The EPR of the triplet state of aryl cations in crystals of diazonium salts

NASA Astrophysics Data System (ADS)

Kondratenko, P. A.; Shrubovich, E. V.; Shulga, S. Z.

The spectra of the electron paramagnetic resonance (EPR) of aryl cations possessing a principle triplet ground-state and orientated in a monocrystal of diazonium salts is studied. It is shown that two nonequivalent paramagnetic centers, which differ in orientation are formed within the crystal. A theoretic description of experimental results is possible only when allowing for the effect of low symmetry. This symmetry is invoked by the interactivity of the paramagnetic center of symmetry C(sub 2v) with the crystal field of symmetry C(sub i).

Tunable Cascade Reaction of Aryl Diazonium Salts and Trialkylamine: Synthesis of Monofluorinated Arylhydrazones and gem-Difluorinated Azo Compounds.

PubMed

Guo, Rui; Zhang, Zhengjuan; Shi, Feng; Tang, Pingping

2016-03-04

The first example of a mild and tunable cascade reaction of aryl diazonium salts and trialkylamine in the presence of Selectfluor to prepare monofluorinated arylhydrazones and gem-difluorinated azo compounds without metal has been explored. In the presence of H2O, the monofluorinated arylhydrazones were observed in moderate to good yield. In the absence of H2O, the gem-difluorinated azo compounds were obtained. The fluorinated arylhydrazones were utilized to synthesize fluorinated pyrazoles and other nitrogen-containing compounds.

Base free aryl coupling of diazonium compounds and boronic esters: self-activation allowing an overall highly practical process.

PubMed

Bonin, Hélène; Delbrayelle, Dominique; Demonchaux, Patrice; Gras, Emmanuel

2010-04-21

Boronic esters have long been considered as poor partners in cross-coupling reactions with arene diazoniums. Here is reported an unprecedented application of self-activated boronic esters in a base-free cross-coupling reaction with diazonium salts under mild and user friendly conditions.

Surface Patterning Using Diazonium Ink Filled Nanopipette.

PubMed

Zhou, Min; Yu, Yun; Blanchard, Pierre-Yves; Mirkin, Michael V

2015-11-03

Molecular grafting of diazonium is a widely employed surface modification technique. Local electrografting of this species is a promising approach to surface doping and related properties tailoring. The instability of diazonium cation complicates this process, so that this species was generated in situ in many reported studies. In this Article, we report the egress transfer of aryl diazonium cation across the liquid/liquid interface supported at the nanopipette tip that can be used for controlled delivery this species to the external aqueous phase for local substrate patterning. An aryl diazonium salt was prepared with weakly coordinating and lipophilic tetrakis(pentafluorophenyl)borate anion stable as a solid and soluble in low polarity media. The chemically stable solution of this salt in 1,2-dichloroethane can be used as "diazonium ink". The ink-filled nanopipette was employed as a tip in the scanning electrochemical microscope (SECM) for surface patterning with the spatial resolution controlled by the pipette orifice radius and a few nanometers film thickness. The submicrometer-size grafted spots produced on the HOPG surface were located and imaged with the atomic force microscope (AFM).

Reactive Diazonium-Modified Silica Fillers for High-Performance Polymers.

PubMed

Sandomierski, Mariusz; Strzemiecka, Beata; Chehimi, Mohamed M; Voelkel, Adam

2016-11-08

We describe a simple way of modification of three silica-based fillers with in situ generated 4-hydroxymethylbenzenediazonium salt ( + N 2 -C 6 H 4 -CH 2 OH). The rationale for using a hydroxyl-functionalized diazonium salt is that it provides surface-functionalized fillers that can react with phenolic resins. The modification of silica by diazonium salts was assessed using Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). FTIR spectroscopy permitted the tracking of benzene ring breathing and C-C. The absence of the characteristic N≡N stretching vibration in the 2200-2300 cm -1 range indicates the loss of the diazonium group. XPS results indicate a higher C/Si atomic ratio after the diazonium modification of fillers and the presence of π-π* C1s satellite peaks characteristic of the surface-tethered aromatic species. Adhesion of aryl layers to the silicas is excellent because they withstand harsh thermal and organic solvent treatments. Phenolic resins (used, for example, as binders in abrasive products) were filled with diazonium-modified silicas at 10-25 wt %. The reactivity of the fillers toward phenolic resins was evaluated by the determination of the flow distance. After annealing at 180 °C, the diazonium-modified silica/phenolic resin composites were mechanically tested using the three-point flexural method. The flexural strength was found to be up to 35% higher than that of the composites prepared without any diazonium salts. Diazonium-modified silica with surface-bound -CH 2 -OH groups is thus ideal reactive filler for phenolic resins. Such filler ensures interfacial chemical reactions with the matrix and imparts robust mechanical properties to the final composites. This specialty diazonium-modified silica will find potential application as fillers in the composites for the abrasive industry. More generally, aryl diazonium salts are a unique new series of compounds for tailoring the surface properties of fillers and tuning the physicochemical and mechanical properties of polymer composites.

Protein resistance of surfaces modified with oligo(ethylene glycol) aryl diazonium derivatives.

PubMed

Fairman, Callie; Ginges, Joshua Z; Lowe, Stuart B; Gooding, J Justin

2013-07-22

Anti-fouling surfaces are of great importance for reducing background interference in biosensor signals. Oligo(ethylene glycol) (OEG) moieties are commonly used to confer protein resistance on gold, silicon and carbon surfaces. Herein, we report the modification of surfaces using electrochemical deposition of OEG aryl diazonium salts. Using electrochemical and contact angle measurements, the ligand packing density is found to be loose, which supports the findings of the fluorescent protein labelling that aryl diazonium OEGs confer resistance to nonspecific adsorption of proteins albeit lower than alkane thiol-terminated OEGs. In addition to protein resistance, aryl diazonium attachment chemistry results in stable modification. In common with OEG species on gold electrodes, OEGs with distal hydroxyl moieties do confer superior protein resistance to those with a distal methoxy group. This is especially the case for longer derivatives where superior coiling of the OEG chains is possible. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

One-step formation of bifunctionnal aryl/alkyl grafted films on conducting surfaces by the reduction of diazonium salts in the presence of alkyl iodides.

PubMed

Hetemi, Dardan; Hazimeh, Hassan; Decorse, Philippe; Galtayries, Anouk; Combellas, Catherine; Kanoufi, Frédéric; Pinson, Jean; Podvorica, Fetah I

2015-05-19

The formation of partial perfluoroalkyl or alkyl radicals from partial perfluoroalkyl or alkyl iodides (ICH2CH2C6F13 and IC6H13) and their reaction with surfaces takes place at low driving force (∼-0.5 V/SCE) when the electrochemical reaction is performed in acetonitrile in the presence of diazonium salts (ArN2(+)), at a potential where the latter is reduced. By comparison to the direct grafting of ICH2CH2C6F13, this corresponds to a gain of ∼2.1 V in the case of 4-nitrobenzenediazonium. Such electrochemical reaction permits the modification of gold surfaces (and also carbon, iron, and copper) with mixed aryl-alkyl groups (Ar = 3-CH3-C6H4, 4-NO2-C6H4, and 4-Br-C6H4, R = C6H13 or (CH2)2-C6F13). These strongly bonded mixed layers are characterized by IRRAS, XPS, ToF-SIMS, ellipsometry, water contact angles, and cyclic voltammetry. The relative proportions of grafted aryl and alkyl groups can be varied along with the relative concentrations of diazonium and iodide components in the grafting solution. The formation of the films is assigned to the reaction of aryl and alkyl radicals on the surface and on the first grafted layer. The former is obtained from the electrochemical reduction of the diazonium salt; the latter results from the abstraction of an iodine atom by the aryl radical. The mechanism involved in the growth of the film provides an example of complex surface radical chemistry.

Diazonium cation-exchanged clay: an efficient, unfrequented route for making clay/polymer nanocomposites.

PubMed

Salmi, Zakaria; Benzarti, Karim; Chehimi, Mohamed M

2013-11-05

We describe a simple, off-the-beaten-path strategy for making clay/polymer nanocomposites through tandem diazonium salt interface chemistry and radical photopolymerization. Prior to photopolymerization, sodium montmorillonite (MMT) was ion exchanged with N,N'-dimethylbenzenediazonium cation (DMA) from the tetrafluoroborate salt precursor. DMA acts as a hydrogen donor for benzophenone in solution; this pair of co-initiators permits us to photopolymerize glycidyl methacrylate (GMA) between the lamellae of the diazonium-modified clay, therefore providing intercalated MMT-PGMA nanocomposites with an onset of exfoliation. This work conclusively provides a new approach for bridging reactive and functional polymers to layered nanomaterials via aryl diazonium salts in a simple, fast, efficient cation-exchange approach.

Multicomponent, flow diazotization/Mizoroki-Heck coupling protocol: dispelling myths about working with diazonium salts.

PubMed

Nalivela, Kumara S; Tilley, Michael; McGuire, Michael A; Organ, Michael G

2014-05-26

A single pass flow diazotization/Mizoroki-Heck protocol has been developed for the production of cinnimoyl and styryl products. The factors that govern aryl diazonium salt stability have been examined in detail leading to the development of a MeOH/DMF co-solvent system in which the diazonium salts can be generated in the presence of all other reaction components and then coupled selectively to give the desired products. Finally the key role of the reaction quench for flow reactions has been demonstrated. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

In situ diazonium-modified flexible ITO-coated PEN substrates for the deposition of adherent silver-polypyrrole nanocomposite films.

PubMed

Samanta, Soumen; Bakas, Idriss; Singh, Ajay; Aswal, Dinesh K; Chehimi, Mohamed M

2014-08-12

In this paper, we report a simple and versatile process of electrografting the aryl multilayers onto indium tin oxide (ITO)-coated flexible poly(ethylene naphthalate) (PEN) substrates using a diazonium salt (4-pyrrolylphenyldiazonium) solution, which was generated in situ from a reaction between the 4-(1H-pyrrol-1-yl)aniline precursor and sodium nitrite in an acidic medium. The first aryl layer bonds with the ITO surface through In-O-C and Sn-O-C bonds which facilitate the formation of a uniform aryl multilayer that is ∼8 nm thick. The presence of the aryl multilayer has been confirmed by impedance spectroscopy as well as by electron-transfer blocking measurements. These in situ diazonium-modified ITO-coated PEN substrates may find applications in flexible organic electronics and sensor industries. Here we demonstrate the application of diazonium-modified flexible substrates for the growth of adherent silver/polpyrrole nanocomposite films using surface-confined UV photopolymerization. These nanocomposite films have platelet morphology owing to the template effect of the pyrrole-terminated aryl multilayers. In addition, the films are highly doped (32%). This work opens new areas in the design of flexible ITO-conductive polymer hybrids.

Visible‐Light‐Mediated Selective Arylation of Cysteine in Batch and Flow

PubMed Central

Bottecchia, Cecilia; Rubens, Maarten; Gunnoo, Smita B.; Hessel, Volker; Madder, Annemieke

2017-01-01

Abstract A mild visible‐light‐mediated strategy for cysteine arylation is presented. The method relies on the use of eosin Y as a metal‐free photocatalyst and aryldiazonium salts as arylating agents. The reaction can be significantly accelerated in a microflow reactor, whilst allowing the in situ formation of the required diazonium salts. The batch and flow protocol described herein can be applied to obtain a broad series of arylated cysteine derivatives and arylated cysteine‐containing dipeptides. Moreover, the method was applied to the chemoselective arylation of a model peptide in biocompatible reaction conditions (room temperature, phosphate‐buffered saline (PBS) buffer) within a short reaction time. PMID:28805276

Core/shell, protuberance-free multiwalled carbon nanotube/polyaniline nanocomposites via interfacial chemistry of aryl diazonium salts.

PubMed

Mekki, Ahmed; Samanta, Soumen; Singh, Ajay; Salmi, Zakaria; Mahmoud, Rachid; Chehimi, Mohamed M; Aswal, Dinesh K

2014-03-15

Highly uniform core-shell like multi-walled carbon nanotubes-polyaniline (MWCNT-PANI) nanocomposites were prepared in two steps (i) surface modification of MWCNTs with a 4-aminodiphenylamine group via in situ diazonium generation process; and (ii) polymerization of aniline onto surface modified MWCNTs. This functionalization helped to easily disperse the MWCNTs in acidic solutions; hence it is suitable for the chemical oxidative polymerization of aniline. It was found that MWCNT-PANI nano-composites with higher MWCNTs loading yield PANI chains with more quinoid units than the pure PANI, which results in significant improvement in the conductivity of the composites. This facile approach of synthesizing core-shell nanocomposites highlights the efficiency of the interfacial chemistry of aryl diazonium salts in generating conductive polymer/MWCNT nanocomposites with enhanced conductivity and high surface area. Copyright © 2013 Elsevier Inc. All rights reserved.

A general access to organogold(iii) complexes by oxidative addition of diazonium salts.

PubMed

Huang, Long; Rominger, Frank; Rudolph, Matthias; Hashmi, A Stephen K

2016-05-11

At room temperature under mild photochemical conditions, namely irradiation with a simple blue light LED, gold(i) chloro complexes of both phosphane and carbene ligands in combination with aryldiazonium salts afford arylgold(iii) complexes. With chelating P,N-ligands cationic six- or five-membered chelate complexes were isolated in the form of salts with weakly coordinating counter anions that were brought in from the diazonium salt. With monodentate P ligands or N-heterocyclic carbene ligands and diazonium chlorides neutral arylgold(iii) dichloro complexes were obtained. The coordination geometry was determined by X-ray crystal structure analyses of representative compounds, a cis arrangement of the aryl and the phosphane ligand at the square planar gold(iii) center is observed.

Dual Visible Light Photoredox and Gold-Catalyzed Arylative Ring Expansion

PubMed Central

2015-01-01

A combination of visible light photocatalysis and gold catalysis is applied to a ring expansion–oxidative arylation reaction. The reaction provides an entry into functionalized cyclic ketones from the coupling reaction of alkenyl and allenyl cycloalkanols with aryl diazonium salts. A mechanism involving generation of an electrophilic gold(III)–aryl intermediate is proposed on the basis of mechanistic studies, including time-resolved FT-IR spectroscopy. PMID:24730447

Pd-catalyzed arylation reactions with phenol diazonium salts: application in the synthesis of diarylheptanoids.

PubMed

Schmidt, Bernd; Hölter, Frank; Kelling, Alexandra; Schilde, Uwe

2011-05-06

The first total synthesis of the natural product (3S,7R)-5,6-dehydro-de-O-methyl centrolobine and various analogues is reported, using a highly regio- and diastereoselective Mizoroki-Heck reaction of phenol diazonium salts and enantiopure dihydropyrans. The assigned relative configuration was confirmed by single-crystal X-ray structure analysis, but a revision of the absolute configuration is proposed based on polarimetric measurement. © 2011 American Chemical Society

Spontaneous grafting of diazonium salts: chemical mechanism on metallic surfaces.

PubMed

Mesnage, Alice; Lefèvre, Xavier; Jégou, Pascale; Deniau, Guy; Palacin, Serge

2012-08-14

The spontaneous reaction of diazonium salts on various substrates has been widely employed since it consists of a simple immersion of the substrate in the diazonium salt solution. As electrochemical processes involving the same diazonium salts, the spontaneous grafting is assumed to give covalently poly(phenylene)-like bonded films. Resistance to solvents and to ultrasonication is commonly accepted as indirect proof of the existence of a covalent bond. However, the most relevant attempts to demonstrate a metal-C interface bond have been obtained by an XPS investigation of spontaneously grafted films on copper. Similarly, our experiments give evidence of such a bond in spontaneously grafted films on nickel substrates in acetonitrile. In the case of gold substrates, the formation of a spontaneous film was unexpected but reported in the literature in parallel to our observations. Even if no interfacial bond was observed, formation of the films was explained by grafting of aryl cations or radicals on the surface arising from dediazoniation, the film growing later by azo coupling, radical addition, or cationic addition on the grafted phenyl layer. Nevertheless, none of these mechanisms fits our experimental results showing the presence of an Au-N bond. In this work, we present a fine spectroscopic analysis of the coatings obtained on gold and nickel substrates that allow us to propose a chemical structure of such films, in particular, their interface with the substrates. After testing the most probable mechanisms, we have concluded in favor of the involvement of two complementary mechanisms which are the direct reaction of diazonium salts with the gold surface that accounts for the observed Au-N interfacial bonds as well as the formation of aryl cations able to graft on the substrate through Au-C linkages.

Aryl Diazonium Chemistry for the Surface Functionalization of Glassy Biosensors.

PubMed

Zheng, Wei; van den Hurk, Remko; Cao, Yong; Du, Rongbing; Sun, Xuejun; Wang, Yiyu; McDermott, Mark T; Evoy, Stephane

2016-03-14

Nanostring resonator and fiber-optics-based biosensors are of interest as they offer high sensitivity, real-time measurements and the ability to integrate with electronics. However, these devices are somewhat impaired by issues related to surface modification. Both nanostring resonators and photonic sensors employ glassy materials, which are incompatible with electrochemistry. A surface chemistry approach providing strong and stable adhesion to glassy surfaces is thus required. In this work, a diazonium salt induced aryl film grafting process is employed to modify a novel SiCN glassy material. Sandwich rabbit IgG binding assays are performed on the diazonium treated SiCN surfaces. Fluorescently labelled anti-rabbit IgG and anti-rabbit IgG conjugated gold nanoparticles were used as markers to demonstrate the absorption of anti-rabbit IgG and therefore verify the successful grafting of the aryl film. The results of the experiments support the effectiveness of diazonium chemistry for the surface functionalization of SiCN surfaces. This method is applicable to other types of glassy materials and potentially can be expanded to various nanomechanical and optical biosensors.

Aryl Diazonium Chemistry for the Surface Functionalization of Glassy Biosensors

PubMed Central

Zheng, Wei; van den Hurk, Remko; Cao, Yong; Du, Rongbing; Sun, Xuejun; Wang, Yiyu; McDermott, Mark T.; Evoy, Stephane

2016-01-01

Nanostring resonator and fiber-optics-based biosensors are of interest as they offer high sensitivity, real-time measurements and the ability to integrate with electronics. However, these devices are somewhat impaired by issues related to surface modification. Both nanostring resonators and photonic sensors employ glassy materials, which are incompatible with electrochemistry. A surface chemistry approach providing strong and stable adhesion to glassy surfaces is thus required. In this work, a diazonium salt induced aryl film grafting process is employed to modify a novel SiCN glassy material. Sandwich rabbit IgG binding assays are performed on the diazonium treated SiCN surfaces. Fluorescently labelled anti-rabbit IgG and anti-rabbit IgG conjugated gold nanoparticles were used as markers to demonstrate the absorption of anti-rabbit IgG and therefore verify the successful grafting of the aryl film. The results of the experiments support the effectiveness of diazonium chemistry for the surface functionalization of SiCN surfaces. This method is applicable to other types of glassy materials and potentially can be expanded to various nanomechanical and optical biosensors. PMID:26985910

Role of adsorbed surfactant in the reaction of aryl diazonium salts with single-walled carbon nanotubes.

PubMed

Hilmer, Andrew J; McNicholas, Thomas P; Lin, Shangchao; Zhang, Jingqing; Wang, Qing Hua; Mendenhall, Jonathan D; Song, Changsik; Heller, Daniel A; Barone, Paul W; Blankschtein, Daniel; Strano, Michael S

2012-01-17

Because covalent chemistry can diminish the optical and electronic properties of single-walled carbon nanotubes (SWCNTs), there is significant interest in developing methods of controllably functionalizing the nanotube sidewall. To date, most attempts at obtaining such control have focused on reaction stoichiometry or strength of oxidative treatment. Here, we examine the role of surfactants in the chemical modification of single-walled carbon nanotubes with aryl diazonium salts. The adsorbed surfactant layer is shown to affect the diazonium derivatization of carbon nanotubes in several ways, including electrostatic attraction or repulsion, steric exclusion, and direct chemical modification of the diazonium reactant. Electrostatic effects are most pronounced in the cases of anionic sodium dodecyl sulfate and cationic cetyltrimethylammonium bromide, where differences in surfactant charge can significantly affect the ability of the diazonium ion to access the SWCNT surface. For bile salt surfactants, with the exception of sodium cholate, we find that the surfactant wraps tightly enough such that exclusion effects are dominant. Here, sodium taurocholate exhibits almost no reactivity under the explored reaction conditions, while for sodium deoxycholate and sodium taurodeoxycholate, we show that the greatest extent of reaction is observed among a small population of nanotube species, with diameters between 0.88 and 0.92 nm. The anomalous reaction of nanotubes in this diameter range seems to imply that the surfactant is less effective at coating these species, resulting in a reduced surface coverage on the nanotube. Contrary to the other bile salts studied, sodium cholate enables high selectivity toward metallic species and small band gap semiconductors, which is attributed to surfactant-diazonium coupling to form highly reactive diazoesters. Further, it is found that the rigidity of anionic surfactants can significantly influence the ability of the surfactant layer to stabilize the diazonium ion near the nanotube surface. Such Coulombic and surfactant packing effects offer promise toward employing surfactants to controllably functionalize carbon nanotubes. © 2011 American Chemical Society

Reaction of the antitumor antibiotic olivomycin I with aryl diazonium salts. Synthesis, cytotoxic and antiretroviral potency of 5-aryldiazenyl-6-O-deglycosyl derivatives of olivomycin I.

PubMed

Tevyashova, Anna N; Olsufyeva, Eugenia N; Turchin, Konstantin F; Balzarini, Jan; Bykov, Eugenyi E; Dezhenkova, Lyubov G; Shtil, Alexander A; Preobrazhenskaya, Maria N

2009-07-15

The azo coupling of the antibiotic olivomycin I (1) with aryl diazonium tetrafluoroborates produced 5-aryldiazenyl-6-O-deglycosyl derivatives of 1. The structures of new compounds were confirmed by (1)H NMR and mass spectrometry analysis. A quantum-chemical study was performed to analyze the possible directions of electrophilic substitution of 1 and the easiness of 6-O-disaccharide hydrolysis in the course of azo coupling. The antiproliferative and anti-retroviral activities of novel derivatives were studied.

Diazonium-derived aryl films on gold nanoparticles: evidence for a carbon-gold covalent bond.

PubMed

Laurentius, Lars; Stoyanov, Stanislav R; Gusarov, Sergey; Kovalenko, Andriy; Du, Rongbing; Lopinski, Gregory P; McDermott, Mark T

2011-05-24

Tailoring the surface chemistry of metallic nanoparticles is generally a key step for their use in a wide range of applications. There are few examples of organic films covalently bound to metal nanoparticles. We demonstrate here that aryl films are formed on gold nanoparticles from the spontaneous reduction of diazonium salts. The structure and the bonding of the film is probed with surface-enhanced Raman scattering (SERS). Extinction spectroscopy and SERS show that a nitrobenzene film forms on gold nanoparticles from the corresponding diazonium salt. Comparison of the SERS spectrum with spectra computed from density functional theory models reveals a band characteristic of a Au-C stretch. The observation of this stretch is direct evidence of a covalent bond. A similar band is observed in high-resolution electron energy loss spectra of nitrobenzene layers on planar gold. The bonding of these types of films through a covalent interaction on gold is consistent with their enhanced stability observed in other studies. These findings provide motivation for the use of diazonium-derived films on gold and other metals in applications where high stability and/or strong adsorbate-substrate coupling are required.

Surface functionalization of cyclic olefin copolymer with aryldiazonium salts: A covalent grafting method

NASA Astrophysics Data System (ADS)

Brisset, Florian; Vieillard, Julien; Berton, Benjamin; Morin-Grognet, Sandrine; Duclairoir-Poc, Cécile; Le Derf, Franck

2015-02-01

Covalent immobilization of biomolecules on the surface of cyclic olefin copolymer (COC) is still a tough challenge. We developed a robust method for COC surface grafting through reaction with aryldiazonium. Chemical diazonium reduction generated an aryl radical and the formation of a grafted film layer on the organic surface. We also demonstrated that the chemical reduction of diazonium salt was not sufficient to form a film on the COC surface. UV illumination had to be combined with chemical reduction to graft an aryl layer onto the COC surface. We optimized organic film deposition by using different chemical reducers, different reaction times and reagent proportions. We characterized surface modifications by fluorescence microscopy and contact angle measurements, infrared spectroscopy, X-ray photoemission spectroscopy and Raman spectroscopy, and assessed the topography of the aryl film by atomic force microscopy. This original strategy allowed us to evidence various organic functions to graft biomolecules onto COC surfaces with a fast and efficient technique.

Photocatalytic surface patterning of cellulose using diazonium salts and visible light.

PubMed

Schroll, Peter; Fehl, Charlie; Dankesreiter, Stephan; König, Burkhard

2013-10-14

Coumarin-functionalized cellulose sheets were chemically modified using a visible light catalyzed "Photo-Meerwein" arylation. Use of a photomask to pattern the surface resulted in directly visible images.

Photocatalytic Surface Patterning of Cellulose using Diazonium Salts and Visible Light

PubMed Central

Schroll, Peter; Fehl, Charlie; Dankesreiter, Stephan

2013-01-01

Coumarin-functionalized cellulose sheets were chemically modified using a visible light catalyzed “Photo-Meerwein” arylation. Use of a photomask to pattern the surface resulted in directly visible images. PMID:23963264

Electrodeposited Organic Layers Formed from Aryl Diazonium Salts for Inhibition of Copper Corrosion

PubMed Central

Chira, Ana; Bucur, Bogdan; Radu, Gabriel-Lucian

2017-01-01

Copper substrates deposed on a gold screen-printed electrode were covered with different aryl diazonium salts by electrodeposition at 0.25 mA for 30 or 300 s. Seven compounds were investigated: 4-aminophenylacetic acid, 4-aminophenethyl alcohol, 4-fluoroaniline, 4-(heptadecafluorooctyl)aniline, 4-aminoantipyrine, 4-(4-aminophenyl)butyric acid and 3,4,5-trimethoxyaniline. Quantitative monitoring of the electrodeposition process was carried out by electrogravimetry using quartz crystal microbalance (QCM). The electrodeposited mass varies between 26 ng/cm2 for 4-fluoroaniline formed during 30 s to 442 ng/cm2 for 4-phenylbutyric acid formed during 300 s. The corrosion inhibition properties of aryl-modified layers have been studied in buffer citrate with pH = 3 or 3.5% NaCl solutions using electrochemical noise (ECN) and Tafel potentiodynamic polarization measurements. A corrosion inhibiting efficiency up to 90% was found. The highest corrosion inhibition was obtained for 4-(4-aminophenyl)butyric acid and the lowest for 4-fluoroaniline. A relation between the inhibition efficiency and the chemical nature of the substituents in the protective layer was found. PMID:28772600

Electrodeposited Organic Layers Formed from Aryl Diazonium Salts for Inhibition of Copper Corrosion.

PubMed

Chira, Ana; Bucur, Bogdan; Radu, Gabriel-Lucian

2017-02-28

Copper substrates deposed on a gold screen-printed electrode were covered with different aryl diazonium salts by electrodeposition at 0.25 mA for 30 or 300 s. Seven compounds were investigated: 4-aminophenylacetic acid, 4-aminophenethyl alcohol, 4-fluoroaniline, 4-(heptadecafluorooctyl)aniline, 4-aminoantipyrine, 4-(4-aminophenyl)butyric acid and 3,4,5-trimethoxyaniline. Quantitative monitoring of the electrodeposition process was carried out by electrogravimetry using quartz crystal microbalance (QCM). The electrodeposited mass varies between 26 ng/cm² for 4-fluoroaniline formed during 30 s to 442 ng/cm² for 4-phenylbutyric acid formed during 300 s. The corrosion inhibition properties of aryl-modified layers have been studied in buffer citrate with pH = 3 or 3.5% NaCl solutions using electrochemical noise (ECN) and Tafel potentiodynamic polarization measurements. A corrosion inhibiting efficiency up to 90% was found. The highest corrosion inhibition was obtained for 4-(4-aminophenyl)butyric acid and the lowest for 4-fluoroaniline. A relation between the inhibition efficiency and the chemical nature of the substituents in the protective layer was found.

Plasmon-mediated chemical surface functionalization at the nanoscale

NASA Astrophysics Data System (ADS)

Nguyen, Mai; Lamouri, Aazdine; Salameh, Chrystelle; Lévi, Georges; Grand, Johan; Boubekeur-Lecaque, Leïla; Mangeney, Claire; Félidj, Nordin

2016-04-01

Controlling the surface grafting of species at the nanoscale remains a major challenge, likely to generate many opportunities in materials science. In this work, we propose an original strategy for chemical surface functionalization at the nanoscale, taking advantage of localized surface plasmon (LSP) excitation. The surface functionalization is demonstrated through aryl film grafting (derived from a diazonium salt), covalently bonded at the surface of gold lithographic nanostripes. The aryl film is specifically grafted in areas of maximum near field enhancement, as confirmed by numerical calculation based on the discrete dipole approximation method. The energy of the incident light and the LSP wavelength are shown to be crucial parameters to monitor the aryl film thickness of up to ~30 nm. This robust and versatile strategy opens up exciting prospects for the nanoscale confinement of functional layers on surfaces, which should be particularly interesting for molecular sensing or nanooptics.Controlling the surface grafting of species at the nanoscale remains a major challenge, likely to generate many opportunities in materials science. In this work, we propose an original strategy for chemical surface functionalization at the nanoscale, taking advantage of localized surface plasmon (LSP) excitation. The surface functionalization is demonstrated through aryl film grafting (derived from a diazonium salt), covalently bonded at the surface of gold lithographic nanostripes. The aryl film is specifically grafted in areas of maximum near field enhancement, as confirmed by numerical calculation based on the discrete dipole approximation method. The energy of the incident light and the LSP wavelength are shown to be crucial parameters to monitor the aryl film thickness of up to ~30 nm. This robust and versatile strategy opens up exciting prospects for the nanoscale confinement of functional layers on surfaces, which should be particularly interesting for molecular sensing or nanooptics. Electronic supplementary information (ESI) available: Additional figures are displayed (from Fig. SI1-SI6) to illustrate the content of the paper, including the proposed mechanisms of diazonium-derived aryl film grafting, the AFM measurements of the aryl film thickness and the calculation by the DDA method. See DOI: 10.1039/C6NR00744A

Aromatic fluorine compounds. VI. Displacement of aryl fluorine in diazonium salts

USGS Publications Warehouse

Finger, G.C.; Oesterling, R.E.

1956-01-01

Several chlorofluorobenzenes have been isolated from the Schiemann synthesis of fluorobenzenes. These have been shown to be the products of two side reactions occurring during thermal decomposition of the dry benzenediazonium fluoborate salt containing coprecipitated sodium chloride, an unavoidable contaminant in large preparations involving the use of hydrochloric acid and sodium fluoborate. The major side reaction and its chloro product were unexpected; a unique displacement of fluorine ortho to the diazonium group was observed. Replacement of the diazo group with chlorine was the predicted side reaction which proved to be minor. Conditions causing the side reactions and the isolation and identification of the products are described.

Cu-Click Compatible Triazabutadienes To Expand the Scope of Aryl Diazonium Ion Chemistry.

PubMed

Cornali, Brandon M; Kimani, Flora W; Jewett, John C

2016-10-07

Triazabutadienes can be used to readily generate reactive aryl diazonium ions under mild, physiologically relevant conditions. These conditions are compatible with a range of functionalities that do not tolerate traditional aryl diazonium ion generation. To increase the utility of this aryl diazonium ion releasing chemistry an alkyne-containing triazabutadiene was synthesized. The copper-catalyzed azide-alkyne cycloaddition ("Cu-click") reaction was utilized to modify the alkyne-containing triazabutadiene and shown to be compatible with the nitrogen-rich triazabutadiene. One of the triazole products was tethered to a fluorophore, thus enabling the direct fluorescent labeling of a model protein.

Simple and Efficient Generation of Aryl Radicals from Aryl Triflates: Synthesis of Aryl Boronates and Aryl Iodides at Room Temperature.

PubMed

Liu, Wenbo; Yang, Xiaobo; Gao, Yang; Li, Chao-Jun

2017-06-28

Despite the wide use of aryl radicals in organic synthesis, current methods to prepare them from aryl halides, carboxylic acids, boronic acids, and diazonium salts suffer from limitations. Aryl triflates, easily obtained from phenols, are promising aryl radical progenitors but remain elusive in this regard. Inspired by the single electron transfer process for aryl halides to access aryl radicals, we developed a simple and efficient protocol to convert aryl triflates to aryl radicals. Our success lies in exploiting sodium iodide as the soft electron donor assisted by light. This strategy enables the scalable synthesis of two types of important organic molecules, i.e., aryl boronates and aryl iodides, in good to high yields, with broad functional group compatibility in a transition-metal-free manner at room temperature. This protocol is anticipated to find potential applications in other aryl-radical-involved reactions by using aryl triflates as aryl radical precursors.

Grafting of diazonium salts on oxides surface: formation of aryl-O bonds on iron oxide nanoparticles

NASA Astrophysics Data System (ADS)

Brymora, Katarzyna; Fouineau, Jonathan; Eddarir, Asma; Chau, François; Yaacoub, Nader; Grenèche, Jean-Marc; Pinson, Jean; Ammar, Souad; Calvayrac, Florent

2015-11-01

Combining ab initio modeling and 57Fe Mössbauer spectrometry, we characterized the nature of the chemical linkage of aminoalkyl arenediazonium salt on the surface of iron oxide nanoparticles. We established that it is built through a metal-oxygen-carbon bonding and not a metal-carbon one, as usually suggested and commonly observed in previously studied metal- or carbon-based surfaces.

Synthesis of stilbene derivatives via visible-light-induced cross-coupling of aryl diazonium salts with nitroalkenes using -NO2 as a leaving group.

PubMed

Zhang, Na; Quan, Zheng-Jun; Zhang, Zhang; Da, Yu-Xia; Wang, Xi-Cun

2016-12-06

The straightforward visible-light-induced synthesis of stilbene compounds via the cross-coupling of nitroalkenes and diazonium tetrafluoroborates under transition-metal-free conditions is described. The protocol uses green LEDs as light sources and eosin Y as an organophotoredox catalyst. Broad substrate scope and exclusive selectivity for the (E)-configuration of stilbenes are observed. This protocol proceeds via a radical pathway, with nitroalkenes serving as the radical acceptor, and the nitro group is cleaved during the process.

Electrografting of alkyl films at low driving force by diverting the reactivity of aryl radicals derived from diazonium salts.

PubMed

Hetemi, Dardan; Kanoufi, Frédéric; Combellas, Catherine; Pinson, Jean; Podvorica, Fetah I

2014-11-25

Alkyl and partial perfluoroalkyl groups are strongly attached to carbon surfaces through (i) the abstraction of the iodine atom from an iodoalkane by the sterically hindered 2,6-dimethylphenyl radical and (ii) the reaction of the ensuing alkyl radical with the carbon surface. Since the 2,6-dimethylphenyl radical is obtained at -0.25 V/Ag/AgCl by reducing the corresponding diazonium salt, the electrografting reaction is facilitated by ∼1.7 V by comparison with the direct electrografting of the iodo compounds. Layers of various thicknesses, including monolayers, are obtained by controlling the time duration of the electrolysis. The grafted films are characterized by electrochemistry, IR, XPS, ellipsometry, and water contact angles.

Spontaneous modification of carbon surface with neutral red from its diazonium salts for bioelectrochemical systems.

PubMed

Guo, Kun; Chen, Xin; Freguia, Stefano; Donose, Bogdan C

2013-09-15

This study introduces a novel and simple method to covalently graft neutral red (NR) onto carbon surfaces based on spontaneous reduction of in situ generated NR diazonium salts. Immobilization of neutral red on carbon surface was achieved by immersing carbon electrodes in NR-NaNO2-HCl solution. The functionalized electrodes were characterized by cyclic voltammetry (CV), atomic force microscope (AFM), and X-ray photoelectron spectroscopy (XPS). Results demonstrated that NR attached in this way retains high electrochemical activity and proved that NR was covalently bound to the carbon surface via the pathway of reduction of aryl diazonium salts. The NR-modified electrodes showed a good stability when stored in PBS solution in the dark. The current output of an acetate-oxidising microbial bioanode made of NR-modified graphite felts were 3.63±0.36 times higher than the unmodified electrodes, which indicates that covalently bound NR can act as electron transfer mediator to facilitate electron transfer from bacteria to electrodes. Copyright © 2013 Elsevier B.V. All rights reserved.

Enhanced interfacial properties of carbon fiber composites via aryl diazonium reaction “on water”

NASA Astrophysics Data System (ADS)

Wang, Yuwei; Meng, Linghui; Fan, Liquan; Ma, Lichun; Qi, Meiwei; Yu, Jiali; Huang, Yudong

2014-10-01

Polyacrylonitrile-based carbon fibers were functionalized with phenyl amine group via aryl diazonium reaction "on water" to improve their interfacial bonding with resin matrix. Raman spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy were employed to characterize ordered degree, functional groups, chemical states and morphology of carbon fiber surface, respectively. The results showed that phenyl amine groups were grafted on the fiber surface successfully. Mechanical property test results indicated that the aryl diazonium reaction in this paper could improve the interfacial shear strength by 73%, while the tensile strength was down very slightly. Hence aryl diazonium reaction "on water" could be a facile green platform to functionalize carbon fibers for many interesting applications.

Electrochemical Functionalization of Graphene at the Nanoscale with Self-Assembling Diazonium Salts.

PubMed

Xia, Zhenyuan; Leonardi, Francesca; Gobbi, Marco; Liu, Yi; Bellani, Vittorio; Liscio, Andrea; Kovtun, Alessandro; Li, Rongjin; Feng, Xinliang; Orgiu, Emanuele; Samorì, Paolo; Treossi, Emanuele; Palermo, Vincenzo

2016-07-26

We describe a fast and versatile method to functionalize high-quality graphene with organic molecules by exploiting the synergistic effect of supramolecular and covalent chemistry. With this goal, we designed and synthesized molecules comprising a long aliphatic chain and an aryl diazonium salt. Thanks to the long chain, these molecules physisorb from solution onto CVD graphene or bulk graphite, self-assembling in an ordered monolayer. The sample is successively transferred into an aqueous electrolyte, to block any reorganization or desorption of the monolayer. An electrochemical impulse is used to transform the diazonium group into a radical capable of grafting covalently to the substrate and transforming the physisorption into a covalent chemisorption. During covalent grafting in water, the molecules retain the ordered packing formed upon self-assembly. Our two-step approach is characterized by the independent control over the processes of immobilization of molecules on the substrate and their covalent tethering, enabling fast (t < 10 s) covalent functionalization of graphene. This strategy is highly versatile and works with many carbon-based materials including graphene deposited on silicon, plastic, and quartz as well as highly oriented pyrolytic graphite.

Diazonium Chemistry for the Bio-Functionalization of Glassy Nanostring Resonator Arrays

PubMed Central

Zheng, Wei; Du, Rongbing; Cao, Yong; Mohammad, Mohammad A.; Dew, Steven K.; McDermott, Mark T.; Evoy, Stephane

2015-01-01

Resonant glassy nanostrings have been employed for the detection of biomolecules. These devices offer high sensitivity and amenability to large array integration and multiplexed assays. Such a concept has however been impaired by the lack of stable and biocompatible linker chemistries. Diazonium salt reduction-induced aryl grafting is an aqueous-based process providing strong chemical adhesion. In this work, diazonium-based linker chemistry was performed for the first time on glassy nanostrings, which enabled the bio-functionalization of such devices. Large arrays of nanostrings with ultra-narrow widths down to 10 nm were fabricated employing electron beam lithography. Diazonium modification was first developed on SiCN surfaces and validated by X-ray photoelectron spectroscopy. Similarly modified nanostrings were then covalently functionalized with anti-rabbit IgG as a molecular probe. Specific enumeration of rabbit IgG was successfully performed through observation of downshifts of resonant frequencies. The specificity of this enumeration was confirmed through proper negative control experiments. Helium ion microscopy further verified the successful functionalization of nanostrings. PMID:26263989

Diazonium Chemistry for the Bio-Functionalization of Glassy Nanostring Resonator Arrays.

PubMed

Zheng, Wei; Du, Rongbing; Cao, Yong; Mohammad, Mohammad A; Dew, Steven K; McDermott, Mark T; Evoy, Stephane

2015-07-30

Resonant glassy nanostrings have been employed for the detection of biomolecules. These devices offer high sensitivity and amenability to large array integration and multiplexed assays. Such a concept has however been impaired by the lack of stable and biocompatible linker chemistries. Diazonium salt reduction-induced aryl grafting is an aqueous-based process providing strong chemical adhesion. In this work, diazonium-based linker chemistry was performed for the first time on glassy nanostrings, which enabled the bio-functionalization of such devices. Large arrays of nanostrings with ultra-narrow widths down to 10 nm were fabricated employing electron beam lithography. Diazonium modification was first developed on SiCN surfaces and validated by X-ray photoelectron spectroscopy. Similarly modified nanostrings were then covalently functionalized with anti-rabbit IgG as a molecular probe. Specific enumeration of rabbit IgG was successfully performed through observation of downshifts of resonant frequencies. The specificity of this enumeration was confirmed through proper negative control experiments. Helium ion microscopy further verified the successful functionalization of nanostrings.

Synergistic effect in carbon coated LiFePO4 for high yield spontaneous grafting of diazonium salt. Structural examination at the grain agglomerate scale.

PubMed

Madec, Lénaïc; Robert, Donatien; Moreau, Philippe; Bayle-Guillemaud, Pascale; Guyomard, Dominique; Gaubicher, Joël

2013-08-07

Molecular grafting of p-nitrobenzene diazonium salt at the surface of (Li)FePO4-based materials was thoroughly investigated. The grafting yields obtained by FTIR, XPS, and elemental analysis for core shell LiFePO4-C are found to be much higher than the sum of those associated with either the LiFePO4 core or the carbon shell alone, thereby revealing a synergistic effect. Electrochemical, XRD, and EELS experiments demonstrate that this effect stems from the strong participation of the LiFePO4 core that delivers large amounts of electrons to the carbon substrate at a constant energy, above the Fermi level of the diazonium salt. Correspondingly large multilayer anisotropic structures that are associated with outstanding grafting yields could be observed from TEM experiments. Results therefore constitute strong evidence of a grafting mechanism where homolytic cleavage of the N2(+) species occurs together with the formation and grafting of radical nitro-aryl intermediates. Although the oxidation and concomitant Li deintercalation of LiFePO4 grains constitute the main driving force of the functionalization reaction, EFTEM EELS mapping shows a striking lack of spatial correlation between grafted grains and oxidized ones.

Flexible strategy for immobilizing redox-active compounds using in situ generation of diazonium salts. Investigations of the blocking and catalytic properties of the layers.

PubMed

Noël, Jean-Marc; Sjöberg, Béatrice; Marsac, Rémi; Zigah, Dodzi; Bergamini, Jean-François; Wang, Aifang; Rigaut, Stéphane; Hapiot, Philippe; Lagrost, Corinne

2009-11-03

A versatile two-step method is developed to covalently immobilize redox-active molecules onto carbon surfaces. First, a robust anchoring platform is grafted onto surfaces by electrochemical reduction of aryl diazonium salts in situ generated. Depending on the nature of the layer termini, -COOH or -NH(2), a further chemical coupling involving ferrocenemethylamine or ferrocene carboxylic acid derivatives leads to the covalent binding of ferrocene centers. The chemical strategy using acyl chloride activation is efficient and flexible, since it can be applied either to surface-reactive end groups or to reactive species in solution. Cyclic voltammetry analyses point to the covalent binding of ferrocene units restricted to the upper layers of the underlying aryl films, while AFM measurements show a lost of compactness of the layers after the chemical attachment of ferrocene centers. The preparation conditions of the anchoring layers were found to determine the interfacial properties of the resulted ferrocenyl-modified electrodes. The ferrocene units promoted effective redox mediation providing that the free redox probes are adequately chosen (i.e., vs size/formal potential) and the underlying layers exhibit strong blocking properties. For anchoring films with weaker blocking effect, the coexistence of two distinct phenomena, redox mediation and ET at pinholes could be evidenced.

Hydroxynaphthoquinone ultrathin films obtained by diazonium electroreduction: toward design of biosensitive electroactive interfaces.

PubMed

March, Gregory; Reisberg, Steeve; Piro, Benoit; Pham, Minh-Chau; Fave, Claire; Noel, Vincent

2010-05-01

Electroactive 2-(phenylsulfanyl)-8-hydroxy-1,4-naphthoquinone has been electrodeposited via the reduction of the corresponding diazonium salt on Au electrodes. Surface characterizations by X-ray photoelectron spectroscopy (XPS) and infrared reflection-absorption spectroscopy (IRRAS) reveal that the mechanism of film deposition follows an aryl radical formation and its immobilization on the electrode surface. Electrochemical study shows that the surface coverage can be finely tuned (thickness between one and four layers) by adjusting the potential and the deposition time. By managing the potential applied when reducing diazonium in potentiostatic mode, the formed layer could mediate or not charge transfer. This is the first time that the films obtained by diazonium process are demonstrated to act as mediators in the growth process. Hence, with potentials higher than the formal potential of quinone group, very thin and homogeneous layers are obtained, whereas thicker films are formed when more cathodic potentials than that of quinone are applied. The possibility to manage the charge-transfer kinetics, the thickness, and the homogeneity of electroactive deposits is interesting in the scope of designing electrochemical transducers.

Protein-functionalized hairy diamond nanoparticles.

PubMed

Dahoumane, Si Amar; Nguyen, Minh Ngoc; Thorel, Alain; Boudou, Jean-Paul; Chehimi, Mohamed M; Mangeney, Claire

2009-09-01

Diazonium salt chemistry and atom transfer radical polymerization (ATRP) were combined in view of preparing new bioactive hairy diamond nanoparticles containing, or potentially containing, nitrogen-vacancy (NV) fluorescent centers (fluorescent nanodiamonds, or fNDs). fNDs were modified by ATRP initiators using the electroless reduction of the diazonium salt BF(4)(-),(+)N(2)-C(6)H(4)-CH(CH(3))-Br. The strongly bound aryl groups -C(6)H(4)-CH(CH(3))-Br efficiently initiated the ATRP of tert-butyl methacrylate (tBMA) at the surface of the nanodiamonds, which resulted in obtaining ND-PtBMA hybrids. The grafted chain thickness, estimated from X-ray photoelectron spectroscopy (XPS), was found to increase linearly with respect to time before reaching a plateau value of ca. 2 nm. These nanoobjects were further hydrolyzed into ND-PMAA (where PMAA is the poly(methacrylic acid) graft) and further decorated by bovine serum albumin through the 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide (EDC/NHS) coupling procedure.

Graphite anode surface modification with controlled reduction of specific aryl diazonium salts for improved microbial fuel cells power output.

PubMed

Picot, Matthieu; Lapinsonnière, Laure; Rothballer, Michael; Barrière, Frédéric

2011-10-15

Graphite electrodes were modified with reduction of aryl diazonium salts and implemented as anodes in microbial fuel cells. First, reduction of 4-aminophenyl diazonium is considered using increased coulombic charge density from 16.5 to 200 mC/cm(2). This procedure introduced aryl amine functionalities at the surface which are neutral at neutral pH. These electrodes were implemented as anodes in "H" type microbial fuel cells inoculated with waste water, acetate as the substrate and using ferricyanide reduction at the cathode and a 1000 Ω external resistance. When the microbial anode had developed, the performances of the microbial fuel cells were measured under acetate saturation conditions and compared with those of control microbial fuel cells having an unmodified graphite anode. We found that the maximum power density of microbial fuel cell first increased as a function of the extent of modification, reaching an optimum after which it decreased for higher degree of surface modification, becoming even less performing than the control microbial fuel cell. Then, the effect of the introduction of charged groups at the surface was investigated at a low degree of surface modification. It was found that negatively charged groups at the surface (carboxylate) decreased microbial fuel cell power output while the introduction of positively charged groups doubled the power output. Scanning electron microscopy revealed that the microbial anode modified with positively charged groups was covered by a dense and homogeneous biofilm. Fluorescence in situ hybridization analyses showed that this biofilm consisted to a large extent of bacteria from the known electroactive Geobacter genus. In summary, the extent of modification of the anode was found to be critical for the microbial fuel cell performance. The nature of the chemical group introduced at the electrode surface was also found to significantly affect the performance of the microbial fuel cells. The method used for modification is easy to control and can be optimized and implemented for many carbon materials currently used in microbial fuel cells and other bioelectrochemical systems. Copyright © 2011 Elsevier B.V. All rights reserved.

Covalent functionalization and passivation of exfoliated black phosphorus via aryl diazonium chemistry.

PubMed

Ryder, Christopher R; Wood, Joshua D; Wells, Spencer A; Yang, Yang; Jariwala, Deep; Marks, Tobin J; Schatz, George C; Hersam, Mark C

2016-06-01

Functionalization of atomically thin nanomaterials enables the tailoring of their chemical, optical and electronic properties. Exfoliated black phosphorus (BP)-a layered two-dimensional semiconductor-exhibits favourable charge-carrier mobility, tunable bandgap and highly anisotropic properties, but it is chemically reactive and degrades rapidly in ambient conditions. Here we show that covalent aryl diazonium functionalization suppresses the chemical degradation of exfoliated BP even after three weeks of ambient exposure. This chemical modification scheme spontaneously forms phosphorus-carbon bonds, has a reaction rate sensitive to the aryl diazonium substituent and alters the electronic properties of exfoliated BP, ultimately yielding a strong, tunable p-type doping that simultaneously improves the field-effect transistor mobility and on/off current ratio. This chemical functionalization pathway controllably modifies the properties of exfoliated BP, and thus improves its prospects for nanoelectronic applications.

Carboxyl functionalization of carbon fibers via aryl diazonium reaction in molten urea to enhance interfacial shear strength

NASA Astrophysics Data System (ADS)

Wang, Yuwei; Meng, Linghui; Fan, Liquan; Wu, Guangshun; Ma, Lichun; Zhao, Min; Huang, Yudong

2016-01-01

Using molten urea as the solvent, carbon fibers were functionalized with carboxylic acid groups via aryl diazonium reaction in 15 min to improve their interfacial bonding with epoxy resin. The surface functionalization was quantified by X-ray photoelectron spectroscopy, which showed that the relative surface coverage of carboxylic acid groups increased from an initial percentage of 3.17-10.41%. Mechanical property test results indicated that the aryl diazonium reaction in this paper could improve the interfacial shear strength by 66%. Meanwhile, the technique did not adopt any pre-oxidation step to produce functional groups prior to grafting and was shown to maintain the tensile strength of the fibers. This methodology provided a rapid, facile and economically viable route to produce covalently functionalized carbon fibers in large quantities with an eco-friendly method.

Covalent functionalization and passivation of exfoliated black phosphorus via aryl diazonium chemistry

NASA Astrophysics Data System (ADS)

Ryder, Christopher R.; Wood, Joshua D.; Wells, Spencer A.; Yang, Yang; Jariwala, Deep; Marks, Tobin J.; Schatz, George C.; Hersam, Mark C.

2016-06-01

Functionalization of atomically thin nanomaterials enables the tailoring of their chemical, optical and electronic properties. Exfoliated black phosphorus (BP)—a layered two-dimensional semiconductor—exhibits favourable charge-carrier mobility, tunable bandgap and highly anisotropic properties, but it is chemically reactive and degrades rapidly in ambient conditions. Here we show that covalent aryl diazonium functionalization suppresses the chemical degradation of exfoliated BP even after three weeks of ambient exposure. This chemical modification scheme spontaneously forms phosphorus-carbon bonds, has a reaction rate sensitive to the aryl diazonium substituent and alters the electronic properties of exfoliated BP, ultimately yielding a strong, tunable p-type doping that simultaneously improves the field-effect transistor mobility and on/off current ratio. This chemical functionalization pathway controllably modifies the properties of exfoliated BP, and thus improves its prospects for nanoelectronic applications.

Photobleachable Diazonium Salt-Phenolic Resin Two-Layer Resist System

NASA Astrophysics Data System (ADS)

Uchino, Shou-ichi; Iwayanagi, Takao; Hashimoto, Michiaki

1988-01-01

This article describes a new negative two-layer photoresist system formed by a simple, successive spin-coating method. An aqueous acetic acid solution of diazonium salt and poly(N-vinylpyrrolidone) is deposited so as to contact a phenolic resin film spin-coated on a silicon wafer. The diazonium salt diffuses into the phenolic resin layer after standing for several minutes. The residual solution on the phenolic resin film doped with diazonium salt is spun to form the diazonium salt-poly(N-vinylpyrrolidone) top layer. This forms a uniform two-layer resist without phase separation or striation. Upon UV exposure, the diazonium salt in the top layer bleaches to act as a CEL dye, while the diazonium salt in the bottom layer decomposes to cause insolubilization. Half μm line-and-space patterns are obtained with an i-line stepper using 4-diazo-N,N-dimethylaniline chloride zinc chloride double salt as the diazonium salt and a cresol novolac resin for the bottom polymer layer. The resist formation processes, insolubilization mechanism, and the resolution capability of the new two-layer resist are discussed.

SiGe derivatization by spontaneous reduction of aryl diazonium salts

NASA Astrophysics Data System (ADS)

Girard, A.; Geneste, F.; Coulon, N.; Cardinaud, C.; Mohammed-Brahim, T.

2013-10-01

Germanium semiconductors have interesting properties for FET-based biosensor applications since they possess high surface roughness allowing the immobilization of a high amount of receptors on a small surface area. Since SiGe combined low cost of Si and intrinsic properties of Ge with high mobility carriers, we focused the study on this particularly interesting material. The comparison of the efficiency of a functionalization process involving the spontaneous reduction of diazonium salts is studied on Si(1 0 0), SiGe and Ge semiconductors. XPS analysis of the functionalized surfaces reveals the presence of a covalent grafted layer on all the substrates that was confirmed by AFM. Interestingly, the modified Ge derivatives have still higher surface roughness after derivatization. To support the estimated thickness by XPS, a step measurement of the organic layers is done by AFM or by profilometer technique after a O2 plasma etching of the functionalized layer. This original method is well-adapted to measure the thickness of thin organic films on rough substrates such as germanium. The analyses show a higher chemical grafting on SiGe substrates compared with Si and Ge semiconductors.

Chameleonic reactivity of vicinal diazonium salt of acetylenyl-9,10-anthraquinones: synthetic application toward two heterocyclic targets.

PubMed

Stepanov, A A; Gornostaev, L M; Vasilevsky, S F; Arnold, E V; Mamatyuk, V I; Fadeev, D S; Gold, B; Alabugin, I V

2011-11-04

The nature of products in the diazotization of 1-amino-2-acetylenyl-9,10-anthraquinones strongly depends on the nature of substituents at both the alkyne and at the anthraquinone core. Donor substitution (NHAr, OH) at the fourth position stabilizes the diazonium salt at C1, decelerating electrophilic cyclization at the arylethynyl substituent at C2. This effect allows the replacement of the diazonium with azide group and subsequent closure into isoxazole ring with preservation of the alkyne. In contrast, electrophilic 5-exo-dig cyclizations to condensed pyrazoles is observed for the combination of donor substituents at the aryl alkyne moiety and an OAc substituent at C4. The latter process provides a new synthetic route to 3-ethynyl-[1,9-cd]isoxazol-6-ones that are difficult to access otherwise. DFT calculations suggest that donor substituents have only a minor effect on alkyne and diazonium polarization in the reactant but provide specific transition state stabilization by stabilizing the incipient vinyl cation. This analysis provides the first computational data on electrophilic 5-exo-dig cyclization in its parent form and the nucleophile-promoted version. This cyclization is a relatively fast but endothermic process that is rendered thermodynamically feasible by the enol-keto tautomerization with concomitant aromatization in the five-membered heteroaromatic ring. Computations suggest that the importance of nucleophilic assistance in the transition state for a relatively weak nucleophile such as water is minor because the energy gain due to the Lewis base coordination to the carbocationic center is more than compensated for by the unfavorable entropic term for the bimolecular proces.

Chemically functionalized two-dimensional titanium carbide MXene by in situ grafting-intercalating with diazonium ions to enhance supercapacitive performance

NASA Astrophysics Data System (ADS)

Wang, Hongbing; Zhang, Jianfeng; Wu, Yuping; Huang, Huajie; Jiang, Quanguo

2018-04-01

Two-dimensional Ti3C2 MXene nanosheets were functionalized with phenylsulfonic groups derived from in situ generated diazonium ions by the corresponding amine. During the functionalization process, the aryl groups were attached onto the MXene surfaces in the form of strong MXene-aryl (Tisbnd Osbnd C) linkages. Simultaneously, the intercalation of diazonium ions enabled Ti3C2 multi-layers to be delaminated into separate few-layer nanosheets via weak sonication with low energy. As a result of chemical functionalization for MXene Ti3C2, the dispersibility was greatly improved and the specific surface area increased significantly. The grafted functional groups are still stable up to at least 200 °C upon thermogravimetric analysis measurements. With diazonium ions intercalating and electroactive groups grafting between-in MXene layers, the chemically functionalized Ti3C2 electrodes exhibited an enhanced supercapacitive performance, which acquired a specific capacitance more than double that of pristine Ti3C2 samples and excellent cycling stability (91% capacity retention after 10,000 cycles at 3 A g-1). This feasible modification scheme can be also extended to functionalize other types of MXenes materials with this or other aryl diazonium ions as surface modifiers and intercalants, thus offering scope for full potential applications of the new 2D materials.

Synthesis and application of a triazene-ferrocene modifier for immobilization and characterization of oligonucleotides at electrodes.

PubMed

Hansen, Majken N; Farjami, Elaheh; Kristiansen, Martin; Clima, Lilia; Pedersen, Steen Uttrup; Daasbjerg, Kim; Ferapontova, Elena E; Gothelf, Kurt V

2010-04-16

A new DNA modifier containing triazene, ferrocene, and activated ester functionalities was synthesized and applied for electrochemical grafting and characterization of DNA at glassy carbon (GC) and gold electrodes. The modifier was synthesized from ferrocenecarboxylic acid by attaching a phenyltriazene derivative to one of the ferrocene Cp rings, while the other Cp ring containing the carboxylic acid was converted to an activated ester. The modifier was conjugated to an amine-modified DNA sequence. For immobilization of the conjugate at Au or GC electrodes, the triazene was activated by dimethyl sulfate for release of the diazonium salt. The salt was reductively converted to the aryl radical which was readily immobilized at the surface. DNA grafted onto electrodes exhibited remarkable hybridization properties, as detected through a reversible shift in the redox potential of the Fc redox label upon repeated hybridization/denaturation procedures with a complementary target DNA sequence. By using a methylene blue (MB) labeled target DNA sequence the hybridization could also be followed through the MB redox potential. Electrochemical studies demonstrated that grafting through the triazene modifier can successfully compete with existing protocols for DNA immobilization through the commonly used alkanethiol linkers and diazonium salts. Furthermore, the triazene modifier provides a practical one-step immobilization procedure.

Spatially selective modification of PLLA surface: From hydrophobic to hydrophilic or to repellent

NASA Astrophysics Data System (ADS)

Bastekova, Kristina; Guselnikova, Olga; Postnikov, Pavel; Elashnikov, Roman; Kunes, Martin; Kolska, Zdenka; Švorčík, Vaclav; Lyutakov, Oleksiy

2017-03-01

A universal approach to controlled surface modification of polylactic acid (PLLA) films using diazonium chemistry was proposed. The multistep procedure includes surface activation of PLLA by argon plasma treatment and chemical activation of arenediazonium tosylates by NaBH4. The surface of PLLA film was grafted with different functional organic groups (OFGs), changing the PLLA surface properties (wettability, morphology, zeta potential, chemical composition, and mechanical response). Three approaches of OFG grafting were examined: (i) plasma treatment following by PLLA immersion into diazonium salt aqueous solution; (ii) grafting of PLLA surface through the reaction with chemically created aryl radicals; (iii) mutual combination of both methods The best results were achieved in the last case, where the previous plasma treatment was combined with further reaction of PLLA surface with generated aryl radicals. Using this method PLLA surface was successfully grafted with amino, carboxyl, aliphatic and fluorinated OFGs. Further investigation of surface properties from potential biological and medical points of view was performed using zeta potential, biodegradation and biofouling tests. It was shown that proposed technique allows preparation of biorepellent or bioabsorptive surfaces, tuning of PLLA biodegradation rate and nanomechanical properties, as well as the introduction of inverse properties (such as hydrophilic and hydrophobic) on both sides of PLLA films.

Photochemical and radiation-chemical aspects of matrix acidity effects on some organic systems

NASA Astrophysics Data System (ADS)

Ambroz, H. B.; Przybytniak, G. K.; Wronska, T.; Kemp, T. J.

The role of matrix effects in radiolysis and photolysis is illustrated using two systems: organosulphur compounds and benzenediazonium salts. Their intermediates as detected by low temperature ESR and optical spectroscopy or FAB-MS give evidence that the main reaction pathways depend strongly on these effects. Changes in matrix acidity can control the formation of neutral radical, ion-radical or ionic species which are crucial to the character of the final products of irradiation of organosulphur compounds, which are of great importance in medicine, biology, ecology and industry. Microenvironmental influences determine whether the triplet aryl cation or radical species are detected as the principal or sole intermediates in the decomposition of diazonium salts, a process leading to different stable products with industrial application.

Clay/Polyaniline Hybrid through Diazonium Chemistry: Conductive Nanofiller with Unusual Effects on Interfacial Properties of Epoxy Nanocomposites.

PubMed

Jlassi, Khouloud; Chandran, Sarath; Poothanari, Mohammed A; Benna-Zayani, Mémia; Thomas, Sabu; Chehimi, Mohamed M

2016-04-12

The concept of conductive network structure in thermoset matrix without sacrificing the inherent mechanical properties of thermoset polymer (e.g., epoxy) is investigated here using "hairy" bentonite fillers. The latter were prepared through the in situ polymerization of aniline in the presence of 4-diphenylamine diazonium (DPA)-modified bentonite (B-DPA) resulting in a highly exfoliated bentonite-DPA/polyaniline (B-DPA/PANI). The nanocomposite filler was mixed with diglycidyl ether of bisphenol A (DGEBA), and the curing agent (4,4'-diaminodiphenylsulfone) (DDS) at high temperature in order to obtain nanocomposites through the conventional melt mixing technique. The role of B-DPA in the modification of the interface between epoxy and B-DPA/polyaniline (B-DPA/PANI) is investigated and compared with the filler B/PANI prepared without any diazonium modification of the bentonite. Synergistic improvement in dielectric properties and mechanical properties points to the fact that the DPA aryl groups from the diazonium precursor significantly modify the interface by acting as an efficient stress transfer medium. In DPA-containing nanocomposites, unique fibril formation was observed on the fracture surface. Moreover, dramatic improvement (210-220%) in fracture toughness of epoxy composite was obtained with B-DPA/PANI filler as compared to the weak improvement of 20-30% noted in the case of the B/PANI filler. This work shows that the DPA diazonium salt has an important effect on the improvement of the interfacial properties and adhesion of DGEBA and clay/PANI nanofillers.

Grafting the sol-gel based sorbents by diazonium salts: a novel approach toward unbreakable capillary microextraction.

PubMed

Bagheri, Habib; Bayat, Parisa; Piri-Moghadam, Hamed

2013-11-29

The present work deals with a novel approach for grafting a sol-gel based sorbent, using diazonium salts for preparation of an unbreakable capillary microextraction (CME) device in on-line combination with high performance liquid chromatography (HPLC). The use of diazonium salts modifier allowed all types of metallic and non-metallic substrates to be used without any limitation. Substrates including copper, brass, stainless steel and polytetrafluoroethylene (PTFE) were chosen to be functionalized by chemical or electrochemical reduction of 4-amino phenyl acetic acid. Then, 3-(trimethoxysilyl)propylamine (3TMSPA) was selected as the precursor and the only reagent for preparation of the desired surface chemical bonded sorbent. The presence of chemical bond between substrate, diazonium salts and 3TMSPA is more probably responsible for thermal and solvent stability and long lifetime of the prepared sorbent. Characterization of the aryl group formation on the various substrates along with the prepared sorbents was thoroughly investigated by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and thermogravimetry analysis (TGA). Typically, one of the prepared sorbents, deposited on the inner surface of the copper tube, was selected for assessing the developed method. The CME device was used for on-line extraction of atrazine, ametryn and terbutryn, as model compounds, from the aquatic media. After extraction, the HPLC mobile phase was used for on-line desorption and elution of the extracted analytes from the CME loop, containing the grafted sol-gel based sorbent, through the HPLC column. Figures of merit of the developed method were also obtained in which the linearity for the analytes was in the range of 30-1000μgL(-1). The value of LOD (S/N=3) for all analytes was 10μgL(-1) and the RSD% values (n=5) were all below 9.4% at the 500μgL(-1) level. Applicability of the developed method was examined by analyzing some real water samples in which the relative recovery percentage ranged from 75 to 95%. Copyright © 2013 Elsevier B.V. All rights reserved.

Penicillamine-modified sensor for the voltammetric determination of Cd(II) and Pb(II) ions in natural samples.

PubMed

Pérez-Ràfols, Clara; Serrano, Núria; Díaz-Cruz, José Manuel; Ariño, Cristina; Esteban, Miquel

2015-11-01

A new penicillamine-GCE was developed based on the immobilization of d-penicillamine on aryl diazonium salt monolayers anchored to the glassy carbon electrode (GCE) surface and it was applied for the first time to the simultaneous determination of Cd(II) and Pb(II) ions by stripping voltammetric techniques. The detection and quantification limits at levels of µg L(-1) suggest that the penicillamine-GCE could be fully suitable for the determination of the considered ions in natural samples. Copyright © 2015 Elsevier B.V. All rights reserved.

