No description available.

Three heterosubstituted boranes were successfully synthesized from the corresponding amines and borane dimethyl sulfide (BH3·DMS) in high yields, and were noted to be significantly more stable than the analogous dioxo-compounds. In situ 11B NMR spectroscopy indicated that the mechanism of the reaction to form these boranes contains two intermediates and supports a step-wise addition mechanism. 15N NMR spectroscopic analysis of the boranes identified a downfield shift in the location of the nitrogen signal from the typical amine region towards the aromatic region, supporting the theory of electron back-donation from the nitrogen lone pair to the boron atom’s vacant pz-orbital. The three boranes proved to be suitable hydroboration reagents under microwave-assisted conditions, with Wilkinson’s catalyst and a rhodium(I) carbonyl hydride catalyst both showing catalytic ability, however yields were noted to be dependent on the borane, the olefin and the catalyst. Twelve heterosubstituted boranes were successfully synthesized in high yields as products from condensation reactions between diamines and boronic acids both in solution and under microwave-assisted solvent-free conditions, which resulted in the reaction time being reduced from three hours to 15 minutes. 15N NMR spectroscopic analysis of these compounds showed a similar downfield shift in the amine signal as was observed previously, lending support to the electron back-donation explanation for the stability of these compounds. Crystals suitable for X-Ray diffraction analysis were grown for four 1,8-diaminonaphthalene-based boranes, and analysis of the data showed that the compounds are not planar as originally thought, rather there is a degree of torsion inherent in each of the structures, ranging from a slight (3-4%) to a substantial deviation (19-20%). It was shown that heterosubstituted boranes can be used in Petasis reactions as the organoborane reagent in a number of cases, although the reaction conditions used were not optimized for these compounds. Microwave irradiation was also successfully employed in the Petasis reactions, which reduced the reaction time from 48 hours to 10 minutes. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.

Zhang, Jian. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 263-289). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

Zheng, Fangrui. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references (leaves 181-197). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

The high temperature transformations of trialkylboranes were investigated in the range: 50- 200 ºC. The extent of dealkylation was found to be linked to temperature with ca. 10% octene liberation from tri-n-octylborane at 150 ºC in the absence of bulk solvent. Analysis of the oxidised samples from the dealkylation investigation shows that, whereas the control experiment shows no back-isomerisation of tri-n-octylborane at 150 ºC, the addition of 10 mol% of DMF, DMSO, HMPA and trimethoxyphosphate results in back-isomerisation of the alkyl chain. In general, the addition of Lewis base catalyst was found to enhance the extent of dealkylation. In a supporting 11B NMR spectroscopy study to understand the interaction of trialkylboranes and Lewis bases, the interactions of a series of oxygen and phosphorous donor Lewis bases with tri-n-butylborane were found to be favourable, as indicated by large negative binding enthalpy ( HBIND) and entropy ( SBIND) values. Only the trialkylamine Lewis bases were found to have unfavourable interactions with tri-nbutylborane, as indicated by positive HBIND and SBIND values. The results also show that the chemical shift of the adduct at infinite dilution ( 11 B = ) is not as reliable a measure of the interaction between the two species and that correlation of binding constant (logKBIND) at 25.0 ºC to GBIND defines a linear trend that orders the Lewis bases according to spontaneity of the interaction with the strength of the dative bond formed. The applicability of 11B NMR spectroscopy to the study of the reactions of boranes and alkylboranes was extended to the investigation of the reduction of nitriles by BH3.SMe2 in dichloromethane (15-30 ºC). Results from the kinetic study indicate that the overall reduction with BH3.SMe2 is associative ( Sactivation = -71 ± 10 J K-1 mol-1), with the dependence of kobs data on SMe2 concentration highlighting the importance of the dissociation of the SMe2 from BH3 to the reduction process. The lack of reaction with propionitrile and benzonitrile at 25 ºC can be attributed to lack of stability of their adducts with BH3 as demonstrated by the small equilibrium constants for the formation of their adducts with borane; as determined by 1H NMR spectroscopy and further illustrated by computational calculation of their energies at the B3LYP/6-31G* level of theory. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2008.

No description available.

No abstract available. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2004.

Submitted in fulfillment of the requirements for the award of the Degree of Master of Applied Science in Chemistry, Durban University of Technology, Durban, South Africa, 2016. / The 𝛼-aminophosphonates (APs) and dihydropyrimidinones (DHPMs) exhibit a wide range of important biological activities. The great potential of these compounds in biological applications prompted an increased interest in the development of efficient synthetic methods for their preparation. A novel rhodium supported boron nitride (RhBNT) material was synthesized by simply mixing boron nitride in a solution of rhodium acetate, under inert atmosphere for 7 days followed by filtration; the yield was 95 %. It exhibited excellent catalytic properties for the synthesis of 13 novel APs and 5 DHPMs. Characterization of RhBNT was performed by several techniques: the crystalline nature of RhBNT and nano size was confirmed by SEM spectroscopy, EDX pattern for RhBNT showed signals for rhodium metal, the Brumnauer-Emmett-Teller (BET) analysis showed the specific surface area of RhBNT to be 28.12 m2/g, pore volume 0.23cm3/g and pore size of 199.8Aº thereby suggesting RhBNT as a potentially effective catalyst for organic reactions; the mesoporous nature of the material was established by a type- IV adsorption isotherm; the DSC-TGA Profile indicates that RhBNT has good thermal stability and can be used adequately for catalysis. The DSC curve showed evidence of a broad exothermic peak. The RhBNT was subsequently used in the Kabachnik-Fields and Biginelli reaction in order to assess its catalytic potential. Herein Vilsmeier-Haack reagent was used to synthesize 4-oxo-chromene-3-carbaldehyde and 4-oxo-4H-benzo[h]chromene-3- carbaldehyde from 2-hydroxyacetophenone and 1-hydroxy-2-acetonaphthone, respectively. These two carbaldehydes were subsequently used to synthesize thirteen novels APs and five DHMPs using RhBNT as the catalyst The antimicrobial activities of the synthesized compounds were assessed against Escherichia coli, Bacillus cereus, Micrococcus luteus, Staphylococcus aureus and Candida albicans using the disc diffusion method. It was found that none of the compounds inhibited growth of bacteria or fungus. The assessment of toxicity was evaluated by using the brine shrimp lethal test. It was found that six of the novel compounds exhibited more than 50% brine shrimp death and were considered toxic against Artemia sp. and hence unsuitable as a potential drug whilst four compounds were found to be less toxic, exhibiting a brine shrimp death of less than 50%. Molecular docking studies were carried out for 13 APs to estimate their binding interactions with HIV-1 reverse transcriptase. Four APs showed good potential for the inhibition of HIV-1 reverse transcriptase. / M

Chan Kin Fai. / "April 2002." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (p. 151-157). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

"July 2003." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2003. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.