No description available.

No description available.

This research investigated the mechanism of action in bacteria of 3,4-methylenedioxy-β-nitropropene (BDM-I), a very broad spectrum antimicrobial lead compound in development as an anti-infective drug. The thesis proposes that BDM-I inhibits bacterial protein tyrosine phosphatases, a novel mechanism of action for an antimicrobial agent and a new target in microorganisms. This very open investigation was directed by considerable biological information on the effects of BDM-I in microorganisms and animals which provided insights into possible and improbable cellular targets. The biological effects of BDM-I were investigated using biochemical and cell-based assays, transmission electron microscopy and whole genome DNA microarray analysis. The specific experiments and order of execution were largely dependent on information gained as the project progressed. BDM-I was shown not to target the metabolic pathways of the major classes of antibacterial drugs, which supports a novel mechanism of action. Investigation of several species-specific effects suggested that cell signalling pathways were a possible target. Based on the structure of BDM-I and review of the scientific literature on cell signalling in bacteria, the hypothesis that BDM-I acted by inhibition of protein tyrosine phosphatases (PTP) was supported by demonstrating inhibition of human and bacterial PTP's in an enzyme assay. This mechanism was consistent with other demonstrated effects: inhibition of the intracellular pathogen, Chlamydia trachomatis; inhibition of swarming in Proteus spp. and inhibition of pigment production in Serratia marcescens; and with kill kinetics in bacteria and yeast. A pilot global genome analysis of BDM-I treated Bacillus subtilis did not detect differential expression of PTP genes but has provided many avenues for further investigation. This research further supports the development of BDM-I as a broad spectrum anti-infective drug.

The primary goal of the research described in this thesis concern the synthesis, characterization and study of 1,8-bis(diarylmethylium)naphthalenediyl dications. Such dications have been prepared from the corresponding diols and have been fully characterized. Single crystals X-ray diffraction studies indicate that the two cationic centers of these derivatives are separated by 3.0 - 3.1 ??. The enforced proximity of the cationic centers intensifies the electron deficiency of these derivatives which behave as strong organic oxidants. As indicated by cyclic voltammetry, these dications undergo a two-electron reduction to afford the corresponding acenaphthenes. The newly formed C-C bond which links the former methylium are remarkably long (1.628-1.706 ??.) and can, in some instances, be oxidatively cleaved in the presence of acids. These dications can also be reduced chemically by reducing reagent, such as hydride, chloride, bromide and iodide. Remarkably, the reaction of 1,8-bis(diphenylmethylium)naphthalenediyl dication with fluoride anion results in the formation of a mono fluorinated cation which features an unsymmetrical C-F?C bridge between the former methylium centers. As indicated by 1H NMR spectroscopy, the structure of this cation is fluxional with the fluorine atom oscillating between the former methylium centers. Finally, this thesis also deals with the synthesis and study of 4,6-bis(dimesitylboryl)dibenzofuran and isoelectronic dications.

