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1
Locke, Julie Myree, University of Western Sydney, College of Health and Science, and 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 systemsDoctor of Philosophy (PhD)
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Wang, Yinli. "Development of A New Heterocycle Forming Reaction and Kinetic Resolution with N-Heterocyclic Carbenes." Kyoto University, 2018. http://hdl.handle.net/2433/232320.
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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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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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Barnes, Samuel. "Synthesis of 2,4-Disubstituted Pyrimidines of Possible Biological Interest." Digital Archive @ GSU, 2008. http://digitalarchive.gsu.edu/chemistry_theses/10.
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The synthesis of 2,4-disubstituted pyrimidine derivatives is described. The synthetic route involved the addition reaction of lithiated intermediates, mostly heterocycles, to position 4 of 2-chloropyrimidine to give a dihydropyrimidine intermediate which was oxidized back to a pyrimidine. This was followed by nucleophilic aromatic substitution with various amines of the chlorine in the position 2. A number of compounds were prepared which showed binding towards various serotonin receptors in preliminary biological evaluation.
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Lapinsky, David J. "STUDIES IN AZIRIDINE-ALLYLSILANE CHEMISTRY: EXTENSION OF SCOPE." Columbus, OH : Ohio State University, 2002. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1038954949.
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Thesis (Ph. D.)--Ohio State University, 2003.Title from first page of PDF file. Document formatted into pages; contains xx, 256 p.: ill. (some col.). Includes abstract and vita. Advisor: Stephen C. Bergmeier, College of Pharmacy. Includes bibliographical references (p. 234-256).
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Qaddo, Akram. "Enantiospecific nitrogen heterocycle synthesis." Thesis, University of Sheffield, 2016. http://etheses.whiterose.ac.uk/15791/.
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Morley, Thomas James. "Sulfur mediated heterocycle synthesis." Thesis, University of Cambridge, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.613825.
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Sadig, Jessie E. R. "Palladium-catalysed heterocycle synthesis." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:c9608957-d215-4a15-87e3-5871c1391946.
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Chapter 1 is a literature review of selected palladium-catalysed aryl C-N and C-S bond forming reactions. The application of these reactions to the synthesis of heterocycles is also discussed. Chapter 2 highlights the importance of the benzimidazole motif and gives a brief discussion of the existing routes to this scaffold. The utility of N-(o-halophenyl)imidoyl chlorides and imidates as precursors to heterocycles is demonstrated in a palladium-catalysed reaction with N-nucleophiles to afford benzimidazole products. Chapter 3 provides a brief introduction to the synthesis of benzothiazoles and describes efforts towards the use of our established substrates for the preparation of these heterocycles. This is achieved via reaction of N-(o-chlorophenyl)imidoyl chlorides with a sulfur nucleophile in a metal-free process. Chapter 4 is a literature review of palladium-catalysed carbonylation chemistry with specific focus on aminocarbonylation and thiocarbonylation reactions of aryl halides. Heterocycle syntheses which employ such carbonylative methods are also discussed. Chapter 5 describes existing protocols for the synthesis of quinazolinones. A novel palladium-catalysed synthesis of these heterocycles from the reaction of our imidate substrates with an amine and carbon monoxide is described. This further demonstrates their utility as general heterocycle precursors
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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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Nordheider, Andreas. "Phosphorus-tellurium heterocycles and their lighter chalcogen analogues : from small rings to macrocycles." Thesis, University of St Andrews, 2014. http://hdl.handle.net/10023/5546.
