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Dissertations / Theses on the topic 'Cyclisation'

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Published: 4 June 2021
Last updated: 25 May 2024

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1

Sukirthalingam, Sukanthini. "Palladium catalysed cyclisation processes." Thesis, Queen's University Belfast, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335444.

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2

Chakraborty, Reena. "Cyclisation using bifunctional silanes." Thesis, University of Nottingham, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335197.

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3

Wilmshurst, Martin Philip. "Fluoroalkyl radical cyclisation reactions." Thesis, University College London (University of London), 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286192.

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4

Bird, Andrew James. "Zirconium-mediated cyclisation reactions." Thesis, University of York, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319766.

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5

Sykes, Bridget Maree. "Reductively triggered internal cyclisation reactions." Thesis, University of Auckland, 1994. http://hdl.handle.net/2292/1977.

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Reductively triggered internal cyclisation reactions have been investigated as a prodrug system for the hypoxia selective release of aromatic nitrogen mustards. The observed pseudo-first-order rate coefficients of cyclisation of several model 2-aminoaryl-acetamides and propanamides have been measured. Cyclisation was observed to be strongly influenced by stereochemistry, whereas electron withdrawal from the amine-bearing ring resulted in a comparatively modest slowing of the rate of cyclisation. Protonation of the leaving group appeared to increase the rate of cyclisation, while changes in 4-substitution on the leaving amine had little effect on this rate. The cyclisation of 2-(2-aminophenyl) alkanamides was found to be subject to general catalysis by acidic buffer components, and rate determining formation of the tetrahedral intermediate has been proposed. Ring closure reactions of several 2-hydroxylaminophenylalkanamides have been studied by γ-radiolysis. HPLC methods have been developed for the separation of reduction and cyclisation products. Reduction stoichiometry implicates the hydroxylamine as the predominant reduction product of radiolysis of the 2-nitrophenylalkanamide precursors, which varied in the nature of substitution of the nitrobenzyl ring, 4-substitution of the leaving aniline, and overall geometry. Cyclisation via the hydroxylamino was observed to be significantly faster than that of its amino counterparts, and was similarly influenced by changes in geometry. The hydroxylamine undergoes a base catalysed, oxygen dependent reaction under aerobic conditions. This reaction did not appear to be influenced by the geometry of the compound. Substitution of the hydroxylamine-bearing ring with a carboxamide group (CONHR σp = 0.36) lowered the pH at which hydroxylamino-amide cyclisation was slowest, compared with its unsubstituted counterpart. The reaction was found to be aided by electron-withdrawal from the leaving amine. Rate determining breakdown of the tetrahedral intermediate has been proposed. Preliminary investigations have been made on 2-nitrophenyl alkyl esters and a 2,6-dinitrophenylamide prodrug system. Rapid, reductively triggered release of coupled phenols and amines has been observed from the nitro-esters and -amides, respectively. In contrast to amino-amide and hydroxylamino-amide cyclisation, gem-dimethyl substitution did not facilitate reductive release from the nitro-ester. The inability to measure the rates of reductive release in radiolysis solutions suggests that these reactions occur significantly faster than hydroxylamino-amide ring closure. Molecular mechanics calculations have been undertaken to investigate relationships between the geometry of 2-aminoarylalkanamides, and rates of cyclisation. The distance between, and angle of approach of the nucleophilic and electrophilic centres in the calculated minimum-energy conformer did not display a correlation with cyclisation rates.
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6

Nilsson, Paul Andrew. "Radical cyclisation reactions of carbonyls." Thesis, Brunel University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.270101.

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7

Pilling, Adam Wesley. "Site Isolation in Cyclisation Cascades." Thesis, University of Manchester, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.492762.

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This thesis concerns the exploitation of the site isolation concept in cascade sequences that facilitate rapid construction of complex polycyclic molecules. Site isolation is the anchoring of mutually destructive reagents onto solid supports to prevent their mutual deactivation.
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8

Nodes, William. "Novel intramolecular organocatalytic cyclisation reactions." Thesis, University of Reading, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.541961.

