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Sample records for kommenteerinud krista aren

  1. Arene oxidation with malonoyl peroxides.

    PubMed

    Dragan, Andrei; Kubczyk, Tomasz M; Rowley, Julian H; Sproules, Stephen; Tomkinson, Nicholas C O

    2015-06-01

    Malonoyl peroxide 7, prepared in a single step from the commercially available diacid, is an effective reagent for the oxidation of aromatics. Reaction of an arene with peroxide 7 at room temperature leads to the corresponding protected phenol which can be unmasked by aminolysis. An ionic mechanism consistent with the experimental findings and supported by isotopic labeling, Hammett analysis, EPR investigations, and reactivity profile studies is proposed. PMID:25966313

  2. Protolytic defluorination of trifluoromethyl-substituted arenes

    PubMed Central

    Kethe, Anila; Tracy, Adam F.; Klumpp, Douglas A.

    2011-01-01

    A series of trifluoromethyl-substitutued arenes were studied in their reactions with Brønsted superacids. The products from these reactions suggest the formation of reactive electrophiles, such as carbocations, acylium cations, or equivalent electrophilic species. As such, Friedel-Crafts type reactions occur between these species and arene nucleophiles. NMR studies were done and the results suggest the formation of an acyl group from the trifluoromethyl groups in superacid. PMID:21547324

  3. Gold(I)-mediated C-H activation of arenes.

    PubMed

    Lu, Pengfei; Boorman, Tanya C; Slawin, Alexandra M Z; Larrosa, Igor

    2010-04-28

    We demonstrate the first Au(I)-mediated C-H activation of arenes. Au(I) salts undergo C-H activation with electron-poor arenes, in stark contrast to Au(III) salts, which activate electron-rich arenes. This operationally simple and highly regioselective process occurs under very mild conditions and gives access to a variety of Au(I)-arene complexes in excellent yields. PMID:20364835

  4. Methods for preparation of cyclopentadienyliron (II) arenes

    DOEpatents

    Keipert, Steven J.

    1991-01-01

    Two improved methods for preparation of compounds with the structure shown in equation X [(Cp)--Fe--(Ar)].sup.+.sub.b X.sup.b- (X) where Cp is an eta.sup.5 complexed, substituted or unsubstituted, cyclopentadienyl or indenyl anion, Ar is an eta.sup.6 complexed substituted or unsubstituted, pi-arene ligand anad X is a b-valent anion where b is an integer between 1 and 3. The two methods, which differ in the source of the cyclopentadienyl anion - Lewis acid complex, utilize a Lewis acid assisted ligand transfer reaction. The cyclopentadienyl anion ligand, assisted by a Lewis acid is transferred to ferrous ion in the presence of an arene. In the first method, the cyclopentadienyl anion is derived from ferrocene and ferrous chloride. In this reaction, the cyclopentadienyliron (II) arene product is derived partially from ferrocene and partially from the ferrous salt. In the second method, the cyclopentadienyl anion - Lewis acid complex is formed by direct reaction of the Lewis acid with an inorganic cyclopentadienide salt. The cyclopentadienyliron (II) arene product of this reaction is derived entirely from the ferrous salt. Cyclopentadienyliron (II) arene cations are of great interest due to their utility as photoactivatable catalysts for a variety of polymerization reactions.

  5. Room-temperature direct alkynylation of arenes with copper acetylides.

    PubMed

    Theunissen, Cédric; Evano, Gwilherm

    2014-09-01

    C-H bond in azoles and polyhalogenated arenes can be smoothly activated by copper acetylides to give the corresponding alkynylated (hetero)arenes by simple reaction at room temperature in the presence of phenanthroline and lithium tert-butoxide under an oxygen atmosphere. These stable, unreactive, and readily available polymers act as especially efficient and practical reagents for the introduction of an alkyne group to a wide number of arenes under remarkably mild conditions. PMID:25115357

  6. Arene Selectivity by a Flexible Coordination Polymer Host.

    PubMed

    Wright, James S; Vitórica-Yrezábal, Iñigo J; Thompson, Stephen P; Brammer, Lee

    2016-09-01

    The coordination polymers [Ag4 (O2 CCF3 )4 (phen)3 ]⋅ phen⋅arene (1⋅phen⋅arene) (phen=phenazine; arene=toluene, p-xylene or benzene) have been synthesised from the solution phase in a series of arene solvents and crystallographically characterised. By contrast, analogous syntheses from o-xylene and m-xylene as the solvent yield the solvent-free coordination polymer [Ag4 (O2 CCF3 )4 (phen)2 ] (2). Toluene, p-xylene and benzene have been successfully used in mixed-arene syntheses to template the formation of coordination polymers 1⋅phen⋅arene, which incorporate o- or m-xylene. The selectivity of 1⋅phen⋅arene for the arene guests was determined, through pairwise competition experiments, to be p-xylene>toluene≈benzene>o-xylene>m-xylene. The largest selectivity coefficient was determined as 14.2 for p-xylene:m-xylene and the smallest was 1.0 for toluene:benzene. PMID:27483388

  7. Alkenylation of Arenes and Heteroarenes with Alkynes.

    PubMed

    Boyarskiy, Vadim P; Ryabukhin, Dmitry S; Bokach, Nadezhda A; Vasilyev, Aleksander V

    2016-05-25

    This review is focused on the analysis of current data on new methods of alkenylation of arenes and heteroarenes with alkynes by transition metal catalyzed reactions, Bronsted/Lewis acid promoted transformations, and others. The synthetic potential, scope, limitations, and mechanistic problems of the alkenylation reactions are discussed. The insertion of an alkenyl group into aromatic and heteroaromatic rings by inter- or intramolecular ways provides a synthetic route to derivatives of styrene, stilbene, chalcone, cinnamic acid, various fused carbo- and heterocycles, etc. PMID:27111159

  8. Fitness Centers Aren't Just for "Kids"

    MedlinePlus

    ... My Go4Life Get Free Stuff Be a Partner Fitness Centers Aren't Just for “Kids” If you’ ... exercise, you might be reluctant to join a fitness center or exercise program at your local senior ...

  9. Piling Up Pillar[5]arenes To Self-Assemble Nanotubes.

    PubMed

    Nierengarten, Iwona; Guerra, Sebastiano; Ben Aziza, Haifa; Holler, Michel; Abidi, Rym; Barberá, Joaquín; Deschenaux, Robert; Nierengarten, Jean-François

    2016-04-25

    New liquid-crystalline pillar[5]arene derivatives have been prepared by grafting first-generation Percec-type poly(benzylether) dendrons onto the macrocyclic scaffold. The molecules adopt a disc-shaped structure perfectly suited for self-organization into a columnar liquid-crystalline phase. In this way, the pillar[5]arene cores are piled up, thus forming a nanotubular wire encased within a shell of peripheral dendrons. The capability of pillar[5]arenes to form inclusion complexes has been also exploited. Specifically, detailed binding studies have been carried out in solution with 1,6-dicyanohexane as the guest. Inclusion complexes have also been prepared in the solid state. Supramolecular organization into the Colh mesophase has been deduced from X-ray diffraction data and found to be similar to that observed within the crystal lattice of a model inclusion complex prepared from 1,4-dimethoxypillar[5]arene and 1,6-dicyanohexane. PMID:26888329

  10. Networked calix[4]arene polymers with unusual mechanical properties.

    PubMed

    Grima, Joseph N; Williams, Jennifer J; Evans, Kenneth E

    2005-08-28

    Polymeric networks built from calix[4]arenes that form a three dimensional folded structure have been predicted to exhibit negative Poisson's ratios (auxetic), an unusual property which makes them superior to conventional materials in many practical applications. PMID:16091801

  11. Fifty years of oxacalix[3]arenes: A review

    PubMed Central

    Cottet, Kevin; Marcos, Paula M

    2012-01-01

    Summary Hexahomotrioxacalix[3]arenes, commonly called oxacalix[3]arenes, were first reported in 1962. Since then, their chemistry has been expanded to include numerous derivatives and complexes. This review describes the syntheses of the parent compounds, their derivatives, and their complexation behaviour towards cations. Extraction data are presented, as are crystal structures of the macrocycles and their complexes with guest species. Applications in fields as diverse as ion selective electrode modifiers, fluorescence sensors, fullerene separations and biomimetic chemistry are described. PMID:22423288

  12. From Pillar[n]arene Scaffolds for the Preparation of Nanomaterials to Pillar[5]arene-containing Rotaxanes.

    PubMed

    Nierengarten, Iwona; Deschenaux, Robert; Nierengarten, Jean-François

    2016-01-01

    Pillar[n]arenes are a new class of macrocycles that are efficiently prepared from readily available building blocks. In this particular field, our research teams became interested in the use of a pillar[5]arene core as a compact scaffold for the synthesis of nanomaterials with a controlled distribution of functional groups on both rims of the macrocyclic framework. Such compounds have found applications in biology as multivalent ligands for specific lectines or as polycationic compounds for gene delivery. Liquid-crystalline derivatives have been prepared by grafting mesogenic subunits on the pillar[5]arene core. On the other hand, we also became interested in the preparation of pillar[5]arene-containing [2]rotaxanes. In particular, we have shown that pillar[5] arene-based [2]rotaxanes can be obtained from the reaction of amine stoppers with pseudo-rotaxanes resulting from the association of a pillar[5]arene derivative with a diacyl chloride reagent. Finally, amphiphilic [2]rotaxanes have been prepared and incorporated in thin ordered films at the air-water interface. PMID:26931219

  13. Negative ion gas-phase chemistry of arenes.

    PubMed

    Danikiewicz, Witold; Zimnicka, Magdalena

    2016-01-01

    Reactions of aromatic and heteroaromatic compounds involving anions are of great importance in organic synthesis. Some of these reactions have been studied in the gas phase and are occasionally mentioned in reviews devoted to gas-phase negative ion chemistry, but no reviews exist that collect all existing information about these reactions. This work is intended to fill this gap. In the first part of this review, methods for generating arene anions in the gas phase and studying their physicochemical properties and fragmentation reactions are presented. The main topics in this part are as follows: processes in which gas-phase arene anions are formed, measurements and calculations of the proton affinities of arene anions, proton exchange reactions, and fragmentation processes of substituted arene anions, especially phenide ions. The second part is devoted to gas-phase reactions of arene anions. The most important of these are reactions with electrophiles such as carbonyl compounds and α,β-unsaturated carbonyl and related compounds (Michael acceptors). Other reactions including oxidation of arene anions and halogenophilic reactions are also presented. In the last part of the review, reactions of electrophilic arenes with nucleophiles are discussed. The best known of these is the aromatic nucleophilic substitution (SN Ar) reaction; however, other processes that lead to the substitution of a hydrogen atom in the aromatic ring are also very important. Aromatic substrates in these reactions are usually but not always nitroarenes bearing other substituents in the ring. The first step in these reactions is the formation of an anionic σ-adduct, which, depending on the substituents in the aromatic ring and the structure of the attacking nucleophile, is either an intermediate or a transition state in the reaction path. In the present review, we attempted to collect the results of both experimental and computational studies of the aforementioned reactions conducted since the

  14. Study: Ex-NFL Players Aren't At Greater Risk for Suicide

    MedlinePlus

    ... NFL Players Aren't at Greater Risk for Suicide Rate was lower than would be expected among ... football players aren't at greater risk of suicide than the general U.S. population, federal health officials ...

  15. Thiacalix[4]arene: New protection for metal nanoclusters

    PubMed Central

    Guan, Zong-Jie; Zeng, Jiu-Lian; Nan, Zi-Ang; Wan, Xian-Kai; Lin, Yu-Mei; Wang, Quan-Ming

    2016-01-01

    Surface organic ligands are critical for the formation and properties of atomically precise metal nanoclusters. In contrast to the conventionally used protective ligands such as thiolates and phosphines, thiacalix[4]arene has been used in the synthesis of a silver nanocluster, [Ag35(H2L)2(L)(C≡CBut)16](SbF6)3, (H4L, p-tert-butylthiacalix[4]-arene). This is the first structurally determined calixarene-protected metal nanocluster. The chelating and macrocyclic effects make the thiacalix[4]arene a rigid shell that protects the silver core. Upon addition or removal of one silver atom, the Ag35 cluster can be transformed to Ag36 or Ag34 species, and the optical properties are changed accordingly. The successful use of thiacalixarene in the synthesis of well-defined silver nanoclusters suggests a bright future for metal nanoclusters protected by macrocyclic ligands. PMID:27536724

  16. Molecular Recognition of Natural Products by Resorc[4]arene Receptors.

    PubMed

    D'Acquarica, Ilaria; Ghirga, Francesca; Quaglio, Deborah; Cerreto, Antonella; Ingallina, Cinzia; Tafi, Andrea; Botta, Bruno

    2016-01-01

    This review is aimed at providing an overview of the up-to-now published literature on resorc[4]arene macrocycles exploited as artificial receptors for the molecular recognition of some classes of natural products. A concise illustration of the main synthetic strategies developed to afford the resorc[4]arene scaffold is followed by a report on the principles of the gas-phase investigation of recognition phenomena by mass spectrometry (MS). Emphasis is placed on gas-phase studies of diastereoisomeric complexes generated inside a Fourier transform-ion cyclotron resonance (FT-ICR) mass spectrometer by resorc[4]arene receptors towards a series of natural products, namely amino acids, amphetamine, ethanolamine neurotransmitters, dipeptides, vinca alkaloids and nucleosides. The literature outcomes discussed here, taken largely from our own revisited work, have been completed by references to other studies, in order to draw a broader picture of this rapidly evolving field of research. PMID:26654589

  17. Activation-Enabled Syntheses of Functionalized Pillar[5]arene Derivatives.

    PubMed

    Han, Jie; Hou, Xisen; Ke, Chenfeng; Zhang, Huacheng; Strutt, Nathan L; Stern, Charlotte L; Stoddart, J Fraser

    2015-07-01

    A series of regioselective di- and trifunctionalized pillar[5]arene derivatives have been synthesized by a deprotection-followed-by-activation strategy, and their constitutions have been established as a result of having access to their solid-state structures. De-O-methylation occurs in a stepwise manner at lower temperatures under kinetic control, affording the desired oligo-substituted pillar[5]arene derivatives. In addition, the regioisomers of these derivatives can be isolated by installing triflate groups on the free hydroxyl groups. PMID:26083303

  18. Palladium-catalyzed arylation of simple arenes with iodonium salts.

    PubMed

    Storr, Thomas E; Greaney, Michael F

    2013-03-15

    The development of an arylation protocol for simple arenes with diaryliodonium salts using the Herrmann-Beller palladacycle catalyst is reported. The reaction takes simple aromatic feedstocks and creates valuable biaryls for use in all sectors of the chemical industry. PMID:23461706

  19. Nickel Hydrides Supported by a Non-Innocent Diphosphine Arene Pincer: Mechanistic Studies of Nickel-Arene H-Migration and Partial Arene Hydrogenation

    PubMed Central

    Lin, Sibo; Day, Michael W.; Agapie, Theodor

    2011-01-01

    Nickel hydrides supported by a terphenyl diphosphine were synthesized and found to undergo nickel-to-arene H-transfers. Some of the resulting complexes also undergo the reverse (C-to-Ni) H-migration indicating the potential for storing H-equivalents in this type of pincer ligand. NMR spectroscopy, single crystal X-ray diffraction, and isotopic labeling studies investigating the mechanism of these processes are discussed. PMID:21344904

  20. DFT studies on the directing group dependent arene-alkene cross-couplings: arene activation vs. alkene activation.

    PubMed

    Zhang, Lei; Fang, De-Cai

    2015-08-01

    Due to its green-chemistry advantages, the dehydrogenative Heck reaction (DHR) has experienced enormous growth over the past few decades. In this work, two competing reaction channels were comparatively studied for the Pd(OAc)2-catalyzed DHRs of arenes with alkenes, referred to herein as the arene activation mechanism and the alkene activation mechanism, respectively, which mainly differ in the involvement of the reactants in the C-H activation step. Our calculations reveal that the commonly accepted arene activation mechanism is plausible for the desired arene-alkene cross-coupling; in contrast, the alternative alkene activation mechanism is kinetically inaccessible for the desired cross-coupling, but it is feasible for the homo-coupling of alkenes. The nature of directing groups on reactants could mainly determine the dominance of the two competing reaction routes, and therefore, influence the experimental yields. A wide range of directing groups experimentally used are examined by the density functional theory (DFT) method in this work, providing theoretical guidance for screening compatible reactants. PMID:26108375

  1. Synthesis and Structure of Corona[6](het)arenes Containing Mixed Bridge Units.

    PubMed

    Fu, Zhan-Da; Guo, Qing-Hui; Zhao, Liang; Wang, De-Xian; Wang, Mei-Xiang

    2016-06-01

    A one-pot nucleophilic aromatic substitution reaction of 3,6-dichlorotetrazine with various diphenols and dibenzenethiols produced corona[4]arene[2]tetrazines that contain mixed oxygen, sulfide, methylene, and sulfone linkages. Macrocyclic ring transformations employing an inverse-electron-demand Diels-Alder reaction of tetrazine moieties with enamines and the subsequent sulfide oxidation reaction afforded diverse corona[4]arene[2]pyridazines. The acquired corona[6]arenes adopted three types of conformational structures in the crystalline state. PMID:27182609

  2. Iridium/N-heterocyclic carbene-catalyzed C–H borylation of arenes by diisopropylaminoborane

    PubMed Central

    Igarashi, Takuya

    2016-01-01

    Summary Catalytic C–H borylation of arenes has been widely used in organic synthesis because it allows the introduction of a versatile boron functionality directly onto simple, unfunctionalized arenes. We report herein the use of diisopropylaminoborane as a boron source in C–H borylation of arenes. An iridium(I) complex with 1,3-dicyclohexylimidazol-2-ylidene is found to efficiently catalyze the borylation of arenes and heteroarenes. The resulting aminoborylated products can be converted to the corresponding boronic acid derivatives simply by treatment with suitable diols or diamines. PMID:27340457

  3. [Accumulation of polycyclic arenes in Baltic Sea algae].

    PubMed

    Veldre, I A; Itra, A R; Paal'me, L P; Kukk, Kh A

    1985-01-01

    The paper presents data on the level of benzo(a)pyrene (BP) and some other polycyclic arenes in alga and phanerogam specimens from different gulfs of the Baltic Sea. Algae were shown to absorb BP from sea water. The mean concentration of BP in sea water was under 0.004 microgram/1, while in algae it ranged 0.1-21.2 micrograms/kg dry weight. Algae accumulate BP to a higher degree than phanerogams. The highest concentrations of BP were found in algae Enteromorpha while the lowest ones in Furcellaria. In annual green algae, BP level was higher in autumn, i. e. at the end of vegetation period, than in spring. Brown algae Fucus vesiculosus is recommended for monitoring polycyclic arene pollution in the area from Vormsi Island to Käsmu and green algae Cladophora or Enteromorpha in the eastern part of the Finnish Gulf. PMID:4060672

  4. Iron-catalyzed electrochemical C-H perfluoroalkylation of arenes.

    PubMed

    Khrizanforov, Mikhail; Strekalova, Sofia; Khrizanforova, Vera; Grinenko, Valeriya; Kholin, Kirill; Kadirov, Marsil; Burganov, Timur; Gubaidullin, Aidar; Gryaznova, Tatyana; Sinyashin, Oleg; Xu, Long; Vicic, David A; Budnikova, Yulia

    2015-12-01

    A new iron-catalyzed reaction for the coupling of perfluoroalkyl iodides (RFI) with aromatic substrates is described. The perfluoroalkylated arene products are obtained in good to excellent yields in the presence of a [(bpy)Fe(ii)] catalyst (10%) electrochemically regenerated or generated from [(bpy)Fe(iii)] at room temperature. The development, scope, and preliminary mechanistic studies of these transformations are reported. PMID:26459803

  5. Calix[4]arene Based Single-Molecule Magnets

    SciTech Connect

    Karotsis, Georgios; Teat, Simon J.; Wernsdorfer, Wolfgang; Piligkos, Stergios; Dalgarno, Scott J.; Brechin, Euan K.

    2009-06-04

    Single-molecule magnets (SMMs) have been the subject of much interest in recent years because their molecular nature and inherent physical properties allow the crossover between classical and quantum physics to be observed. The macroscopic observation of quantum phenomena - tunneling between different spin states, quantum interference between tunnel paths - not only allows scientists to study quantum mechanical laws in great detail, but also provides model systems with which to investigate the possible implementation of spin-based solid state qubits and molecular spintronics. The isolation of small, simple SMMs is therefore an exciting prospect. To date almost all SMMs have been made via the self-assembly of 3d metal ions in the presence of bridging/chelating organic ligands. However, very recently an exciting new class of SMMs, based on 3d metal clusters (or single lanthanide ions) housed within polyoxometalates, has appeared. These types of molecule, in which the SMM is completely encapsulated within (or shrouded by) a 'protective' organic or inorganic sheath have much potential for design and manipulation: for example, for the removal of unwanted dipolar interactions, the introduction of redox activity, or to simply aid functionalization for surface grafting. Calix[4]arenes are cyclic (typically bowl-shaped) polyphenols that have been used extensively in the formation of versatile self-assembled supramolecular structures. Although many have been reported, p-{sup t}But-calix[4]arene and calix[4]arene (TBC4 and C4 respectively, Figure 1A) are frequently encountered due to (a) synthetic accessibility, and (b) vast potential for alteration at either the upper or lower rim of the macrocyclic framework. Within the field of supramolecular chemistry, TBC4 is well known for interesting polymorphic behavior and phase transformations within anti-parallel bi-layer arrays, while C4 often forms self-included trimers. The polyphenolic nature of calix[n]arenes (where n = 4

  6. Tuning reactivity and site selectivity of simple arenes in C-H activation: ortho-arylation of anisoles via arene-metal π-complexation.

    PubMed

    Ricci, Paolo; Krämer, Katrina; Larrosa, Igor

    2014-12-31

    Current approaches to achieve site selectivity in the C-H activation of arenes involve the use of directing groups or highly electron-poor arenes. In contrast, simple arenes, such as anisole, are characterized by poor reactivity and selectivity. We report that π-complexation to a Cr(CO)3 unit enhances the reactivity of anisoles providing an unprecedented ortho-selective arylation. This mild methodology can be used for the late stage functionalization of bioactive compounds containing the anisole motif, allowing the construction of novel organic scaffolds with few synthetic steps. PMID:25510851

  7. Cellular delivery of pyrenyl-arene ruthenium complexes by a water-soluble arene ruthenium metalla-cage.

    PubMed

    Furrer, Mona Anca; Schmitt, Frédéric; Wiederkehr, Michaël; Juillerat-Jeanneret, Lucienne; Therrien, Bruno

    2012-06-28

    Three pyrenyl-arene ruthenium complexes (M(1)-M(3)) of the general formula [Ru(η(6)-arene-pyrenyl)Cl(2)(pta)] (pta = 1,3,5-triaza-7-phosphaadamantane) have been synthesised and characterised. Prior to the coordination to ruthenium, pyrene was connected to the arene ligand via an alkane chain containing different functional groups: ester (L(1)), ether (L(2)) and amide (L(3)), respectively. Furthermore, the pyrenyl moieties of the M(n) complexes were encapsulated within the hydrophobic cavity of the water soluble metalla-cage, [Ru(6)(η(6)-p-cymene)(6)(tpt)(2)(donq)(3)](6+) (tpt = 2,4,6-tri-(pyridin-4-yl)-1,3,5-triazine; donq = 5,8-dioxydo-1,4-naphthoquinonato), while the arene ruthenium end was pointing out of the cage, thus giving rise to the corresponding host-guest systems [M(n)⊂Ru(6)(η(6)-p-cymene)(6)(tpt)(2)(donq)(3)](6+) ([M(n)⊂cage](6+)). The antitumor activity of the pyrenyl-arene ruthenium complexes (M(n)) and the corresponding host-guest systems [M(n)⊂cage][CF(3)SO(3)](6) were evaluated in vitro in different types of human cancer cell lines (A549, A2780, A2780cisR, Me300 and HeLa). Complex M(2), which contains an ether group within the alkane chain, demonstrated at least a 10 times higher cytotoxicity than the reference compound [Ru(η(6)-p-cymene)Cl(2)(pta)] (RAPTA-C). All host-guest systems [M(n)⊂cage](6+) showed good anticancer activity with IC(50) values ranging from 2 to 8 μM after 72 h exposure. The fluorescence of the pyrenyl moiety allowed the monitoring of the cellular uptake and revealed an increase of uptake by a factor two of the M(2) complex when encapsulated in the metalla-cage [Ru(6)(η(6)-p-cymene)(6)(tpt)(2)(donq)(3)](6+). PMID:22506276

  8. Spectroscopic investigation of the interaction of water-soluble azocalix[4]arenes with bovine serum albumin.

    PubMed

    Fan, Ping; Wan, Lu; Shang, Yunshan; Wang, Jun; Liu, Yulong; Sun, Xiaoyu; Chen, Chen

    2015-02-01

    In this work, three hydrosoluble azocalix[4]arene derivatives, 5-(o-methylphenylazo)-25,26,27-tris(carboxymethoxy)-28-hydroxycalix[4]arene (o-MAC-Calix), 5-(m-methylphenylazo)-25,26,27-tris(carboxymethoxy)-28-hydroxycalix[4]arene (m-MAC-Calix) and 5-(p-methylphenylazo)-25,26,27-tris(carboxymethoxy)-28-hydroxycalix[4]arene (p-MAC-Calix) were synthesized. Their structures were characterized by infrared spectrum (IR), nuclear magnetic resonance spectrum (1H NMR and 13C NMR) and mass spectrum (MS). The interactions between these compounds and bovine serum albumin (BSA) were studied by fluorescence spectroscopy, UV-vis spectrophotometry and circular dichroic spectroscopy. According to experimental results, three azocalix[4]arene derivatives can efficiently bind to BSA molecules and the o-MAC-Calix displays more efficient interactions with BSA molecules than m-MAC-Calix and p-MAC-Calix. Molecular docking showed that the o-MAC-Calix was embedded in the hydrophobic cavity of helical structure of BSA molecular and the tryptophan (Trp) residue of BSA molecular had strong interaction with o-MAC-Calix. The fluorescence quenching of BSA caused by azocalix[4]arene derivatives is attributed to the static quenching process. In addition, the synchronous fluorescence spectroscopy indicates that these azocalix[4]arene derivatives are more accessible to Trp residues of BSA molecules than the tyrosine (Tyr) residues. The circular dichroic spectroscopy further verified the binding of azocalix[4]arene derivatives and BSA. PMID:25549320

  9. Glued Langmuir-Blodgett bilayers from calix[n]arenes: Influence of calix[n]arene size on ionic cross-linking, film thickness, and permeation selectivity

    DOE PAGESBeta

    Wang, Minghui; Janout, Vaclav; Regen, Steven L.

    2010-07-12

    A homologous series of calix[4]arene-, calix[5]arene- and calix[6]arene-based surfactants, containing pendant trimethylammonium and n-hexadecyl groups, have been compared with respect to their ability (i) to undergo ionic crosslinking at the air/water interface, (ii) to incorporate poly(4-styrenesulfonate) (PSS) in Langmuir-Blodgett (LB) bilayers, and (iii) to act as barriers towards He, N2 and CO2 when assembled into crosslinked LB bilayers. As these calix[n]arenes increase in size, their ability to undergo ionic crosslinking has been found to increase, the thickness of corresponding glued LB bilayers has been found to decrease, and their barrier properties and permeation selectivities have been found to increase. Inmore » conclusion, the likely origin for these effects and the probable mechanism by which He, N2 and CO2 cross these ultrathin films are discussed.« less

  10. C-F Activation in Perfluorinated Arenes with Isonitriles under UV-Light Irradiation.

    PubMed

    Dewanji, Abhishek; Mück-Lichtenfeld, Christian; Bergander, Klaus; Daniliuc, Constantin G; Studer, Armido

    2015-08-24

    Due to the great value of fluorinated arenes in agrochemistry, medicinal chemistry and materials science, development of methods for preparation of fluorinated arenes is of high importance. They can be either accessed by arene fluorination or by partial arene defluorination. However, the carbon-fluorine bond belongs to the strongest σ-bonds, which renders C-F activation highly challenging. Here it is shown that aryl and alkyl isonitriles efficiently activate the strong C-F bond in perfluoroarenes by simple UV irradiation under mild conditions. Reactions proceed by formal direct insertion of the isonitrile into the C-F bond without any transition metal. Activation occurs at arene C-F bonds whereas aliphatic C-F bonds remain unreacted. For selected perfluoroarenes C-F activation occurs with high regioselectivity and resulting imidoyl fluorides are transformed into other valuable compounds. Theoretical studies give insights into the reaction mechanism. PMID:26189958

  11. para-Sulphonato-calix[n]arenes as selective activators for the passage of molecules across the Caco-2 model intestinal membrane.

    PubMed

    Roka, Eszter; Vecsernyes, Miklos; Bacskay, Ildiko; Félix, Caroline; Rhimi, Moez; Coleman, Anthony W; Perret, Florent

    2015-06-01

    The passage of Lucifer Yellow across the Caco-2 intestinal model membrane has been studied for the para-sulphonato-calix[n]arenes, the results show that para-sulphonato-calix[4]arene and para-sulphonato-calix[8]arene activate membrane passage when used simultaneously with a transport probe, Lucifer Yellow, whereas para-sulphonato-calix[6]arene has no effect. PMID:25958962

  12. Visible-light-initiated difluoromethylation of arene diazonium tetrafluoroborates.

    PubMed

    Wu, Ye-Bin; Lu, Guo-Ping; Zhou, Bao-Jing; Bu, Mei-Jie; Wan, Li; Cai, Chun

    2016-05-21

    A mild and efficient method for the radical addition of α-aryl-β,β-difluoroenol silyl with arene diazonium tetrafluoroborates at room temperature has been disclosed, which involves an innate radical long chain cycle, so only a small amount (0.05 mol%) of photocatalyst and a short light exposure time are required as radical initiators. A proposed mechanism for the transformation is also illustrated based on the results of control experiments and quantum calculations. A variety of α-aryl-α,α-difluoroketones were formed in moderate to high yields, and can be easily further transformed into various difluoromethylarenes under basic conditions. PMID:27055723

  13. Mixed-Monolayer-Protected Au25 Clusters with Bulky Calix[4]arene Functionalities.

    PubMed

    Hassinen, Jukka; Pulkkinen, Petri; Kalenius, Elina; Pradeep, Thalappil; Tenhu, Heikki; Häkkinen, Hannu; Ras, Robin H A

    2014-02-01

    Although various complex, bulky ligands have been used to functionalize plasmonic gold nanoparticles, introducing them to small, atomically precise gold clusters is not trivial. Here, we demonstrate a simple one-pot procedure to synthesize fluorescent magic number Au25 clusters carrying controlled amounts of bulky calix[4]arene functionalities. These clusters are obtained from a synthesis feed containing binary mixtures of tetrathiolated calix[4]arene and 1-butanethiol. By systematic variation of the molar ratio of ligands, clusters carrying one to eight calixarene moieties were obtained. Structural characterization reveals unexpected binding of the calix[4]arenes to the Au25 cluster surface with two or four thiolates per moiety. PMID:26276613

  14. Immobilization of [60]fullerene on silicon surfaces through a calix[8]arene layer

    SciTech Connect

    Busolo, Filippo; Silvestrini, Simone; Maggini, Michele; Armelao, Lidia

    2013-10-28

    In this work, we report the functionalization of flat Si(100) surfaces with a calix[8]arene derivative through a thermal hydrosilylation process, followed by docking with [60]fullerene. Chemical grafting of calix[8]arene on silicon substrates was evaluated by X-ray photoelectron spectroscopy, whereas host-guest immobilization of fullerene was demonstrated by atomic force microscopy and sessile drop water contact angle measurements. Surface topographical variations, modelled on the basis of calix[8]arene and [60]fullerene geometrical parameters, are consistent with the observed morphological features relative to surface functionalization and to non-covalent immobilization of [60]fullerene.

  15. Gas Concentration Mapping of Arenal Volcano Using AVEMS

    NASA Technical Reports Server (NTRS)

    Diaz, J. Andres; Arkin, C. Richard; Griffin, Timothy P.; Conejo, Elian; Heinrich, Kristel; Soto, Carlomagno

    2005-01-01

    The Airborne Volcanic Emissions Mass Spectrometer (AVEMS) System developed by NASA-Kennedy Space Center and deployed in collaboration with the National Center for Advanced Technology (CENAT) and the University of Costa Rica was used for mapping the volcanic plume of Arenal Volcano, the most active volcano in Costa Rica. The measurements were conducted as part of the second CARTA (Costa Rica Airborne Research and Technology Application) mission conducted in March 2005. The CARTA 2005 mission, involving multiple sensors and agencies, consisted of three different planes collecting data over all of Costa Rica. The WB-57F from NASA collected ground data with a digital camera, an analog photogrametric camera (RC-30), a multispectral scanner (MASTER) and a hyperspectral sensor (HYMAP). The second aircraft, a King Air 200 from DoE, mounted with a LIDAR based instrument, targeted topography mapping and forest density measurements. A smaller third aircraft, a Navajo from Costa Rica, integrated with the AVEMS instrument and designed for real-time measurements of air pollutants from both natural and anthropogenic sources, was flown over the volcanoes. The improved AVEMS system is designed for deployment via aircraft, car or hand-transport. The 85 pound system employs a 200 Da quadrupole mass analyzer, has a volume of 92,000 cubic cm, requires 350 W of power at steady state, can operate up to an altitude of 41,000 feet above sea level (-65 C; 50 torr). The system uses on-board gas bottles on-site calibration and is capable of monitoring and quantifying up to 16 gases simultaneously. The in-situ gas data in this work, consisting of helium, carbon dioxide, sulfur dioxide and acetone, was acquired in conjunction of GPS data which was plotted with the ground imagery, topography and remote sensing data collected by the other instruments, allowing the 3 dimensional visualization of the volcanic plume at Arenal Volcano. The modeling of possible scenarios of Arenal s activity and its

  16. Study: Ex-NFL Players Aren't At Greater Risk for Suicide

    MedlinePlus

    ... 2016 WEDNESDAY, May 11, 2016 (HealthDay News) -- Professional football players aren't at greater risk of suicide ... suicide death rate for 3,439 retired National Football League players who played for at least five ...

