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Teses / dissertações sobre o tema "Heterocycles"

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Publicado: 4 de junho de 2021
Última modificação: 9 de novembro de 2024

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1

Locke, Julie Myree, University of Western Sydney, College of Health and Science e School of Biomedical and Health Sciences. "Synthetic and conformational studies of hexahydropyrimidines and related heterocycles". THESIS_CHS_BHS_Locke_J.xml, 2003. http://handle.uws.edu.au:8081/1959.7/638.

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This thesis explores the synthesis and conformational behaviour of hexahydropyrimidines and related heterocycles, with particular emphasis on 5- hyrdohexahydropyrimidines. The conformational behaviour of these compounds was investigated using dynamic NMR spectroscopy, molecular modelling techniques and X-ray crystal structure analysis. The conformational behaviour of 5- hyrdohexahydropyrimidine, hexahydropyrimidine and their analogous oxygen compounds as well as a series of hexahydropyrimidines with various exocyclic substituents, were examined. The preferred conformations of all these compounds are attenuated by a combination of steric and electronic influences. These influences include intramolecular hydrogen bonding as well as anomeric and gauche interactions. The conformational behaviour of the selected seven membered benzodiazepine rings, which share structural characteristics with the six-membered 5- hyrdohexahydropyrimidines was also explored. The increased flexibility of the seven membered rings facilitates intramolecular hydrogen bonding, which in turn retards ring inversion in these systems
Doctor of Philosophy (PhD)
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2

Sheldrake, Paul J. "Complexed heterocycles". Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386622.

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3

Locke, Julie Myree. "Synthetic and conformational studies of hexahydropyrimidines and related heterocycles". Thesis, View thesis, 2003. http://handle.uws.edu.au:8081/1959.7/638.

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This thesis explores the synthesis and conformational behaviour of hexahydropyrimidines and related heterocycles, with particular emphasis on 5- hyrdohexahydropyrimidines. The conformational behaviour of these compounds was investigated using dynamic NMR spectroscopy, molecular modelling techniques and X-ray crystal structure analysis. The conformational behaviour of 5- hyrdohexahydropyrimidine, hexahydropyrimidine and their analogous oxygen compounds as well as a series of hexahydropyrimidines with various exocyclic substituents, were examined. The preferred conformations of all these compounds are attenuated by a combination of steric and electronic influences. These influences include intramolecular hydrogen bonding as well as anomeric and gauche interactions. The conformational behaviour of the selected seven membered benzodiazepine rings, which share structural characteristics with the six-membered 5- hyrdohexahydropyrimidines was also explored. The increased flexibility of the seven membered rings facilitates intramolecular hydrogen bonding, which in turn retards ring inversion in these systems
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4

Hemmings, Philippa Rachel. "Nitrogen heterocycles from sugars". Thesis, University of Oxford, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314823.

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5

Bedford, Simon Bernard. "Synthesis of oxygen heterocycles". Thesis, University of Nottingham, 1993. http://eprints.nottingham.ac.uk/13159/.