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The research on phosphorus-chalcogen compounds enjoys a long tradition in the field of inorganic chemistry, which has led to applications such as strike-anywhere matches, precursors for metal chalcogenide thin films and versatile reagents in organic synthesis. Whereas a wide range of phosphorus-sulfur and -selenium systems is known, the literature lacks information about compounds incorporating phosphorus-tellurium bonds. This thesis describes fundamental studies that develop the basic understanding of the synthesis of phosphorus-tellurium systems and the structural characteristics of these species. The focus will be on cyclic structural motifs as these offer novel bonding modes and often an interesting reactivity. In addition, the novel compounds are compared with the properties of the sulfur and selenium analogues. Three different approaches were developed to stabilise and study compounds incorporating phosphorus-tellurium bonds: a) Stabilisation of binary organophosphorus-tellurium heterocycles by bulky substituents, b) the utilisation of P₂N₂ rings based on the dianions [{EP(NtBu)(μ-NtBu)}₂]²⁻ (E = S, Se, Te) and c) the peri-substitution of phosphorus and tellurium atoms on an acenaphthene backbone. The use of sterically demanding substituents led to the isolation of the first series of structurally characterised organophosphorus(III)-tellurium heterocycles of the type (RP)[sub]nTe[sub]m including three- to six-membered ring systems. The mild oxidation of [{EP(NtBu)(μ-NtBu)}₂]²⁻ (E = S, Se, Te) with iodine yielded macrocyclic (S, Se) or oligomeric systems (Te). Furthermore, a collection of novel P₂N₂-supported phosphorus-chalcogen heterocycles incorporating main group elements was synthesised employing [{EP(NtBu)(μ-NtBu)}₂]²⁻ (E = S, Se, Te) in metathetical reactions with main group element halides. Extension of this approach to transition metal halides generated some unusual metallocycles, as well as macrocycles and ladders incorporating coinage metals. The first peri-substituted phosphorus-tellurium species were studied regarding their interatomic and intermolecular forces. Systems of the general formula RTe–Acenap–P(iPr)₂ were shown to exhibit extensive through-space spin-spin coupling. In addition, the influence of oxidation and complexation on these interactions was investigated and the formation of peri-substituted phosphorus-tellurium cations exhibiting P–Te bonds was observed.
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Mortimer, Claire. "New transformations of azacycles." Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:1fe27dc8-6525-4d45-a398-b3e6531e7b99.
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The work presented in this thesis involves new transformations of azacycles, focusing on the introduction of functionality α-to N. α-C-H functionalisation on an azetidine has been a long-standing challenge, with N-protecting/activating groups that work well in the higher and lower azacyclic systems not viable. A recent breakthrough in the Hodgson group showed the rarely used N-thiopivaloyl group was effective for α-deprotonationâ electrophile trapping on azetidines, but was not without limitations concerning harsh removal conditions and scope for further substitutions. This thesis describes efforts to overcome these issues by development of a new protecting/activating group for N, t-butoxythiocarbonyl (Botc).
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Lewis, William. "Chiral Heterocyclic Ligands." Thesis, University of Canterbury. Chemistry, 2007. http://hdl.handle.net/10092/1383.
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This thesis describes the preparation and characterisation of a number of homochiral coordination and metallosupramolecular assemblies. These species were formed from the reaction of chiral pyridine and quinoline containing ligands and metal ions. The combination of traditional coordination chemistry and supramolecular interactions led to a range of polymeric and network structures being formed. The ligands used in this thesis can be divided into two broad categories: alkaloids and ligands derived from them, and amino acid-based ligands. In the first category three new ligands were synthesized, and a variety of routes towards alkaloid-based homochiral ligands were investigated. The second category focused on three ligand motifs, and resulted in the preparation of 16 ligands. These two categories of ligands were reacted with a range of metal salts to investigate their coordination and supramolecular chemistry. The structure of twenty complexes was determined by single crystal X-ray crystallography. The complexes had a range of structures, with discrete and polymeric species being formed. Hydrogen bonding was an important feature in the supramolecular chemistry of the complexes, playing a different role in different series of complexes. Two chiral coordination polymers and one chiral coordination network were synthesized. All three of these structures possessed directionality to some degree: in the coordination network and one of the polymers the directionality is counterbalanced by the opposite directionality being present in the crystal, while the second coordination polymer is generated by the screw axis present and has a high degree of overall directionality.