  17. Arene-metal π-complexation as a traceless reactivity enhancer for C-H arylation.

    PubMed

    Ricci, Paolo; Krämer, Katrina; Cambeiro, Xacobe C; Larrosa, Igor

    2013-09-11

    Current approaches to facilitate C-H arylation of arenes involve the use of either strongly electron-withdrawing substituents or directing groups. Both approaches require structural modification of the arene, limiting their generality. We present a new approach where C-H arylation is made possible without altering the connectivity of the arene via π-complexation of a Cr(CO)3 unit, greatly enhancing the reactivity of the aromatic C-H bonds. We apply this approach to monofluorobenzenes, highly unreactive arenes, which upon complexation become nearly as reactive as pentafluorobenzene itself in their couplings with iodoarenes. DFT calculations indicate that C-H activation via a concerted metalation-deprotonation transition state is facilitated by the predisposition of C-H bonds in (Ar-H)Cr(CO)3 to bend out of the aromatic plane. PMID:23962336

  18. A General Method for Copper-Catalyzed Arene Cross-Dimerization

    PubMed Central

    Do, Hien-Quang; Daugulis, Olafs

    2011-01-01

    A general method for a highly regioselective, copper-catalyzed cross-coupling of two aromatic compounds by using iodine oxidant has been developed. The reactions involve an initial iodination of one arene followed by arylation of the most acidic C-H bond of the other coupling component. Cross-coupling of electron-rich arenes, electron-poor arenes, five- and six-membered heterocycles is possible in many combinations. Typically, 1/1.5 to 1/3 ratio of coupling components is used in contrast to existing methodology that often employs a large excess of one of the arenes. Common functionalities such as ester, ketone, aldehyde, ether, nitrile, nitro, and amine are well-tolerated. PMID:21823581

  19. Functionalized O6-Corona[6]arenes: Synthesis, Structure, and Fullerene Complexation Property.

    PubMed

    Ren, Wen-Sheng; Zhao, Liang; Wang, Mei-Xiang

    2016-07-01

    The synthesis, structure, and fullerene complexation property of novel and functionalized On-corona[n]arenes were reported. Based on the fragment coupling strategy, ester-containing On-corona[n]arenes (n = 6, 8) were obtained readily starting from 1,4-hydroquinone and diethyl 2,5-difluoroterephthalate. Reduction of esters with LiAlH4 produced almost quantitatively hydroxymethylated On-corona[n]arenes, which underwent etherification with MeI to afford methoxymethyl-substituted On-corona[n]arenes (n = 6, 8) in good yields. The macrocycles adopt unique corona-type conformation with a large cylindroid cavity. They are strong macrocyclic host molecules to form 1:1 complexes with fullerenes C60 and C70 in toluene with an associate constant up to (1.59 ± 0.04) × 10(5) M(-1). PMID:27324274

  20. Irritable Bowel Syndrome Treatments Aren't One-Size-Fits-All

    MedlinePlus

    ... Bowel Syndrome Treatments Aren't One-Size-Fits-All Share Tweet Linkedin Pin it More sharing options ... the United States. No one remedy works for all patients, so there’s a great medical need to ...

  1. Manganese-Mediated C-H Alkylation of Unbiased Arenes Using Alkylboronic Acids.

    PubMed

    Castro, Susana; Fernández, Juan J; Fañanás, Francisco J; Vicente, Rubén; Rodríguez, Félix

    2016-06-27

    The alkylation of arenes is an essential synthetic step of interest not only from the academic point of view but also in the bulk chemical industry. Despite its limitations, the Friedel-Crafts reaction is still the method of choice for most of the arene alkylation processes. Thus, the development of new strategies to synthesize alkyl arenes is a highly desirable goal, and herein, we present an alternative method to those conventional reactions. Particularly, a simple protocol for the direct C-H alkylation of unbiased arenes with alkylboronic acids in the presence of Mn(OAc)3 ⋅2H2 O is reported. Primary or secondary unactivated alkylboronic acids served as alkylating agents for the direct functionalization of representative polyaromatic hydrocarbons (PAHs) or benzene. The results are consistent with a free-radical mechanism. PMID:27124250

  2. Synthesis and Characterization of Mesoporous Silica Functionalized with Calix[4]arene Derivatives

    PubMed Central

    Alahmadi, Sana M.; Mohamad, Sharifah; Maah, Mohd Jamil

    2012-01-01

    This work reports a new method to covalently attach calix[4]arene derivatives onto MCM-41, using a diisocyanate as a linker. The modified mesoporous silicates were characterized by fourier transform infrared spectroscopy (FTIR), thermal analysis (TGA) and elemental analysis. The FTIR spectra and TGA analysis verified that the calix[4]arene derivates are covalently attached to the mesoporous silica. The preservation of the MCM-41 channel system was checked by X-ray diffraction and nitrogen adsorption analysis. PMID:23202977

  3. Pillar-Shaped Macrocyclic Hosts Pillar[n]arenes: New Key Players for Supramolecular Chemistry.

    PubMed

    Ogoshi, Tomoki; Yamagishi, Tada-Aki; Nakamoto, Yoshiaki

    2016-07-27

    In 2008, we reported a new class of pillar-shaped macrocyclic hosts, known as "pillar[n]arenes". Today, pillar[n]arenes are recognized as key players in supramolecular chemistry because of their facile synthesis, unique pillar shape, versatile functionality, interesting host-guest properties, and original supramolecular assembly characteristics, which have resulted in numerous electrochemical and biomedical material applications. In this Review, we have provided historical background to macrocyclic chemistry, followed by a detailed discussion of the fundamental properties of pillar[n]arenes, including their synthesis, structure, and host-guest properties. Furthermore, we have discussed the applications of pillar[n]arenes to materials science, as well as their applications in supramolecular chemistry, in terms of their fundamental properties. Finally, we have described the future perspectives of pillar[n]arene chemistry. We hope that this Review will provide a useful reference for researchers working in the field and inspire discoveries concerning pillar[n]arene chemistry. PMID:27337002

  4. A route for lignin and bio-oil conversion: dehydroxylation of phenols into arenes by catalytic tandem reactions.

    PubMed

    Wang, Xingyu; Rinaldi, Roberto

    2013-10-25

    Finding a workaround: The conversion of lignin into low-boiling-point arenes instead of high-boiling-point phenols could greatly facilitate conventional refinery processes. A new procedure for the depolymerization of lignin and simultaneous conversion phenols into arenes is described. The method can also be rendered as a fundamental finding for the upgrade of bio-oils to arenes under mild conditions. PMID:24030931

  5. Rhodium(III)-Catalyzed Mild Alkylation of (Hetero)Arenes with Cyclopropanols via C-H Activation and Ring Opening.

    PubMed

    Zhou, Xukai; Yu, Songjie; Qi, Zisong; Kong, Lingheng; Li, Xingwei

    2016-06-01

    The rhodium(III)-catalyzed regioselective alkylation of (hetero)arenes using cyclopropanols as a reactive and efficient coupling partner under oxidative conditions has been developed. This coupling occurred at room temperature via C-H activation of arenes and C-C cleavage of cyclopropanols. Various types of (hetero)arenes (indolines, carbazole, tetrahydrocarbazole, pyrrole, thiophene, etc.) were all successfully reacted under the present conditions. This protocol provides the facile and efficient construction of C7-alkylated indoline scaffolds. PMID:27166521

  6. Recent advances in pillar[n]arenes: synthesis and applications based on host-guest interactions.

    PubMed

    Yang, Kui; Pei, Yuxin; Wen, Jia; Pei, Zhichao

    2016-07-19

    Pillar[n]arenes (n = 5-15) are a novel class of macrocyclic molecules with hydroquinone as the repeating unit linked by methylene bridges at para-positions. Introduced by T. Ogoshi for the first time in 2008, pillararenes have attracted increasing interest and have been widely studied during the last eight years, due to their unique structural advantages as host molecules, such as symmetrical rigid architecture, electron-rich cavities and facile functional modification. In this review, we first describe the syntheses of pillar[n]arenes including cyclooligomerization of pillar[n]arenes and modification of pillar[n]arenes after cyclooligomerization, summarising almost twenty different kinds of guest motifs and dividing them into three types: cationic, neutral and anionic motifs. The main section of this review examines the applications of pillar[n]arenes based on the host-guest interactions in different research fields, including biology, materials science and environmental science. Finally, future research directions and potential for novel applications are discussed. PMID:27332040

  7. X-ray guided 1H NMR analysis of pinched cone calix[4]arenes

    NASA Astrophysics Data System (ADS)

    Rashatasakhon, Paitoon; Jaiyu, Arisa; Rojanathanes, Rojrit; Muangsin, Nongnuj; Chaichit, Narongsak; Sukwattanasinitt, Mongkol

    2010-01-01

    The analysis of structural parameters of azobenzene- and stilbene-bridged calix[4]arene obtained from AM1 calculation are in good agreement with those obtained from X-ray crystallography. The bridge longer than 9.0 Å such as p,p- trans-azobenzene and p,p- trans-stilbene cannot be constructed over the narrow rim of calix[4]arene through two ethylene oxide linkers. The m,m-stilbene bridge is the most promising photo switch because its shorter cis stereoisomer (5.85 Å) allows calix[4]arene to assume the perfect cone conformation, whilst its longer trans stereoisomer (8.00 Å) forces calix[4]arene to adapt a pinched cone conformation. The pinched cone conformation has longer distances between the neighbouring phenoxyl groups causing the weaker intramolecular hydrogen bonding and the upfield shifts of the phenolic proton signals to below 7.00 ppm. This upfield shift is useful for quick identification of pinched cone conformation of new calix[4]arene compounds.

  8. Multipoint molecular recognition within a calix[6]arene funnel complex

    PubMed Central

    Coquière, David; de la Lande, Aurélien; Martí, Sergio; Parisel, Olivier; Prangé, Thierry; Reinaud, Olivia

    2009-01-01

    A multipoint recognition system based on a calix[6]arene is described. The calixarene core is decorated on alternating aromatic subunits by 3 imidazole arms at the small rim and 3 aniline groups at the large rim. This substitution pattern projects the aniline nitrogens toward each other when Zn(II) binds at the Tris-imidazole site or when a proton binds at an aniline. The XRD structure of the monoprotonated complex having an acetonitrile molecule bound to Zn(II) in the cavity revealed a constrained geometry at the metal center reminiscent of an entatic state. Computer modeling suggests that the aniline groups behave as a tritopic monobasic site in which only 1 aniline unit is protonated and interacts with the other 2 through strong hydrogen bonding. The metal complex selectively binds a monoprotonated diamine vs. a monoamine through multipoint recognition: coordination to the metal ion at the small rim, hydrogen bonding to the calix-oxygen core, CH/π interaction within the cavity's aromatic walls, and H-bonding to the anilines at the large rim. PMID:19237564

  9. Catalysis alkene and arene hydrogenation by thermally activated silica

    SciTech Connect

    Rajagopal, V.; Guthrie, R.D.; Davis, B.H.

    1995-12-31

    Bittner, Bockrath and Solar have reported that thermal activation of fumed silica at 320{degrees}C under argon flow introduces catalytic activity for the reactions H{sub 2} + D{sub 2} {yields} 2 HD and D{sub 2} + CH{sub 2}=CH{sub 2} {yields} CH{sub 2}DCH{sub 2}D {yields} CD{sub 3}CD{sub 3}. Using the Bittner catalyst in a glass-walled, tube reactor we hydrogenate bulk samples of alkenes and arenes using D{sub 2} at pressures of 10-14 MPa and >300{degrees}C. Activation is required. Compounds hydrogenated include, stilbene, nonene, anthracene and diphenylacetylene. The aromatic rings of naphthalene, biphenyl and bibenzyl are partially hydrogenated on prolonged treatment at 350{degrees}C. At threshold temperature for the hydrogenation of diphenylacetylene, the less-stable cis-stilbene is formed faster than it proceeds to the predominantly transequilibrium mixture. Surface OH groups on the silica undergo complete equilibration to OD under our reaction conditions. However, only a barely-measurable trace of D-atom addition occurs when D{sub 2}-equilibrated silica is heated with stilbene after D{sub 2} removal.

  10. Phenyl shifts in substituted arenes via ipso arenium ions.

    PubMed

    Ajaz, Aida; McLaughlin, Erin C; Skraba, Sarah L; Thamatam, Rajesh; Johnson, Richard P

    2012-11-01

    The isomerization of substituted arenes through ipso arenium ions is an important and general molecular rearrangement that leads to interconversions of constitutional isomers. We show here that the superacid trifluoromethanesulfonic acid (TfOH), ca. 1 M in dichloroethane (DCE), provides reliable catalytic reaction conditions for these rearrangements, easily applied at ambient temperature, reflux (84 °C), or in a microwave reactor for higher temperatures. Interconversion of terphenyl isomers in TfOH/DCE at 84 °C gives an ortho/meta/para equilibrium ratio of 0:65:35, nearly identical to values reported earlier by Olah with catalysis by AlCl(3). For the three triphenylbenzenes, TfOH-catalyzed equilibration strongly (>95%) favors the 1,3,5-triphenyl isomer. Equilibration of the three possible tetraphenylbenzenes gives a 61:39 mixture of the 1,2,3,5- and 1,2,4,5-substituted isomers. Under the reaction conditions explored, none of these structures undergoes significant Scholl cyclization. DFT calculations with inclusion of solvation support a mechanistic scheme in which all of the phenyl migrations occur among a series of ipso arenium ions. In every case studied, the preferred isomers at equilibrium are those that yield highly stable cations by the most exothermic, hence least reversible 1,2-H shift. PMID:23061916

  11. Spectroscopic investigations of ADMA encapsulated in pyrogallol[4]arene nanocapsules.

    PubMed

    Bassil, Daniel B; Dalgarno, Scott J; Cave, Gareth W V; Atwood, Jerry L; Tucker, Sheryl A

    2007-08-01

    Pyrogallol[4]arenes form stable hydrogen-bonded nanocapsules that have unique properties that may make them suitable for diverse applications, such as catalysts and molecular transporters. Little is known about the behavior of the interior of these new materials in solution, and by using the solvent-dependent properties of 1-(9-anthryl)-3-(4-dimethylaniline) propane (ADMA), the inner phase properties of the hexamers are investigated. Steady-state and dynamic spectrofluorometric results are in agreement, are consistent with solid-state studies, and indicate that the majority of ADMA is sequestered in an extended conformation with the crystallization solvent. The conformational flexibility of ADMA is attributed to lower capsule occupancies ( approximately 50%, i.e., 1 molecule per 2 capsules, one occupied and one empty) relative to our previous study with pyrene butyric acid (occupancy of 150%, i.e., 1.5 molecules per capsule) in which the probe was restricted within a nanocapsule. The nature of the encapsulated ADMA complexes are found to change with time, as there is either fluorophore leaching from the capsule or endo-exo-capsule solvent exchange. However, the choice of crystallizing solvent (ethyl acetate or acetonitrile) and PgC(n) alkyl tail (C(6) or C(10)) does not influence experimental outcomes. These research findings give a better understanding of the encapsulation versatility of these unique supramolecular assemblies and the protective nanopockets that can exist for guest molecules. PMID:17602580

  12. Investigations into Transition Metal Catalyzed Arene Trifluoromethylation Reactions

    PubMed Central

    Ye, Yingda; Sanford, Melanie S.

    2015-01-01

    Trifluoromethyl-substituted arenes and heteroarenes are widely prevalent in pharmaceuticals and agrochemicals. As a result, the development of practical methods for the formation of aryl–CF3 bonds has become an active field of research. Over the past five years, transition metal catalyzed cross-coupling between aryl–X (X = halide, organometallic, or H) and various “CF3” reagents has emerged as a particularly exciting approach for generating aryl–CF3 bonds. Despite many recent advances in this area, current methods generally suffer from limitations such as poor generality, harsh reaction conditions, the requirement for stoichiometric quantities of metals, and/or the use of costly CF3 sources. This Account describes our recent efforts to address some of these challenges by: (1) developing aryl trifluoromethylation reactions involving high oxidation state Pd intermediates, (2) exploiting AgCF3 for C–H trifluoromethylation, and (3) achieving Cu-catalyzed trifluoromethylation with photogenerated CF3•. PMID:25838638

  13. Trifluoromethylation of arenes and heteroarenes by means of photoredox catalysis

    PubMed Central

    Nagib, David A.; MacMillan, David W. C.

    2012-01-01

    Modern drug discovery relies on the continual development of synthetic methodology to address the many challenges associated with the design of new pharmaceutical agents1. One such challenge arises from the enzymatic metabolism of drugs in vivo by cytochrome P450 oxidases, which use single-electron oxidative mechanisms to rapidly modify small molecules to facilitate their excretion2. A commonly used synthetic strategy to protect against in vivo metabolism involves the incorporation of electron-withdrawing functionality, such as the trifluoromethyl (CF3) group, into drug candidates3. The CF3 group enjoys a privileged role in the realm of medicinal chemistry because its incorporation into small molecules often enhances efficacy by promoting electrostatic interactions with targets, improving cellular membrane permeability, and increasing robustness towards oxidative metabolism of the drug4–6. Although common pharmacophores often bear CF3 motifs in an aromatic system, access to such analogues typically requires the incorporation of the CF3 group, or a surrogate moiety, at the start of a multi-step synthetic sequence. Here we report a mild, operationally simple strategy for the direct trifluoromethylation of unactivated arenes and heteroarenes through a radical-mediated mechanism using commercial photocatalysts and a household light bulb. We demonstrate the broad utility of this transformation through addition of CF3 to a number of heteroaromatic and aromatic systems. The benefit to medicinal chemistry and applicability to late-stage drug development is also shown through examples of the direct trifluoromethylation of widely prescribed pharmaceutical agents. PMID:22158245

  14. Access to Electron-Rich Arene-Fused Hexahydroquinolizinones via A Gold Catalysis-Triggered Cascade Process

    PubMed Central

    Liu, Lianzhu; Zhang, Liming

    2012-01-01

    Golden Cascade? Using a tethered, electron-rich arene as the internal nucleophile, a gold catalyzed amide cyclization to an alkyne serves as the trigger of a cascade process that ends with a Ferrier rearrangement. Electron-rich arene-fused hexahydroqinolizin-2-ones are formed in good yields and can be converted into indole alkaloids in short orders. PMID:22692916

  15. Improvement of catalytic activity of lipase in the presence of calix[4]arene valeric acid or hydrazine derivative.

    PubMed

    Akoz, Enise; Sayin, Serkan; Kaplan, Selcuk; Yilmaz, Mustafa

    2015-03-01

    Sol-gel encapsulation is a simple but powerful method to enhance the enantioselectivity of lipase-catalyzed transformations in an isooctane/aqueous buffer solution. Candida rugosa lipase was encapsulated according to a sol-gel procedure in the presence and absence of calix[4]arene hydrazine or carboxylic acid derivatives with Fe3O4 magnetic nanoparticles as an additive. The activity of the encapsulated lipases was evaluated for the enantioselective hydrolysis of racemic Naproxen methyl ester and the hydrolysis of p-Nitrophenylpalmitate. The results indicate that the encapsulated lipase without calix[4]arene derivative has lower conversion and enantioselectivity compared to the encapsulated lipase with calix[4]arene derivative. It was found that the calix[4]arene hydrazine and carboxylic acid-based encapsulated lipases have excellent activity and enantioselectivity (E >300) compared to encapsulated lipase without the calix[4]arene derivatives. PMID:25326059

  16. The synthesis, lipophilicity and cytotoxic effects of new ruthenium(II) arene complexes with chromone derivatives.

    PubMed

    Pastuszko, Adam; Majchrzak, Kinga; Czyz, Malgorzata; Kupcewicz, Bogumiła; Budzisz, Elzbieta

    2016-06-01

    A series of arene ruthenium(II) complexes with the general formula [(η(6)-arene)Ru(L)X2] (where arene=p-cymene, benzene, hexamethylbenzene or mesitylene, L=aminoflavone or aminochromone derivatives and X=Cl, I) were synthesized and characterized by elemental analysis, MS, IR and (1)H NMR spectroscopy. The stability of the selected complexes was assessed by UV-Vis spectroscopy in 24-hour period. The lipophilicity of the synthesized complexes was determined by the shake-flask method, and their cytotoxicity evaluated in vitro on patient-derived melanoma populations. The most active complexes against melanoma cells contain 7-aminoflavone and 6-aminoflavone as a ligand. The relationship between the cytotoxicity of all the obtained compounds and their logP values was determined and briefly analyzed with two different patterns observed. PMID:26986980

  17. Palladium-Catalyzed Trifluoromethylation of (Hetero)Arenes with CF3 Br.

    PubMed

    Natte, Kishore; Jagadeesh, Rajenahally V; He, Lin; Rabeah, Jabor; Chen, Jianbin; Taeschler, Christoph; Ellinger, Stefan; Zaragoza, Florencio; Neumann, Helfried; Brückner, Angelika; Beller, Matthias

    2016-02-18

    The CF3 group is an omnipresent motif found in many pharmaceuticals, agrochemicals, catalysts, materials, and industrial chemicals. Despite well-established trifluoromethylation methodologies, the straightforward and selective introduction of such groups into (hetero)arenes using available and less expensive sources is still a major challenge. In this regard, the selective synthesis of various trifluoromethyl-substituted (hetero)arenes by palladium-catalyzed C-H functionalization is herein reported. This novel methodology proceeds under comparably mild reaction conditions with good regio- and chemoselectivity. As examples, trifluoromethylations of biologically important molecules, such as melatonin, theophylline, caffeine, and pentoxifylline, are showcased. PMID:26804330

  18. Silver(I)-Catalyzed Iodination of Arenes: Tuning the Lewis Acidity of N-Iodosuccinimide Activation.

    PubMed

    Racys, Daugirdas T; Sharif, Salaheddin A I; Pimlott, Sally L; Sutherland, Andrew

    2016-02-01

    A mild and rapid method for the iodination of arenes that utilizes silver(I) triflimide as a catalyst for activation of N-iodosuccinimide has been developed. The transformation was found to be general for a wide range of anisole, aniline, acetanilide, and phenol derivatives and allowed the late-stage iodination of biologically active compounds such as PIMBA, a SPECT imaging agent of breast cancer, and (-)-IBZM, a dopamine D2 receptor antagonist. The method was also modified for the radioiodination of arenes using a one-pot procedure involving the in situ generation of [(125)I]-N-iodosuccinimide followed by the silver(I)-catalyzed iodination. PMID:26795534

  19. Double Heteroatom Functionalization of Arenes Using Benzyne Three‐Component Coupling†

    PubMed Central

    García‐López, José‐Antonio; Çetin, Meliha

    2015-01-01

    Abstract Arynes participate in three‐component coupling reactions with N, S, P, and Se functionalities to yield 1,2‐heteroatom‐difunctionalized arenes. Using 2‐iodophenyl arylsulfonates as benzyne precursors, we could effectively add magnesiated S‐, Se‐, and N‐nucleophilic components to the strained triple bond. In the same pot, addition of electrophilic N, S, or P reagents and a copper(I) catalyst trapped the intermediate aryl Grignard to produce a variety of 1,2‐difunctionalized arenes. PMID:25580700

  20. Removal of uranyl ions by p-hexasulfonated calyx[6]arene acid

    NASA Astrophysics Data System (ADS)

    Popescu (Hoştuc), Ioana-Carmen; Petru, Filip; Humelnicu, Ionel; Mateescu, Marina; Militaru, Ecaterina; Humelnicu, Doina

    2014-10-01

    Radioactive pollution is a significant threat for the people’s health. Therefore highly effective radioactive decontamination methods are required. Ion exchange, biotechnologies and phytoremediation in constructed wetlands have been used as radioactive decontamination technologies for uranium contaminated soil and water remediation. Recently, beside those classical methods the calix[n]arenic derivatives’ utilization as radioactive decontaminators has jogged attention. The present work aims to present the preliminary research results of uranyl ion sorption studies on the p-hexasulfonated calyx[6]arenic acid. The effect of temperature, contact time, sorbent amount and uranyl concentration variation on sorption efficiency was investigated. Isotherm models revealed that the sorption process fit better Langmuir isotherm.

  1. Crystal structure of a mono-bridged calix[4]arene.

    PubMed

    Hailu, Shimelis T; Butcher, Ray J; Hudrlik, Paul F; Hudrlik, Anne M

    2015-07-01

    The title compound, 5(2)-[(5-bromo-pent-yl)-oxy]-1(2),1(14),3(5),5(5)-tetra-tert-butyl-1(7),1(8),1(9),1(10)-tetra-hydro-1(6) H,1(16) H-1(4,12)-dibenzo[b,e][1,7]dioxa-cyclo-dodecina-3,5(1,3)-dibenzena-cyclo-hexa-phan-3(2)-ol, C54H73BrO4, was synthesized from the reaction of tert-butyl-calix[4]arene with 1,5-di-bromo-pentane using K2CO3 in CH3CN. The structure consists of a calixarene unit with a five-carbon bridge connecting two proximal phenolic O atoms, and with a bromo-pent-oxy chain on one of the remaining phenolic O atoms. The calixarene unit was found to have a flattened cone conformation with no solvent (or other guest) mol-ecule observed in the cavity. Two of the opposite phenyl rings lean outwards with fold angles of 136.2 (1) and 133.0 (1)° between the rings and the plane of the bridging methyl-ene C atoms, while the other two opposite rings form fold angles of 83.27 (9) and 105.46 (9)°. There is considerable disorder in this mol-ecule. One of the tert-butyl groups is disordered over two conformations with occupancies of 0.527 (5) and 0.473 (5). The bromo-pent-oxy chain is disordered over three configurations with occupancies of 0.418, 0.332 and 0.250. The five-carbon bridge connecting two proximal phenolic O atoms is disordered over two conformations with occupancies of 0.537 (7) and 0.463 (7). PMID:26279864

  2. Crystal structure of a mono-bridged calix[4]arene

    PubMed Central

    Hailu, Shimelis T.; Butcher, Ray J.; Hudrlik, Paul F.; Hudrlik, Anne M

    2015-01-01

    The title compound, 52-[(5-bromo­pent­yl)­oxy]-12,114,35,55-tetra-tert-butyl-17,18,19,110-tetra­hydro-16 H,116 H-1(4,12)-dibenzo[b,e][1,7]dioxa­cyclo­dodecina-3,5(1,3)-dibenzena­cyclo­hexa­phan-32-ol, C54H73BrO4, was synthesized from the reaction of tert-butyl­calix[4]arene with 1,5-di­bromo­pentane using K2CO3 in CH3CN. The structure consists of a calixarene unit with a five-carbon bridge connecting two proximal phenolic O atoms, and with a bromo­pent­oxy chain on one of the remaining phenolic O atoms. The calixarene unit was found to have a flattened cone conformation with no solvent (or other guest) mol­ecule observed in the cavity. Two of the opposite phenyl rings lean outwards with fold angles of 136.2 (1) and 133.0 (1)° between the rings and the plane of the bridging methyl­ene C atoms, while the other two opposite rings form fold angles of 83.27 (9) and 105.46 (9)°. There is considerable disorder in this mol­ecule. One of the tert-butyl groups is disordered over two conformations with occupancies of 0.527 (5) and 0.473 (5). The bromo­pent­oxy chain is disordered over three configurations with occupancies of 0.418, 0.332 and 0.250. The five-carbon bridge connecting two proximal phenolic O atoms is disordered over two conformations with occupancies of 0.537 (7) and 0.463 (7). PMID:26279864

  3. Studies of morphological optical and electrical properties of the MEH-PPV/azo-calix[4]arene composite layers

    NASA Astrophysics Data System (ADS)

    Rouis, A.; Davenas, J.; Bonnamour, I.; Ben Ouada, H.

    2015-10-01

    Thin films of poly[2-methoxy-5-(20-ethylhexyloxy)-1,4 phenylenevinylene] (MEH-PPV), 5,17-bis(4-nitrophenylazo)-26,28-dihydroxy-25,27-di(ethoxycarbonylmethoxy)-calix[4]arene (azo-calix[4]arene) and MEH-PPV doped azo-calix[4]arene, with 30 wt% and 70 wt% doping ratios, were prepared from chloroform solution by spin coating technique on quartz and ITO substrates. Morphological and optical properties of the samples were investigated by scanning electron microscopy (SEM) and UV-visible spectrophotometry techniques, respectively. Further, the charge carrier transport properties and conduction mechanism of the composite MEH-PPV:azo-calix[4]arene thin films based junction were studied by using current-voltage (I-V) characteristics and dielectric spectroscopy technique. I-V characteristic of ITO/MEH-PPV:azo-calix[4]arene/Al devices showed that the space charge limited conduction (SCLC) dominates in the high voltage region. Moreover, frequency dependence of ac conductivity obeys Jonscher's universal power law. Finally, dielectric constant (ε‧), dielectric loss (ε″) and loss tangent (tan δ) were investigated as function of amount of azo-calix[4]arene in the MEH-PPV polymer matrix.

  4. Development of degradative techniques for coal chemistry based on ether cleavage reactions and metal arene chemistry

    SciTech Connect

    Lemke, D.W.

    1988-01-01

    The degradation of C-O and C-C bonds have been examined using model compounds that are similar in structure to those found in coal and other natural products. The conditions to maximize ether cleavage and minimize the formation of undesirable side products were determined by varying the concentration of reagents, temperature, and reaction time. 2-Phenoxynaphthalene (1) and 1-methoxypyrene (2) were the compounds examined. The optimum conditions demonstrated complete disappearance of 1 and 2, mass recoveries were above 84%, and the formation of reduced dimers in less than 10 mole % yield. The possibility of cleaving a C-C bond by a (3+2) cycloaddition and subsequent cycloreversion reactions was examined by treating a variety of dipolarphiles with deprotonated (({eta}{sup 6}-arene)FeCp){sup +} complexes (arene = hexamethylbenzene or tetralin) Azides and ozone were found to add quantitatively to the metal-arene complexes. Upon decomplexation of the ring, moderated yields of benzyl substituted products were isolated. The mechanism of this reaction is yet unknown but is postulated to occur by direct nucleophilic addition of the complex anion to the most electropositive atom of the dipolarphile. Chemical and electrochemical oxidation techniques were applied to the deprotonated (({eta}{sup 6}-arene)FeCp){sup +} complexes. Only minor yields of benzylic oxidation products were observed.

  5. Comparative effect of nitroarenes and their parent arenes on hepatic drug and carcinogen metabolism in rats

    SciTech Connect

    Asokan, P.; Das, M.; Bickers, D.; Mukhtar, H.

    1986-03-01

    The effect of a single topical application of several nitroarenes (1-nitropyrene, nitropyrenes mixture, nitrobenzo(ghi)perylenes mixture, 3-nitrofluoranthene (3-NF), nitrofluoranthenes mixture (NFM), and nitroperylenes mixture (NPM) and their corresponding parent arenes was studied for their effect on hepatic drug and carcinogen metabolism in neonatal rats. All compounds caused highly significant induction of aryl hydrocarbon hydroxylase (AHH), 7-ethoxyresorufin O-deethylase (ERD), 7-ethoxycoumarin O-deethylase activities, and benzo(a)pyrene (BP) metabolism. The induction by each nitroarene was significant when compared to controls or to their corresponding parent non-nitrated arenes. 1-Nitropyrene was least effective in this regard. The inducing effect of NFM and NP was closely similar to 3-methylcholanthrene (3-MC). Benzphentamine N-demethylase, NADPH-cytochrome c reductase, NADH-ferricyanide reductase activities and the levels of cytochrome P-450 and cytochrome b/sub 5/ remained uncharged following treatment with arenes or nitroarenes. However, a shift of approximately 1 nm to the blue region in the absorption of P-450 was observed in nitroarenes-treated animals. A single topical or parenteral administration of 3-NF or NFM to adult rats also resulted in significant induction of ERD and AHH activities and BP metabolism. The parent arene, fluoranthene was ineffective in this regard. The authors studies suggest that nitroarenes are inducers of hepatic monooxygenases and they resemble the 3-MC type of inducers in rats.

  6. A pillar[5]arene-fused cryptand: from orthogonal self-assembly to supramolecular polymer.

    PubMed

    Wang, Qi; Cheng, Ming; Zhao, Yue; Wu, Lin; Jiang, Juli; Wang, Leyong; Pan, Yi

    2015-02-28

    A pillar[5]arene-fused cryptand with two different cavities was synthesized successfully. It was found that the novel tricyclic host could associate with two different guest species in an orthogonal manner. And based on this orthogonal self-assembly of two host-guest interactions, a novel type of supramolecular polymer was constructed easily and conveniently. PMID:25636005

  7. A photochromic supramolecular polymer based on bis-p-sulfonatocalix[4]arene recognition in aqueous solution.

    PubMed

    Yao, Xuyang; Li, Teng; Wang, Sheng; Ma, Xiang; Tian, He

    2014-07-11

    A photochromic supramolecular polymer based on bis-p-sulfonatocalix[4]arene recognition with a dithienylethene derivative in aqueous solution was fabricated. The resultant polymer showed good photochromic behaviour with obvious colour switching and a morphology change under alternative UV/Vis light stimuli. PMID:24853232

  8. Selective single crystal complexation of L- or D-leucine by p-sulfonatocalix[6]arene.

    PubMed

    Atwood, Jerry L; Dalgarno, Scott J; Hardie, Michaele J; Raston, Colin L

    2005-01-21

    p-Sulfonatocalix[6]arene, organised in the 'double cone' conformation, has multi-guest capability binding either L- or D-leucine in a single crystal in a bi-layer type arrangement from a racemic mixture of the amino acid. PMID:15645029

  9. Complex polycyclic scaffolds by metathesis rearrangement of Himbert arene/allene cycloadducts.

    PubMed

    Lam, Jonathan K; Schmidt, Yvonne; Vanderwal, Christopher D

    2012-11-01

    The intramolecular arene/allene cycloaddition first described 30 years ago by Himbert and Henn permits rapid access to strained polycyclic compounds. Alkene metathesis processes cleanly rearrange appropriately substituted cycloadducts into complex, functional-group-rich polycyclic lactams of potential utility for natural product synthesis and medicinal chemistry. PMID:23067058

  10. Pentanuclear lanthanide pyramids based on thiacalix[4]arene ligand exhibiting slow magnetic relaxation.

    PubMed

    Ge, Jing-Yuan; Ru, Jing; Gao, Feng; Song, You; Zhou, Xin-Hui; Zuo, Jing-Lin

    2015-09-21

    A series of pentanuclear Ln(III) clusters, [Ln5(μ4-OH)(μ3-OH)4(L1)(acac)6] (H4L1 = p-tert-butylthiacalix[4]arene; acac = acetylacetonate; Ln = Dy, Ho, Er) and [Ln5(μ5-OH)(μ3-OH)4(L1)(L2)2(acac)2(CH3OH)2] (H3L2 = 5,11,17,23-tetrakis(1,1-dimethylethyl)-25,26,27-trihydroxy-28-methoxy thiacalix[4]arene; Ln = Dy, Ho, Er), have been synthesized based on the thiacalix[4]arene ligand. All of these complexes feature a square-based pyramid with four triangular Ln3 structural motifs. One μ4-OH group bridges four Ln(III) ions in the basal plane of , while the OH group in complexes adopts the μ5-coordination mode. Our results illuminate the coordination modes of the versatile thiacalix[4]arene ligands and their application to new cluster compounds. The structural and magnetic studies confirm that the molecular symmetries and coordination geometries for lanthanide metal cores have a significant effect on some parameters as single-molecule magnets. Among them, two Dy5 pyramids exhibit distinct slow magnetic relaxation. PMID:26237158

  11. Why Aren?t Lightsabers Real Yet? Get the Lowdown from a Laser Physicist

    ScienceCinema

    Hunsberger, Maren; Liao, Zhi

    2016-03-22

    The release of "Star Wars: The Force Awakens" begs the obvious question: Why aren't lightsabers real yet? LLNL science communicator Maren Hunsberger gets the lowdown from laser physicist Zhi Liao in this first installment of "Inside the Lab," a new YouTube series exploring crazy-cool science questions.

