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

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dc.contributor.advisorSickle, Eugene Sen_ZA
dc.contributor.advisorHunter, Rogeren_ZA
dc.contributor.authorKidane, Aklilu Asefawen_ZA
dc.date.accessioned2014-10-21T06:53:20Z
dc.date.available2014-10-21T06:53:20Z
dc.date.issued2005en_ZA
dc.descriptionIncludes bibliographical references ( leaves 78-81)en_ZA
dc.description.abstractInvestigation 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.identifier.apacitationKidane, A. A. (2005). <i>Retro-Diels-Alder routes to 4,5 disubstituted cyclopentenones</i>. (Thesis). University of Cape Town ,Faculty of Science ,Department of Chemistry. Retrieved from http://hdl.handle.net/11427/8660en_ZA
dc.identifier.chicagocitationKidane, Aklilu Asefaw. <i>"Retro-Diels-Alder routes to 4,5 disubstituted cyclopentenones."</i> Thesis., University of Cape Town ,Faculty of Science ,Department of Chemistry, 2005. http://hdl.handle.net/11427/8660en_ZA
dc.identifier.citationKidane, A. 2005. Retro-Diels-Alder routes to 4,5 disubstituted cyclopentenones. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Kidane, Aklilu Asefaw AB - 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. DA - 2005 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 2005 T1 - Retro-Diels-Alder routes to 4,5 disubstituted cyclopentenones TI - Retro-Diels-Alder routes to 4,5 disubstituted cyclopentenones UR - http://hdl.handle.net/11427/8660 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/8660
dc.identifier.vancouvercitationKidane AA. Retro-Diels-Alder routes to 4,5 disubstituted cyclopentenones. [Thesis]. University of Cape Town ,Faculty of Science ,Department of Chemistry, 2005 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/8660en_ZA
dc.language.isoengen_ZA
dc.publisher.departmentDepartment of Chemistryen_ZA
dc.publisher.facultyFaculty of Scienceen_ZA
dc.publisher.institutionUniversity of Cape Town
dc.subject.otherChemistryen_ZA
dc.titleRetro-Diels-Alder routes to 4,5 disubstituted cyclopentenonesen_ZA
dc.typeMaster Thesis
dc.type.qualificationlevelMasters
dc.type.qualificationnameMScen_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceThesisen_ZA
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