Synthesis, spectral characterization and in vitro antimicrobial activity of some new azopyridine derivatives

NASA Astrophysics Data System (ADS)

Abuo-Melha, Hanaa; Fadda, A. A.

2012-04-01

A series of arylpicolino and/or isonicotinohydrazonyl cyanide 2a-d and 4a-f were prepared by coupling the approprite aryl diazonium salt with 2-cyanomethyl and/or 4-cyanomethyl-pyridine, respectively. These compounds were characterized by analytical and spectral analyses and screened for their antibacterial activity against Gram-positive bacteria, Gram-negative bacteria and antifungal activity. Among the synthesized compounds, N'-(4-phenyldiazenyl)phenylisonicotinohydrazonyl cyanide 4f showed a significant activity toward both Gram-positive, Gram-negative bacteria and exhibit the most potent in vitro antifungal with MIC's (625 μg/mL) against Aspergillus nieger.

Scope and limitations of the Heck-Matsuda-coupling of phenol diazonium salts and styrenes: a protecting-group economic synthesis of phenolic stilbenes.

PubMed

Schmidt, Bernd; Elizarov, Nelli; Berger, René; Hölter, Frank

2013-06-14

4-Phenol diazonium salts undergo Pd-catalyzed Heck reactions with various styrenes to 4'-hydroxy stilbenes. In almost all cases higher yields and fewer side products were observed, compared to the analogous 4-methoxy benzene diazonium salts. In contrast, the reaction fails completely with 2- and 3-phenol diazonium salts. For these substitution patterns the methoxy-substituted derivatives are superior.

Electrochemical impedance immunosensor based on gold nanoparticles and aryl diazonium salt functionalized gold electrodes for the detection of antibody.

PubMed

Liu, Guozhen; Liu, Jingquan; Davis, Thomas P; Gooding, J Justin

2011-04-15

Electrodes modified with passivating organic layers have been shown to, here and previously, to exhibit good Faradaic electrochemistry upon attachment of gold nanoparticles (AuNP). Due to their low background capacitances these constructs have good potential in electrochemical sensing. Herein is reported the application of these electrode constructs for impedance based immunosensing. The immunosensor was constructed by modifying a gold electrode with 4-thiophenol (4-TP) passivating layers by diazonium salt chemistry. Subsequently, the attachment of AuNP and then a biotin derivative as a model epitope to detect anti-biotin IgG were carried out. The interfacial properties of the modified electrodes were evaluated in the presence of Fe(CN)(6)(4-/3-) redox couple as a probe by cyclic voltammetry and electrochemical impedance spectroscopy. The impedance change, due to the specific immuno-interaction at the immunosensor surface was utilized to detect anti-biotin IgG. The increase in charge-transfer resistance (R(ct)) was linearly proportional to the concentration of anti-biotin IgG in the range of 5-500 ng mL(-1), with a detection limit of 5 ng mL(-1). Copyright © 2011 Elsevier B.V. All rights reserved.

An electrochemical immunosensor for brain natriuretic peptide prepared with screen-printed carbon electrodes nanostructured with gold nanoparticles grafted through aryl diazonium salt chemistry.

PubMed

Serafín, V; Torrente-Rodríguez, R M; González-Cortés, A; García de Frutos, P; Sabaté, M; Campuzano, S; Yáñez-Sedeño, P; Pingarrón, J M

2018-03-01

A sensitive amperometric immunosensor has been prepared by immobilization of capture antibodies onto gold nanoparticles (AuNPs) grafted on a screen-printed carbon electrode (SPCE) through aryl diazonium salt chemistry using 4-aminothiophenol (AuNPs-S-Phe-SPCE). The immunosensor was designed for the accurate determination of clinically relevant levels of B-type natriuretic peptide (BNP) in human serum samples. The nanostructured electrochemical platform resulted in an ordered layer of AuNPs onto SPCEs which combined the advantages of high conductivity and improved stability of immobilized biomolecules. The resulting disposable immunosensor used a sandwich type immunoassay involving a peroxidase-labeled detector antibody. The amperometric transduction was carried out at -0.20V (vs the Ag pseudo-reference electrode) upon the addition of hydroquinone (HQ) as electron transfer mediator and H 2 O 2 as the enzyme substrate. The nanostructured immunosensors show a storage stability of at least 25 days, a linear range between 0.014 and 15ngmL -1 , and a LOD of 4pgmL -1 , which is 100 times lower than the established cut-off value for heart failure (HF) diagnosis. The performance of the immunosensor is advantageously compared with that provided with immunosensors prepared by grafting SPCE with p-phenylendiamine (H 2 N-Phe-SPCE) and attaching AuNPs by immersion into an AuNPs suspension or by electrochemical deposition, as well as with immunosensors constructed using commercial AuNPs-modified SPCEs. The developed immunosensor was applied to the successful analysis of human serum from heart failure (HF) patients upon just a 10-times dilution as sample treatment. Copyright © 2017 Elsevier B.V. All rights reserved.

Electronic structure and optical spectra of semiconducting carbon nanotubes functionalized by diazonium salts

NASA Astrophysics Data System (ADS)

Ramirez, Jessica; Mayo, Michael L.; Kilina, Svetlana; Tretiak, Sergei

2013-02-01

We report density functional (DFT) calculations on finite-length semiconducting carbon nanotubes covalently and non-covalently functionalized by aryl diazonium moieties and their chlorinated derivatives. For these systems, we investigate (i) an accuracy of different functionals and basis sets, (ii) a solvent effect, and (iii) the impact of the chemical functionalization on optical properties of nanotubes. In contrast to B3LYP, only long-range-corrected functionals, such as CAM-B3LYP and wB97XD, properly describe the ground and excited state properties of physisorbed molecules. We found that physisorbed cation insignificantly perturbs the optical spectra of nanotubes. In contrast, covalently bound complexes demonstrate strong redshifts and brightening of the lowest exciton that is optically dark in pristine nanotubes. However, the energy and oscillator strength of the lowest state are dictated by the position of the molecule on the nanotube. Thus, if controllable and selective chemical functionalization is realized, the PL of nanotubes could be improved.

Atomically-thin molecular layers for electrode modification of organic transistors

NASA Astrophysics Data System (ADS)

Gim, Yuseong; Kang, Boseok; Kim, Bongsoo; Kim, Sun-Guk; Lee, Joong-Hee; Cho, Kilwon; Ku, Bon-Cheol; Cho, Jeong Ho

2015-08-01

Atomically-thin molecular layers of aryl-functionalized graphene oxides (GOs) were used to modify the surface characteristics of source-drain electrodes to improve the performances of organic field-effect transistor (OFET) devices. The GOs were functionalized with various aryl diazonium salts, including 4-nitroaniline, 4-fluoroaniline, or 4-methoxyaniline, to produce several types of GOs with different surface functional groups (NO2-Ph-GO, F-Ph-GO, or CH3O-Ph-GO, respectively). The deposition of aryl-functionalized GOs or their reduced derivatives onto metal electrode surfaces dramatically enhanced the electrical performances of both p-type and n-type OFETs relative to the performances of OFETs prepared without the GO modification layer. Among the functionalized rGOs, CH3O-Ph-rGO yielded the highest hole mobility of 0.55 cm2 V-1 s-1 and electron mobility of 0.17 cm2 V-1 s-1 in p-type and n-type FETs, respectively. Two governing factors: (1) the work function of the modified electrodes and (2) the crystalline microstructures of the benchmark semiconductors grown on the modified electrode surface were systematically investigated to reveal the origin of the performance improvements. Our simple, inexpensive, and scalable electrode modification technique provides a significant step toward optimizing the device performance by engineering the semiconductor-electrode interfaces in OFETs.Atomically-thin molecular layers of aryl-functionalized graphene oxides (GOs) were used to modify the surface characteristics of source-drain electrodes to improve the performances of organic field-effect transistor (OFET) devices. The GOs were functionalized with various aryl diazonium salts, including 4-nitroaniline, 4-fluoroaniline, or 4-methoxyaniline, to produce several types of GOs with different surface functional groups (NO2-Ph-GO, F-Ph-GO, or CH3O-Ph-GO, respectively). The deposition of aryl-functionalized GOs or their reduced derivatives onto metal electrode surfaces dramatically enhanced the electrical performances of both p-type and n-type OFETs relative to the performances of OFETs prepared without the GO modification layer. Among the functionalized rGOs, CH3O-Ph-rGO yielded the highest hole mobility of 0.55 cm2 V-1 s-1 and electron mobility of 0.17 cm2 V-1 s-1 in p-type and n-type FETs, respectively. Two governing factors: (1) the work function of the modified electrodes and (2) the crystalline microstructures of the benchmark semiconductors grown on the modified electrode surface were systematically investigated to reveal the origin of the performance improvements. Our simple, inexpensive, and scalable electrode modification technique provides a significant step toward optimizing the device performance by engineering the semiconductor-electrode interfaces in OFETs. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr03307a

Covalent electron transfer chemistry of graphene with diazonium salts.

PubMed

Paulus, Geraldine L C; Wang, Qing Hua; Strano, Michael S

2013-01-15

Graphene is an atomically thin, two-dimensional allotrope of carbon with exceptionally high carrier mobilities, thermal conductivity, and mechanical strength. From a chemist's perspective, graphene can be regarded as a large polycyclic aromatic molecule and as a surface without a bulk contribution. Consequently, chemistries typically performed on organic molecules and surfaces have been used as starting points for the chemical functionalization of graphene. The motivations for chemical modification of graphene include changing its doping level, opening an electronic band gap, charge storage, chemical and biological sensing, making new composite materials, and the scale-up of solution-processable graphene. In this Account, we focus on graphene functionalization via electron transfer chemistries, in particular via reactions with aryl diazonium salts. Because electron transfer chemistries depend on the Fermi energy of graphene and the density of states of the reagents, the resulting reaction rate depends on the number of graphene layers, edge states, defects, atomic structure, and the electrostatic environment. We limit our Account to focus on pristine graphene over graphene oxide, because free electrons in the latter are already bound to oxygen-containing functionalities and the resulting chemistries are dominated by localized reactivity and defects. We describe the reaction mechanism of diazonium functionalization of graphene and show that the reaction conditions determine the relative degrees of chemisorption and physisorption, which allows for controlled modulation of the electronic properties of graphene. Finally we discuss different applications for graphene modified by this chemistry, including as an additive in polymer matrices, as biosensors when coupled with cells and biomolecules, and as catalysts when combined with nanoparticles.

On-off QD switch that memorizes past recovery from quenching by diazonium salts.

PubMed

Liras, Marta; González-Béjar, María; Scaiano, J C

2010-09-07

The understanding of the interaction of CdSe/ZnS semiconductor quantum dots (QD) with their chemical environment is fundamental, yet far from being fully understood. p-Methylphenyldiazonium tetrafluoroborate has been used to get some insight into the effect of diazonium salts on the spectroscopy of QD. Our study reveals that the surface of CdSe/ZnS quantum dots can be modified by diazonium salts (although not functionalized), showing and on-off fluorescence behaviour that memorizes past quenching recoveries. Facile modification of the surface confers protection against quenching by new molecules of diazonium salt and other known quenchers such as 4-amino-TEMPO. The reaction mechanism has been explored in detail by using different spectroscopic techniques. At the first time after addition of diazonium salt over QD the fluorescent is turned off with Stern-Volmer behaviour; the fluorescence recovers following irradiation. Subsequent additions of diazonium salts do not cause the same degree of quenching. We have noted that the third addition (following two cycles of addition and irradiation) is unable to quench the fluorescence. Monitoring the process using NMR techniques reveals the formation of p-difluoroborane toluene as a result of the irradiation of diazonium-treated QD; the treatment leads to the fluorination of the QD surface.

Functionalization of graphene nanoribbons

NASA Astrophysics Data System (ADS)

Genorio, Bostjan; Znidarsic, Andrej

2014-03-01

Graphene nanoribbon (GNR) is a recently discovered carbon allotrope, which can be described as a stripe of graphene. Pseudo-one-dimensionality exerts additional confinement on the electrons resulting in the formation of a band gap relevant for electronic devices. Due to distinct physical and chemical properties it is a promising material for several applications. To expand the range of potential applications and to improve processability, chemical functionalization of GNRs is required. This review aims to provide a concise and systematic coverage of recent work in chemical functionalization of GNRs. We will focus on longitudinal carbon nanotube unzipping, functionalization with aryl diazonium salts, non-covalent functionalization, bottom-up synthesis and one pot carbon nanotube unzipping with in situ edge functionalization.

Exploring Flow Procedures for Diazonium Formation.

PubMed

Hu, Te; Baxendale, Ian R; Baumann, Marcus

2016-07-14

The synthesis of diazonium salts is historically an important transformation extensively utilized in dye manufacture. However the highly reactive nature of the diazonium functionality has additionally led to the development of many new reactions including several carbon-carbon bond forming processes. It is therefore highly desirable to determine optimum conditions for the formation of diazonium compounds utilizing the latest processing tools such as flow chemistry to take advantage of the increased safety and continuous manufacturing capabilities. Herein we report a series of flow-based procedures to prepare diazonium salts for subsequent in-situ consumption.

Facile synthesis of electrophilic vinyl boranes: reactions of alkynyl-borates and diazonium salts.

PubMed

Zhao, Xiaoxi; Liang, Liyuan; Stephan, Douglas W

2012-10-21

Reactions of alkynylborate salts, easily derived from reaction of frustrated Lewis pairs with terminal alkynes, with diazonium salts to induce 1,1-carboboration affording a facile and efficient route to substituted electrophilic vinyl boranes.

Spontaneous Aryldiazonium Film Formation on 440C Stainless Steel in Nonaqueous Environments

DOE PAGES

Small, Leo J.; Hibbs, Michael R.; Wheeler, David R.

2014-11-07

The ability of three aryldiazonium salts to spontaneously assemble onto the surface of type 440C stainless steel is investigated in acetonitrile and the model hydraulic fluids tributyl phosphate and hexamethyldisiloxane. Competition between native oxide growth and organic film growth at different diazonium salt concentrations is monitored by electrochemical impedance spectroscopy. At 1 mM diazonium salt, 70% of total assembly is complete within 10 minutes, though total surface coverage by organics is limited to ≈ 0.15 monolayers. X-ray photoelectron spectroscopy confirms preferential bonding of organic molecules to iron over chromium, and adsorption of BF - 4 onto the surface. Secondary ionmore » mass spectroscopy reveals the ability of these films to self-heal when mechanically removed or damaged. Aging the diazonium salts in these nonaqueous environments demonstrates that up to 90% of the original diazonium salt concentration remains after 21 days at room temperature, while increasing the temperature beyond 50 °C results complete decomposition within 24 hours, regardless of solvent-salt combination.« less

Tailoring the Electrochemical Properties of Carbon Nanotube Modified Indium Tin Oxide via in Situ Grafting of Aryl Diazonium.

PubMed

Hicks, Jacqueline M; Wong, Zhi Yi; Scurr, David J; Silman, Nigel; Jackson, Simon K; Mendes, Paula M; Aylott, Jonathan W; Rawson, Frankie J

2017-05-23

Our ability to tailor the electronic properties of surfaces by nanomodification is paramount for various applications, including development of sensing, fuel cell, and solar technologies. Moreover, in order to improve the rational design of conducting surfaces, an improved understanding of structure/function relationships of nanomodifications and effect they have on the underlying electronic properties is required. Herein, we report on the tuning and optimization of the electrochemical properties of indium tin oxide (ITO) functionalized with single-walled carbon nanotubes (SWCNTs). This was achieved by controlling in situ grafting of aryl amine diazonium films on the nanoscale which were used to covalently tether SWCNTs. The structure/function relationship of these nanomodifications on the electronic properties of ITO was elucidated via time-of-flight secondary ion mass spectrometry and electrochemical and physical characterization techniques which has led to new mechanistic insights into the in situ grafting of diazonium. We discovered that the connecting bond is a nitro group which is covalently linked to a carbon on the aryl amine. The increased understanding of the surface chemistry gained through these studies enabled us to fabricate surfaces with optimized electron transfer kinetics. The knowledge gained from these studies allows for the rational design and tuning of the electronic properties of ITO-based conducting surfaces important for development of various electronic applications.

Metal-free carbonylations by photoredox catalysis.

PubMed

Majek, Michal; Jacobi von Wangelin, Axel

2015-02-09

The synthesis of benzoates from aryl electrophiles and carbon monoxide is a prime example of a transition-metal-catalyzed carbonylation reaction which is widely applied in research and industrial processes. Such reactions proceed in the presence of Pd or Ni catalysts, suitable ligands, and stoichiometric bases. We have developed an alternative procedure that is free of any metal, ligand, and base. The method involves a redox reaction driven by visible light and catalyzed by eosin Y which affords alkyl benzoates from arene diazonium salts, carbon monoxide, and alcohols under mild conditions. Tertiary esters can also be prepared in high yields. DFT calculations and radical trapping experiments support a catalytic photoredox pathway without the requirement for sacrificial redox partners. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nano-Electrochemistry and Nano-Electrografting with an Original Combined AFM-SECM

PubMed Central

Ghorbal, Achraf; Grisotto, Federico; Charlier, Julienne; Palacin, Serge; Goyer, Cédric; Demaille, Christophe; Ben Brahim, Ammar

2013-01-01

This study demonstrates the advantages of the combination between atomic force microscopy and scanning electrochemical microscopy. The combined technique can perform nano-electrochemical measurements onto agarose surface and nano-electrografting of non-conducting polymers onto conducting surfaces. This work was achieved by manufacturing an original Atomic Force Microscopy-Scanning ElectroChemical Microscopy (AFM-SECM) electrode. The capabilities of the AFM-SECM-electrode were tested with the nano-electrografting of vinylic monomers initiated by aryl diazonium salts. Nano-electrochemical and technical processes were thoroughly described, so as to allow experiments reproducing. A plausible explanation of chemical and electrochemical mechanisms, leading to the nano-grafting process, was reported. This combined technique represents the first step towards improved nano-processes for the nano-electrografting. PMID:28348337

Aryl diazonium for biomolecules immobilization onto SPRi chips.

PubMed

Mandon, Céline A; Blum, Loïc J; Marquette, Christophe A

2009-12-21

A method for the immobilization of proteins at the surface of surface plasmon resonance imaging (SPRi) chips is presented. The technology, based on the electro-deposition of a 4-carboxymethyl aryl diazonium (CMA) monolayer is compared to a classical thioctic acid self-assembled monolayer. SPRi live recording experiments followed by the quantification of the diazonium surface coverage demonstrate the presence of a monolayer of electro-deposited molecules (11*10(12) molecules mm(-2)). This monolayer, when activated through a classical carbodiimide route, generates a surface suitable for the protein immobilization. In the present study, protein A and BSA are immobilized as specific and control spots (150 microm id), respectively. The AFM characterization of the spots deposited onto CMA or thioctic acid modified chips prove the presence of 4.7 nm protein monolayers. Finally, the SPRi detection capabilities of the two surface chemistries are compared according to specific signal, non-specific interaction and regeneration possibilities. Advantages are given to the CMA surface modification since no measurable non-specific signal is obtained while reaching a higher specific signal.

Aryl-modified graphene quantum dots with enhanced photoluminescence and improved pH tolerance

NASA Astrophysics Data System (ADS)

Luo, Peihui; Ji, Zhe; Li, Chun; Shi, Gaoquan

2013-07-01

Chemical modification is an important technique to modulate the chemical and optical properties of graphene quantum dots (GQDs). In this paper, we report a versatile diazonium chemistry method to graft aryl groups including phenyl, 4-carboxyphenyl, 4-sulfophenyl and 5-sulfonaphthyl to GQDs via Gomberg-Bachmann reaction. The aryl-modified GQDs are nanocrystals with lateral dimensions in the range of 2-4 nm and an average thickness lower than 1 nm. Upon chemical modification with aryl groups, the photoluminescence (PL) bands of GQDs were tuned in the range of 418 and 447 nm, and their fluorescence quantum yields (QYs) were increased for up to about 6 times. Furthermore, the aryl-modified GQDs exhibited stable PL (both intensity and peak position) in a wide pH window of 1-11. The mechanism of improving the PL properties of GQDs by aryl-modification was also discussed.Chemical modification is an important technique to modulate the chemical and optical properties of graphene quantum dots (GQDs). In this paper, we report a versatile diazonium chemistry method to graft aryl groups including phenyl, 4-carboxyphenyl, 4-sulfophenyl and 5-sulfonaphthyl to GQDs via Gomberg-Bachmann reaction. The aryl-modified GQDs are nanocrystals with lateral dimensions in the range of 2-4 nm and an average thickness lower than 1 nm. Upon chemical modification with aryl groups, the photoluminescence (PL) bands of GQDs were tuned in the range of 418 and 447 nm, and their fluorescence quantum yields (QYs) were increased for up to about 6 times. Furthermore, the aryl-modified GQDs exhibited stable PL (both intensity and peak position) in a wide pH window of 1-11. The mechanism of improving the PL properties of GQDs by aryl-modification was also discussed. Electronic supplementary information (ESI) available: Fluorescence quantum yield measurements, estimation of grafting ratio, TEM images, FTIR spectra, PL spectra and zeta potentials. See DOI: 10.1039/c3nr02156d

Removal of amino groups from anilines through diazonium salt-based reactions.

PubMed

He, Linman; Qiu, Guanyinsheng; Gao, Yueqiu; Wu, Jie

2014-09-28

This minireview describes the applications of in situ generated diazonium salts from anilines in organic synthesis. In situ generation of diazonium salts from anilines represents an efficient and practical pathway, leading to a series of useful structures. In these transformations, the amino group of aniline formally acts as a leaving group. Two distinctive kinds of mechanisms, including transition metal (especially palladium)-catalyzed oxidative addition-reductive elimination and a radical process, are involved in the removal of amino groups from anilines, and both catalytic processes are described in this minireview.

Diazonium functionalized graphene: microstructure, electric, and magnetic properties.

PubMed

Huang, Ping; Jing, Long; Zhu, Huarui; Gao, Xueyun

2013-01-15

The unique honeycomb lattice structure of graphene gives rise to its outstanding electronic properties such as ultrahigh carrier mobility, ballistic transport, and more. However, a crucial obstacle to its use in the electronics industry is its lack of an energy bandgap. A covalent chemistry strategy could overcome this problem, and would have the benefits of being highly controllable and stable in the ambient environment. One possible approach is aryl diazonium functionalization. In this Account, we investigate the micromolecular/lattice structure, electronic structure, and electron-transport properties of nitrophenyl-diazonium-functionalized graphene. We find that nitrophenyl groups mainly adopt random and inhomogeneous configurations on the graphene basal plane, and that their bonding with graphene carbon atoms leads to slight elongation of the graphene lattice spacing. By contrast, hydrogenated graphene has a compressed lattice. Low levels of functionalization suppressed the electric conductivity of the resulting functionalized graphene, while highly functionalized graphene showed the opposite effect. This difference arises from the competition between the charge transfer effect and the scattering enhancement effect introduced by nitrophenyl groups bonding with graphene carbon atoms. Detailed electron transport measurements revealed that the nitrophenyl diazonium functionalization locally breaks the symmetry of graphene lattice, which leads to an increase in the density of state near the Fermi level, thus increasing the carrier density. On the other hand, the bonded nitrophenyl groups act as scattering centers, lowering the mean free path of the charge carriers and suppressing the carrier mobility. In rare cases, we observed ordered configurations of nitrophenyl groups in local domains on graphene flakes due to fluctuations in the reaction processes. We describe one example of such a superlattice, with a lattice constant nearly twice of that of pristine graphene. We performed comprehensive theoretical calculations to investigate the lattice and the electronic structure of the superlattice structure. Our results reveal that it is a thermodynamically stable, spin-polarized semiconductor with a bandgap of ∼0.5 eV. Our results demonstrate the possibility of controlling graphene's electronic properties using aryl diazonium functionalization. Asymmetric addition of aryl groups to different sublattices of graphene is a promising approach for producing ferromagnetic, semiconductive graphene, which will have broad applications in the electronic industry.

Reactions of aromatic diazonium salts with unsaturated compounds in the presence of nucleophiles

NASA Astrophysics Data System (ADS)

Grishchuk, B. D.; Gorbovoi, P. M.; Ganushchak, N. I.; Dombrovskii, A. V.

1994-03-01

The review surveys the reactions of aromatic diazonium salts with diene and monounsaturated compounds in the presence of nucleophiles. Certain further reactions of the reaction products and their application are considered. The bibliography includes 63 references.

Cellobiose Dehydrogenase Aryl Diazonium Modified Single Walled Carbon Nanotubes: Enhanced Direct Electron Transfer through a Positively Charged Surface

PubMed Central

2011-01-01

One of the challenges in the field of biosensors and biofuel cells is to establish a highly efficient electron transfer rate between the active site of redox enzymes and electrodes to fully access the catalytic potential of the biocatalyst and achieve high current densities. We report on very efficient direct electron transfer (DET) between cellobiose dehydrogenase (CDH) from Phanerochaete sordida (PsCDH) and surface modified single walled carbon nanotubes (SWCNT). Sonicated SWCNTs were adsorbed on the top of glassy carbon electrodes and modified with aryl diazonium salts generated in situ from p-aminobenzoic acid and p-phenylenediamine, thus featuring at acidic pH (3.5 and 4.5) negative or positive surface charges. After adsorption of PsCDH, both electrode types showed excellent long-term stability and very efficient DET. The modified electrode presenting p-aminophenyl groups produced a DET current density of 500 μA cm−2 at 200 mV vs normal hydrogen reference electrode (NHE) in a 5 mM lactose solution buffered at pH 3.5. This is the highest reported DET value so far using a CDH modified electrode and comes close to electrodes using mediated electron transfer. Moreover, the onset of the electrocatalytic current for lactose oxidation started at 70 mV vs NHE, a potential which is 50 mV lower compared to when unmodified SWCNTs were used. This effect potentially reduces the interference by oxidizable matrix components in biosensors and increases the open circuit potential in biofuel cells. The stability of the electrode was greatly increased compared with unmodified but cross-linked SWCNTs electrodes and lost only 15% of the initial current after 50 h of constant potential scanning. PMID:21417322

Cellobiose dehydrogenase aryl diazonium modified single walled carbon nanotubes: enhanced direct electron transfer through a positively charged surface.

PubMed

Tasca, Federico; Harreither, Wolfgang; Ludwig, Roland; Gooding, John Justin; Gorton, Lo

2011-04-15

One of the challenges in the field of biosensors and biofuel cells is to establish a highly efficient electron transfer rate between the active site of redox enzymes and electrodes to fully access the catalytic potential of the biocatalyst and achieve high current densities. We report on very efficient direct electron transfer (DET) between cellobiose dehydrogenase (CDH) from Phanerochaete sordida (PsCDH) and surface modified single walled carbon nanotubes (SWCNT). Sonicated SWCNTs were adsorbed on the top of glassy carbon electrodes and modified with aryl diazonium salts generated in situ from p-aminobenzoic acid and p-phenylenediamine, thus featuring at acidic pH (3.5 and 4.5) negative or positive surface charges. After adsorption of PsCDH, both electrode types showed excellent long-term stability and very efficient DET. The modified electrode presenting p-aminophenyl groups produced a DET current density of 500 μA cm(-2) at 200 mV vs normal hydrogen reference electrode (NHE) in a 5 mM lactose solution buffered at pH 3.5. This is the highest reported DET value so far using a CDH modified electrode and comes close to electrodes using mediated electron transfer. Moreover, the onset of the electrocatalytic current for lactose oxidation started at 70 mV vs NHE, a potential which is 50 mV lower compared to when unmodified SWCNTs were used. This effect potentially reduces the interference by oxidizable matrix components in biosensors and increases the open circuit potential in biofuel cells. The stability of the electrode was greatly increased compared with unmodified but cross-linked SWCNTs electrodes and lost only 15% of the initial current after 50 h of constant potential scanning. © 2011 American Chemical Society

Protein-diazonium adduct direct electrografting onto SPRi-biochip.

PubMed

Corgier, Benjamin P; Bellon, Sophie; Anger-Leroy, Marielle; Blum, Loïc J; Marquette, Christophe A

2009-08-18

A direct protein immobilization method for surface plasmon resonance imaging (SPRi) gold chip arraying is exposed. The biomolecule electroaddressing strategy, previously demonstrated by our team on carbon surfaces, is here valuably involved and adapted to create a straightforward and efficient protein immobilization process onto SPRi-biochips. The proteins, modified with an aryl-diazonium adduct, are addressed to the SPRi chip surface through the electroreduction of the aryl-diazonium. The biomolecule deposition was followed through SPRi live measurements during the electrografting process. A specially designed setup enabled us to directly observe the mass increasing at the sensor surface while the proteins were electrografted. A pin electrospotting method, allowing the achievement of distinct sensing layers on gold SPRi-biochips, was used to generate microarray biochips. The integrity of the immobilized proteins and the specificity of the detection, based on antigen/antibody interactions, were demonstrated for the detection of specific antibodies and ovalbumin. The SPRi detection limit of ovalbumin using the electroaddressing of anti-ovalbumin IgG was compared with two other immobilization procedures, cystamine-glutaraldehyde self-assembled monolayer and pyrrole, and was found to be a decade lower than these ones (100 ng/mL, i.e., 2 nM).

A simple, enaminone-based approach to some bicyclic pyridazinium tetrafluoroborates

PubMed Central

Josefík, František; Svobodová, Markéta; Bertolasi, Valerio

2013-01-01

Summary Easily obtainable cyclic enaminones (piperidin-2-ylidenealkanones) can be transformed into substituted bicyclic pyridazinium tetrafluoroborates upon treatment with corresponding diazonium salts. The transformation can be performed either in a one-pot way or in a two-step process with the isolation of single azo-coupled enaminone as the intermediate. The former method is superior. Under the optimized conditions, a number of pyridazinium salts substituted with both electron-donating and electron-withdrawing substituents was easily synthesized. A mechanism of the formation of the pyridazinium salts is suggested. A partial drawback is the possibility of the formation of a mixture of products when using a different diazonium salt in each step due to a reversibility of the azo coupling. This can be suppressed by using a more reactive diazonium salt before a less reactive one. PMID:23946844

Electrografted diazonium salt layers for antifouling on the surface of surface plasmon resonance biosensors.

PubMed

Zou, Qiongjing; Kegel, Laurel L; Booksh, Karl S

2015-02-17

Electrografted diazonium salt layers on the surface of surface plasmon resonance (SPR) sensors present potential for a significant improvement in antifouling coatings. A pulsed potential deposition profile was used in order to circumvent mass-transport limitations for layer deposition rate. The influence of number of pulses with respect to antifouling efficacy was evaluated by nonspecific adsorption surface coverage of crude bovine serum proteins. Instead of using empirical and rough estimated values, the penetration depth and sensitivity of the SPR instrument were experimentally determined for the calculation of nonspecific adsorption surface coverage. This provides a method to better examine antifouling surface coatings and compare crossing different coatings and experimental systems. Direct comparison of antifouling performance of different diazonium salts was facilitated by a tripad SPR sensor design. The electrografted 4-phenylalanine diazonium chloride (4-APhe) layers with zwitterionic characteristic demonstrate ultralow fouling.

Acid-promoted Bicyclization of Diaryl Alkynes: Synthesis of 2H-Indazoles with in situ Generated Diazonium Salt as Nitrogen Source.

PubMed

Zhang, Cheng; Chang, Sailan; Dong, Shanliang; Qiu, Lihua; Xu, Xinfang

2018-06-08

An unprecedented transition-metal-free tandem bicyclization of diaryl alkynes has been disclosed, which provides a streamlined access to a range of polycyclic 2H-indazoles in high to excellent yields. The salient features of this reaction include readily available starting materials, good functional group compatibility, mild reaction conditions, no column chromatography, high bond-formation efficiency, and ease in further transformations. Notably, this is the first example for the synthesis of 2H-indazoles with in situ generated diazonium salt as the nitrogen source, and a mechanistic rationale involving an acid-promoted tandem diazonium salt formation/bicyclization process is discussed.

A One-Pot Synthesis of m-Terphenyls: A Guided Exploration of Reaction Chemistry, Chromatography, and Spectroscopy. A Miniproject for the Advanced Organic Chemistry Laboratory

NASA Astrophysics Data System (ADS)

Anam, Kishorekumar T.; Curtis, Michael P.; Irfan, Muhammad J.; Johnson, Michael P.; Royer, Andrew P.; Shahmohammadi, Kianor; Vinod, Thottumkara K.

2002-05-01

This four-week project-based laboratory exercise, developed for advanced organic chemistry students, involves a one-pot synthesis of m-terphenyls. Chemistry of aryl diazonium salts and Grignard reagents and reactivity of aryne intermediates toward nucleophilic reagents form the reaction chemistry basis for the project. The project exposes students to a number of important laboratory techniques (thin-layer chromatography, gas chromatography-mass spectrometry, and column chromatography) for monitoring reaction progress and product isolation. A variety of spectroscopic techniques, including IR, 1H NMR, 13C NMR, and attached proton test are used for product characterization. Students are also introduced to a useful empirical relationship to help predict (with considerable accuracy) the 13C chemical shift values of carbon atoms of substituted benzenes.

Functionalized alkoxy arene diazonium salts from paracetamol.

PubMed

Schmidt, Bernd; Berger, René; Hölter, Frank

2010-03-21

Arene diazonium tetrafluoroborates can be synthesized from aromatic acetamides via a sequence of deacetylation, diazotation and precipitation, induced by anion exchange. The reaction is conducted as a convenient one-flask transformation with consecutive addition of the appropriate reagents. Exchange of solvents or removal of byproducts prior to isolation of the product is not required. The arene diazonium salts are isolated from the reaction mixture by simple filtration. Two complementary protocols are presented, and the utility of the reaction is exemplified for a synthesis of the diarylheptanoid natural product de-O-methyl centrolobine.

40 CFR 721.9597 - Salt of a substituted sulfonated aryl azo compound (generic).

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Salt of a substituted sulfonated aryl... New Uses for Specific Chemical Substances § 721.9597 Salt of a substituted sulfonated aryl azo... substance identified generically as salt of a substituted sulfonated aryl azo compound (PMN P-00-0094) is...

40 CFR 721.9597 - Salt of a substituted sulfonated aryl azo compound (generic).

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Salt of a substituted sulfonated aryl... New Uses for Specific Chemical Substances § 721.9597 Salt of a substituted sulfonated aryl azo... substance identified generically as salt of a substituted sulfonated aryl azo compound (PMN P-00-0094) is...

Synthesis, antioxidant and antibacterial activities of 3-nitrophenyl ferrocene

NASA Astrophysics Data System (ADS)

Benabdesselam, S.; Izza, H.; Lanez, T.; Guechi, E. K.

2018-03-01

The current work aims in its first part to synthesize 3-nitrophenylferrocene after diazotizing nitroaniline in the meta position by the sodium nitrite and the formation of the corresponding diazonium salt: 3-nitrobenzendiazonium sulfate, then the salt in solution was added to the ferrocene for the purpose of introducing the nitrophenyl moiety thereon (arylation) and the formation of 3-nitrophenylferrocene. The second part is devoted to the study of the antioxidant activity of 3-NPF by applying the trapping test of superoxide radical using cyclic voltammetry, the free radical DPPH trapping test by spectrophotometry. The results showed that 3-nitrophenylferrocene has a scavenging effect of DPPH radical with IC50 = 1.44mg/ml, superoxide radical with IC50=5.38mg/ml. The third part is devoted to the study of antibacterial activity of the synthesized compound tested on four strains of bacteria: Escherichia coli, Pseudomonas aeruginosa, Enterococcus faecalis and Klebsiella pneumoniae. The obtained results clearly showed that 3-nitrophenylferrocene has low activities on the four bacterial strains with diameters of inhibition zones do not exceeding 17 mm at concentrations of 25mg/ml.

Fabrication of biomembrane-like films on carbon electrodes using alkanethiol and diazonium salt and their application for direct electrochemistry of myoglobin.

PubMed

Anjum, Saima; Qi, Wenjing; Gao, Wenyue; Zhao, Jianming; Hanif, Saima; Aziz-Ur-Rehman; Xu, Guobao

2015-03-15

Alkanethiols generally form self-assembled monolayers on gold electrodes and the electrochemical reduction of aromatic diazonium salts is a popular method for the covalent modification of carbon. Based on the reaction of alkanethiol with aldehyde groups covalently bound on carbon surface by the electrochemical reduction of aromatic diazonium salts, a new strategy for the modification of carbon electrodes with alkanethiols has been developed. The modification of carbon surface with aldehyde groups is achieved by the electrochemical reduction of aromatic diazonium salts in situ electrogenerated from a nitro precursor, p-nitrophenylaldehyde, in the presence of nitrous acid. By this way, in situ electrogenerated p-aminophenyl aldehyde from p-nitrophenylaldehyde immediately reacts with nitrous acid, effectively minimizing the side reaction of amine groups and aldehyde groups. The as-prepared alkanethiol-modified glassy carbon electrode was further used to make biomembrane-like films by casting didodecyldimethylammonium bromide on its surface. The biomembrane-like films enable the direct electrochemistry of immobilized myoglobin for the detection of hydrogen peroxide. The response is linear over the range of 1-600μM with a detection limit of 0.3μM. Copyright © 2014 Elsevier B.V. All rights reserved.

Electrodeposition of gold nanoparticles on aryl diazonium monolayer functionalized HOPG surfaces.

PubMed

González, M C R; Orive, A G; Salvarezza, R C; Creus, A H

2016-01-21

Gold nanoparticle electrodeposition on a modified HOPG surface with a monolayer organic film based on aryl diazonium chemistry has been studied. This organic monolayer is electrochemically grown with the use of 2,2-diphenyl-1-picrylhydrazyl (DPPH), a radical scavenger. The electrodeposition of gold on this modified surface is highly favored resulting in an AuNP surface density comparable to that found on glassy carbon. AuNPs grow only in the areas covered by the organic monolayer leaving free clean HOPG zones. A progressive mechanism for the nucleation and growth is followed giving hemispherical AuNPs, homogeneously distributed on the surface and their sizes can be well controlled by the applied electrodeposition potential. By using AFM, C-AFM and electrochemical measurements with the aid of two redox probes, namely Fe(CN)6(4-)/Fe(CN)6(3-) and dopamine, relevant results about the electrochemical modified surface as well as the gold nanoparticles electrodeposited on them are obtained.

Diazonium-protein adducts for graphite electrode microarrays modification: direct and addressed electrochemical immobilization.

PubMed

Corgier, Benjamin P; Marquette, Christophe A; Blum, Loïc J

2005-12-28

Diazonium cation electrodeposition was investigated for the direct and electro-addressed immobilization of proteins. For the first time, this reaction was triggered directly onto diazonium-modified proteins. Screen-printed (SP) graphite electrode microarrays were studied as active support for this immobilization. A 10-microelectrode (eight working electrodes, 0.2 mm2 each; one reference; and one auxiliary) setup was used to study the addressing possibilities of the method. These electrode microarrays were shown to be able to covalently graft diazonium cations through electrochemical reduction. Cyclic voltammetry and X-ray photoelectron spectroscopy were used to characterize the electrochemical grafting onto our SP graphite surface and suggested that a diazonium monolayer was deposited. Rabbit and human immunoglobulins (IgGs) were then chemically coupled to an aniline derivative (4-carboxymethylaniline), followed by diazotation to form an aryl diazonium function available for the electrodeposition. These modified proteins were both successfully electro-addressed at the surface of the graphite electrodes without cross-talk or interference. The immuno-biochip obtained using this novel approach enabled the specific detection of anti-rabbit IgG antibodies with a detection limit of 50 fmol of protein. A promising strategy to immobilize markedly different biological entities was then presented, providing an excellent spatial specificity of the electro-addressing.

Diazotisation of Weakly Basic Aromatic and Heterocyclic Amines in Strongly Acid Media

NASA Astrophysics Data System (ADS)

Godovikova, Tamara I.; Rakitin, Oleg A.; Khmel'nitskii, Lenor I.

1983-05-01

The review is devoted to the diazotisation of weakly basic aromatic amines. The methods of synthesis of diazonium salts based on these amines by non-traditional methods are examined. Data on the mechanism of the diazotisation reaction in strongly acid media are surveyed. Reactions of diazonium salts leading to the synthesis of new compounds are presented. The bibliography includes 75 references.

Fine tuning of graphene properties by modification with aryl halogens

NASA Astrophysics Data System (ADS)

Bouša, D.; Pumera, M.; Sedmidubský, D.; Šturala, J.; Luxa, J.; Mazánek, V.; Sofer, Z.

2016-01-01

Graphene and its derivatives belong to one of the most intensively studied materials. The radical reaction using halogen derivatives of arene-diazonium salts can be used for effective control of graphene's electronic properties. In our work we investigated the influence of halogen atoms (fluorine, chlorine, bromine and iodine) as well as their position on the benzene ring towards the electronic and electrochemical properties of modified graphenes. The electronegativity as well as the position of the halogen atoms on the benzene ring has crucial influence on graphene's properties due to the inductive and mesomeric effects. The results of resistivity measurement are in good agreement with the theoretical calculations of electron density within chemically modified graphene sheets. Such simple chemical modifications of graphene can be used for controllable and scalable synthesis of graphene with tunable transport properties.Graphene and its derivatives belong to one of the most intensively studied materials. The radical reaction using halogen derivatives of arene-diazonium salts can be used for effective control of graphene's electronic properties. In our work we investigated the influence of halogen atoms (fluorine, chlorine, bromine and iodine) as well as their position on the benzene ring towards the electronic and electrochemical properties of modified graphenes. The electronegativity as well as the position of the halogen atoms on the benzene ring has crucial influence on graphene's properties due to the inductive and mesomeric effects. The results of resistivity measurement are in good agreement with the theoretical calculations of electron density within chemically modified graphene sheets. Such simple chemical modifications of graphene can be used for controllable and scalable synthesis of graphene with tunable transport properties. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr06295k

Mapping nanometric electronic property changes induced by an aryl diazonium sub-monolayer on HOPG.

PubMed

González, M C R; Carro, P; Vázquez, L; Creus, A H

2016-10-26

The morphology as well as the electric and electronic properties of aryl diazonium, in particular 4-nitrobenzene-diazonium (NBD), films on HOPG surfaces have been studied at the nanoscale level. By controlling the 2,2-diphenyl-1-picrylhydrazyl concentration during the NBD film growth, we have been able to control the thickness of the layer. The implications of NBD submonolayer adsorption on the electrical properties of this system have been analysed through Density Functional Theory (DFT) calculations, Atomic Force (AFM), Electric Force (EFM) and Kelvin Probe Force (KPFM) microscopies. DFT simulations showed that the NBD molecule adsorbs almost perpendicularly to the HOPG surface, which was confirmed experimentally through AFM imaging in the dynamic mode. In addition, DFT calculations showed that the adsorbed NBD has an appreciable dipole moment directed towards the HOPG surface and along the vertical direction of the HOPG surface. The existence of this dipole is the origin of the EFM contrast observed between the NBD-free and NBD-covered regions when a bias of -2 V was applied to the tip. Besides, the KPFM measurements show that the NBD adsorption leads to higher work function values, which is in agreement with the DFT calculations. Noticeably, our studies show that the KPFM signal is sensitive to the partial NBD coverage of the HOPG surface below the monolayer level.

Amine-selective bioconjugation using arene diazonium salts.

PubMed

Diethelm, Stefan; Schafroth, Michael A; Carreira, Erick M

2014-08-01

A novel bioconjugation strategy is presented that relies on the coupling of diazonium terephthalates with amines in proteins. The diazonium captures the amine while the vicinal ester locks it through cyclization, ensuring no reversibility. The reaction is highly efficient and proceeds under mild conditions and short reaction times. Densely functionalized, complex natural products were directly coupled to proteins using low concentrations of coupling partners.

Formation of mixed organic layers by stepwise electrochemical reduction of diazonium compounds.

PubMed

Santos, Luis; Ghilane, Jalal; Lacroix, Jean Christophe

2012-03-28

This work describes the formation of a mixed organic layer covalently attached to a carbon electrode. The strategy adopted is based on two successive electrochemical reductions of diazonium salts. First, bithiophene phenyl (BTB) diazonium salt is reduced using host/guest complexation in a water/cyclodextrin (β-CD) solution. The resulting layer consists of grafted BTB oligomers and cyclodextrin that can be removed from the surface. The electrochemical response of several outer-sphere redox probes on such BTB/CD electrodes is close to that of a diode, thanks to the easily p-dopable oligo(BTB) moieties. When CD is removed from the surface, pinholes are created and this diode like behavior is lost. Following this, nitrophenyl (NP) diazonium is reduced to graft a second component. Electrochemical study shows that upon grafting NP insulating moieties, the diode-like behavior of the layer is restored which demonstrates that NP is grafted predominately in the empty spaces generated by β-CD desorption. As a result, a mixed BTB/NP organic layer covalently attached to a carbon electrode is obtained using a stepwise electrochemical reduction of two diazonium compounds.

Triggering the Electrolyte-Gated Organic Field-Effect Transistor output characteristics through gate functionalization using diazonium chemistry: Application to biodetection of 2,4-dichlorophenoxyacetic acid.

PubMed

Nguyen, T T K; Nguyen, T N; Anquetin, G; Reisberg, S; Noël, V; Mattana, G; Touzeau, J; Barbault, F; Pham, M C; Piro, B

2018-08-15

We investigated an Electrolyte-Gated Organic Field-Effect transistor based on poly(N-alkyldiketopyrrolo-pyrrole dithienylthieno[3,2-b]thiophene) as organic semiconductor whose gate electrode was functionalized by electrografting a functional diazonium salt capable to bind an antibody specific to 2,4-dichlorophenoxyacetic acid (2,4-D), an herbicide well-known to be a soil and water pollutant. Molecular docking computations were performed to design the functional diazonium salt to rationalize the antibody capture on the gate surface. Sensing of 2,4-D was performed through a displacement immunoassay. The limit of detection was estimated at around 2.5 fM. Copyright © 2018 Elsevier B.V. All rights reserved.

Mesomeric Effects of Graphene Modified with Diazonium Salts: Substituent Type and Position Influence its Properties.

PubMed

Bouša, Daniel; Jankovský, Ondřej; Sedmidubský, David; Luxa, Jan; Šturala, Jiří; Pumera, Martin; Sofer, Zdeněk

2015-12-01

In the last decade, graphene and graphene derivatives have become some of the most intensively studied materials. Tuning of the electronic and electrochemical properties of graphene is of paramount importance. In this study, six diazonium-modified graphenes containing different functional groups according to the diazonium salt precursor were investigated. These diazonium moieties have a strong mesomeric (resonance) effect and act as either electron-donating or -withdrawing species. Different graphene precursors, such as thermally and chemically reduced graphenes were studied. All the products were characterized in detail by elemental combustion analysis, FTIR spectroscopy, Raman spectroscopy, high-resolution X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry. Resistivity and zeta potential measurements were consistent with theoretical (DFT) calculations. The results show that chemical modification of graphene by diazotation strongly influences its properties, creating a huge application potential in microelectronics, energy storage and conversion devices, and electrocatalysis. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

XPS study of ruthenium tris-bipyridine electrografted from diazonium salt derivative on microcrystalline boron doped diamond.

PubMed

Agnès, Charles; Arnault, Jean-Charles; Omnès, Franck; Jousselme, Bruno; Billon, Martial; Bidan, Gérard; Mailley, Pascal

2009-12-28

Boron doped diamond (BDD) functionalization has received an increasing interest during the last few years. Such an infatuation comes from the original properties of BDD, including chemical stability or an electrochemical window, that opens the way for the design of (bio)sensors or smart interfaces. In such a context, diazonium salts appear to be well suited for BDD functionalization as they enable covalent immobilization of functional entities such as enzymes or DNA. In this study we report microcrystalline BDD functionalization with a metallic complex, ruthenium tris(bipyridine), using the p-(tris(bipyridine)Ru(2+))phenyl diazonium salt. Electrografting using cyclic voltammetry (CV) allowed the formation of a ruthenium complex film that was finely characterized using electrochemistry and X-ray photoelectron spectroscopy (XPS). Moreover, we showed that chronopotentiometry (CP) is a convenient tool to monitor Ru complex film deposition through the control of the electrochemical pulse parameters (i.e. current density and pulse duration). Finally, such a control was demonstrated through the correlation between electrochemical and XPS characterizations.

Direct peptide bioconjugation/PEGylation at tyrosine with linear and branched polymeric diazonium salts.

PubMed

Jones, Mathew W; Mantovani, Giuseppe; Blindauer, Claudia A; Ryan, Sinead M; Wang, Xuexuan; Brayden, David J; Haddleton, David M

2012-05-02

Direct polymer conjugation at peptide tyrosine residues is described. In this study Tyr residues of both leucine enkephalin and salmon calcitonin (sCT) were targeted using appropriate diazonium salt-terminated linear monomethoxy poly(ethylene glycol)s (mPEGs) and poly(mPEG) methacrylate prepared by atom transfer radical polymerization. Judicious choice of the reaction conditions-pH, stoichiometry, and chemical structure of diazonium salt-led to a high degree of site-specificity in the conjugation reaction, even in the presence of competitive peptide amino acid targets such as histidine, lysines, and N-terminal amine. In vitro studies showed that conjugation of mPEG(2000) to sCT did not affect the peptide's ability to increase intracellular cAMP induced in T47D human breast cancer cells bearing sCT receptors. Preliminary in vivo investigation showed preserved ability to reduce [Ca(2+)] plasma levels by mPEG(2000)-sCT conjugate in rat animal models. © 2012 American Chemical Society

Enhanced chemiluminescence-based detection on gold substrate after electrografting of diazonium precursor-coated gold nanoparticles.

PubMed

Houmed Adabo, Ali; Zeggari, Rabah; Mohamed Saïd, Nasser; Bazzi, Rana; Elie-Caille, Céline; Marquette, Christophe; Martini, Matteo; Tillement, Olivier; Perriat, Pascal; Chaix, Carole; Boireau, Wilfrid; Roux, Stéphane

2016-04-01

Since it was demonstrated that nanostructured surfaces are more efficient for the detection based on the specific capture of analytes, there is a real need to develop strategies for grafting nanoparticles onto flat surfaces. Among the different routes for the functionalization of a surface, the reduction of diazonium salts appears very attractive for the covalent immobilization of nanoparticles because this method does not require a pre-treatment of the surface. For achieving this goal, gold nanoparticles coated by precursor of diazonium salts were synthesized by reduction of gold salt in presence of mercaptoaniline. These mercaptoaniline-coated gold nanoparticles (Au@MA) were successfully immobilized onto various conducting substrates (indium tin oxide (ITO), glassy carbon (GC) and gold electrodes with flat terraces) after addition of sodium nitrite at fixed potential. When applied onto the gold electrodes, such a grafting strategy led to an obvious enhancement of the luminescence of luminol used for the biodetection. Copyright © 2016 Elsevier Inc. All rights reserved.

The reaction of Grignard reagents with Bunte salts: a thiol-free synthesis of sulfides.

PubMed

Reeves, Jonathan T; Camara, Kaddy; Han, Zhengxu S; Xu, Yibo; Lee, Heewon; Busacca, Carl A; Senanayake, Chris H

2014-02-21

S-Alkyl, S-aryl, and S-vinyl thiosulfate sodium salts (Bunte salts) react with Grignard reagents to give sulfides in good yields. The S-alkyl Bunte salts are prepared from odorless sodium thiosulfate by an SN2 reaction with alkyl halides. A Cu-catalyzed coupling of sodium thiosulfate with aryl and vinyl halides was developed to access S-aryl and S-vinyl Bunte salts. The reaction is amenable to a broad structural array of Bunte salts and Grignard reagents. Importantly, this route to sulfides avoids the use of malodorous thiol starting materials or byproducts.

Aryl imidazylates and aryl sulfates as electrophiles in metal-free ArS(N)1 reactions.

PubMed

Qrareya, Hisham; Protti, Stefano; Fagnoni, Maurizio

2014-12-05

Some oxygen-bonded substituents were investigated as leaving groups in photoinduced ArS(N)1 reactions. Irradiation of aryl imidazylates and of the corresponding imidazolium salts mainly caused homolysis of the ArO-S bond. However, previously unexplored trifluoroethoxy aryl sulfates were found to undergo efficient metal-free arylation. The sulfates were conveniently generated in situ by dissolving the corresponding imidazolium salts in basic 2,2,2-trifluoroethanol.

Controlled Zn-mediated grafting of thin layers of bipodal diazonium salt on gold and carbon substrates.

PubMed

Torréns, Mabel; Ortiz, Mayreli; Turner, Anthony P F; Beni, Valerio; O'Sullivan, Ciara K

2015-01-07

A controlled, rapid, and potentiostat-free method has been developed for grafting the diazonium salt (3,5-bis(4-diazophenoxy)benzoic acid tetrafluoroborate (DCOOH)) on gold and carbon substrates, based on a Zn-mediated chemical dediazonation. The highly stable thin layer organic platforms obtained were characterized by cyclic voltammetry, AFM, impedance, XP, and Raman spectroscopies. A dediazonation mechanism based on radical formation is proposed. Finally, DCOOH was proved as a linker to an aminated electroactive probe. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The Onium Compounds

NASA Astrophysics Data System (ADS)

Tsarevsky, Nicolay V.; Slaveykova, Vera; Manev, Stefan; Lazarov, Dobri

1997-06-01

The onium salts are of a big interest for theoretical and structural chemistry, and for organic synthesis. Some representatives of the group (e.g. ammonium salts) were known from the oldest times. Many onium salts are met the nature: ammonium salts (either as inorganic salts, and organic derivatives, e.g. aminoacids, salts of biogenic amines and alkaloids, etc.); oxonium salts (plant pigments as anthocyans are organic oxonium compounds), etc. In 1894 C. Hartmann and V. Meyer prepared the first iodonium salts - 4-iododiphenyliodonium hydrogensulfate and diphenyliodonium salts, and suggested the ending -onium for all compounds with properties similar to those of ammonium salts. Nowadays onium compounds of almost all nonmetals are synthesised and studied. A great variety of physical methods: diffraction (e.g. XRD) and spectral methods (IR-, NMR-, and UV-spectra), as well as the chemical properties and methods of preparation of onium salts have been used in determination of the structure of these compounds. The application of different onium salts is immense. Ammonium, phosphonium and sulfonium salts are used as phase-transfer catalysts; diazonium salts - for the preparation of dyes, metalochromic and pH-indicators. All the onium salts and especially diazonium and iodonium salts are very useful reagents in organic synthesis.

Controlled, Site-Specific Functionalization of Carbon Nanotubes with Diazonium Salts

NASA Technical Reports Server (NTRS)

Tour, James M.

2013-01-01

This work uses existing technologies to prepare a crossbar architecture of nano tubes, wherein one nanotube is fixed to a substrate, and a second nanotube is suspended a finite distance above. Both nano tubes can be individually addressed electrically. Application of opposite potentials to the two tubes causes the top tube to deform and to essentially come into contact with the lower tube. Contact here refers not to actual, physical contact, but rather within an infinitesimally small distance referred to as van der Walls contact, in which the entities may influence each other on a molecular and electronic scale. First, the top tube is physically deformed, leading to a potentially higher chemical reactivity at the point of deformation, based on current understanding of the effects of curvature strain on reactivity. This feature would allow selective functionalization at the junction via reaction with diazonium salts. Secondly, higher potential is achieved at the point of "cross" between the tubes. In a pending patent application, a method is claimed for directed self-assembly of molecular components onto the surface of metal or conductive materials by application of potential to the metal or conductive surface. In another pending patent application, a method is claimed for attaching molecules to the surface of nanotubes via the use of reactive diazonium salts. In the present invention, the directed functionalization of the crossed-nanotube junctions by applying a potential to the ends of the nanotubes in the presence of reactive diazonium slats, or other reactive molecular species is claimed. The diazonium salts are directed by the potential existing at the junction to react with the surface of the nanotube, thus placing functional molecular components at the junctions. The crossed nano tubes therefore provide a method of directly addressing the functionalized molecules, which have been shown to function as molecular switches, molecular wires, and in other capacities and uses. Site-specific functionalization may enable the use of nanotubes in molecular electronic applications because device functionality is critical at the cross points.

Efficient Covalent Modification of Multiwalled Carbon Nanotubes with Diazotized Dyes in Water at Room Temperature.

PubMed

Bensghaïer, Asma; Lau Truong, Stéphanie; Seydou, Mahamadou; Lamouri, Aazdine; Leroy, Eric; Mičušik, Matej; Forro, Klaudia; Beji, Mohamed; Pinson, Jean; Omastová, Mária; Chehimi, Mohamed M

2017-07-11

Tetrafluoroborate salts of diazotized Azure A (AA-N 2 + ), Neutral Red (NR-N 2 + ) and Congo Red (CR-N 2 + ) dyes were prepared and reacted with multiwalled carbon nanotubes (MWCNTs) at room temperature, in water without any reducing agent. The as-modified MWCNTs were examined by IRATR, Raman spectroscopy, XPS, TGA, TEM, and cyclic voltammetry. The diazonium band located at ∼2350 cm -1 in the diazotized dye IR spectra vanished after attachment to the nanotubes whereas the Raman D/G peak ratio slightly increased after dye covalent attachment at a high initial diazonium/CNT mass ratio. XPS measurements show the loss of F 1s from the BF 4 - anion together with a clear change in the high-resolution C 1s region from the modified nanotubes. Thermogravimetric analyses proved substantial mass loadings of the organic grafts leveling off at 40.5, 34.3, and 50.7 wt % for AA, NR, and CR, respectively. High-resolution TEM pictures confirmed the presence of 1.5-7-nm-thick continuous amorphous layers on the nanotubes assigned to the aryl layers from the dyes. Cyclic voltammetry studies in acetonitrile (ACN) confirmed the grafting of the dyes; the latter retain their electrochemical behavior in the grafted state. The experimental results correlate remarkably well with quantum chemical calculations that indicate high binding energies between the dyes and the CNTs accounting for true covalent bonding (140-185 kJ/mol with the CNT-aryl distance <1.6 nm), though attachment by π stacking also contributes to obtaining stable hybrids. Finally, the pH-responsive character of the robust hybrids was demonstrated by a higher degree of protonation of Neutral Red-grafted CNTs at pH 2 compared to that of the neutral aqueous medium. This work demonstrates that diazotized dyes can be employed for the surface modification of MWCNTs in a very simple and efficient manner in water and at room temperature. The hybrids could be employed for many purposes such as optically pH-responsive materials, biosensors, and optothermal composite actuators to name a few.

Formylbenzene diazonium hexafluorophosphate reagent for tyrosine-selective modification of proteins and the introduction of a bioorthogonal aldehyde

PubMed Central

Gavrilyuk, Julia; Ban, Hitoshi; Nagano, Masanobu; Hakamata, Wataru; Barbas, Carlos F.

2012-01-01

4-Formylbenzene diazonium hexafluorophosphate (FBDP) is a novel bench-stable crystalline diazonium salt that reacts selectively with tyrosine to install a bioorthogonal aldehyde functionality. Model studies with N-acyl-tyrosine methylamide allowed us to identify conditions optimal for tyrosine ligation reactions with small peptides and proteins. FBDP-based conjugation was used for the facile introduction of small molecule tags, poly(ethylene) glycol chains (PEGylation), and functional small molecules onto model proteins and to label the surface of living cells. PMID:23181702

Formylbenzene diazonium hexafluorophosphate reagent for tyrosine-selective modification of proteins and the introduction of a bioorthogonal aldehyde.

PubMed

Gavrilyuk, Julia; Ban, Hitoshi; Nagano, Masanobu; Hakamata, Wataru; Barbas, Carlos F

2012-12-19

4-Formylbenzene diazonium hexafluorophosphate (FBDP) is a novel bench-stable crystalline diazonium salt that reacts selectively with tyrosine to install a bioorthogonal aldehyde functionality. Model studies with N-acyl-tyrosine methylamide allowed us to identify conditions optimal for tyrosine ligation reactions with small peptides and proteins. FBDP-based conjugation was used for the facile introduction of small molecule tags, poly(ethylene glycol) chains (PEGylation), and functional small molecules onto model proteins and to label the surface of living cells.

Integrated Affinity Biosensing Platforms on Screen-Printed Electrodes Electrografted with Diazonium Salts

PubMed Central

Yáñez-Sedeño, Paloma

2018-01-01

Adequate selection of the electrode surface and the strategies for its modification to enable subsequent immobilization of biomolecules and/or nanomaterials integration play a major role in the performance of electrochemical affinity biosensors. Because of the simplicity, rapidity and versatility, electrografting using diazonium salt reduction is among the most currently used functionalization methods to provide the attachment of an organic layer to a conductive substrate. This particular chemistry has demonstrated to be a powerful tool to covalently immobilize in a stable and reproducible way a wide range of biomolecules or nanomaterials onto different electrode surfaces. Considering the great progress and interesting features arisen in the last years, this paper outlines the potential of diazonium chemistry to prepare single or multianalyte electrochemical affinity biosensors on screen-printed electrodes (SPEs) and points out the existing challenges and future directions in this field. PMID:29495294

Integrated Affinity Biosensing Platforms on Screen-Printed Electrodes Electrografted with Diazonium Salts.

PubMed

Yáñez-Sedeño, Paloma; Campuzano, Susana; Pingarrón, José M

2018-02-24

Adequate selection of the electrode surface and the strategies for its modification to enable subsequent immobilization of biomolecules and/or nanomaterials integration play a major role in the performance of electrochemical affinity biosensors. Because of the simplicity, rapidity and versatility, electrografting using diazonium salt reduction is among the most currently used functionalization methods to provide the attachment of an organic layer to a conductive substrate. This particular chemistry has demonstrated to be a powerful tool to covalently immobilize in a stable and reproducible way a wide range of biomolecules or nanomaterials onto different electrode surfaces. Considering the great progress and interesting features arisen in the last years, this paper outlines the potential of diazonium chemistry to prepare single or multianalyte electrochemical affinity biosensors on screen-printed electrodes (SPEs) and points out the existing challenges and future directions in this field.

Fast dye salts provide fast access to azidoarene synthons in multi-step one-pot tandem click transformations

PubMed Central

Fletcher, James T.; Reilly, Jacquelline E.

2012-01-01

This study examined whether commercially available diazonium salts could be used as efficient aromatic azide precursors in one-pot multi-step click transformations. Seven different diazonium salts, including Fast Red RC, Fast Blue B, Fast Corinth V and Variamine Blue B were surveyed under aqueous click reaction conditions of CuSO4/Na ascorbate catalyst with 1:1 t-BuOH:H2O solvent. Two-step tandem reactions with terminal alkyne and diyne co-reactants led to 1,2,3-triazole products in 66%-88% yields, while three-step tandem reactions with trimethylsilyl-protected alkyne and diyne co-reactants led to 1,2,3-triazole products in 61%-78% yields. PMID:22368306

Reductive electrografting of benzene (p-bisdiazonium hexafluorophosphate): a simple and effective protocol for creating diazonium-functionalized thin films.

PubMed

Marshall, Nicholas; Locklin, Jason

2011-11-01

In this Article, we describe a protocol for surface functionalization of benzenediazonium hexafluorophosphate monolayers by in situ electrochemical reduction of bis(benzenediazonium) hexafluorophosphate. Due to the considerable difference in potential between the first and second reduction of this species, it is possible to form a high density of surface-bound diazonium groups by use of a mild potential which selectively reduces only one diazonium group per ring. The resulting diazonium-containing monolayer reacts readily with solutions of electron-rich aromatic compounds. The reaction with ferrocene produces a dense (2.7 × 10(-10) mol/cm(2)) ferrocene-containing monolayer through a Gomberg-Bachmann type arylation. The resulting ferrocene group exhibits relatively rapid electron transfer to the electrode due to the conjugated linker layer as measured by alternating current voltammetry (ACV) and cyclic voltammetry. Aromatic systems with π-donor substitutents (N,N-dimethylaniline, N,N,N',N'-tetramethyldiaminobenzophenone, and hydroquinone) react through an azo-coupling to form monolayers linked to the surface through an azobenzene moiety. The redox properties of these electron-rich species tethered to the surface were observed and quantified using cyclic voltammetry. This simple and versatile functionalization procedure has a wide variety of potential applications in surface science and materials research.

Self-Assembled Polystyrene Beads for Templated Covalent Functionalization of Graphitic Substrates Using Diazonium Chemistry.

PubMed

Van Gorp, Hans; Walke, Peter; Bragança, Ana M; Greenwood, John; Ivasenko, Oleksandr; Hirsch, Brandon E; De Feyter, Steven

2018-04-11

A network of self-assembled polystyrene beads was employed as a lithographic mask during covalent functionalization reactions on graphitic surfaces to create nanocorrals for confined molecular self-assembly studies. The beads were initially assembled into hexagonal arrays at the air-liquid interface and then transferred to the substrate surface. Subsequent electrochemical grafting reactions involving aryl diazonium molecules created covalently bound molecular units that were localized in the void space between the nanospheres. Removal of the bead template exposed hexagonally arranged circular nanocorrals separated by regions of chemisorbed molecules. Small molecule self-assembly was then investigated inside the resultant nanocorrals using scanning tunneling microscopy to highlight localized confinement effects. Overall, this work illustrates the utility of self-assembly principles to transcend length scale gaps in the development of hierarchically patterned molecular materials.

Cu(ii)-catalyzed sulfide construction: both aryl groups utilization of intermolecular and intramolecular diaryliodonium salt.

