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The synthesis of novel profluorescent nitroxide probes

Keddie, Daniel Joseph (2008) The synthesis of novel profluorescent nitroxide probes. PhD thesis, Queensland University of Technology.

Abstract

A number of novel isoindoline nitroxides have been synthesised using a variety of synthetic techniques. Several carbon-carbon bond forming methodologies, including the first examples of Heck and Sonogashira coupling applied to the isoindoline nitroxide class, were utilised to give novel robust aromatic frameworks. Palladium-catalysed Heck coupling of brominated nitroxides and ester-substituted olefins generates novel nitroxides possessing extended conjugation. Hydrolysis of the nitroxide esters gave the corresponding carboxylic acids, which showed enhanced water solubility. Sonogashira coupling of an iodo-isoindoline nitroxide gave several novel alkynesubstituted nitroxides in high yield. Subsequent coupling of a deprotected ethynyl nitroxide with aromatic iodides gave acetylene-linked nitroxides and an acetylene linked nitroxide dimer. A butadiyne linked dinitroxide was successfully synthesised via Eglinton oxidative coupling of two ethynyl nitroxides. The synthesis of a novel water-soluble dicarboxy nitroxide was achieved by base hydrolysis of a dinitrile. Functional group interconversion furnished anhydride and imide substituted nitroxides from the diacid. Subjecting the imide to the Hofmann rearrangement gave an unexpected brominated amino-carboxy nitroxide. The dicarboxy nitroxide and the brominated amino-carboxy nitroxide were both shown to have a protective effect on Ataxia-Telangiectasia cells, indicating a possible role as antioxidants in the treatment of this disease. A fluorescein nitroxide was successfully synthesised through the condensation of the anhydride substituted nitroxide and resorcinol. After limited success using a variety of other techniques, Buchwald-Hartwig amination was able to furnish a rhodamine nitroxide, via a triflate-fluorescein nitroxide. The extended aromatic nitroxides possess suppressed fluorescence and we have described these systems as profluorescent. The profluorescent nitroxides were found to have significantly lower quantum yields than the non-radical analogues and displayed a substantial increase in fluorescence intensity upon radical trapping, making them useful probes for free radical reactions.

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ID Code: 16702
Item Type: QUT Thesis (PhD)
Supervisor: Bottle, Steven& Arnold, Dennis
Keywords: alkenylation, alkynylation, Buchwald-Hartwig amination, cyanation, fluorescein, fluorescence, fluorophore, free radical, Heck coupling, hydroxylamine, isoindoline, methoxyamine, nitroxide, oxidation, oxoammonium, palladium- catalysis, paramagnetic, profluorescent, reduction, redox, rhodamine, Sonogashira coupling, synthesis, water soluble, xanthene
Divisions: Past > QUT Faculties & Divisions > Faculty of Science and Technology
Past > Schools > School of Physical & Chemical Sciences
Department: Faculty of Science
Institution: Queensland University of Technology
Copyright Owner: Copyright Daniel Joseph Keddie
Deposited On: 03 Dec 2008 14:08
Last Modified: 04 Jun 2012 09:03

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