No description available.

Sulfated polysaccharides are widespread in nature. These compounds are implicated in a wide variety of important biological processes such as blood clotting, cell adhesion, and cell–cell communication. However, detailed characterization of their specific biological roles has proved to be very challenging. One reason for this is that the synthesis of even relatively small sulfated oligosaccharides still remains a considerable challenge. A general approach to the synthesis of sulfated carbohydrates was examined in which the sulfate group is incorporated at the beginning of the syntheses as a protected sulfodiester. Towards this end, a series of modified sulfuryl imidazolium salts were prepared and examined as reagents for incorporating 2,2,2-trichloroethyl-protected sulfate esters into monosaccharides.. A more efficient sulfating agent was obtained by incorporating a methyl group at the 2-position of the imidazolium ring. O-Sulfations that required prolonged reaction times and a large excess of the original sulfuryl imidazolium salt (SIS) which bears no alkyl groups on the imidazolium ring, were more readily achieved using the new reagent. Direct regioselective incorporation of TCE-protected sulfates into monosaccharides was achieved using the new imidazolium salt. We have also shown that the new SIS can also be used for the direct disulfation of monosaccharides and that trisulfated monosaccharides can also be prepared from the disulfated compounds. SIS’s bearing the TFE and phenyl groups, were readily prepared. In most instances, both TFE- and phenyl protected sulfated carbohydrates were easily prepared in good yields using SIS’s. Deprotection of the TFE group from secondary sulfates in carbohydrates and aryl sulfates was achieved in excellent yields using NaN3 in DMF. We applied the sulfate protecting group strategy towards the total synthesis of the tetrasaccharide portion of a disulfated glycosphingolipid called SB1a. Efficient routes were developed for the construction of the left- and right-hand protected disaccharide portions of the SB1a tetrasaccharide.

No description available.

The decomposition of three phenyl-substituted 1,2-dithiolium salts, 3,5-diphenyl-, 3-phenyl- and 4-phenyl- in aqueous, ethanol and DMSO solutions have been examined. With bases of the type hydroxide, ethoxide, DMSO, and acetate, the 1,2-dithiolium ion formed adducts reversibly. Orders of adduct stability were determined in ethanol and water. Many of the adducts were unstable and decomposed to monothio-(beta)-dicarbonyls. The monothio-(beta)-dicarbonyls were in turn unstable and decomposed in aqueous media to the corresponding-(beta)-diketone in the case of the monothiodibenzoylmethane. / Reaction of the 1,2-dithiolium ions with sodium sulphide or sodium borohydride led to dithio-(beta)-dicarbonyls. These species were unstable and decomposed to monothio-(beta)-dicarbonyls in the presence of water. It was possible to observe the formation of metal chelates of monothio- and dithio-(beta)-dicarbonyls in DMSO for several systems. Metal ion and ligand stability orders were established. / Chelates of dithio-(beta)-dicarbonyls decomposed to monothio-(beta)-dicarbonyls in the presence of trace amounts of water. Monothio-(beta)-dicarbonyl chelates were also sensitive to water with dibenzoylmethane produced from monothiodibenzoylmethane chelate decomposition. / Mechanisms for 1,2-dithiolium ion decomposition in the presence and absence of metal ions have been proposed.

This thesis concerns the preparation and use of diaryliodonium salts. In Project I various unsymmetrical diaryliodonium salts were reacted with three different nucleophiles in order to study the chemoselectivity of the reactions of the salts. The main focus of this project was to gain a deeper understanding of the underlying factors that affect the chemoselectivity in transition metal-free arylation reactions. They were found to be very nucleophile-dependent. Some nucleophiles were very sensitive to electronic effects, whereas others were sensitive to steric factors. Ultimately, some arenes are never transferred. A very interesting scrambling reaction was also observed under the reaction conditions, where unsymmetrical diaryliodonium salts form symmetrical salts in situ. Project II details the preparation of N-heteroaryliodonium salts via a one-pot procedure. The salts were designed so that the N-heteroaryl moiety was selectively transferred in applications both with and without transition metals. The chemoselectivity was demonstrated by selective transfer of the pyridyl group onto two different nucleophiles. The third project in the thesis discusses the synthesis of alkynyl(aryl)iodonium salts and alkynylbenziodoxolones from arylsilanes. This protocol could potentially be a very useful complement to the existing procedures, in which boronic acids are used. The last part of the thesis (Project IV) describes a C-2 selective arylation of indoles where diaryliodonium salts were used in combination with hetero-geneous palladium catalysis. This transformation was performed in water at ambient temperature to 50 °C, and tolerated variations of both the indole and the diaryliodonium salt. Importantly, several N-H indoles could be arylated. The MCF-supported Pd-catalyst showed very little leaching and it was demonstrated that the main part of the reaction occurred via heterogeneous catalysis. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Accepted.</p>

Thesis (Ph. D. - Soils, Water and Engineering)--University of Arizona. / Includes bibliographical references.

Thesis (M.Ag.Sc.)--University of Adelaide, Dept. of Soil and Water, 2002. / Includes bibliographical references (leaves 78-86).

Thesis (Ph.D.) --Murdoch University, 2003. / Thesis submitted to the Division of Science and Engineering. Includes bibliographical references (leaves 172-181).

Report (M. Eng.)--Virginia Polytechnic Institute and State University, 1991. / Includes bibliographical references (leaves 27-28). Also available via the Internet.

Thesis (M. S.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Pavlostathis, Spyros G.; Committee Member: Huang, Ching-Hua; Committee Member: Hughes, Joseph B.; Committee Member: Sobecky, Patricia A.; Committee Member: Spain, Jim C.