Tesi: "Heterocyclic chemistry"

1

Perrins, Ross. "Heterocyclic chemistry of trithiazyl trichloride". Thesis, Imperial College London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283411.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

2

Jones, Louise. "Combinatorial, heterocyclic and guanidine chemistry". Thesis, Bangor University, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.429865.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

3

Henderson, Neil. "Studies in nitrogen heterocyclic chemistry". Thesis, University of East Anglia, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.280300.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

4

Simcox, Michael Thomas. "Some aspects of nitrogen heterocyclic chemistry". Thesis, Loughborough University, 1997. https://dspace.lboro.ac.uk/2134/10544.

Testo completo

Abstract (sommario):

Chapter One reviews the use of scandium and lanthanide trifluoromethanesulfonates (triflates) in organic synthesis. Their ability to act as Lewis acids and so promote a wide variety of reactions are illustrated. In particular the review highlights the advantages of scandium and lanthanide triflates over more conventional Lewis acids, such as aluminium(I1I) chloride. Chapter Two describes the use of scandium and lanthanide trifiates in the reaction of acetals with amines to produce imines. The extension of this methodology to the synthesis of nitrogen-containing heterocycles such as isoindolones, isoquinolinones and ~-carboline derivatives are elaborated on. Some limitations of the methodology and the problems encountered with its application to the synthesis of enamines are covered. Chapter Three reports our approach to a novel synthesis of ~-carboline derivatives. The formylation of indole-3-acetic acid derivatives in the 2- position proved difficult and several approaches to this problem are discussed. The attempted cyclisation of imines prepared from 2-formyl- and 2- acetyl-3-indolyl acetic acid compounds are also covered. Chapter Four describes a modified Clauson-Kaas pyrrole procedure using trimethylsilyl trifiate. The selection of reaction conditions in an effort to optimise the procedure are discussed. Chapter Five provides full experimental procedures and analytical data for the reactions described in Chapters Two, Three and Four.

Gli stili APA, Harvard, Vancouver, ISO e altri

5

Civcir, Pervin Unal. "Extended heterocyclic systems". Thesis, University of East Anglia, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.332359.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

6

Karatza, Mary-Helen. "Extended heterocyclic systems". Thesis, University of East Anglia, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359850.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

7

Collier, Steven James. "Heterocyclic ortho-quinodimethanes". Thesis, University of Liverpool, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366249.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

8

White, Lindsay Anne. "Heterocyclic o-quinodimethanes". Thesis, University of Liverpool, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262608.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

9

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.

Testo completo

Abstract (sommario):

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).

Gli stili APA, Harvard, Vancouver, ISO e altri

10

Pedersen, Jan Mondrup. "Amides as radical precursors in heterocyclic chemistry". Thesis, Loughborough University, 2005. https://dspace.lboro.ac.uk/2134/34502.

Testo completo

Abstract (sommario):

In this project the use of amides as precursors for imidoyl radicals in heterocyclic chemistry has been developed. Amides were converted to thioamides, which function as precursors for imidoyl radical equivalents. Also, a novel protocol for the synthesis of imidoyl selanides was developed for the purpose of using these as imidoyl radical precursors. The precursors were used in a study of intramolecular oxidative cyclisation of imidoyl radicals onto electron deficient pyrroles and indoles. The imidoyl radical equivalents derived from thioamides did not cyclise onto heteroarene double bonds. In contrast, imidoyl radicals derived from imidoyl selanides did cyclise 6-exo onto activated heteroarenes, but yields were generally low due mainly to competing reduction of the imidoyl radical, but also due to adduct formation with isobutyronitrile radicals originating from the initiator.

Gli stili APA, Harvard, Vancouver, ISO e altri

11

Lewis, William. "Chiral Heterocyclic Ligands". Thesis, University of Canterbury. Chemistry, 2007. http://hdl.handle.net/10092/1383.

Testo completo

Abstract (sommario):

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.

Gli stili APA, Harvard, Vancouver, ISO e altri

12

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.

Testo completo

Abstract (sommario):

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.

Gli stili APA, Harvard, Vancouver, ISO e altri

13

Jones, Richard G. "Studies in heterocyclic synthesis". Thesis, University of Nottingham, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.238268.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

14

Chauncey, Marek Anthony. "Reactions heterocyclic quinone methides". Thesis, University of Ulster, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328193.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

15

Nicolson, Neil James. "Some new heterocyclic thermosets". Thesis, University of St Andrews, 1996. http://hdl.handle.net/10023/15293.

Testo completo

Abstract (sommario):

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.

Gli stili APA, Harvard, Vancouver, ISO e altri

16

Holt, Jarle. "Nitropyridine carbamates, amides and carboxylates in heterocyclic chemistry". Doctoral thesis, Norwegian University of Science and Technology, Department of Chemistry, 2006. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-1830.