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9

Young, Adrian R. "Free radical cyclisation of imines." Thesis, Loughborough University, 1996. https://dspace.lboro.ac.uk/2134/15357.

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Introduction. The free radical cyclisation reaction onto an unsaturated bond is a well known synthetic pathway, where a wide range of cyclic compounds can be produced form acyclic starting materials. Up until recent years, free radical addition to multiple bonds other than carbon-carbon had been little studied. Nowadays there is much information available of radical addition to carbonyl, thiocarbonyl, nitrile and oxime ether (C=NOR) functional groups. However there has been surprisingly little detailed study of similar reactions involving imines (C=NR) or hydrazones (C=NNHR). Monocyclisation. In the early phase of the research, different types of imine were synthesised and subjected to the standard free radical cyclisation procedure (tributyl-tin hydride / AIBN, added by syringe pump to refluxing solvent) to determination of the regiochemistry of cyclisation onto imines and to assess the synthetic potential of the reaction. The results of this investigative study show that a variety of five and six-membered ring compounds can be synthesised in good yield. A similar study of hydrazones showed that fivemembered rings can be formed under the same reaction conditions. Tandem Reactions. In the next phase, the aim was to extend the methodology to produce more complex structures from acyclic starting materials. If a radical adds to the carbon atom of an imine, a nitrogen-centred (aminyl) radical is generated which can undergo subsequent addition to a suitably positioned double bond to yield a bicyclic amine. This type of reaction is known as tandem or cascade cyclisation. By this method, compounds could be synthesised which have similar structures to natural products. A range of suitably designed imines wct.5. prepared and underwent cyclisation, producing many different types of bicyclic amine in yields varying from moderate to good. The Synthesis of Natural Products. After the successful formation of key bicyclic structures, the third phase of the research aimed at the synthesis of one or more of target natural products. The synthetic strategy used in the tandem reactions outline above was. adapted for these purposes. However the synthesis of the desired compounds could not be achieved in the time, but progress towards their formation was achieved.
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10

Cecil, Alexander Richard Liam. "Asymmetric oxidative cyclisation of dienes." Thesis, University of Southampton, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.402065.

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11

Owen, David Rodney. "Zirconocene mediated co-cyclisation reactions." Thesis, University of Southampton, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313216.

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12

Drayton, Sally Katherine. "Palladium-catalysed cyclisation of allylic esters." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358604.

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13

Murphy, Nicholas Patrick. "Radical aromatic cyclisation and substitution reactions." Thesis, University of Warwick, 2008. http://wrap.warwick.ac.uk/2286/.

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This dissertation is divided into five chapters. Chapter One consists of an introduction to radical cyclisation and rearrangement reactions. Chapter Two investigates the reactions of substituted arylsulfonamides 278a-l with copper bromide and an amine ligand-TPA. This reaction involves an alkyl radical generated from the copper (I) bromide/TPA complex, which can then undergo a 1,5- ipso attack onto the sulfonamide leading to a cyclohexadienyl radical intermediate. Re-aromatisation and extrusion of sulfur dioxide leads to an amidyl radical intermediate. This can undergo either cyclisation back onto the aromatic ring to give the 6-substituted oxindole 336, or reduction from H-atom abstraction by the solvent leading to rearranged amides. A minor product identified as a 5-substituted oxindole 333 may be formed from direct radical cyclisation onto the sulfonamide followed by extrusion of sulfur dioxide. An unambiguous synthesis of 333 was obtained through the Stollé method in order to rigorously identify this product. For completion, the rearranged amide 280e was also unambiguously synthesised from known literature sources. It has been shown that the selectivity towards either rearrangement or cyclisation is dependent upon the solvent used and temperature. For example, toluene induces excellent selectivity towards cyclisation (to furnish oxindoles), while using dichloromethane (DCM) induces a greater selectivity towards rearranged amides. Chapter Three explores the effects of varying the alkyl chain length on the nitrogen atom on selectivity, while keeping both the aryl group and initiator the same. It has been shown that selectivity towards the rearrangement (or decrease in cyclisation) occurred when the alkyl chain was increased from N-butyl to N-dodecyl. In addition a similar solvent effect on selectivity was observed as discussed in Chapter 3, notably relatively more rearranged amide was produced with DCM and oxindoles with toluene. Chapter four involves investigating the copper-mediated radical cyclisation of haloamides to give oxindoles directly. The final chapter consists of the experimental.
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14