  12. Versatile assembly of p-carboxylatocalix[4]arene-O-alkyl ethers

    SciTech Connect

    Kennedy, Stuart; Teat, Simon J.; Dalgarno, Scott J.

    2009-07-08

    Crystallisation of lower-rim tetra-O-alkylated p-carboxylatocalix[4]arenes from pyridine results in the formation of both bi-layer and pillar type supramolecular motifs. Full alkylation at the calixarene lower rim has significant influence over the supramolecular self-assembly motif, including preclusion of pyridine guest molecules from the calixarene cavity in the solid state.

  13. Oxatub[4]arene: a molecular "transformer" capable of hosting a wide range of organic cations.

    PubMed

    Jia, Fei; Wang, Hao-Yi; Li, Dong-Hao; Yang, Liu-Pan; Jiang, Wei

    2016-04-14

    The molecular "transformer", oxatub[4]arene, was found to be able to host a wide range of organic cations. The strong binding ability is believed to originate from its four interconvertible and deep-cavity conformers. The binding behavior of such adaptable receptors may provide implications for molecular recognition in nature. PMID:26955919

  14. Multifunctional water-soluble molecular capsules based on p-phosphonic acid calix[5]arene.

    PubMed

    Martin, Adam D; Boulos, Ramiz A; Hubble, Lee J; Hartlieb, Karel J; Raston, Colin L

    2011-07-14

    p-Phosphonic acid calix[5]arene forms molecular capsules in water based on two of the molecules, which can be loaded with carboplatin using intense shearing, and attached to single wall carbon nano-tubes. Spin coating of the capsules onto a substrate affords 2 nm fibres of stacked calixarenes, with the self-assembly understood using molecular modelling. PMID:21637889

  15. Review of "Incomplete: How Middle Class Schools Aren't Making the Grade". Think Tank Review

    ERIC Educational Resources Information Center

    Baker, Bruce D.

    2011-01-01

    "Incomplete: How Middle Class Schools Aren't Making the Grade" is a new report from Third Way, a Washington, D.C.-based policy think tank. The report aims to convince parents, taxpayers and policymakers that they should be as concerned about middle-class schools not making the grade as they are about the failures of the nation's large, poor, urban…

  16. Molecular binding behavior of bipyridium derivatives by water-soluble carboxylato-biphen[3]arene.

    PubMed

    Ma, Junwei; Deng, Hongmei; Ma, Suxiang; Li, Jian; Jia, Xueshun; Li, Chunju

    2015-04-18

    Complexation of two types of dicationic bipyridium guests, paraquat derivatives and bis(N-mono-substituted bipyridine) cations, by a negatively charged carboxylato-biphen[3]arene (CBP3) in water is reported. CBP3 could strongly interact with these guests, where charge-transfer and electrostatic interactions play important roles. PMID:25778925

  17. Highly selective binding of methyl orange dye by cationic water-soluble pillar[5]arenes.

    PubMed

    Yakimova, L S; Shurpik, D N; Gilmanova, L H; Makhmutova, A R; Rakhimbekova, A; Stoikov, I I

    2016-05-01

    A new water-soluble pillar[5]arene with an amide fragment and triethylammonium groups was synthesized by our original method of aminolysis of the ester groups. Using UV-spectroscopy, it is shown that cationic pillar[5]arenes are able to selectively form 1 : 1 complexes with some hydrophobic anions: the guests with bulky uncharged or negatively charged substituents hindering entry into the macrocycle cavity. Highly selective binding of the most lipophilic guest, methyl orange dye, in the form of organic anion salts by positively charged water-soluble pillar[5]arenes was detected. In the case of the azo dye the appropriate Kass values were 10-100-fold higher than those calculated for the other sulfonic acid derivatives studied. The 2D NMR NOESY (1)H-(1)H spectroscopy confirms the formation of the inclusion complex: negative charge sulfonate head is outside the cavity of pillar[5]arenes and the hydrophobic fragment of the guest is located in the cavity. PMID:27074630

  18. Single-Face/All-cis Arene Hydrogenation by a Supported Single-Site d(0) Organozirconium Catalyst.

    PubMed

    Stalzer, Madelyn Marie; Nicholas, Christopher P; Bhattacharyya, Alak; Motta, Alessandro; Delferro, Massimiliano; Marks, Tobin J

    2016-04-18

    The single-site supported organozirconium catalyst Cp*ZrBz2 /ZrS (Cp*=Me5 C5 , Bz=benzyl, ZrS=sulfated zirconia) catalyzes the single-face/all-cis hydrogenation of a large series of alkylated and fused arene derivatives to the corresponding all-cis-cyclohexanes. Kinetic/mechanistic and DFT analysis argue that stereoselection involves rapid, sequential H2 delivery to a single catalyst-bound arene face, versus any competing intramolecular arene π-face interchange. PMID:26990244

  19. Palladium-Catalyzed Desilylative Acyloxylation of Silicon-Carbon Bonds on (Trimethylsilyl)arenes: Synthesis of Phenol Derivatives from Trimethylsilylarenes.

    PubMed

    Gondo, Keisuke; Oyamada, Juzo; Kitamura, Tsugio

    2015-10-01

    A strategy for desilylative acetoxylation of (trimethylsilyl)arenes has been developed in which (trimethylsilyl)arenes are converted into acetoxyarenes. The direct acetoxylation is performed in the presence of 5 mol % of Pd(OAc)2 and PhI(OCOCF3)2 (1.5 equiv) in AcOH at 80 °C for 17 h. The acetoxyarenes are obtained in good to high yields (67-98%). The synthetic utility is demonstrated with a one-pot transformation of (trimethylsilyl)arenes to phenols by successive acetoxylation and hydrolysis. Furthermore, desilylative acyloxylation of 2-(trimethylsilyl)naphthalene using several carboxylic acids has been conducted. PMID:26401835

  20. Glued Langmuir-Blodgett bilayers from calix[n]arenes: Influence of calix[n]arene size on ionic cross-linking, film thickness, and permeation selectivity

    SciTech Connect

    Wang, Minghui; Janout, Vaclav; Regen, Steven L.

    2010-07-12

    A homologous series of calix[4]arene-, calix[5]arene- and calix[6]arene-based surfactants, containing pendant trimethylammonium and n-hexadecyl groups, have been compared with respect to their ability (i) to undergo ionic crosslinking at the air/water interface, (ii) to incorporate poly(4-styrenesulfonate) (PSS) in Langmuir-Blodgett (LB) bilayers, and (iii) to act as barriers towards He, N2 and CO2 when assembled into crosslinked LB bilayers. As these calix[n]arenes increase in size, their ability to undergo ionic crosslinking has been found to increase, the thickness of corresponding glued LB bilayers has been found to decrease, and their barrier properties and permeation selectivities have been found to increase. In conclusion, the likely origin for these effects and the probable mechanism by which He, N2 and CO2 cross these ultrathin films are discussed.

  1. Metal-free protodeboronation of electron-rich arene boronic acids and its application to ortho-functionalization of electron-rich arenes using a boronic acid as a blocking group.

    PubMed

    Ahn, Su-Jin; Lee, Chun-Young; Kim, Nak-Kyoon; Cheon, Cheol-Hong

    2014-08-15

    The metal-free thermal protodeboronation of various electron-rich arene boronic acids was studied. Several reaction parameters controlling this protodeboronation, such as solvent, temperature, and a proton source, have been investigated. On the basis of these studies, suitable reaction conditions for protodeboronation of several types of electron-rich arene boronic acids were provided. On the basis of this protodeboronation, a new protocol for the synthesis of ortho-functionalized electron-rich arenes from these boronic acids was developed using the boronic acid moiety as a blocking group in the electrophilic aromatic substitution reaction, followed by the removal of the boronic acid moiety via thermal protodeboronation. Mechanistic studies suggested that this protodeboronation might proceed via the complex formation of a boronic acid with a proton source, followed by the carbon-boron bond fission through σ-bond metathesis, to afford the corresponding arene compound and boric acid. PMID:25052375

  2. Phosphonate monoesters on a thiacalix[4]arene framework as potential inhibitors of protein tyrosine phosphatase 1B.

    PubMed

    Trush, Viacheslav V; Kharchenko, Sergiy G; Tanchuk, Vsevolod Yu; Kalchenko, Vitaly I; Vovk, Andriy I

    2015-09-01

    Monoester derivatives of thiacalix[4]arene tetrakis(methylphosphonic) acid were found to be capable of inhibiting protein tyrosine phosphatase 1B. In addition, these compounds can strongly bind to human serum albumin. PMID:26205135

  3. The high yielding synthesis of pillar[5]arenes under Friedel-Crafts conditions explained by dynamic covalent bond formation.

    PubMed

    Holler, Michel; Allenbach, Nicolas; Sonet, Jordan; Nierengarten, Jean-François

    2012-03-01

    Systematic investigations of the cyclooligomerization of 1,4-disubstituted hydroquinone derivatives under Friedel-Crafts conditions have been carried out to demonstrate that the formation of pillar[5]arenes occurs under thermodynamic control. PMID:22159430

  4. Derivation of structure-activity relationships from the anticancer properties of ruthenium(II) arene complexes with 2-aryldiazole ligands.

    PubMed

    Martínez-Alonso, Marta; Busto, Natalia; Jalón, Félix A; Manzano, Blanca R; Leal, José M; Rodríguez, Ana M; García, Begoña; Espino, Gustavo

    2014-10-20

    The ligands 2-pyridin-2-yl-1H-benzimidazole (HL(1)), 1-methyl-2-pyridin-2-ylbenzimidazole (HL(2)), and 2-(1H-imidazol-2-yl)pyridine (HL(3)) and the proligand 2-phenyl-1H-benzimidazole (HL(4)) have been used to prepare five different types of new ruthenium(II) arene compounds: (i) monocationic complexes with the general formula [(η(6)-arene)RuCl(κ(2)-N,N-HL)]Y [HL = HL(1), HL(2), or HL(3); Y = Cl or BF4; arene = 2-phenoxyethanol (phoxet), benzene (bz), or p-cymene (p-cym)]; (ii) dicationic aqua complexes of the formula [(η(6)-arene)Ru(OH2)(κ(2)-N,N-HL(1))](Y)2 (Y = Cl or TfO; arene = phoxet, bz, or p-cym); (iii) the nucleobase derivative [(η(6)-arene)Ru(9-MeG)(κ(2)-N,N-HL(1))](PF6)2 (9-MeG = 9-methylguanine); (iv) neutral complexes consistent with the formulation [(η(6)-arene)RuCl(κ(2)-N,N-L(1))] (arene = bz or p-cym); (v) the neutral cyclometalated complex [(η(6)-p-cym)RuCl(κ(2)-N,C-L(4))]. The cytototoxic activity of the new ruthenium(II) arene compounds has been evaluated in several cell lines (MCR-5, MCF-7, A2780, and A2780cis) in order to establish structure-activity relationships. Three of the compounds with the general formula [(η(6)-arene)RuCl(κ(2)-N,N-HL(1))]Cl differing in the arene moiety have been studied in depth in terms of thermodynamic dissociation constants, aquation kinetic constants, and DNA binding measurements. The biologically most active compound is the p-cym derivative, which strongly destabilizes the DNA double helix, whereas those with bz and phoxet have only a small effect on the stability of the DNA double helix. Moreover, the inhibitory activity of several compounds toward CDK1 has also been evaluated. The DNA binding ability of some of the studied compounds and their CDK1 inhibitory effect suggest a multitarget mechanism for their biological activity. PMID:25302401

  5. A1/A2-Diamino-Substituted Pillar[5]arene-Based Acid-Base-Responsive Host-Guest System.

    PubMed

    Hu, Wei-Bo; Hu, Wen-Jing; Zhao, Xiao-Li; Liu, Yahu A; Li, Jiu-Sheng; Jiang, Biao; Wen, Ke

    2016-05-01

    An acid-base-responsive supramolecular host-guest system based on a planarly chiral A1/A2-diamino-substituted pillar[5]arene (1)/imidazolium ion recognition motif was created. The pillar[4]arene[1]diaminobenzene 1 can bring an electron-deficient imidazolium cation into its cylindrically shaped cavity under neutral or basic conditions and release it under acidic conditions. PMID:27088317

  6. Iron-mediated oxidative C-H coupling of arenes and alkenes directed by sulfur: an expedient route to dihydrobenzofurans.

    PubMed

    Cavanagh, Craig W; Aukland, Miles H; Laurent, Quentin; Hennessy, Alan; Procter, David J

    2016-06-21

    A novel route to medicinally-relevant dihydrobenzofurans utilises a sulfur-directed C-H ortho-coupling of arenes and unactivated terminal alkenes mediated by iron, and a palladium-catalysed deallylation/heterocyclisation sequence. The iron-mediated coupling affords linear products of alkene chloroarylation in good yield and with complete regioselectivity. The coupling likely proceeds by redox-activation of the arene partner by iron(iii) and alkene addition to the resultant radical cation. PMID:27198174

  7. Control of the rheological properties of clay nanosheet hydrogels with a guanidinium-attached calix[4]arene binder.

    PubMed

    Lee, Ji Ha; Kim, Chaelin; Jung, Jong Hwa

    2015-10-21

    A 1,3-alternate calix[4]arene derivative 1 possessing four guanidinium moieties was synthesized as a molecular binder. The clay nanosheet (CNS) hydrogels were prepared upon addition of 1 and sodium polyacrylate (ASSP), and their mechanical properties were measured by rheometry. CNS hydrogels prepared by combining calix[4]arene 1 with dispersed CNSs surrounded by ASSPs showed an enhancement of mechanical properties such as viscosity and elasticity. PMID:26327603

  8. Extremely robust and post-functionalizable gold nanoparticles coated with calix[4]arenes via metal-carbon bonds.

    PubMed

    Troian-Gautier, Ludovic; Valkenier, Hennie; Mattiuzzi, Alice; Jabin, Ivan; den Brande, Niko Van; Mele, Bruno Van; Hubert, Julie; Reniers, François; Bruylants, Gilles; Lagrost, Corinne; Leroux, Yann

    2016-08-18

    Gold nanoparticles stabilized with a thin layer of post-functionalizable calix[4]arenes were prepared through the reductive grafting of a calix[4]arene-tetra-diazonium salt. These particles show exceptional stability towards extreme pH, F(-), NaCl, and upon drying. Post-functionalization of the calix-layer was demonstrated, opening the way to a wide range of applications. PMID:27452314

  9. Conformational isomerism in the solid-state structures of tetracaine and tamoxifen with para-sulphonato-calix[4]arene

    NASA Astrophysics Data System (ADS)

    Danylyuk, Oksana; Monachino, Melany; Lazar, Adina N.; Suwinska, Kinga; Coleman, Anthony W.

    2010-02-01

    The solid-state complexes between para-sulphonato-calix[4]arene and the drugs tamoxifen and tetracaine show an unusual 4:1 guest-host stoichiometry with formation of hydrophobic layer of drug molecules held between bilayers of para-sulphonato-calix[4]arene. In both structures each of the four independent drug molecules adopts different conformation due to the different mode of interaction with the anionic host, the neighbouring drug cations and water molecules.

  10. Carboxylate-Assisted Iridium-Catalyzed C-H Amination of Arenes with Biologically Relevant Alkyl Azides.

    PubMed

    Zhang, Tao; Hu, Xuejiao; Wang, Zhen; Yang, Tiantian; Sun, Hao; Li, Guigen; Lu, Hongjian

    2016-02-24

    An iridium-catalyzed C-H amination of arenes with a wide substrate scope is reported. Benzamides with electron-donating and -withdrawing groups and linear, branched, and cyclic alkyl azides are all applicable. Cesium carboxylate is crucial for both reactivity and regioselectivity of the reactions. Many biologically relevant molecules, such as amino acid, peptide, steroid, sugar, and thymidine derivatives can be introduced to arenes with high yields and 100 % chiral retention. PMID:26712274

  11. Rhodium-Catalyzed C-S and C-N Functionalization of Arenes: Combination of C-H Activation and Hypervalent Iodine Chemistry.

    PubMed

    Wang, Fen; Yu, Xinzhang; Qi, Zisong; Li, Xingwei

    2016-01-11

    Rhodium-catalyzed sulfonylation, thioetherification, thiocyanation, and other heterofunctionalizations of arenes bearing a heterocyclic directing group have been realized. The reaction proceeds by initial Rh(III) -catalyzed C-H hyperiodination of arene at room temperature followed by uncatalyzed nucleophilic functionalization. A diaryliodonium salt is isolated as an intermediate, which represents umpolung of the arene substrate, in contrast to previous studies that suggested umpolung of the coupling partner. PMID:26538162

  12. Host-guest interaction of flavanone and 7-aminoflavone with C-Hexylpyrogallol[4]arene

    NASA Astrophysics Data System (ADS)

    Chandrasekaran, Sowrirajan; Enoch, Israel V. M. V.

    2014-11-01

    In this paper, we report the structures of the host-guest complexes of flavanone and 7-aminoflavone (guests) with C-Hexylpyrogallol[4]arene (host). The study of the host-guest binding is carried out using UV-Visible absorption, steady-state and time-resolved fluorescence, and 2D ROESY spectroscopy. The stoichiometry and the binding constant of the C-Hexylpyrogallol[4]arene-guest complexes are reported based on absorption and fluorescence titrations. Both flavanone and 7-aminoflavone form 1:1 complexes with the host with binding constant values of 1.71 × 104 mol-1 dm3 and 2.06 × 104 mol-1 dm3 respectively. Fluorescence quenching of the two flavonoids on complex formation occurs and the Stern-Volmer constants are reported. The mode of binding of flavanone and 7-aminoflavone with the host molecule is optimized with 2D ROESY and the structures of the inclusion complexes are proposed.

  13. Bis-tert-Alcohol-Functionalized Crown-6-Calix[4]arene: An Organic Promoter for Nucleophilic Fluorination.

    PubMed

    Jadhav, Vinod H; Choi, Wonsil; Lee, Sung-Sik; Lee, Sungyul; Kim, Dong Wook

    2016-03-18

    A bis-tert-alcohol-functionalized crown-6-calix[4]arene (BACCA) was designed and prepared as a multifunctional organic promoter for nucleophilic fluorinations with CsF. By formation of a CsF/BACCA complex, BACCA could release a significantly active and selective fluoride source for SN2 fluorination reactions. The origin of the promoting effects of BACCA was studied by quantum chemical methods. The role of BACCA was revealed to be separation of the metal fluoride to a large distance (>8 Å), thereby producing an essentially "free" F(-). The synergistic actions of the crown-6-calix[4]arene subunit (whose O atoms coordinate the counter-cation Cs(+)) and the terminal tert-alcohol OH groups (forming controlled hydrogen bonds with F(-)) of BACCA led to tremendous efficiency in SN2 fluorination of base-sensitive substrates. PMID:26880350

  14. Highly selective hydrogenation of arenes using nanostructured ruthenium catalysts modified with a carbon–nitrogen matrix

    PubMed Central

    Cui, Xinjiang; Surkus, Annette-Enrica; Junge, Kathrin; Topf, Christoph; Radnik, Jörg; Kreyenschulte, Carsten; Beller, Matthias

    2016-01-01

    Selective hydrogenations of (hetero)arenes represent essential processes in the chemical industry, especially for the production of polymer intermediates and a multitude of fine chemicals. Herein, we describe a new type of well-dispersed Ru nanoparticles supported on a nitrogen-doped carbon material obtained from ruthenium chloride and dicyanamide in a facile and scalable method. These novel catalysts are stable and display both excellent activity and selectivity in the hydrogenation of aromatic ethers, phenols as well as other functionalized substrates to the corresponding alicyclic reaction products. Furthermore, reduction of the aromatic core is preferred over hydrogenolysis of the C–O bond in the case of ether substrates. The selective hydrogenation of biomass-derived arenes, such as lignin building blocks, plays a pivotal role in the exploitation of novel sustainable feedstocks for chemical production and represents a notoriously difficult transformation up to now. PMID:27113087

  15. Peroxide-Free Pd(II)-Catalyzed Ortho Aroylation and Ortho Halogenation of Directing Arenes.

    PubMed

    Santra, Sourav Kumar; Banerjee, Arghya; Mohanta, Prakash Ranjan; Patel, Bhisma K

    2016-07-15

    A Pd(II)-catalyzed peroxide-free ortho aroylation of directing arenes has been developed via cross dehydrogenative coupling (CDC) in the presence of the terminal oxidant Cu(OAc)2·H2O. Ortho aroylation of directing arenes proceeds via decarbonylation of the in situ generated phenyl glyoxal, which is obtained from 2-acetoxyacetophenone in the presence of the oxidant Cu(OAc)2·H2O. However, changing the oxidant to CuX2 (X = Cl, Br) provided exclusive di-ortho-halogenated 2-arylbenzothiazoles. During the halogenation, CuX2 served the dual role of a halogen source as well as a co-oxidant. PMID:27314648

  16. Pentavalent pillar[5]arene-based glycoclusters and their multivalent binding to pathogenic bacterial lectins.

    PubMed

    Galanos, Nicolas; Gillon, Emilie; Imberty, Anne; Matthews, Susan E; Vidal, Sébastien

    2016-04-01

    Anti-adhesive glycoclusters offer potential as therapeutic alternatives to classical antibiotics in treating infections. Pillar[5]arenes functionalised with either five galactose or five fucose residues were readily prepared using CuAAC reactions and evaluated for their binding to three therapeutically relevant bacterial lectins: LecA and Lec B from Pseudomonas aeuruginosa and BambL from Burkholderia ambifaria. Steric interactions were demonstrated to be a key factor in achieving good binding to LecA with more flexible galactose glycoclusters showing enhanced activity. In contrast binding to the fucose-selective lectins confirmed the importance of topology of the glycoclusters for activity with the pillar[5]arene ligand proving a selective ligand for BambL. PMID:26972051

  17. The magma budget of Volcan Arenal, Costa Rica from 1968 to 1980

    NASA Technical Reports Server (NTRS)

    Wadge, G.

    1983-01-01

    The magma volume emitted by Volcan Arenal, Costa Rica, has been calculated to be 304 x 10 to the 6th cu m. A near-continuous rise from very deep within the crust is proposed as an explanation for Arenal's magma supply, and the long-term seismic pattern is interpreted as individual batches of magma using previously fractured pathways. During a break in activity (1973) the effusion site moved from Crater A to Crater C, approximately 400 m higher. It is maintained that the steady downward tilting of the volcano's summit was caused by the loading of the volcano's western side by about 19 x 10 to the 6th cu m of lava. Also noted is the abrupt decrease in effusion rate compatible with the increased magmatic head needed to reach Crater C. It is concluded that the constancy of magma composition and effusion rate from 1974 to 1980 indicates a homogeneous magma reservoir.

  18. Highly selective hydrogenation of arenes using nanostructured ruthenium catalysts modified with a carbon-nitrogen matrix.

    PubMed

    Cui, Xinjiang; Surkus, Annette-Enrica; Junge, Kathrin; Topf, Christoph; Radnik, Jörg; Kreyenschulte, Carsten; Beller, Matthias

    2016-01-01

    Selective hydrogenations of (hetero)arenes represent essential processes in the chemical industry, especially for the production of polymer intermediates and a multitude of fine chemicals. Herein, we describe a new type of well-dispersed Ru nanoparticles supported on a nitrogen-doped carbon material obtained from ruthenium chloride and dicyanamide in a facile and scalable method. These novel catalysts are stable and display both excellent activity and selectivity in the hydrogenation of aromatic ethers, phenols as well as other functionalized substrates to the corresponding alicyclic reaction products. Furthermore, reduction of the aromatic core is preferred over hydrogenolysis of the C-O bond in the case of ether substrates. The selective hydrogenation of biomass-derived arenes, such as lignin building blocks, plays a pivotal role in the exploitation of novel sustainable feedstocks for chemical production and represents a notoriously difficult transformation up to now. PMID:27113087

  19. Polyaniline-Induced C-H Arylation of Arenes with Arenediazonium Salts.

    PubMed

    Amaya, Toru; Hata, Dai; Moriuchi, Toshiyuki; Hirao, Toshikazu

    2015-11-01

    A reduced form of polyaniline has been shown to induce direct arylation of an arenediazonium salt with an arene (Gomberg-Bachmann reaction) to give the cross-coupling product in moderate to good yields under mild conditions. Various arenediazonium salts and arenes, including heteroarenes such as furans, thiophenes, and pyrroles, are employed for the reaction. The most favorable combination of substrates is an electron-poor arenediazonium salt with an electron-rich heteroarene. Investigation of the mechanism by reactions with radical scavengers and experiments on kinetic isotope effects indicated the occurrence of a radical chain reaction initiated by one-electron reduction of an arenediazonium salt by the polyaniline. Only 1 mol % (based on aniline tetramer) of the polyaniline is required for the cross-coupling reaction to occur. This reaction proceeds under metal-free conditions and with no need for photonic activation. PMID:26439667

  20. Highly Regioselective Iodination of Arenes via Iron(III)-Catalyzed Activation of N-Iodosuccinimide.

    PubMed

    Racys, Daugirdas T; Warrilow, Catherine E; Pimlott, Sally L; Sutherland, Andrew

    2015-10-01

    An iron(III)-catalyzed method for the rapid and highly regioselective iodination of arenes has been developed. Use of the powerful Lewis acid, iron(III) triflimide, generated in situ from iron(III) chloride and a readily available triflimide-based ionic liquid allowed activation of N-iodosuccinimide (NIS) and efficient iodination under mild conditions of a wide range of substrates including biologically active compounds and molecular imaging agents. PMID:26394175

  1. Porphyrinic supramolecular daisy chains incorporating pillar[5]arene-viologen host-guest interactions.

    PubMed

    Fathalla, Maher; Strutt, Nathan L; Sampath, Srinivasan; Katsiev, Khabiboulakh; Hartlieb, Karel J; Bakr, Osman M; Stoddart, J Fraser

    2015-07-01

    A porphyrin functionalised with pillar[5]arene and a viologen at its 5- and 15-meso positions assembles in a head-to-tail manner, producing linear supramolecular daisy chains in dichloromethane. At high concentrations, it forms an organogel which has been investigated by electron microscopy and rheological measurements, paving the way for the preparation of other functional supramolecular assemblies which harness viologen⊂pillararene host-guest interactions. PMID:26027650

  2. A protocol to generate phthaloyl peroxide in flow for the hydroxylation of arenes.

    PubMed

    Eliasen, Anders M; Thedford, Randal P; Claussen, Karin R; Yuan, Changxia; Siegel, Dionicio

    2014-07-18

    A flow protocol for the generation of phthaloyl peroxide has been developed. This process directly yields phthaloyl peroxide in high purity (>95%) and can be used to bypass the need to isolate and recrystallize phthaloyl peroxide, improving upon earlier batch procedures. The flow protocol for the formation of phthaloyl peroxide can be combined with arene hydroxylation reactions and provides a method for the consumption of peroxide as it is generated to minimize the accumulation of large quantities of peroxide. PMID:24988535

  3. Guests inducing p-sulfonatocalix[4]arenes into nanocapsule and layer structure

    SciTech Connect

    Zheng Guoli; Fan Weiqiang; Song Shuyan; Guo Huadong; Zhang Hongjie

    2010-06-15

    Reaction of sodium p-sulfonatocalix[4]arene and TbCl{sub 3} in the presence of 2,2'-bipyridine-N,N'-dioxide (bpdo) gives the 2:1 supramolecular nanocapsule [[Tb(bpdo){sub 2}.4H{sub 2}O]{sup 3+} intersection {l_brace}p-sulfonatocalix[4]arene{sup 4-{r_brace}}{sub 2}], which further interacts with the [Tb(bpdo){sub 4}]{sup 3+} through charge-assisted {pi}-stacking interactions forming a channel structure 1. In further investigation, we tried to use the terpyridine-1,1',1'-trisoxide (tpto) instead of bpdo. Although we failed to isolate a supramolecular capsules based on the tpto, lanthanide and p-sulfonatocalix[4]arene, a layer structure derived from p-sulfonatocalix[4]arene with an unusual [Cu(tpto){sub 2}]{sup 2+} incorporation into the cavity of the calixarene and an outside [Cu(tpto){sub 2}]{sup 2+} balancing the charge, has been obtained. Fluorescence spectra show clearly that compound 1 possesses the luminescence characteristics of Tb{sup 3+} and the ligand bpdo can sensitize Tb{sup 3+} ion. Gas sorption experiment shows the channel structure 1 has highly selective gas sorption properties for water and methanol. - Graphical abstract: In the presence of different guests, a nanochannel architecture based on the p-sulfonato[4]calixarene capsule and a layered structure based on the p-sulfonato[4]calixarene tecton have been synthesized, and the luminescence properties and guest sorption of porous structure have been investigated.

  4. Palladium-Catalyzed Aerobic Oxidative Dehydrogenation of Cyclohexenes to Substituted Arene Derivatives

    PubMed Central

    Iosub, Andrei V.; Stahl, Shannon S.

    2015-01-01

    A palladium(II) catalyst system has been identified for aerobic dehydrogenation of substituted cyclohexenes to the corresponding arene derivatives. Use of sodium anthraquinone-2-sulfonate (AMS) as a co-catalyst enhances the product yields. A wide range of functional groups are tolerated in the reactions, and the scope and limitations of the method are described. The catalytic dehydrogenation of cyclohexenes is showcased in an efficient route to a phthalimide-based TRPA1 activity modulator. PMID:25734414

  5. Thin-skinned Mass-wasting Responsible for Rapid, Edifice-wide Deformation at Arenal Volcano

    NASA Astrophysics Data System (ADS)

    Ebmeier, S. K.; Biggs, J.; Muller, C.; Avard, G.

    2014-12-01

    Volcanic edifices are built rapidly, at rates far exceeding those of erosion. The resulting mechanical failure of the edifices of both active and quiescent volcanoes can result in hazards on a range of scales, from rockfall to sector collapse. The stability of a volcanic edifice depends on the ratio of its exogenous growth to mass loss due to erosion, deformation and mass wasting. Geodetic measurements of edifice spreading have mostly been associated with local zones of extension at island volcanoes and relatively few observations have been made at continental stratovolcanoes. We present measurements of displacement and surface property changes at Arenal, Costa Rica, a continental stratovolcano that stopped erupting in 2010 after almost 42 years of activity. High resolution TerraSAR-X data (2011-2013) have increased the area covered geodetically by ~40%, allowing us to make measurements of displacements close to Arenal's summit for the first time. InSAR and intensity change observations provide evidence of frequent rockfalls and of shallow landslides (5-11 m thick, total volume = 1.9×107 m3 DRE). Rockfall and shallow translational landsliding have a stabilizing effect on Volcán Arenal's edifice that reduces the potential for external triggering of slope failure. We map 16 shallow landslides (5-11 m depth, 4% of post-1968 deposits) and expect failure planes to be associated with layers of blocky debris and lava crust. Unstable material on Arenal's upper slopes is removed steadily, potentially reducing sensitivity to external triggers: the 2012 Nicoya Earthquake (Mw 7.6) had no measurable impact on the velocities of sliding units, but did result in an elevated area of rockfall. This demonstrates the importance of mass wasting for the stability of young volcanic edifices.

  6. Unique organization of solvent molecules within the hexameric capsules of pyrogallol[4]arene in solution.

    PubMed

    Guralnik, Vicky; Avram, Liat; Cohen, Yoram

    2014-11-01

    The hexameric capsules of pyrogallol[4]arene (2b) were prepared in nondeuterated solvents in the absence and presence of adamantane carboxylic acid (3). The small encapsulated molecules were shown to occupy different sites within the same capsule. In the presence of 3, which are also encapsulated in the hexameric capsules, one observes yet another pair of signals for the encapsulated solvent molecules. Different NMR experiments enabled assignment of the different sites within the hexameric capsules of 2b. PMID:25337806

  7. Synthesis and investigation of the properties of novel azocalix[4]arenes

    NASA Astrophysics Data System (ADS)

    Kart, H. H.; Bayrakdar, A.; Elcin, S.; Deligoz, H.; Karabacak, M.