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Civcir, Pervin Unal. "Extended heterocyclic systems." Thesis, University of East Anglia, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.332359.
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Karatza, Mary-Helen. "Extended heterocyclic systems." Thesis, University of East Anglia, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359850.
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Collier, Steven James. "Heterocyclic ortho-quinodimethanes." Thesis, University of Liverpool, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366249.
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White, Lindsay Anne. "Heterocyclic o-quinodimethanes." Thesis, University of Liverpool, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262608.
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Foster, Radleigh. "Tandem reactions for nitrogen heterocycle syntheses." Thesis, University of Oxford, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.669897.
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Shirtcliff, Laura Donnell. "'Coarctate' cyclizations : applications to heterocycle synthesis /." view abstract or download file of text, 2006. http://proquest.umi.com/pqdweb?did=1188876631&sid=1&Fmt=2&clientId=11238&RQT=309&VName=PQD.
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Thesis (Ph. D.)--University of Oregon, 2006.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 336-357). Also available for download via the World Wide Web; free to University of Oregon users.
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Braunton, Alan James. "Tethered cycloaddition reactions for heterocycle synthesis." Thesis, Imperial College London, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.407915.
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Tadd, Andrew. "Palladium and copper catalysed heterocycle synthesis." Thesis, University of Oxford, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.504606.
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Brumwell, Julie E. "Heterocycle synthesis using free radical cyclisations." Thesis, University of Nottingham, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357926.
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Ball, Catherine Jane. "Palladium- and copper-catalysed heterocycle synthesis." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:589b70fb-0823-4ccf-8b35-1883908f917d.
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A number of privileged starting materials based on aryl halide frameworks have emerged that allow access to a variety of different heterocyclic scaffolds through judicious choice of reaction conditions. This work describes efforts to develop and extend the utility of two of these general heterocycle precursors - ortho-(haloalkenyl)aryl halides A and α-(ortho-haloaryl) ketones B - in conjunction with cascade reactions involving the construction of key carbon-heteroatom bonds via palladium or copper catalysis. Chapter 1 entails an overview of the development of palladium- and copper-catalysed carbon-heteroatom bond forming processes. The application of these processes in heterocycle synthesis using ortho-(haloalkenyl)aryl halide and ortho-haloacetanilides/ α-(ortho-haloaryl) ketone precursors is also described. Chapter 2 focuses on the development of a two-step synthesis of cinnolines using ortho-(haloalkenyl)aryl halides via intermediate protected dihydrocinnoline derivatives C. Chapter 3 demonstrates how the inherent reactivity of protected dihydrocinnoline derivatives C can be harnessed to provide access to functionalised products. A brief target synthesis of a pharmaceutically-relevent cinnoline is also described. Chapter 4 details attempts to develop a novel synthesis of benzothiophenes D from both ortho-(haloalkenyl)aryl halide and α-(ortho-haloaryl) ketone precursors.
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Liu, Jing. "Heterocyclic small molecule peptidomimetics." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-3125.
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Myers, Eddie Leonard. "Heterocyclic aromatic nucleic acids." Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=79056.
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In order to investigate the role played by the aromatic moiety of Aromatic Peptide Nucleic Acids (APNAs) in their ability to hybridize with RNA and DNA, as well as improve the solubility of APNA oligomers in aqueous solutions, a new generation of heterocyclic monomers were designed. APNA monomers, where the nucleobase can be thymine, cytosine adenine or guanine, with backbones contain thiophene and pyridine moieties were synthesized. Suitably protected APNA-APNA and PNA-APNA dimers were also synthesized as building blocks for the solid phase synthesis of APNA-PNA chimeras and APNA homopolymers. Due to the instability of the pyridine-containing APNA oligomers to the harsh acidic conditions required to cleave oligomers from the MBHA resin, a new protocol was developed for the synthesis of these molecules on the trityl chloride resin. Oligomers of PNA and APNA-PNA chimeras were successfully synthesized on this solid support, and cleaved from the resin using mild acidic conditions.