Burns, Barry. "Palladium catalysed cyclisation anion capture process." Thesis, Queen's University Belfast, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334562.

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15

Rajviroongit, Shuleewan. "Cyclisation and cycloaddition of imine derivatives." Thesis, Queen's University Belfast, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335436.

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16

Gleasure, A. J. "Ruthenium and palladium catalysed cyclisation reactions." Thesis, Queen's University Belfast, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246436.

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17

Coulter, Thomas Stephen. "Combined cycloaddition - palladium catalysed cyclisation processes." Thesis, University of Leeds, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305704.

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18

Moore, Peter Robert. "Organic synthesis through radical cyclisation reactions." Thesis, University of Exeter, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337802.

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19

McLaughlin, Mark. "Studies on the Khand cyclisation reaction." Thesis, University of Strathclyde, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248357.

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20

Goodall, Karen. "A radical cyclisation approach to pyroglutamates." Thesis, University of York, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337153.

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21

Penfold, David John. "Novel radical and palladium cyclisation reactions." Thesis, University of Southampton, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266525.

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22

Avcil, Muhammet. "Investigation of novel thermal cyclisation reactions." Thesis, University of Sussex, 2013. http://sro.sussex.ac.uk/id/eprint/47138/.

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[For full abstract, with illustrations, see pdf file]. Part 1. Concise Synthesis of Highly Substituted Isoquinolin-1(2H)-ones via IMDA The primary goal of this DPhil research project was to further investigate the mechanism of a novel thermally activated cyclisation reaction discovered within the Parsons' research group. Through the synthesis and cyclisation of the substituted pyrrole rings 2.38a-c we have investigated the mechanism and increased the scope of the cyclisation reaction. We have also developed a robust route to advanced intermediate 2.10 in the synthesis of hymenialdisine 2.1. Part 2. Investigation and Development of a Novel Cascade Reaction The aim of this DPhil research project was to devise and execute a series of experiments to gain a better mechanistic understanding of the novel thermal cyclisation, discovered within the Parsons' research group. To further investigate the mechanism and scope of the cyclisation, the model system 2.1 was initially selected. Through extensive modification and manipulation of the cyclisation precursor 2.1, we have increased the scope of the cyclisation and postulated a reaction pathway. During these studies remarkable transformation of ketone 2.81 to alkyne 2.82 was also observed. The repeatability of the above reactions was also investigated by synthesising various analogues.
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23

Warner, Andrew. "Borylative cyclisation of alkynes using BCl3." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/borylative-cyclisation-of-alkynes-using-bcl3(7a4e56f3-e8c6-4c68-97ec-4596ef5e0ce2).html.

