Synthetic and mechanistic aspects of the reactions of α-diazosulfoxides

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dc.contributor.advisor Maguire, Anita R. O'Sullivan, Orlagh C. M. 2012-11-26T17:43:54Z 2012-11-26T17:43:54Z 2008-11 2009
dc.identifier.citation O'Sullivan, O. C. M. 2009. Synthetic and mechanistic aspects of the reactions of α-diazosulfoxides. PhD Thesis, University College Cork. en
dc.description.abstract The research described in this thesis focuses, principally, on synthesis of stable α-diazosulfoxides and investigation of their reactivity under various reaction conditions (transition-metal catalysed, photochemical, thermal and microwave) with a particular emphasis on the reactive intermediates and mechanistic aspects of the reaction pathways involved. In agreement with previous studies carried out on these compounds, the key reaction pathway of α-diazosulfoxides was found to be hetero-Wolff rearrangement to give α-oxosulfine intermediates. However, a competing reaction pathway involving oxygen migration from sulfur to oxygen was also observed. Critically, isomerisation of α-oxosulfine stereoisomers was observed directly by 1H NMR spectroscopy in this work and this observation accounts for the stereochemical outcomes of the various cycloaddition reactions, whether carried out with in situ trapping or with preformed solutions of sulfines. Furthermore, matrix isolation experiments have shown that electrocyclisation of α-oxosulfines to oxathiiranes takes place and this verifies the proposed mechanisms for enol and disulfide formation. The introductory chapter includes a brief literature review of the synthesis and reactivity of α-diazosulfoxides prior to the commencement of research in this field by the Maguire group. The Wolff rearrangement is also discussed and the characteristic reactions of a number of reactive intermediates (sulfines, sulfenes and oxathiiranes) are outlined. The use of microwave-assisted organic synthesis is also examined, specifically, in the context of α-diazocarbonyl compounds as substrates. The second chapter describes the synthesis of stable monocyclic and bicyclic lactone derivatives of α-diazosulfoxides from sulfide precursors according to established experimental procedures. Approaches to precursors of ketone and sulfimide derivatives of α-diazosulfoxides are also described. The third chapter examines the reactivity of α-diazosulfoxides under thermal, microwave, rhodium(II)-catalysed and photochemical conditions. Comparison of the results obtained under thermal and microwave conditions indicates that there was no evidence for any effect, other than thermal, induced by microwave irradiation. The results of catalyst studies involving several rhodium(II) carboxylate and rhodium(II) carboxamidate catalysts are outlined. Under photochemical conditions, sulfur extrusion is a significant reaction pathway while under thermal or transition metal catalysed conditions, oxygen extrusion is observed. One of the most important observations in this work was the direct spectroscopic observation (by 1H NMR) of interconversion of the E and Z-oxosulfines. Trapping of the α-oxosulfine intermediates as cycloadducts by reaction with 2,3-dimethyl-1,3-butadiene proved useful both synthetically and mechanistically. As the stereochemistry of the α-oxosulfine is retained in the cycloadducts, this provided an ideal method for characterisation of this key feature. In the case of one α-oxosulfine, a novel [2+2] cycloaddition was observed. Preliminary experiments to investigate the reactivity of an α-diazosulfone under rhodium(II) catalysis and microwave irradiation are also described. The fourth chapter describes matrix isolation experiments which were carried out in Rühr Universität, Bochum in collaboration with Prof. Wolfram Sander. These experiments provide direct spectroscopic evidence of an α-oxosulfine intermediate formed by hetero-Wolff rearrangement of an α-diazosulfoxide and subsequent cyclisation of the sulfine to an oxathiirane was also observed. Furthermore, it was possible to identify which stereoisomer of the α-oxosulfine was present in the matrix. A preliminary laser flash photolysis experiment is also discussed. The experimental details, including all spectral and analytical data, are reported at the end of each chapter. The structural interpretation of 1H NMR spectra of the cycloadducts, described in Chapter 3, is discussed in Appendix I. en
dc.format.mimetype application/pdf en
dc.language.iso en en
dc.publisher University College Cork en
dc.rights © 2009, Orlagh C. M. O'Sullivan en
dc.rights.uri en
dc.subject Alpha-diazosulfoxides en
dc.subject Synthesis of alpha-diazosulfoxides en
dc.subject Reactivity of alpha-diazosulfoxides en
dc.subject Matrix isolation studies en
dc.subject.lcsh Chemistry, Analytic en
dc.title Synthetic and mechanistic aspects of the reactions of α-diazosulfoxides en
dc.type Doctoral thesis en
dc.type.qualificationlevel Doctoral en
dc.type.qualificationname PhD (Science) en
dc.internal.availability Full text not available en
dc.description.version Accepted Version en
dc.contributor.funder Enterprise Ireland en
dc.contributor.funder Eli Lilly and Company, United States en
dc.description.status Not peer reviewed en Chemistry en

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© 2009, Orlagh C. M. O'Sullivan Except where otherwise noted, this item's license is described as © 2009, Orlagh C. M. O'Sullivan
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