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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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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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Jones, Richard G. "Studies in heterocyclic synthesis." Thesis, University of Nottingham, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.238268.
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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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Chauncey, Marek Anthony. "Reactions heterocyclic quinone methides." Thesis, University of Ulster, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328193.
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Wren, S. A. C. "Cycloadditions of heterocyclic sulphinylamines." Thesis, University of York, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377290.
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Young, Richard Getliff. "Tetrazoles in heterocyclic synthesis." Thesis, Imperial College London, 1989. http://hdl.handle.net/10044/1/47727.
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Garrison, Jered C. "Silver N-Heterocyclic Carbenes." University of Akron / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=akron1124128998.
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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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Caruthers, Heather Anne. "Applications of heterocyclic synthesis." [Ames, Iowa : Iowa State University], 2009.
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Nicolson, Neil James. "Some new heterocyclic thermosets." Thesis, University of St Andrews, 1996. http://hdl.handle.net/10023/15293.
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The original aim of this project was to investigate the possibility of synthesising a novel polymer system combining the best features of cyanate ester resins and epoxy resins. Chapter 1 presents the historical background for both types of resin. The remaining three chapters describe attempts to achieve this aim by a) finding a cyanate ester that cures at a lower temperature than those in current commercial use (Chapter 2); b) using mixed epoxy and cyanate ester resins (Chapter 3); and c) designing chemically completely novel polymers from knowledge of the existing ones (Chapter 4). In Chapter 2 it was revealed that different cyanate esters cure at different temperatures, but that no obvious correlation exists between curing temperature and either steric or electronic effects of the ring substituents. The mixing of two dicyanate esters, one of which cures at a lower temperature than the other, leads to some reduction in the overall curing temperature required, but not sufficient to warrant further study at this stage. In Chapter 3 the usefulness of a previously proposed co-reaction between cyanate esters and epoxides was examined. Previous work in this area is full of inconsistencies that put many of the proposed conclusions in doubt. Further examination of the alleged co-reaction reveals that any such co-reaction is unpredictable, can vary significantly with reaction conditions and is in any case a minor reaction pathway by comparison with the self-reactions of the two individual reactants. It was therefore decided that further pursuit of this strategy was also likely to prove unrewarding in the short term. In Chapter 4 a study was made into the effects of including novel monomers in a standard epoxy resin system. These novel monomers had a cyanurate backbone with epoxide functionality, and can be cured at the lower temperatures of epoxy resins. Tests on the properties (mechanical, dielectric, water absorption, fracture toughness etc.) of these polymers were of a preliminary "scouting" nature, but are sufficiently promising to encourage further study.
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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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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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Cartwright, Matthew William. "Highly functionalised fused heterocycle synthesis from fluoropyridines." Thesis, Durham University, 2006. http://etheses.dur.ac.uk/2622/.
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Current approaches to drug discovery tends to involve the rapid analogue synthesis and testing of small, focused libraries of low molecular weight, structurally similar "drug-like" molecules, often based around heterocyclic core scaffolds. If some desired activity is shown by a compound, elaboration can give higher activity and more favourable pharmiokinetic properties. As this "lead generation" stage of drug development has been identified as a major bottleneck in the drug pipeline process, there is a great demand for methodology detailing the synthesis of highly functionalised heterocyclic compounds. Our approach involves the sequential nucleophilic aromatic substitution of highly fluorinated pyridines, in an efficient and flexible manner, to furnish a range of novel, functionalised polycyclic systems.
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Holden, Catherine. "Transition metal-free arylation and heterocycle synthesis." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/transition-metalfree-arylation-and-heterocycle-synthesis(4ecff18c-6cf9-4dfe-a874-1d83601c94d3).html.