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Boron trichloride, a cheap and commercially available Lewis acid, has been demonstrated to activate alkynes possessing appropriate nucleophiles, facilitating borylative cyclisation. This reaction furnishes polycyclic compounds possessing a new C(sp2)-B bond externally to the newly formed ring (through concomitant C-C and C-B bond formation). The RBCl2 intermediates generated from cyclisation were esterified with pinacol to furnish air/moisture stable boronic esters. This methodology has been applied to the following classes of starting materials: 1,4-disubstituted but-1-ynes (including N- and O- linked analogues), 2-alkynylanisoles, 2-alkynylthioanisoles and 1,2-bis(alkynyl)benzenes. Thus, borylated scaffolds such as dihydronaphthalenes, dihydroquinolines, 2H-chromenes, benzofurans, benzothiophenes, dibenzopentalenes and benzofulvenes have been synthesised. A variety of functionalities (e.g. amines, esters, nitriles) were tolerated by the reaction, with a number of substrates cyclised on either a gram scale, or under ambient conditions, demonstrating the robust nature of this methodology. An oxidation reaction with [Ph3C][BF4] was carried out on some of the borylated dihydronaphthalene compounds to obtain borylated naphthalenes. Suzuki-Miyaura cross-coupling reactions were carried out on certain borylated cycles to furnish new C-C bonds and generate analogues of established pharmaceuticals such as Nafoxidine or Raloxifene, demonstrating the synthetic value of these borylated cycles. Additionally, a one-pot borylative cyclisation/Suzuki-Miyaura cross-coupling reaction was also developed. Throughout this investigation, alternative reactivity has been observed when using BCl3 to activate certain alkynes, including intermolecular 1,2-trans-carboboration and a rare example of N- and O-directed 1,2-trans-haloboration. Additionally, multiple borylative cyclisations have been carried out on an appropriate alkyne to obtain a B-doped polyaromatic hydrocarbon (PAH), which has potential material-based applications.
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24

BOUZIDE, ABDERRAHIM. "Nouvelles reactions de cyclisation des enamines." Paris 6, 1993. http://www.theses.fr/1993PA066321.

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Deux nouvelles reactions de cyclisation des enamines ont ete mises au point au cours de ce travail: 1) une reaction de cyclisation radicalaire oxydante induite par les sels de metaux; 2) une ene cyclisation thermique. Ces deux reactions appliquees aux beta-carboxamidoenamines secondaires ou tertiaires permettent d'obtenir en une etape le squelette de base de nombreux produits naturels; i) les enamines insaturees soumises a l'action de sels de metaux se transforment rapidement en produits azaspiraniques avec de bons rendements. Cette reaction appliquee a des beta-carboxamidoenamines ou des beta-enaminoesters satures conduit a la formation des 1-azadienes ou des derives aniliniques; ii) les memes enamines insaturees soumises a des temperatures relativement basses se convertissent aisement en produits azaspiraniques racemiques ou chiraux selon une aza-ene ou une carba-ene reaction avec d'excellent rendements chimiques et de bons rendements optiques
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25

Gregory, Alexander William. "Cyclisation cascades via reactive iminium intermediates." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:8e633fee-3457-4c31-939c-4421fac2fb8f.

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The aim of this D.Phil was to develop a range of cyclisation cascades, which initially form a reactive iminium intermediates that can then be attacked by a pendant nucleophile resulting in novel polycyclic structures. This concept has been applied to the development of three methodologies and has resulted in the discovery of new reactivity as well as the synthesis of a wide range of interesting novel structures Chapter 1: Enantioselective chiral-BINOL-phosphoric acid catalysed reaction cascade A highly enantioselective hydroamination / N-sulfonyliminium cyclisation cascade using a combination of Au(I) and chiral phosphoric acid catalysts has been developed. Proceeding by an initial 5-exo-dig hydroamination and a subsequent phosphoric acid catalysed Pictet- Spengler cyclisation, the reaction provides access to complex sulfonamide scaffolds in excellent yields and with high levels of enantiocontrol. The scope can be extended to lactam derivatives, with excellent yields and enantiomeric excesses of up to 93% ee. Chapter 2: Iridium catalysed nitro-Mannich cyclisation A new chemoselective reductive nitro-Mannich cyclisation reaction sequence of nitroalkyltethered lactams has been developed. An initial rapid and chemoselective iridium(I) catalysed reduction of lactams to the corresponding enamine is subsequently followed by intra molecular nitro-Mannich cyclisation. This methodology provides direct access to important alkaloid, natural product-like structures in yields up to 81% and in diastereoselectivities that are typically good to excellent. An in-depth understanding of the reaction mechanism has been gained through NMR studies and characterisation of reaction intermediates. The new methodology has been applied to the total synthesis of (±)-epi-epiquinamide in 4 steps. Chapter 3: Iridium catalysed reductive interrupted Pictet-Spengler cyclisation A novel reductive interrupted Pictet-Spengler cyclisation reaction cascade has been created. An iridium(I) catalyzed partial reduction of lactams/amides to the corresponding iminium is subsequently trapped by a pendant indole nucleophile. Interruption of the Pictet-Spengler reaction by indolium reduction provides a wide range of novel spirocyclic indoline moieties in excellent yield and diastereoselectivity.
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26