The research conducted for this thesis has led to the development of an intramolecular gold-catalysed direct arylation protocol whereby tethered arenes and aryltrimethylsilanes are coupled (Scheme 1). In Chapter 1, the key synthetic and mechanistic studies that have ultimately led to the conception of this project are introduced. In Chapter 2, the substrate scope of intramolecular direct arylation is assessed. The reaction tolerates a wide range of substrates with tether lengths between one and five units (containing C, N and O) generating 5- to 9- membered rings. Substrates that lead to 5-membered rings (1 → 2) can tolerate a broad electronic range of substituents and proceed under the mildest reaction conditions (≤ 1 mol% catalyst, room temperature) and with excellent yields. A smaller collection of examples is demonstrated for the cyclisation to 6- and 7- membered rings (3 → 4, 5 → 6), but no heating is required and good yields are maintained throughout the series. The synthetically challenging synthesis of 8- and 9- membered rings (7 → 8, 9 → 10) is successful, albeit with slightly more forcing conditions (4 mol%, up to 50 °C). The methodology was subsequently applied in the successful 10-step synthesis of natural product allocolchicine 11. In Chapter 3, the operative reaction mechanism is elucidated. Reaction monitoring techniques allowed for the detailed study of linear free energy relationships (LFERs) and kinetic isotope effects (KIEs), which in turn allowed for deduction of the reaction turnover-limiting step (TLS) and thus the first quantitative experimental data on the effects of aryl electron demand and conformational freedom on the rate of reductive elimination from diarylgold(III) species. The mechanistic investigation led to the observation of complex kinetic profiles for specific substrates. The origin of these unusual effects is the focus of Chapter 4. By combining experiment with kinetic simulation, an off-cycle catalyst inhibition pathway was identified and the understanding of this process allowed for a re-optimisation of reaction conditions. In Chapter 5, the general kinetic parameters that could govern any domino reaction combining inter- and intramolecular direct arylation are deduced through kinetic analysis and simulation of hypothetical systems. The results of the kinetic analysis were proved experimentally through the successful combination of intra- and intermolecular gold-catalysed direct arylation. The products of intramolecular cyclisation 2, generated in-situ, are demonstrated to couple with intermolecular aryltrimethylsilanes 12, resulting in a rapid increase in molecular complexity from simple substrates in one pot.

No description available.

Elaboration de matériaux métallacalix[4]arènes pour la valorisation des hydrocarbures basée sur un nouveau concept de greffage par voie COMS dont la mise au point par fonctionnalisation de supports silice en faisant réagir l’hydroquinone avec une espèce originale [(SiO)2AliBu.(Et2O)]. La réactivité du complexe W(CtBu)(CH2tBu)3 avec l’hydroquinone supportée [(SiO)2AlO-C6H4-OH.(Et2O)] a permis de générer un nouveau système catalytique bien défini [(SiO)2AlO-C6H4-OW(CtBu)(CH2tBu)2.(Et2O)] entièrement caractérisé. Par cette méthode, l’ancrage du calixarène [[4H]-(OH)3(H)] sur le complexe de surface [(SiO)2AliBu.(Et2O)]SBA-15-(700) a conduit à l’espèce [(SiO)2Al-O-[4H]-(OH)2.(Et2O)]. L’incorporation de complexes organométalliques du groupe IV (Zr) et VI (W) mène à de nouveaux matériaux métallacalix[4]arènes bipodaux. L’élucidation de leurs structures a été appuyée par comparaison avec les données spectroscopiques de leurs homologues solubles ou directement liés à la silice. Ces matériaux, présentant des espaceurs phénoxy, montrent des activités initiales supérieures à celles de leurs homologues supportés sur silice. Avant la préparation des matériaux métallacalix[4]arènes, une série de complexes titana-, zircona- et tantalacalix[4]arenes solubles bi- et tripodaux a été synthétisée et caractérisée à partir de dérivés calix[4]arène présentant des modes de coordination différents pour le métal (podalité, ligands ancillaires, angle OMO). Parallèlement, une relation structure-réactivité dans la polymérisation des oléfines a été établie dans le cas des titanacalix[4]arènes, et pour les tantalacalix[4]arènes, des activations Csp2-H et O-Me intramoléculaires ont été mises en évidence. / Generation of novel metallacalix[4]arenes materials applied to the valorization of hydrocarbons prepared using an unprecendented COMS method by the first functionalization of the silica support by reaction of hydroquinone with the unreported supported species [(SiO)2AliBu.(Et2O)].The reactivity between the complex W(CtBu)(CH2tBu)3 and the hydroquinone species [(SiO)2AlO-C6H4-OH.(Et2O)] allows the access to new well-defined catalytic systems [(SiO)2AlO-C6H4-OW(CtBu)(CH2tBu)2.(Et2O)]. Using this way, the anchoring of the calixarene [[4H]-(OH)3(H)] onto [(SiO)2AliBu.(Et2O)]SBA-15-(700) leads to the surface complex [(SiO)2Al-O-[4H]-(OH)2.(Et2O)].The subsequent incorporation of organometallic complexes from groups IV (Zr) and VI (W) provided novel bipodal metallacalix[4]arenes materials, characterized by IR, solid-state NMR, microanalysis and EXAFS. The clarification of their structures was supported by comparison of the spectroscopic data collected from their soluble models or analogues directly bonded to silica. These new materials, presenting phenoxo linkers display higher initial conversion rates than their analogues directly grafted on silica. Before preparation of the materials, a set of bi and tripodal titana-, zircona- and tantalacalix[4]arenes complexes were synthesized and characterized from calix[4]arenes derivatives ligands, presenting different mode of coordination for the metal (podality, ancillary ligands, OMO bite angle). In parallel, a structure-reactivity relation in the polymerization of ethylene was established in the case of the titanacalix[4]arenes, while Csp2-H and O-Me intramolecular activations were related for the tantalacalix[4]arenes.