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Arenes are ubiquitous motifs in both naturally occurring and synthetic functional organic molecules. The investigation of metal-free methodology for the installation of these motifs is important for sustainable development and the discovery of new modes of reactivity. Chapter 1. The preparation of halogenated phenoxathin 10,10 dioxides was ascertained to proceed through fluoride-induced decomposition and subsequent recombination of two molecules of the o-trimethylsilyl(aryl) triflate aryne precursors. Chapter 2. A new mild and metal-free methodology for the transition metal-free preparation of 2-amino biaryls using the benzyne intermediate was established. This proceeds via a desulfonative Truce-Smiles rearrangement of an aryl anion in the key bond-forming step. Chapter 3. The electron-poor S-aryl sulfonamides developed in chapter 2 were explored as reagents for metal-free 1,1- and 1,2-carbonamination. Asymmetric catalysis was also investigated for the preparation of enantioenriched alpha,alpha-disubstituted aryl glycine derivatives. Chapter 4. Some organocatalytic methods for the vicarious nucleophilic substitution of hydrogen were investigated to expand the remit of this classical arylation mechanism.
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Visco, Michael David. "Chiral Silanediols Designed for Enantioselective Heterocycle Functionalization." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1492438099945523.
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Swindlehurst, Marianne. "Ethoxyvinylarenes as versatile intermediates for heterocycle synthesis." Thesis, University of Surrey, 2017. http://epubs.surrey.ac.uk/841208/.
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In the field of drug discovery, pyrrolopyridine moieties are often incorporated into bioactive molecules. This is due to their ability to form both pi-stacking and hydrogen bonding interactions when binding to target proteins. This project aimed to provide a robust and rapid method of synthesis that will provide access to substituted pyrrolopyridines. The work is based on a previously published method involving the synthesis of ethoxyvinyl(amino)arenes, by Suzuki reaction of halo-aminoarenes, followed by cyclisation. It was hoped this method would be advanced by applying alternative cyclisation reactions to the ethoxyvinyl(amino)arenes to give 3-substituted products in one step. In comparison with previous methods, this route would be inexpensive, robust and applicable to a wide range of substrates. It was also envisaged that alternative starting materials could be used to make it a more generalised method for the synthesis of bicyclic arenes. Work began with testing the reproducibility of the previously published method of synthesising the ethoxyvinyl(amino)arenes. This was done successfully, although a change in ligand (SPhos to RuPhos) proved beneficial, with seven different analogues being synthesised in yields ranging from 36% to 98%. This same reaction was attempted with halo-hydroxypyridines, with a novel route to furopyridines in mind, but with no success. The synthesis of non-commercially available halo-hydroxypyridines themselves also proved to be challenging with no material being isolated. Various methods were tested for the bromo-cyclisation of ethoxyvinyl(amino)arenes to 3-bromopyrrolopyridines. A two-step method using acid cyclisation followed by bromination was entirely successful. Two-step, one-pot and one-step methods both appeared to promote polymerisation/oligermisation. Success was achieved with a one-step method employing an acid additive but only on selected ethoxyvinyl(amino)arene isomers and with varying yields. The work was extended to the attempted synthesis of anti-malarial precursors using the bromo-pyrrolopyridine isomers as building blocks and converting them to alkyl-linked glutarimides. This led to the successful and novel synthesis of the reactants vinyl glutarimide and glutarimylethylborolane. However, successful conditions for their palladium catalysed cross coupling with the bromides were not found.
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SASSI, MAURO. "Heterocycle-based redox active, electrochromic organic materials." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2011. http://hdl.handle.net/10281/25393.
Full textAbstract:
ELECTROCHROMIC MATERIALS represent a special and intriguing class of redox active compounds, characterized by a drastic change in their optical properties
upon reduction or oxidation. Many aromatic organic molecules, monomeric
or polymeric, are electrochromic, and some of them can even outperform their
inorganic counterparts in some aspects. In particular, the ability to easily tune
the colour of the redox states, represent an invaluable asset of this class of compounds.
Among the many different organic electrochromic materials, those
possessing a highly transmissive colourless state have gained much attention
for their potential application in smart windows, self-darkening eyeglasses,
anti-glare car rearview mirrors, etc. Moreover, a neutral tint of the coloured
form is desired for these applications in order to avoid colour distortion.
