760 research outputs found
Redemption in the work of Francis Stuart
No full textThe idea of redemption is central to an understanding of the work
of Francis Stuart. Through an examination of its development and
expression, it is possible to demonstrate the integrity of his work and
its distinctive qualities. Such a demonstration is necessary because
Stuart's writing has been subjected to comparatively little scholarly
inquiry, although reviews of his work, especially that produced since
1949, suggest that it is impressive and important.
First, a general background to Stuart's work, a discussion of the
special problems associated with reading it, and a summary of his corpus
is provided. This indicates that the idea of redemption is important to
his earliest writing. The state of redemption is shown to be a
necessary apotheosis for Stuart's outcast heroes; it involves spiritual
suffering through which may be found a sense of reintegration and a
higher reality. This is expressed through interrelated themes such as
those of gambler, artist and ordinary man; mystic and criminal; sacred
and profane love; and spirituality and the mundane. The nature of the
redemptive experience is further elaborated by distinctive, complex
motifs, especially the hare, the ark and the woman-Christ. Their
recurrence provides an important element in the unity of Stuart's work.
Because Stuart's idea of the outcast raises important biographical
questions, an examination of the relationship between Stuart's life and
his work is made. Finally, the way in which the idea of redemption
exists in the language structures of Stuart's novels is examined, with
especial reference to his most recent work, The High Consistory. The
thesis shows that the development of the these of redemption
demonstrates the integrity of Stuart's work
National Geographic : understand civil engineering differently
No full textOur undergraduate civil engineering students have access to a rich and diverse bank of textual and graphical knowledge concerning their chosen profession. However, over a number of decades, commentators have raised concerns that our students have insufficient understanding of the role of civil engineering in society. Indeed, the call for universities to educate ‘global engineers’ emphasises the need for our students to be schooled in the humanities, in parallel with their core computational studies. Unfortunately, engineering students in particular, are not accustomed to regular exploratory reading. This paper considers the use of the National Geographic magazine as a means to ignite our students’ curiosity with the world around them. The results from a pilot study and a content analysis of a number of editions from over a decade shows that this periodical regularly carries themes directly concerning the impact of civil engineering in society, be it political , financial environmental , social or ecological
Synthetic, photophysical studies of 2-alkenyl/arylbenzo-1,3,2- diazaborole compounds and their palladium-catalysed cross-coupling reactions.
No full textThesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2013.This study was aimed at investigating the suitability of 2-alkyl/alkenylbenzo-1,3,2-diazaborolane compounds as potential nucleophilic coupling partners in the Suzuki-Miyaura cross-coupling reaction. A range of aryl bromides and iodides bearing electron-donating as well as electron-withdrawing substituents were reacted with 2-alkyl/alkenylbenzo-1,3,2-diazaborolane compounds under the influence of Pd(OAc)2/PCy3 combination. The cross coupling reaction afforded the desired products in yields ranging from 35% to 89% in less than 20 minutes. The catalytic system was found to be versatile and general tolerating a variety of functional groups including OMe, NO2, OH, COOMe and COMe2, thus demonstrating the suitability of 2-alkyl/alkenylbenzo-1,3,2-diazaborolane as coupling partners in the Suzuki-Miyaura cross-coupling methodology. The results from this study have been accepted for publication, full reference: (Sithebe, S., Hadebe, S. W., Robinson, R. S. Tetrahedron, 2011, 67, 4277.)
