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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
61

Synthesis, binding studies and click modification of diazido acridine intercalators : a versatile two-step approach to functional nanomaterials

Moradpour Hafshejani, Shahrbanou January 2013 (has links)
Two diazido acridine drivatives, N,N'-(acridine-3,6-diyl)bis(2-azidoacetamide), PD and 3,6-bis(2-azidoacetamido)-10-methylacridin-10-ium, PDMe⁺ were prepared from 3,6- diamino acridine, Pf. The azide groups were exploited by click chemistry to synthesise functional intercalators by reaction with the alkyne-bearing groups, ethynyl ferrocene EFc, phenylacetylene, N-pentynyl-2-(2-thienyl)-pyrrole pent-TP and acetylene-PEG4- carboxyrhodamine, APCR. The click reaction products were characterised by ¹H NMR spectroscopy, ¹³C NMR spectroscopy, ES-MS, IR and, where appropriate, cyclic voltammetry. IR studies showed the disappearance of the azide and alkynyl stretching signals at 2114 cm⁻¹ and 2112 cm⁻¹ respectively after the click reaction. Cyclic voltammetry revealed that the click product with EFc was redox active, E = 346 mV compared to 441 m V for the free EFc, a negative shift due to the electron donating effect of the triazole ring. Intercalation of PD and PDMe⁺ into DNA, were studied by UV/vis, fluorescence, circular dichroism (CD), linear dichroism (LD) and DNA denaturation experiments. The titration of Pf and PDMe⁺ with DNA showed bathocromic and hypochromic effects in the absorption spectra. However, for PD an interesting phenomenon, a bathochromic and hyperchromic effect was observed. The pKa of PD (4.3) suggests that as PD approaches DNA it becomes protonated due to the low local pH and so aids binding to DNA. Both UV and fluorescence titrations gave DNA binding constants for Pf, PD and PDMe⁺ of ≥ 3.8 × 10⁶, 5.3 × 10⁵ and 2 × 10⁶ respectively. These findings were consistent with the observed increasing stabilisation of the double helix by the intercalators, PD < PDMe+ < Pf. DNA complexes of PD and PDMe⁺ were click modified with EFc, pent-TP and APCR and characterised by ES-MS, UV/vis, IR, fluorescence microscopy, LD, atomic and electrostatic force microscopy (AFM and EFM), and cyclic voltammetry. As for the free reaction, cyclic voltammetry, IR and UV/vis spectroscopy confirmed the successful click reaction of the DNA complexes, but could not confirm PD or PDMe⁺ remained intercalated after click modification. AFM studies confirmed DNA retained its natural wire-like topology after intercalation and click functionalization. Fluorescence microscopy images of DNA complexes with PD and PDMe⁺ that had been click modified with APCR showed illuminated strands 17 μm in length, comparing well with the dimensions of λ-DNA. LD experiments indicated that PDMe⁺ reamains inserted into the DNA helix after the click reaction was performed in-situ using pent-TP.
62

New reactions of diazonium and related compounds

Baigrie, Brian Devlin January 1973 (has links)
No description available.
63

Acylation and alkylation reactions of biphenyl- and n-phenylpyrrole-alkanoic acid derivatives

Leitch, David S. January 1970 (has links)
No description available.
64

Hydrogen bonding : a tool for synthesis and control of motion in rotaxane and catenane architectures

Wong, Jenny Ka Yan January 2002 (has links)
Although mechanical interlocking at the molecular level can be achieved through statistical or covalently-directed methods, the most effective and efficient routes to rotaxane architectures invoke supramolecular assistance - the use of attractive noncovalent interactions between the macrocycle and thread (or their precursors) - to preorganise the components prior to interlocking. Hydrogen bonding offers a particularly powerful method for preorganising precursors in such a way that efficient interlocking of the components to form rotaxanes and catenanes can occur in high yields. The restricted degrees of freedom inherent in rotaxane and catenane architectures also make them attractive candidates as components for molecular level devices. This thesis outlines the investigation of the role of hydrogen bonding in the assembly of rotaxane architectures; how it can be used as a directing tool for synthesis and in the control of sub-molecular motion, including (i) controlled translational of the components of two-station rotaxanes and (ii) unidirectional rotation in a catenane system incorporating three different stations. The submolecular movements are mediated using heat and light.
65

New routes to the generation of alkyl metaphosphates in solution (I) ; and, Synthesis of novel phosphorus-containing scale inhibitors for use in oil-field operations (II)