PubMed

Wang, Ming; Wei, Jianpeng; Fan, Qiaoling; Jiang, Xuefeng

2017-03-07

A sulfur-iodine exchange protocol of diaryliodonium salts with inorganic sulfur salt was developed. Both aryl groups in the diaryliodonium salt were fully exerted in this transformation. Five- to eight-membered sulfur-containing heterocycles were achieved. Note that [1]benzothieno-[3,2-b][1]benzothiophene (BTBT) (an organic field-effect transistor (OFET) material) and Zaltoprofen were efficiently established through this method.

Bulk functionalization of graphene using diazonium compounds and amide reaction

NASA Astrophysics Data System (ADS)

Peng, Chang; Xiong, Yuzi; Liu, Zhibo; Zhang, Fan; Ou, Encai; Qian, Jiangtao; Xiong, Yuanqin; Xu, Weijian

2013-09-01

An efficient and convenient method is applied to introduce varieties of simple functionalities onto the graphene surface for the bulk preparation, which begins with pristine graphite that does not require initial oxidative damage of the graphene basal planes. Diazonium compounds functionalized reaction is demonstrated and it successfully prevented the aggregation of graphene for which providing solubility in high polar organic media or even in volatile solvents such as ethanol and acetone. This approach is complemented by the phenyl carboxylic diazonium salt functionalized graphene (PCFG) attachment of a symmetrically substituted zinc phthalocyanine (PCFG-Pc) using the amide reaction, which is used for the covalent introduction of a complex phthalocyanine molecule.

A direct method to visualise the aryl acylamidase activity on cholinesterases in polyacrylamide gels

PubMed Central

Jaganathan, Lakshmanan; Boopathy, Rathanam

2000-01-01

Background In vertebrates, two types of cholinesterases exist, acetylcholinesterase and butyrylcholinesterase. The function of acetylcholinesterase is to hydrolyse acetylcholine, thereby terminating the neurotransmission at cholinergic synapse, while the precise physiological function of butyrylcholinesterase has not been identified. The presence of cholinesterases in tissues that are not cholinergically innervated indicate that cholinesterases may have functions unrelated to neurotransmission. Furthermore, cholinesterases display a genuine aryl acylamidase activity apart from their predominant acylcholine hydrolase activity. The physiological significance of this aryl acylamidase activity is also not known. The study on the aryl acylamidase has been, in part hampered by the lack of a specific method to visualise this activity. We have developed a method to visualise the aryl acylamidase activity on cholinesterase in polyacrylamide gels. Results The o-nitroaniline liberated from o-nitroacetanilide by the action of aryl acylamidase activity on cholinesterases, in the presence of nitrous acid formed a diazonium compound. This compound gave an azo dye complex with N-(1-napthyl)-ethylenediamine, which appeared as purple bands in polyacrylamide gels. Treating the stained gels with trichloroacetic acid followed by Tris-HCl buffer helped in fixation of the stain in the gels. By using specific inhibitors for acetylcholinesterase and butyrylcholinesterase, respectively, differential staining for the aryl acylamidase activities on butyrylcholinesterase and acetylcholinesterase in a sample containing both these enzymes has been demonstrated. A linear relationship between the intensity of colour developed and activity of the enzyme was obtained. Conclusions A novel method to visualise the aryl acylamidase activity on cholinesterases in polyacrylamide gels has been developed. PMID:11231883

A direct method to visualise the aryl acylamidase activity on cholinesterases in polyacrylamide gels.

PubMed

Jaganathan, L; Boopathy, R

2000-01-01

In vertebrates, two types of cholinesterases exist, acetylcholinesterase and butyrylcholinesterase. The function of acetylcholinesterase is to hydrolyse acetylcholine, thereby terminating the neurotransmission at cholinergic synapse, while the precise physiological function of butyrylcholinesterase has not been identified. The presence of cholinesterases in tissues that are not cholinergically innervated indicate that cholinesterases may have functions unrelated to neurotransmission. Furthermore, cholinesterases display a genuine aryl acylamidase activity apart from their predominant acylcholine hydrolase activity. The physiological significance of this aryl acylamidase activity is also not known. The study on the aryl acylamidase has been, in part hampered by the lack of a specific method to visualise this activity. We have developed a method to visualise the aryl acylamidase activity on cholinesterase in polyacrylamide gels. The o-nitroaniline liberated from o-nitroacetanilide by the action of aryl acylamidase activity on cholinesterases, in the presence of nitrous acid formed a diazonium compound. This compound gave an azo dye complex with N-(1-napthyl)-ethylenediamine, which appeared as purple bands in polyacrylamide gels. Treating the stained gels with trichloroacetic acid followed by Tris-HCl buffer helped in fixation of the stain in the gels. By using specific inhibitors for acetylcholinesterase and butyrylcholinesterase, respectively, differential staining for the aryl acylamidase activities on butyrylcholinesterase and acetylcholinesterase in a sample containing both these enzymes has been demonstrated. A linear relationship between the intensity of colour developed and activity of the enzyme was obtained. A novel method to visualise the aryl acylamidase activity on cholinesterases in polyacrylamide gels has been developed.

Nickel-catalyzed amination of aryl chlorides with ammonia or ammonium salts.

PubMed

Green, Rebecca A; Hartwig, John F

2015-03-16

The nickel-catalyzed amination of aryl chlorides to form primary arylamines occurs with ammonia or ammonium sulfate and a well-defined single-component nickel(0) precatalyst containing a Josiphos ligand and an η(2)-bound benzonitrile ligand. This system also catalyzes the coupling of aryl chlorides with gaseous amines in the form of their hydrochloride salts. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A simple approach to patterned protein immobilization on silicon via electrografting from diazonium salt solutions.

PubMed

Flavel, Benjamin S; Gross, Andrew J; Garrett, David J; Nock, Volker; Downard, Alison J

2010-04-01

A highly versatile method utilizing diazonium salt chemistry has been developed for the fabrication of protein arrays. Conventional ultraviolet mask lithography was used to pattern micrometer sized regions into a commercial photoresist on a highly doped p-type silicon (100) substrate. These patterned regions were used as a template for the electrochemical grafting of the in situ generated p-aminobenzenediazonium cation to form patterns of aminophenyl film on silicon. Immobilization of biomolecules was demonstrated by coupling biotin to the aminophenyl regions followed by reaction with fluorescently labeled avidin and visualization with fluorescence microscopy. This simple patterning strategy is promising for future application in biosensor devices.

Optical excitation of carbon nanotubes drives stoichiometric reaction with diazonium salts

NASA Astrophysics Data System (ADS)

Powell, Lyndsey; Piao, Yanmei; Wang, Yuhuang; YuHuang Wang Research Group Team

Covalent chemistry is known to lack the precision required to tailor the physical properties of carbon nanostructures. Here we show that, for the first time, light can be used to drive a typically inefficient reaction with single-walled carbon nanotubes in a more stoichiometric fashion. Specifically, our experimental results suggest that light can enhance the reaction rate of diazonium salt with carbon nanotubes by as much as 35-fold, making possible stoichiometric control of the covalent bonding of a functional group to the sp2 carbon lattice. This light-controlled reaction paves the way for the possibility of highly selective and precise chemistry on single-walled carbon nanotubes and other graphitic nanostructures.

Thiolated graphene - a new platform for anchoring CdSe quantum dots for hybrid heterostructures

NASA Astrophysics Data System (ADS)

Debgupta, Joyashish; Pillai, Vijayamohanan K.

2013-04-01

Effective organization of small CdSe quantum dots on graphene sheets has been achieved by a simple solution exchange with thiol terminated graphene prepared by diazonium salt chemistry. This generic methodology of CdSe QD attachment to any graphene surface has remarkable implications in designing hybrid heterostructures.Effective organization of small CdSe quantum dots on graphene sheets has been achieved by a simple solution exchange with thiol terminated graphene prepared by diazonium salt chemistry. This generic methodology of CdSe QD attachment to any graphene surface has remarkable implications in designing hybrid heterostructures. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr00363a

Understanding and Exploitation of Neighboring Heteroatom Effect for the Mild N-Arylation of Heterocycles with Diaryliodonium Salts under Aqueous Conditions: A Theoretical and Experimental Mechanistic Study.

PubMed

Bihari, Tamás; Babinszki, Bence; Gonda, Zsombor; Kovács, Szabolcs; Novák, Zoltán; Stirling, András

2016-07-01

The mechanism of arylation of N-heterocycles with unsymmetric diaryliodonium salts is elucidated. The fast and efficient N-arylation reaction is interpreted in terms of the bifunctionality of the substrate: The consecutive actions of properly oriented Lewis base and Brønsted acid centers in sufficient proximity result in the fast and efficient N-arylation. The mechanistic picture points to a promising synthetic strategy where suitably positioned nucleophilic and acidic centers enable functionalization, and it is tested experimentally.

An efficient synthesis of bis-1,3-(3'-aryl-N-heterocycl-1'-yl)arenes as CCC-NHC pincer ligand precursors.

PubMed

Howell, Tyler O; Huckaba, Aron J; Hollis, T Keith

2014-05-02

A report that demonstrated an efficient methodology for the arylation of imidazoles has been extended to bis(N-heterocyclic) compounds. Using bis(aryl) iodonium salts provides high-yielding access to CCC-NHC ligand precursors in a single step. Examples of arylation using various iodonium salts are reported herein with an investigation into the factors governing their relative rate of reactivity. The metalation of one of these compounds using Zr(NMe2)4 and its subsequent treatment with [Pt(COD)Cl2] to yield a transmetalated product are reported.

Molecular perspective on diazonium adsorption for controllable functionalization of single-walled carbon nanotubes in aqueous surfactant solutions.

PubMed

Lin, Shangchao; Hilmer, Andrew J; Mendenhall, Jonathan D; Strano, Michael S; Blankschtein, Daniel

2012-05-16

Functionalization of single-walled carbon nanotubes (SWCNTs) using diazonium salts allows modification of their optical and electronic properties for a variety of applications, ranging from drug-delivery vehicles to molecular sensors. However, control of the functionalization process remains a challenge, requiring molecular-level understanding of the adsorption of diazonium ions onto heterogeneous, charge-mobile SWCNT surfaces, which are typically decorated with surfactants. In this paper, we combine molecular dynamics (MD) simulations, experiments, and equilibrium reaction modeling to understand and model the extent of diazonium functionalization of SWCNTs coated with various surfactants (sodium cholate, sodium dodecyl sulfate, and cetyl trimethylammonium bromide). We show that the free energy of diazonium adsorption, determined using simulations, can be used to rank surfactants in terms of the extent of functionalization attained following their adsorption on the nanotube surface. The difference in binding affinities between linear and rigid surfactants is attributed to the synergistic binding of the diazonium ion to the local "hot/cold spots" formed by the charged surfactant heads. A combined simulation-modeling framework is developed to provide guidance for controlling the various sensitive experimental conditions needed to achieve the desired extent of SWCNT functionalization.

Fabrication of superhydrophobic surface on zinc substrate by 3-trifluoromethylbenzene diazonium tetrafluoroborate salts

NASA Astrophysics Data System (ADS)

Li, Hong; Huang, Chengya; Zhang, Long; Lou, Wanqiu

2014-09-01

In this study we report a new and efficient method of fabricating superhydrophobic surface on zinc plate modified with 3-trifluoromethylbenzene diazonium tetrafluoroborate salts (CF3BD), which shows a water contact angle of 160° for a 4 μl water droplet and a low sliding angle of about 1°. The morphology and chemical composition of as-prepared superhydrophobic zinc surfaces are investigated by means of scanning electron microscopy (SEM), electron probe microanalyzer (EPMA) and FT-IR spectrum. The results show that the organic layers formed on zinc plate surface are provided with the special hierarchical porous microstructure and the low surface energy, which lead to the superhydrophobicity surface on the modified zinc.

Direct functionalization of pristine single-walled carbon nanotubes by diazonium-based method with various five-membered S- or N- heteroaromatic amines

NASA Astrophysics Data System (ADS)

Leinonen, Heli; Lajunen, Marja

2012-09-01

Reactivity of five-membered, variously substituted, heteroaromatic diazonium salts was studied toward pristine single-walled carbon nanotubes (SWCNTs), prepared by high-pressure CO conversion (HiPCO) method. Average size range of individual HiPCO SWCNTs was 0.8-1.2 nm (diameter) and 100-1,000 nm (length). Functionalizations were performed by a one-pot diazotization-dediazotization method with methyl-2-aminothiophene-3-carboxylate, 2-aminothiophene-3-carbonitrile, 2-aminoimidazole sulfate, or 3-aminopyrazole in acetic acid using sodium nitrite at room temperature or by heating. According to Raman and Fourier transform infrared spectroscopy, all used heterocyclic diazonium salts formed a covalent bond with SWCNTs and yielded new kinds of five-membered heterocycle-functionalized SWCNTs. Methyl-2-thiophenyl-3-carboxylate-functionalized SWCNTs formed a highly soluble, stable dispersion in tetrahydrofuran (THF), 3-pyrazoyl-functionalized SWCNTs in ethanol, and 2-imidazoyl- or 2-thiophenyl-3-carbonitrile-functionalized SWCNTs in ethanol and THF. The thermogravimetric analysis as well as energy-filtered transmission electron microscopy imaging of the products confirmed the successful functionalization of SWCNTs.

A simple and facile Heck-type arylation of alkenes with diaryliodonium salts using magnetically recoverable Pd-catalyst

EPA Science Inventory

The Heck-type arylation of alkenes was achieved in aqueous polyethylene glycol using a magnetically recoverable heterogenized palladium catalyst employing diaryliodonium salts under ambient conditions. The benign reaction medium and the stability of the catalyst are the salient f...

Copper-catalyzed Green and Expeditious N-Arylation of Sulfoximines using Diaryliodonium Salts

EPA Science Inventory

An ultrasound-accelerated green route for an expeditious N-arylation of NH-sulfoximines is described that involves the use of benign diaryliodonium salts in aqueous polyethylene glycol-400 and copper(I) bromide as catalyst at room temperature. The high yields of the products and...

Fabrication and characterization of graphene/molecule/graphene vertical junctions with aryl alkane monolayers

NASA Astrophysics Data System (ADS)

Jeong, Inho; Song, Hyunwook

2017-11-01

In this study, we fabricated and characterized graphene/molecule/graphene (GMG) vertical junctions with aryl alkane monolayers. The constituent molecules were chemically self-assembled via electrophilic diazonium reactions into a monolayer on the graphene bottom electrode, while the other end physically contacted the graphene top electrode. A full understanding of the transport properties of molecular junctions is a key step in the realization of molecular-scale electronic devices and requires detailed microscopic characterization of the junction's active region. Using a multiprobe approach combining a variety of transport techniques, we elucidated the transport mechanisms and electronic structure of the GMG junctions, including temperature- and length-variable transport measurements, and transition voltage spectroscopy. These results provide criteria to establish a valid molecular junction and to determine the most probable transport characteristics of the GMG junctions.

Crystal structures of five 1-alkyl-4-aryl-1,2,4-triazol-1-ium halide salts.

PubMed

Guino-O, Marites A; Talbot, Meghan O; Slitts, Michael M; Pham, Theresa N; Audi, Maya C; Janzen, Daron E

2015-06-01

The asymmetric units for the salts 4-(4-fluoro-phen-yl)-1-isopropyl-1,2,4-triazol-1-ium iodide, C11H13FN3 (+)·I(-), (1), 1-isopropyl-4-(4-methyl-phen-yl)-1,2,4-triazol-1-ium iodide, C12H16N3 (+)·I(-), (2), 1-isopropyl-4-phenyl-1,2,4-triazol-1-ium iodide, C11H14N3 (+)·I(-), (3), and 1-methyl-4-phenyl-1,2,4-triazol-1-ium iodide, C9H10N3 (+)·I(-), (4), contain one cation and one iodide ion, whereas in 1-benzyl-4-phenyl-1,2,4-triazol-1-ium bromide monohydrate, C15H14N3 (+)·Br(-)·H2O, (5), there is an additional single water mol-ecule. There is a predominant C-H⋯X(halide) inter-action for all salts, resulting in a two-dimensional extended sheet network between the triazolium cation and the halide ions. For salts with para-substitution on the aryl ring, there is an additional π-anion inter-action between a triazolium carbon and iodide displayed by the layers. For salts without the para-substitution on the aryl ring, the π-π inter-actions are between the triazolium and aryl rings. The melting points of these salts agree with the predicted substituent inductive effects.

Induction heating to trigger the nickel surface modification by in situ generated 4-carboxybenzene diazonium

NASA Astrophysics Data System (ADS)

Arrotin, Bastien; Jacques, Amory; Devillers, Sébastien; Delhalle, Joseph; Mekhalif, Zineb

2016-05-01

Nickel is commonly used in numerous applications and is one of the few materials that present strong ferromagnetic properties. These make it a suitable material for induction heating which can be used to activate the grafting of organic species such as diazonium salts onto the material. Diazonium compounds are often used for the modification of metals and alloys thanks to their easy chemical reduction onto the substrates and the possibility to apply a one-step in situ generation process of the diazonium species. This work focuses on the grafting of 4-aminocarboxybenzene on nickel substrates in the context of a spontaneous grafting conducted either at room temperature or by thermal assistance through conventional heating and induction heating. These modifications are also carried out with the goal of maintaining the oxides layer as much as possible unaffected. The benefits of using induction heating with respect to conventional heating are an increase of the grafting rate, a better control of the reaction and a slighter impact on the oxides layer.

Grafting of a peptide probe for Prostate-Specific Antigen detection using diazonium electroreduction and click chemistry.

PubMed

Strzemińska, I; Sainte Rose Fanchine, S; Anquetin, G; Reisberg, S; Noël, V; Pham, M C; Piro, B

2016-07-15

The main objective of this work was to validate a label-free electrochemical method of protein detection using peptides as capture probes. As a proof-of-concept, we used a 7 amino acids sequence (HSSKLQL) specific for Prostate Specific Antigen. We investigated various electrografting conditions of two anilines (2-[(4-aminophenyl)sulfanyl]-8-hydroxy-1,4-naphthoquinone and 4-azidoaniline) further converted in situ into their corresponding diazonium salts on glassy carbon electrodes. It was demonstrated that the best method to obtain a mixed layer is the simultaneous electroreduction of the two diazonium salts. 4-azidoaniline was used to covalently immobilize the ethynyl-functionalized peptide probe by click coupling, and the hydroxynaphthoquinone derivative plays the role of electrochemical transducer of the peptide-protein recognition. The proteolytic activity of PSA towards a small peptide substrate carrying streptavidin at its distal end was also investigated to design an original sensing architecture leading to a reagentless, label free, and "signal-on" PSA sensor. Without optimization, the limit of quantification can be estimated in the nM to pM range. Copyright © 2016 Elsevier B.V. All rights reserved.

Arynes, diaryliodonium salts and azine N-oxides in transition metal-free electrophilic N-arylation

NASA Astrophysics Data System (ADS)

Bugaenko, D. I.; Karchava, A. V.; Yurovskaya, M. A.

2018-03-01

The main approach to the synthesis of aromatic and heteroaromatic amines is based on palladium- and copper-catalyzed N-arylation reactions. Although these methods are highly efficient and provide extensive opportunities for the synthesis of (het)arylamines with various structures and properties, they have some limitations related to the catalysts used and reaction conditions. This review addresses alternative approaches to N-(het)arylation that have been extensively developed in the past decade and are based on the use of arynes, diaryliodonium salts and azine N-oxides as electrophilic (het)arylating agents. Because of mild reaction conditions and no need for catalysts and strong bases, these N-(het)arylation methods are attractive for various synthetic applications and open up new possibilities for the preparation of valuable organic compounds inaccessible via traditional catalytic methods. The attention is focussed on publications of the last decade. The bibliography includes 112 references.

Surface immobilized azomethine for multiple component exchange.

PubMed

Lerond, Michael; Bélanger, Daniel; Skene, W G

2017-09-27

Diazonium chemistry concomitant with in situ electrochemical reduction was used to graft an aryl aldehyde to indium-tin oxide (ITO) coated glass substrates. This served as an anchor for preparing electroactive azomethines that were covalently bonded to the transparent electrode. The immobilized azomethines could undergo multiple step-wise component exchanges with different arylamines. The write-erase-write sequences were electrochemically confirmed. The azomethines could also be reversibly hydrolyzed. This was exploited for multiple azomethine-hydrolysis cycles resulting in discrete electroactive immobilized azomethines. The erase-rewrite sequences were also electrochemically confirmed.

New Method for Super Hydrophobic Treatment of Gas Diffusion Layers for Proton Exchange Membrane Fuel Cells Using Electrochemical Reduction of Diazonium Salts.

PubMed

Thomas, Yohann R J; Benayad, Anass; Schroder, Maxime; Morin, Arnaud; Pauchet, Joël

2015-07-15

The purpose of this article is to report a new method for the surface functionalization of commercially available gas diffusion layers (GDLs) by the electrochemical reduction of diazonium salt containing hydrophobic functional groups. The method results in superhydrophobic GDLs, over a large area, without pore blocking. An X-ray photoelectron spectroscopy study based on core level spectra and chemical mapping has demonstrated the successful grafting route, resulting in a homogeneous distribution of the covalently bonded hydrophobic molecules on the surface of the GDL fibers. The result was corroborated by contact angle measurement, showing similar hydrophobicity between the grafted and PTFE-modified GDLs. The electrochemically modified GDLs were tested in proton exchange membrane fuel cells under automotive, wet, and dry conditions and demonstrated improved performance over traditional GDLs.

Crystal structures of five 1-alkyl-4-aryl-1,2,4-triazol-1-ium halide salts

PubMed Central

Guino-o, Marites A.; Talbot, Meghan O.; Slitts, Michael M.; Pham, Theresa N.; Audi, Maya C.; Janzen, Daron E.

2015-01-01

The asymmetric units for the salts 4-(4-fluoro­phen­yl)-1-isopropyl-1,2,4-triazol-1-ium iodide, C11H13FN3 +·I−, (1), 1-isopropyl-4-(4-methyl­phen­yl)-1,2,4-triazol-1-ium iodide, C12H16N3 +·I−, (2), 1-isopropyl-4-phenyl-1,2,4-triazol-1-ium iodide, C11H14N3 +·I−, (3), and 1-methyl-4-phenyl-1,2,4-triazol-1-ium iodide, C9H10N3 +·I−, (4), contain one cation and one iodide ion, whereas in 1-benzyl-4-phenyl-1,2,4-triazol-1-ium bromide monohydrate, C15H14N3 +·Br−·H2O, (5), there is an additional single water mol­ecule. There is a predominant C—H⋯X(halide) inter­action for all salts, resulting in a two-dimensional extended sheet network between the triazolium cation and the halide ions. For salts with para-substitution on the aryl ring, there is an additional π–anion inter­action between a triazolium carbon and iodide displayed by the layers. For salts without the para-substitution on the aryl ring, the π–π inter­actions are between the triazolium and aryl rings. The melting points of these salts agree with the predicted substituent inductive effects. PMID:26090137

Photoluminescent silicon nanocrystals with chlorosilane surfaces - synthesis and reactivity

NASA Astrophysics Data System (ADS)

Höhlein, Ignaz M. D.; Kehrle, Julian; Purkait, Tapas K.; Veinot, Jonathan G. C.; Rieger, Bernhard

2014-12-01

We present a new efficient two-step method to covalently functionalize hydride terminated silicon nanocrystals with nucleophiles. First a reactive chlorosilane layer was formed via diazonium salt initiated hydrosilylation of chlorodimethyl(vinyl)silane which was then reacted with alcohols, silanols and organolithium reagents. With organolithium compounds a side reaction is observed in which a direct functionalization of the silicon surface takes place.We present a new efficient two-step method to covalently functionalize hydride terminated silicon nanocrystals with nucleophiles. First a reactive chlorosilane layer was formed via diazonium salt initiated hydrosilylation of chlorodimethyl(vinyl)silane which was then reacted with alcohols, silanols and organolithium reagents. With organolithium compounds a side reaction is observed in which a direct functionalization of the silicon surface takes place. Electronic supplementary information (ESI) available: Detailed experimental procedures and additional NMR, PL, EDX, DLS and TEM data. See DOI: 10.1039/C4NR05888G

Electrophoretic Approach for the Simultaneous Deposition and Functionalization of Reduced Graphene Oxide Nanosheets with Diazonium Compounds: Application for Lysozyme Sensing in Serum.

PubMed

Wang, Qian; Vasilescu, Alina; Wang, Qi; Coffinier, Yannick; Li, Musen; Boukherroub, Rabah; Szunerits, Sabine

2017-04-12

Electrophoretic deposition (EPD) of reduced graphene oxide nanosheets (rGO) offers several advantages over other surface coating approaches, including process simplicity, uniformity of the deposited films, and good control of the film thickness. The EPD conditions might also be of interest for the reduction of diazonium salts, which upon the release of N 2 molecules and generation of radicals, can form covalent bonds with the sp 2 hybridized carbon lattice atoms of rGO films. In this work, we report on the coating of gold electrodes in one step with rGO/polyethylenimine (PEI) thin films and their simultaneous modification using different phenyl (Ph) diazonium salt precursors bearing various functionalities such as -B(OH) 2 , -COOH, and -C≡CH. We show further the interest of such interfaces for designing highly sensitive sensing platforms. Azide-terminated lysozyme aptamers were clicked onto the rGO/PEI/Ph-alkynyl matrix and used for the sensing of lysozyme levels in patients suffering from inflammatory bowel disease (IBD), where lysozyme levels are up-regulated. The approach attained the required demand for the determination of lysozyme level in patients suffering from IBD with a 200 fM detection limit and a linear range up to 20 pM without signal amplification.

One-pot in situ mixed film formation by azo coupling and diazonium salt electrografting.

PubMed

Esnault, Charles; Delorme, Nicolas; Louarn, Guy; Pilard, Jean-François

2013-06-24

So simple: The in situ synthesis of an aryldiazonium salt and an azo-aryldiazonium salt by azo coupling from sulfanilic acid and aniline is reported. Formation of a mixed organic layer is monitored by cyclic voltammetry and atomic force microscopy. A compact mixed layer is obtained with a global roughness of 0.4 nm and 10-15 % vertical extension in the range 1.5-6 nm. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Diazonium modification of porous graphitic carbon with catechol and amide groups for hydrophilic interaction and attenuated reversed phase liquid chromatography.

PubMed

Iverson, Chad D; Zhang, Ya; Lucy, Charles A

2015-11-27

Porous graphitic carbon (PGC) is an increasingly popular and attractive phase for HPLC on account of its chemical and thermal stability, and its unique separation mechanism. However, native PGC is strongly hydrophobic and in some instances excessively retentive. As part of our effort to build a library of hydrophilic covalently modified PGC phases, we functionalized PGC with catechol and amide groups by means of aryl diazonium chemistry to produce two new phases. Successful grafting was confirmed by X-ray photoelectron spectroscopy (XPS). Under HILIC conditions, the Catechol-PGC showed up to 5-fold increased retention relative to unmodified PGC and selectivity that differed from four other HILIC phases. Under reversed phase conditions, the Amide-PGC reduced the retentivity of PGC by almost 90%. The chromatographic performance of Catechol-PGC and Amide-PGC is demonstrated by separations of nucleobases, nucleosides, phenols, alkaline pharmaceuticals, and performance enhancing stimulants. These compounds had retention factors (k) ranging from 0.5 to 13. Copyright © 2015 Elsevier B.V. All rights reserved.

Comparing phenolic concentration using folin-ciocalteu and fast blue BB diazonium salt

USDA-ARS?s Scientific Manuscript database

Polyphenolics contribute to antioxidant properties of food, juices, and beverages, and are essential to the human diet. These phytochemicals have various preventive and disease fighting properties. The polyphenolics contribute to antioxidant properties and these compounds include flavonoids, flavon...

Electrochemiluminescent DNA sensor based on controlled Zn-mediated grafting of diazonium precursors.

PubMed

Torréns, Mabel; Ortiz, Mayreli; Bejarano-Nosas, Diego; O'Sullivan, Ciara K

2015-07-01

Controlled Zn-mediated grafting of a thin layer of a diazonium salt was used to functionalise a carbon electrode with ruthenium(II)-tris-bipyridine (Ru)-labelled DNA for use as a capture probe in an electrochemiluminescent genosensor. A secondary reporter probe was labelled with a ferrocene (Fc) molecule, and in the presence of the single-stranded DNA target a genocomplex formed, where the Fc-label effectively quenched the electrochemiluminescence of the signal emitted from the Ru-label. The spacing of the labels for maximum sensitivity and minimum detection limit was optimised, and the signal reproducibility and stability of the method was established.

The Synthesis of Methyl Salicylate: Amine Diazotization.

ERIC Educational Resources Information Center

Zanger, Murray; McKee, James R.

1988-01-01

Notes that this experiment takes safety and noncarcinogenic reactants into account. Demonstrates the use of diazonium salts for the replacement of an aromatic amine group by a phenolic hydroxyl. Involves two pleasant-smelling organic compounds, methyl anthranilate (grape) and methyl salicylate (oil of wintergreen). (MVL)

Understanding and controlling the substrate effect on graphene electron-transfer chemistry via reactivity imprint lithography

NASA Astrophysics Data System (ADS)

Wang, Qing Hua; Jin, Zhong; Kim, Ki Kang; Hilmer, Andrew J.; Paulus, Geraldine L. C.; Shih, Chih-Jen; Ham, Moon-Ho; Sanchez-Yamagishi, Javier D.; Watanabe, Kenji; Taniguchi, Takashi; Kong, Jing; Jarillo-Herrero, Pablo; Strano, Michael S.

2012-09-01

Graphene has exceptional electronic, optical, mechanical and thermal properties, which provide it with great potential for use in electronic, optoelectronic and sensing applications. The chemical functionalization of graphene has been investigated with a view to controlling its electronic properties and interactions with other materials. Covalent modification of graphene by organic diazonium salts has been used to achieve these goals, but because graphene comprises only a single atomic layer, it is strongly influenced by the underlying substrate. Here, we show a stark difference in the rate of electron-transfer reactions with organic diazonium salts for monolayer graphene supported on a variety of substrates. Reactions proceed rapidly for graphene supported on SiO2 and Al2O3 (sapphire), but negligibly on alkyl-terminated and hexagonal boron nitride (hBN) surfaces, as shown by Raman spectroscopy. We also develop a model of reactivity based on substrate-induced electron-hole puddles in graphene, and achieve spatial patterning of chemical reactions in graphene by patterning the substrate.

Effect of doping on the modification of polycrystalline silicon by spontaneous reduction of diazonium salts

NASA Astrophysics Data System (ADS)

Girard, A.; Coulon, N.; Cardinaud, C.; Mohammed-Brahim, T.; Geneste, F.

2014-09-01

The chemical modification of doped polycrystalline silicon materials (N+, N++ and P++) and silicon (1 0 0) and (1 1 1) used as references is investigated by spontaneous reduction of diazonium salts. The effectiveness of the grafting process on all polySi surfaces is shown by AFM and XPS analyses. The effect of substrate doping on the efficiency of the electrografting process is compared by using the thicknesses of the deposited organic films. For a better accuracy, two methods are used to estimate the thicknesses: XPS and the coupling of a O2 plasma etching with AFM measurement. Structural characteristics of the poly-Si films were investigated by Scanning Electron Microscopy and X-ray diffraction to find a correlation between the structure of the material and its reactivity. Different parameters that could have an impact on the efficiency of the grafting procedure are discussed. The observed differences between differently doped silicon surfaces is rather limited, this is in agreement with the radical character of the reacting species.

Mild and selective base-free C–H arylation of heteroarenes: experiment and computation† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c6sc02595a Click here for additional data file.

PubMed Central

Gemoets, Hannes P. L.; Kalvet, Indrek; Nyuchev, Alexander V.; Erdmann, Nico; Hessel, Volker

2017-01-01

A mild and selective C–H arylation strategy for indoles, benzofurans and benzothiophenes is described. The arylation method engages aryldiazonium salts as arylating reagents in equimolar amounts. The protocol is operationally simple, base free, moisture tolerant and air tolerant. It utilizes low palladium loadings (0.5 to 2.0 mol% Pd), short reaction times, green solvents (EtOAc/2-MeTHF or MeOH) and is carried out at room temperature, providing a broad substrate scope (47 examples) and excellent selectivity (C-2 arylation for indoles and benzofurans, C-3 arylation for benzothiophenes). Mechanistic experiments and DFT calculations support a Heck–Matsuda type coupling mechanism. PMID:28451243

Gold Redox Catalysis through Base-Initiated Diazonium Decomposition toward Alkene, Alkyne, and Allene Activation.

PubMed

Dong, Boliang; Peng, Haihui; Motika, Stephen E; Shi, Xiaodong

2017-08-16

The discovery of photoassisted diazonium activation toward gold(I) oxidation greatly extended the scope of gold redox catalysis by avoiding the use of a strong oxidant. Some practical issues that limit the application of this new type of chemistry are the relative low efficiency (long reaction time and low conversion) and the strict reaction condition control that is necessary (degassing and inert reaction environment). Herein, an alternative photofree condition has been developed through Lewis base induced diazonium activation. With this method, an unreactive Au I catalyst was used in combination with Na 2 CO 3 and diazonium salts to produce a Au III intermediate. The efficient activation of various substrates, including alkyne, alkene and allene was achieved, followed by rapid Au III reductive elimination, which yielded the C-C coupling products with good to excellent yields. Relative to the previously reported photoactivation method, our approach offered greater efficiency and versatility through faster reaction rates and broader reaction scope. Challenging substrates such as electron rich/neutral allenes, which could not be activated under the photoinitiation conditions (<5 % yield), could be activated to subsequently yield the desired coupling products in good to excellent yield. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

A Modular Flow Design for the meta‐Selective C−H Arylation of Anilines

PubMed Central

Gemoets, Hannes P. L.; Laudadio, Gabriele; Verstraete, Kirsten; Hessel, Volker

2017-01-01

Abstract Described herein is an effective and practical modular flow design for the meta‐selective C−H arylation of anilines. The design consists of four continuous‐flow modules (i.e., diaryliodonium salt synthesis, meta‐selective C−H arylation, inline copper extraction, and aniline deprotection) which can be operated either individually or consecutively to provide direct access to meta‐arylated anilines. With a total residence time of 1 hour, the desired product could be obtained in high yield and excellent purity without the need for column chromatography, and the residual copper content meets the standards for parenterally administered pharmaceutical substances. PMID:28543979

Carbon nanotube-poly(methyl methacrylate) hybrid films: preparation using diazonium salt chemistry and mechanical properties.

PubMed

Mammeri, Fayna; Teyssandier, Joan; Darche-Dugaret, Clément; Debacker, Sabine; Le Bourhis, Eric; Chehimi, Mohamed Mehdi

2014-11-01

The poor miscibility of carbon nanotubes (CNTs) in common organic solvents and organic monomers requires their modification by suitable functional (reactive or not) groups prior to their incorporation in thermoplastic polymers. Dispersion behavior of carbon nanotubes and mechanical properties of various CNT-poly(methylmethacrylate) (PMMA) nanocomposites were investigated. We studied the influence of the surface chemistry through the use of diazonium salts as an elegant and environmentally friendly platform to provide a suitable sidewall functionalization by methyl methacrylate functions. We used either a molecular size functional group through the grafting of methacryloxypropyltrimethoxysilane or a macromolecular size one, consisting in PMMA brushes grown by SI-ATRP in order to study the influence of the length of methacrylate function on the dispersion of CNT in PMMA. The hardness and the elastic indentation modulus of all hybrid films were obtained through nanoindentation measurements and found to increase, using ATRP-modified CNTs, suggesting a better dispersion of CNTs in PMMA due to optimal inorganic-organic interactions promoted by the short chains of PMMA. Copyright © 2014 Elsevier Inc. All rights reserved.

Indium tin oxide with zwitterionic interfacial design for biosensing applications in complex matrices

NASA Astrophysics Data System (ADS)

Darwish, Nadia T.; Alias, Yatimah; Khor, Sook Mei

2015-01-01

Biosensing interfaces consisting of linker molecules (COOH or NH2) and charged, antifouling moieties ((sbnd SO3- and N+(Me)3) for biosensing applications were prepared for the first time by the in situ deposition of mixtures of aryl diazonium cations on indium tin oxide (ITO) electrodes. A linker molecule is required for the attachment of biorecognition molecules (e.g., antibodies, enzymes, DNA chains, and aptamers) close to the transducer surface. The attached molecules improve the biosensing sensitivity and also provide a short response time for analyte detection. Thus, the incorporation of a linker and antifouling molecules is an important interfacial design for both affinity and enzymatic biosensors. The reductive adsorption behavior and electrochemical measurement were studied for (1) an individual compound and (2) a mixture of antifouling zwitterionic molecules together with linker molecules [combination 1: 4-sulfophenyl (SP), 4-trimethylammoniophenyl (TMAP), and 1,4-phenylenediamine (PPD); combination 2: 4-sulfophenyl (SP), 4-trimethylammoniophenyl (TMAP), and 4-aminobenzoic acid (PABA)] of aryl diazonium cations grafted onto an ITO electrode. The mixture ratios of SP:TMAP:PPD and SP:TMAP:PABA that provided the greatest resistance to non-specific protein adsorptions of bovine serum albumin labeled with fluorescein isothiocyanate (BSA-FITC) and cytochrome c labeled with rhodamine B isothiocyanate (RBITC-Cyt c) were determined by confocal laser scanning microscopy (CLSM). For the surface antifouling study, we used 2-[2-(2-methoxyethoxy) ethoxy]acetic acid (OEG) as a standard control because of its prominent antifouling properties. Surface compositions of combinations 1 and 2 were characterized using X-ray photoelectron spectroscopy (XPS). Field-emission scanning electron microscopy (FE-SEM) was used to characterize the morphology of the grafted films to confirm the even distribution between linker and antifouling molecules grafted onto the ITO surfaces. Combination 1 (SP:TMAP:PPD) with a ratio of 0.5:1.5:0.37 exhibited the best antifouling capability with respect to resisting the nonspecific adsorption of proteins.

A Modular Flow Design for the meta-Selective C-H Arylation of Anilines.

PubMed

Gemoets, Hannes P L; Laudadio, Gabriele; Verstraete, Kirsten; Hessel, Volker; Noël, Timothy

2017-06-12

Described herein is an effective and practical modular flow design for the meta-selective C-H arylation of anilines. The design consists of four continuous-flow modules (i.e., diaryliodonium salt synthesis, meta-selective C-H arylation, inline copper extraction, and aniline deprotection) which can be operated either individually or consecutively to provide direct access to meta-arylated anilines. With a total residence time of 1 hour, the desired product could be obtained in high yield and excellent purity without the need for column chromatography, and the residual copper content meets the standards for parenterally administered pharmaceutical substances. © 2017 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

Copper-Mediated Formation of Aryl, Heteroaryl, Vinyl and Alkynyl Difluoromethylphosphonates: A General Approach to Fluorinated Phosphate Mimics.

PubMed

Ivanova, Maria V; Bayle, Alexandre; Besset, Tatiana; Poisson, Thomas; Pannecoucke, Xavier

2015-11-02

A general and efficient access to aryl, heteroaryl, vinyl and alkynyl difluoromethylphosphonates is described. The developed methodology using TMSCF2PO(OEt)2, iodonium salts and a copper salt provided a straightforward manifold to reach these highly relevant products. The reaction proved to be highly functional group tolerant and proceeded under mild conditions, giving the corresponding products in good to excellent yields. This method represents the first general synthetic route to this important class of fluorinated scaffolds, which are well-recognized as in vivo stable phosphate surrogates. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis of substituted pyrazines

DOEpatents

Pagoria, Philip F.; Zhang, Mao Xi

2016-10-04

A method for synthesizing a pyrazine-containing material according to one embodiment includes contacting an iminodiacetonitrile derivative with a base and a reagent selected from a group consisting of hydroxylamine, a hydroxylamine salt, an aliphatic primary amine, a secondary amine, an aryl-substituted alkylamine a heteroaryl-substituted alkyl amine, an alcohol, an alkanolamine and an aryl alcoholamine. Additional methods and several reaction products are presented. ##STR00001##

Functionalization of magnetic nanocrystals by oligo (ethylene oxide) chains carrying diazonium and iniferter end groups.

PubMed

Ahmad, Randa; Griffete, Nébéwia; Lamouri, Aazdine; Mangeney, Claire

2013-10-01

The water stability of iron oxide nanoparticles (NPs) is a major issue for biomedical and biological applications. This paper presents a versatile approach for preparing water-soluble iron oxide nanoparticles coated by bifunctional oligo(ethylene oxide) (OEO) chains, carrying on the one side a diazonium end group for covalent grafting at the NP surface and on the other side an iniferter group (diethyl dithiocarbamate) for initiating the growing of poly(methacrylic acid). The nanoparticles were synthesized by coprecipitation in basic media and functionalized in situ by adding the diazonium salt directly in the synthesis medium. Oligo(ethylene oxide) with various chain lengths (from one to three monomer units) was grafted at the NP surface using this approach. The length of the OEO spacer between the NP surface and the iniferter end group was found to be a critical parameter for controlling the colloidal stability of the hybrid NPs. The polymerization time was also shown to strongly influence their colloidal stability, emphasizing the interest to control the interfacial properties of the hybrids for obtaining stable dispersions in water. Copyright © 2013 Elsevier Inc. All rights reserved.

One-pot formation of 1,3,4-oxadiazol-2(3H)-ones and dibenzo[c,e]azepines by concomitant cathodic reduction of diazonium salts and phenanthrenequinones.

PubMed

Batanero, Belen; Barba, Fructuoso; Martin, Avelino

2013-09-20

The one-pot concomitant electrochemical reduction of phenanthrenequinones (1, 2) and arenediazonium salts (3a-f) led to the formation of 1,3,4-oxadiazol-2(3H)-ones (4a-f, 5a) and dibenzo[c,e]azepines (6a-f) when N-methylformamide was used as the solvent. A new pathway, different from those previously described with other aprotic solvents, is proposed. The experimental data support a radical mechanism for the electrochemical process followed by an internal rearrangement to give the products.

Salt Effect Accelerates Site-Selective Cysteine Bioconjugation

PubMed Central

2016-01-01

Highly efficient and selective chemical reactions are desired. For small molecule chemistry, the reaction rate can be varied by changing the concentration, temperature, and solvent used. In contrast for large biomolecules, the reaction rate is difficult to modify by adjusting these variables because stringent biocompatible reaction conditions are required. Here we show that adding salts can change the rate constant over 4 orders of magnitude for an arylation bioconjugation reaction between a cysteine residue within a four-residue sequence (π-clamp) and a perfluoroaryl electrophile. Biocompatible ammonium sulfate significantly enhances the reaction rate without influencing the site-specificity of π-clamp mediated arylation, enabling the fast synthesis of two site-specific antibody–drug conjugates that selectively kill HER2-positive breast cancer cells. Computational and structure–reactivity studies indicate that salts may tune the reaction rate through modulating the interactions between the π-clamp hydrophobic side chains and the electrophile. On the basis of this understanding, the salt effect is extended to other bioconjugation chemistry, and a new regioselective alkylation reaction at π-clamp cysteine is developed. PMID:27725962

Synthesis and immobilization of Ag(0) nanoparticles on diazonium modified electrodes: SECM and cyclic voltammetry studies of the modified interfaces.

PubMed

Noël, Jean-Marc; Zigah, Dodzi; Simonet, Jacques; Hapiot, Philippe

2010-05-18

A versatile method was used to prepare modified surfaces on which metallic silver nanoparticles are immobilized on an organic layer. The preparation method takes advantage, on one hand, of the activated reactivity of some alkyl halides with Ag-Pd alloys to produce metallic silver nanoparticles and, on the other hand, of the facile production of an anchoring polyphenyl acetate layer by the electrografting of substituted diazonium salts on carbon surfaces. Transport properties inside such modified layers were investigated by cyclic voltammetry, scanning electrochemical microscopy (SECM) in feedback mode, and conducting AFM imaging for characterizing the presence and nature of the conducting pathways. The modification of the blocking properties of the surface (or its conductivity) was found to vary to a large extent on the solvents used for surface examination (H(2)O, CH(2)Cl(2), and DMF).

Determination of bilirubin glucuronide and assay of glucuronyltransferase with bilirubin as acceptor

PubMed Central

Van Roy, F. P.; Heirwegh, K. P. M.

1968-01-01

1. Conjugated bilirubin is conveniently determined by coupling with the diazonium salt of ethyl anthranilate. 2. This method has been used in the development of assays for UDP-glucuronyltransferase (EC 2.4.1.17), with bilirubin as substrate, in rat liver homogenates, microsomal preparations and partly purified fractions. 3. Chromatographic analysis suggests that bilirubin monoglucuronide is the product of the enzyme systems studied. PMID:5660631

Trace lead analysis based on carbon-screen-printed-electrodes modified via 4-carboxy-phenyl diazonium salt electroreduction.

PubMed

Bouden, Sarra; Chaussé, Annie; Dorbes, Stephane; El Tall, Omar; Bellakhal, Nizar; Dachraoui, Mohamed; Vautrin-Ul, Christine

2013-03-15

This paper describes the use of 4-carboxyphenyl-grafted screen-printed carbon electrodes (4-CP-SPEs) for trace lead analysis. These novel and simple use of electrodes were easily prepared by the electrochemical reduction of the corresponding diazonium salt. Pb detection was then performed by a three-steps method in order to avoid oxygen interference: (i) immersion of the grafted screen-printed electrode (SPE) in the sample and adsorption of Pb(II), (ii) reduction of adsorbed Pb(II) by chronoamperometry (CA), and (iii) oxidation of Pb by Anodic Square Wave Voltammetry (SWV). The reoxidation response was exploited for lead detection and quantification. In order to optimize the analytical responses, the influence of the adsorption medium pH and the adsorption time were investigated. Moreover, an interference study was carried out with Cu(II), Hg(II), Al(III), Mn(II), Zn(II), Cd(II) and no major interference can be expected to quantify Pb(II). The described method provided a limit of detection and a limit of quantification of 1.2 × 10(-9)M and 4.1 × 10(-9)M, respectively. These performances indicate that the 4-CP-SPE could be considered as an efficient tool for environmental analysis. Copyright © 2013 Elsevier B.V. All rights reserved.

Electrochemical immunosensor for ethinylestradiol using diazonium salt grafting onto silver nanoparticles-silica-graphene oxide hybrids.

PubMed

Cincotto, Fernando H; Martínez-García, Gonzalo; Yáñez-Sedeño, Paloma; Canevari, Thiago C; Machado, S A S; Pingarrón, José M

2016-01-15

This work describes the preparation of an electrochemical immunosensor for ethinylestradiol (EE2) based on grafting of diazonium salt of 4-aminobenzoic acid onto a glassy carbon electrode modified with silver nanoparticles/SiO2/graphene oxide hybrid followed by covalent binding of anti-ethinylestradiol (anti-EE2) to activated carboxyl groups. A competitive immunoassay was developed for the determination of the hormone using peroxidase-labeled ethinylestradiol (HRP-EE2) and measurement of the amperometric response at -200mV in the presence of hydroquinone (HQ) as redox mediator. The calibration curve for EE2 exhibited a linear range between 0.1 and 50ng/mL (r(2)=0.996), with a detection limit of 65pg/mL. Interference studies with other hormones related with EE2 revealed the practical specificity of the developed method for the analyte. A good reproducibility, with RSD=4.5% (n=10) was also observed. The operating stability of a single bioelectrode modified with anti-EE2 was maintained at least for 15 days when it was stored at 4°C under humid conditions between measurements. The developed immunosensor was applied to the analysis of spiked urine with good results. Copyright © 2015 Elsevier B.V. All rights reserved.

Palladium-Catalyzed α-Arylation of 2-Chloroacetates and 2-Chloroacetamides

PubMed Central

Traister, Kaitlin M.; Barcellos, Thiago

2013-01-01

A method has been developed for the Pd-catalyzed synthesis of α-(hetero)aryl esters and amides through a Suzuki–Miyaura cross-coupling reaction. This method avoids the use of strong base, does not necessitate inert or low temperature formation of reagents, and does not require the use of a large excess of organometallic reagent. Utilization of organotrifluoroborate salts as nucleophilic partners allows a variety of functional groups and heterocyclic compounds to be tolerated. PMID:23570264

Computational and experimental investigations of one-step conversion of poly(carbonate)s into value-added poly(aryl ether sulfone)s

PubMed Central

Yuen, Alexander; Wojtecki, Rudy J.; Hedrick, James L.; García, Jeannette M.

2016-01-01

It is estimated that ∼2.7 million tons poly(carbonate)s (PCs) are produced annually worldwide. In 2008, retailers pulled products from store shelves after reports of bisphenol A (BPA) leaching from baby bottles, reusable drink bottles, and other retail products. Since PCs are not typically recycled, a need for the repurposing of the PC waste has arisen. We report the one-step synthesis of poly(aryl ether sulfone)s (PSUs) from the depolymerization of PCs and in situ polycondensation with bis(aryl fluorides) in the presence of carbonate salts. PSUs are high-performance engineering thermoplastics that are commonly used for reverse osmosis and water purification membranes, medical equipment, as well as high temperature applications. PSUs generated through this cascade approach were isolated in high purity and yield with the expected thermal properties and represent a procedure for direct conversion of one class of polymer to another in a single step. Computational investigations performed with density functional theory predict that the carbonate salt plays two important catalytic roles in this reaction: it decomposes the PCs by nucleophilic attack, and in the subsequent polyether formation process, it promotes the reaction of phenolate dimers formed in situ with the aryl fluorides present. We envision repurposing poly(BPA carbonate) for the production of value-added polymers. PMID:27354514

Computational and experimental investigations of one-step conversion of poly(carbonate)s into value-added poly(aryl ether sulfone)s.

PubMed

Jones, Gavin O; Yuen, Alexander; Wojtecki, Rudy J; Hedrick, James L; García, Jeannette M

2016-07-12

It is estimated that ∼2.7 million tons poly(carbonate)s (PCs) are produced annually worldwide. In 2008, retailers pulled products from store shelves after reports of bisphenol A (BPA) leaching from baby bottles, reusable drink bottles, and other retail products. Since PCs are not typically recycled, a need for the repurposing of the PC waste has arisen. We report the one-step synthesis of poly(aryl ether sulfone)s (PSUs) from the depolymerization of PCs and in situ polycondensation with bis(aryl fluorides) in the presence of carbonate salts. PSUs are high-performance engineering thermoplastics that are commonly used for reverse osmosis and water purification membranes, medical equipment, as well as high temperature applications. PSUs generated through this cascade approach were isolated in high purity and yield with the expected thermal properties and represent a procedure for direct conversion of one class of polymer to another in a single step. Computational investigations performed with density functional theory predict that the carbonate salt plays two important catalytic roles in this reaction: it decomposes the PCs by nucleophilic attack, and in the subsequent polyether formation process, it promotes the reaction of phenolate dimers formed in situ with the aryl fluorides present. We envision repurposing poly(BPA carbonate) for the production of value-added polymers.

N-aryl pyrrolo-tetrathiafulvalene based ligands: synthesis and metal coordination.

PubMed

Balandier, Jean-Yves; Chas, Marcos; Dron, Paul I; Goeb, Sébastien; Canevet, David; Belyasmine, Ahmed; Allain, Magali; Sallé, Marc

2010-03-05

A straightforward general synthetic access to N-aryl-1,3-dithiolo[4,5-c]pyrrole-2-thione derivatives 6 from acetylenedicarbaldehyde monoacetal is depicted. In addition to their potentiality as precursors to dithioalkyl-pyrrole derivatives, thiones 6 are key building blocks to N-aryl monopyrrolo-tetrathiafulvalene (MPTTF) derivatives 10. X-ray structures of four of these thiones intermediates, reminiscent of the corresponding MPTTF derivatives, are provided. When the aryl group is a binding pyridyl unit, the MPTTF derivative 10a can coordinate M(II) salts (M = Pt, Pd). The first examples of metal-directed orthogonal MPTTF-based dimers 11-14, obtained through coordination of 10a to cis-blocked square planar Pt or Pd complexes are described. Studies on the parameters influencing the dimer construction are presented, as well as first recognition properties of the resulting electron-rich clip for C(60).

Synthesis of oxazolines and oxazines

DOEpatents

Benicewicz, Brian C.; Mitchell, Michael A.

1995-01-01

A process of preparing an oxazoline or oxazine compound of the formula ##STR1## wherein X is an atom selected from the group of oxygen and sulfur, R is selected from the group consisting of C.sub.1-10 alkyl, C.sub.1-10 fluoroalkyl, aryl and substituted-aryl, and n is 2 or 3 comprising ring-closing a compound of the formula ##STR2## wherein X is an atom selected from the group of oxygen and sulfur, R is selected from the group consisting of C.sub.1-10 alkyl, C.sub.1-10 fluoroalkyl, aryl, and substituted aryl, n is 2 or 3, and Y is a bromine or chlorine atom in the presence of a basic reagent consisting essentially of a fluoride salt supported on an inorganic solid substrate is disclosed together with the compounds, 5-bromomethyl-2-phenyl-1,3-oxazoline, 5-methylene-2-phenyl-1,3-oxazine and 4,4-dimethyl-2-vinyl-1,3-oxazoline.

Organocatalytic C-H bond arylation of aldehydes to bis-heteroaryl ketones.

PubMed

Toh, Qiao Yan; McNally, Andrew; Vera, Silvia; Erdmann, Nico; Gaunt, Matthew J

2013-03-13

An organocatalytic aldehyde C-H bond arylation process for the synthesis of complex heteroaryl ketones has been developed. By exploiting the inherent electrophilicity of diaryliodonium salts, we have found that a commercial N-heterocyclic carbene catalyst promotes the union of heteroaryl aldehydes and these heteroaromatic electrophile equivalents in good yields. This straightforward catalytic protocol offers access to ketones bearing a diverse array of arene and heteroarene substituents that can subsequently be converted into molecules displaying structural motifs commonly found in medicinal agents.

Selective chloroform sensor using thiol functionalized reduced graphene oxide at room temperature

NASA Astrophysics Data System (ADS)

Midya, Anupam; Mukherjee, Subhrajit; Roy, Shreyasee; Santra, Sumita; Manna, Nilotpal; Ray, Samit K.

2018-02-01

This paper presents a highly selective chloroform sensor using functionalised reduced graphene oxide (RGO) as a sensing layer. Thiol group is covalently attached on the basal plan of RGO film by a simple one-step aryl diazonium chemistry to improve its selectivity. Several spectroscopic techniques like X-ray photoelectron, Raman and Fourier transform infrared spectroscopy confirm successful thiol functionalization of RGO. Finally, the fabricated chemiresistor type sensor is exposed to chloroform in the concentration range 200-800 ppm (parts per million). The sensor shows a 4.3% of response towards 800 ppm chloroform. The selectivity of the sensor is analyzed using various volatile organic compounds as well. The devices show enhanced response and faster recovery attributed to the physiosorption of chloroform onto thiol functionalized graphene making them attractive for 2D materials based sensing applications.

The Comparative Nucleophilicity of Naphthoxide Derivatives in Reactions with a Fast-Red TR Dye: A Discovery-Oriented Capstone Project for the Second-Year Organic Laboratory

ERIC Educational Resources Information Center

Mascarenhas, Cheryl M.

2008-01-01

In this experiment, organic chemistry students perform reactions between three naphthyl acetate derivatives and the diazonium salt Fast-Red TR, under basic conditions. The three naphthyl acetate derivatives used in this study are 2-naphthyl acetate (1a), 6-bromo-2-naphthyl acetate (1b) and 1,6-dibromo-2-naphthyl acetate (1c). The two-step, one-pot…

Modification of Ti6Al4V surface by diazonium compounds

NASA Astrophysics Data System (ADS)

Sandomierski, Mariusz; Buchwald, Tomasz; Strzemiecka, Beata; Voelkel, Adam

2018-02-01

Ti6Al4V alloy is the most commonly used in orthopedic industry as an endoprosthesis. Ti6Al4V exhibits good mechanical properties, except the abrasion resistance. Surface modification of Ti6Al4V in order to obtain organic layer, and then the attachment of the polymer, can allow for overcoming this problem. The aim of the work was the modification of Ti6Al4V surface by diazonium compounds: salt or cation generated in situ and examine the influence of the reducing agent - ascorbic acid, and the temperature of reaction on modification process. Moreover, the simulated body fluid was used for the assessment of the organic layer stability on Ti6Al4V surface. The evaluation of the modification was carried out using the following methods: Raman microspectroscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy. Higher temperature of modification by 4-hydroxymethylbenzenediazonium cation, provides the largest amount of organic layer on the Ti6Al4V alloy. In the case of the Ti6Al4V modified by Variamine Blue B salt, the amount of organic layer is not dependent on the reaction condition. Moreover, the ascorbic acid and the presence of TiO2 does not effect on the modification. The modified surface is completely coated with the organic layer which is stable in simulated body fluid.

Preparation of sulfonic-functionalized graphene oxide as ion-exchange material and its application into electrochemiluminescence analysis.

PubMed

Chen, Guifen; Zhai, Shengyong; Zhai, Yanling; Zhang, Ke; Yue, Qiaoli; Wang, Lei; Zhao, Jinsheng; Wang, Huaisheng; Liu, Jifeng; Jia, Jianbo

2011-03-15

Graphene oxide (GO) obtained from chemical oxidation of flake graphite was derivatized with sulfonic groups to form sulfonic-functionalized GO (GO-SO(3)(-)) through four sulfonation routes: through amide formation between the carboxylic group of GO and amine of sulfanilic acid (AA-GO-SO(3)(-)), aryl diazonium reaction of sulfanilic acid (AD-GO-SO(3)(-)), amide formation between the carboxylic group of GO and amine of cysteamine and oxidation by H(2)O(2) (CA-GO-SO(3)(-)), and alkyl diazonium reaction of cysteamine and oxidation by H(2)O(2) (CD-GO-SO(3)(-)). Results of Fourier transform infrared spectroscopy and X-ray photoelectrospectrocopy showed that -SO(3)(-) groups were attached onto GO. Thermo gravimetric analysis showed that derivatization with sulfonic groups improved thermo stability of GO. X-ray diffraction results indicated that GO-SO(3)(-) had more ordered π-π stacking structure than the original GO. GO-SO(3)(-) and cationic polyelectrote, poly (diallyldimethylammoniumchloride) (PDDA) were adsorbed at indium tin oxide (ITO) glass surface through layer-by-layer assembling to form (GO-SO(3)(-)/PDDA)(n)/ITO multilayers. After tris-(2,2'-bipyridyl) ruthenium (II) dichloride (Ru(bpy)(3)(2+)) was incorporated into the multilayers, the obtained Ru(bpy)(3)(2+)/(GO-SO(3)(-)/PDDA)(n)/ITO electrodes can be used as electrochemiluminescence sensors for detection of organic amine with high sensitivity (limit of detection of 1 nM) and stability. Copyright © 2010 Elsevier B.V. All rights reserved.

Simple diazonium chemistry to develop specific gene sensing platforms.

PubMed

Revenga-Parra, M; García-Mendiola, T; González-Costas, J; González-Romero, E; Marín, A García; Pau, J L; Pariente, F; Lorenzo, E

2014-02-27

A simple strategy for covalent immobilizing DNA sequences, based on the formation of stable diazonized conducting platforms, is described. The electrochemical reduction of 4-nitrobenzenediazonium salt onto screen-printed carbon electrodes (SPCE) in aqueous media gives rise to terminal grafted amino groups. The presence of primary aromatic amines allows the formation of diazonium cations capable to react with the amines present at the DNA capture probe. As a comparison a second strategy based on the binding of aminated DNA capture probes to the developed diazonized conducting platforms through a crosslinking agent was also employed. The resulting DNA sensing platforms were characterized by cyclic voltammetry, electrochemical impedance spectroscopy and spectroscopic ellipsometry. The hybridization event with the complementary sequence was detected using hexaamineruthenium (III) chloride as electrochemical indicator. Finally, they were applied to the analysis of a 145-bp sequence from the human gene MRP3, reaching a detection limit of 210 pg μL(-1). Copyright © 2014 Elsevier B.V. All rights reserved.

Synthesis and antibacterial properties of water-dispersible silver nanoparticles stabilized by metal-carbon σ-bonds

NASA Astrophysics Data System (ADS)

Kawai, Koji; Narushima, Takashi; Kaneko, Kotaro; Kawakami, Hayato; Matsumoto, Miyuki; Hyono, Atsushi; Nishihara, Hiroshi; Yonezawa, Tetsu

2012-12-01

The synthesis of 4-diazoniumcarboxylbenzene fluoroborate, a new water-soluble stabilizer for metal nanoparticles (NPs), is described. A stable dispersion of Ag NPs in water was successfully produced by a simultaneous aqueous reduction of this diazonium salt and silver nitrate by NaBH4. UV-vis spectra, TEM images, XRD patterns, and XPS spectra of the obtained Ag NPs revealed that they were stabilized by Ag-C σ-bonds. These NPs showed excellent antimicrobial properties against Staphylococcus aureus.

Alkali and alkaline earth metal salts of tetrazolone: structurally interesting and excellently thermostable.

PubMed

He, Piao; Wu, Le; Wu, Jin-Ting; Yin, Xin; Gozin, Michael; Zhang, Jian-Guo

2017-07-04

Tetrazolone (5-oxotetrazole) was synthesized by a moderate strategy through three steps (addition, cyclization and catalytic hydrogenation) avoiding the unstable intermediate diazonium, as reported during the previous preparation. Alkali and alkaline earth metal salts with lithium (1), sodium (2), potassium (3), rubidium (4) caesium (5), magnesium (6), calcium (7), strontium (8) and barium (9) were prepared and fully characterized using elemental analysis, IR and NMR spectroscopy, DSC and TG analysis. All metal salts were characterized via single-crystal X-ray diffraction. They crystallize in common space groups with high densities ranging from 1.479 (1) to 3.060 g cm -3 (5). Furthermore, the crystal structures of 7, 8 and 9 reveal interesting porous energetic coordination polymers with strong hydrogen bond interactions. All new salts have good thermal stabilities with decomposition temperature between 215.0 °C (4) and 328.2 °C (7), significantly higher than that of the reported nitrogen-rich salt neutral tetrazolone. The sensitivities towards impact and friction were tested using standard methods, and all the tetrazolone-based compounds investigated can be classified into insensitive. The flame test of these metal salts supports their potential use as perchlorate-free pyrotechnics or eco-friendly insensitive energetic materials.

A convenient catalyst for aqueous and protein Suzuki-Miyaura cross-coupling.

PubMed

Chalker, Justin M; Wood, Charlotte S C; Davis, Benjamin G

2009-11-18

A phosphine-free palladium catalyst for aqueous Suzuki-Miyaura cross-coupling is presented. The catalyst is active enough to mediate hindered, ortho-substituted biaryl couplings but mild enough for use on peptides and proteins. The Suzuki-Miyaura couplings on protein substrates are the first to proceed in useful conversions. Notably, hydrophobic aryl and vinyl groups can be transferred to the protein surface without the aid of organic solvent since the aryl- and vinylboronic acids used in the coupling are water-soluble as borate salts. The convenience and activity of this catalyst prompts use in both general synthesis and bioconjugation.

The Hydractinia echinata test-system. III: Structure-toxicity relationship study of some azo-, azo-anilide, and diazonium salt derivatives.

PubMed

Chicu, Sergiu Adrian; Munteanu, Melania; Cîtu, Ioana; Soica, Codruta; Dehelean, Cristina; Trandafirescu, Cristina; Funar-Timofei, Simona; Ionescu, Daniela; Simu, Georgeta Maria

2014-07-08

Structure-toxicity relationships for a series of 75 azo and azo-anilide dyes and five diazonium salts were developed using Hydractinia echinata (H. echinata) as model species. In addition, based on these relationships, predictions for 58 other azo-dyes were made. The experimental results showed that the measured effectiveness Mlog(1/MRC50) does not depend on the number of azo groups or the ones corresponding to metobolites, but it is influenced by the number of anilide groups, as well as by the substituents' positions within molecules. The conformational analysis pointed out the intramolecular hydrogen bonds, especially the simple tautomerization of quinoidic (STOH) or aminoidic (STNH2) type. The effectiveness is strongly influenced by the "push-pull" electronic effect, specific to two hydroxy or amino groups separated by an azo moiety (double alternate tautomery, (DAT), to the -COOH or -SO3H groups which are located in ortho or para position with respect to the azo group. The levels of the lipophylic/hydrophilic, electronic and steric equilibriums, pointed out by the Mlog(1/MRC50) values, enabled the calculation of their average values Clog(1/MRC50) ("Köln model"), characteristic to one derivative class (class isotoxicity). The azo group reduction and the hydrolysis of the amido/peptidic group are two concurrent enzymatic reactions, which occur with different reaction rates and mechanisms. The products of the partial biodegradation are aromatic amines. No additive or synergic effects are noticed among them.

Modification of Ti6Al4V surface by diazonium compounds.

PubMed

Sandomierski, Mariusz; Buchwald, Tomasz; Strzemiecka, Beata; Voelkel, Adam

2018-02-15

Ti6Al4V alloy is the most commonly used in orthopedic industry as an endoprosthesis. Ti6Al4V exhibits good mechanical properties, except the abrasion resistance. Surface modification of Ti6Al4V in order to obtain organic layer, and then the attachment of the polymer, can allow for overcoming this problem. The aim of the work was the modification of Ti6Al4V surface by diazonium compounds: salt or cation generated in situ and examine the influence of the reducing agent - ascorbic acid, and the temperature of reaction on modification process. Moreover, the simulated body fluid was used for the assessment of the organic layer stability on Ti6Al4V surface. The evaluation of the modification was carried out using the following methods: Raman microspectroscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy. Higher temperature of modification by 4-hydroxymethylbenzenediazonium cation, provides the largest amount of organic layer on the Ti6Al4V alloy. In the case of the Ti6Al4V modified by Variamine Blue B salt, the amount of organic layer is not dependent on the reaction condition. Moreover, the ascorbic acid and the presence of TiO 2 does not effect on the modification. The modified surface is completely coated with the organic layer which is stable in simulated body fluid. Copyright © 2017 Elsevier B.V. All rights reserved.