Testo completo

Abstract (sommario):

Based on new methodology for nitration of pyridine and pyridine derivatives developed at our department by Professor Jan Bakke and coworkers at NTNU, a whole range of substituted nitropyridines are now readily available. The method provides new possibilities in heterocyclic chemistry for the preparation of new materials. Due to the importance and useful properties of many pyridine-based compounds, the chemistry of nitropyridine derivatives is being investigated by our group at NTNU and results for nitropyridine carbamates, amides and carboxylates are presented in this thesis. These nitropyridine derivatives have been used as substrates for the formation of new bisheterocyclic compounds and pyridine derivatives. New synthetic routes to fused heterocycles have been developed.

Chapter 2 and Paper I presents the preparation, stability and reactivity of nitropyridine isocyanates (13, 23), a new class of compounds in organic chemistry. The introduction of an electronegative substituent represented by the nitro group was expected to reduce the basisity of the pyridine nitrogen, hence decrease the rate of dimerisation and increase the reactivity of the isocyanate carbon towards a nucleophile. The preparation of nitropyridine isocyanates (13, 23) are reported.

Isocyanates constitute an important class of compounds in organic chemistry and undergo a series of reactions to yield a variety of interesting products includingheterocyclic derivatives. Heterocyclic isocyanates, however, have not received the same attention as the respective aromatic compounds in synthesis and reactivity studies because of their instability and high reactivity. 2-Pyridine isocyanate dimerises while the 4-isomer trimerises to form the trimer.

Chapter 3 and Paper I presents the preparation, stability and reactivity of the isocyanate dimer and trimer. The isocyanate dimer (28) was formed in high yield from the reactive 5-nitro-2-pyridine isocyanate (23) by a [2+4]-cycloaddition reaction. Another byproduct in the preparation of the isocyanate using oxalyl chloride was the tetrone (26).

The isocyanate trimer was formed from the unstable 4-pyridine isocyanate for reference purposes. The trimer proved to be less stable than previously reported and afforded 4-aminopyridine and methyl 4-pyridine carbamate as decomposition products in the presence of moisture and alcohols, respectively. This demonstrates that the reactive trimer can be used as a protected version of the isocyanate for synthetic purposes.

Chapter 4 and Paper II presents studies of the nitropyridine isocyanates in cycloaddition reactions. The reactivity of the nitropyridine isocyanates in 1,3-dipolar cycloaddition reactions with trimethylsilylazide and 3,5-dimethylpyridine N-oxide to afford tetrazolinones (41, 43) and substituted amines (52, 55) was investigated. A [2+4]-cycloaddition reaction of nitropyridine isocyanate with diphenylketene was also studied. The cycloadduct (59) was formed. These results demonstrate the potential of the nitropyridine isocyanates to undergo cycloaddition reactions.

Application of nitropyridine carbamates, amides and carboxylates in the formation of new heterocyclic compounds have been investigated and discussed in Chapter 5-7.

Chapter 5 and Paper III presents the aromatic nucleophilic substitution reaction of the nitro group of methyl 3-nitro-4-pyridine carboxylate. The nitro group was successfully replaced by nitrogen, oxygen and sulfur nucleophiles to afford the substitution products (16a-d) in moderate yields.

Chapter 6 and Paper IV presents the cyclization reaction of nitropyridine carbamates for the formation of 1,3-dihydro-2H-imidazo[4,5-c]pyridin-2-one (79a-b), a biologically active compound. A facile acid-catalysed cyclization method for the preparation of the cyclic urea by traditional heating and the corresponding microwave-promoted reaction were developed. Both methods afforded the cyclic urea in high yield and represent a “green method” for the preparation of this compound.

Chapter 7 and Paper V presents the preparation of 1H-1,2,3-triazol [4,5-c]pyridine (86) and N-acyl and N-alkoxycarbonyl triazolo[4,5-c]pyridine derivatives (96a-e, 98a-e). The triazolopyridine derivatives were readily formed by diazotization and cyclization of the respective nitropyridine carbamates and amides in high yields. The application of triazolo[4,5-c]pyridine derivatives (98a-e) in the acylation of amines and amino acids was investigated. They proved to be more effective than the commercially available benzotriazole and afforded the protected amines in high yields under mild conditions.

Gli stili APA, Harvard, Vancouver, ISO e altri

17

Speirs, Richard Allan. "New reagents and syntheses in heterocyclic organoselenium chemistry". Thesis, University of St Andrews, 1986. http://hdl.handle.net/10023/15417.