    2015-07-01

    The azocalix[4]arenes molecules such as methylphenylazocalix[4]aren (MPcalix[4]) and methoxyphenylazocalix[4]aren (MOPcalix[4]) have been synthesized and characterized by experimental FT-IR and 1H NMR spectral analyses. The fundamental vibrational transitions have been addressed by experimental FT-IR (4000-400 cm-1) technique and density functional theory (DFT) employing B3LYP level with the 6-31G(d) and 6-311G(d,p) basis sets. The 1H NMR spectra of the studied compounds have been recorded in chloroform, and compared with computed data obtained by using gauge including atomic orbital (GIAO) method. Furthermore, thermodynamic properties (heat capacity, entropy, and enthalpy changes) and frontier molecular orbitals of the molecules in the ground state have been calculated by using the same method and basis sets. The non-linear optical properties such as the first order hyperpolarizability (β0), related properties (α0 and Δα) are also computed. Information about the charge density distribution of the molecules and its chemical reactivity has been studied by mapping molecular electrostatic potential surface (MEPs). The scaled vibrational frequency values have been compared with experimental FT-IR spectroscopic data. The correlations between the observed and calculated frequencies are in good agreement with each other as well as the correlation of NMR data. The linear polarizability and first hyperpolarizability of the studied molecules indicate that the compounds are a good candidate of nonlinear optical materials.

  8. Synthesis and investigation of the properties of novel azocalix[4]arenes.

    PubMed

    Kart, H H; Bayrakdar, A; Elcin, S; Deligoz, H; Karabacak, M

    2015-07-01

    The azocalix[4]arenes molecules such as methylphenylazocalix[4]aren (MPcalix[4]) and methoxyphenylazocalix[4]aren (MOPcalix[4]) have been synthesized and characterized by experimental FT-IR and (1)H NMR spectral analyses. The fundamental vibrational transitions have been addressed by experimental FT-IR (4000-400 cm(-1)) technique and density functional theory (DFT) employing B3LYP level with the 6-31G(d) and 6-311G(d,p) basis sets. The (1)H NMR spectra of the studied compounds have been recorded in chloroform, and compared with computed data obtained by using gauge including atomic orbital (GIAO) method. Furthermore, thermodynamic properties (heat capacity, entropy, and enthalpy changes) and frontier molecular orbitals of the molecules in the ground state have been calculated by using the same method and basis sets. The non-linear optical properties such as the first order hyperpolarizability (β0), related properties (α0 and Δα) are also computed. Information about the charge density distribution of the molecules and its chemical reactivity has been studied by mapping molecular electrostatic potential surface (MEPs). The scaled vibrational frequency values have been compared with experimental FT-IR spectroscopic data. The correlations between the observed and calculated frequencies are in good agreement with each other as well as the correlation of NMR data. The linear polarizability and first hyperpolarizability of the studied molecules indicate that the compounds are a good candidate of nonlinear optical materials. PMID:25813172

  9. New RuII (arene) complexes with halogen-substituted bis- and tris(pyrazol-1-yl)borate ligands.

    PubMed

    Orbisaglia, Serena; Di Nicola, Corrado; Marchetti, Fabio; Pettinari, Claudio; Pettinari, Riccardo; Martins, Luísa M D R S; Alegria, Elisabete C B A; da Silva, M Fátima C Guedes; Rocha, Bruno G M; Kuznetsov, Maxim L; Pombeiro, Armando J L; Skelton, Brian W; Sobolev, Alexandre N; White, Allan H

    2014-03-24

    [RuCl(arene)(μ-Cl)]2 dimers were treated in a 1:2 molar ratio with sodium or thallium salts of bis- and tris(pyrazolyl)borate ligands [Na(Bp(Br3))], [Tl(Tp(Br3))], and [Tl(Tp(iPr, 4Br))]. Mononuclear neutral complexes [RuCl(arene)(κ(2)-Bp(Br3))] (1: arene=p-cymene (cym); 2: arene=hexamethylbenzene (hmb); 3: arene=benzene (bz)), [RuCl(arene)(κ(2)-Tp(Br3))] (4: arene=cym; 6: arene=bz), and [RuCl(arene)(κ(2)-Tp(iPr, 4Br))] (7: arene=cym, 8: arene=hmb, 9: arene=bz) have been always obtained with the exception of the ionic [Ru2 (hmb)2-(μ-Cl)3][Tp(Br3)] (5'), which formed independently of the ratio of reactants and reaction conditions employed. The ionic [Ru-(CH3OH)(cym)(κ(2)-Bp(Br3))][X] (10: X=PF6, 12: X=O3SCF3) and the neutral [Ru(O2CCF3)(cym)(κ(2)-Bp(Br3))] (11) have been obtained by a metathesis reaction with corresponding silver salts. All complexes 1-12 have been characterized by analytical and spectroscopic data (IR, ESI-MS, (1)H and (13)C NMR spectroscopy). The structures of the thallium and calcium derivatives of ligand Tp(Br3), [Tl(Tp(Br3))] and [Ca(dmso)6][Tp(Br3)]2 ⋅2 DMSO, of the complexes 1, 4, 5', 6, 11, and of the decomposition product [RuCl(cym)(Hpz(iPr, 4Br))2][Cl] (7') have been confirmed by using single-crystal X-ray diffraction. Electrochemical studies showed that 1-9 and 11 undergo a single-electron Ru(II) →Ru(III) oxidation at a potential, measured by cyclic voltammetry, which allows comparison of the electron-donor characters of the bis- and tris(pyrazol-1-yl)borate and arene ligands, and to estimate, for the first time, the values of the Lever EL ligand parameter for Bp(Br3), Tp(Br3), and Tp(iPr, 4Br). Theoretical calculations at the DFT level indicated that both oxidation and reduction of the Ru complexes under study are mostly metal-centered with some involvement of the chloride ligand in the former case, and also demonstrated that the experimental isolation of the μ(3)-binuclear complex 5' (instead of the mononuclear 5

  10. 1,3-Alternate calix[4]arene nitronyl nitroxide tetraradical and diradical: synthesis, X-ray crystallography, paramagnetic NMR spectroscopy, EPR spectroscopy, and magnetic studies

    SciTech Connect

    Rajca, Andrzej; Pink, Maren; Mukherjee, Sumit; Rajca, Suchada; Das, Kausik

    2008-04-02

    Calix[4]arenes constrained to 1,3-alternate conformation and functionalized at the upper rim with four and two nitronyl nitroxides have been synthesized, and characterized by X-ray crystallography, magnetic resonance (EPR and {sup 1}H NMR) spectroscopy, and magnetic studies. Such calix[4]arene tetraradicals and diradicals provide scaffolds for through-bond and through-space intramolecular exchange couplings.

  11. A comparative DFT study on aquation and nucleobase binding of ruthenium (II) and osmium (II) arene complexes.

    PubMed

    Wang, Hanlu; Zeng, Xingye; Zhou, Rujin; Zhao, Cunyuan

    2013-11-01

    The potential energy surfaces of the reactions of organometallic arene complexes of the type [(η (6)-arene)M(II)(pic)Cl] (where pic = 2-picolinic acid, M = Ru or Os) were examined by a DFT computational study. Among the seven density functional methods, hybrid exchange functional B3LYP outperforms the others to explain the aquation of the complexes. The reactions and binding energies of Ru(II) and Os(II) arene complexes with both 9EtG and 9EtA were studied to gain insight into the reactivity of these types of organometallic complexes with DNA. The obtained data rationalize experimental observation, contributing to partly understanding the potential biological and medical applications of organometallic complexes. PMID:24037457

  12. Dimerization control in the self-assembly behavior of copillar[5]arenes bearing ω-hydroxyalkoxy groups.

    PubMed

    Liu, Luzhi; Wang, Lingyun; Liu, Changchun; Fu, Zhiyong; Meier, Herbert; Cao, Derong

    2012-10-19

    Two novel copillar[5]arenes bearing ω-hydroxyalkoxy groups are synthesized and their self-assembly properties are studied by (1)H NMR spectroscopy, specific viscosity, and X-ray measurements. The copillar[5]arene 2b bearing a 6-hydroxyhexyloxy group exhibits a reversible self-assembly behavior, leading to the formation of the self-inclusion monomer and hugging dimers. The reversible self-assembly behavior can be controlled by tuning solvent, temperature, guest, and H-bond interaction. However, the copillar[5]arene 2a bearing a short 4-hydroxybutyloxy group does not show such a self-assembly behavior to the formation of the self-inclusion monomer and hugging dimers. PMID:22998632

  13. Influence of the π-coordinated arene on the anticancer activity of ruthenium(II) carbohydrate organometallic complexes

    NASA Astrophysics Data System (ADS)

    Hanif, Muhammad; Meier, Samuel; Nazarov, Alexey; Risse, Julie; Legin, Anton; Casini, Angela; Jakupec, Michael; Keppler, Bernhard; Hartinger, Christian

    2013-10-01

    The synthesis and in vitro cytotoxicity of a series of RuII(arene) complexes with carbohydrate-derived phosphite ligands and various arene co-ligands is described. The arene ligand has a strong influence on the in vitro anticancer activity of this series of compounds, which correlates fairly well with cellular accumulation. The most lipophilic compound bearing a biphenyl moiety and a cyclohexylidene-protected carbohydrate is the most cytotoxic with unprecedented IC50 values for the compound class in three human cancer cell lines. This compound shows reactivity to the DNA model nucleobase 9-ethylguanine, but does not alter the secondary structure of plasmid DNA indicating that other biological targets are responsible for its cytotoxic effect.

  14. Influence of the π-coordinated arene on the anticancer activity of ruthenium(II) carbohydrate organometallic complexes

    PubMed Central

    Hanif, Muhammad; Meier, Samuel M.; Nazarov, Alexey A.; Risse, Julie; Legin, Anton; Casini, Angela; Jakupec, Michael A.; Keppler, Bernhard K.; Hartinger, Christian G.

    2013-01-01

    The synthesis and in vitro cytotoxicity of a series of RuII(arene) complexes with carbohydrate-derived phosphite ligands and various arene co-ligands is described. The arene ligand has a strong influence on the in vitro anticancer activity of this series of compounds, which correlates fairly well with cellular accumulation. The most lipophilic compound bearing a biphenyl moiety and a cyclohexylidene-protected carbohydrate is the most cytotoxic with unprecedented IC50 values for the compound class in three human cancer cell lines. This compound shows reactivity to the DNA model nucleobase 9-ethylguanine, but does not alter the secondary structure of plasmid DNA, indicating that other biological targets are responsible for its cytotoxic effect. PMID:24790955

  15. Molecular recognition of curcumin (Indian Ayurvedic medicine) by the supramolecular probe, p-t-butyl calix(8)arene

    NASA Astrophysics Data System (ADS)

    Meenakshi, C.; Jayabal, P.; Ramakrishnan, V.

    2014-06-01

    The thermodynamic property of the host-guest complexes formed between the curcumin, component of Indian Ayurvedic medicine turmeric, a drug molecule, with the supra molecule, p-t-butyl calix(8)arene was studied. p-t-Butyl calix(8)arene has been used as a host molecule and curcumin as a guest molecule. Optical absorption spectral studies were carried out to investigate the molecular recognition properties of p-t-butyl calix(8)arene with curcumin. The stochiometry of the host-guest complexes formed and the binding constant were determined. An interesting 1:1 and 4:1 stochiometric host-guest complexes were formed. Job's continuous method of variation and Benesi-Hildebrand expression were used for the determination of binding constant and the stochiometry of the host-guest complex formed.

  16. Extending ligand field molecular mechanics to modelling organometallic π-bonded systems: applications to ruthenium-arenes.

    PubMed

    Brodbeck, Ralf; Deeth, Robert J

    2011-11-14

    The ligand field molecular mechanics method has been extended to treat η(6)-arene ligands coordinated to a ruthenium(II) centre by employing a dummy atom located at the centroid of the arene ring and distributing the forces on the dummy to the arene carbon atoms. Angular overlap model parameters based on orbital energies derived from Kohn-Sham density functional theory (KS-DFT) calculations show that, relative to the Ru-dummy vector, the arene behaves as a very strong π donor and weak σ donor. Based on KS-DFT geometries, partial atomic charges and potential energy scans for a series of homoleptic and half sandwich complexes spanning arene, am(m)ine, imine, pyridyl, hydride and chloride ligands, a new LFMM force field has been developed which accurately reproduces the KS-DFT data. This FF was validated against 47 half-sandwich complexes obtained from the Cambridge Structural Database which, after minor corrections to account for the systematic errors between our chosen functional (BP86) and the experimental structures, yields a 'structurally tuned' FF where 93% of the Ru-L contacts are reproduced to 0.05 Å or better and all bar two bond lengths are within 0.1 Å of experiment. Over half the systems have non-hydrogen-atom rmsds of less than 0.5 Å. Larger differences are usually due to rotation of the arene moiety which is shown by ligand field molecular dynamics (LFMD) simulations to be an inherently low-energy process. Comparisons between LFMD and Car-Parrinello MD for [Ru(p-cymene)(ethylenediamine)Cl](+)show that LFMD is equally accurate but much faster enabling modelling of dynamic properties which occur on a timescale beyond the scope of CPMD. PMID:21792446

  17. [The Ion Identification and Molecular Logic Gate of a Thiacalix[4]arene Fluorescent Probe].

    PubMed

    Wu, Fu-yong; Yu, Mei; Mu, Lan; Zeng, Xi; Wang, Rui-xiao; Takehiko Yamato

    2016-01-01

    A disubstituted phthalimide-based thiacalix[4] arene derivative (probe s1) was synthesized from cone 1, 3-thiacalix[4] arene and hydroxyethyl phthalimide, with benzyl appended the lower edge of thiacalix[4]-arene by triazole ring in the 2,4 position. The relative fluorescence quantum yield of probe s1 is 0.43 in CH3CN solvent. The strong fluorescence emission of probe s1 at 390 nm wavelength can be selectively quenched by Fe3+ in DMF/H2O solution. Similarly, the presence of I- also induced a significant fluorescence quenching of probe s1 at 310 nm wavelength in CH3CN solution. Spectral titration and isothermal titration calorimetry were showed that probe s1 with Fe3+ or I- both form 1 : 1 complexes, the binding constants up to 10(5) and coordinate process were spontaneous. The linear ranges of fluorescence detect Fe3+ or I- were 1.0 x 10(-7) - 1.6 x 10(-4) mol x L(-1) and 1.0 x 10(-7) - 8.5 x 10(-5) mol x L(-1), detection limits were up to 2.30 x 10(-8) mol x L(-1) and 1.17 x 10(-8) mol x L(-1), respectively. Meanwhile, take advantage of identification and coordination action, a logic circuit constructed at the molecular level by controlling two input signals of Fe3+ and F-, which causing probe s1 cycling of fluorescence emission or quenching. IR spectrum speculated that the nitrogen atoms of triazole groups are involved in the complexation with Fe3+, while the hydrogen atoms of triazole groups were complexed with I- by hydrogen bonding. PMID:27228760

  18. The extraction of thorium by calix[6]arene columns for urine analysis.

    PubMed

    Mekki, S; Bouvier-Capely, C; Jalouali, R; Rebière, F

    2011-03-01

    Thorium is a natural alpha-emitting element occurring in various ores and has numerous industrial applications. Routine monitoring of potentially exposed workers is generally achieved through radiobioassay (urine and faeces). The procedures currently used for analysing actinides such as thorium in urine require lengthy chemical separation associated with long counting times by alpha-spectrometry due to low activity levels. Thus, their main drawback is that they are time-consuming, which limits the frequency and flexibility of individual monitoring. In this context, this study developed new radiochemical procedures based on the use of tertbutylcalix[6]arenes bearing three carboxylic acid groups or three hydroxamic acid groups. These previous works demonstrated that these macrocyclic molecules immobilised on an inert solid support are excellent extractants for uranium, plutonium and americium. In this study, the authors investigated the thorium extraction by calix[6]arene columns. Experiments were performed on synthetic solutions and on real urine samples. The influence of various parameters, such as the thorium solution pH and the column flow rate on thorium extraction, was studied. The results showed that both calix[6]arenes are efficient to extract thorium. Thorium extraction is quantitative from pH = 2 for synthetic solution and from pH = 3 for real urine samples. This study has demonstrated that the column flow rate is a crucial parameter since its value must not be too high to achieve the steady-state complexation equilibrium. Finally, these results will be compared with those obtained for other actinides (U, Pu and Am) and the conditions of actinides' separation will be discussed. PMID:21159742

  19. Dual triggering of DNA binding and fluorescence via photoactivation of a dinuclear ruthenium(II) arene complex.

    PubMed

    Magennis, Steven W; Habtemariam, Abraha; Novakova, Olga; Henry, John B; Meier, Samuel; Parsons, Simon; Oswald, Iain D H; Brabec, Viktor; Sadler, Peter J

    2007-06-11

    The dinuclear RuII arene complexes [{(eta6-arene)RuCl}2(mu-2,3-dpp)](PF6)2, arene=indan (1), benzene (2), p-cymene (3), or hexamethylbenzene (4) and 2,3-dpp=2,3-bis(2-pyridyl)pyrazine, have been synthesized and characterized. Upon irradiation with UVA light, complexes 1 and 2 readily underwent arene loss, while complexes 3 and 4 did not. The photochemistry of 1 was studied in detail. In the X-ray structure of [{(eta6-indan)RuCl}2(mu-2,3-dpp)](PF6)2 (1), 2,3-dpp bridges two RuII centers 6.8529(6) A apart. In water, aquation of 1 in the dark occurs with replacement of chloride with biexponential kinetics and decay constants of 100+/-1 min-1 and 580+/-11 min-1. This aquation was suppressed by 0.1 M NaCl. UV or visible irradiation of 1 in aqueous or methanolic solution led to arene loss. The fluorescence of the unbound arene is approximately 40 times greater than when it is complexed. Irradiation of 1 also had a significant effect on its interactions with DNA. The DNA binding of 1 is increased after irradiation. The non-irradiated form of 1 preferentially formed DNA adducts that only weakly blocked RNA polymerase, while irradiation of 1 transformed the adducts into stronger blocks for RNA polymerase. The efficiency of irradiated 1 to form DNA interstrand cross-links was slightly greater than that of cisplatin in both 10 mM NaClO4 and 0.1 M NaCl. In contrast, the interstrand cross-linking efficiency of non-irradiated 1 in 10 mM NaClO4 was relatively low. An intermediate amount of cross-linking was observed when the sample of DNA already modified by non-irradiated 1 was irradiated. DNA unwinding measurements supported the conclusion that both mono- and bifunctional adducts with DNA can form. These results show that photoactivation of dinuclear RuII arene complexes can simultaneously produce a highly reactive ruthenium species that can bind to DNA and a fluorescent marker (the free arene). Importantly, the mechanism of photoreactivity is also independent of oxygen. These

  20. Sulfur dioxide and particles in quiescent volcanic plumes from Poas, Arenal, and Colima volcanos, Costa Rica and Mexico.

    USGS Publications Warehouse

    Casadevall, T.J.

    1984-01-01

    Measurements of SO2 emission rates and concentrations and of particle distribution, size, shape, and composition were made in quiescent volcanic plumes emitted into the troposphere from Poas and Arenal volcanos, Costa Rica, and Colima volcano, Mexico. SO2 emission rates were 700 +- 180 metric tons per day (t/d) for Poas, 210 +- 30 t/d for Arenal, and 320 +- 50 t/d for Colima. The concentrations of SO2 calculated from the COSPEC/lidar data were 5-380 ppb.-from Authors

  1. A novel colorimetric and fluorescent sensor based on calix[4]arene possessing triphenylamine units

    NASA Astrophysics Data System (ADS)

    Erdemir, Serkan; Malkondu, Sait; Kocyigit, Ozcan; Alıcı, Onder

    2013-10-01

    A novel colorimetric and fluorometric calix[4]arene probe (CTP) bearing triphenylamine units was synthesized in good yield and characterized by combination of 1H, 13C, APT, COSY, FTIR, HRMS, and UV-vis spectral data. Ion-binding studies of CTP were investigated in acetonitrile with a wide range of cations and anions and the recognition process was monitored by luminescence, UV-vis and 1H NMR spectral changes. CTP exhibited naked eye detection for Hg2+ ion. Also it showed a significant fluorescence quenching towards F- ion.

  2. Towards Uniform Iodine Catalysis: Intramolecular C-H Amination of Arenes under Visible Light.

    PubMed

    Martínez, Claudio; Bosnidou, Alexandra E; Allmendinger, Simon; Muñiz, Kilian

    2016-07-11

    A photochemical catalytic amination of arenes is presented. The reaction proceeds under benign iodine catalysis in the presence of visible light as the initiator and provides access to a range of differently substituted arylamines. A total of 29 examples demonstrate the broad applicability of this mild oxidation method. The scope of the reaction could further be expanded to silyl-tethered derivatives, which undergo intramolecular amination upon formation of seven-membered heterocycles. Cleavage of the silicon tether provides access to the corresponding 3-substituted anilines. PMID:27159628

  3. Catalytic dehydrogenation of cycloalkanes to arenes by a dihydrido iridium P-C-P pincer complex

    SciTech Connect

    Gupta, M.; Hagen, C.; Cramer, R.E.; Jensen, C.M.; Kaska, W.C.

    1997-01-29

    We recently found that the iridium P-C-P pincer complex IrH{sub 2}[C{sub 6}H{sub 3}-2,6-(CH{sub 2}-PBu{sup T}{sub 2}){sub 2}] (1) is a highly active, homogeneous catalyst for the transfer dehydrogenation of cyclooctane with unusual long-term stability at temperatures as high as 200 {degree}C. This reactivity has now been extended to the catalytic transfer dehydrogenation of cycloalkanes to arenes. We report this novel catalytic activity as well as the results of an X-ray structure determination of 1. 15 refs., 1 fig., 1 tab.

  4. Lithium Bromide/Water as Additives in Dearomatizing Samarium-Ketyl (Hetero)Arene Cyclizations.

    PubMed

    Rao, Chintada Nageswara; Bentz, Christoph; Reissig, Hans-Ulrich

    2015-11-01

    New conditions for dearomatizing samarium-ketyl (hetero)arene cyclizations are reported. In many examples of these samarium diiodide-mediated reactions, lithium bromide and water can be used as additives instead of the carcinogenic and mutagenic hexamethylphosphoramide (HMPA). The best results were obtained for the cyclizations of N-acylated indole derivatives delivering the expected indolines in good yields and excellent diastereoselectivities. A new type of cyclization delivering indolyl-substituted allene derivatives is also described. The scope and limitations of the lithium bromide/water system are discussed. PMID:26368916

  5. Direct transformation of esters into arenes with 1,5-bifunctional organomagnesium reagents.

    PubMed

    Link, Achim; Fischer, Christian; Sparr, Christof

    2015-10-01

    A direct transformation of carboxylic acid esters into arenes with 1,5-bifunctional organomagnesium reagents is described. This efficient and practical method enables the one-step defunctionalization of various carboxylic acid esters to prepare benzene, anthracene, tetracene, and pentacene derivatives. A double nucleophilic addition of the 1,5-organodimagnesium reagent to the ester is followed by an immediate 1,4-elimination reaction that leads to the direct [5+1] formation of a new aromatic ring. PMID:26291060

  6. Direct Synthesis of Polyaryls by Consecutive Oxidative Cross-Coupling of Phenols with Arenes.

    PubMed

    Dyadyuk, Alina; Sudheendran, Kavitha; Vainer, Yulia; Vershinin, Vlada; Shames, Alexander I; Pappo, Doron

    2016-09-01

    A bioinspired iron-catalyzed consecutive oxidative cross-coupling reaction between a single phenolic unit and nucleophilic arenes was developed. This sustainable transformation offers a selective synthetic strategy for the preparation of complex polyaryl compounds directly from readily available phenols. With the aid of electron paramagnetic resonance spectroscopy, it was demonstrated that the groups ortho to the phenolic functionality (whether hydrogen, methyl, or methoxy) direct the regioselectivity (ortho, para, or meta via dienone-phenol rearrangement) and chemoselectivity (C-C coupling or C-O coupling) in this multistep process. PMID:27529128

  7. A bactericidal calix[4]arene-based nanoconstruct with amplified NO photorelease.

    PubMed

    Di Bari, Ivana; Picciotto, Roberta; Granata, Giuseppe; Blanco, Anna R; Consoli, Grazia M L; Sortino, Salvatore

    2016-09-14

    A hydrophobic N-dodecyl-3-(trifluoromethyl)-4-nitrobenzenamine has been synthesized as a suitable NO photodonor and encapsulated in a nanocontainer based on a polycationic calix[4]arene derivative, leading to a supramolecular micellar-like nanoassembly ca. 45 nm in diameter. Visible light excitation of this nanoconstruct triggers NO generation with an efficiency remarkably higher than that observed for the free NO photoreleaser. This amplified NO release results in considerable antibacterial activity against Staphylococcus aureus (ATCC 6538) and Pseudomonas aeruginosa (ATCC 9027) as representative Gram positive and Gram negative bacteria, respectively. PMID:27438008

  8. Noncovalent Complexation of Monoamine Neurotransmitters and Related Ammonium Ions by Tetramethoxy Tetraglucosylcalix[4]arene

    NASA Astrophysics Data System (ADS)

    Torvinen, Mika; Kalenius, Elina; Sansone, Francesco; Casnati, Alessandro; Jänis, Janne

    2012-02-01

    The noncovalent complexation of monoamine neurotransmitters and related ammonium and quaternary ammonium ions by a conformationally flexible tetramethoxy glucosylcalix[4]arene was studied by electrospray ionization Fourier transform ion cyclotron resonance (ESI-FTICR) mass spectrometry. The glucosylcalixarene exhibited highest binding affinity towards serotonin, norepinephrine, epinephrine, and dopamine. Structural properties of the guests, such as the number, location, and type of hydrogen bonding groups, length of the alkyl spacer between the ammonium head-group and the aromatic ring structure, and the degree of nitrogen substitution affected the complexation. Competition experiments and guest-exchange reactions indicated that the hydroxyl groups of guests participate in intermolecular hydrogen bonding with the glucocalixarene.

  9. Reconstruction of lava fields based on 3D and conventional images. Arenal volcano, Costa Rica.

    NASA Astrophysics Data System (ADS)

    Horvath, S.; Duarte, E.; Fernandez, E.

    2007-05-01

    Conventional air photographs, multi-spectral images and a map scale 1:10 000 were used to upgrade Arenal volcano's lava field. Arenal volcano located in NW Costa Rica has been active for 39 years. Fifty two days after the initial explosive events that opened three craters on the west flank, lava flows were erupted from crater A (1050 m) in September, 1968 and continued flowing until November, 1973. These lavas were the most voluminous of the eruption and the effusion rate of lava was relatively high in this period. In April, 1974 lava flows were erupted from crater C (1460 m) and continue to present time. Younger lava flows extended over uncovered ground to the south and southwest in the 1980s and early 1990s and onto the northern slopes in the 1990s and 2000s. Lava flows are becoming shorter and narrower with time. Therefore, the centre of mass of the whole lava flow-field has migrated closer to the vent. Above crater C a cone has been growing steadily, reaching a height of 1670 m, 36 m higher than the prehistoric Arenal cone by 2004. After 39 years of continuous emission of lava flows, the profile of Arenal volcano consists of a duplet of cones whose summits are separated by less than 500 meters. Most of the build up around the new cone comes from varied lava flows. For near 30 years volcano monitoring staff (from OVSICORI-UNA) has recorded field observations of regular and extraordinary events, in paper. Several drafts maps have been used for teaching, academic presentations and for graphic explanations to specific audiences and to the general public. An upgraded version was needed. The purpose of this work is to present the most recent lava flows giving a visual presentation of them by computer methods. Combined SIG techniques (Arc View 3.3) and ERDAS produced a base map in which layers containing the recorded lava flows from the recent 16 years, were depicted. Each lava flow has its own characteristics: direction, year of origin, width, length, surface texture

  10. Stereoselective Arene-Forming Aldol Condensation: Synthesis of Axially Chiral Aromatic Amides.

    PubMed

    Fäseke, Vincent C; Sparr, Christof

    2016-06-13

    The increasing awareness of the importance of amide atropisomers prompts the development of novel strategies for their selective preparation. Described herein is a method for the enantioselective synthesis of atropisomeric aromatic amides by an amine-catalyzed arene-forming aldol condensation. The high reactivity of the glyoxylic amide substrates enables a remarkably efficient construction of a new aromatic ring, which proceeds within minutes at ambient temperature to afford products with excellent stereoselectivity. The high rotational barriers of the reduced products highlight the utility of this stable, spatially organized chiral scaffold. PMID:27166995

  11. Stereoselective Arene-Forming Aldol Condensation: Synthesis of Configurationally Stable Oligo-1,2-naphthylenes.

    PubMed

    Lotter, Dominik; Neuburger, Markus; Rickhaus, Michel; Häussinger, Daniel; Sparr, Christof

    2016-02-18

    Structurally well-defined oligomers are fundamental for the functionality of natural molecular systems and key for the design of synthetic counterparts. Herein, we describe a strategy for the efficient synthesis of individual stereoisomers of 1,2-naphthylene oligomers by iterative building block additions and consecutive stereoselective arene-forming aldol condensation reactions. The catalyst-controlled atropoenantioselective and the substrate-controlled atropodiastereoselective aldol condensation reaction provide structurally distinct ter- and quaternaphthalene stereoisomers, which represent configurationally stable analogues of otherwise stereodynamic, helically shaped ortho-phenylenes. PMID:26799152

  12. One-Pot C-H Functionalization of Arenes by Diaryliodonium Salts.

    PubMed

    Reitti, Marcus; Villo, Piret; Olofsson, Berit

    2016-07-25

    A transition-metal-free, mild, and highly regioselective synthesis of nitroarenes from arenes has been developed. The products are obtained in a sequential one-pot reaction by nitration of iodine(III) reagents with two carbon ligands, which are formed in situ from iodine(I). This novel concept has been extended to formation of aryl azides, and constitutes an important step towards catalytic reactions with these hypervalent iodine reagents. An efficient nitration of isolated diaryliodonium salts has also been developed, and the mechanism is proposed to proceed by a [2,2] ligand coupling pathway. PMID:27272891

  13. Double partial cone conformation for Na{sub 8}(calix[6]arene sulfonate){center_dot}20.5H{sub 2}O and its parent acid

    SciTech Connect

    Atwood, J.L.; Juneja, R.K.; Orr, G.W.

    1992-09-09

    The chemistry of calixarenes has recently become a very active area of endeavor. Of the numerous stimulating findings to appear thus far in the literature, one of the most intriguing concerns the discovery of certain uranophiles by Shinkai. It was reported that calix[5]arene sulfonate, calix[6]arene sulfonate, and the two corresponding derivatives substituted at the base by carboxymethoxy groups, 1 with R{prime} = CH{sub 2}COOH, exhibited stability constants for the uranyl ion of K = 10{sup 18.4-19.2}. Indeed, in competition experiments these calixarenes showed selectivity factors of 10{sup 12-17} for uranyl over the Ni{sup 2+}, Zn{sup 2+}, and Cu{sup 2+} ions. This selectivity was attributed to a moderately rigid calix[6]arene structure which was preorganized to match the rather unusual pseudoplanar hexacoordination needs of the UO{sub 2}{sup 2+} ion. However, on the basis of this study this premise appears untenable. Considering the importance of the above mentioned findings, the structural chemistry of derivatives of calix[6]arene has been slow to develop. In the available selection it is difficult to find general conformational features, apart from the elliptical cone conformation exhibited by the parent p-tert-butycalix[6]arene. Since our group has found a rich and often surprising inclusion chemistry for calix[4]arene sulfonates, we decided to investigate the structure of calix[6]arene sulfonate and its alkali metal salts. 28 refs., 1 fig.

  14. Exchange Coupling Mediated Through-Bonds and Through-Space in Conformationally-Constrained Polyradical Scaffolds: Calix[4]arene Nitroxide Tetraradicals And Diradical

    PubMed Central

    Rajca, Andrzej; Mukherjee, Sumit; Pink, Maren; Rajca, Suchada

    2008-01-01

    Calix[4]arenes constrained to 1,3-alternate conformation and functionalized at the upper rim with four and two tert-butylnitroxides have been synthesized, and characterized by X-ray crystallography, magnetic resonance (EPR and 1H NMR) spectroscopy, and magnetic studies. The 1,3-alternate nitroxide tetraradical and diradical provide unique polyradical scaffolds for dissection of the through-bond and through-space intramolecular exchange couplings. In addition, detailed magnetic studies of the previously reported calix[4]arene nitroxide tetraradical, which possesses cone conformation in solution, reveal conformational dependence of exchange coupling. Through-bond coupling between the adjacent nitroxide radicals is mediated by the nitroxide-m-phenylene-CH2-m-phenylene-nitroxide coupling pathway, and through-space coupling is found between the diagonal nitroxide radicals at the conformationally-constrained N···N distance of 5–6 Å. Magnetic studies of the calix[4]arene polyradical scaffolds in frozen solutions show that the through-bond exchange coupling in the 1,3-alternate calix[4]arene tetraradical is antiferromagnetic, while that in cone calix[4]arene tetraradical is ferromagnetic. The through-space exchange couplings are antiferromagnetic in both cone and 1,3-alternate calix[4]arene tetraradical, as well as in the 1,3-alternate calix[4]arene diradical. The exchange coupling constants (|J/k|) are of the order of 1 Kelvin. PMID:17031963

  15. Thin-skinned mass-wasting responsible for edifice-wide deformation at Arenal Volcano

    NASA Astrophysics Data System (ADS)

    Ebmeier, Susanna; Biggs, Juliet; Muller, Cyril; Avard, Geoffroy

    2014-12-01

    The shape and stability of a volcano’s edifice depends on the relationship between eruption rate and the loss or redistribution of material due to erosion, mass-wasting or deformation. This work provides measurements of deformation and shallow mass-wasting at a stratovolcano immediately after an extended period of growth, and demonstrates that high rates of deformation can be associated with shallow edifice processes. We measure displacements and surface property changes on the upper flanks of Arenal, Costa Rica, after a ~40 year period of edifice growth. We present high-resolution satellite radar imagery of the 2011-2013 period that provides evidence of frequent rockfalls and of at least 16 slow-moving, shallow landslides (estimated to be 5-11 m thick, total volume = 2.4×107 m3 DRE). The 2012 Nicoya Earthquake (Mw 7.4) had no measurable impact on the velocities of sliding units at Arenal, but did result in an increase in the area affected by rockfall.