Facile synthesis of highly substituted 3-aminofurans from thiazolium salts, aldehydes, and dimethyl acetylenedicarboxylate.

PubMed

Ma, Cheng; Ding, Hanfeng; Wu, Guangming; Yang, Yewei

2005-10-28

[reaction: see text] A facile preparation of 3-aminofuran derivatives via multicomponent reactions of thiazole carbenes, aldehydes, and dimethyl acetylenedicarboxylate (DMAD) is reported. In this process, the thiazole carbenes, generated in situ from thiazolium salts, reacted with aldehydes and DMAD at -78 to 0 degree C in CH(2)Cl(2) to afford the substituted furans in moderate to good yields. Eight substituted thiazolium salts were employed as carbene precursors in the reaction. Besides aryl aldehydes, alpha,beta-unsaturated aldehydes, aliphatic aldehydes, and arenedial were also investigated and found to be applicable to this reaction.

Unlocking the energy capabilities of micron-sized LiFePO4.

PubMed

Guo, Limin; Zhang, Yelong; Wang, Jiawei; Ma, Lipo; Ma, Shunchao; Zhang, Yantao; Wang, Erkang; Bi, Yujing; Wang, Deyu; McKee, William C; Xu, Ye; Chen, Jitao; Zhang, Qinghua; Nan, Cewen; Gu, Lin; Bruce, Peter G; Peng, Zhangquan

2015-08-03

Utilization of LiFePO4 as a cathode material for Li-ion batteries often requires size nanonization coupled with calcination-based carbon coating to improve its electrochemical performance, which, however, is usually at the expense of tap density and may be environmentally problematic. Here we report the utilization of micron-sized LiFePO4, which has a higher tap density than its nano-sized siblings, by forming a conducting polymer coating on its surface with a greener diazonium chemistry. Specifically, micron-sized LiFePO4 particles have been uniformly coated with a thin polyphenylene film via the spontaneous reaction between LiFePO4 and an aromatic diazonium salt of benzenediazonium tetrafluoroborate. The coated micron-sized LiFePO4, compared with its pristine counterpart, has shown improved electrical conductivity, high rate capability and excellent cyclability when used as a 'carbon additive free' cathode material for rechargeable Li-ion batteries. The bonding mechanism of polyphenylene to LiFePO4/FePO4 has been understood with density functional theory calculations.

Unlocking the energy capabilities of micron-sized LiFePO4

PubMed Central

Guo, Limin; Zhang, Yelong; Wang, Jiawei; Ma, Lipo; Ma, Shunchao; Zhang, Yantao; Wang, Erkang; Bi, Yujing; Wang, Deyu; McKee, William C.; Xu, Ye; Chen, Jitao; Zhang, Qinghua; Nan, Cewen; Gu, Lin; Bruce, Peter G.; Peng, Zhangquan

2015-01-01

Utilization of LiFePO4 as a cathode material for Li-ion batteries often requires size nanonization coupled with calcination-based carbon coating to improve its electrochemical performance, which, however, is usually at the expense of tap density and may be environmentally problematic. Here we report the utilization of micron-sized LiFePO4, which has a higher tap density than its nano-sized siblings, by forming a conducting polymer coating on its surface with a greener diazonium chemistry. Specifically, micron-sized LiFePO4 particles have been uniformly coated with a thin polyphenylene film via the spontaneous reaction between LiFePO4 and an aromatic diazonium salt of benzenediazonium tetrafluoroborate. The coated micron-sized LiFePO4, compared with its pristine counterpart, has shown improved electrical conductivity, high rate capability and excellent cyclability when used as a ‘carbon additive free' cathode material for rechargeable Li-ion batteries. The bonding mechanism of polyphenylene to LiFePO4/FePO4 has been understood with density functional theory calculations. PMID:26235395

Unlocking the energy capabilities of micron-sized LiFePO4

NASA Astrophysics Data System (ADS)

Guo, Limin; Zhang, Yelong; Wang, Jiawei; Ma, Lipo; Ma, Shunchao; Zhang, Yantao; Wang, Erkang; Bi, Yujing; Wang, Deyu; McKee, William C.; Xu, Ye; Chen, Jitao; Zhang, Qinghua; Nan, Cewen; Gu, Lin; Bruce, Peter G.; Peng, Zhangquan

2015-08-01

Utilization of LiFePO4 as a cathode material for Li-ion batteries often requires size nanonization coupled with calcination-based carbon coating to improve its electrochemical performance, which, however, is usually at the expense of tap density and may be environmentally problematic. Here we report the utilization of micron-sized LiFePO4, which has a higher tap density than its nano-sized siblings, by forming a conducting polymer coating on its surface with a greener diazonium chemistry. Specifically, micron-sized LiFePO4 particles have been uniformly coated with a thin polyphenylene film via the spontaneous reaction between LiFePO4 and an aromatic diazonium salt of benzenediazonium tetrafluoroborate. The coated micron-sized LiFePO4, compared with its pristine counterpart, has shown improved electrical conductivity, high rate capability and excellent cyclability when used as a `carbon additive free' cathode material for rechargeable Li-ion batteries. The bonding mechanism of polyphenylene to LiFePO4/FePO4 has been understood with density functional theory calculations.

Bifluoride-catalysed sulfur(VI) fluoride exchange reaction for the synthesis of polysulfates and polysulfonates

NASA Astrophysics Data System (ADS)

Gao, Bing; Zhang, Linda; Zheng, Qinheng; Zhou, Feng; Klivansky, Liana M.; Lu, Jianmei; Liu, Yi; Dong, Jiajia; Wu, Peng; Sharpless, K. Barry

2017-11-01

Polysulfates and polysulfonates possess exceptional mechanical properties making them potentially valuable engineering polymers. However, they have been little explored due to a lack of reliable synthetic access. Here we report bifluoride salts (Q+[FHF]-, where Q+ represents a wide range of cations) as powerful catalysts for the sulfur(VI) fluoride exchange (SuFEx) reaction between aryl silyl ethers and aryl fluorosulfates (or alkyl sulfonyl fluorides). The bifluoride salts are significantly more active in catalysing the SuFEx reaction compared to organosuperbases, therefore enabling much lower catalyst-loading (down to 0.05 mol%). Using this chemistry, we are able to prepare polysulfates and polysulfonates with high molecular weight, narrow polydispersity and excellent functional group tolerance. The process is practical with regard to the reduced cost of catalyst, polymer purification and by-product recycling. We have also observed that the process is not sensitive to scale-up, which is essential for its future translation from laboratory research to industrial applications.

Selective Cleavage of the Aryl Ether Bonds in Lignin for Depolymerization by Acidic Lithium Bromide Molten Salt Hydrate under Mild Conditions.

PubMed

Yang, Xiaohui; Li, Ning; Lin, Xuliang; Pan, Xuejun; Zhou, Yonghong

2016-11-09

The present study demonstrates that the concentrated lithium bromide (LiBr) solution with acid as catalyst was able to selectively cleave the β-O-4 aryl ether bond and lead to lignin depolymerization under mild conditions (e.g., in 60% LiBr with 0.3 M HCl at 110 °C for 2 h). Four industrial lignins from different pulping and biorefining processes, including softwood kraft lignin (SKL), hardwood kraft lignin (HKL), softwood ethanol organosolv lignin (EOL), and acid corncob lignin (ACL), were treated in the LiBr solution. The molecular weight, functional group, and interunit linkages of the lignins were characterized using GPC, FTIR, and NMR. The results indicated that the β-O-4 aryl ether bonds of the lignins were selectively cleaved, and both LiBr and HCl played crucial roles in catalyzing the cleavage of the ether bonds.

Copper(II)-Catalyzed Conversion of Aryl/Heteroaryl Boronic Acids, Boronates, and Trifluoroborates into the Corresponding Azides: Substrate Scope and Limitations.

PubMed

Grimes, Kimberly D; Gupte, Amol; Aldrich, Courtney C

2010-05-01

We report the copper(II)-catalyzed conversion of organoboron compounds into the corresponding azide derivatives. A systematic series of phenylboronic acid derivatives is evaluated to examine the importance of steric and electronic effects of the substituents on reaction yield as well as functional group compatibility. Heterocyclic substrates are also shown to participate in this mild reaction while compounds incorporating B-C(sp(3)) bonds are unreactive under the reaction conditions. The copper(II)-catalyzed boronic acid-azide coupling reaction is further extended to both boronate esters and potassium organotrifluoroborate salts. The method described herein complements existing procedures for the preparation of aryl azides from the respective amino, triazene, and halide derivatives and we expect that it will greatly facilitate copper- and ruthenium-catalyzed azide-alkyne cycloaddition reactions for the preparation of diversely functionalized 1-aryl- or 1-heteroaryl-1,2,3-triazoles derivatives.

Behavior of a chemically doped graphene junction

NASA Astrophysics Data System (ADS)

Farmer, Damon B.; Lin, Yu-Ming; Afzali-Ardakani, Ali; Avouris, Phaedon

2009-05-01

Polyethylene imine and diazonium salts are used as complementary molecular dopants to engineer a doping profile in a graphene transistor. Electronic transport in this device reveals the presence of two distinct resistance maxima, alluding to neutrality point separation and subsequent formation of a spatially abrupt junction. Carrier mobility in this device is not significantly affected by molecular doping or junction formation, and carrier transmission is found to scale inversely with the effective channel length of the device. Chemical dilutions are used to modify the dopant concentration and, in effect, alter the properties of the junction.

Boron-based dual imaging probes, compositions and methods for rapid aqueous F-18 labeling, and imaging methods using same

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Zibo; Gabbai, Francois P.; Conti, Peter S.

A composition useful as a PET and/or fluorescence imaging probe a compound a compound of Formula I, including salts, hydrates and solvates thereof: ##STR00001## wherein R.sub.1-R.sub.7 may be independently selected from hydrogen, halogen, hydroxy, alkoxy, nitro, substituted and unsubstituted amino, cycloalkyl, carboxy, carboxylic acids and esters thereof, cyano, haloalkyl, aryl, X is selected from the group consisting of C and N; and A is selected of hydrogen, halogen, hydroxy, alkoxy, nitro, substituted and unsubstituted amino, alkyl, cycloalkyl, carboxy, carboxylic acids and esters thereof, cyano, haloalkyl, aryl, including phenyl and aminophenyl, and heteroaryl.

Direct arylation/alkylation/magnesiation of benzyl alcohols in the presence of Grignard reagents via Ni-, Fe-, or Co-catalyzed sp3 C-O bond activation.

PubMed

Yu, Da-Gang; Wang, Xin; Zhu, Ru-Yi; Luo, Shuang; Zhang, Xiao-Bo; Wang, Bi-Qin; Wang, Lei; Shi, Zhang-Jie

2012-09-12

Direct application of benzyl alcohols (or their magnesium salts) as electrophiles in various reactions with Grignard reagents has been developed via transition metal-catalyzed sp(3) C-O bond activation. Ni complex was found to be an efficient catalyst for the first direct cross coupling of benzyl alcohols with aryl/alkyl Grignard reagents, while Fe, Co, or Ni catalysts could promote the unprecedented conversion of benzyl alcohols to benzyl Grignard reagents in the presence of (n)hexylMgCl. These methods offer straightforward pathways to transform benzyl alcohols into a variety of functionalities.

Chemistry of carbon nanomaterials: Uses of lithium nanotube salts in organic syntheses and functionalization of graphite

NASA Astrophysics Data System (ADS)

Chattopadhyay, Jayanta

The effective utilization of carbon nanomaterials, such as single-walled carbon nanotubes (SWNTs) and graphite, has been hindered due to difficulties (poor solubility, poly-dispersity) in processing. Therefore, a high degree of sidewall functionalization, either covalent or non-covalent, is often required to overcome these difficulties as the functionalized nanomaterials exhibit better solubility (either in organic solvents or in water), dispersity, manipulation, and processibility. This thesis presents a series of convenient and efficient organic synthetic routes to functionalize carbon nanomaterials. Carbon nanotube salts, prepared by treating SWNTs with lithium in liquid ammonia, react readily with aryl halides to yield aryl-functionalized SWNTs. These arylated SWNTs are soluble in methanol and water upon treatment with oleum. Similarly, SWNTs can be covalently functionalized by different heteroatoms (nitrogen, oxygen, and sulfur). Using the reductive alkylation approach, a synthetic scheme is designed to prepare long chain carboxylic acid functionalized SWNTs [SWNTs-(RCOOH)] that can react with (1) amine-terminated polyethylene glycol (PEG) chains to yield water-soluble biocompatible PEGylated SWNTs that are likely to be useful in a variety of biomedical applications; (2) polyethyleneimine (PEI) to prepare a SWNTs-PEI based adsorbent material that shows a four-fold improvement in the adsorption capacity of carbon dioxide over commonly used materials, making it useful for regenerable carbon dioxide removal in spaceflight; (3) chemically modified SWNTs-(RCOOH) to permit covalent bonding to the nylon matrix, thus allowing the formation of nylon 6,10 and nylon 6,10/SWNTs-(RCOOH) nanocomposites. Furthermore, we find that the lithium salts of carbon nanotubes serve as a source of electrons to induce polymerization of simple alkenes and alkynes onto the surface of carbon nanotubes. In the presence of sulfide/disulfide bonds, SWNT salts can initiate the single electron transfer (SET) mechanism to functionalize carbon nanotubes with different alkyl/aryl groups. Using the reductive alkylation approach, we can also functionalize graphites by alkyl/carboxylic acid groups, making graphite soluble in organic solvents and water. Tailoring of graphite layers is also accomplished by using different metals in liquid ammonia. Finally, SWNT-epoxides/graphite epoxides are synthesized using m-CPBA. Quantification of the epoxide substituents on the nanotube/graphite surface is evaluated through the catalytic de-epoxidation reaction using MeReO 3/PPh3 as heterogeneous catalyst. In summary, the proposed covalent functionalization methods yield derivatized nanomaterials that can provide a solid platform for a number of exciting applications, ranging from material science to biomedical devices. Furthermore, the results presented in this thesis provide insight into the molecular chemistry at nano-resolution.

Iodine(III) Reagents in Radical Chemistry

PubMed Central

2017-01-01

Conspectus The chemistry of hypervalent iodine(III) compounds has gained great interest over the past 30 years. Hypervalent iodine(III) compounds show valuable ionic reactivity due to their high electrophilicity but also express radical reactivity as single electron oxidants for carbon and heteroatom radical generation. Looking at ionic chemistry, these iodine(III) reagents can act as electrophiles to efficiently construct C–CF3, X–CF3 (X = heteroatom), C–Rf (Rf = perfluoroalkyl), X–Rf, C–N3, C–CN, S–CN, and C–X bonds. In some cases, a Lewis or a Bronsted acid is necessary to increase their electrophilicity. In these transformations, the iodine(III) compounds react as formal “CF3+”, “Rf+”, “N3+”, “Ar+”, “CN+”, and “X+” equivalents. On the other hand, one electron reduction of the I(III) reagents opens the door to the radical world, which is the topic of this Account that focuses on radical reactivity of hypervalent iodine(III) compounds such as the Togni reagent, Zhdankin reagent, diaryliodonium salts, aryliodonium ylides, aryl(cyano)iodonium triflates, and aryl(perfluoroalkyl)iodonium triflates. Radical generation starting with I(III) reagents can also occur via thermal or light mediated homolysis of the weak hypervalent bond in such reagents. This reactivity can be used for alkane C–H functionalization. We will address important pioneering work in the area but will mainly focus on studies that have been conducted by our group over the last 5 years. We entered the field by investigating transition metal free single electron reduction of Togni type reagents using the readily available sodium 2,2,6,6-tetramethylpiperidine-1-oxyl salt (TEMPONa) as an organic one electron reductant for clean generation of the trifluoromethyl radical and perfluoroalkyl radicals. That valuable approach was later successfully also applied to the generation of azidyl and aryl radicals starting with the corresponding benziodoxole (Zhdankin reagent) and iodonium salts. In the presence of alkenes as radical acceptors, vicinal trifluoromethyl-, azido-, and arylaminoxylation products result via a sequence comprising radical addition to the alkene and subsequent TEMPO trapping. Electron-rich arenes also react with I(III) reagents via single electron transfer (SET) to give arene radical cations, which can then engage in arylation reactions. We also recognized that the isonitrile functionality in aryl isonitriles is a highly efficient perfluoroalkyl radical acceptor, and reaction of Rf-benziodoxoles (Togni type reagents) in the presence of a radical initiator provides various perfluoroalkylated N-heterocycles (indoles, phenanthridines, quinolines, etc.). We further found that aryliodonium ylides, previously used as carbene precursors in metal-mediated cyclopropanation reactions, react via SET reduction with TEMPONa to the corresponding aryl radicals. As a drawback of all these transformations, we realized that only one ligand of the iodine(III) reagent gets transferred to the substrate. To further increase atom-economy of such conversions, we identified cyano or perfluoroalkyl iodonium triflate salts as valuable reagents for stereoselective vicinal alkyne difunctionalization, where two ligands from the I(III) reagent are sequentially transferred to an alkyne acceptor. Finally, we will discuss alkynyl-benziodoxoles as radical acceptors for alkynylation reactions. Similar reactivity was found for the Zhdankin reagent that has been successfully applied to azidation of C-radicals, and also cyanation is possible with a cyano I(III) reagent. To summarize, this Account focuses on the design, development, mechanistic understanding, and synthetic application of hypervalent iodine(III) reagents in radical chemistry. PMID:28636313

Electrografting of conductive oligomers and polymers using diazonium electroreduction

NASA Astrophysics Data System (ADS)

Lacroix, Jean Christophe; Trippe-Allard, Gaelle; Ghilane, Jalal; Martin, Pascal

2014-03-01

This paper describes the attachment of conjugated oligomers onto electrode surface through the reduction of diazonium compounds. In this connection some properties of conjugated oligomers and of layers grafted through diazonium electroreduction will first be briefly presented. The electrochemical behavior of conjugated oligomers grafted on a surface using diazonium electroreduction will then be discussed.

Synthesis and characterization of Cu(II), Co(II) and Ni(II) complexes of a number of sulfadrug azodyes and their application for wastewater treatment

NASA Astrophysics Data System (ADS)

El-Baradie, K.; El-Sharkawy, R.; El-Ghamry, H.; Sakai, K.

2014-03-01

The azodye ligand (HL1) was synthesized from the coupling of sulfaguanidine diazonium salt with 2,4-dihydroxy-benzaldehyde while the two ligands, HL2 and HL3, were prepared by the coupling of sulfadiazine diazonium salt with salicylaldehyde (HL2) and 2,4-dihydroxy-benzaldehyde (HL3). The prepared ligands were characterized by elemental analysis, IR, 1H NMR and mass spectra. Cu(II), Co(II) and Ni(II) complexes of the prepared ligands have been synthesized and characterized by various spectroscopic techniques like IR, UV-Visible as well as magnetic and thermal (TG and DTA) measurements. It was found that all the ligands behave as a monobasic bidentate which coordinated to the metal center through the azo nitrogen and α-hydroxy oxygen atoms in the case of HL1 and HL3. HL2 coordinated to the metal center through sulfonamide oxygen and pyrimidine nitrogen. The applications of the prepared complexes in the oxidative degradation of indigo carmine dye exhibited good catalytic activity in the presence of H2O2 as an oxidant. The reactions followed first-order kinetics and the rate constants were determined. The degradation reaction involved the catalytic action of the azo-dye complexes toward H2O2 decomposition, which can lead to the generation of HOrad radicals as a highly efficient oxidant attacking the target dye. The detailed kinetic studies and the mechanism of these catalytic reactions are under consideration in our group.

Synthesis of the diazonium (perfluoroalkyl) benzenesulfonimide monomer from Nafion monomer for proton exchange membrane fuel cells

NASA Astrophysics Data System (ADS)

Mei, Hua; D'Andrea, Dan; Nguyen, Tuyet-Trinh; Nworie, Chima

2014-02-01

One diazonium (perfluoroalkyl) benzenesulfonimide monomer, perfluoro-3, 6-dioxa-4-methyl-7-octene benzenesulfonyl imide, has been synthesized from Nafion monomer for the first time. With trifluorovinyl ether and diazonium precursors, the partially-fluorinated diazonium PFSI monomer can be polymerized and will provide chemically bonding with carbon electrode in proton exchange membrane fuel cells. A systematic study of the synthesis and characterization of this diazonium PFSI monomer has been conducted by varying reaction conditions. The optimized synthesis method has been established in the lab.

Synthesis of structurally diverse benzosuberene analogues and their biological evaluation as anti-cancer agents

PubMed Central

Tanpure, Rajendra P.; George, Clinton S.; Strecker, Tracy E.; Devkota, Laxman; Tidmore, Justin K.; Lin, Chen-Ming; Herdman, Christine A.; MacDonough, Matthew T.; Sriram, Madhavi; Chaplin, David J.; Trawick, Mary Lynn; Pinney, Kevin G.

2014-01-01

Diversely functionalized, fused aryl-alkyl ring systems hold a prominent position as well-established molecular frameworks for a variety of anti-cancer agents. The benzosuberene (6,7 fused, also referred to as dihydro-5H-benzo[7]annulene and benzocycloheptene) ring system has emerged as a valuable molecular core component for the development of inhibitors of tubulin assembly, which function as antiproliferative anti-cancer agents and, in certain cases, as vascular disrupting agents (VDAs). Both a phenolic-based analogue (known as KGP18, compound 39) and its corresponding amine-based congener (referred to as KGP156, compound 45), which demonstrate strong inhibition of tubulin assembly (low micromolar range) and potent cytotoxicity (picomolar range for KGP18 and nanomolar range for KGP156) are noteworthy examples of such benzosuberene-based compounds. In order to extend the structure-activity relationship (SAR) knowledge base related to benzosuberene anti-cancer agents, a series of eleven analogues (including KGP18) were prepared in which the methoxylation pattern on the pendant aryl ring as well as functional group incorporation on the fused aryl ring were varied. The synthetic approach to these compounds featured a sequential Wittig olefination, reduction, Eaton's reagent-mediated cyclization strategy to achieve the core benzosuberone intermediate, and represented a higher-yielding synthesis of KGP18 (which we prepared previously through a ring-expansion strategy). Incorporation of a fluorine or chlorine atom at the 1-position of the fused aryl ring or replacement of one of the methoxy groups with hydrogen (on the pendant aryl ring of KGP18) led to benzosuberene analogues that were both strongly inhibitory against tubulin assembly (IC50 approximately 1.0 M) and strongly cytotoxic against selected human cancer cell lines (for example, GI50 = 5.47 nM against NCI-H460 cells with fluorobenzosuberene analogue 37). A water-soluble phosphate prodrug salt of KGP18 (referred to as KGP265, compound 44) and a water-soluble serinamide salt (compound 48) of KGP156 were also synthesized and evaluated in this study. PMID:24183586

Design, Synthesis, and Structure--Activity Relationship of New 2-Aryl-3,4-dihydro-β-carbolin-2-ium Salts as Antifungal Agents.

PubMed

Hou, Zhe; Zhu, Li-Fei; Yu, Xin-chi; Sun, Ma-Qiang; Miao, Fang; Zhou, Le

2016-04-13

Twenty-two 2-aryl-9-methyl-3,4-dihydro-β-carbolin-2-ium bromides along with four 9-demethylated derivatives were synthesized and characterized by spectroscopic analysis. By using the mycelium growth rate method, the compounds were evaluated for antifungal activities in vitro against six plant pathogenic fungi, and structure-activity relationships (SAR) were derived. Almost all of the compounds showed obvious inhibition activity on each of the fungi at 150 μM. For all of the fungi, 10 of the compounds showed average inhibition rates of >80% at 150 μM, and most of their EC50 values were in the range of 2.0-30.0 μM. SAR analysis showed that the substitution pattern of the N-aryl ring significantly influences the activity; N9-alkylation improves the activity, whereas aromatization of ring-C reduces the activity. It was concluded that the present research provided a series of new 2-aryl-9-alkyl-3,4-dihydro-β-carbolin-2-iums with excellent antifungal potency and structure optimization design for the development of new carboline antifungal agents.

Iron-Catalyzed Enantioselective Cross-Coupling Reactions of α-Chloroesters with Aryl Grignard Reagents.

PubMed

Jin, Masayoshi; Adak, Laksmikanta; Nakamura, Masaharu

2015-06-10

The first iron-catalyzed enantioselective cross-coupling reaction between an organometallic compound and an organic electrophile is reported. Synthetically versatile racemic α-chloro- and α-bromoalkanoates were coupled with aryl Grignard reagents in the presence of catalytic amounts of an iron salt and a chiral bisphosphine ligand, giving the products in high yields with acceptable and synthetically useful enantioselectivities (er up to 91:9). The produced α-arylalkanoates were readily converted to the corresponding α-arylalkanoic acids with high optical enrichment (er up to >99:1) via simple deprotections/recrystallizations. The results of radical probe experiments are consistent with a mechanism that involves the formation of an alkyl radical intermediate, which undergoes subsequent enantioconvergent arylation in an intermolecular manner. The developed asymmetric coupling offers not only facile and practical access to various chiral α-arylalkanoic acid derivatives, which are of significant pharmaceutical importance, but also a basis of controlling enantioselectivity in an iron-catalyzed organometallic transformation.

Non-aqueous electrolyte for lithium-ion battery

DOEpatents

Amine, Khalil; Zhang, Lu; Zhang, Zhengcheng

2016-01-26

A substantially non-aqueous electrolyte solution includes an alkali metal salt, a polar aprotic solvent, and an organophosphorus compound of Formula IA, IB, or IC: ##STR00001## where R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are each independently hydrogen, halogen, alkyl, alkenyl, alkynyl, cycloalkyl, aryl, heterocyclyl, heteroaryl, alkoxy, alkenoxy, alkynoxy, cycloalkoxy, aryloxy, heterocyclyloxy, heteroaryloxy, siloxyl, silyl, or organophosphatyl; R.sup.5 and R.sup.6 are each independently alkyl, alkenyl, alkynyl, cycloalkyl, aryl, heterocyclyl, or heteroaryl; R.sup.7 is ##STR00002## and R.sup.8, R.sup.9 and R.sup.10 are each independently alkyl, cycloalkyl, aryl, heterocyclyl, or heteroaryl; provided that if the organophosphorus compound is of Formula IB, then at least one of R.sup.5, and R.sup.6 are other than hydrogen, alkyl, or alkenyl; and if the organophosphorus compound is of Formula IC, then the electrolyte solution does not include 4-methylene-1,3-dioxolan-2-one or 4,5-dimethylene-1,3-dioxolan-2-one.

Covalent functionalization of reduced graphene oxide with porphyrin by means of diazonium chemistry for nonlinear optical performance

NASA Astrophysics Data System (ADS)

Wang, Aijian; Yu, Wang; Huang, Zhipeng; Zhou, Feng; Song, Jingbao; Song, Yinglin; Long, Lingliang; Cifuentes, Marie P.; Humphrey, Mark G.; Zhang, Long; Shao, Jianda; Zhang, Chi

2016-03-01

Reduced graphene oxide (RGO)-porphyrin (TPP) nanohybrids (RGO-TPP 1 and RGO-TPP 2) were prepared by two synthetic routes that involve functionalization of the RGO using diazonium salts. The microscopic structures, morphology, photophysical properties and nonlinear optical performance of the resultant RGO-TPP nanohybrids were investigated. The covalent bonding of the porphyrin-functionalized-RGO nanohybrid materials was confirmed by Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, and thermogravimetric analysis. Attachment of the porphyrin units to the surface of the RGO by diazotization significantly improves the solubility and ease of processing of these RGO-based nanohybrid materials. Ultraviolet/visible absorption and steady-state fluorescence studies indicate considerable π-π interactions and effective photo-induced electron and/or energy transfer between the porphyrin moieties and the extended π-system of RGO. The nonlinear optical properties of RGO-TPP 1 and RGO-TPP 2 were investigated by open-aperture Z-scan measurements at 532 nm with both 4 ns and 21 ps laser pulses, the results showing that the chemical nanohybrids exhibit improved nonlinear optical properties compared to those of the benchmark material C60, and the constituent RGO or porphyrins.

Carboxylate modified porous graphitic carbon: a new class of hydrophilic interaction liquid chromatography phases.

PubMed

Wahab, M Farooq; Ibrahim, Mohammed E A; Lucy, Charles A

2013-06-18

Stationary phases for hydrophilic interaction liquid chromatography (HILIC) are predominantly based on silica and polymer supports. We present porous graphitic carbon particles with covalently attached carboxylic acid groups (carboxylate-PGC) as a new HILIC stationary phase. PGC particles were modified by adsorbing the diazonium salt of 4-aminobenzoic acid onto the PGC, followed by reduction of the adsorbed salt with sodium borohydride. The newly developed carboxylate-PGC phase exhibits different selectivity than that of 35 HPLC columns, including bare silica, zwitterionic, amine, reversed, and unmodified PGC phases. Carboxylate-PGC is stable from pH 2.0 to 12.6, yielding reproducible retention even at pH 12.6. Characterization of the new phase is presented by X-ray photoelectron spectroscopy, thermogravimetry, zeta potentials, and elemental analysis. The chromatographic performance of carboxylate-PGC as a HILIC phase is illustrated by separations of carboxylic acids, nucleotides, phenols, and amino acids.

Electrochemical behavior of platinum nanoparticles on a carbon xerogel support modified with a [(trifluoromethyl)-benzenesulfonyl]imide electrolyte.

PubMed

Liu, Bing; Mei, Hua; DesMarteau, Darryl; Creager, Stephen E

2014-12-11

A monoprotic [(trifluoromethyl)benzenesulfonyl]imide (SI) superacid electrolyte was used to covalently modify a mesoporous carbon xerogel (CX) support via reaction of the corresponding trifluoromethyl aryl sulfonimide diazonium zwitterion with the carbon surface. Electrolyte attachment was demonstrated by elemental analysis, acid-base titration, and thermogravimetric analysis. The ion-exchange capacity of the fluoroalkyl-aryl-sulfonimide-grafted carbon xerogel (SI-CX) was ∼0.18 mequiv g(-1), as indicated by acid-base titration. Platinum nanoparticles were deposited onto the SI-grafted carbon xerogel samples by the impregnation and reduction method, and these materials were employed to fabricate polyelectrolyte membrane fuel-cell (PEMFC) electrodes by the decal transfer method. The SI-grafted carbon-xerogel-supported platinum (Pt/SI-CX) was characterized by X-ray diffraction and transmission electron microscopy to determine platinum nanoparticle size and distribution, and the findings are compared with CX-supported platinum catalyst without the grafted SI electrolyte (Pt/CX). Platinum nanoparticle sizes are consistently larger on Pt/SI-CX than on Pt/CX. The electrochemically active surface area (ESA) of platinum catalyst on the Pt/SI-CX and Pt/CX samples was measured with ex situ cyclic voltammetry (CV) using both hydrogen adsorption/desorption and carbon monoxide stripping methods and by in situ CV within membrane electrode assemblies (MEAs). The ESA values for Pt/SI-CX are consistently lower than those for Pt/CX. Some possible reasons for the behavior of samples with and without grafted SI layers and implications for the possible use of SI-grafted carbon layers in PEMFC devices are discussed.

The Behavior of the Ru-bda Water Oxidation Catalysts at Low Oxidation States.

PubMed

Matheu, Roc; Ghaderian, Abolfazl; Francas, Laia; Chernev, Petko; Ertem, Mehmed; Benet-Buchholz, Jordi; Batista, Victor; Haumann, Michael; Gimbert-Suriñach, Carolina; Sala, Xavier; Llobet, Antoni

2018-06-13

The Ru complex [RuII(bda-κ-N2O2)(N-NH2)2], 1, (bda2- = (2,2'-bipyridine)-6,6'-dicarboxylate; N-NH2 = 4-(pyridin-4-yl)aniline) is used as a synthetic intermediate to prepare Ru-bda complexes that contain the NO+, acetonitrile (MeCN) or H2O ligands at oxidation states II and III. Complex 1 reacts with excess NO+ to form a Ru complex where the aryl amine ligands N-NH2 in 1 are transformed into diazonium salts (N-N2+ = 4-(pyridin-4-yl)benzenediazonium)) together with the formation of a new Ru-NO group at the equatorial zone, to generate [RuII(bda-κ-N2O)(NO)(N-N2)2]3+, 23+. Similarly, complex 1 can also react with a coordinating solvent, such as MeCN, at room temperature leading to complex [RuII(bda-κ-N2O)(MeCN)(N-NH2)2], 3. Finally in acidic aqueous solutions solvent water coordinates the Ru center forming {[RuII(bda-κ-(NO)3)(H2O)(N-NH3)2](H2O)n}2+, 42+, that is strongly hydrogen bonded with additional water molecules at the second coordination sphere. We have additionally characterized the one electron oxidized complex {[RuIII(bda-κ-(NO)3.5)(H2O)(N-NH3)2](H2O)n}3+, 53+. The coordination mode of the complexes has been studied both in the solid state and in solution through single-crystal XRD, X-ray absorption spectroscopy, variable-temperature NMR and DFT calculations. While the κ-N2O is the main coordination mode for 23+ and 3, an equilibrium that involves isomers with κ-N2O and κ-NO2 coordination modes and neighboring hydrogen bonded water molecules is observed for 42+ and 53+. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Immobilised histidine tagged β2-adrenoceptor oriented by a diazonium salt reaction and its application in exploring drug-protein interaction using ephedrine and pseudoephedrine as probes.

PubMed

Li, Qian; Bian, Liujiao; Zhao, Xinfeng; Gao, Xiaokang; Zheng, Jianbin; Li, Zijian; Zhang, Youyi; Jiang, Ru; Zheng, Xiaohui

2014-01-01

A new oriented method using a diazonium salt reaction was developed for linking β2-adrenoceptor (β2-AR) on the surface of macroporous silica gel. Stationary phase containing the immobilised receptor was used to investigate the interaction between β2-AR and ephedrine plus pseudoephedrine by zonal elution. The isotherms of the two drugs best fit the Langmuir model. Only one type of binding site was found for ephedrine and pseudoephedrine targeting β2-AR. At 37 °C, the association constants during the binding were (5.94±0.05)×103/M for ephedrine and (3.80±0.02) ×103/M for pseudoephedrine, with the binding sites of (8.92±0.06) ×10-4 M. Thermodynamic studies showed that the binding of the two compounds to β2-AR was a spontaneous reaction with exothermal processes. The ΔGθ, ΔHθ and ΔSθ for the interaction between ephedrine and β2-AR were -(22.33±0.04) kJ/mol, -(6.51±0.69) kJ/mol and 50.94±0.31 J/mol·K, respectively. For the binding of pseudoephedrine to the receptor, these values were -(21.17±0.02) kJ/mol, -(7.48±0.56) kJ/mol and 44.13±0.01 J/mol·K. Electrostatic interaction proved to be the driving force during the binding of the two drugs to β2-AR. The proposed immobilised method will have great potential for attaching protein to solid substrates and realizing the interactions between proteins and drugs.

Immobilised Histidine Tagged β 2-Adrenoceptor Oriented by a Diazonium Salt Reaction and Its Application in Exploring Drug-Protein Interaction Using Ephedrine and Pseudoephedrine as Probes

PubMed Central

Li, Qian; Bian, Liujiao; Zhao, Xinfeng; Gao, Xiaokang; Zheng, Jianbin; Li, Zijian; Zhang, Youyi; Jiang, Ru; Zheng, Xiaohui

2014-01-01

A new oriented method using a diazonium salt reaction was developed for linking β 2-adrenoceptor (β 2-AR) on the surface of macroporous silica gel. Stationary phase containing the immobilised receptor was used to investigate the interaction between β 2-AR and ephedrine plus pseudoephedrine by zonal elution. The isotherms of the two drugs best fit the Langmuir model. Only one type of binding site was found for ephedrine and pseudoephedrine targeting β 2-AR. At 37 °C, the association constants during the binding were (5.94±0.05)×103/M for ephedrine and (3.80±0.02) ×103/M for pseudoephedrine, with the binding sites of (8.92±0.06) ×10−4 M. Thermodynamic studies showed that the binding of the two compounds to β 2-AR was a spontaneous reaction with exothermal processes. The ΔGθ, ΔHθ and ΔSθ for the interaction between ephedrine and β 2-AR were −(22.33±0.04) kJ/mol, −(6.51±0.69) kJ/mol and 50.94±0.31 J/mol·K, respectively. For the binding of pseudoephedrine to the receptor, these values were −(21.17±0.02) kJ/mol, −(7.48±0.56) kJ/mol and 44.13±0.01 J/mol·K. Electrostatic interaction proved to be the driving force during the binding of the two drugs to β 2-AR. The proposed immobilised method will have great potential for attaching protein to solid substrates and realizing the interactions between proteins and drugs. PMID:24747442

Spatial and temporal control of the diazonium modification of sp2 carbon surfaces.

PubMed

Kirkman, Paul M; Güell, Aleix G; Cuharuc, Anatolii S; Unwin, Patrick R

2014-01-08

Interest in the controlled chemical functionalization of sp(2) carbon materials using diazonium compounds has been recently reignited, particularly as a means to generate a band gap in graphene. We demonstrate local diazonium modification of pristine sp(2) carbon surfaces, with high control, at the micrometer scale through the use of scanning electrochemical cell microscopy (SECCM). Electrochemically driven diazonium patterning is investigated at a range of driving forces, coupled with surface analysis using atomic force microscopy (AFM) and Raman spectroscopy. We highlight how the film density, level of sp(2)/sp(3) rehybridization and the extent of multilayer formation can be controlled, paving the way for the use of localized electrochemistry as a route to controlled diazonium modification.

Cascade multicomponent synthesis of indoles, pyrazoles, and pyridazinones by functionalization of alkenes.

PubMed

Matcha, Kiran; Antonchick, Andrey P

2014-10-27

The development of multicomponent reactions for indole synthesis is demanding and has hardly been explored. The present study describes the development of a novel multicomponent, cascade approach for indole synthesis. Various substituted indole derivatives were obtained from simple reagents, such as unfunctionalized alkenes, diazonium salts, and sodium triflinate, by using an established straightforward and regioselective method. The method is based on the radical trifluoromethylation of alkenes as an entry into Fischer indole synthesis. Besides indole synthesis, the application of the multicomponent cascade reaction to the synthesis of pyrazoles and pyridazinones is described. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Second harmonic generation by all-optical poling and its relaxation in the polymer films containing azo sulfonamide chromophores

NASA Astrophysics Data System (ADS)

Ortyl, E.; Chan, S. W.; Nunzi, J.-M.; Kucharski, S.

2006-11-01

Polyurethane polymers containing azo sulfonamide chromophores were obtained by coupling reaction of the precursor polyurethane with corresponding diazonium salts. The chromophores, showing high hyperpolarizability value on molecular scale, were found to undergo orientation by all-optical poling method yielding macroscopic nonlinear optical response. The rate of generation and decay of the second-order nonlinear susceptibility was evaluated as a function of time. It was established that the polymers containing sulfonamide type chromophores showed higher stability of the nonlinear optical signal as compared with those modified with a nitro-acceptor groups of the Disperse Red type.

Isolation of a Moderately Stable but Sensitive Zwitterionic Diazonium Tetrazolyl-1,2,3-triazolate.

PubMed

Klapötke, Thomas M; Krumm, Burkhard; Pflüger, Carolin

2016-07-15

An unexpected formation of a diazonium compound was observed by nitration of an amino substituted triazolyl tetrazole with mixed acid. The crystal structure determination revealed a zwitterionic diazonium tetrazolyl-1,2,3-triazolate, whose constitution was supported by NMR and vibrational spectroscopic analysis. The thermal stability and sensitivity toward impact and friction were determined. In contrast, diazotriazoles are rather unstable and are mainly handled in solution and/or low temperatures, which is not the case for this diazonium tetrazolyl-1,2,3-triazolate, being stable at ambient temperature.

Multifunctional thin film surface

DOEpatents

Brozik, Susan M.; Harper, Jason C.; Polsky, Ronen; Wheeler, David R.; Arango, Dulce C.; Dirk, Shawn M.

2015-10-13

A thin film with multiple binding functionality can be prepared on an electrode surface via consecutive electroreduction of two or more aryl-onium salts with different functional groups. This versatile and simple method for forming multifunctional surfaces provides an effective means for immobilization of diverse molecules at close proximities. The multifunctional thin film has applications in bioelectronics, molecular electronics, clinical diagnostics, and chemical and biological sensing.

Reduced Graphene Oxide-Immobilized Tris(bipyridine)ruthenium(II) Complex for Efficient Visible-Light-Driven Reductive Dehalogenation Reaction.

PubMed

Li, Xiaoyan; Hao, Zhongkai; Zhang, Fang; Li, Hexing

2016-05-18

A sodium benzenesulfonate (PhSO3Na)-functionalized reduced graphene oxide was synthesized via a two-step aryl diazonium coupling and subsequent NaCl ion-exchange procedure, which was used as a support to immobilize tris(bipyridine)ruthenium(II) complex (Ru(bpy)3Cl2) by coordination reaction. This elaborated Ru(bpy)3-rGO catalyst exhibited excellent catalytic efficiency in visible-light-driven reductive dehalogenation reactions under mild conditions, even for ary chloride. Meanwhile, it showed the comparable reactivity with the corresponding homogeneous Ru(bpy)3Cl2 catalyst. This high catalytic performance could be attributed to the unique two-dimensional sheet-like structure of Ru(bpy)3-rGO, which efficiently diminished diffusion resistance of the reactants. Meanwhile, the nonconjugated PhSO3Na-linkage between Ru(II) complex and the support and the very low electrical conductivity of the catalyst inhibited energy/electron transfer from Ru(II) complex to rGO support, resulting in the decreased support-induced quenching effect. Furthermore, it could be easily recycled at least five times without significant loss of catalytic reactivity.

Chemically modulated graphene quantum dot for tuning the photoluminescence as novel sensory probe

NASA Astrophysics Data System (ADS)

Hwang, Eunhee; Hwang, Hee Min; Shin, Yonghun; Yoon, Yeoheung; Lee, Hanleem; Yang, Junghee; Bak, Sora; Lee, Hyoyoung

2016-12-01

A band gap tuning of environmental-friendly graphene quantum dot (GQD) becomes a keen interest for novel applications such as photoluminescence (PL) sensor. Here, for tuning the band gap of GQD, a hexafluorohydroxypropanyl benzene (HFHPB) group acted as a receptor of a chemical warfare agent was chemically attached on the GQD via the diazonium coupling reaction of HFHPB diazonium salt, providing new HFHPB-GQD material. With a help of the electron withdrawing HFHPB group, the energy band gap of the HFHPB-GQD was widened and its PL decay life time decreased. As designed, after addition of dimethyl methyl phosphonate (DMMP), the PL intensity of HFHPB-GQD sensor sharply increased up to approximately 200% through a hydrogen bond with DMMP. The fast response and short recovery time was proven by quartz crystal microbalance (QCM) analysis. This HFHPB-GQD sensor shows highly sensitive to DMMP in comparison with GQD sensor without HFHPB and graphene. In addition, the HFHPB-GQD sensor showed high selectivity only to the phosphonate functional group among many other analytes and also stable enough for real device applications. Thus, the tuning of the band gap of the photoluminescent GQDs may open up new promising strategies for the molecular detection of target substrates.

Chemically modulated graphene quantum dot for tuning the photoluminescence as novel sensory probe

PubMed Central

Hwang, Eunhee; Hwang, Hee Min; Shin, Yonghun; Yoon, Yeoheung; Lee, Hanleem; Yang, Junghee; Bak, Sora; Lee, Hyoyoung

2016-01-01

A band gap tuning of environmental-friendly graphene quantum dot (GQD) becomes a keen interest for novel applications such as photoluminescence (PL) sensor. Here, for tuning the band gap of GQD, a hexafluorohydroxypropanyl benzene (HFHPB) group acted as a receptor of a chemical warfare agent was chemically attached on the GQD via the diazonium coupling reaction of HFHPB diazonium salt, providing new HFHPB-GQD material. With a help of the electron withdrawing HFHPB group, the energy band gap of the HFHPB-GQD was widened and its PL decay life time decreased. As designed, after addition of dimethyl methyl phosphonate (DMMP), the PL intensity of HFHPB-GQD sensor sharply increased up to approximately 200% through a hydrogen bond with DMMP. The fast response and short recovery time was proven by quartz crystal microbalance (QCM) analysis. This HFHPB-GQD sensor shows highly sensitive to DMMP in comparison with GQD sensor without HFHPB and graphene. In addition, the HFHPB-GQD sensor showed high selectivity only to the phosphonate functional group among many other analytes and also stable enough for real device applications. Thus, the tuning of the band gap of the photoluminescent GQDs may open up new promising strategies for the molecular detection of target substrates. PMID:27991584

Covalent functionalization of reduced graphene oxide with porphyrin by means of diazonium chemistry for nonlinear optical performance

PubMed Central

Wang, Aijian; Yu, Wang; Huang, Zhipeng; Zhou, Feng; Song, Jingbao; Song, Yinglin; Long, Lingliang; Cifuentes, Marie P.; Humphrey, Mark G.; Zhang, Long; Shao, Jianda; Zhang, Chi

2016-01-01

Reduced graphene oxide (RGO)-porphyrin (TPP) nanohybrids (RGO-TPP 1 and RGO-TPP 2) were prepared by two synthetic routes that involve functionalization of the RGO using diazonium salts. The microscopic structures, morphology, photophysical properties and nonlinear optical performance of the resultant RGO-TPP nanohybrids were investigated. The covalent bonding of the porphyrin-functionalized-RGO nanohybrid materials was confirmed by Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, and thermogravimetric analysis. Attachment of the porphyrin units to the surface of the RGO by diazotization significantly improves the solubility and ease of processing of these RGO-based nanohybrid materials. Ultraviolet/visible absorption and steady-state fluorescence studies indicate considerable π-π interactions and effective photo-induced electron and/or energy transfer between the porphyrin moieties and the extended π-system of RGO. The nonlinear optical properties of RGO-TPP 1 and RGO-TPP 2 were investigated by open-aperture Z-scan measurements at 532 nm with both 4 ns and 21 ps laser pulses, the results showing that the chemical nanohybrids exhibit improved nonlinear optical properties compared to those of the benchmark material C60, and the constituent RGO or porphyrins. PMID:27011265

Metal-free Synthesis of Ynones from Acyl Chlorides and Potassium Alkynyltrifluoroborate Salts

PubMed Central

Taylor, Cassandra L.; Bolshan, Yuri

2015-01-01

Ynones are a valuable functional group and building block in organic synthesis. Ynones serve as a precursor to many important organic functional groups and scaffolds. Traditional methods for the preparation of ynones are associated with drawbacks including harsh conditions, multiple purification steps, and the presence of unwanted byproducts. An alternative method for the straightforward preparation of ynones from acyl chlorides and potassium alkynyltrifluoroborate salts is described herein. The adoption of organotrifluoroborate salts as an alternative to organometallic reagents for the formation of new carbon-carbon bonds has a number of advantages. Potassium organotrifluoroborate salts are shelf stable, have good functional group tolerance, low toxicity, and a wide variety are straightforward to prepare. The title reaction proceeds rapidly at ambient temperature in the presence of a Lewis acid without the exclusion of air and moisture. Fair to excellent yields may be obtained via reaction of various aryl and alkyl acid chlorides with alkynyltrifluoroborate salts in the presence of boron trichloride. PMID:25742169

Graphene heat dissipating structure

DOEpatents

Washburn, Cody M.; Lambert, Timothy N.; Wheeler, David R.; Rodenbeck, Christopher T.; Railkar, Tarak A.

2017-08-01

Various technologies presented herein relate to forming one or more heat dissipating structures (e.g., heat spreaders and/or heat sinks) on a substrate, wherein the substrate forms part of an electronic component. The heat dissipating structures are formed from graphene, with advantage being taken of the high thermal conductivity of graphene. The graphene (e.g., in flake form) is attached to a diazonium molecule, and further, the diazonium molecule is utilized to attach the graphene to material forming the substrate. A surface of the substrate is treated to comprise oxide-containing regions and also oxide-free regions having underlying silicon exposed. The diazonium molecule attaches to the oxide-free regions, wherein the diazonium molecule bonds (e.g., covalently) to the exposed silicon. Attachment of the diazonium plus graphene molecule is optionally repeated to enable formation of a heat dissipating structure of a required height.

Surface modification of GC and HOPG with diazonium, amine, azide, and olefin derivatives.

PubMed

Tanaka, Mutsuo; Sawaguchi, Takahiro; Sato, Yukari; Yoshioka, Kyoko; Niwa, Osamu

2011-01-04

Surface modification of glassy carbon (GC) and highly oriented pyrolytic graphite (HOPG) was carried out with diazonium, amine, azide, and olefin derivatives bearing ferrocene as an electroactive moiety. Features of the modified surfaces were evaluated by surface concentrations of immobilized molecule, blocking effect of the modified surface against redox reaction, and surface observation using cyclic voltammetry and electrochemical scanning tunneling microscope (EC-STM). The measurement of surface concentrations of immobilized molecule revealed the following three aspects: (i) Diazonium and olefin derivatives could modify substrates with the dense-monolayer concentration. (ii) The surface concentration of immobilized amine derivative did not reach to the dense-monolayer concentration reflecting their low reactivity. (iii) The surface modification with the dense-monolayer concentration was also possible with azide derivative, but the modified surface contained some oligomers produced by the photoreaction of azides. Besides, the blocking effect against redox reaction was observed for GC modified with diazonium derivative and for HOPG modified with diazonium and azide derivatives, suggesting fabrication of a densely modified surface. Finally, the surface observation for HOPG modified with diazonium derivative by EC-STM showed a typical monolayer structure, in which the ferrocene moieties were packed densely at random. On the basis of those results, it was demonstrated that surface modification of carbon substrates with diazonium could afford a dense monolayer similar to the self-assembled monolayer (SAM) formation.

Metal-composite adhesion based on diazonium chemistry.

PubMed

Oweis, Yara; Alageel, Omar; Kozak, Paige; Abdallah, Mohamed-Nur; Retrouvey, Jean-Marc; Cerruti, Marta; Tamimi, Faleh

2017-11-01

Composite resins do not adhere well to dental alloys. This weak bond can result in failure at the composite-metal interface in fixed dental prostheses and orthodontic brackets. The aim of this study was to develop a new adhesive, based on diazonium chemistry, to facilitate chemical bonding between dental alloys and composite resin. Samples of two types of dental alloys, stainless steel and cobalt chromium were primed with a diazonium layer in order to create a surface coating favorable for composite adhesion. Untreated metal samples served as controls. The surface chemical composition of the treated and untreated samples was analyzed by X-ray photoelectron spectroscopy (XPS) and the tensile strength of the bond with composite resin was measured. The diazonium adhesive was also tested for shear bond strength between stainless steel orthodontic brackets and teeth. XPS confirmed the presence of a diazonium coating on the treated metals. The coating significantly increased the tensile and shear bond strengths by three and four folds respectively between the treated alloys and composite resin. diazonium chemistry can be used to develop composite adhesives for dental alloys. Diazonium adhesion can effectively achieve a strong chemical bond between dental alloys and composite resin. This technology can be used for composite repair of fractured crowns, for crown cementation with resin based cements, and for bracket bonding. Copyright © 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Abstracts of AF Materials Laboratory Reports. January 1973 - December 1973

DTIC Science & Technology

1974-07-01

substituted polymers with aryl ether , ketone and sulfone units in the backbone has been studied. The best resins seem to have come from simple...exposed to hostile environments such as heat aging plus salt spray, humid aging , humid aging and elevated temperature cycling, and fatigue...unclassified results of materials and process and radome characterization effort. Environmental exposure including thermal aging resulted in significant

A highly efficient dual-diazonium reagent for protein crosslinking and construction of a virus-based gel.

PubMed

Ma, Dejun; Zhang, Jie; Zhang, Changyu; Men, Yuwen; Sun, Hongyan; Li, Lu-Yuan; Yi, Long; Xi, Zhen

2018-05-09

A new bench-stable reagent with double diazonium sites was designed and synthesized for protein crosslinking. Based on the highly efficient diazonium-Tyr coupling reaction, a direct mixture of the reagent and tobacco mosaic virus led to the formation of a new hydrogel, which could be degraded by chemicals and could be used to encapsulate small molecules for sustained release. Because plant viruses exhibit many chemical characteristics like protein labelling and nucleic acid packaging, the virus-based hydrogel will have large chemical space for further functionalization. Besides, this dual-diazonium reagent should be a generally useful crosslinker for chemical biology and biomaterials.

Pyrrolizine-1,3-dione.

PubMed

McNab, Hamish; Montgomery, James; Parsons, Simon; Tredgett, David G

2010-10-07

Pyrrolizine-1,3-dione 4 was made by oxidation of the alcohol 2 using pyridinium chlorochromate. The dione 4 shows ketone properties (e.g. formation of DNP derivative 11) and, in common with other pyrrolizinones, the lactam unit is readily ring-opened by methanol under basic conditions. The active methylene unit of 4 couples readily with diazonium salts to provide the hydrazone 15 whose structure was confirmed by X-ray crystallography. The 'Meldrumsated' derivative 18 exists exclusively as the tautomer 18F; flash vacuum pyrolysis (FVP) of 18 at 700 degrees C gives the pyronopyrrolizine 20 exclusively. Reaction of 4 with DMF acetal gives the dimethylaminomethylene derivative 22 which exists as a mixture of rotamers at room temperature.

Copper/amino acid catalyzed cross-couplings of aryl and vinyl halides with nucleophiles.

PubMed

Ma, Dawei; Cai, Qian

2008-11-18

Copper-assisted Ullmann-type coupling reactions are valuable transformations for organic synthesis. Researchers have extensively applied these reactions in both academic and industrial settings. However, two important issues, the high reaction temperatures (normally above 150 degrees C) and the stoichiometric amounts of copper necessary, have greatly limited the reaction scope. To solve these problems, we and other groups have recently explored the use of special ligands to promote these coupling reactions. We first showed that the structure of alpha-amino acids can accelerate Cu-assisted Ullmann reactions, leading to the coupling reactions of aryl halides and alpha-amino acids at 80-90 degrees C. In response to these encouraging results, we also discovered that an l-proline ligand facilitated the following transformations: (1) coupling of aryl halides with primary amines, cyclic secondary amines, and N-containing heterocycles at 40-90 degrees C; (2) coupling of aryl halides with sulfinic acid salts at 80-95 degrees C; (3) azidation of aryl halides and vinyl halides with sodium azide at 40-95 degrees C; (4) coupling of aryl halides with activated methylene compounds at 25-50 degrees C. In addition, we found that N,N-dimethylglycine as a ligand facilitated Cu-catalyzed biaryl ether formation at 90 degrees C. Moreover, Sonogashira reactions worked in the absence of palladium and phosphine ligands, forming enamides from vinyl halides and amides at temperatures ranging from ambient temperature up to 80 degrees C. Furthermore, we discovered that an ortho-amide group can accelerate some Ullmann-type reactions. This functional group in combination with other ligand effects allowed for aryl amination or biaryl ether formation at ambient temperature. The coupling between aryl halides and activated methylene compounds even proceeded at -45 degrees C to enantioselectively form a quaternary carbon center. Taking advantage of these results, we developed several novel approaches for the synthesis of pharmaceutically important heterocycles: 1,2-disubstituted benzimidazoles, polysubstituted indoles, N-substituted 1,3-dihydrobenzimidazol-2-ones, and substituted 3-acyl oxindoles. Our results demonstrate that an l-proline or N,N-dimethylglycine ligand can facilitate most typical Ullmann-type reactions, with reactions occurring under relatively mild conditions and using only 2-20 mol % copper catalysts. These conveniently available and inexpensive catalytic systems not only accelerate the reactions but also tolerate many more functional groups. Thus, they should find considerable application in organic synthesis.

Atom-scale covalent electrochemical modification of single-layer graphene on SiC substrates by diaryliodonium salts

DOE PAGES

Gearba, Raluca I.; Mueller, Kory M.; Veneman, Peter A.; ...

2015-05-09

Owing to its high conductivity, graphene holds promise as an electrode for energy devices such as batteries and photovoltaics. However, to this end, the work function and doping levels in graphene need to be precisely tuned. One promising route for modifying graphene’s electronic properties is via controlled covalent electrochemical grafting of molecules. We show that by employing diaryliodonium salts instead of the commonly used diazonium salts, spontaneous functionalization is avoided. This then allows for precise tuning of the grafting density. Moreover, by employing bis(4-nitrophenyl)iodonium(III) tetrafluoroborate (DNP) salt calibration curves, the surface functionalization density (coverage) of glassy carbon was controlled usingmore » cyclic voltammetry in varying salt concentrations. These electro-grafting conditions and calibration curves translated directly over to modifying single layer epitaxial graphene substrates (grown on insulating 6H-SiC (0 0 0 1)). In addition to quantifying the functionalization densities using electrochemical methods, samples with low grafting densities were characterized by low-temperature scanning tunneling microscopy (LT-STM). We show that the use of buffer-layer free graphene substrates is required for clear observation of the nitrophenyl modifications. Furthermore, atomically-resolved STM images of single site modifications were obtained, showing no preferential grafting at defect sites or SiC step edges as supposed previously in the literature. Most of the grafts exhibit threefold symmetry, but occasional extended modifications (larger than 4 nm) were observed as well.« less

Electrochemical supercapacitors

DOEpatents

Rudge, Andrew J.; Ferraris, John P.; Gottesfeld, Shimshon

1996-01-01

A new class of electrochemical capacitors provides in its charged state a positive electrode including an active material of a p-doped material and a negative electrode including an active material of an n-doped conducting polymer, where the p-doped and n-doped materials are separated by an electrolyte. In a preferred embodiment, the positive and negative electrode active materials are selected from conducting polymers consisting of polythiophene, polymers having an aryl group attached in the 3-position, polymers having aryl and alkyl groups independently attached in the 3- and 4-positions, and polymers synthesized from bridged dimers having polythiophene as the backbone. A preferred electrolyte is a tetraalykyl ammonium salt, such as tetramethylammonium trifluoromethane sulphonate (TMATFMS), that provides small ions that are mobile through the active material, is soluble in acetonitrile, and can be used in a variety of capacitor configurations.

Palladium coupling catalysts for pharmaceutical applications.

PubMed

Doucet, Henri; Hierso, Jean-Cyrille

2007-11-01

This review discusses recent advances made in the area of palladium-catalyzed coupling reactions and describes a selection of the catalytic systems that are useful in the preparation of valuable compounds for the pharmaceutical industry. Most of these types of syntheses have used either simple palladium salts or palladium precursors associated with electron-rich mono- or bidentate phosphine ligands as catalysts. For some reactions, ligands such as triphenyl phosphine, 1,1'-bis(diphenylphosphino)ferrocene, a carbene or a bipyridine have also been employed. Several new procedures for the Suzuki cross-coupling reaction, the activation of aryl chlorides, the functionalization of aromatics and the synthesis of heteroaromatics are discussed. The C-H activation/ functionalization reactions of aryl and heteroaryl derivatives have emerged as powerful tools for the preparation of biaryl compounds, and the recent procedures and catalysts employed in this promising field are also highlighted herein.

Preparation of catalytically active, covalent α-polylysine-enzyme conjugates via UV/vis-quantifiable bis-aryl hydrazone bond formation.

PubMed

Grotzky, Andrea; Manaka, Yuichi; Kojima, Taisuke; Walde, Peter

2011-01-10

Covalent UV/vis-quantifiable bis-aryl hydrazone bond formation was investigated for the preparation of conjugates between α-poly-d-lysine (PDL) and either α-chymotrypsin (α-CT) or horseradish peroxidase (HRP). PDL and the enzymes were first modified via free amino groups with the linking reagents succinimidyl 6-hydrazinonicotinate acetone hydrazone (S-HyNic, at pH 7.6) and succinimidyl 4-formylbenzoate (S-4FB, at pH 7.2), respectively. The modified PDL and enzymes were then conjugated at pH 4.7, whereby polymer chains carrying several enzymes were obtained. Kinetics of the bis-aryl hydrazone bond formation was investigated spectrophotometrically at 354 nm. Retention of the enzymatic activity after conjugate formation was confirmed by using the substrates N-succinimidyl-l-Ala-l-Ala-l-Pro-l-Phe-p-nitroanilide (for α-CT) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS, for HRP). Thus, not only a mild and efficient preparation and convenient quantification of a conjugate between the polycationic α-polylysine and enzymes could be shown, but also the complete preservation of the enzymatic activity.

Metal-doped organic gels and method thereof

DOEpatents

Satcher, Jr., Joe H.; Baumann, Theodore F.

2003-09-02

Disclosed herein is a sol-gel polymerization process for synthesizing metal-doped organic gels. The process polymerizes metal salts of hydroxylated benzenes or hydroxylated benzene derivatives with alkyl or aryl aldehydes to form metal-doped, wet, organic gels. The gels can then be dried by supercritical solvent extraction to form metal-doped aerogels or by evaporation to form metal-doped xerogels. The aerogels and xerogels can then be pyrolyzed.

Mesoporous imine-based organic polymer: catalyst-free synthesis in water and application in CO2 conversion.

PubMed

Yu, Xiaoxiao; Yang, Zhenzhen; Guo, Shien; Liu, Zhenghui; Zhang, Hongye; Yu, Bo; Zhao, Yanfei; Liu, Zhimin

2018-06-22

A mesoporous imine-functionalized organic polymer (Imine-POP) was prepared based on the reaction of an aryl ammonium salt with an aromatic aldehyde in water without any catalyst and template. The Pd coordinated Imine-POP exhibited high catalytic activity for the N-formylation of amines with CO2/H2 at 100 °C, affording a series of formamides in high yields.

Metal-doped organic gels and method thereof

DOEpatents

Satcher, Jr., Joe H.; Baumann, Theodore F.

2007-10-23

Disclosed herein is a sol-gel polymerization process for synthesizing metal-doped organic gels. The process polymerizes metal salts of hydroxylated benzenes or hydroxylated benzene derivatives with alkyl or aryl aldehydes to form metal-doped, wet, organic gels. The gels can then be dried by supercritical solvent extraction to form metal-doped aerogels or by evaporation to form metal-doped xerogels. The aerogels and xerogels can then be pyrolyzed.

Cu-mediated C–H 18F-fluorination of electron-rich (hetero)arenes

DOE Office of Scientific and Technical Information (OSTI.GOV)

McCammant, Matthew S.; Thompson, Stephen; Brooks, Allen F.

This communication describes a method for the nucleophilic radiofluorination of electron-rich arenes. The reaction involves the initial C(sp 2)–H functionalization of an electron-rich arene with MesI(OH)OTs to form a (mesityl)(aryl)iodonium salt. This salt is then used in situ in a Cu-mediated radiofluorination with [ 18F]KF. This approach leverages the stability and availability of electron-rich arene starting materials to enable mild late-stage radiofluorination of toluene, anisole, aniline, pyrrole, and thiophene derivatives. Finally, the radiofluorination has been automated to access a 41 mCi dose of an 18F-labeled nimesulide derivative in high (2800 ± 700 Ci/mmol) specific activity.

Cu-mediated C–H 18F-fluorination of electron-rich (hetero)arenes

DOE PAGES

McCammant, Matthew S.; Thompson, Stephen; Brooks, Allen F.; ...

2017-06-30

This communication describes a method for the nucleophilic radiofluorination of electron-rich arenes. The reaction involves the initial C(sp 2)–H functionalization of an electron-rich arene with MesI(OH)OTs to form a (mesityl)(aryl)iodonium salt. This salt is then used in situ in a Cu-mediated radiofluorination with [ 18F]KF. This approach leverages the stability and availability of electron-rich arene starting materials to enable mild late-stage radiofluorination of toluene, anisole, aniline, pyrrole, and thiophene derivatives. Finally, the radiofluorination has been automated to access a 41 mCi dose of an 18F-labeled nimesulide derivative in high (2800 ± 700 Ci/mmol) specific activity.

A Boron Protecting Group Strategy for 1,2-Azaborines.

PubMed

Baggett, Andrew W; Liu, Shih-Yuan

2017-10-25

Upon reaction with either molecular oxygen or di-tert-butylperoxide in the presence of a simple copper(I) salt and an alcohol, a range of 1,2-azaborines readily exchange B-alkyl or B-aryl moieties for B-alkoxide fragments. This transformation allows alkyl and aryl groups to serve for the first time as removable protecting groups for the boron position of 1,2-azaborines during reactions that are not compatible with the easily modifiable B-alkoxide moiety. This reaction can be applied to synthesize a previously inaccessible BN isostere of ethylbenzene, a compound of interest in biomedical research. A sequence of epoxide ring opening using N-deprotonated 1,2-azaborines followed by an intramolecular version of the boron deprotection reaction can be applied to access the first examples of BN isosteres of dihydrobenzofurans and benzofurans, classes of compounds that are important to medicinal chemistry and natural product synthesis.

Facially Selective Cu-catalyzed Carbozincation of Cyclopropenes Using Arylzinc Reagents Formed by Sequential I/Mg/Zn exchange

PubMed Central

Tarwade, Vinod; Selvaraj, Ramajeyam; Fox, Joseph M.