The thesis titled “Novel Strategies for the Synthesis of Organo-Sulfur Compounds Under Metal-free Reaction conditions” is presented into three main sections. Section A– deals with the synthesis of thiourea and thioamide. Section B– describes the sulfenylation of electron-rich arenes, ketones and β- diketones Section C– deals with the sulfur/fluorine assisted deacylation of α-sulfenylated β- diketones. Section A: This section is divided in to two chapters, Chapter 1 and Chapter 2. Chapter 1 of this section describes the non-isothiocyanate route to obtain trisubstituted thioureas of arylamines by using in situ generated dithiocarbamates of secondary amines. Trisubstituted thioureas of aryl amines are important precursors for the synthesis of heterocyles like 2-aminobenzothiazoles derivatives,1 amidines,2 and guanidines.3 Therefore, this strategy provides an excellent opportunity to access thioureas containing primary aryl amines without employing isothiocyanates. From the current method, the broad substrate scope was achieved with excellent yield of the corresponding products. Further, under the optimized reaction conditions a variety of functional groups like ketones, carboxylic acids, amides and sulfonamides were found to be well tolerated. A few representative examples are shown in Scheme 1.4 (a) Jordan, A. D.; Luo, C.; and Reitz, A. B. J. Org. Chem. 2003, 68, 8693. (b) Joyce, L. L.; Batey, R. A. Org. Lett. 2009, 11, 2792 and references therein. (c) Jamir, L.; Khatun, N.; Patel, B. K. RSC Adv., 2011, 1, 447. 1 Biswas, K.; Greaney, M. F. Org. Lett. 2011, 13, 4946. 2 (a) Wilson, L. J.; Klopfenstein, S. R.; Li, M. Tetrahedron Lett. 1999, 40, 3999. (b) Schneider, S. E.; Bishop, P. A.; Salazar, M. A.; Bishop, O. A.; Anslyn, E. V. Tetrahedron 1998, 54, 15063. 3 Varun, B. V.; Prabhu, K. R. RSC Adv.2013, 3, 3079. Synopsis Chapter 2 describes the rapid, high yielding and easily isolable method for the synthesis of thioamide by nucleophilic addition of electron-rich arenes to isothiocyanates. Thioamides are essential structural motifs which are found in a variety of biologically active molecules.5 They are also crucial building blocks for synthesizing sulfur conntaining heterocycles.6 The current method employs triflic acid (TfOH) to activate the nitrogen of isothiocyanate, where as, in the earlier methods AlCl3 was used.7 Also, the reaction was found to be highly regioselective and the broad substrate scope of the reaction was demonstrated (Scheme 2).85 (a) Cremlyn, R. J. An Introduction to Organosulfur Chemistry,John Wiley and Sons, Chichester, 1996. (b) Gottesman, M. M.; Fojo, T.; Bates, S. E. Nat. Rev. Cancer 2002, 2, 48; (c) Angehrn, P.; Goetschi, E.; Gmuender, H.; Hebeisen, P.; Hennig, M.; Kuhn, B.; Luebbers, T.; Reindl, P.; Ricklin, F.; Schmitt-Hoffmann, A. J. Med. Chem.2011, 54, 2207 6 (a)Shibuya, I.; Honda, K.; Gama, Y.; Shimizu, M. Heterocycles 2000, 53, 929. (b) Takido, T.; Itabashi, K.; Synthesis 1985, 430. (c) Shibuya, I.; Gama, Y.; Shimizu, M. Heterocycles 2001, 55, 381. (d) Wang, H.; Wang, L.; Shang, J.; Li, X.; Wang, H.; Gui, J.; Lei, A. Chem. Commun., 2012, 48, 76. (e) Alla, S. K.; Sadhu, P.; Punniyamurthy, T. J. Org. Chem., 2014, 79, 7502. (f) Chaudhari, P. S.; Pathare, S. P.; Akamanchi, K. G. J. Org. Chem., 2012, 77, 3716. (g) Mendoza-Espinosa, D.; Ung, G.; Donnadieu, B.; Bertrand, G. Chem. Commun.,2011, 47, 10614. (h) Potts, K. T.; Houghton, E.; Singh, U. P. J. Org. Chem., 1974, 39, 3627. 7 a) Jagodzinski, T.; Jagodzinska, E.; Jabłonski, Z. Tetrahedron 1986, (b) Jagodzinski, T. Synthesis 1988, 717. 