Outin, Johanne. "Synthèse de composés polycycliques azotés par cyclisation de Vilsmeier-Haack et cyclisation de Mannich organocatalysée en séquence." Thèse, Université de Sherbrooke, 2017. http://hdl.handle.net/11143/10979.

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Les recherches présentées dans cette thèse découlent de problématiques rencontrées lors de précédents travaux effectués dans notre groupe au sujet de cyclisations séquentielles de Vilsmeier-Haack et de Mannich par une activation chimiosélective d’amides. Deux limitations avaient été soulevées : une faible réactivité lors de la seconde cyclisation de Mannich et aucune possibilité d’obtention de produit de double cyclisation de façon énantiosélective. Au chapitre un, une étude de double cyclisation de Vilsmeier-Haack et de Mannich est présentée, tout d’abord sur des substrats allylsilane-aldéhyde puis vératrol-aldéhyde. Une étude mécanistique est détaillée dans le but d’améliorer le rendement de la réaction. Les bases de notre méthodologie avec l’aldéhyde sont établies dans ce premier chapitre. Au chapitre deux, une étude de double cyclisation de Vilsmeier-Haack et de Mannich en présence d’une cétone est exposée. Les conditions de première cyclisation sont rapidement déterminées tandis que pour la seconde étape, les divers paramètres pouvant influencer la réaction sont examinés. Aussi, une tentative de formation de centres quaternaires produisant des squelettes carbonés de type quinolizidine et spirocyclique est présentée, ainsi qu’une variation de tailles de cycles formés. Au chapitre trois, l’étendue de notre méthodologie est étudiée et celle-ci est appliquée sur divers substrats. Les nucléophiles de type indole, pyrrole, éther d’énol et allylsilane sont couverts et la variation de taille de cycle est également testée. Au chapitre quatre, une étude sur le développement catalytique et un effort vers une version non racémique de notre méthodologie sera présentée. Diverses amines secondaires chirales sont investiguées et les excès énantiomériques mesurés. Le chapitre cinq propose des suites au projet de thèse, incluant des pistes au sujet de l’induction asymétrique en s’appuyant sur des exemples concrets de la littérature.
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27

Pecheux, Muriel. "Cyclisation reactions mediated by sulfur-stabilised cations." Thesis, Imperial College London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.481499.

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28

El-Sayed, Nahed Nasser Eid. "Cyclisation desymmetrisation reactions of cyclohexa-1,4-dienes." Thesis, Cardiff University, 2006. http://orca.cf.ac.uk/56053/.

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This thesis describes different strategies to desymmetrise 1,4-cyclohexadiene derivatives with concomitant formation of a quaternary stereogenic centre. Chapter 1 gives a brief overview of the previous desymmetrisation and diastereotopic group selection processes of 1,4-cyclohexadiene derivatives. Chapter 2 describes the initial model studies for the formation of the quaternary stereogenic centre using achiral cyclohexa-1,4-dienone derivatives. This was developed to permit stereoselective formation of a quaternary stereogenic centre using a chiral sulfinyl group as the stereodirecting influence during the cyclisation step. This proceeded with acceptable levels of discrimination between the two diastereotopic double bonds. Chapter 3 outlines attempts to improve the level of diastereoselectivity obtained under the influence of the sulfinyl group by synthesising a range of different compounds having only carbon atoms in the tether. Chapter 4 describes the desymmetrisation of the two diastereotopic double bonds of derivatives of cyclohexa-1,4-diene using free-radical methodology. The sense and level of the diastereoselectivity is dependent on the protecting group used. Application of this methodology toward natural product synthesis has been described. Chapters 5 describes the desymmetrisation of the two diastereotopic double bonds of 1,4-cyclohexadiene derivatives using the Prins cyclisation reaction. This approach afforded an easy and stereocontrolled access to fused tetrahydropyrans and tetrahydrofurans depending on the reaction conditions employed. The stereochemical outcome of all of these reactions can be rationalised by a single transition state model.
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29