2012-01-01

Described is a Cu-catalyzed directed carbozincation of cyclopropenes with organozinc reagents prepared by I/Mg/Zn exchange. This protocol broadens the scope with respect to functional group tolerance and enables use of aryl iodide precursors, rather than purified diorganozinc precursors. Critical to diastereoselectivity of the carbozincation step is the removal of magnesium halide salts after transmetallation with ZnCl2. PMID:23035947

Stille coupling via C-N bond cleavage

NASA Astrophysics Data System (ADS)

Wang, Dong-Yu; Kawahata, Masatoshi; Yang, Ze-Kun; Miyamoto, Kazunori; Komagawa, Shinsuke; Yamaguchi, Kentaro; Wang, Chao; Uchiyama, Masanobu

2016-09-01

Cross-coupling is a fundamental reaction in the synthesis of functional molecules, and has been widely applied, for example, to phenols, anilines, alcohols, amines and their derivatives. Here we report the Ni-catalysed Stille cross-coupling reaction of quaternary ammonium salts via C-N bond cleavage. Aryl/alkyl-trimethylammonium salts [Ar/R-NMe3]+ react smoothly with arylstannanes in 1:1 molar ratio in the presence of a catalytic amount of commercially available Ni(cod)2 and imidazole ligand together with 3.0 equivalents of CsF, affording the corresponding biaryl with broad functional group compatibility. The reaction pathway, including C-N bond cleavage step, is proposed based on the experimental and computational findings, as well as isolation and single-crystal X-ray diffraction analysis of Ni-containing intermediates. This reaction should be widely applicable for transformation of amines/quaternary ammonium salts into multi-aromatics.

Grafting of activated carbon cloths for selective adsorption

NASA Astrophysics Data System (ADS)

Gineys, M.; Benoit, R.; Cohaut, N.; Béguin, F.; Delpeux-Ouldriane, S.

2016-05-01

Chemical functionalization of an activated carbon cloth with 3-aminophthalic acid and 4-aminobenzoic acid groups by the in situ formation of the corresponding diazonium salt in aqueous acidic solution is reported. The nature and amount of selected functions on an activated carbon surface, in particular the grafted density, were determined by potentiometric titration, elemental analysis and X-ray photoelectron spectroscopy (XPS). The nanotextural properties of the modified carbon were explored by gas adsorption. Functionalized activated carbon cloth was obtained at a discrete grafting level while preserving interesting textural properties and a large porous volume. Finally, the grafting homogeneity of the carbon surface and the nature of the chemical bonding were investigated using Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) technique.

Synthesis and Evaluation of Curcuminoid Analogues as Antioxidant and Antibacterial Agents.

PubMed

Emam, Dalia R; Alhajoj, Ahmad M; Elattar, Khaled M; Kheder, Nabila A; Fadda, Ahmed A

2017-06-11

Diazocoupling reaction of curcumin with different diazonium salts of p -toluidine, 2-aminopyridine, and 4-aminoantipyrine in pyridine yielded the arylhydrazones 2a - c . Arylhydrazone of p -toluidine reacted with urea, thiourea, and guanidine nitrate to produce 5,6-dihydropyrimidines. Further reaction of 2a with 2,3-diaminopyrdine in sodium ethoxide solution yielded 1 H -pyrido[2,3- b ][1,4]diazepine derivative. Bis (2,5-dihydroisoxazole) is obtained from the reaction of 2a with hydroxylamine hydrochloride, while its reactions with hydrazines afforded the respective 4,5-dihydro-1 H -pyrazoles. The target compounds were evaluated as antioxidant and antibacterial agents. The tested compounds showed good to moderate activities compared to ascorbic acid and chloramphenicol, respectively.

Optical Excitation of Carbon Nanotubes Drives Localized Diazonium Reactions

PubMed Central

2016-01-01

Covalent chemistries have been widely used to modify carbon nanomaterials; however, they typically lack the precision and efficiency required to directly engineer their optical and electronic properties. Here, we show, for the first time, that visible light which is tuned into resonance with carbon nanotubes can be used to drive their functionalization by aryldiazonium salts. The optical excitation accelerates the reaction rate 154-fold (±13) and makes it possible to significantly improve the efficiency of covalent bonding to the sp2 carbon lattice. Control experiments suggest that the reaction is dominated by a localized photothermal effect. This light-driven reaction paves the way for precise nanochemistry that can directly tailor carbon nanomaterials at the optical and electronic levels. PMID:27588432

Hg(ii) and Pd(ii) complexes with a new selenoether bridged biscarbene ligand: efficient mono- and bis-arylation of methyl acrylate with a pincer biscarbene Pd(ii) precatalyst.

PubMed

Rishu; Prashanth, Billa; Bawari, Deependra; Mandal, Ushnish; Verma, Aditya; Choudhury, Angshuman Roy; Singh, Sanjay

2017-05-16

Two equivalents of 1-benzyl-3-bromoethylbenzimidazolium bromide couple with Na 2 Se to produce the first selenoether bridged bis-benzimidazolium salt (LH 2 )Br 2 . The nitrate (LH 2 )(NO 3 ) 2 and tetrafluoroborate (LH 2 )(BF 4 ) 2 salts were also synthesized from (LH 2 )Br 2 . The reaction of Hg(OAc) 2 with (LH 2 )Br 2 gave the first pseudo pincer carbene mercury complex, [Hg(L-κ 2 C)][HgBr 4 ] (C1). Different complexes of Pd(ii) with selenoether bridged carbene were obtained using (LH 2 )Br 2 and (LH 2 )(NO 3 ) 2 . Syntheses of these complexes were dependent on the counter anion and the temperature. Thus, the pincer type ionic complex [PdBr(L-κ 3 CSeC)]Br (C2) was isolated at 80 °C and the pseudo pincer type neutral complex cis-[PdBr 2 (L-κ 2 C)] (C3) was isolated at room temperature from (LH 2 )Br 2 and Pd(OAc) 2 in DMSO. The nitrate precursor (LH 2 )(NO 3 ) 2 on palladation with Pd(OAc) 2 afforded [Pd(L-κ 4 C Bz CSeC)]NO 3 (C4) showing an unprecedented intramolecular metallation at the ortho position of the benzyl wingtip of the benzimidazole moiety. The ligand salts and metal complexes have been characterized using HRMS, heteronuclear NMR and IR spectroscopy. Single crystal X-ray structures of the ligand salts (LH 2 )Br 2 and (LH 2 )(BF 4 ) 2 and complexes C1-C4 have also been elucidated. Complex C2 showed good activity for C-C coupling in the mono-Heck reaction of methyl acrylate and arylbromides. Interestingly, the less common bis-arylation was also observed with deactivated arylbromides as the result of double-Heck coupling.

Highly selective biaryl cross-coupling reactions between aryl halides and aryl Grignard reagents: a new catalyst combination of N-heterocyclic carbenes and iron, cobalt, and nickel fluorides.

PubMed

Hatakeyama, Takuji; Hashimoto, Sigma; Ishizuka, Kentaro; Nakamura, Masaharu

2009-08-26

Combinations of N-heterocyclic carbenes (NHCs) and fluoride salts of the iron-group metals (Fe, Co, and Ni) have been shown to be excellent catalysts for the cross-coupling reactions of aryl Grignard reagents (Ar(1)MgBr) with aryl and heteroaryl halides (Ar(2)X) to give unsymmetrical biaryls (Ar(1)-Ar(2)). Iron fluorides in combination with SIPr, a saturated NHC ligand, catalyze the biaryl cross-coupling between various aryl chlorides and aryl Grignard reagents in high yield and high selectivity. On the other hand, cobalt and nickel fluorides in combination with IPr, an unsaturated NHC ligand, exhibit interesting complementary reactivity in the coupling of aryl bromides or iodides; in contrast, with these substrates the iron catalysts show a lower selectivity. The formation of homocoupling byproducts is suppressed markedly to less than 5% in most cases by choosing the appropriate metal fluoride/NHC combination. The present catalyst combinations offer several synthetic advantages over existing methods: practical synthesis of a broad range of unsymmetrical biaryls without the use of palladium catalysts and phosphine ligands. On the basis of stoichiometric control experiments and theoretical studies, the origin of the unique catalytic effect of the fluoride counterion can be ascribed to the formation of a higher-valent heteroleptic metalate [Ar(1)MF(2)]MgBr as the key intermediate in our proposed catalytic cycle. First, stoichiometric control experiments revealed the stark differences in chemical reactivity between the metal fluorides and metal chlorides. Second, DFT calculations indicate that the initial reduction of di- or trivalent metal fluoride in the wake of transmetalation with PhMgCl is energetically unfavorable and that formation of a divalent heteroleptic metalate complex, [PhMF(2)]MgCl (M = Fe, Co, Ni), is dominant in the metal fluoride system. The heteroleptic ate-complex serves as a key reactive intermediate, which undergoes oxidative addition with PhCl and releases the biaryl cross-coupling product Ph-Ph with reasonable energy barriers. The present cross-coupling reaction catalyzed by iron-group metal fluorides and an NHC ligand provides a highly selective and practical method for the synthesis of unsymmetrical biaryls as well as the opportunity to gain new mechanistic insights into the metal-catalyzed cross-coupling reactions.

Taming hazardous chemistry in flow: the continuous processing of diazo and diazonium compounds.

PubMed

Deadman, Benjamin J; Collins, Stuart G; Maguire, Anita R

2015-02-02

The synthetic utilities of the diazo and diazonium groups are matched only by their reputation for explosive decomposition. Continuous processing technology offers new opportunities to make and use these versatile intermediates at a range of scales with improved safety over traditional batch processes. In this minireview, the state of the art in the continuous flow processing of reactive diazo and diazonium species is discussed. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Diazonium-functionalized horseradish peroxidase immobilized via addressable electrodeposition: direct electron transfer and electrochemical detection.

PubMed

Polsky, Ronen; Harper, Jason C; Dirk, Shawn M; Arango, Dulce C; Wheeler, David R; Brozik, Susan M

2007-01-16

A simple one-step procedure is introduced for the preparation of diazonium-enzyme adducts. The direct electrically addressable deposition of diazonium-modified enzymes is examined for electrochemical sensor applications. The deposition of diazonium-horseradish peroxidase leads to the direct electron transfer between the enzyme and electrode exhibiting a heterogeneous rate constant, ks, of 10.3 +/- 0.7 s-1 and a DeltaEp of 8 mV (v = 150 mV/s). The large ks and low DeltaEp are attributed to the intimate contact between enzyme and electrode attached by one to three phenyl molecules. Such an electrode shows high nonmediated catalytic activity toward H2O2 reduction. Future generations of arrayed electrochemical sensors and studies of direct electron transfer of enzymes can benefit from protein electrodes prepared by this method.

Platinum(0)-mediated C-O bond activation of ethers via an SN2 mechanism.

PubMed

Ortuño, Manuel A; Jasim, Nasarella A; Whitwood, Adrian C; Lledós, Agustí; Perutz, Robin N

2016-11-29

A computational study of the C(methyl)-O bond activation of fluorinated aryl methyl ethers by a platinum(0) complex Pt(PCyp 3 ) 2 (Cyp = cyclopentyl) (N. A. Jasim, R. N. Perutz, B. Procacci and A. C. Whitwood, Chem. Commun., 2014, 50, 3914) demonstrates that the reaction proceeds via an S N 2 mechanism. Nucleophilic attack of Pt(0) generates an ion pair consisting of a T-shaped platinum cation with an agostic interaction with a cyclopentyl group and a fluoroaryloxy anion. This ion-pair is converted to a 4-coordinate Pt(ii) product trans-[PtMe(OAr F )(PCyp 3 ) 2 ]. Structure-reactivity correlations are fully consistent with this mechanism. The Gibbs energy of activation is calculated to be substantially higher for aryl methyl ethers without fluorine substituents and higher still for alkyl methyl ethers. These conclusions are in accord with the experimental results. Further support was obtained in an experimental study of the reaction of Pt(PCy 3 ) 2 with 2,3,5,6-tetrafluoro-4-allyloxypyridine yielding the salt of the Pt(η 3 -allyl) cation and the tetrafluoropyridinolate anion [Pt(PCy 3 ) 2 (η 3 -allyl)][OC 5 NF 4 ]. The calculated activation energy for this reaction is significantly lower than that for fluorinated aryl methyl ethers.

Long life lithium batteries with stabilized electrodes

DOEpatents

Amine, Khalil; Liu, Jun; Vissers, Donald R; Lu, Wenquan

2015-04-21

The present invention relates to non-aqueous electrolytes having electrode stabilizing additives, stabilized electrodes, and electrochemical devices containing the same. Thus the present invention provides electrolytes containing an alkali metal salt, a polar aprotic solvent, and an electrode stabilizing additive. In certain electrolytes, the alkali metal salt is a bis(chelato)borate and the additives include substituted or unsubstituted linear, branched or cyclic hydrocarbons comprising at least one oxygen atom and at least one aryl, alkenyl or alkynyl group. In other electrolytes, the additives include a substituted aryl compound or a substituted or unsubstituted heteroaryl compound wherein the additive comprises at least one oxygen atom. There are also provided methods of making the electrolytes and batteries employing the electrolytes. The invention also provides for electrode materials. Cathodes of the present invention may be further stabilized by surface coating the particles of the spinel or olivine with a material that can neutralize acid or otherwise lessen or prevent leaching of the manganese or iron ions. In some embodiments the coating is polymeric and in other embodiments the coating is a metal oxide such as ZrO.sub.2, TiO.sub.2, ZnO, WO.sub.3, Al.sub.2O.sub.3, MgO, SiO.sub.2, SnO.sub.2 AlPO.sub.4, Al(OH).sub.3, a mixture of any two or more thereof.

Direct Electrochemistry of Bilirubin Oxidase from Magnaporthe orizae on Covalently-Functionalized MWCNT for the Design of High-Performance Oxygen-Reducing Biocathodes.

PubMed

Gentil, Solène; Carrière, Marie; Cosnier, Serge; Gounel, Sébastien; Mano, Nicolas; Le Goff, Alan

2018-06-12

Herein, the direct electrochemistry of bilirubin oxidase from Magnaporthe orizae (MoBOD) was studied on CNTs functionalized by electrografting several types of diazonium salts. The functionalization induces favorable or unfavorable orientation of MoBOD, the latter being compared to the well-known BOD from Myrothecium verrucaria (MvBOD). On the same nanostructured electrodes, MoBOD can surpass MvBOD in terms of both current densities and minimal overpotentials. Added to the fact that MoBOD is also highly active at the gas-diffusion electrode (GDE), these findings make MoBOD one of the MCOs with the highest catalytic activity towards the oxygen reduction reaction (ORR). © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

UV-vis, IR and 1H NMR spectroscopic studies of some mono- and bis-azo-compounds based on 2,7-dihydroxynaphthalene and aniline derivatives

NASA Astrophysics Data System (ADS)

Issa, Raafat M.; Fayed, Tarek A.; Awad, Mohammed K.; El-Kony, Sanaa M.

2005-12-01

The absorption spectra of mono- and bis-azo-derivatives obtained by coupling the diazonium salts of aromatic amines and 2,7-dihydroxynaphthalene have been studied in six organic solvents. The different absorption bands have been assigned and the effect of solvents on the charge transfer band is also discussed. The diagnostic IR spectral bands and 1H NMR signals are assigned and discussed in relation to molecular structure. Also, semi-empirical molecular orbital calculations using the atom superposition and electron delocalization molecular orbital (ASED-MO) theory have been performed to investigate the molecular and electronic structures of these compounds. According to these calculations, an intramolecular hydrogen bonding is essential for stabilization of such molecules.

Saturated Heterocyclic Aminosulfonyl Fluorides: New Scaffolds for Protecting-Group-Free Synthesis of Sulfonamides.

PubMed

Zhersh, Sergey A; Blahun, Oleksandr P; Sadkova, Iryna V; Tolmachev, Andrey A; Moroz, Yurii S; Mykhailiuk, Pavel K

2018-06-12

Cyclic saturated aminosulfonyl fluorides were synthesized as their HCl salts. The compounds were found to be stable upon storage and could be used for the protecting-group-free synthesis of sulfonamides. In the presence of the -SO 2 F group, the nitrogen atom could be modified by means of acylation, arylation, or reductive amination to give products that have high potential for the synthesis of bioactive compounds. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Inhibitors of glycogen synthase 3 kinase

DOEpatents

Schultz, Peter; Ring, David B.; Harrison, Stephen D.; Bray, Andrew M.

2000-01-01

Compounds of formula 1: ##STR1## wherein R.sub.1 is alkyl, cycloalkyl, aryl, aralkyl, heteroaryl, or heteroaralkyl, substituted with 0-3 substituents selected from lower alkyl, halo, hydroxy, lower alkoxy, amino, lower alkyl-amino, and nitro; R.sub.2 is hydroxy, amino, or lower alkoxy; R.sub.3 is H, lower alkyl, lower acyl, lower alkoxy-acyl, or amnino-acyl; R.sub.4 is H or lower alkyl; and pharmaceutically acceptable salts and esters thereof; are effective inhibitors of GSK3.

Inhibitors of glycogen synthase 3 kinase

DOEpatents

Schultz, Peter; Ring, David B.; Harrison, Stephen D.; Bray, Andrew M.

2006-05-30

Compounds of formula 1: ##STR00001## wherein R.sub.1 is alkyl, cycloalkyl, aryl, aralkyl, heteroaryl, or heteroaralkyl, substituted with 0 3 substituents selected from lower alkyl, halo, hydroxy, lower alkoxy, amino, lower alkyl-amino, and nitro; R.sub.2 is hydroxy, amino, or lower alkoxy; R.sub.3 is H, lower alkyl, lower acyl, lower alkoxy-acyl, or amino-acyl; R.sub.4 is H or lower alkyl; and pharmaceutically acceptable salts and esters thereof; are effective inhibitors of GSK3.

Water-soluble triazabutadienes that release diazonium species upon protonation under physiologically relevant conditions.

PubMed

Kimani, Flora W; Jewett, John C

2015-03-23

Triazabutadienes are an understudied structural motif that have remarkable reactivity once rendered water-soluble. It is shown that these molecules readily release diazonium species in a pH-dependent manner in a series of buffer solutions with pH ranges similar to those found in cells. Upon further development, we expect that this process will be well suited to cargo-release strategies and organelle-specific bioconjugation reactions. These compounds offer one of the mildest ways of generating diazonium species in aqueous solutions. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis and biological evaluation of aryl-oxadiazoles as inhibitors of Mycobacterium tuberculosis.

PubMed

Martinez-Grau, Maria Angeles; Valcarcel, Isabel C Gonzalez; Early, Julie V; Gessner, Richard Klaus; de Melo, Candice Soares; de la Nava, Eva Maria Martin; Korkegian, Aaron; Ovechkina, Yulia; Flint, Lindsay; Gravelle, Anisa; Cramer, Jeff W; Desai, Prashant V; Street, Leslie J; Odingo, Joshua; Masquelin, Thierry; Chibale, Kelly; Parish, Tanya

2018-06-01

Despite increased research efforts to find new treatments for tuberculosis in recent decades, compounds with novel mechanisms of action are still required. We previously identified a series of novel aryl-oxadiazoles with anti-tubercular activity specific for bacteria using butyrate as a carbon source. We explored the structure activity relationship of this series. Structural modifications were performed in all domains to improve potency and physico-chemical properties. A number of compounds displayed sub-micromolar activity against M. tuberculosis utilizing butyrate, but not glucose as the carbon source. Compounds showed no or low cytotoxicity against eukaryotic cells. Three compounds were profiled in mouse pharmacokinetic studies. Plasma clearance was low to moderate but oral exposure suggested solubility-limited drug absorption in addition to first pass metabolism. The presence of a basic nitrogen in the linker slightly increased solubility, and salt formation optimized aqueous solubility. Our findings suggest that the 1,3,4-oxadiazoles are useful tools and warrant further investigation. Copyright © 2018 The Author(s). Published by Elsevier Ltd.. All rights reserved.

Ab initio and density functional force field studies on the IR spectra and structure of diazonium dicyanomethylide (diazodicyanomethane)

NASA Astrophysics Data System (ADS)

Georgieva, Miglena K.

2004-03-01

The structure of diazonium dicyanomethylide (diazodicyanomethane) +N 2-C(CN) 2-↔N 2C(CN) 2 has been studied on the basis of ab initio HF, MP2 and DFT BLYP force field calculations, as well as of literature IR spectra and X-ray diffraction structural data. The results have been compared with those obtained for a series of chemical relatives of the title compound, i.e. molecules, push-pull molecules, anions and zwitterions, containing α-dicyano or diazo fragments, and especially substituted ammonium dicyanomethylides and diazomethane +N 2-CH 2-↔N 2CH 2. It has been found on the basis of spectral, bond length, bond order and electric charge analyses that the diazonium (or carbanionic, left) canonical form is much more important for the title zwitterion, than the corresponding one for diazomethane. So, the title compound can be named (and considered as) both diazonium dicyanomethylide and dicyanodiazomethane.

Mechanism of the coupling of diazonium to single-walled carbon nanotubes and its consequences.

PubMed

Schmidt, Grégory; Gallon, Salomé; Esnouf, Stéphane; Bourgoin, Jean-Philippe; Chenevier, Pascale

2009-01-01

On the tube: The coupling of diazonium ions onto single-walled carbon nanotubes is shown to proceed through a radical chain reaction by kinetic analysis of the absorption peak drop (see picture). Radical species are also revealed by ESR. Metallic (m) nanotubes play a special catalytic role in the functionalization of semiconducting (sc) nanotubes.Due to its simplicity and versatility, diazonium coupling is the most widely used method for carbon nanotube (CNT) functionalization to increase CNT processability and add new functionalities. Yet, its mechanism is so far mostly unknown. Herein, we use kinetic analysis to shed light on this complex mechanism. A free-radical chain reaction is revealed by absorption spectroscopy and ESR. Metallic CNTs are shown to play an unexpected catalytic role. The step determining the selectivity towards metallic CNTs is identified by a Hammett correlation. A mechanistic model is proposed that predicts reactivity and selectivity as a function of diazonium electrophilicity and metallic-to-semiconducting CNT ratio, thus opening perspectives of controlled high-yield functionalization and purification.

Synthesis, structure and solvatochromic properties of some novel 5-arylazo-6-hydroxy-4-phenyl-3-cyano-2-pyridone dyes

PubMed Central

2012-01-01

Background A series of some novel arylazo pyridone dyes was synthesized from the corresponding diazonium salt and 6-hydroxy-4-phenyl-3-cyano-2-pyridone using a classical reaction for the synthesis of the azo compounds. Results The structure of the dyes was confirmed by UV-vis, FT-IR, 1H NMR and 13C NMR spectroscopic techniques and elemental analysis. The solvatochromic behavior of the dyes was evaluated with respect to their visible absorption properties in various solvents. Conclusions The azo-hydrazone tautomeric equilibration was found to depend on the substituents as well as on the solvent. The geometry data of the investigated dyes were obtained using DFT quantum-chemical calculations. The obtained calculational results are in very good agreement with the experimental data. PMID:22824496

Polymer modified sol-gel materials for photochromic applications

NASA Astrophysics Data System (ADS)

Janik, Ryszard; Kucharski, Stanislaw

2006-08-01

The chromophoric materials were prepared by copolymerization of various methacrylic monomers. The incorporation of the chromophore groups was done by coupling reaction of diazonium salts of the sulfonamide such as: sulfomethazine or sulfisomidine). The copolymers having free OH groups were able to react with 3-triethoxypropyl isocyanate forming intermediates used to prepare hybrid transparent films by sol-gel technique. The films of both copolymers as well as of hybrid sol-gel structures showed photochromic properties via trans-cis isomerization of the diazo groups. The absorption maximum of the trans form was ca. 435-445 nm depending on chemical composition of the material. Illumination of the films with coherent laser beams (two-beam coupling) resulted in formation of diffraction grating. The diffraction efficiency reached 4-5 % and refractive index modulation was in the range up to 0.0032.

Diazonium Functionalisation of Carbon Nanotubes for Specific Orientation of Multicopper Oxidases: Controlling Electron Entry Points and Oxygen Diffusion to the Enzyme.

PubMed

Lalaoui, Noémie; Holzinger, Michael; Le Goff, Alan; Cosnier, Serge

2016-07-18

We report the controlled orientation of bilirubin oxidases (BOD) from Myrothecium verrucaria on multiwalled carbon nanotubes (MWCNTs) functionalised by electrografting of 6-carboxynaphthalenediazonium and 4-(2-aminoethyl)benzenediazonium salts. On negatively charged naphthoate-modified MWCNTs, a high-potential (0.44 V vs. SCE) oxygen reduction electrocatalysis is observed, occurring via the T1 copper centre. On positively charged ammonium-modified MWCNTs, a low-potential (0.15 V) oxygen reduction electrocatalysis is observed, occurring through a partially oxidised state of the T2/T3 trinuclear copper cluster. Finally, chemically modified naphthoate MWCNTs exhibit high bioelectrocatalytic current densities of 3.9 mA cm(-2) under air at gas-diffusion electrode. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A facile route to steady redox-modulated nitroxide spin-labeled surfaces based on diazonium chemistry.

PubMed

Cougnon, Charles; Boisard, Séverine; Cador, Olivier; Dias, Marylène; Levillain, Eric; Breton, Tony

2013-05-18

A TEMPO derivative was covalently grafted onto carbon and gold surfaces via the diazonium chemistry. The acid-dependent redox properties of the nitroxyl group were exploited to elaborate electro-switchable magnetic surfaces. ESR characterization demonstrated the reversible and permanent magnetic character of the material.

Total Synthesis of Strychnine.

PubMed

Lee, Geun Seok; Namkoong, Gil; Park, Jisook; Chen, David Y-K

2017-11-16

The total synthesis of the flagship Strychnos indole alkaloid, strychnine, has been accomplished. The developed synthetic sequence features a novel vinylogous 1,4-addition, a challenging iodinium salt mediated silyl enol ether arylation, a palladium-catalyzed Heck reaction, and a streamlined late-stage conversion to strychnine. Furthermore, an application of asymmetric counterion-directed catalysis (ACDC) in the context of target-oriented organic synthesis has been rendered access to an optically active material. The synthetic sequence described herein represents the most concise entry to optically active strychnine to date. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chemoselective chromium(II)-catalyzed cross-coupling reactions of dichlorinated heteroaromatics with functionalized aryl grignard reagents.

PubMed

Steib, Andreas K; Kuzmina, Olesya M; Fernandez, Sarah; Malhotra, Sushant; Knochel, Paul

2015-01-26

Chromium(II) chloride catalyzes the chemoselective cross-coupling reaction of dichloropyridines with a range of functionalized (hetero)aromatic Grignard reagents at room temperature. Functional groups, such as esters and acetals, are well tolerated in this transformation. Previously challenging substrates, quinolines and isoquinolines, participate in the selective Cr-catalyzed cross-coupling in cyclopentyl methyl ether (CPME) as the solvent. The effective purging of Cr salts is demonstrated by using various solid supports. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A chiral aluminum solvating agent (CASA) for 1H NMR chiral analysis of alcohols at low temperature.

PubMed

Seo, Min-Seob; Jang, Sumin; Kim, Hyunwoo

2018-03-16

A chiral aluminum solvating agent (CASA) was demonstrated to be a general and efficient reagent for 1H NMR chiral analysis of alcohols. The sodium salt of the CASA (CASA-Na) showed a complete baseline peak separation of the hydroxyl group for various chiral alcohols including primary, secondary, and tertiary alcohols with alkyl and aryl substituents in CD3CN. Due to the weak intermolecular interaction, 1H NMR measurement at low temperature (-40 to 10 °C) was required.

Electrolyte solutions including a phosphoranimine compound, and energy storage devices including same

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klaehn, John R.; Dufek, Eric J.; Rollins, Harry W.

An electrolyte solution comprising at least one phosphoranimine compound and a metal salt. The at least one phosphoranimine compound comprises a compound of the chemical structure ##STR00001## where X is an organosilyl group or a tert-butyl group and each of R.sup.1, R.sup.2, and R.sup.3 is independently selected from the group consisting of an alkyl group, an aryl group, an alkoxy group, or an aryloxy group. An energy storage device including the electrolyte solution is also disclosed.

Characterization and growth analysis of two types of thin films formed on copper surfaces: An inorganic chromium containing film and an organic film formed via reduction of diazonium ions

NASA Astrophysics Data System (ADS)

Hurley, Belinda Louise

Surface enhanced Raman scattering was used to observe interactions of dilute CrVI solutions with silver and copper surfaces in situ. Using silver as a model surface, CrIII was observed at the near monolayer level, and the spectra were compared to those from CrIII oxyhydroxide species and CrIII/Cr VI mixed oxide. Similar experiments were conducted with copper surfaces and 785 nm excitation. Upon exposure of a copper surface to CrVI solution, the characteristic copper oxide Raman bands disappeared, and a Cr III band increased in intensity over a period of ˜20 hours. The intensity of the CrIII band on copper became self limiting after the formation of several CrIII monolayers, as supported by chronoamperometry experiments. This CrIII spectrum was stable after CrVI was removed from the solution provided the potential remained negative of -200 mV vs. Ag/AgCl. The results support the conclusion that CrVI is reductively adsorbed to copper at the near neutral pH and open circuit potentials expected for Cu/Al alloys in field applications. The CrIII film is stable and strongly inhibits oxygen reduction at the treated copper surface. Copper surfaces and polished Aluminum Alloy 2024 T3 substrates were derivatized at open circuit potential with arenediazonium salts in both aprotic and aqueous media. Raman spectroscopy confirmed the presence of a derivatized film on the substrates before and after exposure to boiling water and sonication in acetone. Preliminary experiments to test these films for corrosion inhibition proved unsuccessful. Aluminum and copper substrates were prepared and used for x-ray photoelectron spectroscopy (XPS) analysis of the derivatization results. In the copper experiments, one surface was native oxide copper, predominantly in the form of Cu2O, and one surface was predominantly Cu 0. Results of the XPS analysis indicate the presence of a Cu-O-C linkage and possibly a Cu-C covalent bond between the aryl ring and the copper substrate. XPS results also indicate the formation of multilayers on both types of copper surfaces with different percentages of azo coupling within the multilayers on the two surfaces. These easily prepared, covalently bonded organic films could be used for applications currently fulfilled with self-absorbed monolayers and Langmuir Blodgett films.

Azidoimidazolinium Salts: Safe and Efficient Diazo-transfer Reagents and Unique Azido-donors.

PubMed

Kitamura, Mitsuru

2017-07-01

2-Azido-1,3-dimethylimidazolinium chloride (ADMC) and its corresponding hexafluorophosphate (ADMP) were found to be efficient diazo-transfer reagents to various organic compounds. ADMC was prepared by the reaction of 2-chloro-1,3-dimethylimidazolinium chloride (DMC) and sodium azide. ADMP was isolated as a crystal having good thermal stability and low explosibility. ADMC and ADMP reacted with 1,3-dicarbonyl compounds under mild basic conditions to give 2-diazo-1,3-dicarbonyl compounds in high yields, which were easily isolated in virtue of the high water solubility of the by-products. ADMP showed high diazo-transfer ability to primary amines even in the absence of metal salt such as Cu(II). Using this diazotization approach, various alkyl/aryl azides were directly obtained from their corresponding primary amines in high yields. Furthermore, naphthols reacted with ADMC to give the corresponding diazonaphthoquinones in good to high yields. In addition, 2-azido-1,3-dimethylimidazolinium salts were employed as azide-transfer and migratory amidation reagents. © 2017 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Absolute configuration in 4-alkyl- and 4-aryl-3,4-dihydro-2(1H)-pyrimidones: a combined theoretical and experimental investigation.

PubMed

Uray, G; Verdino, P; Belaj, F; Kappe, C O; Fabian, W M

2001-10-05

Structural features (orientation of the carboxyl group, ring puckering), electronic absorption, and circular dichroism spectra of 4-alkyl- and 4-aryl-dihydropyrimidones 1-5 are calculated by semiempirical (AM1, INDO/S), ab initio (HF/6-31G, CIS/6-31G, RPA/6-31G), and density functional theory (B3LYP/6-31G) methods. These calculations allow an assignment of the absolute configuration by comparison of simulated and experimental CD spectra. Although the ab initio methods greatly overestimate electronic transition energies, the general appearance of the experimental CD spectra is quite nicely reproduced by these calculations. Thus, comparison of experimental with calculated CD spectra is a reliable tool for the assignment of the absolute configuration. For 4-methyl derivatives 1, the first enantiopure DHPM examples with no additional aromatic substituent, the stereochemistry at C4 provided by the theoretical results is confirmed by X-ray structure determination of the diastereomeric salt 6. Additional support is the consistent HPLC elution order found for all investigated DHPMs on a cellulose-derived chiral stationary phase.

Surface properties of hydrogenated nanodiamonds: a chemical investigation.

PubMed

Girard, H A; Petit, T; Perruchas, S; Gacoin, T; Gesset, C; Arnault, J C; Bergonzo, P

2011-06-28

Hydrogen terminations (C-H) confer to diamond layers specific surface properties such as a negative electron affinity and a superficial conductive layer, opening the way to specific functionalization routes. For example, efficient covalent bonding of diazonium salts or of alkene moieties can be performed on hydrogenated diamond thin films, owing to electronic exchanges at the interface. Here, we report on the chemical reactivity of fully hydrogenated High Pressure High Temperature (HPHT) nanodiamonds (H-NDs) towards such grafting, with respect to the reactivity of as-received NDs. Chemical characterizations such as FTIR, XPS analysis and Zeta potential measurements reveal a clear selectivity of such couplings on H-NDs, suggesting that C-H related surface properties remain dominant even on particles at the nanoscale. These results on hydrogenated NDs open up the route to a broad range of new functionalizations for innovative NDs applications development. This journal is © the Owner Societies 2011

Hydrophilic Modification of Multi-Walled Carbon Nanotube for Building Photonic Crystals with Enhanced Color Visibility and Mechanical Strength.

PubMed

Li, Feihu; Tang, Bingtao; Xiu, Jinghai; Zhang, Shufen

2016-04-28

Low color visibility and poor mechanical strength of polystyrene (PS) photonic crystal films have been the main shortcomings for the potential applications in paints or displays. This paper presents a simple method to fabricate PS/MWCNTs (multi-walled carbon nanotubes) composite photonic crystal films with enhanced color visibility and mechanical strength. First, MWCNTs was modified through radical addition reaction by aniline 2,5-double sulfonic acid diazonium salt to generate hydrophilic surface and good water dispersity. Then the MWCNTs dispersion was blended with PS emulsion to form homogeneous PS/MWCNTs emulsion mixtures and fabricate composite films through thermal-assisted method. The obtained films exhibit high color visibility under natural light and improved mechanical strength owing to the light-adsorption property and crosslinking effect of MWCNTs. The utilization of MWCNTs in improving the properties of photonic crystals is significant for various applications, such as in paints and displays.

Label-free impedimetric immunosensor for sensitive detection of ochratoxin A.

PubMed

Radi, Abd-Elgawad; Muñoz-Berbel, Xavier; Lates, Vasilica; Marty, Jean-Louis

2009-03-15

A novel label-free electrochemical impedimetric immunosensor for sensitive detection of ochratoxin A (OTA) was reported. A two-step reaction protocol was elaborated to modify the gold electrode. The electrode was first derivatized by electrochemical reduction of in situ generated 4-carboxyphenyl diazonium salt (4-CPDS) in acidic aqueous solution yielded stable 4-carboxyphenyl (4-CP) monolayer. The ochratoxin A antibody was then immobilized making use of the carbodiimide chemistry. The steps of the immunosensor elaboration and the immunochemical reaction between ochratoxin A and the surface-bound antibody were interrogated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The impedance change, due to the specific immuno-interaction at the immunosensor surface was utilized to detect ochratoxin A. The increase in electron-transfer resistance (DeltaR(et)) values was linearly proportional to the concentration of OTA in the range of 1-20ngmL(-1), with a detection limit of 0.5ngmL(-1).

DFT, FT-IR, FT-Raman and NMR studies of 4-(substituted phenylazo)-3,5-diacetamido-1H-pyrazoles

NASA Astrophysics Data System (ADS)

Kınalı, Selin; Demirci, Serkan; Çalışır, Zühre; Kurt, Mustafa; Ataç, Ahmet

2011-05-01

We present a detailed analysis of the structural and vibrational spectra of some novel azo dyes. 2-(Substituted phenylazo)malononitriles were synthesized by the coupling reaction of the diazonium salts, which were prepared with the use of various aniline derivatives with malononitrile, and then 4-(substituted phenylazo)-3,5-diamino-1H-pyrazole azo dyes were obtained via the ring closure of the azo compounds with hydrazine monohydrate. The experimental and theoretical vibrational spectra of azo dyes were studied. The structural and spectroscopic analysis of the molecules were carried out by using Becke's three-parameters hybrid functional (B3LYP) and density functional harmonic calculations. The 1H nuclear magnetic resonance (NMR) chemical shifts of the azo dye molecules were calculated using the gauge-invariant-atomic orbital (GIAO) method. The calculated vibrational wavenumbers and chemical shifts were compared with the experimental data of the molecules.

CYP450 2B4 covalently attached to carbon and gold screen printed electrodes by diazonium salt and thiols monolayers.

PubMed

Alonso-Lomillo, M A; Yardimci, C; Domínguez-Renedo, O; Arcos-Martínez, M J

2009-02-02

An easy covalent immobilization method used to develop enzyme biosensors based on carbon and gold screen printed electrodes (SPCEs and gold SPEs) is described. The linkage of biomolecules through 4-nitrobenzenediazonium tetrafluoroborate, mercaptopropionic acid and thioctic acid monolayers has been attempted using bare SPCEs and gold SPEs, as well as gold nanoparticles (AuNPs) modified SPCEs and gold SPEs. Direct covalent attachment of Cytochrome P450 2B4 (CYP450 2B4) to the transducer has been carried out by carbodiimide and hydroxysuccinimide. Experimental variables in the immobilization process and in the chronoamperometric determination of Phenobarbital (PB) have been optimized by the experimental design methodology. Reproducibility of the different biosensors has been checked under the optimum conditions, yielding values lower than 6%. Their performances have been shown by the determination of PB in pharmaceutical drugs.

Photogeneration of singlet oxygen by the phenothiazine derivatives covalently bound to the surface-modified glassy carbon

NASA Astrophysics Data System (ADS)

Blacha-Grzechnik, Agata; Piwowar, Katarzyna; Krukiewicz, Katarzyna; Koscielniak, Piotr; Szuber, Jacek; Zak, Jerzy K.

2016-05-01

The selected group of four amine-derivatives of phenothiazine was covalently grafted to the glassy carbon surface in the four-step procedure consisting of the electrochemical reduction of the diazonium salt followed by the electrochemical and chemical post-modification steps. The proposed strategy involves the bonding of linker molecule to which the photosensitizer is attached. The synthesized organic layers were characterized by means of cyclic voltammetry, XPS and Raman Spectroscopy. It was shown that the phenothiazines immobilized via proposed strategy retain their photochemical properties and are able to generate 1O2 when activated by the laser radiation. The effectiveness of in situ singlet oxygen generation by those new solid photoactive materials was determined by means of UVVis spectroscopy. The reported, covalently modified solid surfaces may find their application as the singlet oxygen photogenerators in the fine chemicals' synthesis or in the wastewater treatment.

XPS-nanocharacterization of organic layers electrochemically grafted on the surface of SnO2 thin films to produce a new hybrid material coating

NASA Astrophysics Data System (ADS)

Drevet, R.; Dragoé, D.; Barthés-Labrousse, M. G.; Chaussé, A.; Andrieux, M.

2016-10-01

This work presents the synthesis and the characterization of hybrid material thin films obtained by the combination of two processes. The electrochemical grafting of organic layers made of carboxyphenyl moieties is carried out from the reduction of a diazonium salt on tin dioxide (SnO2) thin films previously deposited on Si substrates by metal organic chemical vapor deposition (MOCVD). Since the MOCVD experimental parameters impact the crystal growth of the SnO2 layer (i.e. its morphology and its texturation), various electrochemical grafting models can occur, producing different hybrid materials. In order to evidence the efficiency of the electrochemical grafting of the carboxyphenyl moieties, X-ray Photoelectron Spectroscopy (XPS) is used to characterize the first nanometers in depth of the synthesized hybrid material layer. Then three electrochemical grafting models are proposed.

Interactions of p-Nitrobenzene Diazonium Fluoroborate and Analogs with the Active Sites of Acetylcholine-Receptor and -Esterase*

PubMed Central

Mautner, Henry G.; Bartels, Eva

1970-01-01

p-Nitrobenzene diazonium fluoroborate (NDF) is a potent inhibitor of the carbamylcholine-induced depolarization of the electroplax and of acetylcholinesterase. It probably forms covalent bonds with the acetylcholine-receptor and -esterase at the active site of the proteins. Its inhibitory strength is at least the same as that of trimethylammonium diazonium fluoroborate (TDF). The p-acetoxy analog, with its weaker electron-withdrawing group, is about ten times weaker as an inhibitor than the trimethylammonium or p-nitro analogs, both of which have strong electron-withdrawing groups. After treatment of the electroplax preparation with dithiothreitol, NDF remains an irreversible receptor-inhibitor, while TDF becomes a potent reversible receptor-activator. TDF is self-inhibitory: applied before reduction, it no longer depolarizes. Although the first observations on TDF suggested that the compound labels both proteins by virtue of the steric complementary of its trimethylammonium group to a negative subsite in the proteins, the present study indicates that it is the positively charged diazonium group that reacts with the active sites of the proteins to form a covalent bond with an appropriate amino-acid residue. PMID:5272331

Unprecedented Self-Organized Monolayer of a Ru(II) Complex by Diazonium Electroreduction.

PubMed

Nguyen, Van Quynh; Sun, Xiaonan; Lafolet, Frédéric; Audibert, Jean-Frédéric; Miomandre, Fabien; Lemercier, Gilles; Loiseau, Frédérique; Lacroix, Jean-Christophe

2016-08-03

A new heteroleptic polypyridyle Ru(II) complex was synthesized and deposited on surface by the diazonium electroreduction process. It yields to the covalent grafting of a monolayer. The functionalized surface was characterized by XPS, electrochemistry, AFM, and STM. A precise organization of the molecules within the monolayer is observed with parallel linear stripes separated by a distance of 3.8 nm corresponding to the lateral size of the molecule. Such organization suggests a strong cooperative process in the deposition process. This strategy is an original way to obtain well-controlled and stable functionalized surfaces for potential applications related to the photophysical properties of the grafted chromophore. As an exciting result, it is the first example of a self-organized monolayer (SOM) obtained using diazonium electroreduction.

Room-temperature chromium(II)-catalyzed direct arylation of pyridines, aryl oxazolines, and imines using arylmagnesium reagents.

PubMed

Kuzmina, Olesya M; Knochel, Paul

2014-10-03

We report a CrCl2-catalyzed oxidative arylation of various pyridines, aryl oxazolines, and aryl imines using aromatic Grignard reagents in the presence of 2,3-dichlorobutane (DCB). Most of the reactions proceed rapidly at 25 °C and do not require any additional ligand. Benzo[h]quinoline, 2-arylpyridine, aryl oxazoline, and imines were successfully arylated in good yields under these conditions. A TMS-substituent was used to prevent double arylation. After oxidative cross-coupling the TMS-group was further converted to a second ortho-aryl substituent. Remarkably, inexpensive aryl N-butylimine derivatives are excellent substrates for this oxidative arylation.

XPS and NRA investigations during the fabrication of gold nanostructured functionalized screen-printed sensors for the detection of metallic pollutants

NASA Astrophysics Data System (ADS)

Jasmin, Jean-Philippe; Miserque, Frédéric; Dumas, Eddy; Vickridge, Ian; Ganem, Jean-Jacques; Cannizzo, Caroline; Chaussé, Annie

2017-03-01

An all covalent nanostructured lead sensor was built by the successive grafting of gold nanoparticles and carboxylic ligands at the surface of self-adhesive carbon screen-printed electrodes (SPEs). Surface analysis techniques were used in each step in order to investigate the structuration of this sensor. The self-adhesive surfaces were made from the electrochemical grafting of p-phenylenediamine at the surface of the SPEs via diazonium salts chemistry. The quantity of grafted aniline functions, estimated by Nuclear Reaction Analysis (NRA) performed with p-phenylenediamine labelled with 15N isotope, is in agreement with an almost complete coverage of the electrode surface. The subsequent diazotization of the aniline functions at the surface of the SPEs was performed; X-ray Photoelectron Spectroscopy (XPS) allowed us to consider a quantitative conversion of the aniline functions into diazonium moieties. The spontaneous grafting of gold nanoparticles on the as-obtained reactive surfaces ensures the nanostructuration of the material, and XPS studies showed that the covalent bonding of the gold nanoparticles at the surface of the SPEs induces a change both in the Au-4f (gold nanoparticles) and Cl-2p (carbon ink) core level signals. These unusual observations are explained by an interaction between the carbon ink constituting the substrate and the gold nanoparticles. Heavy and toxic metals are considered of major environmental concern because of their non-biodegradability. In a final step, the grafting of the carboxylic ligands at the surface of the SPEs and an accumulation step in the presence of lead(II) cations allowed us to evidence the interest of nanostructured materials as metallic pollutants sensors.

Functionalization of multilayer fullerenes (carbon nano-onions) using diazonium compounds and "click" chemistry.

PubMed

Flavin, Kevin; Chaur, Manuel N; Echegoyen, Luis; Giordani, Silvia

2010-02-19

A novel versatile approach for the functionalization of multilayer fullerenes (carbon nano-onions) has been developed, which involves the facile introduction of a variety of simple functionalities onto their surface by treatment with in situ generated diazonium compounds. This approach is complemented by use of "click" chemistry which was used for the covalent introduction of more complex porphyrin molecules.

Charge transfer from TiO2 into adsorbed benzene diazonium compounds

NASA Astrophysics Data System (ADS)

Merson, A.; Dittrich, Th.; Zidon, Y.; Rappich, J.; Shapira, Yoram

2004-08-01

Electron transfer from sol-gel-prepared TiO2 into adsorbed benzene diazonium compounds has been investigated using cyclic voltammetry, x-ray photoelectron spectroscopy, contact potential difference, and surface photovoltage spectroscopy. The results show that the potential of maximum electron transfer depends strongly on the dipole moment of the benzene compound. Two reactive surface sites at which electron transfer occurs have been identified.

Aryl triolborates: novel reagent for copper-catalyzed N arylation of amines, anilines, and imidazoles.

PubMed

Yu, Xiao-Qiang; Yamamoto, Yasunori; Miyaura, Norio

2008-09-01

The N arylation of primary and secondary aliphatic amines, anilines, and imidazoles with novel potassium aryl triolborates was carried out in the presence of a reoxidant and a catalytic amount of Cu(OAc)(2) (10 mol %). Aryl triolborates were found to be better reagents than aryl boronic acids or potassium aryl trifluoroborates as the former achieved high yields under mild conditions. Coupling of primary and secondary aliphatic amines to give N-aryl amines in excellent yields was performed under oxygen atmosphere. The reactions of anilines and imidazoles to provide N-aryl anilines and N-aryl imidazoles in good yields proceeded smoothly when trimethylamine N-oxide was used as an oxidant.

Process for derivatizing carbon nanotubes with diazonium species

NASA Technical Reports Server (NTRS)

Tour, James M. (Inventor); Bahr, Jeffrey L. (Inventor); Yang, Jiping (Inventor)

2007-01-01

The invention incorporates new processes for the chemical modification of carbon nanotubes. Such processes involve the derivatization of multi- and single-wall carbon nanotubes, including small diameter (ca. 0.7 nm) single-wall carbon nanotubes, with diazonium species. The method allows the chemical attachment of a variety of organic compounds to the side and ends of carbon nanotubes. These chemically modified nanotubes have applications in polymer composite materials, molecular electronic applications and sensor devices. The methods of derivatization include electrochemical induced reactions thermally induced reactions (via in-situ generation of diazonium compounds or pre-formed diazonium compounds), and photochemically induced reactions. The derivatization causes significant changes in the spectroscopic properties of the nanotubes. The estimated degree of functionality is ca. 1 out of every 20 to 30 carbons in a nanotube bearing a functionality moiety. Such electrochemical reduction processes can be adapted to apply site-selective chemical functionalization of nanotubes. Moreover, when modified with suitable chemical groups, the derivatized nanotubes are chemically compatible with a polymer matrix, allowing transfer of the properties of the nanotubes (such as, mechanical strength or electrical conductivity) to the properties of the composite material as a whole. Furthermore, when modified with suitable chemical groups, the groups can be polymerized to form a polymer that includes carbon nanotubes ##STR00001##.

Synthesis of 2-aryl and 3-aryl benzo[b]furan thioethers using aryl sulfonyl hydrazides as sulfenylation reagents.

PubMed

Zhao, Xia; Zhang, Lipeng; Lu, Xiaoyu; Li, Tianjiao; Lu, Kui

2015-03-06

An efficient, metal-free protocol used to synthesize aryl benzo[b]furan thioethers based on the I2-catalyzed cross-coupling of benzo[b]furans as well as the electrophilic cyclization of 2-alkynylphenol derivatives with aryl sulfonyl hydrazides was developed. Various 2-aryl and 3-aryl benzo[b]furan thioethers were obtained in moderate to good yields.

Direct functionalization processes: a journey from palladium to copper to iron to nickel to metal-free coupling reactions.

PubMed

Mousseau, James J; Charette, André B

2013-02-19

The possibility of finding novel disconnections for the efficient synthesis of organic molecules has driven the interest in developing technologies to directly functionalize C-H bonds. The ubiquity of these bonds makes such transformations attractive, while also posing several challenges. The first, and perhaps most important, is the selective functionalization of one C-H bond over another. Another key problem is inducing reactivity at sites that have been historically unreactive and difficult to access without prior inefficient prefunctionalization. Although remarkable advances have been made over the past decade toward solving these and other problems, several difficult tasks remain as researchers attempt to bring C-H functionalization reactions into common use. The functionalization of sp(3) centers continues to be challenging relative to their sp and sp(2) counterparts. Directing groups are often needed to increase the effective concentration of the catalyst at the targeted reaction site, forming thermodynamically stable coordination complexes. As such, the development of removable or convertible directing groups is desirable. Finally, the replacement of expensive rare earth reagents with less expensive and more sustainable catalysts or abandoning the use of catalysts entirely is essential for future practicality. This Account describes our efforts toward solving some of these quandaries. We began our work in this area with the direct arylation of N-iminopyridinium ylides as a universal means to derivatize the germane six-membered heterocycle. We found that the Lewis basic benzoyl group of the pyridinium ylide could direct a palladium catalyst toward insertion at the 2-position of the pyridinium ring, forming a thermodynamically stable six-membered metallocycle. Subsequently we discovered the arylation of the benzylic site of 2-picolonium ylides. The same N-benzoyl group could direct a number of inexpensive copper salts to the 2-position of the pyridinium ylide, which led to the first description of a direct copper-catalyzed alkenylation onto an electron-deficient arene. This particular directing group offers two advantages: (1) it can be easily appended and removed to reveal the desired pyridine target, and (2) it can be incorporated in a cascade process in the preparation of pharmacologically relevant 2-pyrazolo[1,5-a]pyridines. This work has solved some of the challenges in the direct arylation of nonheterocyclic arenes, including reversing the reactivity often observed with such transformations. Readily convertible directing groups were applied to facilitate the transformation. We also demonstrated that iron can promote intermolecular arylations effectively and that the omission of any metal still permits intramolecular arylation reactions. Lastly, we recently discovered a nickel-catalyzed intramolecular arylation of sp(3) C-H bonds. Our mechanistic investigations of these processes have elucidated radical pathways, opening new avenues in future direct C-H functionalization reactions.

Electrografting of diazonium-functionalized polyoxometalates: synthesis, immobilisation and electron-transfer characterisation from glassy carbon.

PubMed

Rinfray, Corentin; Izzet, Guillaume; Pinson, Jean; Gam Derouich, Sarra; Ganem, Jean-Jacques; Combellas, Catherine; Kanoufi, Frédéric; Proust, Anna

2013-10-04

Polyoxometalates (POMs) are attractive candidates for the rational design of multi-level charge-storage materials because they display reversible multi-step reduction processes in a narrow range of potentials. The functionalization of POMs allows for their integration in hybrid complementary metal oxide semiconductor (CMOS)/molecular devices, provided that fine control of their immobilisation on various substrates can be achieved. Owing to the wide applicability of the diazonium route to surface modification, a functionalized Keggin-type POM [PW11 O39 {Ge(p-C6 H4 -CC-C6 H4 -${{\\rm N}{{+\\hfill \\atop 2\\hfill}}}$)}](3-) bearing a pending diazonium group was prepared and subsequently covalently anchored onto a glassy carbon electrode. Electron transfer with the immobilised POM was thoroughly investigated and compared to that of the free POM in solution. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Anti-cancer agents based on 4-(hetero)Ary1-1,2,5-oxadiazol-3-yl Amino derivatives and a method of making

DOEpatents

Gakh, Andrei A.; Krasavin, Mikhail; Karapetian, Ruben; Rufanov, Konstantin A.; Konstantinov, Igor; Godovykh, Elena; Soldatkina, Olga; Sosnov, Andrey V.

2013-01-29

The present disclosure relates to novel compounds that can be used as anti-cancer agents in the prostate cancer therapy. ##STR00001## In particular, the invention relates N-substituted derivatives of 4-(hetero)aryl-1,2,5-oxadiazol-3-yl amines having the structural Formula (I) and (II), stereoisomers, tautomers, racemics, prodrugs, metabolites thereof, or pharmaceutically acceptable salt and/or solvate thereof. Meaning of R1 and R2 in the Formula (I) and (II) are defined in claim 1. The invention also relates to methods for preparing said compounds, and to pharmaceutical compositions comprising said compounds.

Copper Mediated Fluorination of Aryl Iodides

PubMed Central

Fier, Patrick S.; Hartwig, John F.

2012-01-01

The synthesis of aryl fluorides has been a topic of considerable interest because of the importance of aryl fluorides in pharmaceuticals, agrochemicals and materials. The stability, reactivity and biological properties of aryl fluorides can be distinct from those of the corresponding arenes. Methods for the synthesis of aryl fluorides, however, are limited. We report the conversion of a diverse set of aryl iodides to the corresponding aryl fluorides. This reaction occurs with a cationic copper reagent and silver fluoride. Preliminary results suggest this reaction is enabled by a facile reductive elimination from a cationic aryl copper(III) fluoride. PMID:22709145

Palladium-Catalyzed Direct C–H Arylation of Cyclic Enaminones with Aryl Iodides

PubMed Central

Yu, Yi-Yun; Bi, Lei

2013-01-01

A ligand-free method for the Pd-catalyzed direct arylation of cyclic enaminones using aryl iodides was developed. This method can be applied to a wide range of cyclic enaminones and aryl iodides with excellent C5-regioselectivity. Using widely available aryl iodides, the generality of this transformation provides easy access to a variety of 3-arylpiperidine structural motifs. PMID:23750615

Well-defined flake-like polypyrrole grafted graphene nanosheets composites as electrode materials for supercapacitors with enhanced cycling stability

NASA Astrophysics Data System (ADS)

Wang, Xue; Wang, Tingmei; Yang, Chao; Li, Haidong; Liu, Peng

2013-12-01

Well-defined flake-like polypyrrole grafted graphene nanosheets composites (PPy-g-GNS) were fabricated by the in-situ chemical oxidative grafting polymerization of pyrrole in the presence of the 4-aminophenyl modified graphene nanosheets (AP-GNS), which were prepared via the coupling reaction of the graphene nanosheets (GNS) with diazonium salt. The flake-like PPy-g-GNS composite showed the high conductivity at room temperature. A maximum discharge capacitance of 191.2 F/g at the scan rate of 10 mV/s could be achieved in the three-electrode cell electrochemical testing in 1.0 mol/L NaNO3 electrolyte solution. It is higher than those of the AP-GNS, pure PPy, and the GNS/PPy composite prepared with the unmodified graphene nanosheets (GNS). The flake-like PPy-g-GNS composites also exhibited the excellent electrochemical stability even after 1000 cycles. It revealed the synergistic effect between the conducting polymer and the carbon-based support.

Development and characterization of a voltammetric carbon-fiber microelectrode pH sensor.

PubMed

Makos, Monique A; Omiatek, Donna M; Ewing, Andrew G; Heien, Michael L

2010-06-15

This work describes the development and characterization of a modified carbon-fiber microelectrode sensor capable of measuring real-time physiological pH changes in biological microenvironments. The reagentless sensor was fabricated under ambient conditions from voltammetric reduction of the diazonium salt Fast Blue RR onto a carbon-fiber surface in aprotic media. Fast-scan cyclic voltammetry was used to probe redox activity of the p-quinone moiety of the surface-bound molecule as a function of pH. In vitro calibration of the sensor in solutions ranging from pH 6.5 to 8.0 resulted in a pH-dependent anodic peak potential response. Flow-injection analysis was used to characterize the modified microelectrode, revealing sensitivity to acidic and basic changes discernible to 0.005 pH units. Furthermore, the modified electrode was used to measure dynamic in vivo pH changes evoked during neurotransmitter release in the central nervous system of the microanalytical model organism Drosophila melanogaster.

Molecularly imprinted electrochemical sensor based on amine group modified graphene covalently linked electrode for 4-nonylphenol detection.

PubMed

Chen, Hong-Jun; Zhang, Zhao-Hui; Cai, Rong; Chen, Xing; Liu, Yu-Nan; Rao, Wei; Yao, Shou-Zhuo

2013-10-15

In this work, an imprinted electrochemical sensor based on electrochemical reduced graphene covalently modified carbon electrode was developed for the determination of 4-nonylphenol (NP). An amine-terminated functional graphene oxide was covalently modified onto the electrode surface with diazonium salt reactions to improve the stability and reproducibility of the imprinted sensor. The electrochemical properties of each modified electrodes were investigated with differential pulse voltammetry (DPV). The electrochemical characteristic of the imprinted sensor was also investigated using electrochemical impedance spectroscopy (EIS) in detail. The response currents of the imprinted electrode exhibited a linear relationship toward 4-nonylphenol concentration ranging from 1.0 × 10(-11) to 1.0 × 10(-8) gm L(-1) with the detection limit of 3.5 × 10(-12) gm L(-1) (S/N=3). The fabricated electrochemical imprinted sensor was successfully applied to the detection of 4-nonylphenol in rain and lake water samples. Crown Copyright © 2013 Published by Elsevier B.V. All rights reserved.

Direct on-chip DNA synthesis using electrochemically modified gold electrodes as solid support

NASA Astrophysics Data System (ADS)

Levrie, Karen; Jans, Karolien; Schepers, Guy; Vos, Rita; Van Dorpe, Pol; Lagae, Liesbet; Van Hoof, Chris; Van Aerschot, Arthur; Stakenborg, Tim

2018-04-01

DNA microarrays have propelled important advancements in the field of genomic research by enabling the monitoring of thousands of genes in parallel. The throughput can be increased even further by scaling down the microarray feature size. In this respect, microelectronics-based DNA arrays are promising as they can leverage semiconductor processing techniques with lithographic resolutions. We propose a method that enables the use of metal electrodes for de novo DNA synthesis without the need for an insulating support. By electrochemically functionalizing gold electrodes, these electrodes can act as solid support for phosphoramidite-based synthesis. The proposed method relies on the electrochemical reduction of diazonium salts, enabling site-specific incorporation of hydroxyl groups onto the metal electrodes. An automated DNA synthesizer was used to couple phosphoramidite moieties directly onto the OH-modified electrodes to obtain the desired oligonucleotide sequence. Characterization was done via cyclic voltammetry and fluorescence microscopy. Our results present a valuable proof-of-concept for the integration of solid-phase DNA synthesis with microelectronics.

Application To Bilayer System With Water-Soluble Contrast Enhancing Material

NASA Astrophysics Data System (ADS)

Yabuta, Mitsuo; Ito, Naoki; Yamazaki, Hiroyuki; Nakayama, Toshimasa

1987-09-01

We have developed ,a water-soluble contrast enhancing material, TAD-436 ( Tokyo Ohka. Anti-Defocus Material ) which is consisted of a water-soluble diazonium salt as bleaching compounds and a water-soluble anion type polymer as binder polymers. Needless to say that water is used as solvent in TAD; therefore, it can be spincoated directly on a positive photoresist layer of a quinonediazide-novolak resin type without causing intermixing and furtheremore the bilayer can be developed without stripping TAD immediately after exposure. TAD shows a satisfactory bleaching characteristics on g-line, increases r-value of underlying photoresist and reduces the thickness loss of photoresist layer in unexposed area. Application to bilayer system with TAD will raise the resolution of underlying photoresist and when the focus depth is changed it will make the change in the resist profile small. As the result of it, the notches in the resist patterns on steps is reduced, making the difference in the linewidth between the top and the bottom of steps small.

Development and Characterization of a Voltammetric Carbon-fiber Microelectrode pH Sensor

PubMed Central

Makos, Monique A.; Omiatek, Donna M.; Ewing, Andrew G.; Heien, Michael L.

2010-01-01

This work describes the development and characterization of a modified carbon-fiber microelectrode sensor capable of measuring real-time physiological pH changes in biological microenvironments. The reagentless sensor was fabricated under ambient conditions from voltammetric reduction of the diazonium salt Fast Blue RR onto a carbon-fiber surface in aprotic media. Fast-scan cyclic voltammetry was used to probe redox activity of the p-quinone moiety of the surface-bound molecule as a function of pH. In vitro calibration of the sensor in solutions ranging from pH 6.5 to 8.0 resulted in a pH-dependent anodic peak potential response. Flow-injection analysis was used to characterize the modified microelectrode, revealing sensitivity to acidic and basic changes discernable to 0.005 pH units. Furthermore, the modified electrode was used to measure dynamic in vivo pH changes evoked during neurotransmitter release in the central nervous system of the microanalytical model organism Drosophila melanogaster. PMID:20380393

Palladium-Catalyzed Indole, Pyrrole, and Furan Arylation by Aryl Chlorides

PubMed Central

Nadres, Enrico T.; Lazareva, Anna; Daugulis, Olafs

2011-01-01

The palladium-catalyzed direct arylation of indoles, pyrroles, and furans by aryl chlorides has been demonstrated. The method employs a palladium acetate catalyst, 2-(dicyclohexylphosphino)-biphenyl ligand, and an inorganic base. Electron-rich and electron-poor aryl chlorides as well as chloropyridine coupling partners can be used and arylated heterocycles are obtained in moderate to good yields. Optimization of base, ligand, and solvent is required for achieving best results. PMID:21192652

A Novel, Diazonium-Phenolic Resin Two-Layer Resist System Utilizing Photoinduced Interfacial Insolubilization

NASA Astrophysics Data System (ADS)

Uchino, Shou-ichi; Iwayanagi, Takao; Ueno, Takumi; Hashimoto, Michiaki; Nonogaki, Saburo

1987-08-01

This paper deals with a negative two-layer photoresist system utilizing a photoinduced insolubilization process at the interface. The bottom layer is a phenolic resin either with or without aromatic azide and the top layer is a photosensitive layer comprised of an aromatic diazonium compound and a water soluble polymer. Upon exposure to light, the diazo compound decomposes to cause insolubilization at the interface between the two layers. The system exhibits high contrast due to the combination of interfacial insolubilization and contrast enhancement by photobleaching of the diazonium compound. Patterns of 0.5 um lines and spaces are obtained using an i-line stepper and a resist system containing 4-diazo-N,N-dimethylaniline chloride zinc chloride in the top layer and 3-(4-azidostyry1)- 5,5-dimethyl- 2-cyclohexen-1-one in the bottom layer. Resists with varying spectral responses from mid-UV to g-line can be designed by selecting the kind of diazo compound used in the top layer.