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In chapter one, the various methods of generating benzenoid orthoquinodimethanes are discussed and approaches to their heterocyclic analogues are also reviewed. The utility of ortho-quinodimethanes in organic synthesis is highlighted by examples of both inter- and intramolecular Diels-Alder cycloadditions as the key steps in the total synthesis of naturally occurring polycyclic systems. In chapter two, work aimed at the development of a rapid synthetic entry to heterocyclic quinodimethanes starting from ortho-methyl heterocyclic carboxylic acids is presented. To this end, the dianion of 3-methylbenzofuran-2-carboxylic acid (018) was used to facilitate the construction of a "benzylsilane type" precursor (038) which in turn when treated with fluoride base, resulted in the generation of benzofuran-2,3-quinodimethane (012). We were then successful in trapping this intermediate with reactive dienophiles to form a series of the corresponding tetrahydrodibenzofurans (042 to 049). We have been able, for the first time, to determine the regioselectivity in this reaction by performing an X-ray crystallographic analysis on the major isomer (046) arising from cyclization with methylvinylketone. Preliminary work on an intramolecular variant as well as other heterocyclic acids is also presented. Chapter three, deals with the extensive modern approaches to tetrahydrofurans, but concentrates on examples that exhibit 2,5-disubstitution. It is sub-divided into the methods which involve an electrophile induced cyclization and the numerous alternative ones which do not. Their relevance in Natural Product assembly, especially the polyether antibiotics, is appraised. Chapter four continues with studies which have already established that Z-3-silyloxy-5-alkenoic acids undergo efficient and highly stereoselective iodolactonizations leading to the Mevinic analogues and related valerolactones. We have now established that the iodolactonizations of Z- and E-3-silyloxy-5-alkenoic acids (174 and 131) both lead to trans-disubstituted valerolactones, which differ only in the stereochemistry of the iodine substituent (175 and 178). The possibilities of effecting etherifications of the related Z-3-hydroxy-5- alkenoates (106) are then examined. By simply blocking the carboxylate end of the hydroxy-5-alkenoic acids involved in the above reactions it was found that under iodolactonization conditions a novel iodoetherification-hydroxylation process ensues which leads to 3-hydroxy-2,5-disubstituted tetrahydrofurans of which (182) is an example. These products were essentially single diastereoisomers according to all their spectroscopic data indicating that a well defined transition state must be involved in these cyclizations. Extensive work was then conducted in probing the mechanism of this reaction which required developing several complementary routes to various homoallylic alcohol precursors. Indeed, results thus generated suggest that the more expected iodotetrahydrofuran (183) is not an intermediate and neither is the plausible epoxide (201). A strong link with hydroxytetrahydrofuran formation and the amount of water present in the reaction was established. That the ester group plays a key role in the cyclization was evident from the observation that its repositioning (135) or removal (137) gave only iodo-diols (204-5 and 221-2) which failed to cyclize further. Similar cyclizations of the corresponding E-isomers gave iodotetrahydrofurans (199) in excellent yield. In each case, the cyclization was reasonably stereoselective with a modest improvement in yields being obtained in anhydrous solvents. However, under a variety of conditions, these did not lead to hydroxytetrahydrofurans. lodoetherification of simpler Z - and E-3-hydroxy-5-alkenes proceeded efficiently with high levels of stereoselection by a 5-endo-trig process and gave iodotetrahydrofurans, but only when anhydrous acetonitrile was used as solvent. The E-alk-5-en-ols gave a stereoselective reaction and the Z-isomers showed poorer selectivity. In semi-aqueous conditions iodo-diols and not hydroxytetrahydrofurans were obtained. Displacements on the iodotetrahydrofurans with azide (240) and hydroxide (243) equivalents have also been demonstrated in which the inverted products are obtained in good yield as single isomers. The relevance of all these tetrahydrofurans in Natural Product assembly is then emphasized by a few specific examples.
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6

Slater, Jonathan. "Cyclometallated nitrogen heterocycles - metallomesogens". Thesis, University of Warwick, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269196.

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7

Yow, Shu Hui. "Claisen rearrangements of heterocycles". Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/9491.

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This thesis is divided into five chapters. Chapter 1 is a review of de-aromatisation processes achieved by sigmatropic rearrangement. It covers the two main types of sigmatropic rearrangements, namely [2,3]- and [3,3]-rearrangement. Chapter 2 introduces the decarboxylative Claisen rearrangement (dCr) reaction and the aim to investigate its viability on more elaborate heterocyclic substrates is discussed. Research efforts into the synthesis of 3-sulfonyl-6-alkenyl-1,4-dioxan-2-ones are detailed. Chapter 3 discusses the extension of this methodology towards N-alkylmorpholinones. The first section examines 5,6-divinyl cis-morpholinones and L-alanine-derived trans-morpholinones as Claisen precursors, whereby stereospecific Ireland–Claisen rearrangement of L-alanine-derived trans-morpholinones was achieved. The second section details the synthesis of a novel L-proline-derived bicyclic morpholinone. However, attempted rearrangement led to degradation of product instead. The third section details the synthesis of 6-thienyl and 6-furanyl morpholinones, along with attempted Ireland–Claisen rearrangements and dCr reactions. Chapter 4 describes research efforts into the de-aromatising sigmatropic rearrangement of azide- and phthalimide-containing thienyl acyclic precursors. dCr Reaction of a cyanoacetate-containing substrate followed by unprecedented cyclisation led to the formation a highly-conjugated tetracycle and the mechanism of its formation is discussed. Chapter 5 provides experimental procedures and characterisation data.
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8

Hollis, Stephen James. "Heterocycles in peptide chemistry". Thesis, Open University, 2000. http://oro.open.ac.uk/54180/.

