. The use of azomethine ylides and nitrile oxides as 1,3-dipoles in organic and aqueous media are also discussed. The second chapter reviews current synthetic methods and applications of oxetanes as polymeric binders with a brief overview of the use of solid phase supports in organic synthesis. The results and discussion is presented in chapters three to six. Azomethine ylide 1,3-dipolar cycloadditions in aqueous media were investigated and are discussed in chapter three. Contrary to a previous report, exclusive endo diastereoselectivity was observed in water for reactions between maleimides and ylides generated from acyclic α-amino esters. This was attributed to enforced hydrophobic interactions between the reactants. In contrast, cyclic α-amino esters favoured Michael addition in water alone with yield enhancements in biphasic media suggesting that this reaction was catalysed at the solvent interface. Investigations into intermolecular and intramolecular nitrile oxide 1,3-dipolar cycloadditions in aqueous media are discussed in chapters four and five. The first successful generation and subsequent reaction of nitrile oxides has been achieved using sodium hypochlorite in water alone. A wide variety of isoxazolines were synthesised using hydrophobic/hydrophilic substrates and in many cases the use of volatile organic solvents was eliminated. In chapter six, the results of our investigations into oxetane synthesis are described. The primary objective of synthesising a bis-hydroxyl-protected oxetane was achieved using solid support in high yield. Furthermore, the results of our investigations into the synthesis of pentaerythritol oligomers are presented. The final chapter describes the experimental methods employed.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: 1,3-dipolar cycloaddition reactions in aqueous media and investigations into solid phase ether synthesis
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
Keywords: Pure sciences; Cycloadditions
URI: https://discovery.ucl.ac.uk/id/eprint/10104524
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