O'Neill, William. "New and novel cyclisation reactions of imidoylketenes." Thesis, University of Edinburgh, 2009. http://hdl.handle.net/1842/3124.

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The effect of scale on the conversion to products in flash vacuum pyrolysis experiments was studied using four model reactions. Overall, conversion was dependent on rection scale up to 0.5 g, but above 0.5 g, the effect was minimal and within experimental error. This effect was shown to be due to variations in contact time of the molecules in the furnace tube. Altering the furnace tube diameter had the effect of increasing the conversion to product. The pyrolysis of ortho-anilinomethylene Meldrum’s acid derivatives was investigated. Typically the 8-substituted quinolin-4-one was obtained as the major product, with a few exceptions. Certain substituents (such as nitro) were found to react with the ketene produced in the reaction to give alternative products, while others (such as chloro- and N-unsubstituted amides) gave the 3-substituted quinolin-4- ones via ipso-cyclisation and migration of the substituent. The regioselectivity of the pyrolysis of meta-anilinomethylene Meldrum’s acid derivatives, to give 5- and 7-substituted quinolin-4-ones, was studied. In general a 3:1 – 4:1 ratio of regioisomers was obtained, in favour of the 7-substituted quinolin-4-one. Substituents capable of hydrogen bonding, such as hydroxy-, were shown to give the 5-substituted quinolin-4-one exclusively and DFT calculations were employed to show that, in these examples, the 5-substituted product was favoured energetically. The pyrolysis of the methylene Meldrum’s acid derivative of 3-aminophenol gave 8-hydroxyquinolizinone as the sole product at low temperatures, with 5- hydroxyquinolinone as the major product formed at higher temperatures. The mechanism involves a regioselective electrocyclisation, followed by a hydrogen transfer and generation of a new ketene. Cyclisation of this ketene gives the quinolizinone. The scope of this reaction was explored, with a number of derivatives synthesised, and substitution on the aminophenol and the ketene generator was tolerated. The reactivity of the quinolizinones was also explored. The hydroxygroup was found to be phenol-like and underwent similar reactions, such as alkylations and acetylations. The compound was found to be highly reactive towards electrophiles, reacting in the 1- and 3- positions of the ring system, often in both positions. The pyrolysis of the aminomethylene Meldrum’s acid derivatives of certain pyridazinones was shown to give pyridopyrazidinediones. In some examples, a 4 second product based on a pyrrolopyridazine ring system was observed and DFT calculations show that the mechanism involves probably an electrocyclisation, followed by a decarboxylation reaction. Pyrolysis of amino acid ester derivatives of methylene Meldrum’s acid were shown to give N-unsubstituted 3-hydroxypyrroles and 1H-pyrrol-3(2H)-ones. Different amino acids were tolerated in the reaction, as were different electronwithdrawing groups in place of the amino acid ester. DFT calculations were employed to explore the mechanism of the reaction. 3-Hydroxypyrrole was also synthesised from the pyrolysis of Meldrum’s acid derivative of glycine tert-butyl ester, and the reactivity of the compound explored for the first time. The compound was found to be reactive towards electrophiles, such as diazonium salts, and could be O-acetylated under appropriate conditions.
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30

Yang, Ting. "Transition metal ion catalysed alkyne cyclisation reactions." Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.505491.

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31

Hughes, D. D. "The synthesis and oxidative cyclisation of lignans." Thesis, Swansea University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.637339.