Testo completo

Abstract (sommario):

The main aim of this project was to develop new reagents capable of exchanging selenium for oxygen under mild conditions, to obtain new carboselenaldehyde (1) and selone (2) compounds. Phenylphosphonoselenoic dichloride (3) was prepared as a solution in xylene. It was reacted with (1,2-dithiol-3-ylidene)carbaldehydes and indolizine-3-carbaldehydes to afford 1,6aλ4-dithia-6-selena-pentalenes (5) and indolizine-3-carboselenaldehydes (6), respectively. The indolizine-3-carbaldehydes had previously been prepared from the corresponding indolizines, in turn prepared from the appropriate pyridinium bromide salts. CHSe(5)(6)Phenylphosphonoselenoic dichloride (3) was also reacted with several other carbonyl compounds. Reactions with N,N.-dimethyl- fonnamide, 5-phenyl-3H-1,2-dithiol-3-one, 2,6-dimethyl-4H.-pyran-4-one, 4-hydroxypyridine, 1-methylpyrrolidin-2-one, hexeihydro-2H-azepin-2-one, and 2,4,6-cycloheptatrien-1-one met with varied success, and only N,N-dimethylselenoformamide (7), 5-phenyl-3H-1,2-dithiole-3-selone (8), and 2,6-dimethy1-4H-pyraxi-4-selone (9) were obtained.(8)(9)The presence of a stabilising substituent was therefore required, and was introduced as a tungsten pentacarboiyl species. Pentacarbon-yl(indolizine-3-carboselenaldehyde-Se) tungsten(0) (10) and penta-carbonyl(2,4,6-cycloheptatriene-1-selone-Se)tungsten(0) (11) were obtained from the reaction of the corresponding oarboryl compounds with phenylphosphonoselenoic dichloride (3) in the presence of tetra- ethylanunonium iodopentacarbonyltungstate(0).The reagent (4) was prepared from the reaction of chlorodlphenyl- phosphine and tetramethylammonium selenocyanate, and was reacted in situ with indolizine-3-carbaldehydes to produce not only indolizine-3-carboselenaldehydes (6), but also compounds which were proposed on the strength of spectral and analytical evidence as being members of the novel 3-(indolizin-3-yl)-2,5-dihydro-2-selenoformyl-1,2,4-selena- diazole-5-selone (12) system.

Gli stili APA, Harvard, Vancouver, ISO e altri

18

Liu, Jing. "Heterocyclic small molecule peptidomimetics". [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-3125.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

19

Fishwick, C. W. G. "Azaxylylenes and their heterocyclic analogues". Thesis, University of Liverpool, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356266.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

20

Brown, J. W. "Studies of heterocyclic reaction mechanisms". Thesis, Bucks New University, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356206.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

21

Jenkins, Graham. "Heterocyclic analogues of ortho-xylylene". Thesis, University of Liverpool, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.279695.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

22

Large, Janet. "Asymmetric induction using heterocyclic precursors". Thesis, Open University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.272951.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

23

Hu, Gang. "Conducting polymers from heterocyclic compounds". Thesis, Open University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240331.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

24

Scarisbrick, Andrew Colin. "Transition metal chemistry of anionic functionalised N-heterocyclic carbenes". Thesis, University of Nottingham, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.415903.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

25

Foster, R. W. "Sustainable approaches to novel heterocyclic scaffolds for medicinal chemistry". Thesis, University College London (University of London), 2015. http://discovery.ucl.ac.uk/1470876/.

Testo completo

Abstract (sommario):

This thesis investigates new methods for the environmentally sustainable synthesis of heterocyclic scaffolds for application in medicinal chemistry. Chapter I introduces general principles of sustainability in synthetic organic chemistry. This includes the characterization and application of sustainable solvents and the use of biomass feedstocks in synthesis. Chapter II explores the synthesis of substituted isoindolinones via a ruthenium-catalyzed alkyne cyclotrimerization. The introduction details the synthesis and medicinal application of isoindolinones and describes previous research involving alkyne cyclotrimerizations. Following this, the development of a regioselective alkyne cyclotrimerization reaction in a sustainable solvent is reported. The optimized alkyne cyclotrimerization conditions are then used to synthesize a selection of isoindolinone products. Chapter III describes the application of a kinetically-controlled furan-Diels–Alder reaction to the synthesis of heterocyclic scaffolds, including the endo-cantharimide. The study and application of furan-Diels–Alder reactions are introduced. Following this, the Diels–Alder reaction of a 3-alkoxyfuran under sustainable reaction conditions is explored experimentally and applied to the diastereoselective synthesis of endo-cantharimides. The potential application of endo-cantharimides in medicinal chemistry is discussed with the aid of biological testing and the Diels–Alder reactions of 3-alkoxyfurans is probed with the aid of computational calculations. Chapter IV concerns the cyclization of reducing sugars to prepare chiral tetrahydrofurans. The role of tetrahydrofurans in medicinal chemistry, the synthesis of tetrahydrofurans from sugar derivatives and the application of hydrazones in synthetic chemistry are introduced. Following this the development of a hydrazone-mediated cyclization of L-arabinose under sustainable reaction conditions is reported. The optimized conditions are applied to prepare tetrahydrofurans from other sugars. The manipulation of the tetrahydrofuran products is also explored. Chapter V draws some general conclusions from the thesis and describes potential future directions for the research. Chapter VI contains the details of experimental procedures and compound characterization for the results discussed in Chapters II–IV.