A graphene-based electrochemical competitive immunosensor for the sensitive detection of okadaic acid in shellfish

NASA Astrophysics Data System (ADS)

Eissa, Shimaa; Zourob, Mohammed

2012-11-01

A novel graphene-based voltammetric immunosensor for sensitive detection of okadaic acid (OA) was developed. A simple and efficient electrografting method was utilized to functionalize graphene-modified screen-printed carbon electrodes (GSPE) by the electrochemical reduction of in situ generated 4-carboxyphenyl diazonium salt in acidic aqueous solution. Next, the okadaic acid antibody was covalently immobilized on the carboxyphenyl modified graphene electrodes via carbodiimide chemistry. Square wave voltammetry (SWV) was used to investigate the stepwise assembly of the immunosensor. A competitive assay between OA and a fixed concentration of okadaic acid-ovalbumin conjugate (OA-OVA) for the immobilized antibodies was employed for the detection of okadaic acid. The decrease of the [Fe(CN)6]3-/4- reduction peak current in the square wave voltammetry for various concentrations of okadaic acid was used for establishing the calibration curve. A linear relationship between the SWV peak current difference and OA concentration was obtained up to ~5000 ng L-1. The developed immunosensor allowed a detection limit of 19 ng L-1 of OA in PBS buffer. The matrix effect studied with spiked shellfish tissue extracts showed a good percentage of recovery and the method was also validated with certified reference mussel samples.A novel graphene-based voltammetric immunosensor for sensitive detection of okadaic acid (OA) was developed. A simple and efficient electrografting method was utilized to functionalize graphene-modified screen-printed carbon electrodes (GSPE) by the electrochemical reduction of in situ generated 4-carboxyphenyl diazonium salt in acidic aqueous solution. Next, the okadaic acid antibody was covalently immobilized on the carboxyphenyl modified graphene electrodes via carbodiimide chemistry. Square wave voltammetry (SWV) was used to investigate the stepwise assembly of the immunosensor. A competitive assay between OA and a fixed concentration of okadaic acid-ovalbumin conjugate (OA-OVA) for the immobilized antibodies was employed for the detection of okadaic acid. The decrease of the [Fe(CN)6]3-/4- reduction peak current in the square wave voltammetry for various concentrations of okadaic acid was used for establishing the calibration curve. A linear relationship between the SWV peak current difference and OA concentration was obtained up to ~5000 ng L-1. The developed immunosensor allowed a detection limit of 19 ng L-1 of OA in PBS buffer. The matrix effect studied with spiked shellfish tissue extracts showed a good percentage of recovery and the method was also validated with certified reference mussel samples. Electronic supplementary information (ESI) available. See DOI: 10.1039/c2nr32146g

Palladium-Catalyzed α-Arylation of Aryl Nitromethanes

PubMed Central

2015-01-01

Catalytic conditions for the α-arylation of aryl nitromethanes have been discovered using parallel microscale experimentation, despite two prior reports of the lack of reactivity of these aryl nitromethane precursors. The method efficiently provides a variety of substituted, isolable diaryl nitromethanes. In addition, it is possible to sequentially append two different aryl groups to nitromethane. Mild oxidation conditions were identified to afford the corresponding benzophenones via the Nef reaction, and reduction conditions were optimized to afford several diaryl methylamines. PMID:26584680

A new route to synthesize aryl acetates from carbonylation of aryl methyl ethers

PubMed Central

Yang, Youdi; Li, Shaopeng; Han, Buxing

2018-01-01

Ether bond activation is very interesting because the synthesis of many valuable compounds involves conversion of ethers. Moreover, C–O bond cleavage is also very important for the transformation of biomass, especially lignin, which abundantly contains ether bonds. Developing efficient methods to activate aromatic ether bonds has attracted much attention. However, this is a challenge because of the inertness of aryl ether bonds. We proposed a new route to activate aryl methyl ether bonds and synthesize aryl acetates by carbonylation of aryl methyl ethers. The reaction could proceed over RhCl3 in the presence of LiI and LiBF4, and moderate to high yields of aryl acetates could be obtained from transformation of various aryl methyl ethers with different substituents. It was found that LiBF4 could assist LiI to cleave aryl methyl ether bonds effectively. The reaction mechanism was proposed by a combination of experimental and theoretical studies. PMID:29795781

Rhodium Catalyzed Intramolecular C-H Insertion of α-Aryl-α-diazo Ketones

PubMed Central

Taber, Douglass F.; Tian, Weiwei

2011-01-01

Direct diazo transfer proceeds smoothly with α-aryl ketones. The derived α-aryl-α-diazo ketones cyclize efficiently with Rh catalysis to give the corresponding α-aryl cyclopentanones. PMID:17385917

Direct asymmetric aldol reaction of aryl ketones with aryl aldehydes catalyzed by chiral BINOL-derived zincate catalyst.

PubMed

Li, Hong; Da, Chao-Shan; Xiao, Yu-Hua; Li, Xiao; Su, Ya-Ning

2008-09-19

Direct asymmetric aldol reaction of aryl ketones with aryl aldehydes catalyzed by chiral metal complex is reported for the first time herein. Two novel semicrown chiral ligands 1a and 1b were synthesized from (S)- and (R)-BINOL, respectively, and then employed to catalyze the direct asymmetric aldol addition of aryl ketones to aryl aldehydes. Introduced with 2.0 equiv of diethylzinc, 1b had higher enantioselectivity than 1a. Up to 97% yield and up to 80% enantioselectivity were achieved.

Covalent modification of reduced graphene oxide by means of diazonium chemistry and use as a drug-delivery system.

PubMed

Wei, Guangcheng; Yan, Miaomiao; Dong, Renhao; Wang, Dong; Zhou, Xiangzhu; Chen, Jingfei; Hao, Jingcheng

2012-11-12

Under acidic conditions, reduced graphene oxide (rGO) was functionalized with p-aminobenzoic acid, which formed the diazonium ions through the diazotization with a wet-chemical method. Surfactants or stabilizers were not applied during the diazotization. After the functionalized rGO was treated through mild sonication in aqueous solution, these functionalized rGO sheets were less than two layers, which was determined by atomic force microscopy (AFM) imaging. The water solubility of functionalized rGO after the introduction of polyethyleneimine (PEI) was improved significantly; it was followed by covalent binding of folic acid (FA) molecules to the functionalized rGO to allow us to specifically target CBRH7919 cancer cells by using FA as a receptor. The loading and release behaviors of elsinochrome A (EA) and doxorubicin (DOX) on the functionalized rGO sheets were investigated. The EA loading ratio onto rGO-C(6)H(4)-CO-NH-PEI-NH-CO-FA (abbreviated rGO-PEI-FA, the weight ratio of drug loaded onto rGO-PEI-FA) was approximately 45.56 %, and that of DOX was approximately 28.62 %. It was interesting that the drug release from rGO-PEI-FA was pH- and salt-dependent. The results of cytotoxicity (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and flow cytometry (FCM) assays, as well as cell morphology observations) clearly showed that the concentration of rGO-PEI-FA as the drug-delivery composite should be less than 12.5 mg L(-1). The conjugation of DOX and rGO-PEI-FA can enhance the cancer-cell apoptosis effectively and can also push the cancer cells to the vulnerable G2 phase of the cell cycle, which is most sensitive and susceptible to damage by drugs or radiation. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ligand-Enabled meta-Selective C-H Arylation of Nosyl-Protected Phenethylamines, Benzylamines, and 2-Aryl Anilines.

PubMed

Ding, Qiuping; Ye, Shengqing; Cheng, Guolin; Wang, Peng; Farmer, Marcus E; Yu, Jin-Quan

2017-01-11

A Pd-catalyzed, meta-selective C-H arylation of nosyl-protected phenethylamines and benzylamines is disclosed using a combination of norbornene and pyridine-based ligands. Subjecting nosyl protected 2-aryl anilines to this protocol led to meta-C-H arylation at the remote aryl ring. A diverse range of aryl iodides are tolerated in this reaction, along with select heteroaryl iodides. Select aryl bromides bearing ortho-coordinating groups can also be utilized as effective coupling partners in this reaction. The use of pyridine ligands has allowed the palladium loading to be reduced to 2.5 mol %. Furthermore, a catalytic amount of 2-norbornene (20 mol %) to mediate this meta-C-H activation process is demonstrated for the first time. Utilization of a common protecting group as the directing group for meta-C-H activation of amines is an important feature of this reaction in terms of practical applications.

Mechanistic Studies on the Copper-Catalyzed N-Arylation of Amides

PubMed Central

Strieter, Eric R.; Bhayana, Brijesh; Buchwald, Stephen L.

2009-01-01

The copper-catalyzed N-arylation of amides, i.e., the Goldberg reaction, is an efficient method for the construction of products relevant to both industry and academic settings. Herein, we present mechanistic details concerning the catalytic and stoichiometric N-arylation of amides. In the context of the catalytic reaction, our findings reveal the importance of chelating diamine ligands in controlling the concentration of the active catalytic species. The consistency between the catalytic and stoichiometric results suggest that the activation of aryl halides occurs through a 1,2-diamine-ligated copper(I) amidate complex. Kinetic studies on the stoichiometric N-arylation of aryl iodides using 1,2-diamine ligated Cu(I) amidates also provide insights into the mechanism of aryl halide activation. PMID:19072233

CuI/L-proline-catalyzed coupling reactions of aryl halides with activated methylene compounds.

PubMed

Xie, Xiaoan; Cai, Guorong; Ma, Dawei

2005-10-13

[reaction: see text] The arylation of ethyl acetoacetate, ethyl benzoyl acetate, and diethyl malonate under the catalysis of CuI/L-proline in DMSO proceeds smoothly at 40-50 degrees C in the presence of Cs2CO3 to provide the 2-aryl-1,3-dicarbonyl compounds in good yields. Both aryl iodides and aryl bromides are compatible with these reaction conditions.

The Ketene-Surrogate Coupling: Catalytic Conversion of Aryl Iodides to Aryl Ketenes via Ynol Ethers**

PubMed Central

Zhang, Wenhan; Ready, Joseph M.

2014-01-01

tert-Butoxyacetylene is shown to undergo Sonogashira coupling with aryl iodides to yield aryl-substituted tert-butyl ynol ethers. These intermediates participate in a [1,5]-hydride shift, which results in the extrusion of isobutylene and the generation of aryl ketenes. The ketenes are trapped in situ with multiple nucleophiles or undergoelectrocyclic ring closure to yield hydroxynaphthalenes and quinolines. PMID:24975840

Transition-metal-catalyzed direct arylation of (hetero)arenes by C-H bond cleavage.

PubMed

Ackermann, Lutz; Vicente, Rubén; Kapdi, Anant R

2009-01-01

The area of transition-metal-catalyzed direct arylation through cleavage of C-H bonds has undergone rapid development in recent years, and is becoming an increasingly viable alternative to traditional cross-coupling reactions with organometallic reagents. In particular, palladium and ruthenium catalysts have been described that enable the direct arylation of (hetero)arenes with challenging coupling partners--including electrophilic aryl chlorides and tosylates as well as simple arenes in cross-dehydrogenative arylations. Furthermore, less expensive copper, iron, and nickel complexes were recently shown to be effective for economically attractive direct arylations.

NiXantphos: a deprotonatable ligand for room-temperature palladium-catalyzed cross-couplings of aryl chlorides.

PubMed

Zhang, Jiadi; Bellomo, Ana; Trongsiriwat, Nisalak; Jia, Tiezheng; Carroll, Patrick J; Dreher, Spencer D; Tudge, Matthew T; Yin, Haolin; Robinson, Jerome R; Schelter, Eric J; Walsh, Patrick J

2014-04-30

Although the past 15 years have witnessed the development of sterically bulky and electron-rich alkylphosphine ligands for palladium-catalyzed cross-couplings with aryl chlorides, examples of palladium catalysts based on either triarylphosphine or bidentate phosphine ligands for efficient room temperature cross-coupling reactions with unactivated aryl chlorides are rare. Herein we report a palladium catalyst based on NiXantphos, a deprotonatable chelating aryldiphosphine ligand, to oxidatively add unactivated aryl chlorides at room temperature. Surprisingly, comparison of an extensive array of ligands revealed that under the basic reaction conditions the resultant heterobimetallic Pd-NiXantphos catalyst system outperformed all the other mono- and bidentate ligands in a deprotonative cross-coupling process (DCCP) with aryl chlorides. The DCCP with aryl chlorides affords a variety of triarylmethane products, a class of compounds with various applications and interesting biological activity. Additionally, the DCCP exhibits remarkable chemoselectivity in the presence of aryl chloride substrates bearing heteroaryl groups and sensitive functional groups that are known to undergo 1,2-addition, aldol reaction, and O-, N-, enolate-α-, and C(sp(2))-H arylations. The advantages and importance of the Pd-NiXantphos catalyst system outlined herein make it a valuable contribution for applications in Pd-catalyzed arylation reactions with aryl chlorides.

NiXantphos: A Deprotonatable Ligand for Room-Temperature Palladium-Catalyzed Cross-Couplings of Aryl Chlorides

PubMed Central

2015-01-01

Although the past 15 years have witnessed the development of sterically bulky and electron-rich alkylphosphine ligands for palladium-catalyzed cross-couplings with aryl chlorides, examples of palladium catalysts based on either triarylphosphine or bidentate phosphine ligands for efficient room temperature cross-coupling reactions with unactivated aryl chlorides are rare. Herein we report a palladium catalyst based on NiXantphos, a deprotonatable chelating aryldiphosphine ligand, to oxidatively add unactivated aryl chlorides at room temperature. Surprisingly, comparison of an extensive array of ligands revealed that under the basic reaction conditions the resultant heterobimetallic Pd–NiXantphos catalyst system outperformed all the other mono- and bidentate ligands in a deprotonative cross-coupling process (DCCP) with aryl chlorides. The DCCP with aryl chlorides affords a variety of triarylmethane products, a class of compounds with various applications and interesting biological activity. Additionally, the DCCP exhibits remarkable chemoselectivity in the presence of aryl chloride substrates bearing heteroaryl groups and sensitive functional groups that are known to undergo 1,2-addition, aldol reaction, and O-, N-, enolate-α-, and C(sp2)–H arylations. The advantages and importance of the Pd–NiXantphos catalyst system outlined herein make it a valuable contribution for applications in Pd-catalyzed arylation reactions with aryl chlorides. PMID:24745758

Facile N-Arylation of Amines and Sulfonamides and O-Arylation of Phenols and Arenecarboxylic Acids

PubMed Central

Liu, Zhijian; Larock, Richard C.

2008-01-01

An efficient, transition-metal free procedure for the N-arylation of amines, sulfonamides and carbamates and O-arylation of phenols and carboxylic acids has been achieved by allowing these substrates to react with a variety of o-silylaryl triflates in the presence of CsF. Good to excellent yields of arylated products are obtained under very mild reaction conditions. This chemistry readily tolerates a variety of functional groups. PMID:16599619

Diisopropylfluorophosphate-sensitive aryl acylamidase activity of fatty acid free human serum albumin.

PubMed

Manoharan, Indumathi; Boopathy, Rathnam

2006-08-15

Butyrylcholinesterase in human plasma and acetylcholinesterase in human red blood cells have aryl acylamidase activity toward o-nitroacetanilide, hydrolyzing the amide bond to produce o-nitroaniline and acetate. People with a genetic variant of butyrylcholinesterase that had no detectable activity with butyrylthiocholine, nevertheless had aryl acylamidase activity in their plasma. To determine the source of this aryl acylamidase activity we tested fatty acid free human albumin for activity. We found that albumin had aryl acylacylamidase activity and that this activity was inhibited by diisopropylfluorophosphate. Since the esterase activity of albumin is also inhibited by diisopropylfluorophosphate, and since it is known that diisopropylfluorophosphate covalently binds to Tyr 411 of human albumin, we conclude that the active site for aryl acylamidase activity of albumin is Tyr 411. Albumin accounts for about 10% of the aryl acylamidase activity in human plasma.

Ultrafast endothermic transfer of non-radiative exciplex state to radiative excitons in polyfluorene random copolymer for blue electroluminescence

NASA Astrophysics Data System (ADS)

Moghe, Dhanashree A.; Dey, Amrita; Johnson, Kerr; Lu, L.-P.; Friend, Richard H.; Kabra, Dinesh

2018-04-01

We report a blue-emitting random copolymer (termed modified Aryl-F8) consisting of three repeat units of polydioctylfluorene (F8), Aryl-polydioctylfluorene (Aryl-F8), and an aromatic amine comonomer unit, poly(bis-N,Ν'-(4-butylphenyl)-bis-N,N'-phenyl-1,4 phenylenediamine) chemically linked to get an improved charge carrier balance without compromising on the photoluminescence (PL) quantum yield with respect to the Aryl-F8 homo-polymer. The measured photoluminescence quantum efficiency (˜70%) of the blue-emitting polymer is comparable to or greater than the individual monomer units. The time resolved PL spectra from the modified Aryl-F8 are similar to those of Arylated-poly(9,9'-dioctylfluorene-co-bis-N,N'-(4-butylphenyl)-bis-N,N'-phenyl-1,4 phenylenediamine) (PFB) even at a time scale of 100-250 ps, indicating an ultrafast energy transfer from the (Aryl-F8 or F8):Arylated-PFB interface to Arylated-PFB, i.e., endothermic transfer of non-radiative exciplex to a radiative molecular exciton. Furthermore, the presence of non-radiative exciplex is confirmed by the photoluminescence decay profile and temperature dependent PL spectra. The luminance efficiency achieved for the modified Aryl-F8 polymer light-emitting diodes is ˜11 cd A-1 with an external quantum efficiency (EQE) of ˜4.5%, whereas it is 0.05 cd/A with an EQE of ˜0.025% for Aryl-F8. Almost two orders of higher efficiency is achieved due to the improved charge carrier balance from the random copolymer without compromising on the photoluminescence yield.

Palladium-Catalyzed Conversion of Aryl and Vinyl Triflates to Bromides and Chlorides

PubMed Central

Shen, Xiaoqiang; Hyde, Alan M.; Buchwald, Stephen L.

2010-01-01

The palladium-catalyzed conversion of aryl and vinyl triflates to aryl and vinyl halides (bromides and chlorides) has been developed using dialkylbiaryl phosphine ligands. A variety of aryl, heteroaryl and vinyl halides can be prepared via this method in good to excellent yields. PMID:20857936

Stabilities of nitrogen containing heterocyclic radicals and geometrical influences on non-radiative processes in organic molecules

NASA Technical Reports Server (NTRS)

Evleth, E. M.

1971-01-01

Theoretical and experimental work on generating radicals by removal of a hydrogen atom from pyrrole, imidazole, indole, and carbazole is reported. Photophysical studies on indolizine and related aza-derivatives show that materials having large S2-S1 energy gaps might exhibit upper state fluorescence. Photodecomposition quantum yields of a series of sterically hindered p-aminobenzene diazonium cations in water were found structurally and wavelength dependent and unquenched in aqueous sodium bromide solutions. Photodecomposition of diazonium materials did not produce a metastable species with a longer lifetime than 1 msec.

Ex situ generation of stoichiometric HCN and its application in the Pd-catalysed cyanation of aryl bromides: evidence for a transmetallation step between two oxidative addition Pd-complexes.

PubMed

Kristensen, Steffan K; Eikeland, Espen Z; Taarning, Esben; Lindhardt, Anders T; Skrydstrup, Troels

2017-12-01

A protocol for the Pd-catalysed cyanation of aryl bromides using near stoichiometric and gaseous hydrogen cyanide is reported for the first time. A two-chamber reactor was adopted for the safe liberation of ex situ generated HCN in a closed environment, which proved highly efficient in the Ni-catalysed hydrocyanation as the test reaction. Subsequently, this setup was exploited for converting a range of aryl and heteroaryl bromides (28 examples) directly into the corresponding benzonitriles in high yields, without the need for cyanide salts. Cyanation was achieved employing the Pd(0) precatalyst, P( t Bu) 3 -Pd-G3 and a weak base, potassium acetate, in a dioxane-water solvent mixture. The methodology was also suitable for the synthesis of 13 C-labelled benzonitriles with ex situ generated 13 C-hydrogen cyanide. Stoichiometric studies with the metal complexes were undertaken to delineate the mechanism for this catalytic transformation. Treatment of Pd(P( t Bu) 3 ) 2 with H 13 CN in THF provided two Pd-hydride complexes, (P( t Bu) 3 ) 2 Pd(H)( 13 CN), and [(P( t Bu) 3 )Pd(H)] 2 Pd( 13 CN) 4 , both of which were isolated and characterised by NMR spectroscopy and X-ray crystal structure analysis. When the same reaction was performed in a THF : water mixture in the presence of KOAc, only (P( t Bu) 3 ) 2 Pd(H)( 13 CN) was formed. Subjection of this cyano hydride metal complex with the oxidative addition complex (P( t Bu) 3 )Pd(Ph)(Br) in a 1 : 1 ratio in THF led to a transmetallation step with the formation of (P( t Bu) 3 ) 2 Pd(H)(Br) and 13 C-benzonitrile from a reductive elimination step. These experiments suggest the possibility of a catalytic cycle involving initially the formation of two Pd(ii)-species from the oxidative addition of L n Pd(0) into HCN and an aryl bromide followed by a transmetallation step to L n Pd(Ar)(CN) and L n Pd(H)(Br), which both reductively eliminate, the latter in the presence of KOAc, to generate the benzonitrile and L n Pd(0).

Generation and reactivity of ketyl radicals with lignin related structures. On the importance of the ketyl pathway in the photoyellowing of lignin containing pulps and papers.

PubMed

Fabbri, Claudia; Bietti, Massimo; Lanzalunga, Osvaldo

2005-04-01

[reaction: see text] Ketyl radicals with lignin related structures have been generated by means of radiation chemical and photochemical techniques. In the former studies ketyl radicals are produced by reaction of alpha-carbonyl-beta-aryl ether lignin models with the solvated electron produced by pulse radiolysis of an aqueous solution at pH 6.0. The UV-vis spectra of ketyl radicals are characterized by three main absorption bands. The shape and position of these bands slightly change when the spectra are recorded in alkaline solution (pH 11.0) being now assigned to the ketyl radical anions and a pKa = 9.5 is determined for the 1-(3,4,5-trimethoxyphenyl)-2-phenoxyethanol-1-yl radical. Decay rates of ketyl radicals are found to be dose dependent and, at low doses, lie in the range (1.7-2.7) x 10(3) s(-1). In the presence of oxygen a fast decay of the ketyl radicals is observed (k2 = 1.8-2.7 x 10(9) M(-1) s(-1)) that is accompanied by the formation of stable products, i.e., the starting ketones. In the photochemical studies ketyl radicals have been produced by charge-transfer (CT) photoactivation of the electron donor-acceptor salts of methyl viologen (MV2+) with alpha-hydroxy-alpha-phenoxymethyl-aryl acetates. This process leads to the instantaneous formation of the reduced acceptor (methyl viologen radical cation, MV+*), as is clearly shown in a laser flash photolysis experiment by the two absorption bands centered at 390 and 605 nm, and an acyloxyl radical [ArC(CO2*))(OH)CH2(OC6H5)], which undergoes a very fast decarboxylation with formation of the ketyl radicals. Steady-state photoirradiation of the CT ion pairs indicates that 1-aryl-2-phenoxyethanones are formed as primary photoproducts by oxidation of ketyl radicals by MV2+ (under argon) or by molecular oxygen. Small amounts of acetophenones are formed by further photolysis of 1-aryl-2-phenoxyethanones and not by beta-fragmentation of the ketyl radicals. The high reactivity of ketyl radicals with oxygen coupled with the low rates of beta-fragmentation of the same species have an important bearing in the context of the photoyellowing of lignin containing pulps and papers.

2-Aryl-2-nitroacetates as Central Precursors to Aryl Nitromethanes, α-Ketoesters, and α-Amino Acids

PubMed Central

Metz, Alison E.

2013-01-01

Nitroarylacetates are useful small molecular building blocks that act as precursors to α-ketoesters and aryl nitromethanes as well as α-amino acids. Methods were developed that produce each of these compound types in good yields. Two different conditions for decarboxylation are discussed for substrates with neutral and electron-poor aryl groups versus electron-rich aryl groups. For formation of the α-ketoesters, new mild conditions for the Nef disproportionation were identified. PMID:23245626

Construction of 1-Heteroaryl-3-azabicyclo[3.1.0]hexanes by sp3-sp2 Suzuki-Miyaura and Chan-Evans-Lam Coupling Reactions of Tertiary Trifluoroborates.

PubMed

Harris, Michael R; Li, Qifang; Lian, Yajing; Xiao, Jun; Londregan, Allyn T

2017-05-05

Compounds that contain the 1-heteroaryl-3-azabicyclo[3.1.0]hexane architecture are of particular interest to the pharmaceutical industry yet remain a challenge to synthesize. We report herein an expedient and modular approach to the synthesis of 1-heteroaryl-3-azabicyclo[3.1.0]hexanes by Suzuki-Miyaura and Chan-Evans-Lam coupling reactions of tertiary trifluoroborate salts. Our Suzuki-Miyaura cross-coupling protocol is compatible with a broad range of aryl and heteroaryl bromides and chlorides. The unprecedented Chan-Evans-Lam coupling of tertiary trifluoroborates allows the facile construction of 1-heteroaryl-3-azabicyclo[3.1.0]hexanes containing C-tertiary arylamines at the ring juncture.

Pseudoephedrine-Directed Asymmetric α-Arylation of α-Amino Acid Derivatives.

PubMed

Atkinson, Rachel C; Fernández-Nieto, Fernando; Mas Roselló, Josep; Clayden, Jonathan

2015-07-27

Available α-amino acids undergo arylation at their α position in an enantioselective manner on treatment with base of N'-aryl urea derivatives ligated to pseudoephedrine as a chiral auxiliary. In situ silylation and enolization induces diastereoselective migration of the N'-aryl group to the α position of the amino acid, followed by ring closure to a hydantoin with concomitant explulsion of the recyclable auxiliary. The hydrolysis of the hydantoin products provides derivatives of quaternary amino acids. The arylation avoids the use of heavy-metal additives, and is successful with a range of amino acids and with aryl rings of varying electronic character. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Organocatalytic asymmetric arylation of indoles enabled by azo groups

NASA Astrophysics Data System (ADS)

Qi, Liang-Wen; Mao, Jian-Hui; Zhang, Jian; Tan, Bin

2018-01-01

Arylation is a fundamental reaction that can be mostly fulfilled by electrophilic aromatic substitution and transition-metal-catalysed aryl functionalization. Although the azo group has been used as a directing group for many transformations via transition-metal-catalysed aryl carbon-hydrogen (C-H) bond activation, there remain significant unmet challenges in organocatalytic arylation. Here, we show that the azo group can effectively act as both a directing and activating group for organocatalytic asymmetric arylation of indoles via formal nucleophilic aromatic substitution of azobenzene derivatives. Thus, a wide range of axially chiral arylindoles have been achieved in good yields with excellent enantioselectivities by utilizing chiral phosphoric acid as catalyst. Furthermore, highly enantioenriched pyrroloindoles bearing two contiguous quaternary chiral centres have also been obtained via a cascade enantioselective formal nucleophilic aromatic substitution-cyclization process. This strategy should be useful in other related research fields and will open new avenues for organocatalytic asymmetric aryl functionalization.

Organocatalytic asymmetric arylation of indoles enabled by azo groups.

PubMed

Qi, Liang-Wen; Mao, Jian-Hui; Zhang, Jian; Tan, Bin

2018-01-01

Arylation is a fundamental reaction that can be mostly fulfilled by electrophilic aromatic substitution and transition-metal-catalysed aryl functionalization. Although the azo group has been used as a directing group for many transformations via transition-metal-catalysed aryl carbon-hydrogen (C-H) bond activation, there remain significant unmet challenges in organocatalytic arylation. Here, we show that the azo group can effectively act as both a directing and activating group for organocatalytic asymmetric arylation of indoles via formal nucleophilic aromatic substitution of azobenzene derivatives. Thus, a wide range of axially chiral arylindoles have been achieved in good yields with excellent enantioselectivities by utilizing chiral phosphoric acid as catalyst. Furthermore, highly enantioenriched pyrroloindoles bearing two contiguous quaternary chiral centres have also been obtained via a cascade enantioselective formal nucleophilic aromatic substitution-cyclization process. This strategy should be useful in other related research fields and will open new avenues for organocatalytic asymmetric aryl functionalization.

A photochemical approach for a fast and self-limited covalent modification of surface supported graphene with photoactive dyes

NASA Astrophysics Data System (ADS)

Sergeeva, Natalia N.; Chaika, Alexander N.; Walls, Brian; Murphy, Barry E.; Walshe, Killian; Martin, David P.; Richards, Billy D. O.; Jose, Gin; Fleischer, Karsten; Aristov, Victor Yu; Molodtsova, Olga V.; Shvets, Igor V.; Krasnikov, Sergey A.

2018-07-01

Herein, we report a simple method for a covalent modification of surface supported graphene with photoactive dyes. Graphene was fabricated on cubic-SiC/Si(001) wafers due to their low cost and suitability for mass-production of continuous graphene fit for electronic applications on millimetre scale. Functionalisation of the graphene surface was carried out in solution via white light induced photochemical generation of phenazine radicals from phenazine diazonium salt. The resulting covalently bonded phenazine-graphene hybrid structure was characterised by scanning tunnelling microscopy (STM) and spectroscopy (STS), Raman spectroscopy and density functional theory (DFT) calculations. It was found that phenazine molecules form an overlayer, which exhibit a short range order with a rectangular unit cell on the graphene surface. DFT calculations based on STM results reveal that molecules are standing up in the overlayer with the maximum coverage of 0.25 molecules per graphene unit cell. Raman spectroscopy and STM results show that the growth is limited to one monolayer of standing molecules. STS reveals that the phenazine-graphene hybrid structure has a band gap of 0.8 eV.

Enzyme-less electrochemical displacement heterogeneous immunosensor for diclofenac detection.

PubMed

Nguyen, T T K; Vu, T T; Anquetin, G; Tran, H V; Reisberg, S; Noël, V; Mattana, G; Nguyen, Q V; Dai Lam, Tran; Pham, M C; Piro, B

2017-11-15

We describe an electrochemical immunosensor based on functionalization of a working electrode by electrografting two functional diazonium salts. The first one is a molecular probe, diclofenac, coupled with an arylamine onto which a specific antibody is immobilized by affinity interactions; the second is a redox probe (a quinone) also coupled with an arylamine, able to transduce the hapten-antibody association into a change in electroactivity. The steric hindrance induced by the antibody leads to a current decrease upon binding of the antibody on the grafted molecular probe; conversely, when diclofenac is present in solution, a displacement equilibrium occurs between the target diffusing into the solution and the grafted probe. This leads to dissociation of the antibody from the electrode surface, event which is transduced into a current increase ("signal-on" detection). The detection limit is ca. 20 fM, corresponding to 6pgL -1 diclofenac, which is competitive compared to other label-free immunosensors. We demonstrate that the sensor is selective and is able to quantify diclofenac in tap water. Copyright © 2017 Elsevier B.V. All rights reserved.

Benzene carboxylic acid derivatized graphene oxide nanosheets on natural zeolites as effective adsorbents for cationic dye removal.

PubMed

Yu, Yang; Murthy, Bandaru N; Shapter, Joseph G; Constantopoulos, Kristina T; Voelcker, Nicolas H; Ellis, Amanda V

2013-09-15

Graphene oxide (GO) nanosheets were grafted to acid-treated natural clinoptilolite-rich zeolite powders followed by a coupling reaction with a diazonium salt (4-carboxybenzenediazoniumtetrafluoroborate) to the GO surface. Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and thermogravimetric analysis (TGA) revealed successful grafting of GO nanosheets onto the zeolite surface. The application of the adsorbents for the adsorption of rhodamine B from aqueous solutions was then demonstrated. After reaching adsorption equilibrium the maximum adsorption capacities were shown to be 50.25, 55.56 and 67.56 mg g(-1) for pristine natural zeolite, GO grafted zeolite (GO-zeolite) and benzene carboxylic acid derivatized GO-zeolite powders, respectively. The adsorption behavior was fitted to a Langmuir isotherm and shown to follow a pseudo-second-order reaction model. Further, a relationship between surface functional groups, pH and adsorption efficiency was established. Results indicate that benzene carboxylic acid derivatized GO-zeolite powders are environmentally favorable adsorbents for the removal of cationic dyes from aqueous solutions. Copyright © 2013 Elsevier B.V. All rights reserved.

A Novel Preparation Method of Two Polymer Dyes with Low Cytotoxicity

PubMed Central

Lv, Dongjun; Zhang, Mingjie; Cui, Jin; Li, Weixue; Zhu, Guohua

2017-01-01

A new preparation method of polymer dyes was developed to improve both the grafting degree of the azo dyes onto O-carboxymethyl chitosan (OMCS) and the water solubility of prepared polymer dyes. Firstly, the coupling compound of two azo edible colorants, sunset yellow (SY) and allura red (AR), was grafted onto OMCS, and then coupled with their diazonium salt. The chemical structure of prepared polymer dyes was determined by Fourier transform-infrared spectroscopy and 1H-NMR, and the results showed that the two azo dyes were successfully grafted onto OMCS. The grafting degree onto OMCS and the water solubility of polymer dyes were tested, and the results showed that they were both improved as expected. The UV-vis spectra analysis results showed that the prepared polymer dyes showed similar color performance with the original azo dyes. Eventually, the cytotoxicity of prepared polymer dyes was tested and compared with the original azo dyes by a cytotoxicity test on human liver cell lines LO2, and the results showed that their grafting onto OMCS significantly reduced the cytotoxicity. PMID:28772583

Molecular adsorption on graphene

NASA Astrophysics Data System (ADS)

Kong, Lingmei; Enders, Axel; Rahman, Talat S.; Dowben, Peter A.

2014-11-01

Current studies addressing the engineering of charge carrier concentration and the electronic band gap in epitaxial graphene using molecular adsorbates are reviewed. The focus here is on interactions between the graphene surface and the adsorbed molecules, including small gas molecules (H2O, H2, O2, CO, NO2, NO, and NH3), aromatic, and non-aromatic molecules (F4-TCNQ, PTCDA, TPA, Na-NH2, An-CH3, An-Br, Poly (ethylene imine) (PEI), and diazonium salts), and various biomolecules such as peptides, DNA fragments, and other derivatives. This is followed by a discussion on graphene-based gas sensor concepts. In reviewing the studies of the effects of molecular adsorption on graphene, it is evident that the strong manipulation of graphene’s electronic structure, including p- and n-doping, is not only possible with molecular adsorbates, but that this approach appears to be superior compared to these exploiting edge effects, local defects, or strain. However, graphene-based gas sensors, albeit feasible because huge adsorbate-induced variations in the relative conductivity are possible, generally suffer from the lack of chemical selectivity.

40 CFR 721.6220 - Aryl sulfonate of a fatty acid mixture, polyamine condensate.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Aryl sulfonate of a fatty acid mixture... Specific Chemical Substances § 721.6220 Aryl sulfonate of a fatty acid mixture, polyamine condensate. (a... generically as an aryl sulfonate of a fatty acid mixture, polyamine condensate (PMN P-91-584) is subject to...

40 CFR 721.6220 - Aryl sulfonate of a fatty acid mixture, polyamine condensate.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Aryl sulfonate of a fatty acid mixture... Specific Chemical Substances § 721.6220 Aryl sulfonate of a fatty acid mixture, polyamine condensate. (a... generically as an aryl sulfonate of a fatty acid mixture, polyamine condensate (PMN P-91-584) is subject to...

Regioselective copper-catalyzed N(1)-(hetero)arylation of protected histidine.

PubMed

Sharma, Krishna K; Mandloi, Meenakshi; Jain, Rahul

2016-09-26

We report regioselective N(1)-arylation of protected histidine using copper(i) iodide as a catalyst, trans-N,N'-dimethylcyclohexane-1,2-diamine as a ligand and readily available aryl iodides as coupling partners under microwave irradiation at 130 °C for 40 min. The reaction provides rapid access to electron-donating, electron-withdrawing and bulky group substituted N-arylated histidines in high yields, including previously inaccessible N-heteroaryl histidines. These N(1)-(hetero)aryl histidines are promising building blocks in peptide-based drug design and discovery.

β-Selective C-H arylation of pyrroles leading to concise syntheses of lamellarins C and I.

PubMed

Ueda, Kirika; Amaike, Kazuma; Maceiczyk, Richard M; Itami, Kenichiro; Yamaguchi, Junichiro

2014-09-24

The first general β-selective C-H arylation of pyrroles has been developed by using a rhodium catalyst. This C-H arylation reaction, which is retrosynthetically straightforward but results in unusual regioselectivity, could result in de novo syntheses of pyrrole-derived natural products and pharmaceuticals. As such, we have successfully synthesized polycyclic marine pyrrole alkaloids, lamellarins C and I, by using this β-selective arylation of pyrroles with aryl iodides (C-H/C-I coupling) and a new double C-H/C-H coupling as key steps.

Versatile Alkylation of (Hetero)Aryl Iodides with Ketones via β-C(sp3)-H Activation.

PubMed

Zhu, Ru-Yi; Liu, Luo-Yan; Park, Han Seul; Hong, Kai; Wu, Yongwei; Senanayake, Chris H; Yu, Jin-Quan

2017-11-15

We report Pd(II)-catalyzed β-C(sp 3 )-H (hetero)arylation of a variety of ketones using a commercially available 2,2-dimethyl aminooxyacetic acid auxiliary. Facile installation and removal of the auxiliary as well as its superior scope for both ketones and (hetero)aryl iodides overcome the significant limitations of the previously reported β-C(sp 3 )-H arylation of ketones. The ready availability of ketones renders this reaction a broadly useful method for alkyl-(hetero)aryl coupling involving both primary and secondary alkyls.

Metabolism and disposition of oral dabrafenib in cancer patients: proposed participation of aryl nitrogen in carbon-carbon bond cleavage via decarboxylation following enzymatic oxidation.

PubMed

Bershas, David A; Ouellet, Daniele; Mamaril-Fishman, Donna B; Nebot, Noelia; Carson, Stanley W; Blackman, Samuel C; Morrison, Royce A; Adams, Jerry L; Jurusik, Kristen E; Knecht, Dana M; Gorycki, Peter D; Richards-Peterson, Lauren E

2013-12-01

A phase I study was conducted to assess the metabolism and excretion of [(14)C]dabrafenib (GSK2118436; N-{3-[5-(2-amino-4-pyrimidinyl)-2-(1,1-dimethylethyl)-1,3-thiazol-4-yl]-2-fluorophenyl}-2,6-difluorobenzene sulfonamide, methanesulfonate salt), a BRAF inhibitor, in four patients with BRAF V600 mutation-positive tumors after a single oral dose of 95 mg (80 µCi). Assessments included the following: 1) plasma concentrations of dabrafenib and metabolites using validated ultra-high-performance liquid chromatography--tandem mass spectrometry methods, 2) plasma and blood radioactivity, 3) urinary and fecal radioactivity, and 4) metabolite profiling. Results showed the mean total recovery of radioactivity was 93.8%, with the majority recovered in feces (71.1% of administered dose). Urinary excretion accounted for 22.7% of the dose, with no detection of parent drug in urine. Dabrafenib is metabolized primarily via oxidation of the t-butyl group to form hydroxy-dabrafenib. Hydroxy-dabrafenib undergoes further oxidation to carboxy-dabrafenib, which subsequently converts to desmethyl-dabrafenib via a pH-dependent decarboxylation. The half-lives for carboxy- and desmethyl-dabrafenib were longer than for parent and hydroxy-dabrafenib (18-20 vs. 5-6 hours). Based on area under the plasma concentration-time curve, dabrafenib, hydroxy-, carboxy-, and desmethyl-dabrafenib accounted for 11%, 8%, 54%, and 3% of the plasma radioactivity, respectively. These results demonstrate that the major route of elimination of dabrafenib is via oxidative metabolism (48% of the dose) and biliary excretion. Based on our understanding of the decarboxylation of carboxy-dabrafenib, a low pH-driven, nonenzymatic mechanism involving participation of the aryl nitrogen is proposed to allow prediction of metabolic oxidation and decarboxylation of drugs containing an aryl nitrogen positioned α to an alkyl (ethyl or t-butyl) side chain.

FV-100: the most potent and selective anti-varicella zoster virus agent reported to date.

PubMed

Migliore, Marco

2010-01-05

Bicyclic aryl furano pyrimidines represent the most potent anti-varicella zoster virus (VZV) agents reported to date. Lead compounds have 50% effective concentration (EC(50)) values in vitro that are in the subnanomolar range and selectivity index values that exceed 1 million. They have an absolute requirement for VZV thymidine kinase and most likely act as their phosphate forms. Some structural modification (such as aryl substitution in the base moiety) is tolerated, whereas little sugar modification is acceptable. The Cf1743 compound has proved to be significantly more potent than all reference anti-VZV compounds, as measured either by inhibition of infectious virus particles and/or viral DNA production; however, the high lipophilicity and very low water solubility of this compound gives poor oral bioavailability (<14%). Use of the modified cyclodextrin captisol and the synthesis of the 5'-monophosphate prodrug of Cf1743 has significantly improved water solubility, but does not give any enhancement in oral bioavailability. By contrast, the synthesis of the ether series does not give any further improvement in terms of solubility. The most promising prodrug to emerge to date is the hydrochloric salt of the 5'-valyl-ester, designated as FV-100. Its uptake into cells has been studied using fluorescent microscopy and biological assays, which have indicated that the compound is efficiently taken up by the cells after a short period of incubation.

Chemoselective N-arylation of aminobenzamides via copper catalysed Chan-Evans-Lam reactions.

PubMed

Liu, Shuai; Zu, Weisai; Zhang, Jinli; Xu, Liang

2017-11-15

Chemoselective N-arylation of unprotected aminobenzamides was achieved via Cu-catalysed Chan-Evans-Lam cross-coupling with aryl boronic acids for the first time. Simple copper catalysts enable the selective arylation of amino groups in ortho/meta/para-aminobenzamides under open-flask conditions. The reactions were scalable and compatible with a wide range of functional groups.

Functionalized polyfluorenes for use in optoelectronic devices

DOEpatents

Chichak, Kelly Scott [Clifton Park, NY; Lewis, Larry Neil [Scotia, NY; Cella, James Anthony [Clifton Park, NY; Shiang, Joseph John [Niskayuna, NY

2011-11-08

The present invention relates to process comprising reacting a polyfluorenes comprising at least one structural group of formula I ##STR00001## with an iridium (III) compound of formula II ##STR00002## wherein R.sup.1 and R.sup.2 are independently alkyl, substituted alkyl, aryl, substituted aryl or a combination thereof; R.sup.5is H or CHO; R.sup.3 and R.sup.4 are independently hydrogen, alkyl, substituted alkyl, aryl, substituted aryl or a combination thereof; R.sup.11 and R.sup.12 taken together form a substituted or unsubstituted monocyclic or bicyclic heteroaromatic ring; R.sup.13 is independently at each occurrence halo, nitro, hydroxy, amino, alkyl, aryl, arylalkyl, alkoxy, substituted alkoxy, substituted alkyl, substituted aryl, or substituted arylalkyl; Ar is aryl, heteroaryl, substituted aryl, substituted heteroaryl, or a combination thereof; X is selected from a direct bond, alky, substituted alkyl, and combinations thereof; Y is CHO or NH.sub.2; Z is CHO or NH.sub.2 where Z does not equal Y; and p is 0, 1 or 2. The invention also relates to the polyfluorenes, which are products of the reaction, and the use of the polyfluorenes in optoelectronic devices.

Electronic states of aryl radical functionalized graphenes: Density functional theory study

NASA Astrophysics Data System (ADS)

Tachikawa, Hiroto; Kawabata, Hiroshi

2016-06-01

Functionalized graphenes are known as a high-performance molecular device. In the present study, the structures and electronic states of the aryl radical functionalized graphene have been investigated by the density functional theory (DFT) method to elucidate the effects of functionalization on the electronic states of graphene (GR). Also, the mechanism of aryl radical reaction with GR was investigated. The benzene, biphenyl, p-terphenyl, and p-quaterphenyl radicals [denoted by (Bz) n (n = 1-4), where n means numbers of benzene rings in aryl radical] were examined as aryl radicals. The DFT calculation of GR-(Bz) n (n = 1-4) showed that the aryl radical binds to the carbon atom of GR, and a C-C single bond was formed. The binding energies of aryl radicals to GR were calculated to be ca. 6.0 kcal mol-1 at the CAM-B3LYP/6-311G(d,p) level. It was found that the activation barrier exists in the aryl radical addition: the barrier heights were calculated to be 10.0 kcal mol-1. The electronic states of GR-(Bz) n were examined on the basis of theoretical results.

Enhanced Electro-Static Modulation of Ionic Diffusion through Carbon Nanotube Membranes by Diazonium Grafting Chemistry

PubMed Central

Majumder, Mainak; Keis, Karin; Zhan, Xin; Meadows, Corey; Cole, Jeggan

2013-01-01

A membrane structure consisting of an aligned array of open ended carbon nanotubes (~ 7 nm i.d.) spanning across an inert polymer matrix allows the diffusive transport of aqueous ionic species through CNT cores. The plasma oxidation process that opens CNTs tips inherently introduces carboxylic acid groups at the CNT tips, which allows for a limited amount of chemical functional at the CNT pore entrance. However for numerous applications, it is important to increase the density of carboxylic acid groups at the pore entrance for effective separation processes. Aqueous diazonium based electro-chemistry significantly increases the functional density of carboxylic acid groups. pH dependent dye adsorption-desorption and interfacial capacitance measurements indicate ~ 5–6 times increase in functional density. To further control the spatial location of the functional chemistry, a fast flowing inert liquid column inside the CNT core is found to restrict the diazonium grafting to the CNT tips only. This is confirmed by the increased flux of positively charged Ru(bi-py)3+2 with anionic functionality. The electrostatic enhancement of ion diffusion is readily screened in 0.1(M) electrolyte solution consistent with the membrane pore geometry and increased functional density. PMID:25132719

Stereospecific Palladium-Catalyzed C-H Arylation of Pyroglutamic Acid Derivatives at the C3 Position Enabled by 8-Aminoquinoline as a Directing Group.

PubMed

Verho, Oscar; Maetani, Micah; Melillo, Bruno; Zoller, Jochen; Schreiber, Stuart L

2017-09-01

An efficient and stereospecific Pd-catalyzed protocol for the C-H arylation of pyroglutamic acid derivatives that uses 8-aminoquinoline as a directing group is described. The reaction was shown to proceed efficiently with a variety of aryl and heteroaryl iodides bearing different functional groups, giving C3-arylated cis products in good to high yields. Removal of the 8-aminoquinoline unit from these C-H arylation products enables access to synthetically useful cis and trans pyroglutamic acid-based building blocks.

Aryl Ketone Synthesis via Tandem Orthoplatinated Triarylphosphite-Catalyzed Addition Reactions of Arylboronic Acids with Aldehydes Followed by Oxidation

PubMed Central

Liao, Yuan-Xi; Hu, Qiao-Sheng

2010-01-01

Tandem orthoplatinated triarylphosphite-catalyzed addition reactions of arylboronic acids with aldehydes followed by oxidation to yield aryl ketones is described. 3-Pentanone was identified as a suitable oxidant for the tandem aryl ketone formation reaction. By using microwave energy, aryl ketones were obtained in high yields with the catalyst loading as low as 0.01%. PMID:20849092

Chemical degradation mechanisms of membranes for alkaline membrane fuel cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Choe, Yoong-Kee; Henson, Neil J.; Kim, Yu Seung

2015-12-31

Chemical degradation mechanisms of membranes for alkaline membrane fuel cells have been investigated using density functional theory (DFT). We have elucidated that the aryl-ether moiety of membranes is one of the weakest site against attack of hydroxide ions. The results of DFT calculations for hydroxide initiated aryl-ether cleavage indicated that the aryl-ether cleavage occurred prior to degradation of cationic functional group. Such a weak nature of the aryl-ether group arises from the electron deficiency of the aryl group as well as the low bond dissociation energy. The DFT results suggests that removal of the aryl-ether group in the membrane shouldmore » enhance the stability of membranes under alkaline conditions. In fact, an ether fee poly(phenylene) membrane exhibits excellent stability against the attack from hydroxide ions.« less

An Efficient Process for Pd-Catalyzed C–N Cross-Coupling Reactions of Aryl Iodides: Insight Into Controlling Factors

PubMed Central

Fors, Brett P.; Davis, Nicole R.; Buchwald, Stephen L.

2009-01-01

An investigation into Pd-catalyzed C–N cross-coupling reactions of aryl iodides is described. NaI is shown to have a significant inhibitory effect on these processes. By switching to a solvent system in which the iodide byproduct was insoluble, reactions of aryl iodides were accomplished with the same efficiencies as aryl chlorides and bromides. Using catalyst systems based on certain biarylphosphine ligands, aryl iodides were successfully reacted with an array of primary and secondary amines in high yields. Lastly, reactions of heteroarylamines and heteroaryliodides were also conducted in high yields. PMID:19348431

Application of a Heterogeneous Chiral Titanium Catalyst Derived from Silica-Supported 3-Aryl H8-BINOL to Enantioselective Alkylation and Arylation of Aldehydes.

PubMed

Akai, Junichiro; Watanabe, Satoshi; Michikawa, Kumiko; Harada, Toshiro

2017-07-07

A 3-aryl H 8 -BINOL was grafted on the surface of silica gel using a hydrosilane derivative as a precursor, and the resulting silica-supported ligand (6 mol %) was employed in the enantioselective alkylation and arylation of aldehydes in the presence of Ti(O i Pr) 4 . The reactions using Et 2 Zn, Et 3 B, and aryl Grignard reagents all afforded the corresponding adducts in high enantioselectivities and yields. The silica-immobilized titanium catalyst could be reused up to 14 times without appreciable deterioration of the activity.

Metal and base free synthesis of primary amines via ipso amination of organoboronic acids mediated by [bis(trifluoroacetoxy)iodo]benzene (PIFA).

PubMed

Chatterjee, Nachiketa; Goswami, Avijit

2015-08-07

A metal and base free synthesis of primary amines has been developed at ambient temperature through ipso amination of diversely functionalized organoboronic acids, employing a combination of [bis(trifluoroacetoxy)iodo]benzene (PIFA)-N-bromosuccinimide (NBS) and methoxyamine hydrochloride as the aminating reagent. The amines were primarily obtained as their trifluoroacetate salts which on subsequent aqueous alkaline work up provided the corresponding free amines. The combination of PIFA-NBS is found to be the mildest choice compared to the commonly used strong bases (e.g. n-BuLi, Cs2CO3) for activating the aminating agent. The reaction is expected to proceed via activation of the aminating reagent followed by B-N 1,2-aryl migration.

Method for removing elemental sulfur in sour gas wells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sample, T.E. Jr.

1975-09-30

A process is described for removing sulfur deposits from sour gas wells. The formation, well, and surface equipment are contacted with a chemical composition whose aqueous solution will solubilize the sulfur by primary chemical reaction and contains a wetting agent to facilitate and accelerate the sulfur dissolution and removal. The wetting agent or surfactant may be any of a wide variety of surface-active substances such as soaps, sodium or ammonium salts of alkyl or alkyl-aryl sulfates and sulfonates. Nonionic surfactants are preferred, such as ethoxylated substituted phenols. The aqueous solvents are capable of chemically reacting with sulfur to form water-solublemore » sulfur derivatives and include aqueous solutions of alkalies, bases (both inorganic and organic), ammonia, sulfites, bisulfites, etc. (6 claims)« less

Synthesis of Polyfunctional Diorganomagnesium and Diorganozinc Reagents through In Situ Trapping Halogen-Lithium Exchange of Highly Functionalized (Hetero)aryl Halides in Continuous Flow.

PubMed

Ketels, Marthe; Ganiek, Maximilian A; Weidmann, Niels; Knochel, Paul

2017-10-02

We report a halogen-lithium exchange performed in the presence of various metal salts (ZnCl 2 , MgCl 2 ⋅LiCl) on a broad range of sensitive bromo- or iodo(hetero)arenes using BuLi or PhLi as the exchange reagent and a commercially available continuous-flow setup. The resulting diarylmagnesium or diarylzinc species were trapped with various electrophiles, resulting in the formation of polyfunctional (hetero)arenes in high yields. This method enables the functionalization of (hetero)arenes containing highly sensitive groups such as an isothiocyanate, nitro, azide, or ester. A straightforward scale-up was possible without further optimization. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Aniline-modified porous graphitic carbon for hydrophilic interaction and attenuated reverse phase liquid chromatography.

PubMed

Iverson, Chad D; Lucy, Charles A

2014-12-19

Most stationary phases for hydrophilic interaction liquid chromatography (HILIC) and reversed phase liquid chromatography (RPLC) are based on silica. Porous graphitic carbon (PGC) is an attractive alternative to silica-based phases due to its chemical and thermal stability, and unique selectivity. However, native PGC is strongly hydrophobic and in some instances excessively retentive. PGC particles with covalently attached aniline groups (Dimethylaniline-PGC and Aniline-PGC) were synthesized to alter the surface polarity of PGC. First, the diazonium salt of N,N-dimethyl-p-phenylenediamine or 4-nitroaniline was adsorbed onto the PGC surface. The adsorbed salt was reduced with sodium borohydride and (Aniline-PGC only) the nitro group was further reduced with iron powder to the aniline. X-ray photoelectron spectroscopy confirmed the surface functionalities and that these moieties were introduced to the surface at concentrations of 0.9 and 2.1molecules/nm(2), respectively. These modified PGC phases (especially Aniline-PGC) were evaluated as HILIC and reversed phases. The Dimethylaniline-PGC phase displayed only weak HILIC retention of phenolic solutes. In contrast, the Aniline-PGC phase displayed up to nearly a 7-fold increase in HILIC retention vs. an aniline-silica phase and selectivity that differed from 10 other HILIC phases. Introduction of aniline groups to the PGC surface reduced the RPLC retentivity of PGC up to more than 5-fold and improved the separation efficiency up to 6-fold. The chromatographic performance of Aniline-PGC is demonstrated by separations of nucleotides, nucleosides, carboxylic acids, basic pharmaceuticals, and other compounds. Copyright © 2014 Elsevier B.V. All rights reserved.

Nickel-catalyzed synthesis of aryl trifluoromethyl sulfides at room temperature.

PubMed

Zhang, Cheng-Pan; Vicic, David A

2012-01-11

Inexpensive nickel-bipyridine complexes were found to be active for the trifluoromethylthiolation of aryl iodides and aryl bromides at room temperature using the convenient [NMe(4)][SCF(3)] reagent. © 2011 American Chemical Society

Synthesis of Secondary Aromatic Amides via Pd-Catalyzed Aminocarbonylation of Aryl Halides Using Carbamoylsilane as an Amide Source.

PubMed

Tong, Wenting; Cao, Pei; Liu, Yanhong; Chen, Jianxin

2017-11-03

Using N-methoxymethyl-N-organylcarbamoyl(trimethyl)silanes as secondary amides source, the direct transformation of aryl halides into the corresponding secondary aromatic amides via palladium-catalyzed aminocarbonylation is described. The reactions tolerated a broad range of functional groups on the aryl ring except big steric hindrance of substituent. The types and the relative position of substituents on the aryl ring impact the coupling efficiency.

Copper-catalyzed direct synthesis of diaryl 1,2-diketones from aryl iodides and propiolic acids.

PubMed

Min, Hongkeun; Palani, Thiruvengadam; Park, Kyungho; Hwang, Jinil; Lee, Sunwoo

2014-07-03

Benzil derivatives such as diaryl 1,2-diketones are synthesized via the direct decarboxylative coupling reaction of aryl propiolic acids and their oxidation. The optimized conditions are that the reaction of aryl propiolic acids and aryl iodides is conducted at 140 °C for 6 h in the presence of 10 mol % CuI/Cu(OTf)2 and Cs2CO3, after which HI (aq) is added and further reacted. The method shows good functional group tolerance toward ester, aldehyde, cyano, and nitro groups. In addition, symmetrical diaryl 1,2-diketones are obtained from aryl iodides and propiolic acid in the presence of palladium and copper catalysts.

Camphyl-based α-diimine palladium complexes: highly efficient precatalysts for direct arylation of thiazoles in open-air.

PubMed

Chen, Fu-Min; Lu, Dong-Dong; Hu, Li-Qun; Huang, Ju; Liu, Feng-Shou

2017-07-21

Based on the strategy of the development of phosphine-free palladium-catalyzed direct C-H arylation, a series of camphyl-based α-diimine palladium complexes bearing sterically bulky substituents were synthesized and characterized. The palladium complexes were applied for the cross-coupling of thiazole derivatives with aryl bromides. The effect of the sterically bulky substituent on the N-aryl moiety as well as the reaction conditions was screened. Under the optimal protocols, a wide range of aryl bromides can be smoothly coupled with thiazoles in good to excellent yields in the presence of a low palladium loading of 0.2 mol% under open-air conditions.

Palladium- and Copper-Catalyzed Arylation of Carbon-Hydrogen Bonds

PubMed Central

Daugulis, Olafs; Do, Hien-Quang; Shabashov, Dmitry

2010-01-01

The transition-metal-catalyzed functionalization of C-H bonds is a powerful method for generating carbon-carbon bonds. Although significant advances to this field have been reported during the last decade, many challenges remain. First, most of the methods are substrate-specific and thus cannot be generalized. Second, conversions of unactivated (i.e. not benzylic or alpha to heteroatom) sp3 C–H bonds to C–C bonds are rare, with most examples limited to t-butyl groups—a conversion that is inherently simple because there are no β-hydrogens that can be eliminated. Finally, the palladium, rhodium, and ruthenium catalysts routinely used for the conversion of C–H bonds to C–C bonds are expensive. Catalytically active metals that are cheaper and less exotic (e.g. copper, iron, and manganese) are rarely used. This Account describes our attempts to provide solutions to these three problems. We have developed a general method for directing-group-containing arene arylation by aryl iodides. Using palladium acetate as the catalyst, we arylated anilides, benzamides, benzoic acids, benzylamines, and 2-substituted pyridine derivatives under nearly identical conditions. We have also developed a method for the palladium-catalyzed auxiliary-assisted arylation of unactivated sp3 C–H bonds. This procedure allows for the β-arylation of carboxylic acid derivatives and the γ-arylation of amine derivatives. Furthermore, copper catalysis can be used to mediate the arylation of acidic arene C–H bonds (i.e. those with pKa values <35 in DMSO). Using a copper iodide catalyst in combination with a base and a phenanthroline ligand, we successfully arylated electron-rich and electron-deficient heterocycles and electron-poor arenes possessing at least two electron-withdrawing groups. The reaction exhibits unusual regioselectivity: arylation occurs at the most hindered position. This copper-catalyzed method supplements the well-known C–H activation/borylation methodology, in which functionalization usually occurs at the least hindered position. We also describe preliminary investigations to determine the mechanisms of these transformations. We anticipate that other transition metals, including iron, nickel, cobalt, and silver, will also be able to facilitate deprotonation/arylation reaction sequences. PMID:19552413

Palladium- and copper-catalyzed arylation of carbon-hydrogen bonds.

PubMed

Daugulis, Olafs; Do, Hien-Quang; Shabashov, Dmitry

2009-08-18

The transition-metal-catalyzed functionalization of C-H bonds is a powerful method for generating carbon-carbon bonds. Although significant advances to this field have been reported during the past decade, many challenges remain. First, most of the methods are substrate-specific and thus cannot be generalized. Second, conversions of unactivated (i.e., not benzylic or alpha to heteroatom) sp(3) C-H bonds to C-C bonds are rare, with most examples limited to t-butyl groups, a conversion that is inherently simple because there are no beta-hydrogens that can be eliminated. Finally, the palladium, rhodium, and ruthenium catalysts routinely used for the conversion of C-H bonds to C-C bonds are expensive. Catalytically active metals that are cheaper and less exotic (e.g., copper, iron, and manganese) are rarely used. This Account describes our attempts to provide solutions to these three problems. We have developed a general method for directing-group-containing arene arylation by aryl iodides. Using palladium acetate as the catalyst, we arylated anilides, benzamides, benzoic acids, benzylamines, and 2-substituted pyridine derivatives under nearly identical conditions. We have also developed a method for the palladium-catalyzed auxiliary-assisted arylation of unactivated sp(3) C-H bonds. This procedure allows for the beta-arylation of carboxylic acid derivatives and the gamma-arylation of amine derivatives. Furthermore, copper catalysis can be used to mediate the arylation of acidic arene C-H bonds (i.e., those with pK(a) values <35 in DMSO). Using a copper iodide catalyst in combination with a base and a phenanthroline ligand, we successfully arylated electron-rich and electron-deficient heterocycles and electron-poor arenes possessing at least two electron-withdrawing groups. The reaction exhibits unusual regioselectivity: arylation occurs at the most hindered position. This copper-catalyzed method supplements the well-known C-H activation/borylation methodology, in which functionalization usually occurs at the least hindered position. We also describe preliminary investigations to determine the mechanisms of these transformations. We anticipate that other transition metals, including iron, nickel, cobalt, and silver, will also be able to facilitate deprotonation/arylation reaction sequences.

Controlling First-Row Catalysts: Amination of Aryl and Heteroaryl Chlorides and Bromides with Primary Aliphatic Amines Catalyzed by a BINAP-Ligated Single-Component Ni(0) Complex

PubMed Central

2015-01-01

First-row metal complexes often undergo undesirable one-electron redox processes during two-electron steps of catalytic cycles. We report the amination of aryl chlorides and bromides with primary aliphatic amines catalyzed by a well-defined, single-component nickel precursor (BINAP)Ni(η2-NC-Ph) (BINAP = 2,2′-bis(biphenylphosphino)-1,1′-binaphthalene) that minimizes the formation of Ni(I) species and (BINAP)2Ni. The scope of the reaction encompasses electronically varied aryl chlorides and nitrogen-containing heteroaryl chlorides, including pyridine, quinoline, and isoquinoline derivatives. Mechanistic studies support the catalytic cycle involving a Ni(0)/Ni(II) couple for this nickel-catalyzed amination and are inconsistent with a Ni(I) halide intermediate. Monitoring the reaction mixture by 31P NMR spectroscopy identified (BINAP)Ni(η2-NC-Ph) as the resting state of the catalyst in the amination of both aryl chlorides and bromides. Kinetic studies showed that the amination of aryl chlorides and bromides is first order in both catalyst and aryl halide and zero order in base and amine. The reaction of a representative aryl chloride is inverse first order in PhCN, but the reaction of a representative aryl bromide is zero order in PhCN. This difference in the order of the reaction in PhCN indicates that the aryl chloride reacts with (BINAP)Ni(0), formed by dissociation PhCN from (BINAP)Ni(η2-NC-Ph), but the aryl bromide directly reacts with (BINAP)Ni(η2-NC-Ph). The overall kinetic behavior is consistent with turnover-limiting oxidative addition of the aryl halide to Ni(0). Several pathways for catalyst decomposition were identified, such as the formation of the catalytically inactive bis(amine)-ligated arylnickel(II) chloride, (BINAP)2Ni(0), and the Ni(I) species [(BINAP)Ni(μ-Cl)]2. By using a well-defined nickel complex as catalyst, the formation of (BINAP)2Ni(0) is avoided and the formation of the Ni(I) species [(BINAP)Ni(μ-Cl)]2 is minimized. PMID:24397570

Correlation of Hydrogen-Atom Abstraction Reaction Efficiencies for Aryl Radicals with their Vertical Electron Affinities and the Vertical Ionization Energies of the Hydrogen Atom Donors

PubMed Central

Jing, Linhong; Nash, John J.

2009-01-01

The factors that control the reactivities of aryl radicals toward hydrogen-atom donors were studied by using a dual-cell Fourier-transform ion cyclotron resonance mass spectrometer (FT – ICR). Hydrogen-atom abstraction reaction efficiencies for two substrates, cyclohexane and isopropanol, were measured for twenty-three structurally different, positively-charged aryl radicals, which included dehydrobenzenes, dehydronaphthalenes, dehydropyridines, and dehydro(iso)quinolines. A logarithmic correlation was found between the hydrogen-atom abstraction reaction efficiencies and the (calculated) vertical electron affinities (EA) of the aryl radicals. Transition state energies calculated for three of the aryl radicals with isopropanol were found to correlate linearly with their (calculated) EAs. No correlation was found between the hydrogen-atom abstraction reaction efficiencies and the (calculated) enthalpy changes for the reactions. Measurement of the reaction efficiencies for the reactions of several different hydrogen-atom donors with a few selected aryl radicals revealed a logarithmic correlation between the hydrogen-atom abstraction reaction efficiencies and the vertical ionization energies (IE) of the hydrogen-atom donors, but not the lowest homolytic X – H (X = heavy atom) bond dissociation energies of the hydrogen-atom donors. Examination of the hydrogen-atom abstraction reactions of twenty-nine different aryl radicals and eighteen different hydrogen-atom donors showed that the reaction efficiency increases (logarithmically) as the difference between the IE of the hydrogen-atom donor and the EA of the aryl radical decreases. This dependence is likely to result from the increasing polarization, and concomitant stabilization, of the transition state as the energy difference between the neutral and ionic reactants decreases. Thus, the hydrogen-atom abstraction reaction efficiency for an aryl radical can be “tuned” by structural changes that influence either the vertical EA of the aryl radical or the vertical IE of the hydrogen atom donor. PMID:19061320

Covalent Crosslinking of Carbon Nanotube Materials for Improved Tensile Strength

NASA Technical Reports Server (NTRS)

Baker, James S.; Miller, Sandi G.; Williams, Tiffany A.; Meador, Michael A.

2013-01-01

Carbon nanotubes have attracted much interest in recent years due to their exceptional mechanical properties. Currently, the tensile properties of bulk carbon nanotube-based materials (yarns, sheets, etc.) fall far short of those of the individual nanotube elements. The premature failure in these materials under tensile load has been attributed to inter-tube sliding, which requires far less force than that needed to fracture individual nanotubes.1,2 In order for nanotube materials to achieve their full potential, methods are needed to restrict this tube-tube shear and increase inter-tube forces.Our group is examining covalent crosslinking between the nanotubes as a means to increase the tensile properties of carbon nanotube materials. We are working with multi-walled carbon nanotube (MWCNT) sheet and yarn materials obtained from commercial sources. Several routes to functionalize the nanotubes have been examined including nitrene, aryl diazonium, and epoxide chemistries. The functional nanotubes were crosslinked through small molecule or polymeric bridges. Additionally, electron beam irradiation induced crosslinking of the non-functional and functional nanotube materials was conducted. For example, a nanotube sheet material containing approximately 3.5 mol amine functional groups exhibited a tensile strength of 75 MPa and a tensile modulus of 1.16 GPa, compared to 49 MPa and 0.57 GPa, respectively, for the as-received material. Electron beam irradiation (2.2x 1017 ecm2) of the same amine-functional sheet material further increased the tensile strength to 120 MPa and the modulus to 2.61 GPa. This represents approximately a 150 increase in tensile strength and a 360 increase in tensile modulus over the as-received material with only a 25 increase in material mass. Once we have optimized the nanotube crosslinking methods, the performance of these materials in polymer matrix composites will be evaluated.

Surface Grafting of Ru(II) Diazonium-Based Sensitizers on Metal Oxides Enhances Alkaline Stability for Solar Energy Conversion.