8 Varun, B. V.; Sood, A.; Prabhu, K. R. RSC Adv.2014, 4, 60798. Scheme 2: Synthesis of thioamide Section B This section is divided in to two chapters, Chapter 1 and Chapter 2. Chapter 1 of this section describes a facile transition metal-free oxidative CDC (Cross Dehydrogenative Coupling) reaction leading to a regioselective thiolation of electron-rich arenes and hetero-arenes. This strategy provides a rare opportunity of using thione in a CDC reaction to form C–S bonds to obtain arylthiobenzoxazoles, hetero-arylthiobenzoxazoles and arylthiobenzthiazoles, which are pharmaceutically valuable compounds.9 This highly regioselective CDC reaction is unique as it requires the reversing the reactivity of sulfur to form the C–S bonds. Despite the propensity of thiols to undergo oxidation, this method provides an elegant and new avenue for synthesizing thioethers of benzazoles (Scheme 3).10 a) Greco, M. N.; Hageman, W. E.; Powell, E. T.; Tighe, J. J.; Persico, F. J. J. Med. Chem. 1992, 35, 3180. b) Zhang, J.-T.; Qi, J.; Feng, H.; Dong, Z. WO2010048603, 2010. c) Greco, M. N.; Hageman, W. E.; Powell, E. T.; Tighe, J. J.; Persico, F. J. J. Med. Chem. 1992, 35, 3180. d) Barchuk, W. T.; Dunford, P. J.; Edwards, J. P.; Fourie, A. M.; Karlsson, L.; Quan, J. M. US 2008194630. e) Koci, J.; Klimesova, V.; Waisser, K.; Kaustova, J.; Dahse, H.-M.; Moellmann, U.;Bioorg. Med. Chem. Lett. 2002, 12, 3275. 10 Varun, B. V.; Prabhu, K. R. J. Org. Chem.2014, 79, 9655. xii Synopsis Scheme 3: C-H-Functionalization of electron-rich arenes Chapter 2 is discussed in two parts, Part A and Part B. Part A: deals with the C–H functionalization of β-diketones via CDC reactions. A variety β-diketones were sulfenylated at α-position with a variety of benzazole-2-thione derivatives. Sulfenylation of β-diketones is challenging as β-diketones undergo deacylation after sulfenylation in the reaction medium.11 The highlight of this work is that the resultant products do not undergo deacylation. Under the optimal reaction conditions a variety of functional group like ketones, acids and esters were well tolerated. Also, the resultant sulfenylated β-diketones were further manipulated to α,α-disubstituted β-diketones and pyrazoles (Scheme 4).12 11 (a) Ogura, K.; Sanada, K.; Takahashi, K.; Iida, H. Tetrahedron Lett.1982, 23, 4035. (b) Zou, L.-H.; Priebbenow, D. L.; Wang, L.; Mottweiler, J.; Bolm, C. Adv. Synth. & Catal. 2013, 355, 2558. 12 Varun, B. V.; Gadde, K.; Prabhu, K. R. Org. Lett. 2015, 17, 2944. Scheme 4: C-H Functionalization of β-diketones via CDC reaction Chapter 2, Part B: deals with the C–H functionalization of ketones via CDC, which is the continuation of the above discussed work (Chapter 2, Part B). The products obtained from this method can be further modified and can be used for the synthesis of α,β-unsaturated carbonyl compounds under Trost or Julia olefination reaction conditions.13 A variety of actophenone derivatives, propiophenone derivatives and simple alkyl ketones were sulfenylated at the α-position with various benzazole-2-thiones (Scheme 5).14 Scheme 5: C-H Functionalization of ketones via CDC reaction (a) Trost, B. M.; Salzmann, T. N.; Hiroi, K. J. Am. Chem. Soc. 1975, 98, 4887. (b) Baudin, J. B.; Hareau, G.; Julia, S. A. Tetrahedron Lett. 1991, 32, 1175. (c) Blakemore, P. R.; Cole, W. J.; Kocienski, P. J.; Morley, A. Synlett 1998, 26. 14 Manuscript under preparation. Section C This section describes the ‘sulfur/fluorine assisted deacylation of β-diketones.’ Achieving a controlled mono fluorination at α- position of a ketone group is a difficult task. Therefore, an alternate approach is to have a sulfide group at α-position to a ketone (electron withdrawing moiety) and thereby providing additional stability to the generated reactive intermediate at α-position. Till date, this transformation has been achieved only by electrochemical methods.15 In continuation of our earlier work of α-sulfenyl β-diketones for exploring the synthetic utility of α-sulfenyl β-diketones (like benzylation and allylation), we performed the fluorination reaction. In this reaction, the fluorinated product (a diketone) underwent a de-acylation process to furnish the corresponding α-fluorinated ketone and we further optimized the reaction conditions and explored the substrate scope for this reaction. Under the optimized reaction conditions a variety of fluorinated products were isolated in excellent yield (Scheme 6) Scheme 6: Sulfur/Fluorine assisted deacylation of β-diketones 15Fuchigami, T.; Shimojo, M.; Konno, A.; Nakagawa, K. J. Org. Chem. 1990, 55, 6074 16 Manuscript under preparation.

Synthetic molecular receptors find applications in the selective extraction, transport and detection of neutral or charged species and the study of these systems is an important facet of supramolecular chemistry. In this thesis, we focused our attention on a specific family of molecular receptors called calix[6]arenes. These receptors possess a hydrophobic cavity formed by 6 aromatic rings that can accommodate small organic molecules. They can furthermore be easily functionalized and give rise to for example ditopic receptors or sensing systems. We worked with two families of calix[6]arenes but also looked at the complexation properties of some related compounds: a homooxacalix[3]arene and a resorcin[4]arene derivatives. The first part of this thesis is devoted to the study of the complexation properties of a fluorescent calix[6]tris-pyrenylurea. The binding of anions, ion pairs, ion triads and phospholipids was monitored by 1H Nuclear Magnetic Resonance (NMR) and Emission Spectroscopy. Our results showed that the receptor exhibits a remarkable selectivity for the sulfate anion in DMSO for which a binding constant of the order of 103 M-1 was found. In chloroform the affinity for sulfate is of the order of 105 M-1 and the selective recognition of ammonium-TBASO4 triads was observed (TBA = tetra-n-butylammonium; ammonium = PrNH3+, HexNH3+ or DodNH3+). This work has been reported in the paper “Fluorescent Chemosensors for Anions and Contact Ion Pairs with a Cavity-Based Selectivity” Emilio Brunetti, Jean-François Picron, Karolina Flidrova, Gilles Bruylants, Kristin Bartik and Ivan Jabin J. Org. Chem. 2014, 79, 6179–6188. We also showed that calix[6]tris-pyrenylurea displays a remarkable selectivity in chloroform for phospholipids bearing a phosphatidylcholine head (PCs) over those bearing a phosphoethanolamine head (PEs). We were able to show that this fluorescent receptor is able to extract PCs from a water solution enabling their quantification. This work has been reported in the paper “A Selective Calix[6]arene-based Fluorescent Chemosensor for Phosphatidylcholine Type Lipids” Emilio Brunetti, Steven Moerkerke, Johan Wouters, Kristin Bartik and Ivan Jabin Org. Biomol. Chem. 2016. Accepted Manuscript. DOI: 10.1039/C6OB01880G.The second part of this thesis is devoted to the evaluation of the binding properties of different receptors incorporated into dodecylphosphocholine (DPC) micelles. This strategy was used to make the hydrophobic molecular receptors “water-compatible” without having to undertake synthetic modifications. Our