Gli stili APA, Harvard, Vancouver, ISO e altri

26

Burrows, Kenneth Dvid. "The chemistry of some heterocyclic analogues of triphenylmethane dyes". Thesis, University of Central Lancashire, 1985. http://clok.uclan.ac.uk/20234/.

Testo completo

Abstract (sommario):

A comprehensive series of triphenylmethane dyes has been synthesised in which the phenyl ring of Malachite Green has been replaced by a 5- or 6- membered heterocycle containing nitrogen, oxygen or sulphur as hetetâacoins. The visible absorption spectra of the dyes have been correlated with the electronic and structural features of the molecules. Novel analogues of Malachite Green have been prepared containing terminal pyrrolidine and N-methylpiperazine groups. Differences in the electronic absorption spectra of the parent dyes have been compared with those of related systems and the differences have been interpreted in terms of the inductive effects and relative basicities of the terminal groups. The observed spectral changes for the Pyrrolidine Green and N-methylpiperazine Green series are in general agreement with the published data for the analogous Malachite Green and Brilliant Green derivatives. Where substitution occurs in the meta- and para- positions of the phenyl ring, the wavelength of maximum absorption bears a linear relationship to the appropriate Hammett substituent constant. Observed Xmax(x) values for disubstituted compounds are in good agreement with the values calculated on the basis of additivity of substituent effects. The spectral changes of the x-band arising from ortho- substitution are consistent with the relief of steric hindrance by rotation of the phenyl ring. A study of bridged analogues of Malachite Green in which the dimethylaminophenyl rings are joined by an ethane or ethene unit across the 2'- and 2"- positions has been initiated. To gain experience with the syster comprehensive series of carbinols containing the dibenzosuberone and dibenzosuberenone moieties have been synthesised. A successful route to the 2,2'-ethano-bridged anologue of 4,4'-dimethoxybenzophenone has been developed and several dye bases have been prepared from this ketone. However, elaboration of this synthesis to the corresponding bisdimethylamino derivative failed to yield the ketone.

Gli stili APA, Harvard, Vancouver, ISO e altri

27

Ho, Yee-Ping. "Some studies in nitrogen heterocyclic chemistry using Reissert compounds". Thesis, Loughborough University, 1986. https://dspace.lboro.ac.uk/2134/33250.

Testo completo

Abstract (sommario):

The thesis reports the first examples of Reissert compounds prepared from five-membered ring heterocycles. The method utilises trimethylsilyl cyanide as the key reagent in a single phase non-aqueous medium. Previous attempts to synthesise such compounds have failed because, under the conventional two phase conditions, the reaction either does not proceed or ring opening of the heterocycle occurs. Reaction of benzothiazole with an acid chloride (aliphatic, aromatic or chloroformate) and trimethylsilyl cyanide in dichloromethane has been shown to give rise to 3-acyl-2-cyano-2,3-dihydrobenzothiazoles. Eight such five-membered ring Reissert compounds have been prepared, mostly in yields exceeding 70%. The mechanistic involvement of trimethylsilyl cyanide is discussed. The novel Reissert compounds have been shown to be versatile intermediates for the further modification of the starting heterocycles.

Gli stili APA, Harvard, Vancouver, ISO e altri

28

Alsulami, Rabah Nafa. "SYNTHETIC APPROACHES TO HETEROCYCLIC BICYCLO[2.1.0]PENTANES". Bowling Green State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1309446512.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

29

Walji, Dhiran. "A radical approach towards the synthesis of novel pyridine and pyrimidine based heterocycles". Thesis, Available from the University of Aberdeen Library and Historic Collections Digital Resources, 2009. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?application=DIGITOOL-3&owner=resourcediscovery&custom_att_2=simple_viewer&pid=62164.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

30

Wilson, Jennifer M. "Synthesis of biologically active heterocyclic compounds". Thesis, University of Glasgow, 2007. http://theses.gla.ac.uk/45/.

