Some benzo- and naphtopyrans by novel cyclisations

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dc.contributor.advisorGiles, Robin G Fen_ZA
dc.contributor.authorPestana, José Alexandre Xavieren_ZA
dc.date.accessioned2016-03-09T09:07:51Z
dc.date.available2016-03-09T09:07:51Z
dc.date.issued1985en_ZA
dc.descriptionBibliography: pages 150-156.en_ZA
dc.description.abstractIt has recently been shown that the naphthalene dimethyl ethers E-2-Hydroxymethyl-1,4-dimethoxy-3-pent-1-enylnaphthalene and E-2-Hydroxyethyl-1, 4-dimethoxy-3-prop-1-enylnaphthalene cyclise to afford naphtho[2,3-c]pyrans when treated with two molar equivalents of cerium(IV) ammonium nitrate. It has also been shown that these naphthalenes cyclise readily and in high yield to give naphthopyrans when treated with potassium-t-butoxide in dimethylformamide under anaerobic conditions. In order to determine which structural features present in these compounds are required for each mode of cyclisation, a series of ortho-alkenylbenzyl and -naphthyl alcohols, unsubstituted or carrying methoxy or ethyl substituents at appropriate positions on the aromatic ring have been synthesized. The investigations which were carried out revealed that as far as the cerium(IV) ammonium nitrate reactions were concerned, a methoxy group ortho to the alkenyl side chain appeared to be imperative for the success of the reaction. A mechanism for the reaction is proposed. Although no conclusive general mechanism could be inferred from the results obtained from the base-promoted cyclisations, the explanation for this unusual reaction may involve steric effects, since it was those alcohols in which both the hydroxyalkyl and alkenyl side chains were flanked by bulky groups (forcing the reacting centres into close proximity) which cyclised in high yield.en_ZA
dc.identifier.apacitationPestana, J. A. X. (1985). <i>Some benzo- and naphtopyrans by novel cyclisations</i>. (Thesis). University of Cape Town ,Faculty of Science ,Department of Chemistry. Retrieved from http://hdl.handle.net/11427/17607en_ZA
dc.identifier.chicagocitationPestana, José Alexandre Xavier. <i>"Some benzo- and naphtopyrans by novel cyclisations."</i> Thesis., University of Cape Town ,Faculty of Science ,Department of Chemistry, 1985. http://hdl.handle.net/11427/17607en_ZA
dc.identifier.citationPestana, J. 1985. Some benzo- and naphtopyrans by novel cyclisations. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Pestana, José Alexandre Xavier AB - It has recently been shown that the naphthalene dimethyl ethers E-2-Hydroxymethyl-1,4-dimethoxy-3-pent-1-enylnaphthalene and E-2-Hydroxyethyl-1, 4-dimethoxy-3-prop-1-enylnaphthalene cyclise to afford naphtho[2,3-c]pyrans when treated with two molar equivalents of cerium(IV) ammonium nitrate. It has also been shown that these naphthalenes cyclise readily and in high yield to give naphthopyrans when treated with potassium-t-butoxide in dimethylformamide under anaerobic conditions. In order to determine which structural features present in these compounds are required for each mode of cyclisation, a series of ortho-alkenylbenzyl and -naphthyl alcohols, unsubstituted or carrying methoxy or ethyl substituents at appropriate positions on the aromatic ring have been synthesized. The investigations which were carried out revealed that as far as the cerium(IV) ammonium nitrate reactions were concerned, a methoxy group ortho to the alkenyl side chain appeared to be imperative for the success of the reaction. A mechanism for the reaction is proposed. Although no conclusive general mechanism could be inferred from the results obtained from the base-promoted cyclisations, the explanation for this unusual reaction may involve steric effects, since it was those alcohols in which both the hydroxyalkyl and alkenyl side chains were flanked by bulky groups (forcing the reacting centres into close proximity) which cyclised in high yield. DA - 1985 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 1985 T1 - Some benzo- and naphtopyrans by novel cyclisations TI - Some benzo- and naphtopyrans by novel cyclisations UR - http://hdl.handle.net/11427/17607 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/17607
dc.identifier.vancouvercitationPestana JAX. Some benzo- and naphtopyrans by novel cyclisations. [Thesis]. University of Cape Town ,Faculty of Science ,Department of Chemistry, 1985 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/17607en_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.titleSome benzo- and naphtopyrans by novel cyclisationsen_ZA
dc.typeDoctoral Thesis
dc.type.qualificationlevelDoctoral
dc.type.qualificationnamePhDen_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceThesisen_ZA
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