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The synthesis of 5-membered heterocyclic rings that bear both amine and carboxylic acid functional groups has been investigated using a 1,3-dipolar cycloaddition reaction strategy. These molecules, on incorporation into a chain of amino acids, have the potential to restrict the conformational freedom of the peptide. Cycloaddition of a nitrile oxide, derived from a Boc-protected naturally-occurring a-amino acid, with a pyrrolidine en amine led to a Boc-protected 3-aminoalkylisoxazole amino acid ester. The nitrogen and carbon termini of this isoxazole were coupled to other a-amino acids. Analysis of the dipeptide from coupling to (S)-alanine indicated that the integrity of the chiral centre of the isoxazole had been retained during the synthesis. Molecular modelling of a tripeptide unit incorporating the isoxazole showed that the presence of the ring had, as intended, restricted the conformational freedom of the molecule. Analogous cycloadditions using azomethine imines as the dipole yielded the corresponding tetrahydropyrazoles (pyrazolidines). These dipoles were generated by reaction of an aldehyde with a 1,2-disubstituted hydrazine, followed by elimination of the elements of water from the resulting aminol. Reaction with a dipolarophile bearing an electron withdrawing substituent gave predominantly the 4-substituted pyrazolidine. A study of the scope of the reaction found that, although the required carboxylic acid group could easily be incorporated by use of methyl acrylate as the dipolarophile, it proved impossible to attach an amine group to the ring using this methodology. However, by using one of the nitrogen atoms in the ring as the N-terminus, two pyrazolidines with protected amine and carboxylic acid groups were prepared, and these can be thought of as conformationally restricted B-amino acids.
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9

Waterfield, P. C. "Novel C-organostannyl heterocycles". Thesis, University of Bath, 1988. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384138.

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10

Esteves, Carlos Henrique Alves. "Palladium-catalysed enolate arylation in the synthesis of aromatic heterocycles and substituted heterocycles". Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:b69e1a46-3275-4d77-a043-7207e7c93d59.

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Chapter 1. Introduction A literature background on the early development of the Pd-catalysed cross-coupling reactions and the later discovery of the enolate arylation reaction is presented. In the second part, the literature on pyruvate chemistry is explored, focusing on enantioselective transformations and the synthesis of α-arylated pyruvate derivatives. The final part presents reported protocols on the synthesis of β-carboline, isoquinoline and indole esters, from the classical approaches to the more recent methodologies based on metal catalysed transformations. Chapter 2. Results and Discussion 2.1 A study towards the synthesis of substituted amino-pyridines via 6π-electrocyclisation of 1-azatrienes is presented. The aspects impacting the efficiency of the cyclisation reaction are discussed using the experimental data collected and kinetic experiments published by other groups. 2.2 A synthetic methodology for the synthesis of substituted β-carbolines from 3-bromoindoles and commercially available ketones via Pd-catalysed enolate arylation is discussed. The α-functionalisation of the keto-indole intermediate with electrophiles provided access to C4-functionalised β-carbolines. The one-pot protocol for this sequence was also developed. 2.3 A protected pyruvate equivalent that allows the α-arylation and α-arylation/alkylation reactions to be carried out at the methyl group via Pd-catalysed enolate arylation is presented. The deprotection of the OBO moiety allows the formation mono and multiply α-functionalised pyruvates. 2.4 The synthesis of isoquinoline, β-carboline and indole esters via Pd-catalysed enolate arylation of the OBO-protected pyruvate equivalent developed in this thesis is demonstrated. The functionalisation of these heterocycles via α-alkylation of the aryl-ketone intermediates is also discussed and some examples synthesised to validate the methodology.
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11

Reddy, Y. S. V. "Enantioselective construction of six - membered heterocycles and carbocycles using N - heterocyclic carbene (NHC) - organocatalysis". Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 2016. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/2079.

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12

Fletcher, Kristin A. "Mobile Order Theory as Applied to Polycyclic Aromatic Heterocycles". Thesis, University of North Texas, 1997. https://digital.library.unt.edu/ark:/67531/metadc278994/.

