| Popis: |
The work in this thesis is divided into three parts: (A) Investigation of the synthesis of lactones from sulfoxonium salts; (B) Investigation of the synthesis of cyclohexanones from donor-acceptor cyclobutanes and ketenes; (C) The synthesis of cyclopentanones from donor-acceptor cyclopropanes and ketenes. A synthetic route to formation of a delta-lactone from cyclopropylamino sulfoxonium salts was initially explored. Multiple reactant partners (e.g. lithium enediolate, lithium enolates, ketene) were tested and although lactone formation was not achieved, ring-opening of the cyclopropyl salt was observed under much milder conditions than previous literature findings (0°C to RT vs >65°C). Research into the synthesis of monocyclic gamma-lactones from vinyl sulfoxonium salts was also pursued. This work was inspired by previous work from the group and aimed to introduce new substitution patterns on the gamma-lactone ring. Both the phenyl-substituted vinyl sulfoxonium salt and the isopropyl-substituted vinyl sulfoxonium salt were investigated for this reaction. Carboxylic acids such as dichloroacetic acid, α-methoxyphenylacetic acid, methoxyacetic acid, benzyloxyacetic acid, 4-methyl-2-phenylpentanoic acid and 4-methylvaleric acid were tested as enediolate precursors. Different bases such as LDA, NaHDMS and n-Butyllithium were tested to verify their ability to deprotonate the carboxylic acid to enable gamma-lactone formation to occur. Other significant research was carried out on the development of a synthetic route to cyclohexanones from donor-acceptor cyclobutanes and ketenes. The reactant partners for this reaction have been synthesized in good yields, the phenyl-substituted donor-acceptor cyclobutane being synthesized in 54% yield, and its precursor 1,3-dibromopropylbenzene synthesized in yields of up to 82%. A variety of Lewis acids including InBr3, AlCl3, In(OTf)3, Sc(OTf)3, Yb(OTf)3 and GaCl3 were explored for their effectiveness in promoting the [4+2]-cycloaddition reaction. Most significantly, through the reaction of a donor-acceptor cyclopropane and a ketene generated in-situ from propionyl chloride a range of substituted cyclopentanones were also synthesized in yields ranging between 60-78%. |