Testo completo

Abstract (sommario):

More than 11 million people worldwide are diagnosed with cancer every year. New cancer drugs are required that are more effective and selective. Nitrogen mustard alkylating agents crosslink DNA inhibiting transcription and replication. Use of the mustard pharmacophore as part of a macrocycle allows metal complexation and produces a prodrug. Hypoxic tumour cells have increased concentrations of reductase enzymes which could lead to reduction of the complex in situ and release of a cytotoxic drug. Human African Trypanosomiasis is commonly known as Sleeping Sickness and affects over 36 countries of sub-Saharan Africa. It is transmitted to humans by the tsetse fly which carries the parasitic subspecies Trypanosoma brucei rhodesiense and Trypanosoma brucei gambiense. Any compounds synthesised would also be tested to assess their potential as anti-parasitic agents. Parker synthesised a range of polyazamacrocycles. Testing of compound A in vitro gave highly efficient DNA crosslinking activity. Copper complexes were formed of the macrocycles and B was found to be 24 times more toxic against hypoxic cells than oxic cells thus exploiting tumour hypoxia and creating a selective drug. Jones synthesised a range of oxaazamacrocycles such as C which when tested in vitro exhibited comparable cross-linking activity to the azamacrocycles although it proved impossible to synthesise the corresponding copper complexes. It was decided to vary the leaving group on the alkylating arms to see if the DNA crosslinking results could be improved. Eight carbamates and the corresponding copper complexes were synthesised. The R-groups were alkyl and aromatic. Anti-cancer DNA crosslinking and hypoxia selectivity results were disappointing however, a number of compounds displayed significant activity when tested against T. brucei. A range of thiaazamacrocycles would complete the set of heteroatom-containing macrocycles (N, O, S) and might produce good DNA crosslinking results. It might also be possible to synthesise the corresponding copper complexes producing prodrugs. Six thiaazamacrocycles were synthesised and 2-hydroxyethyl arms were attached. However it proved impossible to isolate the desired alkylating agents with the 2-chloroethyl arms. In the body, the p53 protein activates the transcription of specific genes. In healthy cells, the levels of p53 have to be kept to a minimum to allow the normal running of the cell, e.g. growth and replication. This function is carried out by the HDM2 protein, which forms an auto-regulatory feedback loop with p53. In some tumours, the p53 function is disrupted due to genetic mutations of p53. However other tumours possess ‘wild type’ p53 – this type of p53 has lost the ability to respond to oncogenic stress due to over-expression of HDM2. Drugs that inhibit HDM2 should cause stabilisation of p53 and induce apoptosis in cancer cells. A small library of 5-deazaflavins were synthesised and biologically tested producing some interesting biological results.

Gli stili APA, Harvard, Vancouver, ISO e altri

31

Richardson, K. A. "The synthesis of heterocyclic prostacyclin analogues". Thesis, University of East Anglia, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355353.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

32

Chaloner, Lynne Marie. "Heterocyclic o-quinodimethanes from 3-sulfolenes". Thesis, University of Liverpool, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333628.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

33

Orrling, Kristina M. "On the Versatility of Microwave-Assisted Chemistry : Exemplified by Applications in Medicinal Chemistry, Heterocyclic Chemistry and Biochemistry". Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-101356.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

34

Deane, Philip O'Grady. "Synthetic and mechanistic studies of heterocyclic systems". Thesis, Rhodes University, 1996. http://hdl.handle.net/10962/d1005044.

Testo completo

Abstract (sommario):

A series of acrylate esters and selected analogues have been reacted with pyridine-2-,pyridine-3-, and pyridine-4-carboxaldehydes in the presence of diazabicyclo[2,2,2]octane (DARCO) to afford a range of Baylis-Hillman products. The pyridine-2-carboxaldehyde-derived products have been acetylated using acetic anhydride and the kinetics of the thermal cyclisation of the acetylated compounds to indolizines was investigated using proton NMR spectroscopy. The first-order kinetics of the cyclisation has been confirmed and the influence of substituents on the first-order rate constant, kₒbs has been examined. The kinetic data has been shown to be consistent with the previously proposed mechanism in which loss of the acetate group is ratedetermining. Each of the cyclisations was also monitored at three different temperatures permitting evaluation of the activation parameters. The Baylis-Hillman products and related acetylated derivatives were treated at room temperature with sodium methylthiolate; the hydroxy precursors were observed to undergo conjugate addition with a degree of diastereocontrol but the acetylated derivatives favoured an apparent SN¹ displacement of the acetate group.

Gli stili APA, Harvard, Vancouver, ISO e altri

35

Orton, Edward. "Synthesis and chemistry of 4,5-dimethylene-1,3-dioxolan-2-one and related compounds /". Thesis, Connect to this title online; UW restricted, 1985. http://hdl.handle.net/1773/8620.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

36

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.