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Experimental mole fraction solubilities of benzil, thianthrene, trans-stilbene, thioxanthen-9-one, diphenyl sulfone and dibenzothiophene sulfone are determined in pure noncomplexing and complexing solvents. Predicted solubility values are calculated for benzil, thianthrene, trans-stilbene and thioxanthen-9-one using expressions derived from Mobile Order theory. Large deviations between experimental and predicted solubilities in alcohol solvents exist, therefore optimized solute - solvent association constants are determined. Previously measured thianthrene solubilities in five binary alkane + cyclohexane solvent mixtures are compared with values predicted from Mobile Order theory using the measured solubility in each of the pure solvents as input parameters. The experimental mole fraction solubility of benzil in eight binary alcohol + 1-octanol solvent mixtures are also measured and compared with predicted values.
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13

Dunford, Damian Gordon. "Novel synthesis of N-heterocycles". Thesis, Cardiff University, 2010. http://orca.cf.ac.uk/54138/.

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In a continuation of studies into metal-catalysed 5-endo-dig cyclisations, we investigated their application to the synthesis of a range of N-heterocycles: indoles, pyrazoles and pyrroles. The second chapter describes an investigation of the application of silver(I) cyclisation methodology to the synthesis of 1,2-disubstituted indoles. Our methodology was applicable to a range of functional groups in both positions, allowing for terpenes, alkenes, aromatic, alkyl and alcohol substituents in position two. Additionally, a range of nitrogen protecting groups were tolerated, including sulfonamides, carbamates, amides and even methyl groups. A few substrates would not cyclise; we propose that the current hypothesis that this is due to pKa differences is insufficient to explain the differing reactivities. This is supported by computational work carried out by a collaborator. Also reported is a successful synthesis of an indole in a flow system; this was achieved using silver nitrate on silica as the stationary phase. Chapter three focuses on the synthesis of pyrazoles from hydrazines prepared using the Mitsunobu alkylation. A regioselective Mitsunobu alkylation has been defined using non-symmetrical disubstituted hydrazines to give a single regioisomer. Exposure of these hydrazines to silver(I) met with limited success with steric hindrance believed to be the explanation as to why some for the hydrazines would not cyclise. Chapter four reports the synthesis of pyrroles using silver(I) and copper(II). The first part focuses on the improvement of Sharland's copper(I)-catalysed pyrrole synthesis which, upon improvement, gave pyrroles cleanly in high yields. Also reported are the successful silver(I)-catalysed synthesis of fused pyrroles such as annulated pyrroles and N-fused pyrrolizines and indolizines by use of silver(I). Finally the silver(I) cyclisation methodology was applied to the successful synthesis of a natural product, pyrrolostatin.
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14

Richmond, Craig J. "Applications for imidazophenanthridine-based heterocycles". Thesis, University of Glasgow, 2009. http://theses.gla.ac.uk/1406/.

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The physical properties and reactivity of 2,3-dihydro-1H-imidazo[1,2-f]phenanthridinium cations (DIPs) and analogous heterocycles have been investigated. The adapted syntheses developed were applied to a range of aryl amines and more elaborate substrates, such as bifunctional aminoquinolinium cations and amino functionalised polyoxometalates (POMs). 1,2,3,12b-tetrahydroimidazo[1,2-f]phenanthridines (TIPs), an intermediate in the 3-step cascade synthesis of DIPs, have also been isolated. Derivatisation of the TIP structure at the imidazo-N position enables control of the reactivity of the intermediate with respect to electronic potential and pKa, allowing isolation of a selection of TIP structures. Correlations between these parameters and reaction outcome have been made and other influences such as steric and solvent effects have also been investigated. Investigation of the structure and properties of the TIP framework led to the discovery of a pH dependent cyclisation between the ring-closed TIP form and the ring-open aminoethylphenanthridinium (AEP) form. The complementary TIP and AEP forms can be further manipulated by oxidation or reduction to convert them to their “pH-inert” forms, DIP and aminoethyldihydrophenanthridine (AEDP). These four interchangeable states formed the basis of a redox “lockable” molecular switch that could be useful for molecular level information processing and data storage. The pH dependent cyclisation between the TIP and AEP forms was also investigated as a targeting mechanism for potential intercalating antitumour agents. The system looks to exploit the pH difference between cancerous tissues and normal tissue to combine high cytotoxicity with high selectivity, a desirable trait that is unfortunately absent in most chemotherapeutic agents. Preliminary in vitro assays have shown the TIP/AEP frameworks to have IC50 values in the pM range in human ovarian cancer cell lines, comparable to cisplatin and the closely related DIP intercalaters.
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15

Gosby, Katherine M. P. "Osmium mediated formation of heterocycles". Thesis, University of Oxford, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.496899.