  16. Photo-induced DNA cleavage and cytotoxicity of a ruthenium(II) arene anticancer complex.

    PubMed

    Brabec, Viktor; Pracharova, Jitka; Stepankova, Jana; Sadler, Peter J; Kasparkova, Jana

    2016-07-01

    We report DNA cleavage by ruthenium(II) arene anticancer complex [(η(6)-p-terp)Ru(II)(en)Cl](+) (p-terp=para-terphenyl, en=1,2-diaminoethane, complex 1) after its photoactivation by UVA and visible light, and the toxic effects of photoactivated 1 in cancer cells. It was shown in our previous work (T. Bugarcic et al., J. Med. Chem. 51 (2008) 5310-5319) that this complex exhibits promising toxic effects in several human tumor cell lines and concomitantly its DNA binding mode involves combined intercalative and monofunctional (coordination) binding modes. We demonstrate in the present work that when photoactivated by UVA or visible light, 1 efficiently photocleaves DNA, also in hypoxic media. Studies of the mechanism underlying DNA cleavage by photoactivated 1 reveal that the photocleavage reaction does not involve generation of reactive oxygen species (ROS), although contribution of singlet oxygen ((1)O2) to the DNA photocleavage process cannot be entirely excluded. Notably, the mechanism of DNA photocleavage by 1 appears to involve a direct modification of mainly those guanine residues to which 1 is coordinatively bound. As some tumors are oxygen-deficient and cytotoxic effects of photoactivated ruthenium compounds containing {Ru(η(6)-arene)}(2+) do not require the presence of oxygen, this class of ruthenium complexes may be considered potential candidate agents for improved photodynamic anticancer chemotherapy. PMID:26778426

  17. Palladium-catalysed norbornene-mediated C-H functionalization of arenes

    NASA Astrophysics Data System (ADS)

    Ye, Juntao; Lautens, Mark

    2015-11-01

    The Catellani reaction -- a palladium-catalysed C-H functionalization reaction mediated by norbornene -- was first reported in 1997. The capacity to functionalize both the ortho and ipso positions of aryl halides in a single transformation held great appeal. We reported an annulative Catellani reaction in 2000. Since then, our two groups have explored the synthetic utility of this reaction and dramatic progress has been made by a number of groups in the past five years. Whereas the original Catellani reaction uses Pd(0) catalysts, recent studies have shown that Pd(II) catalysts can be used in combination with norbornene to effect (1) direct 2-alkylation of indoles and pyrroles and (2) selective meta-C-H functionalization of arenes bearing commonly used ortho-directing groups, thereby opening new avenues for future research. We describe the most recent developments concerning the Pd-catalysed norbornene-mediated C-H functionalization of arenes, including applications in natural products synthesis. We outline challenges and future opportunities.

  18. Fine control on the photochemical and photobiological properties of Ru(II) arene complexes.

    PubMed

    Chen, Yongjie; Lei, Wanhua; Hou, Yuanjun; Li, Chao; Jiang, Guoyu; Zhang, Baowen; Zhou, Qianxiong; Wang, Xuesong

    2015-04-28

    A series of six Ru(arene) complexes, [(η(6)-p-cymene)Ru(dpb)(py-R)](2+) (1-6, dpb = 2,3-bis(2-pyridyl)benzoquinoxaline, py-R = 4-substituted pyridine, R = N(CH3)2, NH2, OCH3, H, COOCH3 and NO2), were synthesized and their photochemical and photobiological properties were compared in detail. The electron push/pull character of the R groups has a significant impact on both ligand photodissociation and (1)O2 generation of the complexes. The photoinduced DNA covalent binding capabilities increase from 1 to 6 under both aerobic and anaerobic conditions, and DNA photocleavage occurs simultaneously in aerobic environments. 4 has the most potent phototoxicity against human lung carcinoma A549 cells among the examined complexes. The substituent effect may be ascribed to the influences of the R groups on the energy levels of (3)MC and (3)MLCT states as well as the energy gaps between (3)MC, (3)MLCT and dpb-based (3)IL states. Similar chemical modification on bidentate and arene ligands or other sites of the pyridine ligand may lead to more efficient agents with PDT and/or PACT activities. PMID:25797273

  19. Synthesis and structures of O-anthrylmethyl-substituted hexahomotrioxacalix[3]arenes

    NASA Astrophysics Data System (ADS)

    Jiang, Xue-Kai; Ikejiri, Yusuke; Ni, Xi-Long; Zeng, Xi; Redshaw, Carl; Yamato, Takehiko

    2016-09-01

    O-Alkylation of 7,15,23-tri-tert-butyl-25,26,27-trihydroxy-2,3,10,11,18,19-hexahomo-3,11,19-trioxacalix[3]arene (1H3) with 9-chloromethylanthracene 5 was carried out under different reaction conditions. Variation of the number of anthrylmethyl group introduced at the phenolic rim of hexahomotrioxacalix[3]arene 1H3 was achieved through selective O-alkylation using stoichiometric amounts of 9-chloromethylanthracene 5 in acetone to afford the mono-O-alkylated product 2H2An, the di-O-alkylated product 3HAn2 and the tri-O-alkylated product partial-cone-4An3, respectively. Interestingly, by using an acetone/benzene (1:1 v/v) mixed solvent system, the cone-4An3 was successfully synthesized. These results suggest that the solvent can also control the conformation of the O-alkylation products. The possible reaction routes of the cone-4An3 and partial-cone-4An3 are also discussed.

  20. Radiosensitisation of human colorectal cancer cells by ruthenium(II) arene anticancer complexes

    PubMed Central

    Carter, R; Westhorpe, A; Romero, MJ; Habtemariam, A; Gallevo, CR; Bark, Y; Menezes, N; Sadler, PJ; Sharma, RA

    2016-01-01

    Some of the largest improvements in clinical outcomes for patients with solid cancers observed over the past 3 decades have been from concurrent treatment with chemotherapy and radiotherapy (RT). The lethal effects of RT on cancer cells arise primarily from damage to DNA. Ruthenium (Ru) is a transition metal of the platinum group, with potentially less toxicity than platinum drugs. We postulated that ruthenium-arene complexes are radiosensitisers when used in combination with RT. We screened 14 ruthenium-arene complexes and identified AH54 and AH63 as supra-additive radiosensitisers by clonogenic survival assays and isobologram analyses. Both complexes displayed facial chirality. At clinically relevant doses of RT, radiosensitisation of cancer cells by AH54 and AH63 was p53-dependent. Radiation enhancement ratios for 5–10 micromolar drug concentrations ranged from 1.19 to 1.82. In p53-wildtype cells, both drugs induced significant G2 cell cycle arrest and apoptosis. Colorectal cancer cells deficient in DNA damage repair proteins, EME1 and MUS81, were significantly more sensitive to both agents. Both drugs were active in cancer cell lines displaying acquired resistance to oxaliplatin or cisplatin. Our findings broaden the potential scope for these drugs for use in cancer therapy, including combination with radiotherapy to treat colorectal cancer. PMID:26867983

  1. Palladium-catalysed norbornene-mediated C-H functionalization of arenes.

    PubMed

    Ye, Juntao; Lautens, Mark

    2015-11-01

    The Catellani reaction--a palladium-catalysed C-H functionalization reaction mediated by norbornene--was first reported in 1997. The capacity to functionalize both the ortho and ipso positions of aryl halides in a single transformation held great appeal. We reported an annulative Catellani reaction in 2000. Since then, our two groups have explored the synthetic utility of this reaction and dramatic progress has been made by a number of groups in the past five years. Whereas the original Catellani reaction uses Pd(0) catalysts, recent studies have shown that Pd(II) catalysts can be used in combination with norbornene to effect (1) direct 2-alkylation of indoles and pyrroles and (2) selective meta-C-H functionalization of arenes bearing commonly used ortho-directing groups, thereby opening new avenues for future research. We describe the most recent developments concerning the Pd-catalysed norbornene-mediated C-H functionalization of arenes, including applications in natural products synthesis. We outline challenges and future opportunities. PMID:26492005

  2. Integrated velocity field from ground and satellite geodetic techniques: application to Arenal volcano

    NASA Astrophysics Data System (ADS)

    Muller, Cyril; del Potro, Rodrigo; Biggs, Juliet; Gottsmann, Joachim; Ebmeier, Susanna K.; Guillaume, Sébastien; Cattin, Paul-Henri; Van der Laat, Rodolfo

    2015-02-01

    Measurements of ground deformation can be used to identify and interpret geophysical processes occurring at volcanoes. Most studies rely on a single geodetic technique, or fit a geophysical model to the results of multiple geodetic techniques. Here we present a methodology that combines GPS, Total Station measurements and InSAR into a single reference frame to produce an integrated 3-D geodetic velocity surface without any prior geophysical assumptions. The methodology consists of five steps: design of the network, acquisition and processing of the data, spatial integration of the measurements, time series computation and finally the integration of spatial and temporal measurements. The most significant improvements of this method are (1) the reduction of the required field time, (2) the unambiguous detection of outliers, (3) an increased measurement accuracy and (4) the construction of a 3-D geodetic velocity field. We apply this methodology to ongoing motion on Arenal's western flank. Integration of multiple measurement techniques at Arenal volcano revealed a deformation field that is more complex than that described by individual geodetic techniques, yet remains consistent with previous studies. This approach can be applied to volcano monitoring worldwide and has the potential to be extended to incorporate other geodetic techniques and to study transient deformation.

  3. Direct Synthesis of 5-Aryl Barbituric Acids by Rhodium(II)-Catalyzed Reactions of Arenes with Diazo Compounds**

    PubMed Central

    Best, Daniel; Burns, David J; Lam, Hon Wai

    2015-01-01

    A commercially available rhodium(II) complex catalyzes the direct arylation of 5-diazobarbituric acids with arenes, allowing straightforward access to 5-aryl barbituric acids. Free N—H groups are tolerated on the barbituric acid, with no complications arising from N—H insertion processes. This method was applied to the concise synthesis of a potent matrix metalloproteinase (MMP) inhibitor. PMID:25959544

  4. Adsorption of remazol yellow FG from aqueous solution on chitosan-linked P-T-Butylcalix[4]Arene

    NASA Astrophysics Data System (ADS)

    Suci Handayani, Desi; Purnawan, Candra; Pranoto; Hastuti, Sri; Hilmiyana, Diniyah

    2016-02-01

    Chitosan-liked p-t-butylcalix[4]arene can be applied as an adsorbent of dye Remazol Yellow FG because it has an active group of hydroxy (-OH) and amine (-NH2). Adsorption had done by comparing to chitosan. Adsorption was carried out in a batch system. Several variables including pH, contact time, and initial concentration of dye Remazol Yellow FG were determined. The optimum adsorption conditions of dye Remazol Yellow FG by chitosan dan chitosan-liked p-t-butylcalix[4]arene occurred at pH 4 and a contact time of 135 minutes. The adsorption kinetics of dye Remazol Yellow FG using chitosan and chitosan-liked p-t- butylcalix[4]arene followed Ho kinetics model, pseudo-second order and the rate constant of adsorption was 2.42 x 10-4 g/mg.menit and 3.63 x 10-4 g/mg.menit. The isothermal study showed that adsorption of dye Remazol Yellow FG using chitosan and chitosan-liked p-t- butylcalix[4]arene tends to follow the Langmuir isotherm, with adsorption energy was 24.92 kJ/mol and 32.21 kJ/mol.

  5. Why Aren't We There Yet? Taking Personal Responsibility for Creating an Inclusive Campus. An ACPA Publication

    ERIC Educational Resources Information Center

    Arminio, Jan, Ed.; Torres, Vasti, Ed.; Pope, Raechele L., Ed.

    2012-01-01

    Despite seeming endless debate and public attention given to the issue for several decades, those committed to creating welcoming and engaging campus environments for all students recognize that there is considerably more work to be done, and ask "Why aren't we there yet, and when will we be done?" While our campuses have evolved from being…

  6. Selective and effective binding of pillar[5,6]arenes toward secondary ammonium salts with a weakly coordinating counteranion.

    PubMed

    Li, Chunju; Shu, Xiaoyan; Li, Jian; Fan, Jiazeng; Chen, Zhenxia; Weng, Linhong; Jia, Xueshun

    2012-08-17

    The selective and effective binding of secondary ammoniums with a weakly coordinating tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (BArF) counteranion by per-ethylated pillar[5,6]arenes is reported. The construction of a first pillararene-based self-sorting system consisting of two wheels and two axles is also described. PMID:22866893

  7. Self-assembly of amphiphilic anionic calix[4]arenes and encapsulation of poorly soluble naproxen and flurbiprofen.

    PubMed

    Barbera, Lucia; Gattuso, Giuseppe; Kohnke, Franz H; Notti, Anna; Pappalardo, Sebastiano; Parisi, Melchiorre F; Pisagatti, Ilenia; Patanè, Salvatore; Micali, Norberto; Villari, Valentina

    2015-06-21

    Supramolecular aggregates formed through the association of an amphiphilic tetra-O-butylsulfonate calix[4]arene 1 were investigated in aqueous solution by a combination of different techniques (NMR, DLS and AFM). The ability of the micellar aggregates of calixarene 1 to increase the solubility of poorly water-soluble drugs was studied. PMID:25994422

  8. p-tert-Butyltetrathiatetramercaptocalix[4]arene as a sulfur-rich platform for molybdenum, tungsten and nickel.

    PubMed

    Buccella, Daniela; Parkin, Gerard

    2009-01-21

    p-tert-Butyltetrathiatetramercaptocalix[4]arene, [S(4)Calix(Bu(t))(SH)(4)], reacts with Mo(PMe(3))(6), W(PMe(3))(4)(eta(2)-CH(2)PMe(2))H and Ni(PMe(3))(4) to yield molybdenum, tungsten and nickel compounds in a sulfur-rich coordination environment. PMID:19209305

  9. Ti(IV)-catalyzed cascade synthesis of tetrahydrofuro[3,2-d]oxazole from arene-1,4-diones.

    PubMed

    Li, Gang; Li, Li; Huang, Haihong; Yin, Dali

    2015-04-21

    A tetrahydrofuro[3,2-d]oxazole scaffold was synthesized efficiently and stereoselectively. The tandem ionic hydrogenation, ketalization, and intramolecular cyclization of arene-1,4-diones with a combination of TiCl4/Et3SiH give facile access to tetrahydrofuro[3,2-d]oxazole derivatives in good yields at room temperature. PMID:25777364

  10. Ditopic CMPO-pillar[5]arenes as unique receptors for efficient separation of americium(III) and europium(III).

    PubMed

    Fang, Yuyu; Yuan, Xiangyang; Wu, Lei; Peng, Zhiyong; Feng, Wen; Liu, Ning; Xu, Dingguo; Li, Shoujian; Sengupta, Arijit; Mohapatra, Prasanta K; Yuan, Lihua

    2015-03-11

    A unique host-guest recognition process involving a new class of homoditopic CMPO-pillar[5]arenes and lanthanides was revealed to proceed in a stepwise manner, and correlated with the efficient separation of americium(III) and europium(III) under acidic feed conditions. PMID:25671799

  11. Tuning Reactivity and Site Selectivity of Simple Arenes in C–H Activation: Ortho-Arylation of Anisoles via Arene–Metal π-Complexation

    PubMed Central

    2014-01-01

    Current approaches to achieve site selectivity in the C–H activation of arenes involve the use of directing groups or highly electron-poor arenes. In contrast, simple arenes, such as anisole, are characterized by poor reactivity and selectivity. We report that π-complexation to a Cr(CO)3 unit enhances the reactivity of anisoles providing an unprecedented ortho-selective arylation. This mild methodology can be used for the late stage functionalization of bioactive compounds containing the anisole motif, allowing the construction of novel organic scaffolds with few synthetic steps. PMID:25510851

  12. [Cu(NHC)]-Catalyzed C-H Allylation and Alkenylation of both Electron-Deficient and Electron-Rich (Hetero)arenes with Allyl Halides.

    PubMed

    Xie, Weilong; Chang, Sukbok

    2016-01-26

    New reactivity of a [Cu(NHC)] (NHC=N-heterocyclic carbene) catalyst is disclosed for the efficient C-H allylation of polyfluoroarenes using allyl halides in benzene at room temperature. The same catalyst system also promotes an isomerization-induced alkenylation of initially the generated allyl arenes when the reaction is run in tetrahydrofuran. Significantly, not only electron-deficient but also electron-rich (hetero)arenes undergo this double-bond migration process, thus leading to alkenylated products. The present system features mild reaction conditions, broad scope with respect to the arene substrates and allyl halide reactants, good functional-group tolerance, and high stereoselectivity. PMID:26695120

  13. Field reconnaissance of the effects of the earthquake of April 13, 1973, near Laguna de Arenal, Costa Rica

    USGS Publications Warehouse

    Plafker, George

    1973-01-01

    At about 3:34 a.m. on April 13, 1973, a moderate-sized, but widely-felt, earthquake caused extensive damage with loss of 23 lives in a rural area of about 150 km2 centered just south of Laguna de Arenal in northwestern Costa Rica (fig. 1). This report summarizes the results of the writer's reconnaissance investigation of the area that was affected by the earthquake of April 13, 1973. A 4-day field study of the meizoseismal area was carried out during the period from April 28 through May 1 under the auspices of the U.S. Geological Survey. The primary objective of this study was to evaluate geologic factors that contributed to the damage and loss of life. The earthquake was also of special interest because of the possibility that it was accompanied by surface faulting comparable to that which occurred at Managua, Nicaragua, during the disastrous earthquake of December 23, 1972 (Brown, Ward, and Plafker, 1973). Such earthquake-related surface faulting can provide scientifically valuable information on active tectonic processes at shallow depths within the Middle America arc. Also, identification of active faults in this area is of considerable practical importance because of the planned construction of a major hydroelectrical facility within the meizoseismal area by the Instituto Costarricense de Electricidad (I.C.E.). The project would involve creation of a storage reservoir within the Laguna de Arenal basin and part of the Río Arenal valley with a 75 m-high earthfill dam across Río Arenal at a point about 10 km east of the outlet of Laguna de Arenal.

  14. Complex behavior and source model of the tremor at Arenal volcano, Costa Rica

    NASA Astrophysics Data System (ADS)

    Lesage, Philippe; Mora, Mauricio M.; Alvarado, Guillermo E.; Pacheco, Javier; Métaxian, Jean-Philippe

    2006-09-01

    Typical records of volcanic tremor and explosion quakes at Arenal volcano are analyzed with a high-resolution time-frequency method. The main characteristics of these seismic signals are: (1) numerous regularly spaced spectral peaks including both odd and even overtones; (2) frequency gliding in the range [0.9-2] Hz of the fundamental peak; (3) frequency jumps with either positive or negative increments; (4) tremor episodes with two simultaneous systems of spectral peaks affected by independent frequency gliding; (5) progressive transitions between spasmodic tremor and harmonic tremor; (6) lack of clear and systematic relationship between the occurrence of explosions and tremor. Some examples of alternation between two states of oscillation characterized by different fundamental frequencies are also observed. Some tremor and explosion codas are characterized by acoustic and seismic waves with identical spectral content and frequency gliding, which suggests a common excitation process. We propose a source model for the tremor at Arenal in which intermittent gas flow through fractures produces repetitive pressure pulses. The repeating period of the pulses is stabilized by a feedback mechanism associated with standing or traveling waves in the magmatic conduit. The pressure pulses generate acoustic waves in the atmosphere and act as excitation of the interface waves in the conduit. When the repeating period of the pulses is stable enough, they produce regularly spaced spectral peaks by the Dirac comb effect and hence harmonic tremor. When the period stability is lost, because of failures in the feedback mechanism, the tremor becomes spasmodic. The proposed source model of tremor is similar to the sound emission process of a clarinet. Fractures in the solid or viscous layer capping the lava pool in the crater act as the clarinet reed, and the conduit filled with low velocity bubbly magma is equivalent to the pipe of the musical instrument. The frequency gliding is

  15. Reversible formation of supramolecular polymer networks via orthogonal pillar[10]arene-based host-guest interactions and metal ion coordinations.

    PubMed

    Wu, Lintao; Han, Chun; Wu, Xi; Wang, Lei; Caochen, Yaozi; Jing, Xiaobi

    2015-12-21

    Supramolecular polymer networks, assembled via the combination of orthogonal terpyridine-Zn(2+), carbene-Ag(+), and pillar[10]arene/alkyl chain recognition motifs, exhibit dynamic properties responsive to various external stimuli. PMID:26569051

  16. Facile and efficient formation and dissociation of a pseudo[2]rotaxane by a slippage approach using pillar[5]arene-based cyclic host liquid and solvent.

    PubMed

    Ogoshi, Tomoki; Tamura, Yuko; Yamafuji, Daiki; Aoki, Takamichi; Yamagishi, Tada-Aki

    2016-08-11

    A pillar[5]arene-based pseudo[2]rotaxane was synthesized using a slippage method by only heating an axle with bulky valine derivative ends in a cyclic host liquid (CHL), which is liquid at room temperature. The pseudo[2]rotaxane synthesized in a CHL can be converted back to the starting components, i.e., the pillar[5]arene wheel and the axle, by heating in a solvent. PMID:27471989

  17. Synthesis of two distinct pyrrole moiety-containing arenes from nitroanilines using Paal-Knorr followed by an indium-mediated reaction.

    PubMed

    Kim, Byeong Hyo; Bae, Seolhee; Go, Ahra; Lee, Hyunseung; Gong, Cheoloh; Lee, Byung Min

    2016-01-01

    Synthesis of arenes substituted with two differently substituted-pyrrole moieties was investigated. A Paal-Knorr condensation reaction of nitroanilines with 1,4-diketone to nitrophenyl-1H-pyrroles followed by an indium-mediated reduction-triggered coupling reaction with another kind of 1,4-diketone resulted in two distinct pyrrole-containing arenes, variously substituted 1-((1H-pyrrol-1-yl)phenyl)-1H-pyrroles, in reasonable yield. PMID:26593044

  18. Troponate/Aminotroponate Ruthenium-Arene Complexes: Synthesis, Structure, and Ligand-Tuned Mechanistic Pathway for Direct C-H Bond Arylation with Aryl Chlorides in Water.

    PubMed

    Dwivedi, Ambikesh D; Binnani, Chinky; Tyagi, Deepika; Rawat, Kuber S; Li, Pei-Zhou; Zhao, Yanli; Mobin, Shaikh M; Pathak, Biswarup; Singh, Sanjay K

    2016-07-01

    A series of water-soluble troponate/aminotroponate ruthenium(II)-arene complexes were synthesized, where O,O and N,O chelating troponate/aminotroponate ligands stabilized the piano-stool mononuclear ruthenium-arene complexes. Structural identities for two of the representating complexes were also established by single-crystal X-ray diffraction studies. These newly synthesized troponate/aminotroponate ruthenium-arene complexes enable efficient C-H bond arylation of arylpyridine in water. The unique structure-activity relationship in these complexes is the key to achieve efficient direct C-H bond arylation of arylpyridine. Moreover, the steric bulkiness of the carboxylate additives systematically directs the selectivity toward mono- versus diarylation of arylpyridines. Detailed mechanistic studies were performed using mass-spectral studies including identification of several key cyclometalated intermediates. These studies provided strong support for an initial cycloruthenation driven by carbonate-assisted deprotonation of 2-phenylpyridine, where the relative strength of η(6)-arene and the troponate/aminotroponate ligand drives the formation of cyclometalated 2-phenylpyridine Ru-arene species, [(η(6)-arene)Ru(κ(2)-C,N-phenylpyridine) (OH2)](+) by elimination of troponate/aminotroponate ligands and retaining η(6)-arene, while cyclometalated 2-phenylpyridine Ru-troponate/aminotroponate species [(κ (2)-troponate/aminotroponate)Ru(κ(2)-C,N-phenylpyridine)(OH2)2] was generated by decoordination of η(6)-arene ring during initial C-H bond activation of 2-phenylpyridine. Along with the experimental mass-spectral evidence, density functional theory calculation also supports the formation of such species for these complexes. Subsequently, these cycloruthenated products activate aryl chloride by facile oxidative addition to generate C-H arylated products. PMID:27305143

  19. The Olefin Metathesis Reactions Combined with Organo-Iron Arene Activation Towards Dendrimers, and Polymers

    NASA Astrophysics Data System (ADS)

    Astruc, Didier; Martinez, Victor

    The subjects treated in the two lectures of the North Atlantic Treaty Organization (NATO) summer course are (1) the combination of arene activation and perfunctionalization using organo-iron chemistry with olefin metathesis incuding metathesis of dendritic polyolefin molecules; (2) the synthesis of metallodendritic benzylidene complexes that catalyse ring-opening metathesis polymerization (ROMP) under ambient conditions and the formation of dendritic stars; (3) the use of stoichiometric and catalytic electron-transfer processes with standard reservoirs of electrons (reductants) or electron holes (oxidants) iron complexes to achieve noteworthy metathesis reactions or synthesize compounds that are useful in metathesis. Only the two first topics are treated in this chapter, and interested readers can find references concerning the third aspect called in the introduction and subsequently cited in the reference list.

  20. Calix[4]arene coated QCM sensors for detection of VOC emissions: Methylene chloride sensing studies.

    PubMed

    Temel, Farabi; Tabakci, Mustafa

    2016-06-01

    This paper describes the sensing studies of QCM sensors with coated some calixarene derivatives bearing different functional groups for some selected Volatile Organic Compounds (VOCs) such as acetone, acetonitrile, carbon tetrachloride, chloroform, methylene chloride (MC), N,N-dimethylformamide, 1,4-dioxane, ethanol, ethyl acetate, xylene, methanol, n-hexane and toluene. The initial experiments have revealed that whole the calix[4]arene modified QCM sensors exhibited strongest sensing ability to MC emissions. Thus, the detailed studies were performed for only MC emissions after the determination of relatively more effective calix-coated QCM sensors for MC emissions in aqueous media. The results demonstrated that QCM sensor coated with calix-7 bearing both amino and imidazole groups was most useful sensor for MC emissions with 54.1ppm of detection limit. Moreover, it was understood that cyclic structures, H-bonding capabilities and also good preorganization properties of calixarene derivatives played an important role in VOC sensing processes. PMID:27130112

  1. Calix(6)arene carboxylate derivative for solvent extraction separation of iron(III).

    PubMed

    Khandwe, R M; Khopkar, S M

    1998-08-01

    Hexaacetatocalix(6)arene was used for the solvent extraction of iron(III). About 7.5x10(-2) M extractant was used at pH 7.0 for the quantitative extraction of iron(III). The metal from the organic phase was stripped with 1.0 M hydrochloric acid and determined spectrophotometrically as its thiocyanate complex at 480 nm. Iron(III) was separated from large excesses of alkali and alkaline earths in the ratio 1:20. The transition and main group elements were tolerated in the ratio 1:10. The method was extended for the analysis of iron from its mineral, alloy and pharmaceutical preparation. The method is reproducible with SD+/-1.10%. PMID:18967172

  2. Antiproliferative activity of ruthenium(ii) arene complexes with mono- and bidentate pyridine-based ligands.

    PubMed

    Richter, Stefan; Singh, Sushma; Draca, Dijana; Kate, Anup; Kumbhar, Anupa; Kumbhar, Avinash S; Maksimovic-Ivanic, Danijela; Mijatovic, Sanja; Lönnecke, Peter; Hey-Hawkins, Evamarie

    2016-08-16

    A series of Ru(II) arene complexes of mono- and bidentate N-donor ligands with carboxyl or ester groups and chlorido ancillary ligands were synthesised and structurally characterised. The complexes have a distorted tetrahedral piano-stool geometry. The binding interaction was studied with calf thymus DNA (CT-DNA) by absorption titration, viscosity measurement, thermal melting, circular dichroism, ethidium bromide displacement assay and DNA cleavage of plasmid DNA (pBR322), investigated by gel electrophoresis. The dichlorido complexes bind covalently to DNA in the dark, similar to cisplatin, while the monochlorido complexes bind covalently on irradiation, similar to cisplatin analogues. The compounds are selectively cytotoxic against several tumour cell lines and show specific nonlinear correlation between dose and activity. This phenomenon is closely related to their potential to act preferentially as inhibitors of cell division. PMID:27264161

  3. Conformational features of an actuator containing calix[4]arene and thiophene: a molecular dynamics study.

    PubMed

    Zanuy, David; Casanovas, Jordi; Aleman, Carlos

    2006-05-25

    Molecular dynamics simulations have been performed for poly(calix[4]arene bis(bithiophene)) in dichloromethane solution. This material responds to its electronic structure variations with significant conformational changes, producing contraction-expansion movements. Simulations have been performed for the three states of this molecular actuator (reduced, oxidized-nondeprotonated, and oxidized-deprotonated), a specific force-field being developed for each case. Results, which are fully consistent with previous ab initio quantum mechanical calculations on an isolated actuating unit, have revealed important findings about the dynamics of the system. Analyses of the flexibility/rigidity of the molecular chain with the state, the interaction of the polymer with the solvent molecules and the influence of environmental factors (as the viscosity of solvent, the counterions and the thermal agitation) on the dynamics have provided important insights to the actuation mechanism. PMID:16706442

  4. Calix[4]arene Based Dual Fluorescent Sensor for Al(3+) and S2O7 (2.).

    PubMed

    Memon, Shahabuddin; Bhatti, Ashfaque Ali; Bhatti, Asif Ali; Ocak, Ümmühan; Ocak, Miraç

    2016-09-01

    Specific functionalized calix[4]arene based fluorescent chemosensor was synthesized for cations and anions binding efficiency examination. Receptor C4MA displayed strong affinity for Al(3+)and S2O7 (2-) with enhanced fluorescence intensity. The selective response of C4MA was investigated in the presence of different co-existing competing ions. The limit of detection (LOD) of Al(3+)and S2O7 (2-) was calculated as 2.8 × 10(-6) M and 2.6 × 10(-7) M respectively. Sensor C4MA forms (1:1) stoichiometric complex with both Al(3+) and S2O7 (2-) and their binding constants were calculated as 12.1 × 10(4) and 8.3 × 10(3) respectively. Complexes were also characterized through FT-IR spectroscopy. Graphical Abstract ᅟ. PMID:27324953

  5. Conformational changes of a calix[8]arene derivative at the air-water interface.

    PubMed

    de Miguel, Gustavo; Pedrosa, José M; Martín-Romero, María T; Muñoz, Eulogia; Richardson, Tim H; Camacho, Luis

    2005-03-10

    The particular behavior of a p-tert-butyl calix[8]arene derivative (C8A) has been studied at the air-water interface using surface pressure-area isotherms, surface potential-area isotherms, film relaxation measurements, Brewster angle microscopy (BAM), and infrared spectroscopy for Langmuir-Blodgett films. Thus, it is observed that the properties of the film, for example, isotherms, domain formation, and FTIR spectra, recorded during the first compression cycle differ appreciably from those during the second compression and following cycles. The results obtained are interpreted on the basis of the conformational changes of the C8A molecules by surface pressure, allowing us to inquire into the inter- and intramolecular interactions (hydrogen bonds) of those molecules. Thus, the compression induces changes in the kind of hydrogen bonds from intra- and intermolecular with other C8A molecules to hydrogen bonds with water molecules. PMID:16851456

  6. Tetranuclear manganese(II) complexes of sulfonylcalix[4]arene macrocycles: synthesis, structure, spectroscopic and magnetic properties.

    PubMed

    Lamouchi, Meriem; Jeanneau, Erwann; Pillonnet, Anne; Brioude, Arnaud; Martini, Matteo; Stéphan, Olivier; Meganem, Faouzi; Novitchi, Ghenadie; Luneau, Dominique; Desroches, Cédric

    2012-03-01

    Two tetranuclear manganese(II) complexes {K(+)[Mn(4)(ThiaSO(2))(2)(OH)](-)} (1) and {K(+)[Mn(4)(ThiaSO(2))(2)(F)](-)} (2) have been synthesized under solvothermal conditions in methanol with p-tert-butylsulfonylcalix[4]arene (ThiaSO(2)). For both complexes, the structure has been established from single-crystal X-ray diffraction. The two complexes are best described as manganese squares sandwiched between two thiacalixarene macrocycles. In both complexes, in the center of the square formed by the four manganese(II) atoms, the unexpected presence of μ(4)-OH(-) or μ(4)-F(-) gives a negative charge to the cluster. The two tetranuclear complexes exhibit strong orange luminescence behavior resulting from the symbiosis between the ThiaSO(2) and the Mn(2+). Despite similar chemical formulation, (1) and (2) present difference in emission intensity and lifetime τ. PMID:22266843

  7. Survey on the complexation character of p-sulfonatocalix[n]arenes and Caffeic acid

    NASA Astrophysics Data System (ADS)

    Chao, Jianbin; Liu, Yuhong; Zhang, Yan; Wang, Yu; Zhao, Wei; Zhang, Bingtai

    2014-11-01

    In this work the inclusion complex formation of Caffeic acid (CA) with p-sulfonatocalix[n]arenes (SCXn, n = 4, 6, 8) is reported aiming to improve the antioxidant activity, thermal stability and photostability properties of CA. Evidence for the formation was obtained using fluorescence spectroscopy, nuclear magnetic resonance spectroscopy (NMR), pulsed field gradient NMR (PFG-NMR), Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC) and scanning electron microphotographs (SEM). Experimental conditions including concentrations of SCXn and pH were investigated for the inclusion formation in detail. The results showed that CA was able to form inclusion complexes with SCXn in a molar ratio of 1:1, and the formation constants were varied with the pH conditions. NMR spectroscopy indicated that both the aromatic ring and the vinyl group of CA were partially covered by SCXn.

  8. Synthesis and evaluation of novel tetrapropoxycalix[4]arene enones and cinnamates for protection from ultraviolet radiation.