Encouraged by the successful application of 2-alkyl/alkenylbenzo-1,3,2-diazaborolanes as coupling partners in the Suzuki-Miyaura (SM) cross-coupling reaction, we then extended our studies to investigate the synthesis and subsequent application of 2-arylbenzo-1,3,2-diazaborole analogues as potential coupling partners under the Suzuki-Miyaura cross-coupling reactions. The cyclocondensation of arylboronic acids with the corresponding 1,2-phenylenediamine afforded 2-arylbenzo-1,3,2-diazaboroles in yields ranging from 43% to 93%. The cross-coupling reaction of 2-arylbenzo-1,3,2-diazaboroles with the range of aryl bromides afforded the desired biaryl products in moderate to excellent yields ranging from 62% to 96%. Substrates bearing electron-withdrawing substituents were shown to be more reactive under these reaction conditions affording biphenyls in excellent isolated yields ranging from 83% to 96%. While our yields are comparable with the yields reported in literature, our reactions take only 10 minutes (!) compared to many hours of reflux as reported in the literature.
This project was also aimed at investigating the spectroscopic characteristics of 2-arylbenzo-1,3,2-diazaborole compounds by acquiring and studying their absorption and emission spectra. The data obtained revealed the lack of significant
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solvatochromism for all the compounds in the ground state which is indicative of the presence of low dipole moments. These values were confirmed computationally which showed low calculated dipole in a range 0.1379-2.2773 D. In the excited state, all chromophores are influenced by the polarity of the solvent used pointing to the presence of solvatochromism. The introduction of a donor group such as thioether (MeS) and the introduction of bromine atom, on the π-system, have proven beneficial for the emission maxima of the species investigated.
The extension of π-conjugation length at the 2-position of these species and the methylation at the backbone of 1,3,2-benzodiazaborolyl group leads to bathochromic shifts of the emission maxima, which in turn lead to large Stokes shifts of up to 11000 cm-1. Alternatively, the formal insertion of the phenyl spacer between the naphthyl ring and the 1,3,2-benzodiazaborolyl group does not have any influence on the photophysical properties of these compounds.
The HOMOs solvatochromism for all the compounds in the ground state which is indicative of the presence of low dipole moments. These values were confirmed computationally which showed low calculated dipole in a range 0.1379-2.2773 D. In the excited state, all chromophores are influenced by the polarity of the solvent used pointing to the presence of solvatochromism. The introduction of a donor group such as thioether (MeS) and the introduction of bromine atom, on the π-system, have proven beneficial for the emission maxima of the species investigated.
The extension of π-conjugation length at the 2-position of these species and the methylation at the backbone of 1,3,2-benzodiazaborolyl group leads to bathochromic shifts of the emission maxima, which in turn lead to large Stokes shifts of up to 11000 cm-1. Alternatively, the formal insertion of the phenyl spacer between the naphthyl ring and the 1,3,2-benzodiazaborolyl group does not have any influence on the photophysical properties of these compounds.
The HOMOs of all the chromophore are purely represented by the 1,3,2-benzodiazaborolyl group except for anthracenyl-functionalised benzo-1,3,2-diazaborolane compounds in which the HOMO are located on the π-system with no contribution of the vacant 2pz-orbital of the boron atom. The large Stokes shifts and significant solvatochromism displayed by these compounds are suggestive of the potential application in organic light emitting diodes (OLED) as emitters. The results from this study have been drafted for publication in Dalton Transition
The use of hydroamination in the attempted synthesis of ant alkaloid 223H (xenovenine).