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16

Pheko, Tshepo. "Stereoselective synthesis of oxygen heterocycles". Thesis, University of Bristol, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.658071.

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The thesis describes the use of y,8-unsaturated alcohol in cyclisations with various aldehydes under acidic conditions to fonn monocyclic and bicyclic heterocycles with good stereocontrol. 6-Phenylhex-5-en-2-01136 was prepared in 3 steps and 55% yield and reacted with prop anal ill the presence of oxygen· and nitrogen nucleophiles to give tri-substituted tetrahydropyrans. Interestingly 229 and 230 have an equatorial C-3 side chain whereas 232 and 235 is in axial. Furthennore reaction of 6-phenylhex-5-en-2-01 136 with aldehydes possessing aryl, nitrogen and oxygen tethered nucleophiles suitably positioned to attack the secondary carbocation giving a range of bicyclic and tricyclic scaffolds with different ring sizes in a single pot. In chapter 3, the use ofhomoallylic alcohol 329 for the synthesis of blepharocalyxin D analogues with differing substitution at the C-7 is discussed. Homoallylic alcohol 329 was reacted with electron deficient and electron rich aromatic aldehydes to give lactones which were subjected to a Grignard addition/reduction protocol to give bicyclic tetrahydropyrans.
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17

Treacy, Alan Bernard. "Nitrogen heterocycles in asymmetric synthesis". Thesis, Queen's University Belfast, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361310.

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18

Jones, A. D. "Novel syntheses of nitrogen heterocycles". Thesis, University of Nottingham, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388287.

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19

McGuigan, H. "Synthetic studies on nitrogen heterocycles". Thesis, University of Glasgow, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375469.

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20

McKnight, Michael Vincent. "Heterocycles as amine protecting groups". Thesis, University of Liverpool, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328176.

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21

Billington, Helen. "Novel approaches to polycyclic heterocycles". Thesis, University of Liverpool, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.272632.

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22

Wilson, Ian. "Halogenated heterocycles for drug discovery". Thesis, Durham University, 2011. http://etheses.dur.ac.uk/863/.

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Within a number of industries, and particularly within the pharmaceutical industry, there is a desire for reliable, high yielding routes towards large numbers of valuable small molecules that allow a wide range of products to be synthesised. Heterocyclic compounds are particularly sought after as useful compounds, with an estimated 70% of pharmaceutical products being based on heterocyclic structures. A drawback of many traditional routes towards heterocyclic compounds is that the range of substituents that may be placed around the ring is limited. This is especially limiting if ring substituents have to be placed early in a synthesis, reducing the opportunities for elaboration at a late stage. Our approach is to take highly halogenated heterocyclic systems and use them as scaffolds for the synthesis of novel compounds by the sequential replacement of halogen atoms with other functionalities. This approach has led to the generation of a number of novel highly substituted heterocyclic species.
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23

Burnett, Duane Arthur. "Synthesis of nitrogen containing heterocycles /". The Ohio State University, 1986. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487264603219377.

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24

Monzón, Díaz Gabriel Andrés. "Zincation of heterocycles and aryl nonaflates". Diss., lmu, 2012. http://nbn-resolving.de/urn:nbn:de:bvb:19-147520.

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25

Austin, Carolyn A. "Diversity-Based Synthesis of Nitrogen Heterocycles". Thesis, University of Glasgow, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.484942.