    PubMed

    Chawla, H M; Pant, Nalin; Kumar, Satish; Mrig, Sarika; Srivastava, Bindu; Kumar, Naresh; Black, D Stc

    2011-10-01

    A series of novel calix[4]arene enones (5-7) and cinnamates (12-14) have been synthesized and evaluated for ensuring protection from ultraviolet radiation (UVR). Spectroscopic analyses has revealed that compound 6 absorbs ultraviolet radiations between 280 and 350 nm with an absorption maximum at 312 nm. Its molar absorption coefficient (ε) (>5 × 10(4)M(-1)cm(-1)) and bandwidth are larger than those for the commercially used sun protectants (oxybenzone (OB), 2-ethylhexyl 4-methoxycinnamate (OMC) and avobenzone). The in vitro Sun Protection Factor (SPF) measurement revealed an SPF of 5.2 at 2% concentration of 6 in home made emulsion formulations while combination of 2% each of 6 and OMC gave an SPF of 8.8. Lower sun protection seems to be compensated by significant protection from more harmful UVA radiations (UVA/UVB absorbance ratio of 0.62). PMID:21803597

  9. Interplay of ortho- with spiro-cyclisation during iminyl radical closures onto arenes and heteroarenes

    PubMed Central

    2013-01-01

    Summary Sensitised photolyses of ethoxycarbonyl oximes of aromatic and heteroaromatic ketones yielded iminyl radicals, which were characterised by EPR spectroscopy. Iminyls with suitably placed arene or heteroarene acceptors underwent cyclisations yielding phenanthridine-type products from ortho-additions. For benzofuran and benzothiophene acceptors, spiro-cyclisation predominated at low temperatures, but thermodynamic control ensured ortho-products, benzofuro- or benzothieno-isoquinolines, formed at higher temperatures. Estimates by steady-state kinetic EPR established that iminyl radical cyclisations onto aromatics took place about an order of magnitude more slowly than prototypical C-centred radicals. The cyclisation energetics were investigated by DFT computations, which gave insights into factors influencing the two cyclisation modes. PMID:23766822

  10. Catalytic synthesis of n-alkyl arenes through alkyl group cross-metathesis.

    PubMed

    Dobereiner, Graham E; Yuan, Jian; Schrock, Richard R; Goldman, Alan S; Hackenberg, Jason D

    2013-08-28

    n-Alkyl arenes were prepared in a one-pot tandem dehydrogenation/olefin metathesis/hydrogenation sequence directly from alkanes and ethylbenzene. Excellent selectivity was observed when ((tBu)PCP)IrH2 was paired with tungsten monoaryloxide pyrrolide complexes such as W(NAr)(C3H6)(pyr)(OHIPT) (1a) [Ar = 2,6-i-Pr2C6H3; pyr = pyrrolide; OHIPT = 2,6-(2,4,6-i-Pr3C6H2)2C6H3O]. Complex 1a was also especially active in n-octane self-metathesis, providing the highest product concentrations reported to date. The thermal stability of selected olefin metathesis catalysts allowed elevated temperatures and extended reaction times to be employed. PMID:23909821

  11. Pillar[5]arene-Based Glycoclusters: Synthesis and Multivalent Binding to Pathogenic Bacterial Lectins.

    PubMed

    Buffet, Kevin; Nierengarten, Iwona; Galanos, Nicolas; Gillon, Emilie; Holler, Michel; Imberty, Anne; Matthews, Susan E; Vidal, Sébastien; Vincent, Stéphane P; Nierengarten, Jean-François

    2016-02-24

    The synthesis of pillar[5]arene-based glycoclusters has been readily achieved by CuAAC conjugations of azido- and alkyne-functionalized precursors. The lectin binding properties of the resulting glycosylated multivalent ligands have been studied by at least two complementary techniques to provide a good understanding. Three lectins were selected from bacterial pathogens based on their potential therapeutic applications as anti-adhesives, namely LecA and LecB from Pseudomonas aeruginosa and BambL from Burkholderia ambifaria. As a general trend, multivalency improved the binding to lectins and a higher affinity can be obtained by increasing to a certain limit the length of the spacer arm between the carbohydrate subunits and the central macrocyclic core. PMID:26845383

  12. Enhancement of cytotoxicity by combining pyrenyl-dendrimers and arene ruthenium metallacages.

    PubMed

    Pitto-Barry, Anaïs; Zava, Olivier; Dyson, Paul J; Deschenaux, Robert; Therrien, Bruno

    2012-07-01

    Three generations of pyrenyl bis-MPA dendrimers with two different end-groups, acetonide (pyr(Gn)) or alcohol (pyr(Gn-OH)) (n = 1-3), were synthesized, and the pyrenyl group of the dendritic molecules was encapsulated in the arene ruthenium metallacages, [Ru(6)(p-cymene)(6)(OO∩OO)(3)(tpt)(2)](6+) (OO∩OO = 5,8-dioxydo-1,4-naphtaquinonato (donq) [1](6+) and 6,11-dioxydo-5,12-naphtacenedionato (dotq) [2](6+); tpt =2,4,6-tri(pyridin-4-yl)-1,3,5-triazine). The host-guest properties of [guest⊂1](6+) and [guest⊂2](6+) were studied in solution by NMR and UV-vis spectroscopic methods, thus allowing the determination of the affinity constants. Moreover, the cytotoxicity of these water-soluble host-guest systems and the pyrenyl-dendrimers was evaluated on human ovarian cancer cells. PMID:22716166

  13. Through-Space Effects of Substituents Dominate Molecular Electrostatic Potentials of Substituted Arenes

    PubMed Central

    Wheeler, Steven E.; Houk, K. N.

    2009-01-01

    Model systems have been studied using density functional theory to assess the contributions of π-resonance and through-space effects on electrostatic potentials of substituted arenes. The results contradict the widespread assumption that changes in molecular ESPs reflect only local changes in the electron density. Substituent effects on the ESP above the molecular plane are commonly attributed to changes in the aryl π-system. We show that ESP changes for a collection of substituted benzenes and more complex aromatic systems can be accounted for mostly by through-space effects, with no change in the aryl π-electron density. Only when π-resonance effects are substantial do they influence changes in the ESP above the aromatic ring to any extent. Examples of substituted arenes studied here are taken from the fields of drug design, host-guest chemistry, and crystal engineering. These findings emphasize the potential pitfalls of assuming ESP changes reflect changes in the local electron density. Since ESP changes are frequently used to rationalize and predict intermolecular interactions, these findings have profound implications for our understanding of substituent effects in countless areas of chemistry and molecular biology. Specifically, in many non-covalent interactions there are significant, often neglected, through-space interactions with the substituents. Finally, the present results explain the perhaps unexpectedly good performance of many molecular mechanics force-fields applied to supramolecular assembly phenomena and π-π interactions in biological systems despite the neglect of the polarization of the aryl π-system by substituents. PMID:20161573

  14. Palladium-catalyzed Cs2CO3-promoted arylation of unactivated C(sp(3))-H bonds by (diacetoxyiodo)arenes: shifting the reactivity of (diacetoxyiodo)arenes from acetoxylation to arylation.

    PubMed

    Gou, Quan; Zhang, Zhao-Fu; Liu, Zhi-Cheng; Qin, Jun

    2015-03-20

    PdCl2(CH3CN)2-catalyzed arylation of unactivated C(sp(3))-H bonds using (diacetoxyiodo)arenes as arylation reagents is reported. The reactivity of (diacetoxyiodo)arenes as arylation reagents is enabled in the presence of Cs2CO3 under the reaction conditions. This arylation method is highly efficient and occurs without the use of silver salt. The reaction tolerates a broad substrate scope that was not demonstrated by other silver salt-free C(sp(3))-H bond arylation conditions. The synthetic utility of the method is further illustrated in the synthesis of the psychotropic drug phenibut. A detailed mechanism study has been conducted to understand the reaction pathway. PMID:25763683

  15. The effect of temperatures and γ-ray irradiation on silica-based calix[4]arene-R14 adsorbent modified with surfactants for the adsorption of cesium from nuclear waste solution

    NASA Astrophysics Data System (ADS)

    Chen, Zi; Wu, Yan; Wei, Yuezhou

    2014-10-01

    1,3-[(2,4-Diethylheptylethoxy)oxy]-2,4-crown-6-Calix[4]arene(Calix[4]arene-R14), used as an extractant of Cs(I) from nitric acid, modified by dodecanol and dodecyl benzenesulfonic acid (DBS), was loaded into the pores of macroporous silica-based polymer support (SiO2-P) particles. To evaluate the stability of the adsorbent, the adsorption data at different temperatures (298-323 K) and γ-ray absorbed doses (10-200 kGy) were analyzed by the Langmuir isotherm. The minimum adsorbed amount was calculated to be 0.121 mmol g-1 at 323 K, approximately 23% reduction compared to 298 K. The maximum adsorbed amount of not-irradiated adsorbent with 0.156 mmol g-1 decreased by 20% than that irradiated in 0.5 M HNO3. The thermodynamic parameters have revealed that this adsorption reaction is an exothermic and spontaneous process. The reduction in 3 M HNO3 was about 45% by the comparison between the before- and after-irradiation. It was found that both the concentrations of HNO3 and DBS have significant influence on the degradation of the adsorbents.

  16. Selectivity of calix[4]arene-bis(benzocrown-6) in the complexation and transport of francium ion.

    PubMed

    Haverlock, Tamara J; Mirzadeh, Saed; Moyer, Bruce A

    2003-02-01

    It is shown for the first time that a representative member of the "cesium-selective" calix[4]arene-crown-6 family exhibits a high affinity for Fr+ ion. In the investigation, the transport of 221Fr+ and Cs+ ions by calix[4]arene-bis(benzocrown-6) from an aqueous sodium nitrate solution into the water-immiscible diluent 1,2-dichloroethane was measured and compared to address the question of selectivity of the calix-crown-6 cavity toward alkali metal ions of increasing size. Selective separation of 221Fr+ from its parent 225Ac and from the matrix Na+ ions was demonstrated. Higher distribution ratios were obtained than those for the Cs+ ion. The extraction equilibria were determined for the case of the Cs+ ion, and the same equilibria were shown to be applicable to the case of Fr+ with inclusion of additional competitive effects. PMID:12553788

  17. Phosphonium pillar[5]arenes as a new class of efficient biofilm inhibitors: importance of charge cooperativity and the pillar platform.

    PubMed

    Joseph, Roymon; Kaizerman, Dana; Herzog, Ido M; Hadar, Maya; Feldman, Mark; Fridman, Micha; Cohen, Yoram

    2016-08-23

    Biofilm formation, which frequently occurs in microbial infections and often reduces the efficacy of antibiotics, also perturbs many industrial and domestic processes. We found that a new class of water soluble pillar[5]arenes bearing phosphonium moieties (1, 2) and their respective ammonium analogues (3, 4) inhibit biofilm formation with IC50 values in the range of 0.67-1.66 μM. These compounds have no antimicrobial activity, do not damage red blood cell membranes, and do not affect mammalian cell viability in culture. Comparison of the antibiofilm activities of the phosphonium-decorated pillar[5]arene derivatives 1 and 2 with their respective ammonium counterparts 3 and 4 and their monomers 5 and 6, demonstrate that while positive charges, charge cooperativity and the pillararene platform are essential for the observed antibiofilm activity the nature of the charges is not. PMID:27503150

  18. Meta-Selective CAr-H Nitration of Arenes through a Ru3(CO)12-Catalyzed Ortho-Metalation Strategy.

    PubMed

    Fan, Zhoulong; Ni, Jiabin; Zhang, Ao

    2016-07-13

    The first example of transition metal-catalyzed meta-selective CAr-H nitration of arenes is described. With the use of Ru3(CO)12 as the catalyst and Cu(NO3)2·3H2O as the nitro source, a wide spectrum of arenes bearing diversified N-heterocycles or oximido as the directing groups were nitrated with meta-selectivity exclusively. Mechanism studies have demonstrated the formation of a new 18e-octahedral ruthenium species as a key ortho-CAr-H metalated intermediate, which may be responsible for the subsequent meta-selective electrophilic aromatic substitution (SEAr). Moreover, this approach provides a fast-track strategy for atom/step economical synthesis of many useful pharmaceutical molecules. PMID:27181121

  19. Langmuir monolayers and thin films of amphifilic thiacalix[4]arenes. Properties and matrix for the immobilization of cytochrome c.

    PubMed

    Solovieva, Svetlana E; Safiullin, Roman A; Kochetkov, Evgeni N; Melnikova, Nina B; Kadirov, Marsil K; Popova, Elena V; Antipin, Igor S; Konovalov, Alexander I

    2014-12-23

    Formation and properties of Langmuir films of thiacalix[4]arene (TCA) derivatives containing N-donor groups on the lower rim (Y═O(CH2)3CN; OCH2CN; NH2; OCH2ArCN-p) in 1,3-alternate conformation on aqueous subphase and solid substrates have been studied. Only tetra-cyanopropoxy-p-tert-butylthiacalix[4]arene 1 forms a typical monomolecular layer with perpendicular orientation of the macrocycle relative to the water-air interface that is able to immobilize cytochrome c in the entire range of the surface pressure. Obtained monolayers were transferred by Langmuir-Schaefer technique onto quartz, indium-tin oxide (ITO), and silicon. It was demonstrated that protein activity is retained after immobilization on the substrate. PMID:25435075

  20. Can metal ion complexation compete with the self-assembly processes of calix[4]arene amine derivatives?

    PubMed

    O'Toole, Laura; Creaven, Bernadette S; McGinley, John

    2014-06-14

    Self-assembly can occur spontaneously through aryl-aryl π-stacking in solution for calix[4]arenes derivatised at both the upper and lower rims with pendant aromatic rings, including pyridine rings. It was hoped that metal ion complexation would help to control the level of self-assembly occurring in solution, by disrupting these interactions. Metal ion titration studies were carried out on 3 with various zinc salts, but it was found that even with 1 : 4 ligand to metal ratio, the self-assembly process still dominated. Furthermore, in an effort to prevent the self-assembly process, the lower rim was completely substituted, but metal complexation reactions with these fully substituted calix[4]arenes still showed that the self-assembly process dominated. PMID:24740409

  1. A novel supramolecular polymer gel constructed by crosslinking pillar[5]arene-based supramolecular polymers through metal-ligand interactions.

    PubMed

    Wang, Pi; Xing, Hao; Xia, Danyu; Ji, Xiaofan

    2015-12-21

    A novel heteroditopic A-B monomer was synthesized and used to construct linear supramolecular polymers utilizing pillar[5]arene-based host-guest interactions. Specifically, upon addition of Cu(2+) ions, the supramolecular polymer chains are crosslinked through metal-ligand interactions, resulting in the formation of a supramolecular polymer gel. Interestingly, this self-organized supramolecular polymer can be used as a novel fluorescent sensor for detecting Cu(2+) ions. PMID:26466511

  2. Formation of a copillar[5]arene-based supramolecular polymer in solution and in the solid state.

    PubMed

    Gao, Lingyan; Zhang, Zibin; Dong, Shengyi; Xue, Min

    2014-05-01

    A linear supramolecular polymer based on the self-assembly of an easily available copillar[5]arene monomer is efficiently prepared, which is evidenced by the NMR spectroscopy, viscosity measurement, and DOSY experiment. The single-crystal X-ray analysis reveals that the polymerization of the AB-type monomer is driven by the quadruple CH•••π interactions and one CH•••O interaction. PMID:24604696

  3. Structures of potassium calix[4]arene crown ether inclusion complexes and application in polymerization of rac-lactide.

    PubMed

    Li, Yingguo; Zhao, Hongwei; Mao, Xiaoyang; Pan, Xiaobo; Wu, Jincai

    2016-06-21

    Reaction of 1,3-dipropoxy-p-tert-butyl-calix[4]arene (L(1)H2) with KN(SiMe3)2 afforded a one-dimensional (1D) chain complex [K2L(1)]n (1). Upon reaction with 1 equivalent 18-crown-6, complex 1 can convert to complex [K2(18-crown-6)L(1)] (2) which possesses a sandwich structure. Treatment of two calix[4]arene-crown ligands of 1,3-dihydroxy-p-tert-butyl-calix[4]arene-crown-5 (L(2)H2) and 1,2-dihydroxy-p-tert-butyl-calix[4]arene-crown-5 (L(3)H2) with KN(SiMe3)2 gave the dinuclear complex [K2L(2)] (3) and the mononuclear complex [K(THF)L(3)H] (4), respectively. Complexes 1-4 were all characterized by single-crystal X-ray diffraction techniques. The variable temperature (1)H NMR spectrum indicates there is a quick rotation equilibrium of the two phenoxy groups in complex 3. In addition, complexes 1-4 have been tested for the ring-opening polymerization (ROP) of rac-lactide and the results showed that complexes 2 and 3 are highly active for the ROP of rac-lactide. The obtained polymers displayed low dispersity values (Đ) and the molecular weights are close to the calculated ones. Furthermore, complexes 2 and 3 show moderate isoselectivities of Pm = 0.67 and Pm = 0.73, respectively. PMID:27222057

  4. Rh(III)-catalyzed dehydrogenative alkylation of (hetero)arenes with allylic alcohols, allowing aldol condensation to indenes.

    PubMed

    Shi, Zhuangzhi; Boultadakis-Arapinis, Mélissa; Glorius, Frank

    2013-07-25

    Efficient Rh(III)-catalyzed C-H activation of different classes of (hetero)arenes such as 2-phenylpyridine, indoles, aryl ketones and acetanilide and their dehydrogenative cross-coupling with allylic alcohols are described. Several important skeletons such as β-aryl aldehydes and ketones, 2-acetylindenes, 3,4-dihydro-1H-quinolin-2-one and quinoline could be produced using this protocol. PMID:23765402

  5. Asymmetric hydrogenation of alpha-chloro aromatic ketones catalyzed by eta6-arene/TsDPEN-ruthenium(II) complexes.

    PubMed

    Ohkuma, Takeshi; Tsutsumi, Kunihiko; Utsumi, Noriyuki; Arai, Noriyoshi; Noyori, Ryoji; Murata, Kunihiko

    2007-01-18

    Asymmetric hydrogenation of various alpha-chloro aromatic ketones with Ru(OTf)(TsDPEN)(eta6-arene) (TsDPEN = N-(p-toluenesulfonyl)-1,2-diphenylethylenediamine) produces the chiral chlorohydrins in up to 98% ee. This reaction can be conducted even on a 206-g scale. The hydrogenation of an alpha-chloro ketone with a phenol moiety has been utilized for the synthesis of (R)-norphenylephrine without protection-deprotection operations. [reaction: see text]. PMID:17217278

  6. Tubular Structures Self-Assembled from a Bola-Amphiphilic Pillar[5]arene in Water and Applied as a Microreactor.

    PubMed

    Chen, Rener; Jiang, Huajiang; Gu, Haining; Zhou, Qizhong; Zhang, Zhen; Wu, Jiashou; Jin, Zhengneng

    2015-09-01

    Various nanomorphologies were obtained by simply changing the fabrication conditions, such as the pH of the system, different solvent, or different concentration, of bola-amphiphilic pillar[5]arene Bola-AP5. Importantly, hybrid microtubules as a microreactor were successfully prepared by directly reducing AuCl4(-) on the surface of Bola-AP5-based tubular structures in water. PMID:26275020

  7. Efficient complexation between pillar[5]arenes and neutral guests: from host-guest chemistry to functional materials.

    PubMed

    Wang, Yiliang; Ping, Guchuan; Li, Chunju

    2016-08-01

    Since their discovery in 2008, pillar[n]arenes have been a popular family of macrocyclic arene hosts due to their accessible one-step synthesis, convenient functionalization, symmetrical prism structures and perfect cavity host-guest properties. Compared with other macrocyclic hosts, the most peculiar recognition behavior of pillararenes is the strong binding affinities of pillar[5]arenes (P5As) towards neutral guests in organic media, which is unfeasible for classic crown ethers and calixarenes. The intriguing properties have found extensive applications in many fields from supramolecular chemistry to materials science. This feature article provides a detailed summary of the molecular recognition of P5As and neutral guests, where the driving forces, binding mechanisms, and binding selectivities are comprehensively discussed. Furthermore, brief highlights of research progress in the functional applications based on the neutral guest⊂P5A motifs were also discussed, including the construction of complex topological superstructures (e.g. rotaxanes, catenanes and daisy chains), supramolecular polymers, and functional materials. PMID:27351168

  8. Arene activation by a nonheme iron(III)-hydroperoxo complex: pathways leading to phenol and ketone products.

    PubMed

    Faponle, Abayomi S; Banse, Frédéric; de Visser, Sam P

    2016-07-01

    Iron(III)-hydroperoxo complexes are found in various nonheme iron enzymes as catalytic cycle intermediates; however, little is known on their catalytic properties. The recent work of Banse and co-workers on a biomimetic nonheme iron(III)-hydroperoxo complex provided evidence of its involvement in reactivity with arenes. This contrasts the behavior of heme iron(III)-hydroperoxo complexes that are known to be sluggish oxidants. To gain insight into the reaction mechanism of the biomimetic iron(III)-hydroperoxo complex with arenes, we performed a computational (density functional theory) study. The calculations show that iron(III)-hydroperoxo reacts with substrates via low free energies of activation that should be accessible at room temperature. Moreover, a dominant ketone reaction product is observed as primary products rather than the thermodynamically more stable phenols. These product distributions are analyzed and the calculations show that charge interaction between the iron(III)-hydroxo group and the substrate in the intermediate state pushes the transferring proton to the meta-carbon atom of the substrate and guides the selectivity of ketone formation. These studies show that the relative ratio of ketone versus phenol as primary products can be affected by external interactions of the oxidant with the substrate. Moreover, iron(III)-hydroperoxo complexes are shown to selectively give ketone products, whereas iron(IV)-oxo complexes will react with arenes to form phenols instead. PMID:27099221

  9. Preparation, characterization and application of p-tert-butyl-calix[4]arene-SBA-15 mesoporous silica molecular sieves.

    PubMed

    Huang, Huayu; Zhao, Chuande; Ji, Yongsheng; Nie, Rong; Zhou, Pan; Zhang, Haixia

    2010-06-15

    p-tert-Butyl-calix[4]arene-SBA-15 mesoporous silica molecular sieves have been prepared and characterized by Fourier transform infrared (FT-IR) spectroscopy, powder X-ray diffraction (XRD) and nitrogen adsorption-desorption measurements. FT-IR spectra showed the presence of methylene (-CH(2)-), methyl (-CH(3)) and phenyl bands on the modified SBA-15. Powder XRD data indicated the structure of p-tert-butyl-calix[4]arene-SBA-15 remained the host SBA-15 structure. Brunauer-Emmett-Teller (BET) surface area analysis revealed a decrease in surface area and pore size. The adsorption capacity of the materials to diethylstilbestrol and bisphenol A was studied via the dynamic adsorption experiments. The maximum dynamic adsorption capacity on modified materials was 34.8 and 2.9 times higher than SBA-15 particles for diethylstilbestrol and bisphenol A, respectively. The results indicated that p-tert-butyl-calix[4]arene-SBA-15 particles could be used to the enrich the various compounds in water samples before the further analysis. PMID:20185235

  10. Acid-Promoted Reaction of Trifluoromethylated Allyl Alcohols with Arenes. Stereoselective Synthesis of CF3-Alkenes and CF3-Indanes.

    PubMed

    Kazakova, Anna N; Iakovenko, Roman O; Boyarskaya, Irina A; Nenajdenko, Valentine G; Vasilyev, Aleksander V

    2015-10-01

    Reaction of 4-aryl-1,1,1-trifluorobut-3-en-2-ols [CF3-allyl alcohols, ArCH═CHCH(OH)CF3] with arenes under activation with anhydrous FeCl3 or FSO3H was studied. We found that the transformation led to trifluoromethylated alkenes [Ar(Ar')CHCH═CHCF3] or 1-trifluoromethylated indanes (CF3-indanes). The formation of these two types of reaction products strongly depends on the nucleophilicity of the starting arene and the electrophilicity of cationic intermediates generated from CF3-allyl alcohols under reaction conditions. Benzene, anisole, veratrole, and ortho-xylene lead exclusively to CF3-alkenes with an E-configuration. More π-donating polymethylated arenes (pseudocumene, mesitylene) afford only CF3-indanes with a predominantly cis-orientation of substituents at positions 1 and 3 of the indane ring. Meta- and para-xylenes show an intermediate behavior; they may form both CF3-alkenes and/or CF3-indanes. The mechanisms of the investigated transformations are discussed. PMID:26334780

  11. Light-Induced C-H Arylation of (Hetero)arenes by In Situ Generated Diazo Anhydrides.

    PubMed

    Cantillo, David; Mateos, Carlos; Rincon, Juan A; de Frutos, Oscar; Kappe, C Oliver

    2015-09-01

    Diazo anhydrides (Ar-N=N-O-N=N-Ar) have been known since 1896 but have rarely been used in synthesis. This communication describes the development of a photochemical catalyst-free C-H arylation methodology for the preparation of bi(hetero)aryls by the one-pot reaction of anilines with tert-butyl nitrite and (hetero)arenes under neutral conditions. The key step in this procedure is the in situ formation and subsequent photochemical (>300 nm) homolytic cleavage of a transient diazo anhydride intermediate. The generated aryl radical then efficiently reacts with a (hetero)arene to form the desired bi(hetero)aryls producing only nitrogen, water, and tert-butanol as byproducts. The scope of the reaction for several substituted anilines and (hetero)arenes was investigated. A continuous-flow protocol increasing selectivity and safety has been developed enabling the experimentally straightforward preparation of a variety of substituted bi(hetero)aryls within 45 min of reaction time. PMID:26239967

  12. Calix[6]arene bypasses human pancreatic cancer aggressiveness: downregulation of receptor tyrosine kinases and induction of cell death by reticulum stress and autophagy.

    PubMed

    Pelizzaro-Rocha, Karin Juliane; de Jesus, Marcelo Bispo; Ruela-de-Sousa, Roberta Regina; Nakamura, Celso Vataru; Reis, Fabiano Souza; de Fátima, Angelo; Ferreira-Halder, Carmen Veríssima

    2013-12-01

    Pancreatic cancer ranks fourth among cancer-related causes of death in North America. Minimal progress has been made in the diagnosis and treatment of patients with late-stage tumors. Moreover, pancreatic cancer aggressiveness is closely related to high levels of pro-survival mediators, which can ultimately lead to rapid disease progression, resistance and metastasis. The main goal of this study was to define the mechanisms by which calix[6]arene, but not other calixarenes, efficiently decreases the aggressiveness of a drug resistant human pancreas carcinoma cell line (Panc-1). Calix[6]arene was more potent in reducing Panc-1 cell viability than gemcitabine and 5-fluorouracil. In relation to the underlying mechanisms of cytotoxic effects, it led to cell cycle arrest in the G0/G1 phase through downregulation of PIM1, CDK2, CDK4 and retinoblastoma proteins. Importantly, calix[6]arene abolished signal transduction of Mer and AXL tyrosine kinase receptors, both of which are usually overexpressed in pancreatic cancer. Accordingly, inhibition of PI3K and mTOR was also observed, and these proteins are positively modulated by Mer and AXL. Despite decreasing the phosphorylation of AKT at Thr308, calix[6]arene caused an increase in phosphorylation at Ser473. These findings in conjunction with increased BiP and IRE1-α provide a molecular basis explaining the capacity of calix[6]arene to trigger endoplasmic reticulum stress and autophagic cell death. Our findings highlight calix[6]arene as a potential candidate for overcoming pancreatic cancer aggressiveness. Importantly, we provide evidence that calix[6]arene affects a broad array of key targets that are usually dysfunctional in pancreatic cancer, a highly desirable characteristic for chemotherapeutics. PMID:23872419

  13. Synthesis, characterization and biological evaluation of novel Ru(II)-arene complexes containing intercalating ligands.

    PubMed

    Nikolić, Stefan; Rangasamy, Loganathan; Gligorijević, Nevenka; Aranđelović, Sandra; Radulović, Siniša; Gasser, Gilles; Grgurić-Šipka, Sanja

    2016-07-01

    Three new ruthenium(II)-arene complexes, namely [(η(6)-p-cymene)Ru(Me2dppz)Cl]PF6 (1), [(η(6)-benzene)Ru(Me2dppz)Cl]PF6 (2) and [(η(6)-p-cymene)Ru(aip)Cl]PF6 (3) (Me2dppz=11,12-dimethyldipyrido[3,2-a:2',3'-c]phenazine; aip=2-(9-anthryl)-1H-imidazo[4,5-f] [1,10] phenanthroline) have been synthesized and characterized using different spectroscopic techniques including elemental analysis. The complexes were found to be well soluble and stable in DMSO. The biological activity of the three complexes was tested in three different human cancer cell lines (A549, MDA-MB-231 and HeLa) and in one human non-cancerous cell line (MRC-5). Complexes 1 and 3, carrying η(6)-p-cymene as the arene ligand, were shown to be toxic in all cell lines in the low micromolar/subnanomolar range, with complex 1 being the most cytotoxic complex of the series. Flow cytometry analysis revealed that complex 1 caused concentration- and time-dependent arrest of the cell cycle in G2-M and S phases in HeLa cells. This event is followed by the accumulation of the sub-G1 DNA content after 48h, in levels higher than cisplatin and in the absence of phosphatidylserine externalization. Fluorescent microscopy and acridine orange/ethidium bromide staining revealed that complex 1 induced both apoptotic and necrotic cell morphology characteristics. Drug-accumulation and DNA-binding studies performed by inductively coupled plasma mass spectrometry in HeLa cells showed that the total ruthenium uptake increased in a time- and concentration-dependent manner, and that complex 1 accumulated more efficiently than cisplatin at equimolar concentrations. The introduction of a Me2dppz ligand into the ruthenium(II)-p-cymene scaffold was found to allow the discovery of a strongly cytotoxic complex with significantly higher cellular uptake and DNA-binding properties than cisplatin. PMID:26818702

  14. Triflate-functionalized calix[6]arenes as versatile building-blocks: application to the synthesis of an inherently chiral Zn(ii) complex.

    PubMed

    Zahim, Sara; Lavendomme, Roy; Reinaud, Olivia; Luhmer, Michel; Evano, Gwilherm; Jabin, Ivan

    2016-02-14

    Cavity-based metal complexes can find many applications notably in the fields of catalysis and biomimicry. In this context, it was shown that metal complexes of calix[6]arenes bearing three aza-coordinating arms at the small rim provide excellent structural models of the poly-imidazole sites found in the active site of many metallo-enzymes. All these N-donor ligands were synthesized from the 1,3,5-tris-methoxy-p-tBu-calix[6]arene platform, which presents some limitations in terms of functionalization. Therefore, there is a need for the development of new calix[6]arene-based building-blocks selectively protected at the small rim. Herein we describe the regioselective one step synthesis of two calix[6]arenes decorated with triflate groups, i.e. X6H4Tf2 and X6H3Tf3, from the parent calix[6]arene X6H6. It is shown that the triflate groups can either act as protecting or deactivating groups, allowing the elaboration of sophisticated calixarene-based systems selectively functionalized at the large and/or at the small rim. In addition, X6H3Tf3 is functionalized on the A, B, and D rings and thus gives access to inherently chiral compounds, as demonstrated by the synthesis of a rare example of inherently chiral cavity-based metal complex. PMID:26751614

  15. Synthesis, Physicochemical Studies, Molecular Dynamics Simulations, and Metal-Ion-Dependent Antiproliferative and Antiangiogenic Properties of Cone ICL670-Substituted Calix[4]arenes

    PubMed Central

    Rouge, Pascal; Dassonville-Klimpt, Alexandra; Cézard, Christine; Boudesocque, Stéphanie; Ourouda, Roger; Amant, Carole; Gaboriau, François; Forfar, Isabelle; Guillon, Jean; Guillon, Emmanuel; Vanquelef, Enguerran; Cieplak, Piotr; Dupradeau, François-Yves; Dupont, Laurent

    2014-01-01

    Iron chelators, through their capacity to modulate the iron concentration in cells, are promising molecules for cancer chemotherapy. Chelators with high lipophilicity easily enter into cells and deplete the iron intracellular pool. Consequently, iron-dependent enzymes, such as ribonucleotide reductase, which is over-expressed in cancer cells, become nonfunctional. A series of calix[4]arene derivatives substituted at the lower rim by ICL670, a strong FeIII chelator, have been synthesized. Physicochemical properties and antiproliferative, angiogenesis, and tumorigenesis effects of two calix[4]arenes mono- (5a) or disubstituted (5b) with ICL670 have been studied. These compounds form metal complexes in a ratio of one to two ligands per FeIII atom as shown by combined analyses of the protometric titration curves and ESIMS spectra. The grafting of an ICL670 group on a calix[4]arene core does not significantly alter the acid–base properties, but improves the iron-chelating and lipophilicity properties. The best antiproliferative and anti-angiogenic results were obtained with calix[4]arene ligand 5a, which possesses the highest corresponding properties. Analyses of molecular dynamics simulations performed on the two calix[4]arenes provide three-dimensional structures of the complexes and proved 5a to be the most stable upon complexation. PMID:25599014

  16. Quantifying recent pyroclastic and lava flows at Arenal Volcano, Costa Rica, using medium-footprint lidar

    NASA Astrophysics Data System (ADS)

    Hofton, M. A.; Malavassi, E.; Blair, J. B.

    2006-11-01

    Arenal volcano is a small, active stratovolcano in Costa Rica. In 1998 and 2005, NASA's Laser Vegetation Imaging Sensor (LVIS) was used to collect wide-swath 3-dimensional topographic images of the volcano. The LVIS is a full-waveform, scanning, medium-sized footprint, airborne laser altimeter system. By digitally recording the shape of the returning laser pulse (waveform), the LVIS provides a precise and accurate view of both the sub-canopy and canopy-top topographies as well as the vertical and horizontal structure of vegetation at 15-25 m horizontal resolution. By comparing georeferenced waveform data collected in 1998 and 2005, we mapped lava and pyroclastic flows deposited during this period. The active crater grew by 3.82 m yr-1. A flow volume estimate of 2.19 × 107 m3 (Dense Rock Equivalent of 1.89 × 107 m3 or 0.085 m3s-1) was obtained for the period 1998 to 2005. Precise elevation and elevation change data such as those provided by the LVIS are essential to calculate eruption volume and to study magma-supply dynamics, as well as assess the danger posed by the volcano to the local population from hazards such as pyroclastic flows.