Kilgour, Derek January 1995 (has links)
The work described in part I of this thesis is concerned with the development of a number of approaches designed to generate alkyl metaphosphates in solution. In each approach the final reaction step involves the crucial breakdown of a suitable precursor with a σ-bond being both broken and formed at a central phosphorus atom. Two main routes to alkyl metaphosphates were investigated. The first involved the condensation of a novel disodium pyrocarbonate salt with alkyl dichlorophosphates to form cyclic pyrocarbonate phosphates. These novel cyclic phosphates then underwent chelotropic breakdown with the release of two moles of carbon dioxide to produce alkyl metaphosphates. The second route investigated involved the condensation of potassium hydrogen carbonate with an alkyl dichlorophosphate to form a mixed anhydride. Upon warming breakdown of the mixed anhydride occurred, with the release of one mole each of hydrogen chloride and carbon dioxide to produce alkyl metaphosphates. In each case when the reactions were repeated in the presence of epoxides, the alkyl metaphosphates were trapped with the formation of 1,3,2-dioxophospholane-2-oxides. This reaction was valuable in providing evidence for the intermediacy of alkyl metaphosphates and demonstrated unequivocally their high electrophilic character. <SUP>31</SUP>P NMR spectroscopy was found to be an invaluable tool for following the course of the reactions being investigated. This was demonstrated by the fact that when alkyl metaphosphates were formed in the absence of trapping reagents, self-condensation occurred to give linear and cyclic polyphosphates which were easily identified by <SUP>31</SUP>P NMR signals in the δ-10 and -20 ppm regions. When trapping by epoxides was carried out these signals were replaced by a closely matched pair of peaks in the range δ 16-18 ppm which were unique to diastereomeric mixtures of cyclic phosphates having five membered rings.
66

Polymerization Studies using homogeneous and supported metallocene catalysts

Monterio, Mario G. Kool January 1998 (has links)
A literature survey of the main aspects of the polymerization of olefins using homogeneous and silica, alumina and niobia supported metallocene catalyst systems is presented. Fundamental information about the surface of niobia and its use as a catalyst support is included. A study of kinetics of polymerization of ethylene was conducted using homogeneous bis(cyclopentadienyl)zirconium dichloride-MAO catalyst systems and its silica, alumina and niobia supported analogue catalyst systems. The characterization of the polyethylene produced by such catalyst systems, focussing on the molecular weight distribution, melting behaviour and morphology of the polymer was carried out.
67

[4+2] and [4+3] cycloaddition reactions and Lewis acid catalysed cycloisomerisation of malonyl epoxides

Ahmed, Awais January 2003 (has links)
Donor-acceptor cyclopropanes have been extensively used in synthetic chemistry in [3+2] and [3+3] cycloaddition reactions for the preparation of highly substituted carbo- and heterocyclic products. This methodology is further extended to donor-acceptor cyclobutane in [4+2] and [4+3] cycloaddition reactions for the synthesis of highly substituted carbo- and heterocyclic products. Initial work carried out makes use of cyclobutanes substituted with a metal-alkyne complex towards the synthesis of tetrahydropyrans in good yields and with acceptable diastereoselectivity. The initial aim of the project was to improve and expand the scope of the previous work carried out within the group on [4+2] cycloaddition reaction. For example, [4+2] and [4+3] cycloaddition reaction were carried out by using diester cyclobutanes having an alkene and phenyl π-donors. The [4+3] cycloaddition reaction of cyclobutane with nitrone did not work but [4+2] cycloaddition was successful when aldehydes were used as trapping reagents. Lower yields of the cycloadducts were observed due to formation of (±)-dimethyl-2-methyl-6-phenylcyclohex-3-ene-1,1-dicarboxylate and 2,6-diphenyl-4,8-dipropenylcyclooctane-1,1,5,5-tetracarboxylic acid tetramethyl ester. During the synthesis of a precursor cyclobutane a novel cycloisomerisation of malonyl epoxide under Lewis acidic conditions to 6,8-dioxabicyclo[3.2.1]octane derivatives was developed. This reaction has opened a new pathway for the synthesis of 6,8-dioxabicyclo[3.2.1]octanes in a diastereoselective fashion using malonyl epoxides as precursors. A wide range of malonyl epoxides were cycloisomerised under Lewis acidic conditions and the cycloisomerisation of syn and anti malonyl epoxides were stereospecific. The diastereoselectivity of the process was proven by nOe and X-ray analysis. The cycloisomerisation of malonyl diepoxide has also been investigated towards the formation of 5,5-dimethoxy-6,6,8,8-tetraoxa4,4-spirobi[bicyclo[3.2.1]octane].
68