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Brief investigations were carried out towards the synthesis of 2,4-disubstituted quinolines and 2,6-disubstituted piperidines using titanium alkylidene chemistry, but these were unsuccessful. A route towards the diversity based stereoselective synthesis of 2-substituted azepane derivatives was explored via titanium alkylidene chemistry. Thioacetals i were reacted with low valent titanium(II) species ii to produce titanium(IV) alkylidenes that were reacted with resin-bound esters iii. Cleavage of the resulting enol ethers led to a small library of amino ketones iv, but reductive amination to give azepanes, remained elusive. However, hydrogenation of the a-phenylethylamino group in ketones iv gave racemic azepanes v. Diversity based synthesis of cyclic imines, both 6 and 7 membered, has been carried out using trityl protected amines vi and vii. Alkylidene formation followed by reaction with a range of resin-bound esters iii gave enol ethers. Cleavage and deprotection under mild acidic conditions followed by treatment with base cyclised aminoketone products to cyclic imines viii and ix.
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26

Agocs, Lisa Lynn. "Design of bioactive chalcogenobismuth(III) heterocycles". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq24728.pdf.

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27

Reeves, Jonathan Robert. "Alkene epoxidation using small ring heterocycles". Thesis, Imperial College London, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.397377.

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28

Jones, Matthew Lloyd. "Radical rearrangements of nitrogen-containing heterocycles". Thesis, University of Oxford, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289342.

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29

Anwar, Muhammad. "Synthesis of highly functionalised nitrogen heterocycles". Thesis, University of Oxford, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.441057.

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30

Orr, Allan J. "A metathesis approach to aromatic heterocycles". Thesis, University of Oxford, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.433342.

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31

Mujtaba, Nadeam. "Homochiral heterocycles from β-amino esters". Thesis, University of Oxford, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.418480.

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32

Honey, Mark A. "A carbenoid approach to functionalised heterocycles". Thesis, University of Nottingham, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.556078.

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This Thesis describes the development of methodology towards an array of functionalised heterocycles from metal-catalysed carbenoid X-H insertion reactions. Chapter 1 introduces the concept of carbenoid chemistry, with carbenoid N- H, O-H and S-H insertion reactions being reviewed. Chapter 2 discusses various methods available for the synthesis of a- diazocarbonyl compounds, with the results and discussion section detailing the synthesis of numerous diazo-containing compounds which will be used throughout this Thesis. The introduction of Chapter 3 details selected literature examples of indole syntheses, with the results and discussion section detailing synthesis of indoles via a modified Bischler indole approach. Chapter 4 summarises selected literature examples of benzofuran and benzothiophene syntheses, with the results and discussion sections detailing a one-pot synthesis of benzofurans from phenols, and the attempted synthesis of benzothiophenes from benzenethiols. Chapter 5 details previous syntheses of both pyrimidines and pyrazoles, with the results and discussion section describing the synthesis of common intermediates derived from metal-catalysed N-H insertion reactions. These intermediates are then successfully utilised in the synthesis of a range of functionalised pyrimidiones and pyrazolones. Efforts towards the synthesis of trifluoromethyl-substituted heterocycles are detailed within Chapter 6, in which novel rhodium-catalysed N-H insertion reactions of ethyl 2-diazo-4,4,4-trifluoro-3-oxobutanoate are described, with the isolation of novel N-H insertion products, as well as the formation of a range of thiazoles, oxazoles a l,2,4-triazole and a pyridine. This Thesis concludes with specific details of experimental procedures and full characterisation data for compounds synthesised throughout the results and discussion sections of this Thesis.
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33

Lindsay-Scott, Peter J. "New osmium-catalysed routes to heterocycles". Thesis, University of Oxford, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.509979.

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34

Davies, Deiniol Hedd. "Synthesis and applications of Guanidine Heterocycles". Thesis, Bangor University, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.519556.

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35

Mann, Emma. "Novel free radical synthesis of heterocycles". Thesis, Loughborough University, 2001. https://dspace.lboro.ac.uk/2134/14589.