  17. New π-arene ruthenium(II) piano-stool complexes with nitrogen ligands.

    PubMed

    Grau, Jordi; Noe, Verónica; Ciudad, Carles; Prieto, Maria J; Font-Bardia, Mercè; Calvet, Teresa; Moreno, Virtudes

    2012-04-01

    The synthesis, characterization, DNA interaction and antiproliferative behavior of new π-arene ruthenium(II) piano-stool complexes with nitrogen ligands are described. Three series of organometallic compounds of formulae [RuCl(2)(η(6)-p-cym)L] were synthesized (with L=2-, 3- or 4-methylpyridine; L=2,3-, 2,4-, 2,5-, 3,4-, 3,5-dimethylpyridine and L=1,2-, 1,3- 1,4-methylaminobenzene). The crystal structures of [RuCl(2)(p-cym)(4-methylpyridine)], [RuCl(2)(p-cym)(3,4-dimethylpyridine)] and [RuCl(2)(p-cym)(1,4-methylaminobenzene)] were resolved and the characterization was completed by spectroscopic UV-vis, FT-IR and (1)H NMR studies. Electrochemical experiments were performed by cyclic voltammetry to estimate the redox potential of the Ru(II)/Ru(III) couple. The interaction with plasmid pBR322 DNA was studied through the examination of the electrophoretical mobility and atomic force microscopy, and interaction with ct-DNA by circular dichroism, viscosity measurements and fluorescence studies based on the DNA-ethidium bromide complex. The antiproliferative behavior of the series with L=methylpyridine was assayed against two tumor cell lines, i.e. LoVo and MiaPaca. The results revealed a moderate cytotoxicity with a higher activity for the LoVo cell line compared to the MiaPaca one. PMID:22387934

  18. Structural Determinants of p53-Independence in Anticancer Ruthenium-Arene Schiff-Base Complexes.

    PubMed

    Chow, Mun Juinn; Babak, Maria V; Wong, Daniel Yuan Qiang; Pastorin, Giorgia; Gaiddon, Christian; Ang, Wee Han

    2016-07-01

    p53 is a key tumor suppressor gene involved in key cellular processes and implicated in cancer therapy. However, it is inactivated in more than 50% of all cancers due to mutation or overexpression of its negative regulators. This leads to drug resistance and poor chemotherapeutic outcome as most clinical drugs act via a p53-dependent mechanism of action. An attractive strategy to circumvent this resistance would be to identify new anticancer drugs that act via p53-independent mode of action. In the present study, we identified 9 Ru (II)-Arene Schiff-base (RAS) complexes able to induce p53-independent cytotoxicity and discuss structural features that are required for their p53-independent activity. Increasing hydrophobicity led to an increase in cellular accumulation in cells with a corresponding increase in efficacy. We further showed that all nine complexes demonstrated p53-independent activity. This was despite significant differences in their physicochemical properties, suggesting that the iminoquinoline ligand, a common structural feature for all the complexes, is required for the p53-independent activity. PMID:27174050

  19. Mirror-Image Organometallic Osmium Arene Iminopyridine Halido Complexes Exhibit Similar Potent Anticancer Activity

    PubMed Central

    Fu, Ying; Soni, Rina; Romero, María J; Pizarro, Ana M; Salassa, Luca; Clarkson, Guy J; Hearn, Jessica M; Habtemariam, Abraha; Wills, Martin; Sadler, Peter J

    2013-01-01

    Four chiral OsII arene anticancer complexes have been isolated by fractional crystallization. The two iodido complexes, (SOs,SC)-[Os(η6-p-cym)(ImpyMe)I]PF6 (complex 2, (S)-ImpyMe: N-(2-pyridylmethylene)-(S)-1-phenylethylamine) and (ROs,RC)-[Os(η6-p-cym)(ImpyMe)I]PF6 (complex 4, (R)-ImpyMe: N-(2-pyridylmethylene)-(R)-1-phenylethylamine), showed higher anticancer activity (lower IC50 values) towards A2780 human ovarian cancer cells than cisplatin and were more active than the two chlorido derivatives, (SOs,SC)-[Os(η6-p-cym)(ImpyMe)Cl]PF6, 1, and (ROs,RC)-[Os(η6-p-cym)(ImpyMe)Cl]PF6, 3. The two iodido complexes were evaluated in the National Cancer Institute 60-cell-line screen, by using the COMPARE algorithm. This showed that the two potent iodido complexes, 2 (NSC: D-758116/1) and 4 (NSC: D-758118/1), share surprisingly similar cancer cell selectivity patterns with the anti-microtubule drug, vinblastine sulfate. However, no direct effect on tubulin polymerization was found for 2 and 4, an observation that appears to indicate a novel mechanism of action. In addition, complexes 2 and 4 demonstrated potential as transfer-hydrogenation catalysts for imine reduction. PMID:24114923

  20. Biocompatible polyurethane/thiacalix[4]arenes functionalized Fe3O4 magnetic nanocomposites: Synthesis and properties.

    PubMed

    Mohammadi, Abbas; Barikani, Mehdi; Lakouraj, Moslem Mansour

    2016-09-01

    In this study, a series of magnetic polyurethane/Fe3O4 elastomer nanocomposites were prepared by covalently embedding novel thiacalix[4]arenes (TC4As) functionalized Fe3O4 nanoparticles (TC4As-Fe3O4) which contain macrocycles with reactive hydroxyl groups. Surface functionalization of Fe3O4 nanoparticles with TC4As macrocycles as unique reactive surface modifier not only gives specific characteristics to Fe3O4 nanoparticles but also improves the interphase interaction between nanoparticles and the polyurethane matrices through covalent attachment of polymer chains to nanoparticle surfaces. The novel synthesized TC4As-Fe3O4 nanoparticles were characterized by FTIR, XRD, TGA, VSM and SEM analysis. Furthermore, the effect of functionalization of Fe3O4 nanoparticles on the various properties of resulting nanocomposites was studied by XRD, TGA, DMTA, SEM, and a universal tensile tester. It was found that the functionalization of nanoparticles with TC4As affords better mechanical and thermal properties to polyurethane nanocomposites in comparison with unmodified nanoparticles. The SEM analysis showed finer dispersion of TC4As-Fe3O4 nanoparticles than unmodified Fe3O4 nanoparticles within the polyurethane matrices, which arising from formation of covalent bonding between TC4As functionalized Fe3O4 nanoparticles and polyurethane matrices. Moreover, the investigation of in vitro biocompatibility of novel nanocomposites showed that these samples are excellent candidate for biomedical use. PMID:27207044

  1. Photorelease of Pyridyl Esters in Organometallic Ru(II) Arene Complexes.

    PubMed

    Habtemariam, Abraha; Garino, Claudio; Ruggiero, Emmanuel; Alonso-de Castro, Silvia; Mareque-Rivas, Juan C; Salassa, Luca

    2015-01-01

    New Ru(II) arene complexes of formula [(η6-p-cym)Ru(N-N)(X)]2+ (where p-cym = para-cymene, N-N = 2,2'-bipyrimidine (bpm) or 2,2'-bipyridine (bpy) and X = m/p-COOMe-Py, 1-4) were synthesised and characterized, including the molecular structure of complexes [(η6-p-cym)Ru(bpy)(m-COOMe-Py)]2+ (3) and [(η6-p-cym)Ru(bpy) (p-COOMe-Py)]2+ (4) by single-crystal X-ray diffraction. Complexes 1-4 are stable in the dark in aqueous solution over 48 h and photolysis studies indicate that they can photodissociate the monodentate m/p-COOMe-Py ligands selectively with yields lower than 1%. DFT and TD-DFT calculations (B3LYP/LanL2DZ/6-31G**) performed on singlet and triplet states pinpoint a low-energy triplet state as the reactive state responsible for the selective dissociation of the monodentate pyridyl ligands. PMID:25905605

  2. Synthesis of novel anticancer ruthenium-arene pyridinylmethylene scaffolds via three-component reaction.

    PubMed

    Jadhav, Gajanan Raosaheb; Sinha, Sohini; Chhabra, Mohit; Paira, Priyankar

    2016-06-01

    A novel three components approach for the synthesis of bioactive Ru-arene pyridinylmethylene complexes has been developed using pyridine carboxaldehyde, amino pyridine and dichloro (p-cymene) ruthenium(II) dimer as starting materials. These scaffolds were screened for their anticancer activity against breast cancer (MCF7) and human Epitheloid Cervix Carcinoma (HeLa) cell line. It was established that compounds [(η(6)-pcymene)RuCl(κ(2)-N,N-(3,5-dinitro-pyridin-2-yl)-pyridin-2-ylmethylene-amine)]PF6 (4o), [(η(6)-pcymene)RuCl(κ(2)-N,N-N-(3,5-dibromo-pyridin-2-yl)-pyridin-2-ylmethylene-amine)]PF6 (4c), [(η(6)-pcymene)RuCl(κ(2)-N,N-(3,5-dibromo-6-methylpyridin-2-yl)-pyridin-2-ylmethylene-amine)]PF6 (4j) and [(η(6)-pcymene)RuCl(κ(2)-N,N-3(3-bromo-5-methyl-pyridin-2-yl)-pyridin-2-ylmethylene-amine)]PF6 (4b) were significantly active against both the cell lines. PMID:27090558

  3. Supramolecular gels with high strength by tuning of calix[4]arene-derived networks

    PubMed Central

    Lee, Ji Ha; Park, Jaehyeon; Park, Jin-Woo; Ahn, Hyo-Jun; Jaworski, Justyn; Jung, Jong Hwa

    2015-01-01

    Supramolecular gels comprised of low-molecular-weight gelators are generally regarded as mechanically weak and unable to support formation of free-standing structures, hence, their practical use with applied loads has been limited. Here, we reveal a technique for in situ generation of high tensile strength supramolecular hydrogels derived from low-molecular-weight gelators. By controlling the concentration of hydrochloric acid during hydrazone formation between calix-[4]arene-based gelator precursors, we tune the mechanical and ductile properties of the resulting gel. Organogels formed without hydrochloric acid exhibit impressive tensile strengths, higher than 40 MPa, which is the strongest among self-assembled gels. Hydrogels, prepared by solvent exchange of organogels in water, show 7,000- to 10,000-fold enhanced mechanical properties because of further hydrazone formation. This method of molding also allows the gels to retain shape after processing, and furthermore, we find organogels when prepared as gel electrolytes for lithium battery applications to have good ionic conductivity. PMID:25799459

  4. Calix[4]arene based dipodal receptor nanohybrids for selective determination of chloride ions in aqueous media.

    PubMed

    Kaur, Harpreet; Singh, Jasminder; Chopra, Shweta; Kaur, Navneet

    2016-01-01

    A chemical sensor based on p-tert butyl calix[4]arene has been synthesized and characterized using an assortment of spectroscopic techniques such as (1)H NMR, (13)C NMR, and elemental analysis. For sensor application, organic nanoparticles (N1) of 1 have been primed by implementing re-precipitation technique, which were further employed for preparing organic-inorganic hybrid (H1) by decorating N1 with gold nanoparticles. Both N1 and H1 were characterized using UV-visible, fluorescence, and DLS studies. Photo-physical changes due to anion binding with H1 were scrutinized using UV-visible absorption spectrometer and found it to promptly and selectively recognize Cl(-) ions in aqueous media. Thus, H1 can be effectively used for recognition of Cl(-) ions in aqueous media over a wide pH range, in samples of real time importance with a detection limit of 2.84×10(-9) M with a linear detection range up to 50 μM. PMID:26695243

  5. Immobilized ferrocenium in tetraurea calix[4]arene heterodimers: Self assembly on gold, electrochemical responses, and detection of redox states by a tip: Towards molecular information storage

    NASA Astrophysics Data System (ADS)

    Xu, Songbo

    Calix[4]arene derivatives attached with sulfur functions were allowed to bind on metal surfaces. While they exist as single molecules in polar solvents, calix[4]arenes of this type form dimeric capsules in aprotic, apolar solvents. A solvent molecule is usually included in such a capsule, if no guest with a higher affinity is present. In the presence of an equimolar amount of a tetratosylurea functionalized calix[4]arene, the heterodimers were formed, inclusive guest molecules. Self-assembled monolayers (SAMs) were formed using the single calix[4]arenes with sulfur attachments and the heterodimeric capsules. Chloroform, dichloromethane and ferrocenium cations were used as guests in these immobilized heterodimeric capsules. The particular supramolecular architecture of the heterodimers should ensure after immobilization that decomposition of the capsules and release of the guest is impossible or at least hindered. The self-assembly process, and the inclusion of the various guests, such as dichloromethane or ferrocenium, were investigated with a variety of methods, including classical surface plasmon spectroscopy, gold nanoparticle absorption spectroscopy and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The stability of the ferrocenium filled SAMs in electrolyte solutions and the film quality was tested by cyclic voltammetry. The electrochemical response of the ferrocenium encapsulated in the heterodimer capsules both in SAMs on a gold disk electrode and in solution was investigated with cyclic voltammetry. The stability of the electrochemically active monolayers was tested by a heat treatment and multiple cycling. Reversible redox reactions for immobilized encapsulated ferrocenium on gold surfaces was demonstrated. The redox states of immobilized encapsulated ferrocenium (filled in calix[4]arene heterodimers) on gold surface were recognized by a tip of a scanning electrochemical microscopy (SECM). The SECM tip can be also used to monitor or change the

  6. Cross-linked supramolecular polymer gels constructed from discrete multi-pillar[5]arene metallacycles and their multiple stimuli-responsive behavior.

    PubMed

    Li, Zhong-Yu; Zhang, Yanyan; Zhang, Chang-Wei; Chen, Li-Jun; Wang, Chao; Tan, Hongwei; Yu, Yihua; Li, Xiaopeng; Yang, Hai-Bo

    2014-06-18

    A new family of discrete hexakis-pillar[5]arene metallacycles with different sizes have been successfully prepared via coordination-driven self-assembly, which presented very few successful examples of preparation of discrete multiple pillar[n]arene derivatives. These newly designed hexakis-pillar[5]arene metallacycles were well characterized with one-dimensional (1-D) multinuclear NMR ((1)H and (31) P NMR), two-dimensional (2-D) (1)H-(1)H COSY and NOESY, ESI-TOF-MS, elemental analysis, and PM6 semiempirical molecular orbital methods. Furthermore, the host-guest complexation of such hexakis-pillar[5]arene hosts with a series of different neutral ditopic guests G1-6 were well investigated. Through host-guest interactions of hexakis-pillar[5]arene metallacycles H2 or H3 with the neutral dinitrile guest G5, the cross-linked supramolecular polymers H2⊃(G5)3 or H3⊃(G5)3 were successfully constructed at the high-concentration region, respectively. Interestingly, these cross-linked supramolecular polymers transformed into the stable supramolecular gels upon increasing the concentrations to a relatively high level. More importantly, by taking advantage of the dynamic nature of metal-ligand bonds and host-guest interactions, the reversible multiple stimuli-responsive gel-sol phase transitions of such polymer gels were successfully realized under different stimuli, such as temperature, halide, and competitive guest, etc. The mechanism of such multiple stimuli-responsive processes was well illustrated by in situ multinuclear NMR investigation. This research not only provides a highly efficient approach to the preparation of discrete multiple pillar[n]arene derivatives but also presents a new family of multiple stimuli-responsive "smart" soft matters. PMID:24571308

  7. A new ion selective electrode for cesium (I) based on calix[4]arene-crown-6 compounds.

    PubMed

    Ramanjaneyulu, P S; Kumar, Abha Naveen; Sayi, Y S; Ramakumar, K L; Nayak, S K; Chattopadhyay, S

    2012-02-29

    A polyvinylchloride (PVC) based liquid membrane ion selective electrode (ISE) for cesium has been developed. 25,27-Dihydroxycalix[4]arene-crown-6 (L1), 5,11,17,23-tetra-tert-butyl-25,27-dimethoxycalix[4]arene-crown-6 (L2) and 25,27-bis(1-octyloxy)calix[4]arene-crown-6 (L3) were investigated for their use as ionophores. The cation exchange resin DOWEX-50W was used to maintain low activity Cs+ in inner filling solution to improve the performance. The best response for cesium was observed with L3 along with optimized membrane constituents and composition. Excellent Nernstian response (56.6 mV/decade of Cs(I)) over the concentration range 10(-7) to 10(-2)M of Cs(I) was obtained with a fast response time of less than 10s. Detection limit for Cs(I) using the present ISE is 8.48×10(-8) M Cs(I). Separate solution method (SSM) was applied to ascertain the selectivity for Cs(I) over alkali, alkaline earth and transition metal ions. The response of ISE for Cs(I) was fairly constant over the pH range of 4-11. The lifetime of the electrode is 10 months which is the highest life for any membrane based Cs-ISE so far developed. The concentration of cesium ion in two simulated high level active waste streams was determined and results agreed well with those obtained independently employing AAS. PMID:22260754

  8. p-Sulfonic Acid Calix[4]arene as an Efficient Catalyst for One-Pot Synthesis of Pharmaceutically Significant Coumarin Derivatives under Solvent-Free Condition

    PubMed Central

    Tashakkorian, Hamed; Lakouraj, Moslem Mansour; Rouhi, Mona

    2015-01-01

    One-pot and efficient protocol for preparation of some potent pharmaceutically valuable coumarin derivatives under solvent-free condition via direct coupling using biologically nontoxic organocatalyst, calix[4]arene tetrasulfonic acid (CSA), was introduced. Calix[4]arene sulfonic acid has been incorporated lately as a magnificent and recyclable organocatalyst for the synthesis of some organic compounds. Nontoxicity, solvent-free conditions, good-to-excellent yields for pharmaceutically significant structures, and especially ease of catalyst recovery make this procedure valuable and environmentally benign. PMID:26798517

  9. A Rare and Exclusive Endoperoxide Photoproduct Derived from a Thiacalix[4]arene Crown-Shaped Derivative Bearing a 9,10-Substituted Anthracene Moiety.

    PubMed

    Zhao, Jiang-Lin; Wu, Chong; Tomiyasu, Hirotsugu; Zeng, Xi; Elsegood, Mark R J; Redshaw, Carl; Yamato, Takehiko

    2016-05-20

    A rare and exclusive endoperoxide photoproduct was quantitatively obtained from a thiacalix[4]arene crown-shaped derivative upon irradiation at λ=365 nm; the structure was unambiguously confirmed by (1) H/(13) C NMR spectroscopy and X-ray crystallography. The prerequisites for the formation of the endoperoxide photoproduct have also been discussed. Furthermore, the photochemical reaction rate could be greatly enhanced in the presence of the thiacalix[4]arene platform because it served as a host to capture oxygen. PMID:26994971

  10. Pd-Catalyzed C-H Alkylation of Arenes Using PyrDipSi, a Transformable and Removable Silicon-Tethered Directing Group.

    PubMed

    Sarkar, Dhruba; Gevorgyan, Vladimir

    2016-08-01

    An efficient Pd-catalyzed ortho-C-H alkylation reaction of arenes using a transformable and removable Si-tethered pyridyldiisopropylsilyl (PyrDipSi) directing group has been developed. In addition, the PyrDipSi directing group allows for an efficient sequential double-fold C-H alkylation/oxygenation of arenes to produce meta-alkylated phenols. This directing group can easily be removed or converted into valuable functionalities, such as aryl, iodo, boronic ester, or phenol. PMID:27272930

  11. DFT/TDDFT investigation on the chemical reactivities, aromatic properties, and UV-Vis absorption spectra of 1-butoxy-4-methoxybenzenepillar[5]arene constitutional isomers.

    PubMed

    Zhang, Jian; Ren, Shuqing

    2016-09-01

    We investigate the chemical reactivities, aromatic properties, and UV-Vis absorption spectra of four constitutional isomers of 1-butoxy-4-methoxybenzenepillar[5]arene with the DFT and TDDFT methods. These characteristics in the gas and solvent phases are discussed on the basis of electronic energy, the highest occupied molecular orbital energy, electrophilicity, global hardness, chemical potential, and nucleus-independent chemical shift. The out-of-plane component of the NICS values reveals that there is a great contrast between aromatic rings of the isomer and benzene. The most intense wavelengths of BMpillar[5]arenes are all made up of delocalized-delocalized π → π* transition. PMID:27535850

  12. 2,14-Dithiacalix[4]arene and its homooxa analogues: synthesis and dynamic NMR study of conformational behaviour.

    PubMed

    Hucko, Michal; Dvoráková, Hana; Eigner, Václav; Lhoták, Pavel

    2015-04-25

    A simple and scalable synthesis of 2,14-dithiacalix[4]arene with alternating bridges (-CH2- and -S-) is reported. Proper selection of the bisphenol-based starting building blocks can provide not only the title compound (58%) but also yet unreported homooxa analogues possessing three different bridging units (-CH2-, -S- and -CH2-O-CH2-) in the molecule. These systems exhibit interesting conformational behaviour allowing for the study of flip-flop motion of the circular hydrogen bond arrays using dynamic NMR techniques. PMID:25807186

  13. Supramolecular Alternating Polymer from Crown Ether and Pillar[5]arene-Based Double Molecular Recognition for Preparation of Hierarchical Materials.

    PubMed

    Li, Hui; Fan, Xiaodong; Qi, Miao; Yang, Zhen; Zhang, Haitao; Tian, Wei

    2016-01-01

    A novel supramolecular alternating polymer is constructed based on double molecular recognition events of benzo-21-crown-7 with a secondary ammonium salt and of pillar[5]arene with a neutral guest. The resulting polymer is utilized to prepare hierarchical materials with different dimensionalities for the first time. These materials included zero-dimensional spherical aggregates, one-dimensional nanofibers, two-dimensional microstructured films, and three-dimensional ordered glue. This development will be helpful for designing and preparing supramolecular hierarchical materials with different dimensionalities. PMID:26555439

  14. Bis-Calix[4]arenes: From Ligand Design to the Directed Assembly of a Metal-Organic Trigonal Antiprism.

    PubMed

    Coletta, Marco; McLellan, Ross; Murphy, Paul; Leube, Bernhard T; Sanz, Sergio; Clowes, Rob; Gagnon, Kevin J; Teat, Simon J; Cooper, Andrew I; Paterson, Martin J; Brechin, Euan K; Dalgarno, Scott J

    2016-06-20

    Calix[4]arenes (C[4]s) are versatile platforms for the construction of polymetallic clusters containing paramagnetic metal ions. Synthetic modification at the C[4] methylene bridge allows for the design of bis-C[4]s that, depending on the linker employed, can be used to either dictate which clusters can be formed or direct the assembly of a new metal-organic polyhedron (MOP). The assembly resulting from the latter approach displays thermal stability and uptake of N2 or H2 gas, confirming that this is a viable route to the synthesis of new, functional supramolecular architectures. PMID:27166930

  15. Direct Access to α,α-Difluoroacylated Arenes by Palladium-Catalyzed Carbonylation of (Hetero)Aryl Boronic Acid Derivatives.

    PubMed

    Andersen, Thomas L; Frederiksen, Mette W; Domino, Katrine; Skrydstrup, Troels

    2016-08-22

    A palladium-catalyzed carbonylative coupling of (hetero)aryl boronates or boronic acid salts with carbon monoxide and α-bromo-α,α-difluoroamides and bromo-α,α-difluoroesters is described herein. The method is useful for the synthesis of a diverse selection of (hetero)aryl α,α-difluoro-β-ketoamides and α,α-difluoro-β-ketoesters, which are useful building blocks for the generation of functionalized difluoroacylated and difluoroalkyl arenes. The method could be further extended to a one-pot protocol for the formation of difluoroacetophenones. PMID:27346239

  16. Theoretical investigation on the molecular inclusion process of prilocaine into p-sulfonic acid calix[6]arene

    NASA Astrophysics Data System (ADS)

    de Sousa, Sara M. R.; Fernandes, Sergio A.; De Almeida, Wagner B.; Guimarães, Luciana; Abranches, Paula A. S.; Varejão, Eduardo V. V.; Nascimento, Clebio S., Jr.

    2016-02-01

    The present letter reports, for the first time, results from a theoretical analysis of the inclusion process involving the prilocaine into the p-sulfonic acid calix[6]arene. Structure and stabilization energies were calculated, in both gas and aqueous phases, using a sequential methodology based on semiempirical and Density Functional Theory (DFT) calculations. From the results, a qualitative structure property relationship could be established with some main structural features being relevant for inclusion complex stabilization: (i) the hydrogen bonds established between guest and host molecules, (ii) the dispersion effect and (iii) the inclusion mode of guest molecule into the host cavity.

  17. Click-modified hexahomotrioxacalix[3]arenes as fluorometric and colorimetric dual-modal chemosensors for 2,4,6-trinitrophenol.

    PubMed

    Wu, Chong; Zhao, Jiang-Lin; Jiang, Xue-Kai; Ni, Xin-Long; Zeng, Xi; Redshaw, Carl; Yamato, Takehiko

    2016-09-14

    A new type of chemosensor-based approach to the detection of 2,4,6-trinitrophenol (TNP) is described in this paper. Two hexahomotrioxacalix[3]arene-based chemosensors 1 and 2 were synthesized through click chemistry, which exhibited high binding affinity and selectivity toward TNP as evidenced by UV-vis and fluorescence spectroscopy studies. (1)H NMR titration analysis verified that CH⋯O hydrogen bonding is demonstrated as the mode of interaction, which possibly facilitates effective charge-transfer. PMID:27566358

  18. Efficiently functionalized oxacalix[4]arenes: Synthesis, characterization and exploration of their biological profile as novel HDAC inhibitors.

    PubMed

    Mehta, Viren; Athar, Mohd; Jha, P C; Panchal, Manthan; Modi, Krunal; Jain, V K

    2016-02-01

    A series of novel substituted oxacalix[4]arene has been synthesized and explored for their biological profile by evaluating anticancer, antifungal and antibacterial properties. The derivatives have been characterized by various spectroscopic techniques such as IR, (1)H NMR, (13)C NMR and Mass spectrometry. Many compounds showed strong inhibition (MIC) in the range of ∼0-50 μM with interesting cytotoxic activities against Hela cells in particular. The compounds were theoretically evaluated by docking studies as potential histone deacetylase inhibitors (HDACi). The study indicates that compounds bound adequately with HDAC, and hence complemented the experimental findings. PMID:26725026

  19. Asymmetric Hydrogenation of Unprotected Indoles Catalyzed by η(6)-Arene/N-Me-sulfonyldiamine-Ru(II) Complexes.

    PubMed

    Touge, Taichiro; Arai, Takayoshi

    2016-09-01

    Protecting-group-free transformation is a challenging and important issue in atom-economical organic synthesis. The η(6)-arene/N-Me-sulfonyldiamine-Ru(II)-BF4 complex-catalyzed asymmetric hydrogenation of 2-substituted unprotected indoles in weakly acidic hexafluoroisopropanol gives optically active indoline compounds with up to >99% ee. Under mild reaction media, halogen atoms and synthetically important protecting groups (e.g., silyl ether, acetal, benzyl ether, and ester) on indoles are maintained, which is advantageous for the synthesis of further complex indoline molecules. PMID:27509089

  20. Rhodium-catalyzed annulation of arenes with alkynes through weak chelation-assisted C-H activation.

    PubMed

    Yang, Yudong; Li, Kaizhi; Cheng, Yangyang; Wan, Danyang; Li, Mingliang; You, Jingsong

    2016-02-18

    The purpose of this article is to give a brief review of weak chelation-assistance as a powerful means for the rhodium-catalyzed annulation of arenes with alkynes. The use of commonly occurring functional groups (e.g., ketones, aldehydes, carboxylic acids and alcohols) as the directing groups enriches the versatility of auxiliary ligands and extends the scope of products. This short article offers an overview on emerging procedures, highlights their advantages and limitations, and covers the latest progress in the rapid synthesis of organic functional materials and natural products. PMID:26757884

  1. Development of ultrafast photochromic organometallics and photoinduced linkage isomerization of arene chromium carbonyl derivatives.

    PubMed

    To, Tung T; Heilweil, Edwin J; Duke, Charles B; Ruddick, Kristie R; Webster, Charles Edwin; Burkey, Theodore J

    2009-03-26

    We review recent studies of processes relevant to photoinduced linkage isomerization of organometallic systems with the goal of preparing organometallics with an efficient and ultrafast photochromic response. The organometallic system thus corresponds to two linkage isomers with different electronic environments that are responsible for different optical properties. Much of this work has focused on examining processes following irradiation of cyclopentadienyl manganese tricarbonyl derivatives (compounds 3-21) including solvent coordination, thermal relaxation, solvent displacement by tethered functional groups (chelation), dissociation of tethered functional groups, and linkage isomerization. A new platform is investigated for obtaining a photochromic response in new experiments with arene chromium dicarbonyl complexes. A photochromic response is observed for arene chromium dicarbonyl complexes with tethered pyridine and olefin functional groups based on light-driven linkage isomerization on the nanosecond time scale. Irradiation at 532 nm of 23 ([Cr{eta(6)-C(6)H(5)CH(2-Py-kappaN)CH(2)CH=CH(2)}(CO)(2)]) (Py = pyridine) results in the isomerization to 22 ([Cr{eta(6)-C(6)H(5)CH(2-Py)CH(2)-eta(2)-CH=CH(2)}(CO)(2)]), and 355 nm irradiation isomerizes 22 to 23. The ultrafast linkage isomerization has been investigated at room temperature in n-heptane solution on the picosecond to microsecond time scale with UV- or visible-pump and IR-probe transient absorption spectroscopy by comparing the dynamics with model compounds containing only a tethered pyridine. Irradiation of 24 ([Cr{eta(6)-C(6)H(5)(CH(2))(3)(2-Py)}(CO)(3)]) and 25 ([Cr{eta(6)-C(6)H(5)(CH(2))(2)(2-Py)}(CO)(3)]) at 289 nm induces CO loss to immediately yield a Cr-heptane solvent coordinated intermediate of the unsaturated Cr fragment, which then converts to the kappaN(1)-pyridine chelate within 200 and 100 ns, respectively. Irradiation of 26 ([Cr{eta(6)-C(6)H(5)CH(2)(2-Py)}(CO)(3)]) also induces CO loss to

  2. Methoxy-ether and crown-ether derivatives of tetrahomodioxa- and octahomotetraoxacalix[4]arenes.

    PubMed

    Masci, B; Saccheo, S; Fonsi, M; Varrone, M; Finelli, M; Nierlich, M; Thuéry, P

    2001-08-01

    Three methoxy-ether and one methoxy-ether/crown-ether derivatives of p-tert-butyltetrahomodioxa- and p-R-octahomotetraoxacalix[4]arenes (R = methyl, tert-butyl, H) have been investigated. The first three compounds, 7,15,21,27-tetra-tert-butyl-29,30,31,32-tetramethoxy-3,11-dioxapentacyclo[23.3.1.1(5,9).1(13,17).1(19,23)]ditriaconta-1(29),5,7,9(30),13,15,-17(31),19,21,23(32),25,27-dodecaene, C(50)H(68)O(6), 33,34,35,36-tetramethoxy-7,15,23,31-tetramethyl-3,11,19,27-tetraoxapentacyclo[27.3.1.1(5,9).1(13,17).1(21,25)]hexatriaconta-1(33),5,7,9(34),13,15,17(35),21,23,25(36),29,31-dodecaene, C(40)H(48)O(8), and 7,23-di-tert-butyl-33,34,35,36-tetramethoxy-3,11,19,27-tetraoxapentacyclo[27.3.1.1(5,9).1(13,17).1(21,25)]hexatriaconta-1(33),5,7,9(34),13,15,17(35),- 21,23,25(36),29,31-dodecaene, C(44)H(56)O(8), in the partial-cone or 1,2-alternate conformations, present the common feature of methoxy-ether self-inclusion, while the fourth, 42,43-dimethoxy-7,15,23,31-tetramethyl-3,11,19,27,34,37,40-heptaoxahexacyclo[15.15.9.1(5,9).1(21,25).0(13,41).0(29,33)]tritetraconta-5(42),6,8,13(41),14,16,21(43),22,24,29(33),30,32-dodecaene, C(42)H(50)O(9), adopts the 1,3-alternate conformation owing to the presence of a 1,3-polyether chain. PMID:11498633

  3. Upconverting Nanoparticles Prompt Remote Near-Infrared Photoactivation of Ru(II)-Arene Complexes.

    PubMed

    Ruggiero, Emmanuel; Garino, Claudio; Mareque-Rivas, Juan C; Habtemariam, Abraha; Salassa, Luca

    2016-02-18

    The synthesis and full characterisation (including X-ray diffraction studies and DFT calculations) of two new piano-stool Ru(II) -arene complexes, namely [(η(6) -p-cym)Ru(bpy)(m-CCH-Py)][(PF)6]2 (1) and [(η(6) -p-cym)Ru(bpm)(m-CCH-Py)][(PF)6]2 (2; p-cym=p-cymene, bpy=2,2'-bipyridine, bpm=2,2'-bipyrimidine, and m-CCH-Py=3-ethynylpyridine), is described and discussed. The reaction of the m-CCH-Py ligand of 1 and 2 with diethyl-3-azidopropyl phosphonate by Cu-catalysed click chemistry affords [(η(6) -p-cym)Ru(bpy)(P-Trz-Py)][(PF)6]2 (3) and [(η(6) -p-cym)Ru(bpm)(P-Trz-Py)][(PF)6]2 (4; P-Trz-Py=[3-(1-pyridin-3-yl-[1,2,3]triazol-4-yl)-propyl]phosphonic acid diethyl ester). Upon light excitation at λ=395 nm, complexes 1-4 photodissociate the monodentate pyridyl ligand and form the aqua adduct ions [(η(6) -p-cym)Ru(bpy)(H2O)](2+) and [(η(6) -p-cym)Ru(bpm)(H2O)](2+). Thulium -doped upconverting nanoparticles (UCNPs) are functionalised with 4, thus exploiting their surface affinity for the phosphonate group in the complex. The so-obtained nanosystem UCNP@4 undergoes near-infrared (NIR) photoactivation at λ=980 nm, thus producing the corresponding reactive aqua species that binds the DNA-model base guanosine 5'-monophosphate. PMID:26785101

  4. Biological activity of ruthenium and osmium arene complexes with modified paullones in human cancer cells.

    PubMed

    Mühlgassner, Gerhard; Bartel, Caroline; Schmid, Wolfgang F; Jakupec, Michael A; Arion, Vladimir B; Keppler, Bernhard K

    2012-11-01

    In an attempt to combine the ability of indolobenzazepines (paullones) to inhibit cyclin-dependent kinases (Cdks) and that of platinum-group metal ions to interact with proteins and DNA, ruthenium(II) and osmium(II) arene complexes with paullones were prepared, expecting synergies and an increase of solubility of paullones. Complexes with the general formula [M(II)Cl(η(6)-p-cymene)L]Cl, where M=Ru (1, 3) or Os (2, 4), and L=L(1) (1, 2) or L(2) (3, 4), L(1)=N-(9-bromo-7,12-dihydroindolo[3,2-d][1]-benzazepin-6(5H)-yliden-N'-(2-hydroxybenzylidene)azine and L(2)=N-(9-bromo-7,12-dihydroindolo[3,2-d][1]benzazepin-6-yl)-N'-[3-hydroxy-5-(hydroxymethyl)-2-methylpyridin-4-yl-methylene]azinium chloride (L(2)(*)HCl), were now investigated regarding cytotoxicity and accumulation in cancer cells, impact on the cell cycle, capacity of inhibiting DNA synthesis and inducing apoptosis as well as their ability to inhibit Cdk activity. The MTT (3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide) assay yielded IC(50) values in the nanomolar to low micromolar range. In accordance with cytotoxicity data, the BrdU assay showed that 1 is the most and 4 the least effective of these compounds regarding inhibition of DNA synthesis. Effects on the cell cycle are minor, although concentration-dependent inhibition of Cdk2/cyclin E activity was observed in cell-free experiments. Induction of apoptosis is most pronounced for complex 1, accompanied by a low fraction of necrotic cells, as observed by annexin V-fluorescein isothiocyanate/propidium iodide staining and flow cytometric analysis. PMID:23037896

  5. Oxovanadium(V) tetrathiacalix[4]arene complexes and their activity as oxidation catalysts.

    PubMed

    Hoppe, Elke; Limberg, Christian

    2007-01-01

    With the aim of modeling reactive moieties and relevant intermediates on the surfaces of vanadium oxide based catalysts during oxygenation/dehydrogenation of organic substrates, mono- and dinuclear vanadium oxo complexes of doubly deprotonated p-tert-butylated tetrathiacalix[4]arene (H4TC) have been synthesized and characterized: PPh4[(H2TC)VOCl(2)] (1) and (PPh4)2[{(H2TC)V(O)(mu-O)}2] (2). According to the NMR spectra of the dissolved complexes they both retain the structures adopted in the crystalline state, as revealed by single-crystal X-ray crystallography. Compounds 1 and 2 were tested as catalysts for the oxidation of alcohols with O(2) at 80 degrees C. Both 1 and 2 efficiently catalyze the oxidation of benzyl alcohol, crotyl alcohol, 1-phenyl-1-propanol, and fluorenol, and in most cases dinuclear complex 2 is more active than mononuclear complex 1. Moreover, the two thiacalixarene complexes 1 and 2 are in many instances more active than oxovanadium(V) complexes containing "classical" calixarene ligands tested previously. Complexes 1 and 2 also show significant activity in the oxidation of dihydroanthracene. Further investigations led to the conclusion that 1 acts as precatalyst that is converted to the active species PPh4[(TC)V==O] (3) at 80 degrees C by double intramolecular HCl elimination. For complex 2, the results of mechanistic investigations indicated that the oxidation chemistry takes place at the bridging oxo ligands and that the two vanadium centers cooperate during the process. The intermediate (PPh4)2[{H2TCV(O)}2(mu-OH)(mu-OC13H9)] (4) was isolated and characterized, also with respect to its reactivity, and the results afforded a mechanistic proposal for a reasonable catalytic cycle. The implications which these findings gathered in solution may have for oxidation mechanisms on the surfaces of V-based heterogeneous catalysts are discussed. PMID:17566134

  6. Crystal Structure of an L-Carnitine Complex with Pyrogallol[4]arene

    NASA Astrophysics Data System (ADS)

    Fujisawa, I.; Takeuchi, D.; Kitamura, Y.; Okamoto, R.; Aoki, K.