No full textThesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2008.The ability to construct C-N bonds is of great importance to organic chemists as exemplified by the vast number of natural products, pharmaceutical agents and fine chemicals that contain such linkages. An atom efficient C-N bond forming reaction namely hydroamination has attracted much interest to date due to its ability in forming amine, imine and enamine functionality. The scope of this project involved the attempted synthesis of a biologically active and nitrogen containing pyrrolizidine alkaloid isolated from cryptic thief ants and poison dart frogs namely 223H (xenovenine). The method of hydroamination was utilized as the pivotal ring forming step and was established as being
a valuable synthetic tool towards the construction of 223H (xenovenine). The
stereoselective synthesis resulted in the successful formation of ethyl (3R)-5-heptyl-3-methyl-2,3-dihydro-lH-pyrrolizine-7-carboxylate 74, a novel, and structurally analogous precursor to 223H (xenovenine) over 10 synthetic steps from (S)-pyroglutamic acid. The following research also resulted in the synthesis of two other novel compounds namely ethyl 3-[(2R)-2-methyl-5-thioxotetrahydro-lH-pyrrol-l-yl]propanoate 86 and ethyl
3-{(5R)-2-[(E)-2-ethoxy-2-oxoethylidene]-5-methyltetrahydro-lH-pyrrol-l-yl}propanoate 87. A catalytic hydroamination study on the conversion of C-propargyl vinylogous amides into pyrroles demonstrated that transition metal salts of groups 11 and 12 serve as effective hydroamination catalysts. The oxide, acetate, chloride and nitrate derivatives of group 11 and 12 metals namely Cu(II), Ag(I), Zn(II), Cd(II) and Hg(II) were employed as potential hydroamination catalysts in the oxidation states provided. The Zn(II) catalyst
series with the exception ZnO provided the greatest hydroamination yields under mild reaction conditions owing to their high Lewis acidities however the Ag(I) and Hg(II) catalyst series also provided excellent yields of product under more forcing reaction conditions
Photocatalyzed tandem oxidation reactions and their application in the synthesis of quinoxalines.
No full textThesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2009.No abstract available
The application of semiconductors as oxidants in synthetic organic chemistry.
No full textThesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2012.Oxidation of alcohols is a vital transformation in synthetic organic chemistry as evidenced by
their numerous applications in natural product synthesis. However, the traditional oxidants
employ hazardous, toxic and malodorous reagents. A welcome addition to the field of alcohol
oxidation is the emergence of tandem coupling reactions in which the oxidized alcohol is
immediately trapped by an appropriate nucleophile.
In previous research within the group, the synthesis of quinoxalines using a photocatalyzed
tandem coupling approach was demonstrated. However, an extension of this research to other
tandem coupling reactions was unsuccessful due to the high redox potential of the active
oxidizing species. Thus, the immediate goal of this project was to develop a photocatalyzed
oxidative system that was selective and high yielding. The assembling of this photooxidative
system began with the choice of TiO2 and ZnO as the photocatalysts, Alizarin Red S as the
dye, silver (I) ions as the electron acceptor and 2,2,6,6-tetramethylpiperidine-1-oxyl radical
(TEMPO) as the active oxidizing species. A test reaction was conducted using the dye
sensitized TiO2/silver/TEMPOand dye sensitized ZnO/silver/TEMPO systems. While the dye
sensitized ZnO system afforded a good yield the dye sensitized TiO2 system produced only a
trace amount of product. Thus, a full study was conducted on a range of alcohols using the
developed dye sensitized ZnO system. In addition, the oxidation of alcohols using the dye
sensitized ZnO system could also be scaled-up with notable success. The developed system
was applied to a one-pot tandem Wittig reaction which unfortunately was unsuccessful. The
dye sensitized ZnO/silver/TEMPO system was however successful when applied to a pseudo-
tandem Wittig reaction.
Subsequently, an electron paramagnetic resonance (EPR) study was conducted using the dye
sensitized TiO2/silver/TEMPO and the dye sensitized ZnO/silver/TEMPO system. The results
of the EPR study supported the proposed mechanism for the dye sensitized ZnO system and
revealed a ‘break’ in the photooxidative chain for the dye sensitized TiO2 system which
accounted for the low yields obtained.
As part of our interest in developing new photocatalyzed oxidative systems, attention was
directed towards the application of impure diamondoid powder as a potential tandem
coupling reagent. Using the diamondoid powder, the synthesis of highly conjugated
quinoxalines was effected in moderate to excellent yields
Towards the synthesis of biotinylated boron compounds and 1, 3, 2 benzodiazaboroles derivatives and their application as potential BNCT delivery agents.