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The use of tri-n-butyltin hydride and an initiator to mediate free radical cyclisation as a synthetic organic process is well documented throughout the chemical literature. By using BU3SnH, and developing new 'catalytic' BU3SnH methods, many new heterocyclic compounds have been synthesised successfully. The search for new 'tin-free' radical reagents is important in order to provide a non-toxic alternative to tin. We have started initial studies on the replacement oftriorganotin hydrides with germanium analogues. An interesting number of reactions using BU3SnH do not give reduced products and have an oxidation step in the mechanism. These BU3SnH mediated cyclisations provide a useful synthetic method. Our studies were aimed at developing the synthetic protocol as well as determining the mechanism. 'Shilajit' is an ancient tribal panacea, believed to have many advantageous biological properties. The active constituents are based upon a benzochromenone skeleton. The key component of the natural product Shilajit, 3-methoxy-6H-benzo[c]chromen-6-one, as well as several analogues have been synthesised using this BU3SnH mediated 'oxidative' free radical approach. The mechanism proposed for these reactions by Bowman et ai, the pseudo SRN I mechanism, has also been studied in order to try to determine the presence of the radical anion intermediates which are essential for the pseudo SRN 1 mechanism to be correct. The BU3SnH mediated 'oxidative' cyclisation protocol was successfully applied to electron deficient pyrroles, i.e. pyrroles with electron withdrawing substituents. Radicals generated on N-substituted chains readily undergo cyclisation onto the pyrrole ring. The protocol was also applied to cyclisation reactions of analogous imidazoles. The imidazole reactions were used for an extensive examination of the mechanism of the 'oxidative' BU3SnH protocol. The studies have disproved the pseudo SRN 1 mechanism (where BU3SnH is the oxidising agent) and suggest possible alternative oxidising agents. The importance of the functionality on the heterocyclic ring is also emphasised. Free radicals have been generated using photolytic methods, and the results are contrasted with those from traditional BU3SnH reactions. The synthesis of several substituted pyrazoles and radical cyclisation reactions were attempted on various pyrazole systems with the aim of synthesising the natural product withasomnine.
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36

Benmansour, Hadjar. "Palladium catalysed reactions of halogenated heterocycles". Thesis, Durham University, 2001. http://etheses.dur.ac.uk/4948/.

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1- The synthesis of unusually substituted halo-fluoroheterocycles has been achieved. 2,4,6-Tribromo-3,5-difluoropyridine and 4-bromo-2,3,5,6-tetrafluoropyridine were prepared from pentafluoropyridine, aluminium bromide and hydrogen bromide Reactions with lithium halides allowed the preparation of 4-iodo-2,3,5,6- tetrafluoropyridine, 4-iodo-2,6-dibromo-3,5-difluoropyridine, 4-iodo-2,3,5,6- tetrafluoropyridine and 4-chloro-2,6-dibromo-3,5-difluoropyridine.2- Reactions of 2,4,6-tribromo-3, 5-difluoropyridine with nucleophiles showed that selective substitution at the C-F centre can be achieved using hard (sodium ethoxide, phenoxide) nucleophiles.3- Lithium mediated reactions of 2,4,6-tribromo-3,5-difluoropyridine allowed selective functionalisation of the 4-position; lithium-halogen exchange occurred exclusively at this position giving a stable lithium derivative, which was successfully trapped with a range of electrophiles (trimethylsilyl chloride, acid chlorides).4- Palladium mediated couplings of 2,4,6-tribromo-3,5-difluoropyridine with a range of substituted phenylacetylenes was successful and the 2- and 6-positions were the most activated sites. Coupling with boronic acids gave the disubstituted or trisubstituted products; in the case of trisubstitution, all three positions (2-,4- and 6-) were activated towards coupling. 2,4,6-Tribromo-3,5-difluoropyridine formed a stable zinc derivative, which was coupled with iodoaromatics (iodobenzene, diiodobenzene).
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37

Coates, Brian. "The stereoselective synthesis of nitrogen heterocycles". Thesis, Queen's University Belfast, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334524.

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38

Simpson, Bryan Garth. "Reactions of heterocycles with phosphorus compounds". Thesis, Cardiff University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329647.

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39

Canfield, Lesley Mary. "Microbiological transformations of partially reduced heterocycles". Thesis, University of Portsmouth, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358921.

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40

Barker, S. J. "Nitrogen heterocycles by flash vacuum pyrolysis". Thesis, University of Liverpool, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383390.

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41

Hicks, Simon Richard John. "Synthesis and reactions of epoxy heterocycles". Thesis, University of Hertfordshire, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365978.

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42

Kemp, Mark Ian. "Zirconocene mediated synthesis of nitrogen heterocycles". Thesis, University of Southampton, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242197.