This work develops a novel class of discrete and polymeric electrochromic materials
based on the violene structural motif. In particular, the class of diazinium
ethenes has been explored and the electrochromic properties of the derivatives
have been evaluated by electrochemical measures. These compounds
have shown to undergo a reversible two-electron transfer, accompanied by a
colourless −)−−*− coloured electrochromic behaviour with high contrast in the
450-550nm region.
The new violene discrete electrochromes were then incorporated in a poly(3,4-
ethylenedioxythiophene) (PEDOT) matrix, developing an hybrid multichromophoric
system that take advantage of the characteristics of both systems to
achieve a panchromatic absorption in the reduced state and a very high contrast
value. In particular, the incorporation of the violene electrochromes has been
obtained linking them, through a tether, to an EDOT moiety, and subsequently
polymerizing (chemically or electrochemically) themodifiedmonomers (ISOx).
The obtained polymers, poly(ISOx), display colourless highly transmissive oxidized
states and reduced states with an extended colour palette (violet-red,
purple and brown). Moreover, an impressive electrochromic contrast in the
visible region has been achieved, with calculated luminance variations as high
as 72%. This result represent a big improvement compared to the literature reported
52% for a system with comparable spectral characteristics.
In the last chapter, a novel and versatile synthon for EDOT derivatization,
exo-methylene-EDOT, is described and characterized along with some of its
derivatives. This compound readily react with alcohols under acid catalysis
to give Markovnikov addition products, and with thiols, in presence of radical
initiators or photochemically, to give sulfides (anti-Markovnikov products).
The latter reactivity proved to be very interesting for the extreme rapidity and
high conversions achieved. An EDOT derivative with a pendant trialkoxysilane
moiety has been prepared using 3-mercaptopropyltrimetoxysilane as thiol
counterpart. This compound was subsequently tested as reagent for the functionalization
of surfaces with EDOT moieties. An alternative approach, relying
on an in situ thiol-ene reaction between exo-methylene-EDOT and a thiol functionalized
surface, was also tested to achieve such functionalization. Both procedures
have demonstrated to provide the desired surface modification. This
kind of ultra thin films could find application as coupling layers for the deposition
of PEDOT-like polymers on metal oxides, solving the adhesion problems
that hamper the long-term operation of the devices.
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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.
Full textAbstract:
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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Bemowski, Ross David. "Novel N-heterocyclic dicarbene ligands and molybdenum and dimolybdenum N-heterocyclic carbene complexes." Diss., University of Iowa, 2013. https://ir.uiowa.edu/etd/1291.
Full textAbstract:
The syntheses of a new class of polycyclic TriAmino DiCarbenes (TADCs), based on 3,9-diazajulolidine, and their precursors and adducts are described.
Starting with 2,6-dimethyl-nitrobenzene, 2,6-bis ((alkylamino)methyl)anilines (alkyl = isopropyl, mesityl, and tert-butyl) were synthesized in 40% yield over five steps. These triamines were then di-cyclized stepwise to diformamidinium dications or formamidinium/2-methoxyformaminals using oxonium salts and trialkyl orthoformates. A diformamidinium dication was characterized by single-crystal X-ray diffractometry. Treatment with various bases, particularly lithium hexamethyldisilylazide, led to the novel TADCs and monocarbenes, two of which were isolated and characterized by 1H and 13C NMR spectroscopies. In both cases, treatment with elemental sulfur trapped the TADCs as dithiobiurets. No TADC-transition metal complexes were successfully isolated from reactions of the diformamidinium dications or LiHMDS TADC complex with a number of transition metal complexes.
With the exception of these two cases, all other TADCs were not isolated because they rapidly reacted to form dimers, trimers, and tetramers. One of these dimers was isolated and its structure determined using 1D and 2D NMR spectroscopies, along with high-resolution electrospray ionization mass spectrometry. This revealed that the TADC had dimerized to form an ene-triamine, likely via 1,3-shift of a benzylic proton.