No full textM. Sc. University of KwaZulu-Natal, Pietermaritzburg 2015.In this study, boron neutrons capture therapy (BNCT) principles which have been reported as the best treatment of glioblastoma multiforme tumors thus far were explored. The aim of this study was to synthesizing boron containing compounds which have a potential as boron delivery agents (BDA) with enhanced tumor selectivity. The tumor identification moiety chosen was biotin (a vitamin H) which is essential for every cell’s metabolism. The mechanism in which biotin accumulates in the tumor cell is through the receptors which are over-expressed in the tumor cells. Therefore the possibility that biotinylated boron compounds could be deposited more on tumor cells than to healthy cells is high.
The synthetic approach involved the synthesis the boronic acids, 4-anilineboronic acid and 4-(hydromethyl) phenylboronic acid followed by their conjugation with D-biotin. These two boronic acids were chosen because their reactive grouping (OH, NH2) could bind to the carboxylic acid reactive part of D-biotin via the formation of an ester linkage. Of these two boronic acids, 4-(hydromethyl) phenylboronic acid was successfully synthesised and biotinylated at 62% yield to form a new boron compound.
In this project it proposed that the addition of a fluorescent marker on this biotinylated compounds could potentially improve their imaging properties. The luminescence properties and stability of 1,3,2-benzodiazaboroles derivatives have been reported in literature. In this project, 1,3,2-benzodiazaboroles derivative of biotinylated boronic acid (already synthesised) was in 72% when reacted with o-phenylenediamine. It is anticipated that this compounds could have better tumor solubility, water solubility, less toxicity (brought about by the attached biotin) and enhanced luminescent properties (as reported for all 1,3,2-benzodiazaboroles derivatives). However, the biological testing on these compounds was not performed in this study
Ultrastabilized boranes : a study into the synthesis, structure and reactivities of heterosubstituted organoboranes.
No full textThesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.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, 2011
An instrumental evaluation of selected metal functionalised semiconductors in the facilitation of photo-organic transformations.
No full textDoctoral Degree. University of KwaZulu-Natal, Pietermaritzburg.Throughout this research study, various strategies to design, synthesise and test the photo-reactivity of attenuated wide band gap semiconductors in alcohol oxidation studies have been explored. An alizarin red-sensitised zinc oxide photocatalyst which was stabilised in a silver-sodium electrolyte effectively facilitated a broad aromatic and aliphatic alcohol oxidation table with reported conversions ranging from 10 to ≥ 99 %. A systematic characterisation of the alizarin red-sensitised zinc oxide investigated the photoelectronic migrations across the alizarin red–zinc oxide interface and detected the transfer of electrons from the highest occupied molecular orbital of alizarin to the defect site of zinc oxide at 507 nm.
Further studies were directed towards the development of a novel titanium dioxide semiconductor that was activated by visible light. Three attempted strategies (pseudo perovskites [Cu3TiO5, Ni3TiO5, and Mn3TiO5], silver functionalised cadmium sulfide and a heterojunction between cadmium sulfide and titanium dioxide) explored the possibility of lowering the band gap potential of wide band gap semiconductors through metal ion functionalisation (Cu, Ni, Mn, and Ag) and heterojunction principles for the purpose of finding applications in mediating alcohol oxidations.
Whilst the three strategies were unable to demonstrate viable photocatalytic properties, the instrumental insight obtained during the process identified a suitable three-component semiconductor system (Cu/Pd-N-TiO2). Cu/Pd-N-TiO2 was extensively characterised with an array of instrumental techniques, thus developing an in-depth understanding of the photophysical properties that governed the photo-oxidative transformation of a range of cyclic alcohols and in the remediation of two dyestuffs typically associated with environmental contamination
Hydroboration studies of olefins with heterocyclic hydroborating reagents with various transition metal complexes : attemped diastereoselective synthesis of homoallylic alcoholics via hydroboration.
No full textMaster of Science in Chemistry. University of KwaZulu-Natal, Pietermaritzburg 2016.Abstract available in PDF file
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