results showed that a calix[6]azacryptand-based receptor can be incorporated into DPC micelles, either as a zinc complex or as a polyammonium at low pH. We observed that the zinc complex incorporated in the micelles is able to bind small and long linear primary amines in its cavity and we were able to highlight that complexation is driven by the hydrophobic effect. This work has been reported in the paper “Primary Amine Recognition in Water by a Calix[6]aza-cryptand Incorporated in Dodecylphosphocholine Micelles” Emilio Brunetti, Alex Inthasot, Flore Keymeulen, Olivia Reinaud, Ivan Jabin and Kristin Bartik Org. Biomol. Chem. 2015, 13, 2931-2938.We also validated the micellar incorporation strategy with a homooxacalix[3]tris-acid and with a resorcin[4]arene zinc complex bearing four methyl-imidazole moieties. Once incorporated into DPC micelles, we showed that the two receptors can bind small organic guests: the homooxacalix[3]arene derivative can bind tert-butylammonium or adamantylammonium, albeit with low affinity and the resorcin[4]arene-based zinc complex can bind acetate and acetylacetone.The final part of this thesis is devoted to the work undertaken in order to try and elucidate the guest exchange mechanism of calix[6]arene-zinc complexes where the zinc is tri-coordinated to the calixarene-based ligand and coordinates a guest molecule inside the calixarene cavity. The hypothesis that we put forward is that when the zinc is only tri-coordinated to the calixarene ligand, the guest exchange mechanism involves a zinc penta-coordinated intermediate where the zinc atom is simultaneous coordinated to an endo-complexed guest (inside the cavity) and an exo-complexed molecule (outside the cavity). 1D EXchange SpectroscopY experiments (EXSY) were undertaken with two calix[6]arene-zinc complexes where the zinc is tri-coordinated to the calixarene ligand and with a calix[6]arene-zinc complex where the zinc is tetra-coordinated to the calixarene ligand. The exchange of different guests (ethanol, dimethylformamide and acetonitrile) was monitored in deuterated dichloromethane. We observed that in all cases water accelerates guest exchange but that the guest residence times are highly dependent on the acidity of the metal center and on the nature of the guest buried inside the cavity. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished

Pillar[n]arenes are a class of macrocycles with outstanding properties given by its electron rich and symmetric cavity, and facile functionalization that allows to tune its solubility and host-guest properties. In this work, the versatility of pillar[n]arenes for the design of porous materials is studied. Pillar[n]arenes are stable to guest removal, giving solvent-free phases and thus resulting in permanent porous structures. From simple ethyl pillar[5,6]arenes, nonporous adaptive crystals are obtained and studied for the recognition and separation of butanol isomers. The cavity size of the pillar[n]arene hosts and the linear or branched characteristic of the butanol isomers influences the assembly of the pillararene to selectively adsorb an isomer. Then, an A1/A2 benzaldehyde-functionalized pillar[5]arene is used as a building block for the synthesis of an imine porous organic cage, which would result in material with intrinsic and extrinsic porosity. Finally, a lipoic acid modified pillar[5]arene is implemented as ligand for nanoclusters, improving their stability. Taking advantage of the cavity of the pillar[5]arene, a host-guest complex is formed, enhancing the optical properties of nanoclusters.