Novel N-heterocyclic Carbene (NHC) complexes of molybdenum were also synthesized and characterized. Reaction of Cp2Mo2(CO)4 (Cp = C5H5) with dimesityl-imidazol-2-ylidenes (IMes) or dimesityl-imidazolidin-2-ylidenes (SIMes) yielded the molybdoradicals CpMo(CO)2(NHC) (NHC = IMes or SIMes). The carbonyl infrared stretching frequencies and the relative metal-to-NHC π-backbonding for IMes and SIMes complexes are compared. Reaction of the less bulky dimethyl-imidazol-2-ylidene (IMe) with Cp2Mo2(CO)4 yielded the Mo-Mo triple bond complex Cp2Mo2(CO)3(IMe) by CO substitution. This is the first example of an NHC-ligated metal-metal multiply bonded complex. Single crystal X-ray diffractometry of these new organomolybdenum and organodimolybdenum complexes is discussed.
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Gerelle, Maria. "Synthesis and elaboration of heterocycles via palladium-catalyzed C-H functionalization." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:45d028d2-0548-4f22-a110-49aa97ae8dde.
Full textAbstract:
Chapter 1 is a brief literature review of the most recent progress in the area of C-H functionalization via palladium catalysis. This covers the functionalization of electron deficient arenes and heterocycles with alkenyl and alkyl halides both using inter- and intra-molecular reactions. The chapter also contains an overview of recent work from the Willis group. Chapter 2 presents the functionalization of electron deficient arenes and alkenyl bromides using palladium catalysis, as well as the use of statistical analysis software for optimizing the cross-coupling reaction. Chapter 3 describes the cross-coupling of substituted benzoxazoles, benzothiazole and benzimidazole with a range of alkenyl iodides using palladium catalysis. The reaction can tolerate both (E) and (Z) disubstituted alkenes and tri-substituted alkenyl iodides, with retention of the double bond geometry. Chapter 4 details the synthesis of sultams via an intramolecular C-H functionalization using palladium catalysis. The chapter covers the optimization of the starting material synthesis as well as the cross-coupling reaction. We can access the sulfonamides from cyclohexenone and were able to incorporate a large range of substitution patterns (Scheme 3). Finally, Chapter 5 contains all the experimental details, general considerations and compound data. All the NMR spectra of novel compounds can be found in the appendix.
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Nyoni, Dubekile. "Application of the Baylis-Hillman methodology in the construction of novel heterocyclic derivatives." Thesis, Rhodes University, 2008. http://eprints.ru.ac.za/1134/.
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Ganto, Mlungiseleli MacDonald. "Application of Baylis-Hillman methodology in the construction of complex heterocyclic targets." Thesis, Rhodes University, 2009. http://hdl.handle.net/10962/d1006703.