PubMed

Bangle, Rachel; Sampaio, Renato N; Troian-Gautier, Ludovic; Meyer, Gerald J

2018-01-24

The electrografting of [Ru(ttt)(tpy-C 6 H 4 -N 2 + )] 3+ , where "ttt" is 4,4',4″-tri-tert-butyl-2,2':6',2″-terpyridine, was investigated on several wide band gap metal oxide surfaces (TiO 2 , SnO 2 , ZrO 2 , ZnO, In 2 O 3 :Sn) and compared to structurally analogous sensitizers that differed only by the anchoring group, i.e., -PO 3 H 2 and -COOH. An optimized procedure for diazonium electrografting to semiconductor metal oxides is presented that allowed surface coverages that ranged between 4.7 × 10 -8 and 10.6 × 10 -8 mol cm -2 depending on the nature of the metal oxide. FTIR analysis showed the disappearance of the diazonium stretch at 2266 cm -1 after electrografting. XPS analysis revealed a characteristic peak of Ru 3d at 285 eV as well as a peak at 531.6 eV that was attributed to O 1s in Ti-O-C bonds. Photocurrents were measured to assess electron injection efficiency of these modified surfaces. The electrografted sensitizers exhibited excellent stability across a range of pHs spanning from 1 to 14, where classical binding groups such as carboxylic and phosphonic derivatives were hydrolyzed.

Synthesis of aryl azides and vinyl azides via proline-promoted CuI-catalyzed coupling reactions.

PubMed

Zhu, Wei; Ma, Dawei

2004-04-07

The coupling reaction of aryl halides or vinyl iodide with sodium azide under catalysis of CuI/L-proline works at relatively low temperature to provide aryl azides or vinyl azides in good to excellent yields.

Mechanism of the Reaction between Alkyl- and Aryl Grignard Reagents and Hexachlorocyclotriphosphazene: An Explanation of Bi(Cyclophosphazene Formation).

DTIC Science & Technology

1982-06-24

ADAI& "I PENNSYLVANIA STATE UNIV UNIVERSITY PARK DEPT OF CHEMISTRY F/S 7/3 ADA MECHANISM OF THE REACTION BETWEEN ALKYL - AND ARYL GRIGNARD REMG-ETC (U...TITLE (and Subliflo) S. TYPE OF REPORT A PERIOD COVERED MECHANISM OF THE REACTION BETWEEN ALKYL - AND ARYL GRIGNARD REAGENTS AND HEXACHLOROCYCLOTRIPHOS...Report No. 27 MECHANISM OF THE REACTION BETWEEN ALKYL - AND ARYL GRIGNARD REAGENTS AND HEXACHLOROCYCLOTRIPHOSPHAZENE: AN EXPLANATION OF BI(CYCLOPHOSPHAZENE

Palladium-catalysed carbonylative α-arylation of nitromethane.

PubMed

Lian, Zhong; Friis, Stig D; Skrydstrup, Troels

2015-02-28

A simple and mild Pd-catalysed carbonylative α-arylation of nitromethane has been realised providing access to α-nitro aryl ketones from an array of aryl and heteroaryl iodides. The methodology requires only a mild base and uses the convenient solid CO releasing molecule, COgen in a two-chamber system. Changing to the isotopically labelled (13)COgen, [(13)C]-acyl labelling can be effected through the generation of a near stoichiometric amount of (13)CO. Lastly, the significance of the generated products as synthetic intermediates is demonstrated.

OBO-Protected Pyruvates as Reagents for the Synthesis of Functionalized Heteroaromatic Compounds.

PubMed

Alves Esteves, C Henrique; Koyioni, Maria; Christensen, Kirsten E; Smith, Peter D; Donohoe, Timothy J

2018-06-15

Pd-catalyzed α-arylation of methyl-OBO-ketone (OBO = 4-methyl-2,6,7-trioxabicyclo[2.2.2]octan-1-yl) gives rise to arylated OBO-protected pyruvates. By appropriate prefunctionalization of the aryl ring or by subsequent functionalization at the α-carbonyl position of the arylated OBO-ketones, useful diketo OBO-protected carboxylates can be generated. Cyclization, aromatization, and OBO deprotection of these intermediates, using two distinct routes, gives access to valuable α-acyl heteroaromatic compounds.

Diastereoselective Synthesis of Symmetrical and Unsymmetrical Tetrahydropyridines Catalyzed by Bi(III) Immobilized on Triazine Dendrimer Stabilized Magnetic Nanoparticles.

PubMed

Asadi, Beheshteh; Landarani-Isfahani, Amir; Mohammadpoor-Baltork, Iraj; Tangestaninejad, Shahram; Moghadam, Majid; Mirkhani, Valiollah; Amiri Rudbari, Hadi

2017-06-12

Unsymmetrical 1,2,5,6-tetrahydropyridine-3-carboxylates were obtained for the first time from a five-component Fe 3 O 4 @TDSN-Bi(III)-catalyzed reaction of aryl aldehydes, aryl amines, and ethyl acetoacetate. This magnetically separable catalyst enabled the selective incorporation of two different aryl amines or two different aryl aldehydes into the product, and provided excellent yields, short reaction times, mild reaction conditions, satisfactory catalyst recyclability, and low catalyst loading.

Spontaneous grafting: a novel approach to graft diazonium cations on gold nanoparticles in aqueous medium and their self-assembly on electrodes.

PubMed

Kesavan, Srinivasan; John, S Abraham

2014-08-15

The spontaneous grafting of aminophenyl groups on gold nanoparticles (AuNPs) by reaction with in situ generated 4-aminophenyl diazonium cations (APD) in an aqueous medium was described. The spontaneous grafting was likely to proceed by transfer of electrons from AuNPs to the APD cations to form an aminophenyl radical and subsequent attachment with AuNPs. The aminophenyl (AP) functionalized gold nanoparticles (AP-AuNPs) were characterized by UV-visible spectroscopy, high resolution-transmission electron microscopy (HR-TEM), X-ray diffraction, FT-IR spectroscopy, X-ray photoelectron spectroscopy (XPS) and surface-enhanced Raman spectroscopy (SERS). The absence of characteristic vibrational bands corresponding to diazonium group in the FT-IR spectrum confirmed the reduction of the aminophenyl diazonium cations at the surface of AuNPs. The spontaneous attachment of AP on AuNPs was confirmed by XPS from the observed binding energy values for -NH2 at 399.4 eV and -N=N- at 400.2 eV. The SERS spectrum reveals the presence Au-C (437 cm(-1)) bond on AP-AuNPs. Further, the AP-AuNPs were self-assembled on GC/ITO electrode (AP-AuNPs modified electrode) with the aid of free amine groups present on the surface of AP-AuNPs via Michael's nucleophilic addition reaction. The AP-AuNPs modified electrode was characterized by cyclic voltammetry, impedance spectroscopy, UV-visible spectroscopy and scanning electron microscopy. Impedance studies show that the electron transfer reaction of [Fe(CN)6](3-/4-) was higher at the AP-AuNPs modified electrode (1.81×10(-4) cm s(-1)) than at bare (3.77×10(-5) cm s(-1)) GC electrode. Finally, the electrocatalytic activity of the AP-AuNPs modified electrode was demonstrated by studying the oxidation of dopamine (DA). Copyright © 2014 Elsevier Inc. All rights reserved.

Palladium-Catalyzed α-Arylation of Zinc Enolates of Esters: Reaction Conditions and Substrate Scope

PubMed Central

Hama, Takuo; Ge, Shaozhong; Hartwig, John F.

2013-01-01

The intermolecular α-arylation of esters by palladium-catalyzed coupling of aryl bromides with zinc enolates of esters is reported. Reactions of three different types of zinc enolates have been developed. α-Arylation of esters occurs in high yields with isolated Reformatsky reagents, with Reformatsky reagents generated from α-bromo esters and activated zinc, and with zinc enolates generated by quenching lithium enolates of esters with zinc chloride. The use of zinc enolates, instead of alkali metal enolates, greatly expands the scope of the arylation of esters. The reactions occur at room temperature or at 70 °C with bromoarenes containing cyano, nitro, ester, keto, fluoro, enolizable hydrogen, hydroxyl or amino functionality and with bromopyridines. The scope of esters encompasses acyclic acetates, propionates, and isobutyrates, α-alkoxyesters, and lactones. The arylation of zinc enolates of esters was conducted with catalysts bearing the hindered pentaphenylferrocenyl di-tert-butylphosphine (Q-phos) or the highly reactive dimeric Pd(I) complex {[P(t-Bu)3]PdBr}2. PMID:23931445

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

2015-09-07

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. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A halogenophilic pathway in the reactions of transition metal carbonyl anions with [(η⁶-iodobenzene)Cr(CO)₃].

PubMed

Sazonov, Petr K; Ivushkin, Vasiliy A; Khrustalev, Victor N; Kolotyrkina, Natal'ya G; Beletskaya, Irina P

2014-09-21

The paper provides the first example of formal nucleophilic substitution by the halogenophilic pathway in Cr(CO)3 complexes of haloarenes with metal carbonyl anions. All metal carbonyl anions examined attack [(η(6)-iodobenzene)Cr(CO)3] at halogen, which is shown by aryl carbanion scavenging with t-BuOH. The reaction with K[CpFe(CO)2] gives only the dehalogenated arene, but the reaction with K[Cp*Fe(CO)2] (Cp* = η(5)-C5Me5) results in nucleophilic substitution to give [(η(6)-C6H5FeCp*(CO)2)Cr(CO)3]. Reaction with Na[Re(CO)5] quantitatively gives the iodo(acyl)rhenate anion Na[(η(6)-C6H5C(O)ReI(CO)4)Cr(CO)3] and in the case of K[Mn(CO)5] a mixture of σ-aryl complexes [(η(6)-C6H5Mn(CO)5)Cr(CO)3] and K[(η(6)-C6H5Mn(CO)4I)Cr(CO)3]. An analogous rhenium complex Na[(η(6)-C6H5Re(CO)4I)Cr(CO)3] is formed from the initial iodo(acyl)rhenate upon prolonged standing at 20 °C, and its structure (in the form of [NEt4](+) salt) is established by X-ray diffraction analysis. The reaction of [(η(6)-chlorobenzene)Cr(CO)3] with K[CpFe(CO)2], in contrast, proceeds by the common S(N)2Ar mechanism.

Optimization of Aryl Amides that Extend Survival in Prion-Infected Mice.

PubMed

Giles, Kurt; Berry, David B; Condello, Carlo; Dugger, Brittany N; Li, Zhe; Oehler, Abby; Bhardwaj, Sumita; Elepano, Manuel; Guan, Shenheng; Silber, B Michael; Olson, Steven H; Prusiner, Stanley B

2016-09-01

Developing therapeutics for neurodegenerative diseases (NDs) prevalent in the aging population remains a daunting challenge. With the growing understanding that many NDs progress by conformational self-templating of specific proteins, the prototypical prion diseases offer a platform for ND drug discovery. We evaluated high-throughput screening hits with the aryl amide scaffold and explored the structure-activity relationships around three series differing in their N-aryl core: benzoxazole, benzothiazole, and cyano. Potent anti-prion compounds were advanced to pharmacokinetic studies, and the resulting brain-penetrant leads from each series, together with a related N-aryl piperazine lead, were escalated to long-term dosing and efficacy studies. Compounds from each of the four series doubled the survival of mice infected with a mouse-passaged prion strain. Treatment with aryl amides altered prion strain properties, as evidenced by the distinct patterns of neuropathological deposition of prion protein and associated astrocytic gliosis in the brain; however, none of the aryl amide compounds resulted in drug-resistant prion strains, in contrast to previous studies on compounds with the 2-aminothiazole (2-AMT) scaffold. As seen with 2-AMTs and other effective anti-prion compounds reported to date, the novel aryl amides reported here were ineffective in prolonging the survival of transgenic mice infected with human prions. Most encouraging is our discovery that aryl amides show that the development of drug resistance is not an inevitable consequence of efficacious anti-prion therapeutics. Copyright © 2016 by The American Society for Pharmacology and Experimental Therapeutics.

Optimization of Aryl Amides that Extend Survival in Prion-Infected Mice

PubMed Central

Giles, Kurt; Berry, David B.; Condello, Carlo; Dugger, Brittany N.; Li, Zhe; Oehler, Abby; Bhardwaj, Sumita; Elepano, Manuel; Guan, Shenheng; Silber, B. Michael; Olson, Steven H.

2016-01-01

Developing therapeutics for neurodegenerative diseases (NDs) prevalent in the aging population remains a daunting challenge. With the growing understanding that many NDs progress by conformational self-templating of specific proteins, the prototypical prion diseases offer a platform for ND drug discovery. We evaluated high-throughput screening hits with the aryl amide scaffold and explored the structure–activity relationships around three series differing in their N-aryl core: benzoxazole, benzothiazole, and cyano. Potent anti-prion compounds were advanced to pharmacokinetic studies, and the resulting brain-penetrant leads from each series, together with a related N-aryl piperazine lead, were escalated to long-term dosing and efficacy studies. Compounds from each of the four series doubled the survival of mice infected with a mouse-passaged prion strain. Treatment with aryl amides altered prion strain properties, as evidenced by the distinct patterns of neuropathological deposition of prion protein and associated astrocytic gliosis in the brain; however, none of the aryl amide compounds resulted in drug-resistant prion strains, in contrast to previous studies on compounds with the 2-aminothiazole (2-AMT) scaffold. As seen with 2-AMTs and other effective anti-prion compounds reported to date, the novel aryl amides reported here were ineffective in prolonging the survival of transgenic mice infected with human prions. Most encouraging is our discovery that aryl amides show that the development of drug resistance is not an inevitable consequence of efficacious anti-prion therapeutics. PMID:27317802

Hydration effects on the photoionization energy of 2‧-deoxyguanosine 5‧-phosphate and activation barriers for guanine methylation by carcinogenic methane diazonium ions

NASA Astrophysics Data System (ADS)

Eichler, Daniel R.; Hamann, Haley A.; Harte, Katherine A.; Papadantonakis, George A.

2017-07-01

Results from DFT calculations indicate that states originating from gas-phase ionization of the phosphate and the base are degenerate in syn-5‧-dGMP- and that bulk hydration lowers the base-localized ionization energy by <0.5 eV. Local ionization maps show that micro-hydration leads to the formation of donor and acceptor hydrogen bonds and the ionization energy decreases or increases in each case respectively. The SN2 transition states of the methylation reactions of guanine with methane diazonium ions are lower at the N7 than at the O6 sites and they are influenced by local ionization energy and steric interference.

Controlling formation of single-molecule junctions by electrochemical reduction of diazonium terminal groups.

PubMed

Hines, Thomas; Díez-Pérez, Ismael; Nakamura, Hisao; Shimazaki, Tomomi; Asai, Yoshihiro; Tao, Nongjian

2013-03-06

We report controlling the formation of single-molecule junctions by means of electrochemically reducing two axialdiazonium terminal groups on a molecule, thereby producing direct Au-C covalent bonds in situ between the molecule and gold electrodes. We report a yield enhancement in molecular junction formation as the electrochemical potential of both junction electrodes approach the reduction potential of the diazonium terminal groups. Step length analysis shows that the molecular junction is significantly more stable, and can be pulled over a longer distance than a comparable junction created with amine anchoring bonds. The stability of the junction is explained by the calculated lower binding energy associated with the direct Au-C bond compared with the Au-N bond.

A novel conversion of C(19)-diterpenoid alkaloids into aconane-type diterpenes with eight-membered ring system via skeletal rearrangement of corresponding diazonium derivatives.

PubMed

Ji, Hong; Chen, Qiao-Hong; Wang, Feng-Peng

2009-03-01

A new and efficient approach toward the conversion of C(19)-diterpenoid alkaloids into diterpenes with [6+8+5+6] ring system is reported. Treatment of imines 5, 14, and 24 derived from the C(19)-diterpenoid alkaloids with NaNO(2)-NaOAc-HOAc afforded a series of novel rearrangement diterpenes 6-8, 15-19, and 25-27, respectively. The lactone 11 was obtained in 41% yield by treating 5 with NaNO(2)-HBr-Br(2). The formation of diazonium intermediate is postulated, which was subsequently subjected to skeletal rearrangement, leading to the enlargement of B ring. All the new compounds were isolated and fully characterized.

Pd-Catalyzed Cross-Coupling Reactions of Amides and Aryl Mesylates

PubMed Central

Dooleweerdt, Karin; Fors, Brett P.; Buchwald, Stephen L.

2010-01-01

A catalyst, based on a biarylphosphine ligand, for the Pd-catalyzed cross-coupling reactions of amides and aryl mesylates is described. This system allows an array of aryl and heteroaryl mesylates to be transformed into the corresponding N-arylamides in moderate to excellent yields. PMID:20420379

40 CFR 721.10367 - Hydroxy-aryl, polymer with substituted benzene, cyanate (generic).

Code of Federal Regulations, 2014 CFR

2014-07-01

... benzene, cyanate (generic). 721.10367 Section 721.10367 Protection of Environment ENVIRONMENTAL PROTECTION... New Uses for Specific Chemical Substances § 721.10367 Hydroxy-aryl, polymer with substituted benzene... substance identified generically as hydroxy-aryl, polymer with substituted benzene, cyanate (PMN P-10-83) is...

40 CFR 721.10367 - Hydroxy-aryl, polymer with substituted benzene, cyanate (generic).

Code of Federal Regulations, 2012 CFR

2012-07-01

... benzene, cyanate (generic). 721.10367 Section 721.10367 Protection of Environment ENVIRONMENTAL PROTECTION... New Uses for Specific Chemical Substances § 721.10367 Hydroxy-aryl, polymer with substituted benzene... substance identified generically as hydroxy-aryl, polymer with substituted benzene, cyanate (PMN P-10-83) is...

40 CFR 721.10367 - Hydroxy-aryl, polymer with substituted benzene, cyanate (generic).

Code of Federal Regulations, 2013 CFR

2013-07-01

... benzene, cyanate (generic). 721.10367 Section 721.10367 Protection of Environment ENVIRONMENTAL PROTECTION... New Uses for Specific Chemical Substances § 721.10367 Hydroxy-aryl, polymer with substituted benzene... substance identified generically as hydroxy-aryl, polymer with substituted benzene, cyanate (PMN P-10-83) is...

Merging Photoredox and Nickel Catalysis: The Direct Synthesis of Ketones via the Decarboxylative Arylation of α-Oxo Acids**

PubMed Central

Chu, Lingling; Lipshultz, Jeffrey M.

2015-01-01

The direct decarboxylative arylation of α-oxo acids has been achieved via synergistic visible light-mediated photoredox and nickel catalyses. This method offers rapid entry to aryl and alkyl ketone architectures from simple α-oxo acid precursors via an acyl radical intermediate. Significant substrate scope is observed with respect to both the oxo acid and arene coupling partners. This mild decarboxylative arylation can also be utilized to efficiently access medicinal agents, as demonstrated by the rapid synthesis of fenofibrate. PMID:26014029

The synthesis of α-aryl-α-aminophosphonates and α-aryl-α-aminophosphine oxides by the microwave-assisted Pudovik reaction

PubMed Central

Tajti, Ádám; Ádám, Anna; Csontos, István; Karaghiosoff, Konstantin; Czugler, Mátyás; Ábrányi-Balogh, Péter

2017-01-01

A family of α-aryl-α-aminophosphonates and α-aryl-α-aminophosphine oxides was synthesized by the microwave-assisted solvent-free addition of dialkyl phosphites and diphenylphosphine oxide, respectively, to imines formed from benzaldehyde derivatives and primary amines. After optimization, the reactivity was mapped, and the fine mechanism was evaluated by DFT calculations. Two α-aminophosphonates were subjected to an X-ray study revealing a racemic dimer formation made through a N–H···O=P intermolecular hydrogen bridges pair. PMID:28179951

Copper(II)-catalyzed hydroxylation of aryl halides using glycolic acid as a ligand.

PubMed

Xiao, Yan; Xu, Yongnan; Cheon, Hwan-Sung; Chae, Junghyun

2013-06-07

Copper(II)-catalyzed hydroxylation of aryl halides has been developed to afford functionalized phenols. The protocol utilizes the reagent combination of Cu(OH)2, glycolic acid, and NaOH in aqueous DMSO, all of which are cheap, readily available, and easily removable after the reaction. A broad range of aryl iodides and activated aryl bromides were transformed into the corresponding phenols in excellent yields. Moreover, it has been shown that C-O(alkyl)-coupled product, instead of phenol, can be predominantly formed under similar reaction conditions.

Suzuki-Miyaura Cross-Coupling Reactions of Primary Alkyltrifluoroborates with Aryl Chlorides

PubMed Central

Dreher, Spencer D.; Lim, Siang-Ee; Sandrock, Deidre L.; Molander, Gary A.

2009-01-01

Parallel microscale experimentation was used to develop general conditions for the Suzuki-Miyaura cross-coupling of diversely functionalized primary alkyltrifluoroborates with a variety of aryl chlorides. These conditions were found to be amenable to coupling with aryl bromides, iodides, and triflates as well. The conditions that were previously identified through similar techniques to promote the cross-coupling of secondary alkyltrifluoroborates with aryl chlorides were not optimal for the primary alkyltrifluoroborates, thus demonstrating the value of parallel experimentation to develop novel, substrate specific results. PMID:19271726

Design and synthesis of aryl ether and sulfone hydroxamic acids as potent histone deacetylase (HDAC) inhibitors.

PubMed

Pabba, Chittari; Gregg, Brian T; Kitchen, Douglas B; Chen, Zhen Jia; Judkins, Angela

2011-01-01

A series of novel hydroxamic acid based histone deacetylases (HDAC) inhibitors with aryl ether and aryl sulfone residues at the terminus of a substituted, unsaturated 5-carbon spacer moiety have been synthesized for the first time and evaluated. Compounds with meta- and para-substitution on the aryl ring of ether hydroxamic acids 19c, 20c, 19e, 19f and 19g are potent HDAC inhibitors with activities at low nanomolar levels. Copyright © 2010 Elsevier Ltd. All rights reserved.

Reusable copper-catalyzed cross-coupling reactions of aryl halides with organotins in inexpensive ionic liquids.

PubMed

Li, Jin-Heng; Tang, Bo-Xiao; Tao, Li-Ming; Xie, Ye-Xiang; Liang, Yun; Zhang, Man-Bo

2006-09-15

A combination of Cu2O nanoparticles with P(o-tol)3 shows highly catalytic activity for the Stille cross-coupling reaction. A series of copper catalysts and ligands were evaluated, and Cu2O nanoparticles combined with P(o-tol)3 provided the best results. In the presence of Cu2O nanoparticles and P(o-tol)3, a variety of aryl halides including aryl chlorides underwent the Stille reaction with organotins smoothly in moderate to excellent yields using inexpensive TBAB (n-Bu4NBr) as the medium. It is noteworthy that the Cu2O/P(o-tol)3/TBAB system can be recovered and reused at least three times without any loss of catalytic activity among the reactions of aryl iodides and activated aryl bromides.

Homogeneous and Supported Niobium Catalysts as Lewis Acid and Radical Catalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wayne Tikkanen

2006-12-31

The synthesis of tetrachlorotetraphenylcyclopentadienyl group 5 metal complexes has been accomplished through two routes, one a salt metathesis with lithiumtetraphenylcyclopentadiende and the other, reaction with trimethyltintetraphenylcyclopentadiene. The reactants and products have been characterized by {sup 1}H and {sup 13}C({sup 1}H) NMR spectroscopy. The niobium complex promotes the silylcyanation of butyraldehyde. The grafting of metal complexes to silica gel surfaces has been accomplished using tetrakisdimethylamidozirconium as the metal precursor. The most homogeneous binding as determined by CP-MAS {sup 13}C NMR and infrared spectroscopy was obtained with drying at 500 C at 3 mtorr vacuum. The remaining amido groups can be replacedmore » by reaction with alcohols to generate surface bound metal alkoxides. These bound catalysts promote silylcyanation of aryl aldehydes and can be reused three times with no loss of activity.« less

Tetraphenylphosphonium allyldithiocarbimates derived from Morita-Baylis-Hillman adducts: Synthesis, characterization, crystal structure and antifungal activity

NASA Astrophysics Data System (ADS)

Tavares, Eder C.; Rubinger, Mayura M. M.; Filho, Eclair V.; Oliveira, Marcelo R. L.; Piló-Veloso, Dorila; Ellena, Javier; Guilardi, Silvana; Souza, Rafael A. C.; Zambolim, Laércio

2016-02-01

Botrytis blight is a very destructive disease caused by Botrytis spp., infecting flowers, trees, vegetables and fruits. Twelve new compounds were prepared by the reaction of potassium N-aryl-sulfonyldithiocarbimates with Morita-Baylis-Hillman derivatives bearing phenyl and furyl groups. These are the first examples of allyldithiocarbimate anions and were isolated as tetraphenylphosphonium salts. The new compounds were characterized by HRMS, NMR and Infrared spectroscopy. Further, the structures of three allyldithiocarbimates were determined by single crystal X-ray diffraction. The compounds are isostructural and crystallize in the space group P21/c of the monoclinic system, and the allyldithiocarbimate anions present Z configuration. All the compounds were active against Botrytis cinerea. The best results were achieved with the tetraphenylphosphonium (Z)-3-(furan-2-yl)-2-(methoxycarbonyl)allyl-(4-chlorophenylsulfonyl)dithiocarbimate (IC50 38 μM).

Phenanthridine synthesis through iron-catalyzed intramolecular N-arylation of O-acetyl oxime.

PubMed

Deb, Indubhusan; Yoshikai, Naohiko

2013-08-16

O-Acetyl oximes derived from 2'-arylacetophenones undergo N-O bond cleavage/intramolecular N-arylation in the presence of a catalytic amount of iron(III) acetylacetonate in acetic acid. In combination with the conventional cross-coupling or directed C-H arylation, the reaction offers a convenient route to substituted phenanthridines.

Synthesis of 1,2-cis-2-C-branched aryl-C-glucosides via desulfurization of carbohydrate based hemithioacetals

PubMed Central

Mebrahtu, Fanuel M; Manana, Mandlenkosi M; Madumo, Kagiso; Sokamisa, Mokela S

2015-01-01

Summary 1-C and 2-C-branched carbohydrates are present as substructures in a number of biologically important compounds. Although the synthesis of such carbohydrate derivatives is extensively studied, the synthesis of 1,2-cis-2-C-branched C-, S-, and N-glycosides is less explored. In this article a synthetic strategy for the synthesis of 1,2-cis-2-C-branched-aryl-C-glucosides is reported via a hydrogenolytic desulfurization of suitably orientated carbohydrate based hemithioacetals. 1,2-cis-2-Hydroxymethyl and 2-carbaldehyde of aryl-C-glucosides have been synthesized using the current strategy in very good yields. The 2-carbaldehyde-aryl-C-glucosides have been identified as suitable substrates for the stereospecific preparation of 2,3-unsaturated-aryl-C-glycosides (Ferrier products). PMID:26124859

General and mild Ni(0)-catalyzed α-arylation of ketones using aryl chlorides.

PubMed

Fernández-Salas, José A; Marelli, Enrico; Cordes, David B; Slawin, Alexandra M Z; Nolan, Steven P

2015-03-02

A general methodology for the α-arylation of ketones using a nickel catalyst has been developed. The new well-defined [Ni(IPr*)(cin)Cl] (1 c) pre-catalyst showed great efficiency for this transformation, allowing the coupling of a wide range of ketones, including acetophenone derivatives, with various functionalised aryl chlorides. This cinnamyl-based Ni-N-heterocyclic carbene (NHC) complex has demonstrated a different behaviour to previously reported NHC-Ni catalysts. Preliminary mechanistic studies suggest a Ni(0)/Ni(II) catalytic cycle to be at play. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Palladium-catalyzed cross-coupling of aryl chlorides and triflates with sodium cyanate: A practical synthesis of unsymmetrical ureas

PubMed Central

Vinogradova, Ekaterina V.; Fors, Brett P.; Buchwald, Stephen L.

2012-01-01

An efficient method for palladium-catalyzed cross-coupling of aryl chlorides and triflates with sodium cyanate is reported. The protocol allows for the synthesis of unsymmetrical N,N'-di- and N,N,N'-trisubstituted ureas in one pot, and is tolerant of a wide range of functional groups. Insight into the mechanism of aryl isocyanate formation is gleaned through studies of the transmetallation and reductive elimination steps of the reaction, including the first demonstration of reductive elimination from an arylpalladium isocyanate complex to produce an aryl isocyanate. PMID:22716197

Redox shuttle additives for lithium-ion batteries

DOEpatents

Zhang, Lu; Zhang, Zhengcheng; Amine, Khalil

2017-03-21

An electro lye includes a compound of Formula I or IA: where each instance of R.sup.1 is independently H, alkyl, alkoxy, alkenyl, aryl, heteroaryl, or cycloalkyl; each instance of R.sup.2 is independently H, alkyl, alkoxy, alkenyl, aryl, heteroaryl, or cycloalkyl; each instance of R.sup.3 is independently H, alkyl, alkenyl, aryl, or cycloalkyl; each instance of R.sup.4 is independently H, halogen, CN, NO.sub.2, phosphate, alkyl, alkenyl, aryl, heteroaryl, or cycloalkyl; x is 1, 2, 3, 4, or 5; y is 1 or 2; and z is 0, 1, 2, 3, or 4. ##STR00001##

Utilization of acidic α-amino acids as acyl donors: an effective stereo-controllable synthesis of aryl-keto α-amino acids and their derivatives.

PubMed

Wang, Lei; Murai, Yuta; Yoshida, Takuma; Okamoto, Masashi; Tachrim, Zetryana Puteri; Hashidoko, Yasuyuki; Hashimoto, Makoto

2014-05-16

Aryl-keto-containing α-amino acids are of great importance in organic chemistry and biochemistry. They are valuable intermediates for the construction of hydroxyl α-amino acids, nonproteinogenic α-amino acids, as well as other biofunctional components. Friedel-Crafts acylation is an effective method to prepare aryl-keto derivatives. In this review, we summarize the preparation of aryl-keto containing α-amino acids by Friedel-Crafts acylation using acidic α-amino acids as acyl-donors and Lewis acids or Brönsted acids as catalysts.

Copper-Catalyzed C(sp2)-S Coupling Reactions for the Synthesis of Aryl Dithiocarbamates with Thiuram Disulfide Reagents.

PubMed

Dong, Zhi-Bing; Liu, Xing; Bolm, Carsten

2017-11-03

An efficient protocol for the copper-catalyzed preparation of aryl dithiocarbamates from aryl iodides and inexpensive, environmentally benign tetraalkylthiuram disulfides was developed. The features of mild reaction conditions, high yields, and broad substrate scope render this new approach synthetically attractive for the preparation of potentially biologically active compounds.

Vibrational spectroscopic study of sulphated silk proteins

NASA Astrophysics Data System (ADS)

Monti, P.; Freddi, G.; Arosio, C.; Tsukada, M.; Arai, T.; Taddei, P.

2007-05-01

Degummed Bombyx mori ( B. m.) silk fibroin fabric and mutant naked pupa cocoons (Nd-s) consisting of almost pure silk sericin were treated with chlorosulphonic acid in pyridine and investigated by FT-IR and FT-Raman spectroscopies. Untreated silk fibroin and sericin displayed typical spectral features due to characteristic amino acid composition and molecular conformation (prevailing β-sheet with a less ordered structure in sericin). Upon sulphation, the degree of molecular disorder increased in both proteins and new bands appeared. The IR bands at 1049 and 1014 cm -1 were attributed to vibrations of sulphate salts and that at 1385 cm -1 to the νasSO 2 mode of organic covalent sulphates. In the 1300-1180 cm -1 range various contributions of alkyl and aryl sulphate salts, sulphonamides, sulphoamines and organic covalent sulphates, fell. Fibroin covalently bound sulphate groups through the hydroxyl groups of tyrosine and serine, while sericin through the hydroxyl groups of serine, since the δOH vibrations at 1399 cm -1 in IR and at 1408 cm -1 in Raman disappeared almost completely. Finally, the increase of the I850/ I830 intensity ratio of Raman tyrosine doublet in fibroin suggested a change towards a more exposed state of tyrosine residues, in good agreement with the more disordered conformation taken upon sulphation.

An influence of structural changes in ammonium cations on ecotoxicity of 2,2'-thiodiacetate mono and bis-salts.

PubMed

Biczak, R; Turek, M; Pawłowska, B; Różycka-Sokołowska, E; Marciniak, B; Deska, M; Krupa, P; Jatulewicz, I; Skalik, J; Bałczewski, P

2018-07-15

2,2'-Thiodiacetates with their excellent complexing properties may be used as metal extraction agents, fluorescent and superparamagnetic materials, antibacterial and anticancer medical agents, however there are no data concerning the environmental impact of 2,2'-thiodiacetates derivatives and data definying the potential hazard connected with their use. This study describes the ecotoxicity assessment of seven 2,2'-thiodiacetates with non-metallic, alkyl and aryl ammonium cations, which were obtained in an environmentally friendly, solvent-free syntheses. The ecotoxicity of these water soluble compounds was tested in aquatic and benthic environments using luminescent marine bacteria Vibrio fischeri (Microtox ® test) and the crustaceans Heterocypris incongruens (Ostracodtoxkit F™), respectively. The antimicrobial and antifungal activity against Trichoderma viridis, Aspergillus niger, Rhizoctonia solani and Escherichia coli was also investigated. The results showed how structural changes within ammonium cations themselves influence ecotoxicity: the QASs with alkylammonium cations exhibited a similar, rather low toxicity both to Vibrio fischeri and Heterocypris incongruens, and they would not pose a risk to these organisms in case of leakage. Higher toxicity was observed in case of two isoquinolinium salts, however it was rather associated with the heteroaromatic cation, than with the 2,2'-thiodiacetate anion. Copyright © 2018 Elsevier Inc. All rights reserved.

Aryl-Aryl Interactions in Designed Peptide Folds: Spectroscopic Characteristics and Placement Issues for Optimal Structure Stabilization

PubMed Central

Anderson, Jordan M.; Kier, Brandon; Jurban, Brice; Byrne, Aimee; Shu, Irene; Eidenschink, Lisa A.; Shcherbakov, Alexander A.; Hudson, Mike; Fesinmeyer, R. M.; Andersen, Niels H.

2017-01-01

We have extended our studies of Trp/Trp to other Aryl/Aryl through-space interactions that stabilize hairpins and other small polypeptide folds. Herein we detail the NMR and CD spectroscopic features of these types of interactions. NMR data remains the best diagnostic for characterizing the common T-shape orientation. Designated as an edge-to-face (EtF or FtE) interaction, large ring current shifts are produced at the edge aryl ring hydrogens and, in most cases, large exciton couplets appear in the far UV circular dichroic (CD) spectrum. The preference for the face aryl in FtE clusters is W≫Y≥F (there are some exceptions in the Y/F order); this sequence corresponds to the order of fold stability enhancement and always predicts the amplitude of the lower energy feature of the exciton couplet in the CD spectrum. The CD spectra for FtE W/W, W/Y, Y/W, and Y/Y pairs all include an intense feature at 225–232 nm. An additional couplet feature seen for W/Y, W/F, Y/Y and F/Y clusters, is a negative feature at 197–200 nm. Tyr/Tyr (as well as F/Y and F/F) interactions produce much smaller exciton couplet amplitudes. The Trp-cage fold was employed to search for the CD effects of other Trp/Trp and Trp/Tyr cluster geometries: several were identified. In this account, we provide additional examples of the application of cross-strand aryl/aryl clusters for the design of stable β-sheet models and a scale of fold stability increments associated with all possible FtE Ar/Ar clusters in several structural contexts. PMID:26850220

Novel Scheme for Biosynthesis of Aryl Metabolites from l-Phenylalanine in the Fungus Bjerkandera adusta

PubMed Central

Lapadatescu, Carmen; Giniès, Christian; Le Quéré, Jean-Luc; Bonnarme, Pascal

2000-01-01

Aryl metabolite biosynthesis was studied in the white rot fungus Bjerkandera adusta cultivated in a liquid medium supplemented with l-phenylalanine. Aromatic compounds were analyzed by gas chromatography-mass spectrometry following addition of labelled precursors (14C- and 13C-labelled l-phenylalanine), which did not interfere with fungal metabolism. The major aromatic compounds identified were benzyl alcohol, benzaldehyde (bitter almond aroma), and benzoic acid. Hydroxy- and methoxybenzylic compounds (alcohols, aldehydes, and acids) were also found in fungal cultures. Intracellular enzymatic activities (phenylalanine ammonia lyase, aryl-alcohol oxidase, aryl-alcohol dehydrogenase, aryl-aldehyde dehydrogenase, lignin peroxidase) and extracellular enzymatic activities (aryl-alcohol oxidase, lignin peroxidase), as well as aromatic compounds, were detected in B. adusta cultures. Metabolite formation required de novo protein biosynthesis. Our results show that l-phenylalanine was deaminated to trans-cinnamic acid by a phenylalanine ammonia lyase and trans-cinnamic acid was in turn converted to aromatic acids (phenylpyruvic, phenylacetic, mandelic, and benzoylformic acids); benzaldehyde was a metabolic intermediate. These acids were transformed into benzaldehyde, benzyl alcohol, and benzoic acid. Our findings support the hypothesis that all of these compounds are intermediates in the biosynthetic pathway from l-phenylalanine to aryl metabolites. Additionally, trans-cinnamic acid can also be transformed via β-oxidation to benzoic acid. This was confirmed by the presence of acetophenone as a β-oxidation degradation intermediate. To our knowledge, this is the first time that a β-oxidation sequence leading to benzoic acid synthesis has been found in a white rot fungus. A novel metabolic scheme for biosynthesis of aryl metabolites from l-phenylalanine is proposed. PMID:10742235

Selective Synthesis of 5- or 6-Aryl Octahydrocyclopenta[b]pyrroles from a Common Precursor Through Control of Competing Pathways in a Pd-Catalyzed Reaction

PubMed Central

Ney, Joshua E.; Wolfe, John P.

2009-01-01

The Pd/phosphine-catalyzed reaction of 1 with aryl bromides leads to the selective synthesis of either 6-aryl octahydrocyclopenta[b]pyrroles (3), the corresponding 5-aryl isomers 5, diarylamine 2, or hexahydrocyclopenta[b]pyrrole 4 depending on the structure of the phosphine ligand. These transformations are effective with a variety of different aryl bromides, and provide 3-5 with excellent levels of diastereoselectivity (dr ≥ 20:1). The changes in product distribution are believed to derive from the influence of Pd-catalyst structure on the relative rates of reductive elimination, β-hydride elimination, alkene insertion, and alkene dissociation processes in a mechanistically complex reaction. The effect of phosphine ligand structure on product distribution is described in detail, along with analysis of a proposed mechanism for these transformations. PMID:15954769

Divergent unprotected peptide macrocyclisation by palladium-mediated cysteine arylation.

PubMed

Rojas, Anthony J; Zhang, Chi; Vinogradova, Ekaterina V; Buchwald, Nathan H; Reilly, John; Pentelute, Bradley L; Buchwald, Stephen L

2017-06-01

Macrocyclic peptides are important therapeutic candidates due to their improved physicochemical properties in comparison to their linear counterparts. Here we detail a method for a divergent macrocyclisation of unprotected peptides by crosslinking two cysteine residues with bis-palladium organometallic reagents. These synthetic intermediates are prepared in a single step from commercially available aryl bis-halides. Two bioactive linear peptides with cysteine residues at i , i + 4 and i , i + 7 positions, respectively, were cyclised to introduce a diverse array of aryl and bi-aryl linkers. These two series of macrocyclic peptides displayed similar linker-dependent lipophilicity, phospholipid affinity, and unique volume of distributions. Additionally, one of the bioactive peptides showed target binding affinity that was predominantly affected by the length of the linker. Collectively, this divergent strategy allowed rapid and convenient access to various aryl linkers, enabling the systematic evaluation of the effect of appending unit on the medicinal properties of macrocyclic peptides.

Effect of acyl chain length on selective biocatalytic deacylation on O-aryl glycosides and separation of anomers.

PubMed

Aggarwal, Neha; Arya, Anu; Mathur, Divya; Singh, Sukhdev; Tyagi, Abhilash; Kumar, Rajesh; Rana, Neha; Singh, Rajendra; Prasad, Ashok K

2014-04-01

It has been demonstrated that Lipozyme® TL IM (Thermomyces lanuginosus lipase immobilised on silica) can selectively deacylate the ester function involving the C-5' hydroxyl group of α-anomers over the other acyl functions of anomeric mixture of peracylated O-aryl α,β-D-ribofuranoside. The analysis of results of biocatalytic deacylation reaction revealed that the reaction time decreases with the increase in the acyl chain length from C1 to C4. The unique selectivity of Lipozyme® TL IM has been harnessed for the separation of anomeric mixture of peracylated O-aryl α,β-D-ribofuranosides, The lipase mediated selective deacylation methodology has been used for the synthesis of O-aryl α-D-ribofuranosides and O-aryl β-D-ribofuranosides in pure forms, which can be used as chromogenic substrate for the detection of pathogenic microbial parasites containing glycosidases. Copyright © 2014. Published by Elsevier Inc.

Dimension-controlled assemblies of anion-responsive π-electronic systems bearing aryl substituents with fan-shaped geometries.

PubMed

Lakshmi, Vellanki; Haketa, Yohei; Yamakado, Ryohei; Yasuda, Nobuhiro; Maeda, Hiromitsu

2017-03-30

Pyrrole-4-aryl-substituted dipyrrolyldiketone BF 2 complexes as anion-responsive π-electronic molecules were synthesized via a 3,5-dimethylpyrrole precursor. Mesophases were observed in derivatives that possessed long alkyl chains on the pyrrole-4-aryl groups along with their anion complexes as ion-pairing assemblies in combination with appropriate cations.

Asymmetric Direct 1,2-Addition of Aryl Grignard Reagents to Aryl Alkyl Ketones.

PubMed

Osakama, Kazuki; Nakajima, Makoto

2016-01-15

The enantioselective addition of Grignard reagents to ketones was promoted by a BINOL derivative bearing alkyl chains at the 3,3'-positions. This is the first asymmetric direct aryl Grignard addition to ketones reported to date. A variety of tertiary diaryl alcohols could be obtained in high yields and enantioselectivities without using any other metal source.

Asymmetric Aryl Polyhedral Oligomeric SilSesquioxanes (ArPOSS) with Enhanced Solubility (Preprint)

DTIC Science & Technology

2011-03-23

by reaction of an aryl Grignard or lithium reagent with SiCl4 under reaction conditions s imilar to those previously reported [22]. The aryl...cooling to room temperature, this Grignard reagent w as added via canula to a SiCl 4 (25.1 g, 0.148 m ol) THF (70 mL) solution and stirred overnight

Asymmetric synthesis of 5-arylcyclohexenones by rhodium(I)-catalyzed conjugate arylation of racemic 5-(trimethylsilyl)cyclohexenone with arylboronic acids.

PubMed

Chen, Qian; Kuriyama, Masami; Soeta, Takahiro; Hao, Xinyu; Yamada, Ken-ichi; Tomioka, Kiyoshi

2005-09-29

[reaction: see text] A catalytic asymmetric conjugate arylation of racemic 5-(trimethylsilyl)cyclohex-2-enone with arylboronic acids was catalyzed by 3 mol % chiral amidophosphane- or BINAP-Rh(I) in dioxane-water (10:1) to afford trans- and cis-3-aryl-5-(trimethylsilyl)cyclohexanones in high enantioselectivity. Dehydrosilylation of the product mixture with cupric chloride in DMF gave 5-arylcyclohex-2-enones with up to 93% ee in good yield. Enantiofacial selectivity with chiral phosphane-Rh(I) exceeds the trans-diastereoselectivity that is maintained in the achiral or racemic phosphane-Rh(I)-catalyzed conjugate arylation of 5-(trimethylsilyl)cyclohexenone.

Copper-Mediated Fluorination of Arylboronate Esters. Identification of a Copper(III) Fluoride Complex

PubMed Central

Fier, Patrick S.; Luo, Jingwei; Hartwig, John F.

2013-01-01

A method for the direct conversion of arylboronate esters to aryl fluorides under mild conditions with readily available reagents is reported. Tandem reactions have also been developed for the fluorination of arenes and aryl bromides through aryl-boronate ester intermediates. Mechanistic studies suggest that this fluorination reaction occurs through facile oxidation of Cu(I) to Cu(III) followed by rate-limiting transmetallation of a bound arylboronate to Cu(III). Fast C-F reductive elimination is proposed to occur from an aryl-copper(III)-fluoride complex. Cu(III) intermediates have been generated independently and identified by NMR spectroscopy and ESI-MS. PMID:23384209

Aryl-O reductive elimination from reaction of well-defined aryl-Cu(III) species with phenolates: the importance of ligand reactivity.

PubMed

Casitas, Alicia; Ioannidis, Nikolaos; Mitrikas, George; Costas, Miquel; Ribas, Xavi

2011-09-21

Well-defined aryl-Cu(III) species undergo rapid reductive elimination upon reaction with phenolates (PhO(-)), to form aryl-OPh cross-coupling products. Kinetic studies show that the reaction follows a different mechanistic pathway compared to the reaction with phenols. The pH active cyclized pincer-like ligand undergoes an initial amine deprotonation that triggers a faster reactivity at room temperature. A mechanistic proposal for the enhanced reactivity and the role of EPR-detected Cu(II) species will be discussed in detail. This journal is © The Royal Society of Chemistry 2011

Polymerization initated at sidewalls of carbon nanotubes

NASA Technical Reports Server (NTRS)

Tour, James M. (Inventor); Hudson, Jared L. (Inventor); Krishnamoorti, Ramanan (Inventor); Yurekli, Koray (Inventor); Mitchell, Cynthia A. (Inventor)

2011-01-01

The present invention is directed to aryl halide (such as aryl bromide) functionalized carbon nanotubes that can be utilized in anionic polymerization processes to form polymer-carbon nanotube materials with improved dispersion ability in polymer matrices. In this process the aryl halide is reacted with an alkyllithium species or is reacted with a metal to replace the aryl-bromine bond with an aryl-lithium or aryl-metal bond, respectively. It has further been discovered that other functionalized carbon nanotubes, after deprotonation with a deprotonation agent, can similarly be utilized in anionic polymerization processes to form polymer-carbon nanotube materials. Additionally or alternatively, a ring opening polymerization process can be performed. The resultant materials can be used by themselves due to their enhanced strength and reinforcement ability when compared to their unbound polymer analogs. Additionally, these materials can also be blended with pre-formed polymers to establish compatibility and enhanced dispersion of nanotubes in otherwise hard to disperse matrices resulting in significantly improved material properties. The resultant polymer-carbon nanotube materials can also be used in drug delivery processes due to their improved dispersion ability and biodegradability, and can also be used for scaffolding to promote cellular growth of tissue.

Expedient synthesis of C-aryl carbohydrates by consecutive biocatalytic benzoin and aldol reactions.

PubMed

Hernández, Karel; Parella, Teodor; Joglar, Jesús; Bujons, Jordi; Pohl, Martina; Clapés, Pere

2015-02-16

The introduction of aromatic residues connected by a C-C bond into the non-reducing end of carbohydrates is highly significant for the development of innovative structures with improved binding affinity and selectivity (e.g., C-aril-sLex). In this work, an expedient asymmetric "de novo" synthetic route to new aryl carbohydrate derivatives based on two sequential stereoselectively biocatalytic carboligation reactions is presented. First, the benzoin reaction of aromatic aldehydes to dimethoxyacetaldehyde is conducted, catalyzed by benzaldehyde lyase from Pseudomonas fluorescens biovar I. Then, the α-hydroxyketones formed are reduced by using NaBH4 yielding the anti diol. After acetal hydrolysis, the aldol addition of dihydroxyacetone, hydroxyacetone, or glycolaldehyde catalyzed by the stereocomplementary D-fructose-6-phosphate aldolase and L-rhamnulose-1-phosphate aldolase is performed. Both aldolases accept unphosphorylated donor substrates, avoiding the need of handling the phosphate group that the dihydroxyacetone phosphate-dependent aldolases require. In this way, 6-C-aryl-L-sorbose, 6-C-aryl-L-fructose, 6-C-aryl-L-tagatose, and 5-C-aryl-L-xylose derivatives are prepared by using this methodology. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Organic amine catalytic organosolv pretreatment of corn stover for enzymatic saccharification and high-quality lignin.

PubMed

Tang, Chenglun; Shan, Junqiang; Chen, Yanjun; Zhong, Lingxia; Shen, Tao; Zhu, Chenjie; Ying, Hanjie

2017-05-01

A novel and efficient organic amine and organosolv synergetic pretreatment method was developed to overcome the recalcitrance of lignocellulose to produce fermentable sugars and high-quality salt-free lignin. After optimization of the process parameters, a delignification of 81.7% and total sugar yield of 83.2% (87.1% glucose, 75.4% xylose) could be obtained using n-propylamine (10mmol/g, biomass) as a catalyst and aqueous ethanol (60%, v/v) as a solvent. The susceptibility of the substrates to enzymatic digestibility was explained by their physical and chemical characteristics. The physical structure of extracted lignin showed higher β-aryl ether bonds content and functionalities, offering the potential for further downstream upgrading. The role of organic amine catalyst and a synergistic mechanism is proposed for the present system. Copyright © 2017 Elsevier Ltd. All rights reserved.

Development of polymeric palladium-nanoparticle membrane-installed microflow devices and their application in hydrodehalogenation.

PubMed

Yamada, Yoichi M A; Watanabe, Toshihiro; Ohno, Aya; Uozumi, Yasuhiro

2012-02-13

We have developed a variety of polymeric palladium-nanoparticle membrane-installed microflow devices. Three types of polymers were convoluted with palladium salts under laminar flow conditions in a microflow reactor to form polymeric palladium membranes at the laminar flow interface. These membranes were reduced with aqueous sodium formate or heat to create microflow devices that contain polymeric palladium-nanoparticle membranes. These microflow devices achieved instantaneous hydrodehalogenation of aryl chlorides, bromides, iodides, and triflates by 10-1000 ppm within a residence time of 2-8 s at 50-90 °C by using safe, nonexplosive, aqueous sodium formate to quantitatively afford the corresponding hydrodehalogenated products. Polychlorinated biphenyl (10-1000 ppm) and polybrominated biphenyl (1000 ppm) were completely decomposed under similar conditions, yielding biphenyl as a fungicidal compound. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Anti-cancer agents based on N-acyl-2, 3-dihydro-1H-pyrrolo[2,3-b] quinoline derivatives and a method of making

DOEpatents

Gakh, Andrei; Krasavin, Mikhail; Karapetian, Ruben; Rufanov, Konstantin A; Konstantinov, Igor; Godovykh, Elena; Soldatkina, Olga; Sosnov, Andrey V

2013-04-16

The present disclosure relates to novel compounds that can be used as anti-cancer agents in the prostate cancer therapy. In particular, the invention relates to N-acyl derivatives of 2,3-dihydro-1H-pyrrolo[2,3-b]quinolines having the structural Formula (I), ##STR00001## stereoisomers, tautomers, racemics, prodrugs, metabolites thereof, or pharmaceutically acceptable salt and/or solvate thereof. The meaning of R1 is independently selected from H; C1-C6 Alkyl, cyclo-Alkyl or iso-Alkyl substituents; R2 is selected from C1-C6 Alkyl, cyclo-Alkyl or iso-Alkyl; substituted or non-substituted, fused or non-fused to substituted or non-substituted aromatic ring, aryl or heteroaryl groups. The invention also relates to methods for preparing said compounds, and to pharmaceutical compositions comprising said compounds.

Anticancer activity and anti-inflammatory studies of 5-aryl-1,4-benzodiazepine derivatives.

PubMed

Sandra, Cortez-Maya; Eduardo, Cortes Cortes; Simon, Hernandez-Ortega; Teresa, Ramirez Apan; Antonio, Nieto Camacho; Lijanova, Irina V; Marcos, Martinez-Garcia

2012-07-01

A series of 5-aryl-1,4-benzodiazepines with chloro- or fluoro-substituents in the second ring have been synthesized and their anti-inflammatory, myeloperoxidase and anticancer properties studied. The synthesized compounds showed potential anti-inflammatory and anticancer activities, which were enhanced in the presence of a chloro-substituent in the second ring of the 5-aryl-1,4- benzodiazepine.

Methoxy-Directed Aryl-to-Aryl 1,3-Rhodium Migration

PubMed Central

Zhang, Jing; Liu, Jun-Feng; Ugrinov, Angel; Pillai, Anthony F. X.; Sun, Zhong-Ming; Zhao, Pinjing

2015-01-01

Through-space metal/hydrogen shift is an important strategy for transition metal-catalyzed C-H bond activation. Here we describe the synthesis and characterization of a Rh(I) 2,6-dimethoxybenzoate complex that underwent stoichiometric rearrangement via a highly unusual 1,3- rhodium migration. This aryl-to-aryl 1,3-Rh/H shift was also demonstrated in a Rh(I)-catalyzed decarboxylative conjugate addition to form a C-C bond at a meta position instead of the ipso-carboxyl position. A deuterium-labeling study under the conditions of Rh(I)-catalyzed protodecarboxylation revealed the involvement of an ortho-methoxy group in a multi-step pathway of consecutive sp3 and sp2 C-H bond activations. PMID:24171626

Synthesis of aryl thioethers through the N-chlorosuccinimide-promoted cross-coupling reaction of thiols with Grignard reagents.

PubMed

Cheng, Jun-Hao; Ramesh, Chintakunta; Kao, Hsin-Lun; Wang, Yu-Jen; Chan, Chien-Ching; Lee, Chin-Fa

2012-11-16

A convenient one-pot approach for the synthesis of aryl sulfides through the coupling of thiols with Grignard reagents in the presence of N-chlorosuccinimide is described. The sulfenylchlorides were formed when thiols were treated with N-chlorosuccinimide, and the resulting sulfenylchlorides were then directly reacted with Grignard reagents to provide aryl sulfides in good to excellent yields under mild reaction conditions. Functional groups including ester, fluoro, and chloro are tolerated by the reaction conditions employed. It is important to note that this method has a short reaction time (30 min in total) and represents an alternative approach for the synthesis of aryl sulfides over the existing protocols.

Stabilizing and destabilizing effects of phenylalanine --> F5-phenylalanine mutations on the folding of a small protein.

PubMed

Woll, Matthew G; Hadley, Erik B; Mecozzi, Sandro; Gellman, Samuel H

2006-12-20

We report a systematic evaluation of phenylalanine-to-pentafluorophenylalanine (Phe --> F5-Phe) mutants for the 35-residue chicken villin headpiece subdomain (c-VHP), the hydrophobic core of which features a cluster of three Phe side chains (residues 6, 10, and 17). Phe --> F5-Phe mutations are interesting because aryl-perfluoroaryl interactions of optimal geometry are intrinsically more favorable than aryl-aryl interactions and because perfluoroaryl units are more hydrophobic than are analogous aryl units. One mutant, Phe-10 --> F5-Phe, provides enhanced tertiary structural stability relative to the native sequence. The other six mutants analyzed caused a decrease in stability.

Design, Synthesis, and Validation of an Effective, Reusable Silicon-Based Transfer Agent for Room-Temperature Pd-Catalyzed Cross-Coupling Reactions of Aryl and Heteroaryl Chlorides with Readily Available Aryl Lithium Reagents

PubMed Central

Martinez-Solorio, Dionicio; Melillo, Bruno; Sanchez, Luis; Liang, Yong; Lam, Erwin; Houk, K. N.; Smith, Amos B.

2016-01-01

A reusable silicon-based transfer agent (1) has been designed, synthesized, and validated for effective room-temperature palladium-catalyzed cross-coupling reactions (CCRs) of aryl and heteroaryl chlorides with readily accessible aryl lithium reagents. The crystalline, bench-stable siloxane transfer agent (1) is easily prepared via a one-step protocol. Importantly, this “green” CCR protocol circumvents prefunctionalization, isolation of organometallic cross-coupling partners, and/or stoichiometric waste aside from LiCl. DFT calculations support a σ-bond metathesis mechanism during transmetalation and lead to insights on the importance of the CF3 groups. PMID:26835838

Highly Reactive, General and Long-Lived Catalysts for Palladium-Catalyzed Amination of Heteroaryl and Aryl Chlorides, Bromides and Iodides: Scope and Structure-Activity Relationships

PubMed Central

Shen, Qilong; Ogata, Tokutaro; Hartwig, John F.

2010-01-01

We describe a systematic study of the scope and relationship between ligand structure and activity for a highly efficient and selective class of catalysts for the amination of heteroaryl and aryl chlorides, bromides and iodides containing sterically hindered chelating alkylphosphines. In the presence of this catalyst, aryl and heteroaryl chlorides, bromides and iodides react with many primary amines in high yields with part-per-million quantities of palladium precursor and ligand. Many reactions of primary amines with both heteroaryl and aryl chlorides, bromides and iodides occur to completion with 0.0005-0.05 mol % catalysts. A comparison of the reactivity of this catalyst for coupling of primary amines at these loadings is made with catalysts generated from hindered monophosphines and carbenes, and these data illustrate the benefits of chelation. Thus, these complexes constitute a fourth-generation catalyst for the amination of aryl halides, whose activity complements catalysts based on monophosphines and carbenes. PMID:18444639

Palladium-catalyzed one-pot three- or four-component coupling of aryl iodides, alkynes, and amines through C-N bond cleavage: efficient synthesis of indole derivatives.

PubMed

Hao, Wei; Geng, Weizhi; Zhang, Wen-Xiong; Xi, Zhenfeng

2014-02-24

An efficient synthesis of N-substituted indole derivatives was realized by combining the Pd-catalyzed one-pot multicomponent coupling approach with cleavage of the C(sp(3))-N bonds. Three or four components of aryl iodides, alkynes, and amines were involved in this coupling process. The cyclopentadiene-phosphine ligand showed high efficiency. A variety of aryl iodides, including cyclic and acyclic tertiary amino aryl iodides, and substituted 1-bromo-2-iodobenzene derivatives could be used. Both symmetric and unsymmetric alkynes substituted with alkyl, aryl, or trimethylsilyl groups could be applied. Cyclic secondary amines such as piperidine, morpholine, 4-methylpiperidine, 1-methylpiperazine, 2-methylpiperidine, and acyclic amines including secondary and primary amines all showed good reactivity. Further application of the resulting indole derivatives was demonstrated by the synthesis of benzosilolo[2,3-b]indole. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Covalent Modification of Highly Ordered Pyrolytic Graphite with a Stable Organic Free Radical by Using Diazonium Chemistry.

PubMed

Seber, Gonca; Rudnev, Alexander V; Droghetti, Andrea; Rungger, Ivan; Veciana, Jaume; Mas-Torrent, Marta; Rovira, Concepció; Crivillers, Núria

2017-01-26

A novel, persistent, electrochemically active perchlorinated triphenylmethyl (PTM) radical with a diazonium functionality has been covalently attached to highly ordered pyrolytic graphite (HOPG) by electrografting in a single-step process. Electrochemical scanning tunneling microscopy (EC-STM) and Raman spectroscopy measurements revealed that PTM molecules had a higher tendency to covalently react at the HOPG step edges. The cross-section profiles from EC-STM images showed that there was current enhancement at the functionalized areas, which could be explained by redox-mediated electron tunneling through surface-confined redox-active molecules. Cyclic voltammetry clearly demonstrated that the intrinsic properties of the organic radical were preserved upon grafting and DFT calculations also revealed that the magnetic character of the PTM radical was preserved. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Modification of Silk Fibroin Using Diazonium Coupling Chemistry and the Effects on hMSC Proliferation and Differentiation

PubMed Central

Murphy, Amanda R.; John, Peter St.; Kaplan, David L.

2009-01-01

A simple chemical modification method using diazonium coupling chemistry was developed to tailor the structure and hydrophilicity of silk fibroin protein. The extent of modification using several aniline derivatives was characterized using UV/vis and 1H NMR spectroscopy, and the resulting protein structure was analyzed with ATR-FTIR spectroscopy. Introduction of hydrophobic functional groups facilitated rapid conversion of the protein from a random coil to a β-sheet structure, while addition of hydrophilic groups inhibited this process. hMSCs were grown on these modified silks to assess the biocompatibility of these materials. The hydrophilicity of the silk derivatives was found to affect the growth rate and morphology, but hMSCs were able to attach, proliferate and differentiate into an osteogenic lineage on all of the silk derivatives. PMID:18417206

Diazonium-based impedimetric aptasensor for the rapid label-free detection of Salmonella typhimurium in food sample.

PubMed

Bagheryan, Zahra; Raoof, Jahan-Bakhsh; Golabi, Mohsen; Turner, Anthony P F; Beni, Valerio

2016-06-15

Fast and accurate detection of microorganisms is of key importance in clinical analysis and in food and water quality monitoring. Salmonella typhimurium is responsible for about a third of all cases of foodborne diseases and consequently, its fast detection is of great importance for ensuring the safety of foodstuffs. We report the development of a label-free impedimetric aptamer-based biosensor for S. typhimurium detection. The aptamer biosensor was fabricated by grafting a diazonium-supporting layer onto screen-printed carbon electrodes (SPEs), via electrochemical or chemical approaches, followed by chemical immobilisation of aminated-aptamer. FTIR-ATR, contact angle and electrochemical measurements were used to monitor the fabrication process. Results showed that electrochemical immobilisation of the diazonium-grafting layer allowed the formation of a denser aptamer layer, which resulted in higher sensitivity. The developed aptamer-biosensor responded linearly, on a logarithm scale, over the concentration range 1 × 10(1) to 1 × 10(8)CFU mL(-1), with a limit of quantification (LOQ) of 1 × 10(1) CFU mL(-1) and a limit of detection (LOD) of 6 CFU mL(-1). Selectivity studies showed that the aptamer biosensor could discriminate S. typhimurium from 6 other model bacteria strains. Finally, recovery studies demonstrated its suitability for the detection of S. typhimurium in spiked (1 × 10(2), 1 × 10(4) and 1 × 10(6) CFU mL(-1)) apple juice samples. Copyright © 2016 Elsevier B.V. All rights reserved.

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

A beta-keto ester as a novel, efficient, and versatile ligand for copper(I)-catalyzed C-N, C-O, and C-S coupling reactions.

PubMed

Lv, Xin; Bao, Weiliang

2007-05-11

Employing ethyl 2-oxocyclohexanecarboxylate as a novel, efficient, and versatile ligand, the copper-catalyzed coupling reactions of various N/O/S nucleophilic reagents with aryl halides could be successfully carried out under mild conditions. A variety of products including N-arylamides, N-arylimidazoles, aryl ethers, and aryl thioethers were synthesized in good to excellent yields.

Towards a fragment-based approach in gelator design: halogen effects leading to thixotropic, mouldable and self-healing systems in aryl-triazolyl amino acid-based gelators!

PubMed

Srivastava, Bhartendu K; Manheri, Muraleedharan K

2017-04-18

A simple replacement of a H atom by Br transformed non-gelating aryl triazolyl amino acid benzyl ester into a versatile gelator, which formed shape-persistent, self-healing and mouldable gels. The 'bromo-aryl benzyl ester' fragment was then transplanted into another framework, which resulted in similar solvent preference and gelation efficiency.

Use of Aryl Chlorides as Electrophiles in Pd-Catalyzed Alkene Difunctionalization Reactions

PubMed Central

Rosen, Brandon R.; Ney, Joshua E.; Wolfe, John P.

2010-01-01

The development of conditions that allow use of inexpensive aryl chlorides as electrophiles in Pd-catalyzed alkene carboamination and carboetherification reactions is described. A catalyst composed of Pd(OAc)2 and S-Phos minimizes N-arylation of the substrate and prevents formation of mixtures of regioisomeric products. A number of heterocycles, including pyrrolidines, isoxazolidines, tetrahydrofurans, and pyrazolidines, are efficiently generated with this method. PMID:20297834

Synthesis Of [2h, 13c]M [2h2m 13c], And [2h3,, 13c] Methyl Aryl Sulfones And Sulfoxides

DOEpatents

Martinez, Rodolfo A.; Alvarez, Marc A.; Silks, III, Louis A.; Unkefer, Clifford J.; Schmidt, Jurgen G.

2004-07-20

The present invention is directed to labeled compounds, [.sup.2 H.sub.1, .sup.13 C], [.sup.2 H.sub.2, .sup.13 C] and [.sup.2 H.sub.3, .sup.13 C]methyl aryl sulfones and [.sup.2 H.sub.1, .sup.13 C], [.sup.2 H.sub.2, .sup.13 C] and [.sup.2 H.sub.3, .sup.13 C]methyl aryl sulfoxides, wherein the .sup.13 C methyl group attached to the sulfur of the sulfone or sulfoxide includes exactly one, two or three deuterium atoms and the aryl group is selected from the group consisting of 1-naphthyl, substituted 1-naphthyl, 2-naphthyl, substituted 2-naphthyl, and phenyl groups with the structure: ##STR1## wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4 and R.sub.5 are each independently, hydrogen, a C.sub.1 -C.sub.4 lower alkyl, a halogen, an amino group from the group consisting of NH.sub.2, NHR and NRR' where R and R' are each a C.sub.1 -C.sub.4 lower alkyl, a phenyl, or an alkoxy group. The present invention is also directed to processes of preparing methyl aryl sulfones and methyl aryl sulfoxides.

Highly enantioselective arylation of aldehydes and ketones using AlArEt(2)(THF) as aryl sources.