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The work described in this thesis outlines the achiral synthesis of lignans and their oxidation. Chapter one classifies lignans and examines their natural occurrence and biological activities. The biosynthesis and synthesis of lignans is also reviewed. Chapter two describes the selective synthesis of trans-dibenzylbutyrolactone lignans. Tandem conjugate addition to 2(5H)-furanone utilising diphenyl thioacteals as acyl anion equivalents, followed by in situ trapping with aromatic benzyl bromides, afforded the adducts in good yields. Desulfurisation yielded the trans-dibenzylbutyrolactone lignans, including enterolactone and matairesinol. The biological activity of some trans-dibenzylbutyrolactone lignans is also discussed. Chapter three describes the non-selective synthesis of cis-dibenzylbutyrolactone lignans. An Aldol reaction with a substituted aromatic aldehyde, followed by acetylation and treatment with NaH, afforded the corresponding α,β-unsaturated lactones in good yields. Subsequent catalytic hydrogenation yielded with cis-dibenzylbutyrolactone lignans as the major product. Chapter four describes the selective oxidative cyclisation of trans-dibenzylbutyrolactone lignans using RUTFA, PIFA and DDQ to afford dibenzocyclooctadiene lignans. The non-selective oxidative cyclisation of cis-dibenzylbutyrolactone lignans was also carried out using the same reagents. It was also shown that cyclisation of para-hydroxy-dibenzylbutyrolactone lignans occurs via a spirodienone intermediate with PIFA is employed. Chapter five describes the selective oxidative cyclisation of trans-dibenzyltetrahydrofuran lignans. Reduction of the trans-dibenzylbutyrolactone lignans, and subsequent dehydration of the resultant dibenzylbutanediols, afforded the dibenzyltetrahydrofurans in good yields. These were successfully cyclised to dibenzocyclooctadiene lignans using RUTFA and PIFA. It was also shown that cyclisation of para-hydroxy-dibenzyltetrahydrofuran lignans occurs via a spirodienone intermediate with PIFA.
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32

Carlisle, J. "Thermodynamically controlled cyclisation reactions with phenylsulfanyl participation." Thesis, University of Cambridge, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.597292.

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Treatment of b-phenylsulfanyl alcohols with acid results in the formation of episulfonium ions. These can be trapped intramolecularly to produce heterocycles. These reactions are under thermodynamic control. This thesis describes the synthesis and subsequent cyclisation of tetrols. In this case there is competition between two episulfonium ions and between two possible secondary hydroxyl nucleophiles. The cyclisation of compounds in which two episulfonium ions can form at the same centre, is also investigated. Finally, the interaction between the ring size (5-vs 6-membered) and sulfur atom position (bound to a tertiary vs a secondary centre) as product-determining factors in competitive cyclisations is explored using diols.
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33

Battle, Gary Michael. "Copper mediated atom transfer radical cyclisation reactions." Thesis, University of Warwick, 2002. http://wrap.warwick.ac.uk/66931/.

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The effect of different N-pentyl-2-pyridylmethanimine (NPMI) derivatives upon the rate of copper(I) mediated atom transfer radical cyclisation (ATRC) of mono-bromo- and trichloro-acetamides were investigated. 6-Functionalised NPMI derivatives retarded the rate of ATRC due to steric effects, while for the 5-substituted analogues, inductively increasing the electron density of the pyridine nitrogen increased the rate of ATRC. Multidentate amine derived copper(l) halide complexes were found to mediate the ATRC of I-halo-N-propargylacetamides. The cyclisation of trichloro- and dichloroacetamide precursors leads to a,B-unsaturated y-Iactams containing the gem-dihalide functional group, while monohaloacetamides gave rise to either cyclised atom transfer or reduction products depending upon the solvent and catalyst used. The tripyridyJamine (TPA) copper(I) halide complex facilitates the efficient ATRC of bromo-enamides to give plactams exclusively with no formation of y-Iactams. Initial products result from 4-exo bromine atom transfer and subesqucnt elimination can be readily achieved to furnish the corresponding alkenes. A range of fused bicyclic lactams were prepared via copper(l) mediated 5-endo ATRC of halo-N-(cycloalk-1-enyl)acetamides and the use of this methodology for the synthesis of the Iycorane and erythrinane alkaloid skeletons was investigated.
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34

Tinkl, Michael. "Stereocontrolled iron-mediated cyclisation routes to heterocyles." Thesis, University of East Anglia, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358562.