The chemistry of new cyclic phosphorus(III) ligands

Ekubo, Allen T. January 2009 (has links)
A range of new aniline derivatives of tetrakis(hydroxymethyl)phosphonium chloride represented as [P(CH2NHR)4]Cl, where R = phenyl or a substituted phenyl group were synthesised by reacting tetrakis(hydroxymethyl)phosphonium chloride with different aniline precursors in EtOH. Similarly, new phenylenediamine derivatives of tetrakis(hydroxymethyl)phosphonium chloride [P{(CH2NHhRh]Cl, [R = C614, C6H3Me, C6H3COPh, C6H2C414] were synthesised by reacting tetrakis(hydroxymethyl)phosphonium chloride with phenylenediamine precursors. Selected aniline derivatives of tetrakis(hydroxymethyl)phosphonium chloride were reacted with triethylamine in acetone at room temperature to give the corresponding diazaphosphorinane ligands cyclo- {CH2N(R)CH2N(R)CH2-P}-CH2N(H)R , where R = phenyl or a substituted phenyl group. Some of the diazaphosphorinane ligands were reacted with Ru(II), Rh(III), Ir(III) , Pd(lI) and Pt(lI) precursors to form new transition metal complexes.
69

Investigation of silica supported Pd catalysts for aerobic alcohol oxidation

Lu, Liang January 2014 (has links)
Oxidising alcohol to their corresponding carbonyl compound is still a vitally important reaction for the fine chemical and pharmaceutical industries. In this thesis the investigation of the use of Pd(II) catalysts for the oxidation of alcohols using 02 as the terminal oxidant is reported. The initial section describes the investigation of ligand effects on Pd(OAc)2 operating under homogeneous conditions. The examination into the use of different gas mixtures showed that 02/C02 was beneficial due to the formation in situ of alkylcarbonic add by the reaction between C02 and the alcohol substrate. The heterogenisation of Pd(II) catalysts and an efficient silica adsorbed Pd catalytic system is also considered. Compared with previous homogeneous catalysts, the new Pd systems show encouraging activity on a silica support. As a development of this, more stable and durable Pd catalysts have been prepared using several different kinds of covalent tether to silica and tested for the Pd catalyzed aerobic alcohol oxidation.
70

"2'-deoxy-6-thioguanosine : synthesis of monomer, oligomers and long DNA, and their binding with metal ions

Hribesh, Samira January 2013 (has links)
The formation of one-dimensional (1D) coordination polymers using thiolated DNA nucleosides and nucleotides with transition metals was investigated. 2’-Deoxy-6- 1 13 thioguanosine was successfully synthesised and characterized by H-NMR, C-NMR, IR, MS and UV spectroscopy. Subsequently, the binding of several transition metal ions to 2’-deoxy-6-thioguanosine and 6-thioguanosine was studied. The binding ratio of thio-monomer with metal ions was shown to be three ligands to one metal in the case of cobalt (II) and nickel (II), whilst in the case of the cadmium (II)-complex with the thio-monomer, the results suggested that a 1D coordination polymer might be formed, although no crystal data was obtained to confirm this structure. Therefore, the oligonucleotides containing the thiolated monomer were synthesised to extend this study. The preparation of thiolated homo-guanosine oligomers involved standard solid phase synthesis of oligo-guanosine followed by on-column conversion of guanosine to 6-thioguanosine. The thiolated reaction was the same as that used for the monomer and yielded 2-, 3-, 4- and 5-mer thio-oligomers in good yield. The thio-oligomers were purified by HPLC and were fully characterized by mass spectrometry and UV. The interaction of thio-oligomers with cadmium (II) ions was investigated. For the dimer and tetramer, the binding ratio was two thio-bases bound to one cadmium, whereas for the trimer and pentamer the binding ratio showed more than one binding species in solution. In order to synthesise a long thiolated DNA polymer, an enzymatic slippage reaction was performed, where a short primer-template of poly (dG)-poly (dC) was 1010 - extended up to 300 bp using Klenow exo polymerase and nucleosides triphosphate (d-tGTP and d-CTP). The addition of cadmium ions to thio-modified DNA suggested a structure resembling M-DNA as coordination polymer is obtained according to UV titration data.

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