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43

Hunter, Rupert Alexander. "Transition metal mediated synthesis of heterocycles". Thesis, University of Southampton, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.402426.

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44

Galan, A. A. "Novel routes to oxygen containing heterocycles". Thesis, University of Bristol, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375386.

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45

Wood, Paul Thomas. "Phosphorus-sulphur and phosphorus-selenium heterocycles". Thesis, Imperial College London, 1988. http://hdl.handle.net/10044/1/47312.

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46

Mahy, William. "Catalytic synthesis and modification of heterocycles". Thesis, University of Bath, 2016. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.687323.

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The following thesis outlines work carried out during the past three years for the discovery and investigation of catalytic methodologies towards the synthesis and modification of heterocycles, namely cyclic carbamates, carbonates and their sulfur analogues. Chapter 1 summarises the current catalytic methods reported in the literature towards the synthesis and modification of functionalized 2-oxazolidinones. This introduction highlights the diverse range of methods and catalysts that have been developed and their scope and limitations. In addition the review highlights the importance of these structural motifs and suggests areas in which the following research fulfills unmet needs. Chapter 2 reports the discovery and development of a one-pot two-step copper-catalysed methodology towards the synthesis of N-aryl oxazolidinones from amino alcohol carbamates. The scope of both the N-aryl substituent as well as oxazolidinone functionalization is presented in addition to preliminary investigations into the mechanisms of both reactions. Chapter 3 presents the application of the previously reported one-pot process towards the synthesis of a number of medicinally active molecules and blockbuster pharmaceuticals. The one-pot two-step copper-catalysed reaction was utilized to synthesise a common intermediate in the synthesis of a number of oxazolidinone-based pharmaceuticals. The complete syntheses of Toloxatone, Linezolid, Tedizolid and Rivaroxaban are reported. Chapter 4 reports the modification of N-aryl oxazolidinones towards a diverse library of N-aryl oxazolidinethiones. The reactivity of these structures, in addition to N-alkyl oxazolidinethiones, towards transition metal catalysis was investigated and revealed a ruthenium catalysed O- to S-alkyl migration to afford structurally diverse thiazolidinones. Investigations into the substrate scope and mechanism were also carried out, suggesting a pseudo-reversible radical pathway drawing mechanistic parallels to the classic Barton-McCombie reaction. Chapter 5 details further development of the pseudo-reversible radical pathway for the regioselective rearrangement of dioxolane-2-thiones using Pd(PPh3)4 as a catalyst. The scope of the reaction is reported for the formation of highly selective, highly substituted sulfur-rearrangement products.
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47

Ducept, Pascal. "Synthesis of heterocycles using silyldiazocarbonyl compounds". Thesis, Imperial College London, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271307.

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48

Wieting, Joshua Merlin. "Silanediol-Catalyzed Stereoselective Functionalization of Heterocycles". The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1448891366.

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49

Yoshioka-Tarver, Megumi. "Benzotriazole intermediates for heterocycles and pharmaceuticals". [Gainesville, Fla.] : University of Florida, 2009. http://purl.fcla.edu/fcla/etd/UFE0041025.

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50

Bloxham, Jason. "The synthesis of novel linked heterocycles". Thesis, Loughborough University, 1996. https://dspace.lboro.ac.uk/2134/10441.

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Chapter 1 reviews the literature with regard to the synthesiS of substituted carbazoles via the cycloaddition reactions of indole-2,3-quinodimethanes and its equivalents with dienophiles. Particular attention is paid to the synthesis and reactions of pyrano[3A-b ]indol-3-ones. Chapter 2 describes the synthesis of a variety of linked indole-3-acetic acid derivatives, where the linkage is either through the indole nitrogen, the 2- position or the acetic acid residue in the 3-position. The preparation and subsequent Diels-Alder reactions of the derived linked pyrano[3,4-b]indol-3-ones are also described. Chapter 3 investigates the possibility of forming a benzothiophene containing polymer via a novel double Diels-Alder reaction. The preparation of thieno[2,3- c]pyran-3-ones and their transformation into benzothiophenes are described. Chapter 4 briefly discusses the relevance of molecular recognition to a variety of fields and introduces the idea of folded and stretched conformations in non-rigid systems. The work described concentrates on the solid state structures obtained for a variety of simple linked heterocycles.
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