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35

Thompson, David Francis. "Iron (III) mediated ring expansion / cyclisation reactions." Thesis, University of East Anglia, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297007.

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36

Amjad, ʿAlī. "Cobalt-mediated cascade cyclisation reactions in synthesis." Thesis, University of Nottingham, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357981.

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37

Roan, Graeme A. "Cobalt-mediated radical and cationic cyclisation reactions." Thesis, University of Nottingham, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336865.

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38

Snowden, David John. "Stereoselective bicyclic amine synthesis by anionic cyclisation." Thesis, University of Exeter, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.264609.

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39

Peron, Guillaume Luc Nicolas. "Lewis acid mediated cyclisation of methylenecyclopropane derivatives." Thesis, University of Southampton, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326304.

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40

Mares, Richard W. "New cyclisation reactions of 3-aminopyrazole derivatives." Thesis, University of Edinburgh, 1993. http://hdl.handle.net/1842/15263.

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Three synthetic routes to cyclised pyrazole derivatives were investigated:- The first route was based on the chemistry of 2,3-diaminopyrazoles. Reactions with various electrophiles were carried out and some cyclised products were obtained. An important reaction with carbon disulphide was carried out and this resulted in the formation of the photographically important pyrazolo[1,5-b]1,2,4-triazole ring system. The second route explored the chemistry of 3-acetamidopyrazoles. Monoacylation of 3-aminopyrazoles was found to give a mixture of 1- and 2-acylated aminopyrazoles. The mixture surprisingly underwent a solid state rearrangement to the required 3-acetamidopyrazole derivative over a period of a few days. The mechanism and kinetics of this reaction were investigated by solid state and traditional NMR methods. The third route involved the preparation and pyrolysis of pyrazol-3-yl-1,2,3-triazoles to give carbene intermediates which could cyclise. These carbenes were found to undergo a rearrangement to give the pyrazolo[1,5-b]pyrimidin-7-one ring system. The mechanism of this reaction was extensively investigated by isotopic labelling methods.
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41

Groundwater, Paul William. "Cyclisation reactions of diene-conjugated nitrile ylides." Thesis, University of Edinburgh, 1986. http://hdl.handle.net/1842/12066.

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42

Bedjeguelal, Karim. "Cyclisation par voie organométallique en série sucre." Lyon 1, 2000. http://www.theses.fr/2000LYO19005.

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43

Pillai, Jayasheela. "Heterocycle synthesis by hydrogen atom transfer and cyclisation." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298644.

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44

Brown, Paul. "Tandem Michael/aldol and Michael/Michael cyclisation reactions." Thesis, Bangor University, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.429866.

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45

Potter, Gavin R. "The synthesis and cyclisation reactions of trifluoropropynyl compounds." Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.492922.

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46

Shrivastava, Rajeev Kumar. "Synthesis of cyclohexanes via a radical cyclisation reaction." Thesis, University of Sunderland, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.270377.

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47

Fletcher, Rodney Justin. "Radical cyclisation in routes to cis-fused heterocycles." Thesis, University of Nottingham, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283701.

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48

Boehm, Haydn M. "Tandem radical cascade cyclisation reactions in steroid synthesis." Thesis, University of Nottingham, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364673.

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49

Newman, Nicola Ann. "Cyclisation strategies towards the synthesis of natural products." Thesis, University of Southampton, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342637.

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50

Barry, Conor. "Clavosolide A : Prins cyclisation in natural product synthesis." Thesis, University of Bristol, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.413614.

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