Full textAbstract:
Baylis-Hillman reactions using various aromatic aldehydes, activated alkenes and catalysts have been used to: - access an extensive range of poly-heterocyclic products;explore chemoselectivity; and optimise reaction efficiency. Chromone-3-carbaldehydes and chromone-2-carbaldehydes, prepared via Vielsmeier-Haack and Kostanecki-Robinson methodology, respectively, have been used as Baylis-Hillman substrates with four different catalysts, viz., 1,4-diazabicyclo[2.2.2]octane (DABCO), 3-hydroxyquinuclidine (3-HQ), imidazole and N’,N’,N’,N’- tetramethylpropanediamine (TMPDA), and with methyl vinyl ketone (MVK), methyl acrylate, cyclic enones (2-cyclohexen-1-one, 2-cyclopenten-1-one and chromones) as activated alkenes. Reactions of the chromone- -carbaldehydes with MVK afforded dimeric Baylis-Hillman adducts when catalyzed by DABCO but when the same reactions were repeated using 3-HQ as catalyst, the dimeric products were accompanied by tricyclic Baylis-Hillman adducts. Use of excess MVK, however, led to mixtures of the normal Baylis-Hillman adducts and the tricyclic adducts – interestingly, with the apparent absence of the dimeric products. While reactions of chromone-3-carbaldehydes with methyl acrylate afforded the normal Baylis-Hillman adducts, the chromone-2- carbaldehydes produced, instead, rearrangement products, consistent with an earlier, single observation. Reactions of 2-nitrobenzaldehydes with cyclic enones using imidazole as catalyst afforded the normal Baylis-Hillman adducts, reductive cyclisation of the 2-cyclohexen-1- one and 2-cyclopenten-1-one adducts, using acetic acid and iron powder, afforded the corresponding quinoline erivatives. Treatment of cyclic enones with pyridine-2-carbaldehydes and quinoline-2-carbaldehydes using TMPDA as catalyst generally gave the expected Baylis-Hillman adducts. However, indolizine derivatives were isolated directly from Baylis-Hillman reactions involving pyridine-2-carbaldehydes and 2-cyclohexen-1-one. The remaining Baylis-Hillman adducts were cyclized to the corresponding indolizines by treatment with acetic anhydride both under reflux and under microwave-assisted conditions, the latter approach providing remarkably rapid and efficient access to the polycyclic products. Computer modelling studies have been conducted on selected polycyclic products at the Molecular Mechanics (MM), Quantum Mechanical (QM) and Density Functional (DFT) levels. The theoretical results have been used to calculate UV, IR and NMR absorption data, which have been compared, in turn, with the experimental spectroscopic data. Use has also been made of the estreNova NMR prediction programme and, generally, good agreement has been observed between the predicted and experimental spectroscopic data.
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Nocanda, Xolani Wittleton. "Applications of Baylis-Idllman methodology in the synthesis of chromene derivatives." Thesis, Rhodes University, 2001. http://hdl.handle.net/10962/d1018257.
Full textAbstract:
The reaction of salicylaldehyde with various activated alkenes, viz., methyl vinyl ketone, ethyl vinyl ketone, phenyl vinyl sulfone, phenyl vinylsulfonate, acrolein and acrylonitrile, under Baylis-Hillman conditions, has been found to proceed with the chemoselective formation of chromene derivatives. The reaction conditions have been optimised and chromene derivatives have been obtained in isolated yields up to 87 %. The generality of the reaction, using 1,4-diazabicyclo[2.2.2]octane (DABCO), as the catalyst, and a heterogeneous (chloroform-water) solvent system, has been established using a range of salicylaldehyde derivatives,. including 2-hydroxynaphthaldehyde. The formation of chromene derivatives, under these conditions, has been assumed to proceed via an initial, Baylis-Hillman reaction, followed by cyclisation involving intramolecular conjugate addition, and subsequent dehydration. Evidence supporting this sequence has been obtained from the isolation ofBaylis-Hillman products from reactions involving the use of tertbutylclimethylsilyl-protected salicylaldehyde, 4-hydroxybenzaldehyde and tert-butyl acrylate as substrates. The potential of the ''Baylis-Hillman zwitterion" to participate as a donor species in Michael-type addition reactions has been explored and a series of climeric products has been isolated. The Baylis-Hillman methodology has also been successfully extended to the synthesis of sulfurcontaining heterocyclic systems, and a range of 3-substituted thiochromenes has been obtained in moderate yields, using 2,2'-dithiobenzaldehyde and various activated alkenes in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as catalyst. The electron-impact mass spectra of selected chromene and thiocbromene derivatives have been investigated permitting comparison of the fragmentation of the oxygen- and sulfur-containing analogues. In a study directed at the synthesis of potential HIV -1 protease inhibitors, chromene- and thiocbromene-containing analogues of the clinically useful drug, ritonavir, have been prepared. Thiochromene and chromene derivatives were converted to the corresponding 3 -carboxylic acids and coupled with a specially prepared, hydroxyethylene dipeptide isostere to afford ritonavir analogues containing cbromene and thiochromene termini in ca. 60% yield.
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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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