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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.
21

Cyclic sulfamidates as pseudo-alkyl halides in Sp3 -based cross-coupling chemistry

Ursinyova, Nina January 2014 (has links)
The use of cyclic sulfamidates as pseudo-alkyl halides in Sp3 -based cross-coupling chemistry has been studied and two approaches were explored. The first approach involved a transition metal-mediated cross-coupling of cyclic sulfamidates, including studies into the oxidative addition step of the catalytic cycle. Various transition metal catalysts (palladium, nickel and iron) and nucleophiles (zinc, boron, magnesium and tin reagents) were investigated. After extensive screening, the desired cross-coupling was achieved under palladium-catalysed Suzuki-Miyaura conditions, albeit in a low yield (20%) and with poor mass recovery. The second approach, via enantiomerically pure f3- and y-aminoalkyl boronic esters, required development of efficient conditions for borylation of cyclic sulfamidates. A range of known and novel 1,2- and 1,3-cyclic sulfamidates was synthesised and subjected to the optimised borylation conditions to determine the scope of this transformation. Mechanism of the copper-catalysed borylation process was also explored, together with the utility of boronic esters in sp3 _Sp2 and Sp3 _sp3 cross-coupling reactions. Aminoalkyl boronic esters (from borylation of cyclic sulfamidates) were also assessed as possible substrates for Matteson homologation. After extensive screening, it was found that f3-aminoalkyl boronic esters (from 1,2-cyclic sulfamidates) can be homologated in a 50% yield, while y-aminoalkyl boronic esters are completely unreactive to a range of homologation conditions.
22

Improved NMR-based methods for molecular structure elucidation

Tatolo, Godiraone January 2014 (has links)
The use of 1H_I3C NMR correlations and its corresponding I1JCH has found a tremendous use in structural elucidation of organic compounds. Chapter 1 highlights different methods for determination of IH_13C correlations and for the measurement of I1JCH. In this work we reported two improved methods for determination of IH_I3C correlations (CTgc2HMBC) and, for the measurement of nJCH (SelEXSIDE). Chapter 2 describes the work undeliaken in order to quantify improvements to the gradient heteronuclear multiple bond correlation (HMBC) experiment specifically to design a constant time gradient HMBC (CTgc2HMBC) with adiabatic pulses. This was done in order to remove IH_IH modulation during fl , which causes cross-peak broadening, to simultaneously maximise sensitivity and resolution and then compare their performance against comparable non-constant time experiments. CTgc2HMBC experiment has shown slightly narrower cross peaks in the FI dimension which is maximised at high FI resolution especially 20 Hz/pt, compared to analogous gc2HMBC which is limited by IH-IH modulation. The CTgc2HMBC has been shown to be more efficient for weak IH_ 13C correlations. Chapter 3 describes the improvement made to the slow, easy to use EXSIDE sequence. The EXSIDE sequence was made to be doubly-selective in both the FI (I3C) and F2 (IH) domains. The modification, named Sel-EXSIDE reduces the number of tl datapoints used by reducing the FI spectrum width substantially, and thus reducing a multi-hour (7 hours 30 minutes 0 f experiment time to 0 btain 3 -7 co up ling co nstants) experiment to a matter of minutes (less than 10 minutes to obtain one coupling constant) while still allowing nJCH coupling constants to be resolved to -I Hz/pt resolution. The SelEXSIDE pulse sequence has been shown to work for determination of all measurable nJCH for both small (2-ethylI- indanone) and large (strychnine) organic molecules. Coupling constants obtained using SelEXSIDE, gave low mean errors and standard deviations when compared to other methods like Line-fitting procedures and calculated values using DFT.
23

Towards functional nanostructures by crystallisation-driven self-assembly

Lunn, David John January 2014 (has links)
This Thesis describes the synthesis, functionalisation and self-assembly of a series of PFS-b-polyvinylsiloxane copolymers (PFS = polyferrocenylsilane). This simple crystalline-coil block copolymer (BCP), containing a PFS block suitable for crystallisation-driven self-assembly (CDSA) and a siloxane block suitable for the introduction of molecular complexity, is an ideal starting point for the bottom-up preparation of functional nanostructures. Chapter 2 outlines enabling chemistry that provides a platform for the majority of the work in this Thesis. It describes the preparation of PFS-b-polyvinylsiloxane copolymers and their subsequent functionalisation to tune the properties of the resulting materials or incorporate more complex functionality for subsequent applications. Chapter 3 describes the CDSA of brush BCPs prepared by the thiol-ene functionalisation of poly( ferrocenyldimethylsilane )-b-poly(methylviny lsiloxane) (PFDMS-b-PMVS) with n-alkane thiols. The rate of CDSA is influenced by the cocrystallisation of brush and linear BCPs and can be manipulated to afford micelles with nanosegregated coronas by gradient CDSA, an analogous process to a covalent gradient copolymerisation. Chapter 4 describes the immobilisation of red, green and blue emitting fluorophores on PFDMS-b-polysiloxane copolymers. By the sequential CDSA of fluorescent BCPs, or mixtures thereof, multicompartment micelles are prepared in which the emission of each segment is precisely controlled to produce colours throughout the visible spectrum and prepare structures analogous to nanoscale pixels and barcodes. Chapter 5 describes the radical hydrophosphination and CDSA of PFDMS-b-PMVS to afford monodisperse cylindrical micelles. On addition of a Pd precursor, · intermicelle crosslinking occurs affording tunable Pd-coated fibres that remain active to further CDSA. FUl1hermore, chains and networks can be prepared by the coordination-driven self-assembly of multicompartment micelle building blocks. Chapter 6 describes future directions and preliminary results for the use of crystalline-coil BCPs, where creativity and control at the small molecule scale is desirable for the transfer of complexity through hierarchical self-assembly processes for the optimisation of end nanostructure function.
24