    2012-03-01

    L-Carnitine is essential for the transport of long-chain fatty acids from cytosol into mitochondria for generating metabolic energy. The survey of crystal structures of carnitine-containing proteins in the Protein Data Bank reveals that carnitine can take several conformations with the quarternary trimethylammonium terminal being always bound to aromatic residues through cation-π interactions in acyltransferases or carnitine-binding proteins. In order to demonstrate the importance of cation-π interaction as a carnitine recognition mechanism in the artificial receptor-ligand system that mimics the carnitine-binding sites, we have determined the crystal structure of a complex formed between L-carnitine and pyrogallol[4]arene (pyrogallol cyclic tetramer: PCT) as a carnitine receptor, 2PCT·2(L-carnitine)·4EtOH. There form two crystallographically independent monomeric [PCT·L-carnitine] substructures, which further form an obliquely arranged capsule-like dimeric [PCT·L-carnitine]2 structure through a pair of O-H (PCT)···O (L-carnitine) hydrogen bonds. This is the first report of PCT complex with chiral molecules. In each of the two monomeric [PCT·L-carnitine] substructures, the L-carnitine molecule takes the elongated form with an intramolecular hydrogen bond between the hydroxyl group and the carboxylate oxygen, and the cationic trimethylammonium moiety is incorporated into the cavity of the bowl-shaped PCT molecule through cation-π interactions. These features are similar to those at the D-carnitine-binding site in the crystal structure of the glycine betaine/carnitine/choline-binding protein complex.

  7. Anticancer potency and multidrug-resistant studies of self-assembled arene-ruthenium metallarectangles.

    PubMed

    Dubey, Abhishek; Min, Jin Wook; Koo, Hyun Jung; Kim, Hyunuk; Cook, Timothy R; Kang, Se Chan; Stang, Peter J; Chi, Ki-Whan

    2013-08-26

    A suite of three tetraruthenium metallacycles have been obtained from [2+2] self-assemblies between N,N'-Di-(4-pyridyl)-1,4,5,8-naphthalenetetracarbo-xydiimide (4) and one of the three dinuclear arene ruthenium clips, (η(6)-p-iPrC6H4Me)2Ru2(OO∩OO)][OTf]2 (OO∩OO = oxalate 1, 2,5-dioxydo-1,4-benzoquinonato (dobq) 2, 5,8-dihydroxy-1,4-naphthaquinonato (donq) 3; OTf = triflate). All complexes were isolated in good yield (>85 %) as triflate salts and were fully characterized by using (1)H NMR and UV/Vis spectroscopies, and high-resolution electrospray mass spectrometry. A single crystal of the metallarectangle 5 was suitable for X-ray diffraction structural characterization. The biological activities of the metallacycles were determined by using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assays, establishing their in vitro anticancer properties. Our results show that for the AGC (gastric cancer) cell lines, the cytotoxicity of (donq)-containing SCC 7 exceeds that of cisplatin, which was used as a control. For HCT15 (colon cancer) cell lines, the cytotoxicity is comparable to both cisplatin and doxorubicin. An in vivo hollow fiber model was used to show growth-inhibitory activity against HCT15 and image-based cytometry experiments indicated that 7 induced apoptosis as the mode of cell death. Complex 7 also showed significant antitumor activity for multidrug-resistant HCT15/CLO2 cell lines, for which doxorubicin was ineffective. PMID:23852626

  8. Biological activity of ruthenium and osmium arene complexes with modified paullones in human cancer cells

    PubMed Central

    Mühlgassner, Gerhard; Bartel, Caroline; Schmid, Wolfgang F.; Jakupec, Michael A.; Arion, Vladimir B.; Keppler, Bernhard K.

    2012-01-01

    In an attempt to combine the ability of indolobenzazepines (paullones) to inhibit cyclin-dependent kinases (Cdks) and that of platinum-group metal ions to interact with proteins and DNA, ruthenium(II) and osmium(II) arene complexes with paullones were prepared, expecting synergies and an increase of solubility of paullones. Complexes with the general formula [MIICl(η6-p-cymene)L]Cl, where M = Ru (1, 3) or Os (2, 4), and L = L1 (1, 2) or L2 (3, 4), L1 = N-(9-bromo-7,12-dihydroindolo[3,2-d][1]-benzazepin-6(5H)-yliden-N′-(2-hydroxybenzylidene)azine and L2 = N-(9-bromo-7,12-dihydroindolo[3,2-d][1]benzazepin-6-yl)-N′-[3-hydroxy-5-(hydroxymethyl)-2-methylpyridin-4-yl-methylene]azinium chloride (L2*HCl), were now investigated regarding cytotoxicity and accumulation in cancer cells, impact on the cell cycle, capacity of inhibiting DNA synthesis and inducing apoptosis as well as their ability to inhibit Cdk activity. The MTT (3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide) assay yielded IC50 values in the nanomolar to low micromolar range. In accordance with cytotoxicity data, the BrdU assay showed that 1 is the most and 4 the least effective of these compounds regarding inhibition of DNA synthesis. Effects on the cell cycle are minor, although concentration-dependent inhibition of Cdk2/cyclin E activity was observed in cell-free experiments. Induction of apoptosis is most pronounced for complex 1, accompanied by a low fraction of necrotic cells, as observed by annexin V–fluorescein isothiocyanate/propidium iodide staining and flow cytometric analysis. PMID:23037896

  9. Synthesis, Structure, and Molecular Recognition of S6 - and (SO2 )6 -Corona[6](het)arenes: Control of Macrocyclic Conformation and Properties by the Oxidation State of the Bridging Heteroatoms.

    PubMed

    Guo, Qing-Hui; Zhao, Liang; Wang, Mei-Xiang

    2016-05-10

    We report herein the synthesis, structure, and molecular recognition of S6 - and (SO2 )6 -corona[6](het)arenes, and demonstrate a unique and efficient strategy of regulating macrocyclic conformation and properties by adjusting the oxidation state of the heteroatom linkages. The one-pot nucleophilic aromatic substitution reaction of 1,4-benzenedithiol derivatives, biphenyl-4,4'-dithiol and 9,9-dipropyl-9H-fluorene-2,7-dithiol with 3,6-dichlorotetrazine afforded S6 -corona[3]arene[3]tetrazines. These compounds underwent inverse-electron-demand Diels-Alder reaction with enamines and norbornadiene to produce S6 -corona[3]arene[3]pyridazines. Facile oxidation of sulfide linkages yielded (SO2 )6 -corona[3]arene[3]pyridazines. All corona[6](het)arenes adopted generally hexagonal macrocyclic ring structures; however, their electronic properties and conformation could be fine-tuned by altering the oxidation state of the sulfur linkages. Whereas (SO2 )6 -corona[3]arene[3]pyridazines were electron-deficient, S6 -corona[3]arene[3]pyridazines acted as electron-rich macrocyclic hosts that recognized various organic cations in both aqueous and organic solutions. PMID:27062180

  10. Thiacalix[4]arene-tetra-(quinoline-8- sulfonate): a Sensitive and Selective Fluorescent Sensor for Co (II).

    PubMed

    Modi, Krunal; Panchal, Urvi; Dey, Shuvankar; Patel, Chirag; Kongor, Anita; Pandya, Himanshu A; Jain, V K

    2016-09-01

    A novel fluorescent thiacalix[4]arene-tetra-(quinoline-8-sulfonate) (TCTQ8S) was synthesized by condensation of thiacalix[4]arene (TCA) and 8-quinoline sulfonyl chloride(8QSC). TCTQ8S was characterized by ESI-MS, (1)H-NMR and (13)C-NMR spectroscopic methods. TCTQ8S was found to be an efficient "turn-off" fluorescent sensor for the selective and sensitive recognition of Co(II) ions. The Job's plot measurement reveals a 1:1 stoichiometric ratio. The designed chemosensor exhibited high selectivity toward Co(II) ions vs. other tested metal ions, with a detection limit of up to 1.038 × 10(-9) M. The binding constant and quantum yield for the complex were also determined. Molecular docking studies have been successfully performed to support 1:1 binding of TCTQ8S with the Co(II) metal ion. TCTQ8S was evaluated for real sample analysis on water sample for the detection of Co(II). Graphical Abstract Thiacalix derivatized fluorescent sensor for the selective detection of Co(II). PMID:27392975

  11. Competition between Hydrogen Bonding and Proton Transfer during Specific Anion Recognition by Dihomooxacalix[4]arene Bidentate Ureas.

    PubMed

    Martínez-González, Eduardo; González, Felipe J; Ascenso, José R; Marcos, Paula M; Frontana, Carlos

    2016-08-01

    Competition between hydrogen bonding and proton transfer reactions was studied for systems composed of electrogenerated dianionic species from dinitrobenzene isomers and substituted dihomooxacalix[4]arene bidentate urea derivatives. To analyze this competition, a second-order ErCrCi mechanism was considered where the binding process is succeeded by proton transfer and the voltammetric responses depend on two dimensionless parameters: the first related to hydrogen bonding reactions, and the second one to proton transfer processes. Experimental results indicated that, upon an increase in the concentration of phenyl-substituted dihomooxacalix[4]arene bidentate urea, voltammetric responses evolve from diffusion-controlled waves (where the binding process is at chemical equilibrium) into irreversible kinetic responses associated with proton transfer. In particular, the 1,3-dinitrobenzene isomer showed a higher proton transfer rate constant (∼25 M(-1) s(-1)) compared to that of the 1,2-dinitrobenzene (∼5 M(-1) s(-1)), whereas the 1,4-dinitrobenzene did not show any proton transfer effect in the experimental conditions employed. PMID:27384148

  12. Sulfur dioxide and particles in quiescent volcanic plumes from Poas, Arenal, and Colima volcanos, Costa Rica and Mexico

    NASA Technical Reports Server (NTRS)

    Casadevall, T. J.; Rose, W. I., Jr.; Fuller, W. H.; Hunt, W. H.; Woods, D. C.; Hart, M. A.; Moyers, J. L.; Chuan, R. L.; Friend, J. P.

    1984-01-01

    Measurements of SO2 emission rates and concentrations and of particle distribution, size, shape, and composition were made in quiescent volcanic plumes emitted into the troposphere from Poas and Arenal volcanos, Costa Rica, and Colima volcano, Mexico. SO2 emission rates were 700 + or - 180 metric tons per day (t/d) for Poas, 210 + or - 30 t/d for Arenal, and 320 + or - 50 t/d for Colima. The concentrations of SO2 calculated from the COSPEC/lidar data were 5-380 ppb. Concentrations of SO2 measured directly by flame photometry were 10-250 ppb. Particles collected in the plumes with a quartz crystal microbalance impactor were mostly less than 3 microns in diameter and consisted of droplets of dilute sulfur-bearing solutions and minor amounts of layer silicate particles coated with a sulfur-bearing film or crust. Total particle concentrations were 4.7 micrograms per cu.m for Poas and 18.8 micrograms per cu.m for Colima. Comparison of concentrations of SO2 in the plumes with gas samples collected at fumaroles on the ground suggests that the plumes are diluted by the atmosphere by factors of up to 100,000.

  13. Transition Metal Complexes of Calix[4]arene: Theoretical Investigations into Small Guest Binding within the Host Cavity.

    PubMed

    Murphy, Paul; Dalgarno, Scott J; Paterson, Martin J

    2016-02-11

    The ability to selectively detect or store small molecules, such as gases, is of enormous commercial potential. Calixarenes have been studied extensively as host molecules; however, recent synthetic advances have seen the formation of new polymetallic calixarene clusters, which have not yet been explored for such purposes. We therefore present a theoretical study, using Density Functional Theory, to thoroughly investigate the binding preferences of calix[4]arene, with a variety of transition metal cations coordinated to the calixarene tetraphenolic pocket, toward a series of important small molecules, H2S, SO2, H2O, O2, H2, N2, N2O, CO2, NH3, and HCN. It was found that the inclusion of a metal atom at the lower-rim of the calixarene caused significant strengthening of binding energy with all of the small molecules in our study as compared to metal-free calixarene. The guests, SO2 and NH3, were found to bind strongest with H2 binding weakest. Our calculations predict that simply introducing metal coordination of any type to calix[4]arene will make the largest difference to the binding energies. Subsequently changing the type, oxidation state, or the spin state of the metal coordinated to the calixarene tetraphenolic pocket was found to have a lesser effect on these. PMID:26783648

  14. Surface photochemistry: Diffuse reflectance studies of thioketones included into p-tert-butylcalix[6 and 8]arenes

    NASA Astrophysics Data System (ADS)

    Vieira Ferreira, L. F.; Ferreira Machado, I.; Oliveira, A. S.; Da Silva, J. P.; Krawczyk, A.; Sikorski, M.

    2007-02-01

    This paper presents time resolved laser induced luminescence (LIL) and diffuse reflectance laser flash-photolysis (DRLFP) studies of solid powdered samples of xanthione (XT) and 4H-1-benzopyran-4-thione (BPT). These thioketones form inclusion complexes with p-tert-butylcalix[6]arene (CLX[6]) and p-tert-butylcalix[8]arene (CLX[8]). Room temperature air equilibrated LIL studies for XT/CLX[8] inclusion complex have shown the existence of both fluorescence and delayed fluorescence emission (S 2 → S 0 emissions in the nanosecond and microsecond time ranges, respectively) peaking at ca. 460 nm while phosphorescence peaks at about 670 nm with a half life of about 4 μs. For the BPT/CLX[8] inclusion complex, the emissions now peak at ca. 450 and 630 nm, respectively. When these two thioketones are included into the CLX[6] nanocavities similar luminescence spectra were detected. The phosphorescence spectra in all cases present a clear vibrational structure characteristic of non-polar environments, in accordance with the non-polar character of the calixarene's cavities. Diffuse reflectance transient absorption spectra revealed in all cases the presence of the triplet state of the thioketones and also of longer lived species. The use of chromatographic methods (GC-MS) allowed us to identify the formation of xanthone, chromone and hydroxy-thioketones following laser irradiation at 355 or 337 nm.

  15. Reversible dioxygen binding and arene hydroxylation reactions: Kinetic and thermodynamic studies involving ligand electronic and structural variations

    PubMed Central

    Karlin, Kenneth D.; Zhang, Christiana Xin; Rheingold, Arnold L.; Galliker, Benedikt; Kaderli, Susan; Zuberbühler, Andreas D.

    2012-01-01

    Copper-dioxygen interactions are of intrinsic importance in a wide range of biological and industrial processes. Here, we present detailed kinetic/thermodynamic studies on the O2-binding and arene hydroxylation reactions of a series of xylyl-bridged binuclear copper(I) complexes, where the effects of ligand electronic and structural elements on these reactions are investigated. Ligand 4-pyridyl substituents influence the reversible formation of side-on bound μ-η2:η2-peroxodicopper(II) complexes, with stronger donors leading to more rapid formation and greater thermodynamic stability of product complexes [CuII2(RXYL)(O22−)]2+. An interaction of the latter with the xylyl π-system is indicated. Subsequent peroxo electrophilic attack on the arene leads to C–H activation and oxygenation with hydroxylated products [CuII2(RXYLO2−)(−OH)]2+ being formed. A related unsymmetrical binucleating ligand was also employed. Its corresponding O2-adduct [CuII2(UN)(O22−)]2+ is more stable, but primarily because the subsequent decay by hydroxylation is in a relative sense slower. The study emphasizes how ligand electronic effects can and do influence and tune copper(I)–dioxygen complex formation and subsequent reactivity. PMID:23420124

  16. A simple and rapid creatinine sensing via DLS selectivity, using calix[4]arene thiol functionalized gold nanoparticles.

    PubMed

    Sutariya, Pinkesh G; Pandya, Alok; Lodha, Anand; Menon, Shobhana K

    2016-01-15

    A new, simple, ultra-sensitive and selective approach has been reported for the "on spot" colorimetric detection of creatinine based on calix[4]arene functionalized gold nanoparticles (AuNPs) with excellent discrimination in the presence of other biomolecules. The lower detection limit of the method is 2.16nM. The gold nanoparticles and p-tert-butylcalix[4]arene were synthesized by microwave assisted method. Specifically, in our study, we used dynamic light scattering (DLS) which is a powerful method for the determination of small changes in particle size, improved selectivity and sensitivity of the creatinine detection system over colorimetric method. The nanoassembly is characterized by Transmission electron microscopy (TEM), DLS, UV-vis and ESI-MS spectroscopy, which demonstrates the binding affinity due its ability of hydrogen bonding and electrostatic interaction between -NH group of creatinine and pSDSC4. It exhibits fast response time (<60s) to creatinine and has long shelf-life (>5 weeks). The developed pSDSC4-AuNPs based creatinine biosensor will be established as simple, reliable and accurate tool for the determination of creatinine in human urine samples. PMID:26592650

  17. A Remote Arene-Binding Site on Prostate Specific Membrane Antigen Revealed by Antibody-Recruiting Small Molecules

    SciTech Connect

    Zhang, Andrew X.; Murelli, Ryan P.; Barinka, Cyril; Michel, Julien; Cocleaza, Alexandra; Jorgensen, William L.; Lubkowski, Jacek; Spiegel, David A.

    2010-09-27

    Prostate specific membrane antigen (PSMA) is a membrane-bound glutamate carboxypeptidase overexpressed in many forms of prostate cancer. Our laboratory has recently disclosed a class of small molecules, called ARM-Ps (antibody-recruiting molecule targeting prostate cancer) that are capable of enhancing antibody-mediated immune recognition of prostate cancer cells. Interestingly, during the course of these studies, we found ARM-Ps to exhibit extraordinarily high potencies toward PSMA, compared to previously reported inhibitors. Here, we report in-depth biochemical, crystallographic, and computational investigations which elucidate the origin of the observed affinity enhancement. These studies reveal a previously unreported arene-binding site on PSMA, which we believe participates in an aromatic stacking interaction with ARMs. Although this site is composed of only a few amino acid residues, it drastically enhances small molecule binding affinity. These results provide critical insights into the design of PSMA-targeted small molecules for prostate cancer diagnosis and treatment; more broadly, the presence of similar arene-binding sites throughout the proteome could prove widely enabling in the optimization of small molecule-protein interactions.

  18. FRET-capable supramolecular polymers based on a BODIPY-bridged pillar[5]arene dimer with BODIPY guests for mimicking the light-harvesting system of natural photosynthesis.

    PubMed

    Meng, Lu-Bo; Li, Dongqi; Xiong, Shuhan; Hu, Xiao-Yu; Wang, Leyong; Li, Guigen

    2015-03-18

    AA/BB-type and A2/B3-type FRET-capable supramolecular polymers based on a BODIPY-bridged pillar[5]arene dimer and two BODIPY derivative guests have been successfully constructed and their application in mimicking the light-harvesting system of natural photosynthesis was studied. PMID:25690934

  19. Aqueous aerobic oxidation of alkyl arenes and alcohols catalyzed by copper(II) phthalocyanine supported on three-dimensional nitrogen-doped graphene at room temperature.

    PubMed

    Mahyari, Mojtaba; Laeini, Mohammad Sadegh; Shaabani, Ahmad

    2014-07-25

    Copper(ii) tetrasulfophthalocyanine supported on three-dimensional nitrogen-doped graphene-based frameworks was synthesized and introduced as a bifunctional catalyst for selective aerobic oxidation of alkyl arenes and alcohols to the corresponding carbonyl compounds. The ease of catalyst separation, high turnover, low catalyst loading and recyclability could potentially render it applicable in industrial setting. PMID:24912023

  20. Multifunctional supramolecular vesicles based on the complex of ferrocenecarboxylic acid capped pillar[5]arene and a galactose derivative for targeted drug delivery.

    PubMed

    Chang, Yincheng; Hou, Chenxi; Ren, Jingli; Xin, Xiaoting; Pei, Yuxin; Lu, Yuchao; Cao, Shoupeng; Pei, Zhichao

    2016-07-21

    Supramolecular vesicles based on the host-guest complexation of ferrocenecarboxylic acid capped pillar[5]arene and a galactose derivative have been constructed, which showed dual-responsiveness and cancer cells targetability resulting from its ferrocenecarboxylic acid units and galactose units, respectively. This work provides a good example for the construction of multifunctional nanocarriers for targeted drug delivery. PMID:27387299

  1. Direct conversion of allyl arenes to aryl ethylketones via a TBHP-mediated palladium-catalyzed tandem isomerization-Wacker oxidation of terminal alkenes.

    PubMed

    Zhao, JinWu; Liu, Li; Xiang, ShiJian; Liu, Qiang; Chen, HuoJi

    2015-05-28

    A TBHP-mediated palladium-catalyzed tandem isomerization-Wacker oxidation of terminal alkenes was developed. This methodology provides a new efficient and simple route for conversion of a range of allyl arenes directly into aryl ethylketones in good yields with high chemoselectivity. PMID:25884269

  2. An Investigation of (Diacetoxyiodo)arenes as Precursors for Preparing No-Carrier-Added [(18)F]Fluoroarenes from Cyclotron-Produced [(18)F]Fluoride Ion.

    PubMed

    Haskali, Mohammad B; Telu, Sanjay; Lee, Yong-Sok; Morse, Cheryl L; Lu, Shuiyu; Pike, Victor W

    2016-01-01

    Treatment of (diacetoxyiodo)arenes (1a-1u) with cyclotron-produced [(18)F]fluoride ion rapidly affords no-carrier-added [(18)F]fluoroarenes (2a-2u) in useful yields and constitutes a new method for converting substituted iodoarenes into substituted [(18)F]fluoroarenes in just two steps. PMID:26641128

  3. pH-Responsive supramolecular vesicles assembled by water-soluble pillar[5]arene and a BODIPY photosensitizer for chemo-photodynamic dual therapy.

    PubMed

    Meng, Lu-Bo; Zhang, Wenyi; Li, Dongqi; Li, Yan; Hu, Xiao-Yu; Wang, Leyong; Li, Guigen

    2015-10-01

    Supramolecular vesicles which can successfully encapsulate DOX and exhibit rapid drug release in a low-pH environment are constructed based on the host-guest interaction of water-soluble pillar[5]arene and a BODIPY derivative. They show remarkable combination of chemo- and photodynamic activities, suggesting a promising drug nanocarrier. PMID:26270623

  4. One-step heterylation at the upper rim of calix[4]arene with 1,2,4-triazin-5(2H)-ones.

    PubMed

    Beresnev, Dmitry G; Itsikson, Nadezhda A; Chupakhin, Oleg N; Charushin, Valery N; Kodess, Mikhail I; Butakov, Alexander I; Rusinov, Gennady L; Morzherin, Yuri Yu; Konovalov, Alexander I; Antipin, Igor S

    2006-10-13

    A convenient way to modify calix[4]arenes based on the direct C-C coupling reaction of their phenol moiety with 1,2,4-triazines has been advanced, and the ability of modified calixarenes to provide transport of La3+ and Ga3+ cations through organic membranes has been examined. PMID:17025324

  5. CALIX[6]ARENE DERIVATIVES BEARING SULFONATE AND ALKYL GROUPS AS SURFACTANTS IN SC(OTF)3-CATALYZED MUKAIYAMA ALDOL REACTIONS IN WATER. (R822668)

    EPA Science Inventory

    Abstract

    Amphiphilic calix[6]arene derivatives 1a¯b were found to be efficient surfactants for Sc(OTf)3-catalyzed Mukaiyama aldol reaction of silyl enol ethers with aldehydes in water. The results indicated t...

  6. Three-dimensional stochastic adjustment of volcano geodetic network in Arenal volcano, Costa Rica

    NASA Astrophysics Data System (ADS)

    Muller, C.; van der Laat, R.; Cattin, P.-H.; Del Potro, R.

    2009-04-01

    before it is built. Moreover, a posterior analysis enables identifying, and hence dismissing, measurement errors (antenna height, atmospheric effects, etc.). Here we present a preliminary effort to apply this technique to volcano deformation. A geodetic network has been developed on the western flank of the Arenal volcano in Costa Rica. It is surveyed with GNSS, angular and EDM (Electronic Distance Measurements) measurements. Three measurement campaigns were carried out between February and June 2008. The results show consistent and accurate output of deformation and uncertainty for each of the 12 benchmarks surveyed. The three campaigns also prove the repeatability and consistency of the statistical indicators and the displacement vectors. Although, this methodology has only recently been applied to volcanoes, we suggest that due to its cost-effective high-quality results it has the potential to be incorporated into the design and analysis of volcano geodetic networks worldwide.

  7. Timescales of degassing and crystallization implied by 210Po- 210Pb- 226Ra disequilibria for andesitic lavas erupted from Arenal volcano

    NASA Astrophysics Data System (ADS)

    Reagan, Mark K.; Tepley, Frank J.; Gill, James B.; Wortel, Matthew; Garrison, Jennifer

    2006-09-01

    Disequilibrium between 210Po, 210Pb, and 226Ra was measured on whole rocks and plagioclase mineral separates erupted between 1968 and 2003 from Arenal volcano with a goal of monitoring the volatile fluxing and crystallization in the decades and years leading up to eruption. Degassing during the eruption was found to remove nearly all 210Po from Arenal lavas, which appears to be true of lava eruptions in general. Most of Arenal's lavas have ( 210Pb)/( 226Ra) ratios within 20% of equilibrium, indicating that most of the magmas involved in this eruption did not have strong, persistent fluxes of 222Rn in or out of the system during the decades leading to eruption. This is consistent with a time-frame of differentiation from basalt to basaltic andesite exceeding a century. Lava erupted in 1971 had ( 210Pb) in excess of ( 226Ra) by as much as a factor of 2. These lavas were the first to mark the change in geochemical trends that were likely caused by the arrival of a new magma at the surface at Arenal [Ryder, C.H., Gill, J.B., Tepley III, F., Ramos, F., Reagan, M., this issue. Closed to open system differentiation at Arenal Volcano (1968-2003). Journal of Volcanology and Geothermal Research.], suggesting that the 210Pb excess was related to the first appearance of this magma. The high ( 210Pb)/( 226Ra) ratio in this lava apparently reflects Rn-degassing from large volumes of underlying magma and/or extraction of Rn from conduit-area rocks or fluids due to deformation and heating. Plagioclase mineral separates had 210Po- 210Pb- 226Ra disequilibrium patterns suggesting a growth period stretching over a period of more than 50 years up to the time of eruption.

  8. Triggering the approach of an arene or heteroarene towards an aldehyde via Lewis acid-aldehyde communication.

    PubMed

    Pratihar, Sanjay

    2016-03-01

    The present work reports a combined experimental/computational study of the Lewis acid promoted hydroxyalkylation reaction involving aldehyde and arene/heteroarene and reveals a mechanism in which the rate determining aldehyde to alcohol formation via a four-member cyclic transition state (TS) involves a transfer of hydrogen from arene/heteroarene C-H to aldehyde oxygen with the breaking of the C-H bond and formation of C-C and O-H bonds. The effect of different Sn(iv) derivatives on the hydroxyalkylation reaction from different in situ NMR and computational studies reveals that although the exergonic formation of the intermediate and its gained electrophilicity at the carbonyl carbon drive the reaction in SnCl4 compared to other Sn(iv) derivatives, the overall reaction is low yielding because of its stable intermediate. With respect to different aldehydes, LA promoted hydroxylation was found to be more feasible for an electron withdrawing aldehyde compared to electron rich aldehyde because of lower stability, enhanced electrophilicity gained at the aldehyde center, and a lower activation barrier between its intermediate and TS in the former as compared to the latter. The relative stability of the LA-aldehyde adduct decreases in the order SnCl4 > AlCl3 > InCl3 > BF3 > ZnCl2 > TiCl4 > SiCl4, while the activation barrier (ΔG(#)) between intermediate and transition states increases in the order AlCl3 < SnCl4 < InCl3 < BF3 < TiCl4 < ZnCl2 < SiCl4. On the other hand, the activation barriers in the case of different arenes/heteroarenes are in the order of indole < furan < anisole < thiophene < toluene < benzene < chlorobenzene < cyanobenzene, which suggests a facile reaction in the case of indole and the most difficult reaction in the case of cyanobenzene. The ease of formation of the corresponding diaryl methyl carbocation from the alcohol-LA intermediate is responsible for the determination of the undesired product and is found to be more viable in the case of strong

  9. Crystal structures of resorcin[4]arene and pyrogallol[4]arene complexes with DL-pipecolinic acid. Model compounds for the recognition of the pipecolinyl ring, a key fragment of FK506, through C-H⋯π interaction

    NASA Astrophysics Data System (ADS)

    Fujisawa, Ikuhide; Kitamura, Yuji; Kato, Ryo; Murayama, Kazutaka; Aoki, Katsuyuki

    2014-01-01

    Resorcin[4]arene (resorcinol cyclic tetramer, abbreviated as RCT) or pyrogallol[4]arene (pyrogallol cyclic tetramer, PCT) form host-guest 1:1 complexes with DL-pipecolinic acid (DL-pipeH), RCT·DL-pipeH·EtOH·8H2O (1), PCT DL-pipeH·EtOH·4H2O (2), and PCT·DL-pipeH·3H2O (3), whose crystal structures have been determined. In each complex, the pipeH ligand is incorporated into the bowl-shaped cavity of the RCT or PCT host molecules through C-H⋯π interactions between alkyl protons of the piperidine ring of pipeH and π-rings of RCT or PCT, forming an [(RCT/PCT)·pipeH] structural fragment. In 1 and 3, two [(RCT/PCT) pipeH] fragments self-associate across an inversion center to form a guest-mediated, obliquely declined dimeric structure [(RCT/PCT)·L-pipeH·D-pipeH (RCT/PCT)]. In 2, each PCT-capped pipeH ligand bridges to two adjacent PCT molecules to form guest-mediated, optically-discrete helical polymers [PCT·L-pipeH]n or [PCT·D-pipeH]n. An 1H NMR experiment shows that the complexation through C-H⋯π interaction between the piperidine ring of pipeH and π-rings of RCT or PCT occurs also in solution, with the binding constants of 9.7 ± 0.6 M-1 for RCT and 26.5 ± 1.5 M-1 for PCT. These complexes provide a synthetic model for the recognition of the pipecolinyl-ring moiety, a key constituent of immunosuppressant drugs such as FK506, FK520 or rapamycin, by their binding proteins through C-H⋯π interaction.

  10. Development of more labile low electron count Co(I) sources: mild, catalytic functionalization of activated alkanes using a [(Cp*Co)2-μ-(η4:η4-arene)] complex.

    PubMed

    Hung-Low, Fernando; Krogman, Jeremy P; Tye, Jesse W; Bradley, Christopher A

    2012-01-11

    Catalytic transfer dehydrogenation of silyl protected amines, requiring sp(3) C-H bond activation, is mediated by a bridging arene complex of the type [(Cp*Co)(2)-μ-(η(4):η(4)-arene)] under mild conditions. Mechanistic and qualitative rate studies establish the compound as a more reactive Co(I) source when compared to other known Cp*Co(I) complexes. PMID:22083519