Testo completo

Abstract (sommario):

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.

Gli stili APA, Harvard, Vancouver, ISO e altri

37

Nocanda, Xolani Wittleton. "Applications of Baylis-Idllman methodology in the synthesis of chromene derivatives". Thesis, Rhodes University, 2001. http://hdl.handle.net/10962/d1018257.

Testo completo

Abstract (sommario):

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.

Gli stili APA, Harvard, Vancouver, ISO e altri

38

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.

Testo completo

Abstract (sommario):

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.

Gli stili APA, Harvard, Vancouver, ISO e altri

39

Diebolt, Olivier. "N-heterocyclic carbene ligands in palladium and iridium organometallic chemistry". Thesis, University of St Andrews, 2010. http://hdl.handle.net/10023/2126.

Testo completo

Abstract (sommario):

The use of ligand in transition-metal catalysed reactions has had a considerable impact. The present manuscript aims at showing the influence of ligands in the palladium catalysed Suzuki-Miyaura cross-coupling reaction. In chapter one, the mechanism of this reaction will be described based on the numerous contribution published in the literature. It will be shown that the electronic and steric properties of the ligands have a huge repercussion on the catalytic activity of the metal. In the second chapter, the electronic and steric properties of the widely used Buchwald-phosphine ligand will be investigated. For this purpose, bis-carbonyl iridium(I) complexes were synthesized and their characterization allowed determining their TEP (Tolman electronic parameter) and their buried volume %V[subscript(bur)]. Then three next chapters of this thesis will focus on the syntheses and characterizations of new palladium complexes bearing N-heterocyclic carbenes (NHC). Their design was made in a view to obtain high activity in cross coupling reaction, particularly in the Suzuki-Miyaura cross coupling. Their activation under the catalytic conditions leads to the formation of palladium(0) species that can be mono- or bis-ligated. The influence of the ligand on the catalyst activity will be discussed. A palladium(II) precatalyst leading to mono-ligated active species will be described. Its activity in cross-coupling is very good, since activated and non-activated aryl chlorides could be coupled with aryl boronic acids at room temperature using low catalyst loadings. Unfortunately, the catalyst activity decreased with temperature. This result showed the fragility of the mono-ligated active species. In a view to obtain more robust catalysts that can perform high turnover numbers, new palladium(II) precatalysts bearing two ancillary ligands were developed. Mixed systems NHC- phosphites and NHC-phosphines are described. NHC-phosphites precatalysts displayed very good activity, but the phosphites are unfortunately sensitive to reaction conditions, limiting their role of active species shield. NHC-phosphine bearing complexes were highly active and could perform up to 10,000 turnovers with unactivated aryl chlorides. Very interestingly, these catalysts were also able to couple benzylchlorides and allyl chlorides with a wide range of boronic acids at very low catalyst loadings. These reactions had also the great advantage to proceed in aqueous solvents at very high substrate concentration. The activation mechanism of these complexes was investigated. Dichloropalladium(II) complexes were reduced under the catalytic conditions to lead palladium(0) species. Therein, it is shown that this reduction step was rate-determining in catalysis. Some palladium(0) intermediates xxiv were synthesized and showed good to excellent activities at low temperature under the exact same conditions. They displayed high reactivity towards oxygen and moisture and have to be handled under inert atmosphere. A particular complex had the ability to react with molecular dioxygen to form a stable peroxo-complex. Interestingly, this complex displayed excellent activity in water under aerobic conditions. This system was of great advantage since the reaction could be set up under air using cheap and user-friendly reagents displaying low toxicity. Moreover, the readily available distilled water used as solvent did not require prior degassing. Symmetrical and unsymmetrical bis-NHC palladium(0) complexes were successfully synthesized. They display excellent activity in the Suzuki-Miyaura cross coupling and turnover frequencies as high as 300 could be obtained at room temperature with unactivated arylchlorides and arylboronic acids. These complexes were also found excellent catalysts for the coupling of benzylchlorides with arylboronic acids. Mechanistic studies showed that no ligand dissociation occurred during the coupling suggesting as bis-ligated active species.

Gli stili APA, Harvard, Vancouver, ISO e altri

40

Wilson, John Daniel. "Metal complexes of heterocyclic thiones and thionates". Thesis, Northumbria University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333906.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

41

Ingate, Simon Thomas. "Conformation and reactivity of 1,3-heterocyclic systems". Thesis, University of Portsmouth, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304065.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

42

Archbold, Trevor. "Synthesis and functionalisation of heterocyclic[2.2.2]octanes". Thesis, University of Liverpool, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288305.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

43

Crew, Andrew Philip Austin. "Approaches to heterocyclic analogues of o-xylyene". Thesis, University of Liverpool, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316473.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

44

Plant, A. "Metallation approaches to heterocyclic analogues of orthoxylylene". Thesis, University of Liverpool, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384397.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

45

Crockett, Rowena. "Generation of free radicals from heterocyclic compounds". Thesis, University of Aberdeen, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.290239.