Very strongly σ-donating carbenes and pseudo-amides based on benzo[c]quinolizine : synthesis, properties and use as ligands

Murphy, Elliot Anthony January 2014 (has links)
Following DFT calculations, the structure of a new, remotely stabilised, N-heterocyclic carbene, thought to be very strongly a-donating, was proposed. This structure was benzo[c]quinolizin-6-ylidene. Synthesis of the basic scaffold of the benzo[c]quinolizine ring system was performed, giving benzo[c]quinolizin-6-one (2.3a). Several novel 5 and 7 substituted varieties (2.3b-e) were also synthesised, requiring the development of a new route, due to the failure of the initial coupling step when using substituted substrates.
25

Synthesis of mycobacterial cord factors and related compounds

Hameed, Rwoaa Tarq January 2014 (has links)
Mycolic acids and their trehalose esters are very important components of mycobacterial cells. They show many biological effects and can be used to detect infection by diseases such as tuberculosis. In this project, a variety of novel trehalose esters of mycolic acids (TDM and TMM) were synthesised for use as antigens and to study their effects on the immune system. The project which the thesis describes consisted of five parts: In the first part, a series of six novel cord factors were prepared by coupling synthetic keto, hydroxyl- and methoxy-mycolic acids containing both cis- and trans-cyclopropanes with protected trehalose. These compounds were synthesised in order to ascertain their efficacy as antigens in ELISA assays to detect active TB in serum samples. These assays showed that trehalose dimycolate A provided a better distinction than natural TDM from Mycobacterium tuberculosis Preliminary results show that some of these compounds also strongly stimulate the production of TNFα, IL-6 and IL-lβ in cell line assays. The second part comprised the synthesis of saturated β-hydroxy acids, models for mycolic acids, without cyclopropane and functional groups, thereby completing the preparation of three saturated cord factors. The third part involved the preparation of four trehalose esters from simple fatty acids. The fourth part involved the synthesis of a novel α-methyl-trans-alkene keto-mycolic acid present in M tuberculosis and in other mycobacteria.
26

Cycloaddition reactions of conjugated trienes

Beels, Christopher Michael Donald January 1970 (has links)
No description available.
27

Mechanisms for catalysis acetal hydrolysis

Craze, Gabrielle-Anne January 1976 (has links)
No description available.
28

Chelating ditertiary phosphine complexes of iron

Bellerby, John Murray January 1972 (has links)
No description available.
29

Novel cyanate ester blends

Crawford, Alasdair January 2014 (has links)
This research focuses on novel polymeric blends containing cyanate esters, a high performance thermoset known for its thermal stability, low moisture uptake and excellent electrical performance. Cyanate esters have found application in numerous areas where performance in extreme environments is required. Aerospace, medicine, energy production and high powered computing are just a selection of industries that exploit the idiosyncratic properties held by cyanate esters, yet for the continued development and advancement of technology, improvements are consistently sought after. The overall aim of this research is to develop blends that build on and improve upon the already high performance properties held by cyanate ester homopolymers. A systematic approach has been adopted that goes about achieving this aim; firstly the blending of binary cyanate polymers has been investigated to produce a set of novel blends with reaction kinetics and thermo-mechanical performance a main area of investigation. The research has looked for improvements in hot/wet performance with the role of catalysis and heating rates studied. Moisture absorption experiments through both elevated humidity and direct immersion tests have yielded data that provide an insight into the mode of water uptake in binary cyanate ester blends. With a reduction in outgassing observed for one binary blend [(3)90(2)10] which is a major improvement upon the typical outgassing observed for either homopolymer. Following the initial studies of binary cyanate ester blends, the research focusses on blends between cyanate ester and another high performance polymer, bismaleimide. BT resins have been analysed for their reaction mechanism and novel materials produced displaying excellent thermo-mechanical properties. In parallel to empirical studies computational modelling has been performed in two methods ultimately producing accurate predictions of the main thermal transitions of Tg and Td for novel blends as well as accurately simulating degree of moisture uptake.
30

The photoreactions of conjugated nitroalkenes in dilute solution

Cridland, John Stephen January 1970 (has links)
No description available.

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