Retro-Diels-Alder routes to 4,5 disubstituted cyclopentenones

 

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dc.contributor.advisor Sickle, Eugene S en_ZA
dc.contributor.advisor Hunter, Roger en_ZA
dc.contributor.author Kidane, Aklilu Asefaw en_ZA
dc.date.accessioned 2014-10-21T06:53:20Z
dc.date.available 2014-10-21T06:53:20Z
dc.date.issued 2005 en_ZA
dc.identifier.citation Kidane, A. 2005. Retro-Diels-Alder routes to 4,5 disubstituted cyclopentenones. University of Cape Town. en_ZA
dc.identifier.uri http://hdl.handle.net/11427/8660
dc.description Includes bibliographical references ( leaves 78-81) en_ZA
dc.description.abstract Investigation into the synthesis of 4,5-disubstituted cyclopentenones was conducted in light of recent interest on cyclopentenone prostaglandins (PGs) as a new class of anti-viral and anti-inflammatory agents. The strategy involved conjugate addition of various organocuprates to tricyclodecadienone derived from dicyclopentadiene and gave 5-exo-substituted tricyclodecadienones. Attempts to alkylate the kinetic lithium, copper and quaternary ammonium enolates generated from 5-exo-substituted tricyclodecadienones with alkylhalides were unsuccessful. Even in the presence of strong cation solvating hexamethylphosphoramide (HMPA) (±30% co-solvent), lithium enolates proved inert. However, trapping the magnesium enolate generated from the 1, 4-addition of n-butylmagnesium bromide to tricyclodecadienone with aldehydes yielded β-ketols of syn and anti-relative configuration. Due to their labile nature, the β-ketols were dehydrated to their corresponding stable enones. Achiral retro-Diets-Alder reactions were first attempted on 5-exo-substituted tricyclodecadienones using several Lewis-acid catalysts. 4-Substituted-2 cyclopentenones were isolated in good yield and no double bond rearrangement or decomposition was observed. Similar results were also obtained with the dienones generated from dehydration of β-ketols to give αα',ββ'-unsaturated cyclopentadienones in good yield. The synthesis of enantiomerically pure 4- Substituted cyclopentenones and 4- butyl-5-butylidene-cyclopent-2-enone via chiral Lewis-acid catalysed asymmetric retro-Diets-Alder reactions were unsuccessful. Chiral Lewis-acids were prepared in situ from selected Lewis-acids and chiral ligands containing the diol functionality namely BINOL and the TADDOLs. en_ZA
dc.language.iso eng en_ZA
dc.subject.other Chemistry en_ZA
dc.title Retro-Diels-Alder routes to 4,5 disubstituted cyclopentenones en_ZA
dc.type Thesis / Dissertation en_ZA
uct.type.publication Research en_ZA
uct.type.resource Thesis en_ZA
dc.publisher.institution University of Cape Town
dc.publisher.faculty Faculty of Science en_ZA
dc.publisher.department Department of Chemistry en_ZA
dc.type.qualificationlevel Masters en_ZA
dc.type.qualificationname MSc en_ZA
uct.type.filetype Text
uct.type.filetype Image


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