Testo completo

Abstract (sommario):

Tetrazolinones, thiatriazole 1-oxides and meso-ionic oxatriazoles were investigated as sources of free radicals. Mono-substituted tetrazolinones decomposed at their melting points. Nitrosation and nitration of the tetrazolinone ring was unsuccessful, although alkoxyalkylation of the ring took place in ether in the presence of nitrosomium and nitronium tetrafluoroborate. The tetrazolinone ring was photolytically unstable, and both eliminated nitrogen and cycloreverted. γ-irradiation of the naphthyl deivative caused cleavage of the nitrogen-hydrogen bond to give a radical which was identified by spin trapping and esr spectroscopy. Thiatriazolyl radicals were generated from thiatriazol-1-ium salts by reduction over sodium metal. Deuterium and nitrogen-15 labelled diphenylthiatriazolium salts were prepared in the reaction between thiatriazole 1-oxides and phosphorus pentachloride or pentabromide. This allowed an unambiguous assignment of the nitrogen and hydrogen hyperfine coupling constants in the esr spectrum of the unlabelled thiatriazolyl radical. X-ray crystallographic analysis was carried out on single crystals of 2,4-diphenyl-2,5-dihydro-1,2,3,5-thiatriazol 1-oxide and 2,4-diphenyl-2H-1,2,3,5-thiatriazol-1-ium bromide. Meso-ionic oxatriazolones were relatively stable to thermolysis, whereas oxatriazolimines decomposed at their melting points. The oxatriazolones decomposed on photolysis via two mechanistic pathways, while the oxatriazol-imines were resistant to photolysis. Radicals were generated by γ-irradiation and oxidation via decomposition of the heterocyclic ring. Electrochemical reduction of nitrophenyl derivatives allowed an investigation of radicals in which the heterocyclic ring was remote from the radical centre. Photochemical reaction between the nitrophenyl derivatives of the oxatriazole and tetrahydrofuran produced oxy-nitroxide radicals which were realatively long-lived and in which the heterocyclic ring was intact. The rates of hydrolysis and crystal structures of three diacetylazolinones, including diacetyltetrazolinone were investigated with the aim of determining whether a correlation existed between bond lengths and reactivity. The relative rates of hydrolysis were found to be independent of the bond lengths. However a correlation was found between the rates of hydrolysis and the acidity of the unsubstituted azolinones.

Gli stili APA, Harvard, Vancouver, ISO e altri

46

Berthelot, Didier. "Synthesis of novel heterocyclic #alpha#-amino acids". Thesis, Open University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367226.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

47

Yoshida, Shu. "Design synthesis and characterization of novel heterocyclic polymers". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape16/PQDD_0008/NQ37033.pdf.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

48

O'Donovan, Jacqueline Patricia. "The synthesis and properties of substituted heterocyclic mesogens". Thesis, Kingston University, 1993. http://eprints.kingston.ac.uk/20570/.

Testo completo

Abstract (sommario):

