In Part 1, the Diels-Alder adducts of trimethyl cyclopentadienylstannane (I.3) with maleic anhydride and fumaronitrile are prepared in 61% yield. The molecular structure of the adduct with maleic anhydride (1.6) is unequivocally established as 7-syn-trimethy1stannyl-endo- bicyclo[2.2.1]hept-5-enyl-2,3-dicarboxy1ic anhydride by single crystal X-ray structure analysis. In Part II, the high yield preparation of some new S-a1ky1-Saryl- N-p-toluenesu1fonylsu1foximines, by ruthenium tetroxide oxidation of the corresponding su1filimine, is described. Dehydrochlorination of S-chloroethy1-N-p-toluenesu1fonyl-S-p-toly1su1foximine and its S-phenyl analog with triethylamine gives the previously unknown N-p-to1uenesu1fony1- S-p-to1y1-S-viny1sulfoximine (II.17) and its S-phenyl analog. The Diels-Alder reaction of II.17 with a variety of 1,3-dienes and the known N-phtha1imido-S-p-tolyl-vinylsu1foximine (11.14) and the previously unreported S-p-nitropheny1-N-phtha1imido-viny1su1foximine (11.39) with cyclopentadiene are described. All of the reactions give mixtures of the possible adducts. The configuration of the major diastereomer (II.19d) of the adducts of II.14 with cyclopentadiene is known from a single crystal X-ray structure analysis. The structures of the other adducts are determined by ¹H NMR spectroscopic analysis. Chemical correlation of II.19d with the adducts of II.17 with cyclopentadiene confirm the assignment made by ¹H NMR. A competition Die1s-Alder reaction between II.17 and p-toly1-viny1sulfone shows that the vinylsulfoximine is more reactive. Sodium amalgam reduction of the cyclohexadienyl adducts of II.17 gives bicyclo[2.2.2Joctene and hydrazine in allyl alcohol reduction of adduct II.19d gives the corresponding sulfoxide II.20d.

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Master / Master of Philosophy

published_or_final_version / abstract / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

No description available.

It has been shown that alkaloids from various sources are vital as lead compounds in medicinal research and thus also the efficient synthesis of these. With the goal of developing a general synthetic route that can potentially access pyrrolizidine, indolizidine, quinolizidine and possibly lehmizidine alkaloid skeletons, a modified route that has been shown to produce pyrrolizidines was employed towards the synthesis of indolizidine alkaloid 223AB. Within this synthesis, a 6-endo-dig hydroamination-cyclization step was attempted for construction of the bicyclic system. For this purpose, a selection of titanium-based catalysts were synthesized in order to determine their regiochemical outcome. For the purpose of investigating ab initio the mechanism of regioselective hydroamination, the skills and methods involved in computational chemistry were acquired through a study into amide rotational barriers: A range of novel 2-oxo-2H-chromen-7-yl dimethylcarbamates were synthesised containing either an oxygen or sulphur in the α-position to the carbonyl or thiocarbonyl group of the amide moiety. Microwave synthesis was essential for the successful synthesis of some of the sulphur containing carbamates. The barriers to internal rotation of each of these compounds were investigated as follows. Variable Temperature and Exchange Spectroscopy NMR was performed on these compounds and the barrier to free amide rotation was calculated. Each of these compounds were also modeled ab initio and the gas phase barrier to rotation calculated. These three sets of data were compared and the influence of the α-heteroatom on rotation for amides and thioamides evaluated. / Thesis (M.Sc.) - University of KwaZulu-Natal, Pietermaritzburg, 2008.

The aim of this research project was to investigate the oxidation reactions of olefins to ketones. Initial studies revolved around the oxidation reactions of terminal olefins to symmetrical dialkyl ketones. The inability to isolate pure products, and the consumption of large amounts of the expensive palladium catalyst for each run as well as the extremely low yields that resulted from these oxidation reactions, made it difficult to thoroughly investigate this oxidation system. It was then decided to embark on the investigation of oxidation reactions of a-olefins to methyl ketones. For these studies, six terminal olefins were oxidised to methyl ketones employing seven different oxidation reactions. One of the most important and pioneering reactions m this field is the system employing PdCl2 / CuCl2 / O2 for the oxidation of terminal olefins to methyl ketones, namely the Wacker oxidation reaction. Experimental results, however, indicated that high product contamination from by-products resulted from these oxidation reactions despite the fairly good yields of product from the Wacker oxidation system. Some reaction systems that have been developed from the Wacker oxidation system were also investigated. The oxidation system employing PdCl2 / p-benzoquinone for the oxidation of terminal olefins to ketones was studied. The oxidation reactions resulted in incomplete oxidation with higher olefins (l-decene, l-nonene and l-octene), and complete oxidation of lower olefins (l-heptene, l-hexene and l-pentene) under the same reaction conditions. The products from lower olefins oxidised under these reaction conditions were pure and high yielding Another system that proved efficient both with feasibility and good yields of products was the oxidation system employing Pd(OAc)2 / H202 catalyst to oxidise terminal olefins to methyl ketones. Phase transfer catalysis has been employed in organic chemistry to effect different reactions. In this case two types of phase transfer agents were employed to effect the oxidation of terminal olefins to ketones. The first oxidation system involved the use of a PdCl2 / CuCl2 / O2 catalyst with a quaternary ammonium salt, cetyltrimethylammonium bromide (CTAB), to govern the course of the reaction. Reasonable yields were obtained, and moderate purity of products was also observed. The second phase transfer catalysis system employed polyethylene glycol (PEG-200) as a phase transfer agent, and PdCl2 / CuCl2 / O2 as a catalyst for oxidation of olefins to ketones. This oxidation system resulted in different isomers of a ketone from a terminal olefin. Pure methyl ketones were not isolable from the mixture of methyl and ethyl ketones. The oxidation reactions of olefins to ketones employing Pd(OAc)2 / p-benzoquinone in combination with electrolysis were also investigated. The unique feature about these reactions was the fact that cyclic olefins could also be oxidised under these conditions. Good yields were obtained, and high product purity was observed. One of the important oxidation reactions investigated during the project was the reaction that used an alternative metal to the expensive palladium catalyst for the oxidation reactions to ketones. This oxidation system employs CuCl2 / 18-C-6 / acetaldehyde as a catalyst for the oxidation of hydrocarbons to ketones and alcohols. It was discovered during the investigation that olefins can also be used as substrates and are oxidised to the corresponding ketones. The use of olefins as substrates resulted in higher yields than the hydrocarbon oxidation reactions, and less contamination in the product mixture was also observed. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1997.

No abstract available. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2009.

The cytosolic second messenger D-myo-inositol 1,4,5-trisphosphate (InsP₃), has the ability to mobilise Ca²⁺ from intracellular stores. Ca²⁺ controls a wide range of cellular processes, such as cell division and proliferation, apoptosis, fertilisation, gene transcription and muscle contraction. A number of potent InsP₃ receptor agonists are currently known; however, no selective InsP₃Rs antagonists have been reported to date. Using the X-ray crystal structure of the mouse type 1 InsP₃R, a range of analogues (below) has been designed with the intention of these compounds acting as competitive InsP₃Rs antagonists. The successful syntheses of these compounds are reported herein.