The initial aim of this work was to synthesise novel pyrazine based esters where the pyrazine ring occupies a central position within the ester molecule. Four novel series of pyrazine based esters were prepared. (1) 5-Phenylpyrazin-2-yl 4-n-alkoxyphenylcarboxylates. (2) 5-(4[sup]/-n-Propylphenyl)pyrazin-2-yl trans-4-n-alkylcyclohexylcarboxylates. (3) 5-(4[sup]/-Ethoxy-3[sup]/-fluorophenyl)pyrazin-2-yl 4-n-alkyloxyphenylcarboxylates. (4) 5-(3[sup]/-Fluoro-4[sup]/-methoxyphenyl)pyrazin-2-yl 4-n-alkoxyphenylcarboxylates. Comparison of the liquid crystal properties of the pyrazine based esters with the analogous phenyl esters was carried out. For comparison with the pyrazine ester series (2) and (3) the analogous phenyl ester series (5) and (6) were prepared. (5) 4-(4[sup]/n-Propylphenyl)phenyl trans-4-n-alkylcyclohexylcarboxylates and, (6) 4-(4[sup]/-Ethoxy-3[sup]/-fluorophenyl)phenyl 4-n-alkyloxyphenylcarboxylates. In general the substitution of the central phenyl ring in the ester molecules with a pyrazine ring resulted in: (i) A depression in the nematic thermal stability. (ii) A depression in the smectic thermal stability to a greater extent than that of the nematic stability. (iii) A general reduction in the melting points. Two ring pyrazine based systems containing a terminal chlorine were synthesised i.e. (7). The analogous terminal bromine compounds of series (8) were also prepared for comparison purposes. (7) 5-( 4-Chlorophenyl)-2-( n-alkoxy)pyrazines. (8) 5-(4-Bromophenyl)-2-(n-alkoxy)pyrazines. Series (7) showed a greater smectic thermal stability than series (8). Synthesis of series (7) and (8) also produced the N-alkylated isomers of series (7) and (8), the 1-n-alkyl-5-(4-chlorophenyl)-pyrazin-2-ones and the 1-n-alkyl-5-(bromophenyl)-pyrazin- 2-ones respectively. Three series of terphenyl analogues which contain a terminal pyrazine ring were prepared using the appropriate 5-(4-bromophenyl)-2-(n-alkoxy)pyrazines as the precursors. (9) 2-n-Alkoxy-5-[4-(4[sup]/-n-propylphenyl)phenyl]pyrazines. (10) 2-n-Alkoxy-5-[ 4-( 4[sup]/-fluorophenyl)phenyl]pyrazines. (11) 2-n-Alkoxy-5-[4-(4[sup]/-n-butoxy-2[sup]/,3[sup]/-difluorophenyl)phenyI]pyrazines. A selection of pyrazine based ethynyl compounds were also prepared. These compounds exhibited very high birefringence values, and were highly smectogenic. The preparation of these novel pyrazine based compounds resulted in a number of patent applications being made by Merck U.K. Ltd.

Gli stili APA, Harvard, Vancouver, ISO e altri

49

Vincent-Rocan, Jean-François. "N-Isocyanates : Versatile Intermediates in Heterocyclic Synthesis". Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/34864.

Testo completo

Abstract (sommario):

Nitrogen heterocycles are present in nearly 60% of all small-molecule drugs approved by the US Food and Drug Administration. New innovative methods that streamline the synthesis of such heterocycles are therefore highly desirable. The use of new or underdeveloped reactive intermediates provides an excellent opportunity to develop novel heterocyclic syntheses. For example, nitrogen-substituted isocyanates (N-isocyanates) are a class of rare amphoteric isocyanates with high, but severely underdeveloped synthetic potential. The research efforts presented in this thesis have been directed towards the use of such intermediates for the rapid construction of heterocycles using cascade reactions. Using an in situ generation approach from masked (blocked) isocyanate precursors, we were able to control the homo dimerization of these species and design several cascade reactions forming more than 10 different classes of heterocycles using appropriate nitrogen nucleophiles. Given the importance of the N-N-C=O motif in pharmaceuticals and agrochemicals, N-isocyanates provide the opportunity to synthesize highly desirable cores for different industrial applications. To illustrate the potential of this new tool in heterocyclic chemistry, more than 200 heterocycles were synthesized using this methodology. In Chapter 2, heterocycles incorporating only one atom from the N-isocyanate will be presented. More precisely, the first cascade reaction involving N-isocyanates for the rapid synthesis of saturated heterocycles will be presented. The incorporation of 2 atoms within the ring will then be discussed in Chapter 3 with the synthesis of hydantoins, imidazolones, thiazolines, pyrazoles and phthalazinones. Chapter 4 will focus on the incorporation of every atom in the heterocycle to form other bioactive cores such as azauracils, pyridazinones and azadiketopiperazines. Lastly, Chapter 5 will describe our efforts for the synthesis of acyclic molecules such as semicarbazides and aza-peptides.

Gli stili APA, Harvard, Vancouver, ISO e altri

50

Armugam, S. "Studies on N-Heterocyclic Compounds". Thesis, Indian Institute of Science, 1994. https://etd.iisc.ac.in/handle/2005/108.

Testo completo

Abstract (sommario):

The thesis entitled "Studies on N-Hetero cyclic Compounds: (a) Reaction of 5,6,7,8-Tetrahydroisoquinolines with Vilsmeier Reagent and (b) Amide Induced in situ Alkylation of 5,6-Dihydroisoquinolines" is presented in two parts. Part I involves a study of the Vilsmeier reaction of 4-cyano-1,3-dihydroxy-5,6,7,8 tetrahydroisoquinoline derivatives, while Part II concerns the in situ alkylation of l-alkyl-4-cyano-3-methoxy-5,6- dihydroisoquinolines in presence of KNH2/liq.NH3.

Gli stili APA, Harvard, Vancouver, ISO e altri

Tesi sul tema "Heterocyclic chemistry"

Cita una fonte nei formati APA, MLA, Chicago, Harvard e in molti altri stili