PubMed

Zhou, Shuangliu; Wu, Kuo-Hui; Chen, Chien-An; Gau, Han-Mou

2009-05-01

A series of AlArEt(2)(THF) (Ar = Ph (1a), 4-MeC(6)H(4) (1b), 4-MeOC(6)H(4) (1c), 4-Me(3)SiC(6)H(4) (1d), 2-naphthyl (1e)) were synthesized from reactions of AlEt(2)Br(THF) with ArMgBr. In CDCl(3) solution, the (1)H NMR spectra showed that AlArEt(2)(THF) compounds exist as a mixture of four species of formulas of AlAr(x)Et(3-x) (THF) (x = 0, 1, 2, or 3). AlArEt(2)(THF) compounds were found to be superior and atom-economic reagents for asymmetric aryl additions to organic carbonyls. Aryl additions of AlArEt(2)(THF) to aldehydes catalyzed by the titanium(IV) complex of (R)-H(8)-BINOL were efficient with a short reaction time of 1 h, affording aryl addition products as exclusive or main products in high yields and excellent enantioselectivities of up to 98% ee. Although ethyl additions to aldehydes occurred in minor extent, this study demonstrates that increasing the amount of AlArEt(2)(THF) from 1.2 to 1.4 or to 1.6 equiv significantly improved the aryl addition products of up to >99%. On the other hand, asymmetric arylations of AlArEt(2)(THF) to ketones employing a titanium(IV) catalyst of (S)-BINOL produced optically active tertiary alcohols exclusively in excellent enantioselectivities of up to 94% ee.

Stimulation of aryl metabolite production in the basidiomycete Bjerkandera sp. strain BOS55 with biosynthetic precursors and lignin degradation products.

PubMed Central

Mester, T; Swarts, H J; Romero i Sole, S; de Bont, J A; Field, J A

1997-01-01

Aryl metabolites are known to have an important role in the ligninolytic system of white rot fungi. The addition of known precursors and aromatic acids representing lignin degradation products stimulated the production of aryl metabolites (veratryl alcohol, veratraldehyde, p-anisaldehyde, and 3-chloro-p-anisaldehyde) in the white rot fungus Bjerkandera sp. strain BOS55. The presence of manganese (Mn) is known to inhibit the biosynthesis of veratryl alcohol (T. Mester, E. de Jong, and J.A. Field, Appl. Environ. Microbiol. 61:1881-1887, 1995). A new finding of this study was that the production of the other aryl metabolites, p-anisaldehyde and 3-chloro-p-anisaldehyde, was also inhibited by Mn. We attempted to bypass the Mn-inhibited step in the biosynthesis of aryl metabolites by the addition of known and suspected precursors. Most of these compounds were not able to bypass the inhibiting effect of Mn. Only the fully methylated precursors (veratrate, p-anisate, and 3-chloro-p-anisate) provided similar concentrations of aryl metabolites in the presence and absence of Mn, indicating that Mn does not influence the reduction of the benzylic acid group. The addition of deuterated benzoate and 4-hydroxybenzoate resulted in the formation of deuterated aryl metabolites, indicating that these aromatic acids entered into the biosynthetic pathway and were common intermediates to all aryl metabolites. Only deuterated chlorinated anisyl metabolites were produced when the cultures were supplemented with deuterated 3-chloro-4-hydroxybenzoate. This observation combined with the fact that 3-chloro-4-hydroxybenzoate is a natural product of Bjerkandera spp. (H. J. Swarts, F. J. M. Verhagen, J. A. Field, and J. B. P. A. Wijnberg, Phytochemistry 42:1699-1701, 1996) suggest that it is a possible intermediate in chlorinated anisyl metabolite biosynthesis. PMID:9143129

Cloning, expression and characterization of an aryl-alcohol dehydrogenase from the white-rot fungus Phanerochaete chrysosporium strain BKM-F-1767

PubMed Central

2012-01-01

Background The white-rot fungus Phanerochaete chrysosporium is among the small group of fungi that can degrade lignin to carbon dioxide while leaving the crystalline cellulose untouched. The efficient lignin oxidation system of this fungus requires cyclic redox reactions involving the reduction of aryl-aldehydes to the corresponding alcohols by aryl-alcohol dehydrogenase. However, the biochemical properties of this enzyme have not been extensively studied. These are of most interest for the design of metabolic engineering/synthetic biology strategies in the field of biotechnological applications of this enzyme. Results We report here the cloning of an aryl-alcohol dehydrogenase cDNA from the white-rot fungus Phanerochaete chrysosporium, its expression in Escherichia coli and the biochemical characterization of the encoded GST and His6 tagged protein. The purified recombinant enzyme showed optimal activity at 37°C and at pH 6.4 for the reduction of aryl- and linear aldehydes with NADPH as coenzyme. NADH could also be the electron donor, while having a higher Km (220 μM) compared to that of NADPH (39 μM). The purified recombinant enzyme was found to be active in the reduction of more than 20 different aryl- and linear aldehydes showing highest specificity for mono- and dimethoxylated Benzaldehyde at positions 3, 4, 3,4 and 3,5. The enzyme was also capable of oxidizing aryl-alcohols with NADP + at 30°C and an optimum pH of 10.3 but with 15 to 100-fold lower catalytic efficiency than for the reduction reaction. Conclusions In this work, we have characterized the biochemical properties of an aryl-alcohol dehydrogenase from the white-rot fungus Phanerochaete chrysosporium. We show that this enzyme functions in the reductive sense under physiological conditions and that it displays relatively large substrate specificity with highest activity towards the natural compound Veratraldehyde. PMID:22742413

Copper complexes of anionic nitrogen ligands in the amidation and imidation of aryl halides.

PubMed

Tye, Jesse W; Weng, Zhiqiang; Johns, Adam M; Incarvito, Christopher D; Hartwig, John F

2008-07-30

Copper(I) imidate and amidate complexes of chelating N,N-donor ligands, which are proposed intermediates in copper-catalyzed amidations of aryl halides, have been synthesized and characterized by X-ray diffraction and detailed solution-phase methods. In some cases, the complexes adopt neutral, three-coordinate trigonal planar structures in the solid state, but in other cases they adopt an ionic form consisting of an L 2Cu (+) cation and a CuX 2 (-) anion. A tetraalkylammonium salt of the CuX 2 (-) anion in which X = phthalimidate was also isolated. Conductivity measurements and (1)H NMR spectra of mixtures of two complexes all indicate that the complexes exist predominantly in the ionic form in DMSO and DMF solutions. One complex was sufficiently soluble for conductance measurements in less polar solvents and was shown to adopt some degree of the ionic form in THF and predominantly the neutral form in benzene. The complexes containing dative nitrogen ligands reacted with iodoarenes and bromoarenes to form products from C-N coupling, but the ammonium salt of [Cu(phth) 2] (-) did not. Similar selectivities for stoichiometric and catalytic reactions with two different iodoarenes and faster rates for the stoichiometric reactions implied that the isolated amidate and imidate complexes are intermediates in the reactions of amides and imides with haloarenes catalyzed by copper complexes containing dative N,N ligands. These amidates and imidates reacted much more slowly with chloroarenes, including chloroarenes that possess more favorable reduction potentials than some bromoarenes and that are known to undergo fast dissociation of chloride from the chloroarene radical anion. The reaction of o-(allyloxy)iodobenzene with [(phen) 2Cu][Cu(pyrr) 2] results in formation of the C-N coupled product in high yield and no detectable amount of the 3-methyl-2,3-dihydrobenzofuran or 3-methylene-2,3-dihydrobenzofuran products that would be expected from a reaction that generated free radicals. These data and computed reaction barriers argue against mechanisms in which the haloarene reacts with a two-coordinate anionic copper species and mechanisms that start with electron transfer to generate a free iodoarene radical anion. Instead, these data are more consistent with mechanisms involving cleavage of the carbon-halogen bond within the coordination sphere of the metal.

Identification and characterization of 4-aryl-3,4-dihydropyrimidin-2(1H)-ones as inhibitors of the fatty acid transporter FATP4.

PubMed

Blackburn, Christopher; Guan, Bing; Brown, James; Cullis, Courtney; Condon, Stephen M; Jenkins, Tracy J; Peluso, Stephane; Ye, Yingchun; Gimeno, Ruth E; Punreddy, Sandhya; Sun, Ying; Wu, Hui; Hubbard, Brian; Kaushik, Virendar; Tummino, Peter; Sanchetti, Praveen; Yu Sun, Dong; Daniels, Tom; Tozzo, Effie; Balani, Suresh K; Raman, Prakash

2006-07-01

Several potent, cell permeable 4-aryl-dihydropyrimidinones have been identified as inhibitors of FATP4. Lipophilic ester substituents at the 5-position and substitution at the para-position (optimal groups being -NO(2) and CF(3)) of the 4-aryl group led to active compounds. In two cases racemates were resolved and the S enantiomers shown to have higher potencies.

Transnitrilation from Dimethylmalononitrile to Aryl Grignard and Lithium Reagents: A Practical Method for Aryl Nitrile Synthesis.

PubMed

Reeves, Jonathan T; Malapit, Christian A; Buono, Frederic G; Sidhu, Kanwar P; Marsini, Maurice A; Sader, C Avery; Fandrick, Keith R; Busacca, Carl A; Senanayake, Chris H

2015-07-29

An electrophilic cyanation of aryl Grignard or lithium reagents, generated in situ from the corresponding aryl bromides or iodides, by a transnitrilation with dimethylmalononitrile (DMMN) was developed. DMMN is a commercially available, bench-stable solid. The transnitrilation with DMMN avoids the use of toxic reagents and transition metals and occurs under mild reaction conditions, even for extremely sterically hindered substrates. The transnitrilation of aryllithium species generated by directed ortho-lithiation enabled a net C-H cyanation. The intermediacy of a Thorpe-type imine adduct in the reaction was supported by isolation of the corresponding ketone from the quenched reaction. Computational studies supported the energetic favorability of retro-Thorpe fragmentation of the imine adduct.

Lanthanum tricyanide-catalyzed acyl silane-ketone benzoin additions and kinetic resolution of resultant alpha-silyloxyketones.

PubMed

Tarr, James C; Johnson, Jeffrey S

2010-05-21

We report the full account of our efforts on the lanthanum tricyanide-catalyzed acyl silane-ketone benzoin reaction. The reaction exhibits a wide scope in both acyl silane (aryl, alkyl) and ketone (aryl-alkyl, alkyl-alkyl, aryl-aryl, alkenyl-alkyl, alkynyl-alkyl) coupling partners. The diastereoselectivity of the reaction has been examined in both cyclic and acyclic systems. Cyclohexanones give products arising from equatorial attack by the acyl silane. The diastereoselectivity of acyl silane addition to acyclic alpha-hydroxy ketones can be controlled by varying the protecting group to obtain either Felkin-Ahn or chelation control. The resultant alpha-silyloxyketone products can be resolved with selectivity factors from 10 to 15 by subjecting racemic ketone benzoin products to CBS reduction.

Rhodium(III)-catalyzed [3+2] annulation of 5-aryl-2,3-dihydro-1H-pyrroles with internal alkynes through C(sp²)-H/alkene functionalization.

PubMed

Zhou, Ming-Bo; Pi, Rui; Hu, Ming; Yang, Yuan; Song, Ren-Jie; Xia, Yuanzhi; Li, Jin-Heng

2014-10-13

This study describes a new rhodium(III)-catalyzed [3+2] annulation of 5-aryl-2,3-dihydro-1H-pyrroles with internal alkynes using a Cu(OAc)2 oxidant for building a spirocyclic ring system, which includes the functionalization of an aryl C(sp(2))-H bond and addition/protonolysis of an alkene C=C bond. This method is applicable to a wide range of 5-aryl-2,3-dihydro-1H-pyrroles and internal alkynes, and results in the assembly of the spiro[indene-1,2'-pyrrolidine] architectures in good yields with excellent regioselectivities. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A new aptamer/graphene interdigitated gold electrode piezoelectric sensor for rapid and specific detection of Staphylococcus aureus.

PubMed

Lian, Yan; He, Fengjiao; Wang, Huan; Tong, Feifei

2015-03-15

A novel aptamer/graphene interdigitated gold electrode piezoelectric sensor was developed for the rapid and specific detection of Staphylococcus aureus (S. aureus) by employing S. aureus aptamer as a biological recognition element. 4-Mercaptobenzene-diazonium tetrafluoroborate (MBDT) salt was used as a molecular cross-linking agent to chemically bind graphene to interdigital gold electrodes (IDE) that are connected to a series electrode piezoelectric quartz crystal (SPQC). S. aureus aptamers were assembly immobilized onto graphene via the π-π stacking of DNA bases. Due to the specific binding between S. aureus and aptamer, when S. aureus is present, the DNA bases interacted with the aptamer, thereby dropping the aptamer from the surface of the graphene. The electric parameters of the electrode surface was changed and resulted in the change of oscillator frequency of the SPQC. This detection was completed within 60min. The constructed sensor demonstrated a linear relationship between resonance frequency shifts with bacterial concentrations ranging from 4.1×10(1)-4.1×10(5)cfu/mL with a detection limit of 41cfu/mL. The developed strategy can detect S. aureus rapidly and specifically for clinical diagnosis and food testing. Copyright © 2014 Elsevier B.V. All rights reserved.

A novel electrochemical aptamer-antibody sandwich assay for lysozyme detection.

PubMed

Ocaña, Cristina; Hayat, Akhtar; Mishra, Rupesh; Vasilescu, Alina; del Valle, Manel; Marty, Jean-Louis

2015-06-21

In this paper, we have reported a novel electrochemical aptamer-antibody based sandwich biosensor for the detection of lysozyme. In the sensing strategy, an anti-lysozyme aptamer was immobilized onto the carbon electrode surface by covalent binding via diazonium salt chemistry. After incubating with a target protein (lysozyme), a biotinylated antibody was used to complete the sandwich format. The subsequent additions of avidin-alkaline phosphatase as an enzyme label, and a 1-naphthyl phosphate substrate (1-NPP) allowed us to determine the concentration of lysozyme (Lys) via Differential Pulse Voltammetry (DPV) of the generated enzyme reaction product, 1-naphthol. Using this strategy, a wide detection range from 5 fM to 5 nM was obtained for a target lysozyme, with a detection limit of 4.3 fM. The control experiments were carried out by using bovine serum albumin (BSA), cytochrome c and casein. The results showed that the proposed biosensor had good specificity, stability and reproducibility for lysozyme analysis. In addition, the biosensor was applied for detecting lysozyme in spiked wine samples, and very good recovery rates were obtained in the range from 95.2 to 102.0% for lysozyme detection. This implies that the proposed sandwich biosensor is a promising analytical tool for the analysis of lysozyme in real samples.

Synthesis and Antimicrobial Evaluation of Some Novel Thiazole, Pyridone, Pyrazole, Chromene, Hydrazone Derivatives Bearing a Biologically Active Sulfonamide Moiety

PubMed Central

Darwish, Elham S.; Abdel Fattah, Azza M.; Attaby, Fawzy A.; Al-Shayea, Oqba N.

2014-01-01

This study aimed for the synthesis of new heterocyclic compounds incorporating sulfamoyl moiety suitable for use as antimicrobial agents via a versatile, readily accessible N-[4-(aminosulfonyl)phenyl]-2-cyanoacetamide (3). The 2-pyridone derivatives were obtained via reaction of cyanoacetamide with acetylacetone or arylidenes malononitrile. Cycloaddition reaction of cyanoacetamide with salicyaldehyde furnished chromene derivatives. Diazotization of 3 with the desired diazonium chloride gave the hydrazone derivatives 13a–e. Also, the reactivity of the hydrazone towards hydrazine hydrate to give Pyrazole derivatives was studied. In addition, treatment of 3 with elemental sulfur and phenyl isothiocyanate or malononitrile furnished thiazole and thiophene derivatives respectively. Reaction of 3 with phenyl isothiocyanate and KOH in DMF afforded the intermediate salt 17 which reacted in situ with 3-(2-bromoacetyl)-2H-chromen-2-one and methyl iodide afforded the thiazole and ketene N,S-acetal derivatives respectively. Finally, reaction of 3 with carbon disulfide and 1,3-dibromopropane afforded the N-[4-(aminosulfonyl) phenyl]-2-cyano-2-(1,3-dithian-2-ylidene)acetamide product 22. All newly synthesized compounds were elucidated by considering the data of both elemental and spectral analysis. The compounds were evaluated for both their in vitro antibacterial and antifungal activities and showed promising results. PMID:24445259

Novel acid mono azo dye compound: Synthesis, characterization, vibrational, optical and theoretical investigations of 2-[(E)-(8-hydroxyquinolin-5-yl)-diazenyl]-4,5-dimethoxybenzoic acid

NASA Astrophysics Data System (ADS)

Saçmacı, Mustafa; Çavuş, Hatice Kanbur; Arı, Hatice; Şahingöz, Recep; Özpozan, Talat

2012-11-01

Novel acid mono azo dye, 2-[(E)-(8-hydroxyquinolin-5yl)-diazenyl]-4,5-dimethoxybenzoic acid (HQD), was synthesized by coupling diazonium salt solution of 2-amino-4,5-dimethoxybenzoic acid (DMA) with 8-hydroxyquinoline (HQ). This dye was characterized by UV-vis, IR & Raman, 1H and 13C NMR spectroscopic techniques and elemental analysis. The normal coordinate analysis of HQD was also performed to assign each band in vibrational spectra. DFT (B3LYP and B3PW91) calculations were employed to optimize the geometry, to interpret NMR spectra, to calculate and to determine the stable tautomeric structure of the compound. Natural Bond Orbital (NBO) analysis was performed to investigate intramolecular interactions. The vibrational spectral data obtained from solid phase IR & Raman spectra were assigned based on the results of the theoretical calculations. UV-vis spectroscopic technique was employed to obtain the optical band gap of HQD. The analysis of the optical absorption data revealed the existence of direct and indirect transitions in the optical band gaps. The optical band gaps of HQD have been found 1.95 and 1.90 eV for direct and indirect transitions, respectively.

N-heterocycle carbene (NHC)-ligated cyclopalladated N,N-dimethylbenzylamine: a highly active, practical and versatile catalyst for the Heck-Mizoroki reaction.

PubMed

Peh, Guang-Rong; Kantchev, Eric Assen B; Zhang, Chi; Ying, Jackie Y

2009-05-21

The wide dissemination of catalytic protocols in academic and industrial laboratories is facilitated by the development of catalysts that are not only highly active but also user-friendly, stable to moisture, air and long term storage and easy to prepare on a large scale. Herein we describe a protocol for the Heck-Mizoroki reaction mediated by cyclopalladated N,N-dimethylbenzylamine (dmba) ligated with a N-heterocyclic carbene, 1,3-bis(mesityl)imidazol-2-ylidene (IMes), that fulfils these criteria. The precatalyst can be synthesized on approximately 100 g scale by a tri-component, sequential, one-pot reaction of N,N-dimethylbenzylamine, PdCl2 and IMes.HCl in refluxing acetonitrile in air in the presence of K2CO3. This single component catalyst is stable to air, moisture and long term storage and can be conveniently dispensed as a stock solution in NMP. It mediates the Heck-Mizoroki reaction of a range of aryl- and heteroaryl bromides in reagent grade NMP at the 0.1-2 mol% range without the need for rigorous anhydrous techniques or a glovebox, and is active even in air. The catalyst is capable of achieving very high levels of catalytic activity (TON of up to 5.22 x 10(5)) for the coupling of a deactivated arylbromide, p-bromoanisole, with tBu acrylate as a benchmark substrate pair. A wide range of aryl bromides, iodides and, for the first time with a NHC-Pd catalyst, a triflate was coupled with diverse acrylate derivatives (nitrile, tert-butyl ester and amides) and styrene derivatives. The use of excess (>2 equiv.) of the aryl bromide and tert-butyl acrylate leads to mixture of tert-butyl beta,beta-diarylacrylate and tert-butyl cinnamate derivatives depending on the substitution pattern of the aryl bromide. Electron rich m- and p-substituted arylbromides give the diarylated products exclusively, whereas electron-poor aryl bromides give predominantly mono-arylated products. For o-substituted aryl bromides, no doubly arylated products could be obtained under any conditions. Overall, the active catalyst (IMes-Pd) shows higher activity with electron-rich aryl halides, a marked difference compared with the more commonly used phosphane-Pd or non-ligated Pd catalysts.

Structure of aryl O -demethylase offers molecular insight into a catalytic tyrosine-dependent mechanism

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kohler, Amanda C.; Mills, Matthew J. L.; Adams, Paul D.

Some strains of soil and marine bacteria have evolved intricate metabolic pathways for using environmentally derived aromatics as a carbon source. Many of these metabolic pathways go through intermediates such as vanillate, 3-O-methylgallate, and syringate. Demethylation of these compounds is essential for downstream aryl modification, ring opening, and subsequent assimilation of these compounds into the tricarboxylic acid (TCA) cycle, and, correspondingly, there are a variety of associated aryl demethylase systems that vary in complexity. Intriguingly, only a basic understanding of the least complex system, the tetrahydrofolate-dependent aryl demethylase LigM from Sphingomonas paucimobilis, a bacterial strain that metabolizes lignin-derived aromatics, wasmore » previously available. LigM-catalyzed demethylation enables further modification and rin g opening of the single-ring aromatics vanillate and 3-Omethylgallate, which are common byproducts of biofuel production. We characterize aryl O-demethylation by LigM and report its 1.81-Å crystal structure, revealing a unique demethylase fold and a canonical folate-binding domain. Structural homology and geometry optimization calculations enabled the identification of LigM's tetrahydrofolate-binding site and protein-folate interactions. Computationally guided mutagenesis and kinetic analyses allowed the identification of the enzyme's aryl-binding site location and determination of its unique, catalytic tyrosine-dependent reaction mechanism. This work defines LigM as a distinct demethylase, both structurally and functionally, and provides insight into demethylation and its reaction requirements. Our results afford the mechanistic details required for efficient utilization of LigM as a tool for aryl O-demethylation and as a component of synthetic biology efforts to valorize previously underused aromatic compounds.« less

Structure of aryl O -demethylase offers molecular insight into a catalytic tyrosine-dependent mechanism

DOE PAGES

Kohler, Amanda C.; Mills, Matthew J. L.; Adams, Paul D.; ...

2017-04-03

Some strains of soil and marine bacteria have evolved intricate metabolic pathways for using environmentally derived aromatics as a carbon source. Many of these metabolic pathways go through intermediates such as vanillate, 3-O-methylgallate, and syringate. Demethylation of these compounds is essential for downstream aryl modification, ring opening, and subsequent assimilation of these compounds into the tricarboxylic acid (TCA) cycle, and, correspondingly, there are a variety of associated aryl demethylase systems that vary in complexity. Intriguingly, only a basic understanding of the least complex system, the tetrahydrofolate-dependent aryl demethylase LigM from Sphingomonas paucimobilis, a bacterial strain that metabolizes lignin-derived aromatics, wasmore » previously available. LigM-catalyzed demethylation enables further modification and rin g opening of the single-ring aromatics vanillate and 3-Omethylgallate, which are common byproducts of biofuel production. We characterize aryl O-demethylation by LigM and report its 1.81-Å crystal structure, revealing a unique demethylase fold and a canonical folate-binding domain. Structural homology and geometry optimization calculations enabled the identification of LigM's tetrahydrofolate-binding site and protein-folate interactions. Computationally guided mutagenesis and kinetic analyses allowed the identification of the enzyme's aryl-binding site location and determination of its unique, catalytic tyrosine-dependent reaction mechanism. This work defines LigM as a distinct demethylase, both structurally and functionally, and provides insight into demethylation and its reaction requirements. Our results afford the mechanistic details required for efficient utilization of LigM as a tool for aryl O-demethylation and as a component of synthetic biology efforts to valorize previously underused aromatic compounds.« less

R-carrying genotypes of serum paraoxonase (PON1) 192 polymorphism and higher activity ratio are related to susceptibility against ischemic stroke.

PubMed

Mahrooz, Abdolkarim; Gohari, Ghorban; Hashemi, Mohammad-Bagher; Zargari, Mehryar; Musavi, Hadis; Abedini, Mahmoud; Alizadeh, Ahad

2012-12-01

The polymorphic gene of serum paraoxonase (PON1) and its activity involved in atherosclerosis. The purpose of the study was to analyze PON1 192 Q/R polymorphism and the enzyme activities in ischemic stroke. The polymorphism as the most common polymorphism in PON1 gene coding sequence is associated with variation in the enzyme activity and vascular disease. The study included 85 stroke patients and 71 control subjects. PON1 192 polymorphism was genotyped using PCR protocol. Paraoxonase activity (Para) and arylesterase activity (Aryl) were determined spectrophotometrically using paraoxon and phenylacetate as the substrates. The QR and RR genotypes were more frequent in stroke population compared to controls, resulting in a higher frequency of the R allele in patients (0.24 vs 0.18, OR = 1.41). Patients had significantly higher Para/Aryl ratio than that of controls (P = 0.016). In stroke patients, Para/Aryl and Para/HDL ratios increased with this order: QQ < QR < RR. Hypertension significantly increased the risk of ischemic stroke by 15-fold among R-containing people, while this was significantly increased 4-fold for QQ homozygotes. Smoking increased the risk of having ischemic stroke in both QQ homozygote and QR + RR group (OR = 2.84 and OR = 2.33, respectively). In conclusion, these data highlight the importance of PON1 192 R allele and high Para/Aryl ratio in susceptibility to ischemic stroke in the population. The presence of the 192 R allele potentiates the risk of stroke especially in hypertensive people. Decreased Aryl and increased Para/Aryl, Para/HDL and Aryl/HDL ratios may be markers indicated the increased susceptibility to ischemic stroke in the population.

Aryl-substituted aminobenzimidazoles targeting the hepatitis C virus internal ribosome entry site

PubMed Central

Ding, Kejia; Wang, Annie; Boerneke, Mark A.; Dibrov, Sergey M.; Hermann, Thomas

2014-01-01

We describe the exploration of N1-aryl-substituted benzimidazoles as ligands for the hepatitis C virus (HCV) internal ribosome entry site (IRES) RNA. The design of the compounds was guided by the co-crystal structure of a benzimidazole viral translation inhibitor in complex with the RNA target. Structure-binding activity relationships of aryl-substituted benzimidazole ligands were established that were consistent with the crystal structure of the translation inhibitor complex. PMID:24856063

Single-step synthesis of styryl phosphonic acids via palladium-catalyzed Heck coupling of vinyl phosphonic acid with aryl halides

DOE PAGES

McNichols, Brett W.; Koubek, Joshua T.; Sellinger, Alan

2017-10-27

Here, we have developed a single step palladium-catalyzed Heck coupling of aryl halides with vinyl phosphonic acid to produce functionalized (E)-styryl phosphonic acids. This pathway utilizes a variety of commercially available aryl halides, vinyl phosphonic acid and Pd(P(tBu) 3) 2 as catalyst. These conditions produce a wide range of styryl phosphonic acids with high purities and good to excellent yields (31–80%).

Single-step synthesis of styryl phosphonic acids via palladium-catalyzed Heck coupling of vinyl phosphonic acid with aryl halides

DOE Office of Scientific and Technical Information (OSTI.GOV)

McNichols, Brett W.; Koubek, Joshua T.; Sellinger, Alan

Here, we have developed a single step palladium-catalyzed Heck coupling of aryl halides with vinyl phosphonic acid to produce functionalized (E)-styryl phosphonic acids. This pathway utilizes a variety of commercially available aryl halides, vinyl phosphonic acid and Pd(P(tBu) 3) 2 as catalyst. These conditions produce a wide range of styryl phosphonic acids with high purities and good to excellent yields (31–80%).

Enantioselective synthesis of chiral 3-aryl-1-indanones through rhodium-catalyzed asymmetric intramolecular 1,4-addition.

PubMed

Yu, Yue-Na; Xu, Ming-Hua

2013-03-15

Enantioselective synthesis of potentially useful chiral 3-aryl-1-indanones was achieved through a rhodium-catalyzed asymmetric intramolecular 1,4-addition of pinacolborane chalcone derivatives using extraordinary simple MonoPhos as chiral ligand under relatively mild conditions. This novel protocol offers an easy access to a wide variety of enantioenriched 3-aryl-1-indanone derivatives in high yields (up to 95%) with excellent enantioselectivities (up to 95% ee).

Mechanism-based inactivation of benzo(a)pyrene hydroxylase by aryl acetylenes and aryl olefins

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gan, L.S.; Lu, J.Y.L.; Alworth, W.L.

A series of aryl acetylenes and aryl olefins have been examined as substrates and inhibitors of cytochrome P-450 dependent monooxgenases in liver microsomes from 5,6-benzoflavone or phenobarbital pretreated rats. 1-Ethynylpyrene, 3-ethynylperylene, 2-ethynylfluorene, methyl 1-pyrenyl acetylene, cis- and trans-1-(2-bromovinyl)pyrene, and 1-allylpyrene serve as mechanism-based irreversible inactivators (suicide inhibitors) of benzo(a)pyrene hydroxylase, while 1-vinylpyrene and phenyl 1-pyrenyl acetylene do not cause a detectable suicide inhibition of benzo(a)pyrene hydroxylase. The mechanism-based loss of benzo(a)pyrene hydroxylase caused by the aryl acetylenes is not accompanied by a corresponding loss of the P-450 content of the microsomes (suicide destruction). The suicide inhibition by these aryl acetylenesmore » therefore does not involve covalent binding to the heme moiety of the monooxygenase. Nevertheless, in the presence of NADPH, /sup 3/H-labeled 1-ethynylpyrene becomes covalently attached to the cytochrome P-450 protein; the measured stoichiometry of binding is one 1-ethynylpyrene per P-450 heme unit. The authors conclude that the inhibition of benzo(a)pyrene hydroxylase produced by 1-ethynylpyrene may be related to the mechanism of suicide inhibition of P-450 activity by chloramphenicol rather than the mechanism of suicide destruction of P-450 previously described for acetylene and propyne.« less

The evolution of aryl hydrocarbon signaling proteins: diversity of ARNT isoforms among fish species.

PubMed

Powell, W H; Hahn, M E

2000-01-01

The aryl hydrocarbon receptor nuclear translocator (ARNT) mediates aryl hydrocarbon signaling and toxicity by dimerizing with the ligand-activated aryl hydrocarbon receptor (AHR), forming a complex that binds specific DNA elements and alters transcription of target genes. Two genes encode different forms of ARNT in rodents: ARNT1, which is widely expressed, and ARNT2, which exhibits a very restricted expression pattern. In an effort to characterize aryl hydrocarbon signaling mechanisms in fishes, we previously isolated an ARNT cDNA from Fundulus heteroclitus and discovered that this species expresses ARNT2 ubiquitously. This situation differs not only from mammals, but also from rainbow trout, which expresses a divergent ARNT gene that we hypothesized was peculiar to salmonids (rtARNTa/b). In this communication, we examine the ARNT sequences of multiple fish species, including a newly isolated cDNA from scup (Stenotomus chrysops). Our phylogenetic analysis demonstrates that zebrafish ARNT, like the Fundulus protein, is an ARNT2. Contrary to expectations, the scup ARNT is closely related to the rainbow trout protein, demonstrating that the existence of this ARNT isoform predates the divergence of salmonids from the other teleosts. Thus, different species of fish express distinct and highly conserved isoforms of ARNT. The number, type, and expression pattern of ARNT proteins may contribute to interspecies differences in aryl hydrocarbon toxicity, possibly through distinct interactions with additional PAS-family proteins.

Nucleophilic addition of nitrogen to aryl cations: mimicking Titan chemistry.

PubMed

Li, Anyin; Jjunju, Fred P M; Cooks, R Graham

2013-11-01

The reactivity of aryl cations toward molecular nitrogen is studied systematically in an ion trap mass spectrometer at 10(2) Pascal of nitrogen, the pressure of the Titan main haze layer. Nucleophilic addition of dinitrogen occurs and the nature of aryl group has a significant influence on the reactivity, through inductive effects and by changing the ground state spin multiplicity. The products of nitrogen activation, aryldiazonium ions, react with typical nitriles, aromatic amines, and alkynes (compounds that are relevant as possible Titan atmosphere constituents) to form covalently bonded heterocyclic products. Theoretical calculations at the level [DFT(B3LYP)/6-311++G(d,p)] indicate that the N2 addition reaction is exothermic for the singlet aryl cations but endothermic for their triplet spin isomers. The -OH and -NH2 substituted aryl ions are calculated to have triplet ground states, which is consistent with their decreased nitrogen addition reactivity. The energy needed for the generation of the aryl cations from their protonated precursors (ca. 340 kJ/mol starting with protonated aniline) is far less than that required to directly activate the nitrogen triple bond (the lowest energy excited state of N2 lies ca. 600 kJ/mol above the ground state). The formation of aza-aromatics via arene ionization and subsequent reactions provide a conceivable route to the genesis of nitrogen-containing organic molecules in the interstellar medium and Titan haze layers.

Palladium-Catalyzed Coupling of Ammonia with Aryl Chlorides, Bromides, Iodides and Sulfonates: A General Method for the Preparation of Primary Arylamines

PubMed Central

Vo, Giang D.

2010-01-01

We report that the complex generated from Pd[P(o-tol)3]2 and the alkylbisphosphine CyPF-t-Bu is a highly active and selective catalyst for the coupling of ammonia with aryl chlorides, bromides, iodides, and sulfonates. The couplings of ammonia with this catalyst conducted with a solution of ammonia in dioxane form primary arylamines from a variety of aryl electrophiles in high yields. Catalyst loadings as low as 0.1 mol % were sufficient for reactions of many aryl chlorides and bromides. In the presence of this catalyst, aryl sulfonates also coupled with ammonia for the first time in high yields. A comparison of reactions in the presence of this catalyst versus those in the presence of existing copper and palladium systems revealed a complementary, if not broader substrate scope. The utility of this method to generate amides, imides and carbamates is illustrated by a one-pot synthesis of a small library of these carbonyl compounds from aryl bromides and chlorides. Mechanistic studies show that Pd[P(o-tol)3]2 and CyPF-t-Bu generate a more active and general catalyst than that generated from CyPF-t-Bu and palladiun(II) precursors because of the low concentration of active catalyst that is generated from the combination of palladium(II), ammonia and base. PMID:19591470

Synthesis, characterization, and reactivity of arylpalladium cyanoalkyl complexes: selection of catalysts for the alpha-arylation of nitriles.

PubMed

Culkin, Darcy A; Hartwig, John F

2002-08-14

A new coupling process, the palladium-catalyzed alpha-arylation of nitriles, was developed by exploring the structure and reactivity of arylpalladium cyanoalkyl complexes. Complexes of 1,2-bis(diphenylphosphino)benzene (DPPBz), 1,1'-bis(di-i-propylphosphino)ferrocene (D(i)()PrPF), racemic-2,2'-bis(diphenylphosphino)-1,1'-binaphthyl (BINAP), and diphenylethylphosphine (PPh(2)Et) were prepared. Coordination to palladium through the alpha-carbon was observed for DPPBz-ligated complexes and for complexes of primary and benzylic nitrile anions. However, the anion of isobutyronitrile was coordinated to palladium through the cyano-nitrogen when the complex was ligated by D(i)()PrPF. The isobutyronitrile anion displaced a phosphine ligand to form a C,N-bridged dimer when generated from PPh(2)Et-ligated palladium. These results suggest that the nitrile anion preferentially coordinates to palladium through the carbon atom in the absence of steric effects. Thermolysis of the arylpalladium cyanoalkyl complexes led to reductive elimination that formed alpha-aryl nitriles. The high yields and short reaction times observed for BINAP-ligated complexes suggested that BINAP-ligated palladium catalysts might be appropriate for the arylation of nitriles. Initial results on a palladium-catalyzed process for the direct coupling of aryl bromides and primary, benzylic, and secondary nitrile anions to form alpha-aryl nitriles in good yields are reported.

A new family of nucleophiles for photoinduced, copper-catalyzed cross-couplings via single-electron transfer: reactions of thiols with aryl halides under mild conditions (O °C).

PubMed

Uyeda, Christopher; Tan, Yichen; Fu, Gregory C; Peters, Jonas C

2013-06-26

Building on the known photophysical properties of well-defined copper-carbazolide complexes, we have recently described photoinduced, copper-catalyzed N-arylations and N-alkylations of carbazoles. Until now, there have been no examples of the use of other families of heteroatom nucleophiles in such photoinduced processes. Herein, we report a versatile photoinduced, copper-catalyzed method for coupling aryl thiols with aryl halides, wherein a single set of reaction conditions, using inexpensive CuI as a precatalyst without the need for an added ligand, is effective for a wide range of coupling partners. As far as we are aware, copper-catalyzed C-S cross-couplings at 0 °C have not previously been achieved, which renders our observation of efficient reaction of an unactivated aryl iodide at -40 °C especially striking. Mechanistic investigations are consistent with these photoinduced C-S cross-couplings following a SET/radical pathway for C-X bond cleavage (via a Cu(I)-thiolate), which contrasts with nonphotoinduced, copper-catalyzed processes wherein a concerted mechanism is believed to occur.

Synthesis of 8-Aryl-O-methylcyanidins and Their Usage for Dye-Sensitized Solar Cell Devices.

PubMed

Kimura, Yuki; Oyama, Kin-Ichi; Murata, Yasujiro; Wakamiya, Atsushi; Yoshida, Kumi

2017-02-16

Anthocyanins as natural pigments are colorful and environmentally compatible dyes for dye-sensitized solar cells (DSSCs). To increase the efficiency, we designed and synthesized unnatural O -methylflavonols and O -methylcyanidins that possess an aryl group at the 8-position. We synthesized per - O -methylquercetin from quercetin, then using selective demethylation prepared various O -methylquercetins. Using the Suzuki-Miyaura coupling reaction, 8-arylation of per - O -methylquercetin was achieved. Using a LiAlH₄ reduction or Clemmensen reduction, these flavonols were transformed to the corresponding cyanidin derivatives in satisfactory yields. Using these dyes, we fabricated DSSCs, and their efficiency was investigated. The efficiency of tetra - O -methylflavonol was 0.31%. However, the introduction of the 8-aryl residue increased the efficiency to 1.04%. In comparison to these flavonols, O -methylcyanidins exhibited a lower efficiency of 0.05% to 0.52%. The introduction of the 8-aryl group into the cyanidin derivatives did not result in a remarkable increase in the efficiency. These phenomena may be due to the poor fit of the HOMO-LUMO level of the dyes to the TiO₂ conduction band.

Cloning and heterologous expression of two aryl-aldehyde dehydrogenases from the white-rot basidiomycete Phanerochaete chrysosporium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nakamura, Tomofumi; Fukuoka Institute of Health and Environmental Sciences, 39 Mukaizano, Dazaifu-shi, Fukuoka 818-0135; Ichinose, Hirofumi

2010-04-09

We identified two aryl-aldehyde dehydrogenase proteins (PcALDH1 and PcALDH2) from the white-rot basidiomycete Phanerochaete chrysosporium. Both PcALDHs were translationally up-regulated in response to exogenous addition of vanillin, one of the key aromatic compounds in the pathway of lignin degradation by basidiomycetes. To clarify the catalytic functions of PcALDHs, we isolated full-length cDNAs encoding these proteins and heterologously expressed the recombinant enzymes using a pET/Escherichia coli system. The open reading frames of both PcALDH1 and PcALDH2 consisted of 1503 nucleotides. The deduced amino acid sequences of both proteins showed high homologies with aryl-aldehyde dehydrogenases from other organisms and contained ten conservedmore » domains of ALDHs. Moreover, a novel glycine-rich motif 'GxGxxxG' was located at the NAD{sup +}-binding site. The recombinant PcALDHs catalyzed dehydrogenation reactions of several aryl-aldehyde compounds, including vanillin, to their corresponding aromatic acids. These results strongly suggested that PcALDHs metabolize aryl-aldehyde compounds generated during fungal degradation of lignin and various aromatic xenobiotics.« less

Process for derivatizing carbon nanotubes with diazonium species and compositions thereof

NASA Technical Reports Server (NTRS)

Bahr, Jeffrey L. (Inventor); Tour, James M. (Inventor); Yang, Jiping (Inventor)

2011-01-01

Methods for the chemical modification of carbon nanotubes involve the derivatization of multi- and single-wall carbon nanotubes, including small diameter (ca. 0.7 nm) single-wall carbon nanotubes, with diazonium species. The method allows the chemical attachment of a variety of organic compounds to the side and ends of carbon nanotubes. These chemically modified nanotubes have applications in polymer composite materials, molecular electronic applications, and sensor devices. The methods of derivatization include electrochemical induced reactions, thermally induced reactions, and photochemically induced reactions. Moreover, when modified with suitable chemical groups, the derivatized nanotubes are chemically compatible with a polymer matrix, allowing transfer of the properties of the nanotubes (such as, mechanical strength or electrical conductivity) to the properties of the composite material as a whole. Furthermore, when modified with suitable chemical groups, the groups can be polymerized to form a polymer that includes carbon nanotubes.

Highly sensitive electrochemical biosensor for bisphenol A detection based on a diazonium-functionalized boron-doped diamond electrode modified with a multi-walled carbon nanotube-tyrosinase hybrid film.

PubMed

Zehani, Nedjla; Fortgang, Philippe; Saddek Lachgar, Mohamed; Baraket, Abdoullatif; Arab, Madjid; Dzyadevych, Sergei V; Kherrat, Rochdi; Jaffrezic-Renault, Nicole

2015-12-15

A highly sensitive electrochemical biosensor for the detection of Bisphenol A (BPA) in water has been developed by immobilizing tyrosinase onto a diazonium-functionalized boron doped diamond electrode (BDD) modified with multi-walled carbon nanotubes (MWCNTs). The fabricated biosensor exhibits excellent electroactivity towards o-quinone, a product of this enzymatic reaction of BPA oxidation catalyzed by tyrosinase. The developed BPA biosensor displays a large linear range from 0.01 nM to 100 nM, with a detection limit (LOD) of 10 pM. The feasibility of the proposed biosensor has been demonstrated on BPA spiked water river samples. Therefore, it could be a promising and reliable analytical tool for on-site monitoring of BPA in waste water. Copyright © 2015 Elsevier B.V. All rights reserved.

Covalent modification of graphene and graphite using diazonium chemistry: tunable grafting and nanomanipulation.

PubMed

Greenwood, John; Phan, Thanh Hai; Fujita, Yasuhiko; Li, Zhi; Ivasenko, Oleksandr; Vanderlinden, Willem; Van Gorp, Hans; Frederickx, Wout; Lu, Gang; Tahara, Kazukuni; Tobe, Yoshito; Uji-I, Hiroshi; Mertens, Stijn F L; De Feyter, Steven

2015-05-26

We shine light on the covalent modification of graphite and graphene substrates using diazonium chemistry under ambient conditions. We report on the nature of the chemical modification of these graphitic substrates, the relation between molecular structure and film morphology, and the impact of the covalent modification on the properties of the substrates, as revealed by local microscopy and spectroscopy techniques and electrochemistry. By careful selection of the reagents and optimizing reaction conditions, a high density of covalently grafted molecules is obtained, a result that is demonstrated in an unprecedented way by scanning tunneling microscopy (STM) under ambient conditions. With nanomanipulation, i.e., nanoshaving using STM, surface structuring and functionalization at the nanoscale is achieved. This manipulation leads to the removal of the covalently anchored molecules, regenerating pristine sp(2) hybridized graphene or graphite patches, as proven by space-resolved Raman microscopy and molecular self-assembly studies.

Regioselective Copper-Catalyzed Amination of Chlorobenzoic Acids: Synthesis and Solid-State Structures of N-Aryl Anthranilic Acid Derivatives

PubMed Central

Mei, Xuefeng; August, Adam T.; Wolf, Christian

2008-01-01

A chemo- and regioselective copper-catalyzed cross-coupling reaction for effective amination of 2-chlorobenzoic acids with aniline derivatives has been developed. The method eliminates the need for acid protection and produces a wide range of N-aryl anthranilic acid derivatives in up to 99%. The amination was found to proceed with both electron-rich and electron-deficient aryl chlorides and anilines and also utilizes sterically hindered anilines such as 2,6-dimethylaniline and 2-tert-butylaniline. The conformational isomerism of appropriately substituted N-aryl anthranilic acids has been investigated in the solid state. Crystallographic analysis of seven anthranilic acid derivatives showed formation of two distinct supramolecular architectures exhibiting trans-anti- and unprecedented trans-syn-dimeric structures. PMID:16388629

Lanthanum Tricyanide-Catalyzed Acyl Silane-Ketone Benzoin Additions and Kinetic Resolution of Resultant α-Silyloxyketones

PubMed Central

Tarr, James C.

2010-01-01

We report the full account of our efforts on the lanthanum tricyanide-catalyzed acyl silane-ketone benzoin reaction. The reaction exhibits a wide scope in both acyl silane (aryl, alkyl) and ketone (aryl-alkyl, alkyl-alkyl, aryl-aryl, alkenyl-alkyl, alkynyl-alkyl) coupling partners. The diastereoselectivity of the reaction has been examined in both cyclic and acyclic systems. Cyclohexanones give products arising from equatorial attack by the acyl silane. The diastereoselectivity of acyl silane addition to acyclic α-hydroxy ketones can be controlled by varying the protecting group to obtain either Felkin-Ahn or chelation control. The resultant α-silyloxyketone products can be resolved with selectivity factors from 10 to 15 by subjecting racemic ketone benzoin products to CBS reduction. PMID:20392127

Synthesis and optical properties of new 5'-aryl-substituted 2,5-bis(3-decyl-2,2'-bithiophen-5-yl)-1,3,4-oxadiazoles.

PubMed

Kostyuchenko, Anastasia Sergeevna; Zheleznova, Tatyana Yu; Stasyuk, Anton Jaroslavovich; Kurowska, Aleksandra; Domagala, Wojciech; Pron, Adam; Fisyuk, Alexander S

2017-01-01

New photoluminescent donor-acceptor-donor (DAD) molecules, namely 5'-aryl-substituted 2,5-bis(3-decyl-2,2'-bithiophen-5-yl)-1,3,4-oxadiazoles were prepared by palladium-catalyzed coupling from readily available compounds such as ethyl 3-decyl-2,2'-bithiophene-5-carboxylate and aryl halides. The obtained compounds feature increasing bathochromic shifts in their emission spectra with increasing aryl-substituent size yielding blue to bluish-green emissions. At the same time, their absorption spectra are almost independent from the identity of the terminal substituent with λ max values ranging from 395 to 405 nm. The observed trends are perfectly predicted by quantum chemical DFT/TDDFT calculations carried out for these new molecules.

Synthesis and optical properties of new 5'-aryl-substituted 2,5-bis(3-decyl-2,2'-bithiophen-5-yl)-1,3,4-oxadiazoles

PubMed Central

Kostyuchenko, Anastasia Sergeevna; Zheleznova, Tatyana Yu; Stasyuk, Anton Jaroslavovich; Kurowska, Aleksandra; Domagala, Wojciech

2017-01-01

New photoluminescent donor–acceptor–donor (DAD) molecules, namely 5'-aryl-substituted 2,5-bis(3-decyl-2,2'-bithiophen-5-yl)-1,3,4-oxadiazoles were prepared by palladium-catalyzed coupling from readily available compounds such as ethyl 3-decyl-2,2'-bithiophene-5-carboxylate and aryl halides. The obtained compounds feature increasing bathochromic shifts in their emission spectra with increasing aryl-substituent size yielding blue to bluish-green emissions. At the same time, their absorption spectra are almost independent from the identity of the terminal substituent with λmax values ranging from 395 to 405 nm. The observed trends are perfectly predicted by quantum chemical DFT/TDDFT calculations carried out for these new molecules. PMID:28326140

Diuresis and reduced urinary osmolality in rats produced by small-molecule UT-A-selective urea transport inhibitors.

PubMed

Esteva-Font, Cristina; Cil, Onur; Phuan, Puay-Wah; Su, Tao; Lee, Sujin; Anderson, Marc O; Verkman, A S

2014-09-01

Urea transport (UT) proteins of the UT-A class are expressed in epithelial cells in kidney tubules, where they are required for the formation of a concentrated urine by countercurrent multiplication. Here, using a recently developed high-throughput assay to identify UT-A inhibitors, a screen of 50,000 synthetic small molecules identified UT-A inhibitors of aryl-thiazole, γ-sultambenzosulfonamide, aminocarbonitrile butene, and 4-isoxazolamide chemical classes. Structure-activity analysis identified compounds that inhibited UT-A selectively by a noncompetitive mechanism with IC50 down to ∼1 μM. Molecular modeling identified putative inhibitor binding sites on rat UT-A. To test compound efficacy in rats, formulations and administration procedures were established to give therapeutic inhibitor concentrations in blood and urine. We found that intravenous administration of an indole thiazole or a γ-sultambenzosulfonamide at 20 mg/kg increased urine output by 3-5-fold and reduced urine osmolality by ∼2-fold compared to vehicle control rats, even under conditions of maximum antidiuresis produced by 1-deamino-8-D-arginine vasopressin (DDAVP). The diuresis was reversible and showed urea > salt excretion. The results provide proof of concept for the diuretic action of UT-A-selective inhibitors. UT-A inhibitors are first in their class salt-sparing diuretics with potential clinical indications in volume-overload edemas and high-vasopressin-associated hyponatremias. © FASEB.

A Green Synthesis of Xanthenone Derivatives in Aqueous Media Using TiO2-CNTs Nanocomposite as an Eco-Friendly and Re-Usable Catalyst.

PubMed

Samani, Amir; Abdolmohammadi, Shahrzad; Otaredi-Kashani, Asieh

2018-01-01

The xanthene (dibenzopyran) framework constitutes the core structure of many biologically active compounds, that they have been of interest because of their pharmacological activities like antiviral, antibacterial, anti-inflammatory, and CCR1 antagonist. As heterogeneous catalysts offer several advantages over homogeneous catalysts, the performance of reactions on the surface of nanosized heterogeneous salts has received a great deal of interest in recent years. In the area of nanosized heterogeneous catalysts there is a noticeable range of reactions that are catalyzed efficiently by TiO2 NPs. Moreover, carbon nanotubes (CNTs) as a support can be used to obtain nanoparticles with modified morphology, structural, chemical, electrical, and optical properties. The catalytic activity of titanium dioxide supported on carbon nanotubes has been greatly improved. The present methodology focus on the synthesis of 7,7-dimethyl-10-aryl- 6,7,8,10-tetrahydro-9H-[1,3]dioxolo[4,5-b]xanthen-9-ones, through a condensation reaction of dimedone, aromatic aldehydes and 3,4-methylenedioxyphenol, using a catalytic amount of TiO2- CNTs nanocomposite (15 mol%) at 80 ˚C in aqueous media, within 60-90 min. The TiO2-CNTs nanocomposite was also prepared by a known simple sonochemical method. A series of 7,7-dimethyl-10-aryl-6,7,8,10-tetrahydro-9H-[1,3]dioxolo[4,5-b]xanthen-9-ones were successfully synthesized in high yields (92-98%). All synthesized compounds were well characterized by their satisfactory elemental analyses, IR, 1H and 13C NMR spectroscopy. The synthesized catalyst was fully characterized by SEM, TEM, XRD, and EDX techniques. In summary, this investigation constitutes a novel and efficient route for the synthesis of 7,7-dimethyl-10-aryl-6,7,8,10-tetrahydro-9H-[1,3]dioxolo[4,5-b]xanthen-9-ones in high yields, by a three-component reaction of dimedone, aromatic aldehydes and 3,4-methylenedioxyphenol in water and in the presence of the TiO2-CNTs nanocomposite as a green, effective and recyclable catalyst. This novel method has the advantages of high yields, mild reaction conditions, short reaction time, easy work-up, inexpensive reagents and environmentally friendly procedure. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Diastereoselective syntheses of 3-aryl-5-(arylalkyl)-6-methyl-1-(1-phenylethyl)thioxotetrahydropyrimidin-4(1H)-ones: a stereochemical perspective from endo and exocyclic chiral centres.

PubMed

Kumar, Varun; Raghavaiah, Pallepogu; Mobin, Shaikh M; Nair, Vipin A

2010-11-07

Diastereoselective syntheses of 3-aryl-(S/R)-6-methyl-1-[(S/R)-1-phenylethyl)]-2-thioxotetrahydro pyrimidin-4(1H)-ones were achieved in good yields by the condensation of aryl isothiocyanates with ethyl 3-(1-phenylethylamino)butanoate in a one-pot reaction. Benzylation of these substrates illustrated that the orientations of the exocylic and endocylic groups determine the stereochemical outcome of the product formed.

Substitution of the nitro group with Grignard reagents: facile arylation and alkenylation of pyridine N-oxides.

PubMed

Zhang, Fang; Zhang, Song; Duan, Xin-Fang

2012-11-02

The unprecedented substitution of a nitro group with aryl or alkenyl groups of Grignard reagents affords 2-aryl or alkenylpyridine N-oxides in modest to high yields with high chemoselectivity. This protocol allows a simple and clean synthesis of various 2-substituted pyridine N-oxides and the corresponding pyridine derivatives. Furthermore, straightforward one-pot iterative functionality of pyridine N-oxides could also be achieved simply by successive applications of two Grignard reagents.

Assembly of N,N-disubstituted hydrazines and 1-aryl-1H-indazoles via copper-catalyzed coupling reactions.

PubMed

Xiong, Xiaodong; Jiang, Yongwen; Ma, Dawei

2012-05-18

CuI-catalyzed coupling of N-acyl-N'-substituted hydrazines with aryl iodides takes place at 60-90 °C to afford N-acyl-N',N'-disubstituted hydrazines regioselectively and thereby gives a facile method for assembling N,N-diaryl hydrazines. N-Acyl-N'-substituted hydrazines can also react with 2-bromoarylcarbonylic compounds at 60-125 °C under the catalysis of CuI/4-hydroxy-l-proline to provide 1-aryl-1H-indazoles.

Photooxidation of Mixed Aryl and Biarylphosphines

PubMed Central

Zhang, Dong; Celaje, Jeff A.; Agua, Alon; Doan, Chad; Stewart, Timothy; Bau, Robert; Selke, Matthias

2010-01-01

Aryl phosphines and dialkylbiaryl phosphines react with singlet oxygen to form phosphinate esters. For mixed arylphosphines, the most electron-rich aryl group migrates to form the phosphinate, while for dialkylbiaryl phosphines migration of the alkyl group occurs. Dialkylbiaryl phosphines also yield arene epoxides, especially in electron rich systems. Phosphinate ester formation is increased at high temperature while protic solvents increase the yield of epoxide. The product distribution provides evidence for Buchwald’s recent conformational model for the aerobic oxidation of dialkylbiaryl phosphines. PMID:20527907

Reactivity of bromoselenophenes in palladium-catalyzed direct arylations.

PubMed

Skhiri, Aymen; Ben Salem, Ridha; Soulé, Jean-François; Doucet, Henri

2017-01-01

The reactivity of 2-bromo- and 2,5-dibromoselenophenes in Pd-catalyzed direct heteroarylation was investigated. From 2-bromoselenophene, only the most reactive heteroarenes could be employed to prepare 2-heteroarylated selenophenes; whereas, 2,5-dibromoselenophene generally gave 2,5-di(heteroarylated) selenophenes in high yields using both thiazole and thiophene derivatives. Moreover, sequential catalytic C2 heteroarylation, bromination, catalytic C5 arylation reactions allowed the synthesis of unsymmetrical 2,5-di(hetero)arylated selenophene derivatives in three steps from selenophene.

New aromatic activated dihalides and bisphenol monomers for the preparation of novel poly(arylene ethers)

NASA Technical Reports Server (NTRS)

Wolfe, James F.

1993-01-01

The goal of this research program was to synthesize a series of unique monomers of type I to be utilized at NASA-Langley in the preparation of new poly(arylene ether ketones), poly(arylene ether ketosulfones), and poly(arylene ether ketophosphine oxides). These A-A and A-B monomer systems, which possess activated aryl halide and/or phenolic end groups, are accessible via condensation reactions of appropriately substituted aryl acetonitrile carbanions with activated aryl dihalides followed by oxidative decyanation.

N,N-Diethylurea-Catalyzed Amidation between Electron-Defficient Aryl Azides and Phenylacetaldehydes

PubMed Central

Xie, Sheng; Ramström, Olof; Yan, Mingdi

2015-01-01

Urea structures, of which N,N-diethylurea (DEU) proved to be the most efficient, were discovered to catalyze amidation reactions between electron-defficient aryl azides and phenylacetaldehydes. Experimental data support 1,3-dipolar cycloaddition between DEU-activated enols and electrophilic phenyl azides, especially perfluoroaryl azides, followed by rearrangement of the triazoline intermediate. The activation of the aldehyde under near-neutral conditions was of special importance in inhibiting dehydration/aromatization of the triazoline intermediate, thus promoting the rearrangement to form aryl amides. PMID:25616121

Access to 6a-Alkyl Aporphines: Synthesis of (±)-N-Methylguattescidine.

PubMed

Ku, Angela F; Cuny, Gregory D

2016-10-21

(-)-N-Methylguattescidine (3) is an alkaloid recently isolated from Fissistigma latifolium and assigned as a rare example of a 6a-alkyl aporphine. Herein, we report the synthesis of (±)-3 and the des-hydroxyl derivative 4 using our previously reported ortho-phenol arylation methodology mediated by the XPhos precatalyst as a key synthetic step. In addition, substituents on the aryl halide portion of the ortho-phenol arylation substrates significantly influenced the formation of an oxidized side product.

Pd-Catalyzed N-Arylation of Secondary Acyclic Amides: Catalyst Development, Scope, and Computational Study

PubMed Central

Hicks, Jacqueline D.; Hyde, Alan M.; Cuezva, Alberto Martinez; Buchwald, Stephen L.

2009-01-01

We report the efficient N-arylation of acyclic secondary amides and related nucleophiles with aryl nonaflates, triflates, and chlorides. This method allows for easy variation of the aromatic component in tertiary aryl amides. A new biaryl phosphine with P-bound 3,5-(bis)trifluoromethylphenyl groups was found to be uniquely effective for this amidation. The critical aspects of the ligand were explored through synthetic, mechanistic, and computational studies. Systematic variation of the ligand revealed the importance of (1) a methoxy group on the aromatic carbon of the “top ring” ortho to the phosphorus and (2) two highly electron-withdrawing P-bound 3,5-(bis)trifluoromethylphenyl groups. Computational studies suggest the electron-deficient nature of the ligand is important in facilitating amide binding to the LPd(II)(Ph)(X) intermediate. PMID:19886610

Aryl Polyenes, a Highly Abundant Class of Bacterial Natural Products, Are Functionally Related to Antioxidative Carotenoids.

PubMed

Schöner, Tim A; Gassel, Sören; Osawa, Ayako; Tobias, Nicholas J; Okuno, Yukari; Sakakibara, Yui; Shindo, Kazutoshi; Sandmann, Gerhard; Bode, Helge B

2016-02-02

Bacterial pigments of the aryl polyene type are structurally similar to the well-known carotenoids with respect to their polyene systems. Their biosynthetic gene cluster is widespread in taxonomically distant bacteria, and four classes of such pigments have been found. Here we report the structure elucidation of the aryl polyene/dialkylresorcinol hybrid pigments of Variovorax paradoxus B4 by HPLC-UV-MS, MALDI-MS and NMR. Furthermore, we show for the first time that this pigment class protects the bacterium from reactive oxygen species, similarly to what is known for carotenoids. An analysis of the distribution of biosynthetic genes for aryl polyenes and carotenoids in bacterial genomes is presented; it shows a complementary distribution of these protective pigments in bacteria. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Visible-light-driven Photocatalytic N-arylation of Imidazole Derivatives and Arylboronic Acids on Cu/graphene catalyst

NASA Astrophysics Data System (ADS)

Cui, Yan-Li; Guo, Xiao-Ning; Wang, Ying-Yong; Guo, Xiang-Yun

2015-07-01

N-aryl imidazoles play an important role as structural and functional units in many natural products and biologically active compounds. Herein, we report a photocatalytic route for the C-N cross-coupling reactions over a Cu/graphene catalyst, which can effectively catalyze N-arylation of imidazole and phenylboronic acid, and achieve a turnover frequency of 25.4 h-1 at 25 oC and the irradiation of visible light. The enhanced catalytic activity of the Cu/graphene under the light irradiation results from the localized surface plasmon resonance of copper nanoparticles. The Cu/graphene photocatalyst has a general applicability for photocatalytic C-N, C-O and C-S cross-coupling of arylboronic acids with imidazoles, phenols and thiophenols. This study provides a green photocatalytic route for the production of N-aryl imidazoles.

Synthesis and biological screening of 2'-aryl/benzyl-2-aryl-4-methyl-4',5-bithiazolyls as possible anti-tubercular and antimicrobial agents.

PubMed

Abhale, Yogita K; Sasane, Amit V; Chavan, Abhijit P; Deshmukh, Keshav K; Kotapalli, Sudha Sravanti; Ummanni, Ramesh; Sayyad, Sadikali F; Mhaske, Pravin C

2015-04-13

A series of 2'-aryl/benzyl-2-aryl-4-methyl-4',5-bithiazolyl derivatives, 25-64 were synthesized and evaluated for inhibitory activity against Mycobacterium smegmatis MC(2) 155 strain and antimicrobial activities against four pathogenic bacteria Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Proteus vulgaris. Among them, compounds 40, 49, 50, and 54 exhibited moderate to good inhibition on the growth of the bacteria Mycobacterium smegmatis at the concentration of 30 μM. Compounds 26, 40, 44, 54 and 56 exhibited moderate to good antibacterial activity. Compound 5-(2'-(4-fluorobenzyl)thiazol-4'-yl)-2-(4-fluorophenyl)-4-methyl-thiazole (54) exhibited both antitubercular as well as antimicrobial activity against all tested strains. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

Anaerobic Aryl Reductive Dehalogenation of Halobenzoates by Cell Extracts of “Desulfomonile tiedjei”

PubMed Central

DeWeerd, Kim A.; Suflita, Joseph M.

1990-01-01

We studied the transformation of halogenated benzoates by cell extracts of a dehalogenating anaerobe, “Desulfomonile tiedjei.” We found that cell extracts possessed aryl reductive dehalogenation activity. The activity was heat labile and dependent on the addition of reduced methyl viologen, but not on that of reduced NAD, NADP, flavin mononucleotide, flavin adenine dinucleotide, desulfoviridin, cytochrome c3, or benzyl viologen. Dehalogenation activity in extracts was stimulated by formate, CO, or H2, but not by pyruvate plus coenzyme A or by dithionite. The pH and temperature optima for aryl dehalogenation were 8.2 and 35°C, respectively. The rate of dehalogenation was proportional to the amount of protein in the assay mixture. The substrate specificity of aryl dehalogenation activity for various aromatic compounds in “D. tiedjei” cell extracts was identical to that of whole cells, except differences were observed in the relative rates of halobenzoate transformation. Dehalogenation was 10-fold greater in “D. tiedjei” extracts prepared from cells cultured in the presence of 3-chlorobenzoate, suggesting that the activity was inducible. Aryl reductive dehalogenation in extracts was inhibited by sulfite, sulfide, and thiosulfate, but not sulfate. Experiments with combinations of substrates suggested that cell extracts dehalogenated 3-iodobenzoate more readily than either 3,5-dichlorobenzoate or 3-chlorobenzoate. Dehalogenation activity was found to be membrane associated. This is the first report characterizing aryl dehalogenation activity in cell extracts of an obligate anaerobe. PMID:16348308

Palladium-catalyzed coupling of ammonia with aryl chlorides, bromides, iodides, and sulfonates: a general method for the preparation of primary arylamines.

PubMed

Vo, Giang D; Hartwig, John F

2009-08-12

We report that the complex generated from Pd[P(o-tol)(3)](2) and the alkylbisphosphine CyPF-t-Bu is a highly active and selective catalyst for the coupling of ammonia with aryl chlorides, bromides, iodides, and sulfonates. The couplings of ammonia with this catalyst conducted with a solution of ammonia in dioxane form primary arylamines from a variety of aryl electrophiles in high yields. Catalyst loadings as low as 0.1 mol % were sufficient for reactions of many aryl chlorides and bromides. In the presence of this catalyst, aryl sulfonates also coupled with ammonia for the first time in high yields. A comparison of reactions in the presence of this catalyst versus those in the presence of existing copper and palladium systems revealed a complementary, if not broader, substrate scope. The utility of this method to generate amides, imides, and carbamates is illustrated by a one-pot synthesis of a small library of these carbonyl compounds from aryl bromides and chlorides, ammonia, and acid chlorides or anhydrides. Mechanistic studies show that reactions conducted with the combination of Pd[P(o-tol)(3)](2) and CyPF-t-Bu as catalyst occur with faster rates and higher yields than those conducted with CyPF-t-Bu and palladiun(II) as catalyst precursors because of the low concentration of active catalyst that is generated from the combination of palladium(II), ammonia, and base.

A robust protocol for directed aryl sulfotransferase evolution toward the carbohydrate building block GlcNAc.

PubMed

Islam, Shohana; Mate, Diana M; Martínez, Ronny; Jakob, Felix; Schwaneberg, Ulrich

2018-05-01

Bacterial aryl sulfotransferases (AST) utilize p-nitrophenylsulfate (pNPS) as a phenolic donor to sulfurylate typically a phenolic acceptor. Interest in aryl sulfotransferases is growing because of their broad variety of acceptors and cost-effective sulfuryl-donors. For instance, aryl sulfotransferase A (ASTA) from Desulfitobacterium hafniense was recently reported to sulfurylate d-glucose. In this study, a directed evolution protocol was developed and validated for aryl sulfotransferase B (ASTB). Thereby the well-known pNPS quantification system was advanced to operate efficiently as a continuous screening system in 96-well MTP format with a true coefficient of variation of 14.3%. A random mutagenesis library (SeSaM library) of ASTB was screened (1,760 clones) to improve sulfurylation of the carbohydrate building block N-acetylglucosamine (GlcNAc). The beneficial variant ASTB-V1 (Val579Asp) showed an up to 3.4-fold increased specific activity toward GlcNAc when compared to ASTB-WT. HPLC- and MS-analysis confirmed ASTB-V1's increased GlcNAc monosulfurylation (2.4-fold increased product formation) representing the validation of the first successful directed evolution round of an AST for a saccharide substrate. © 2017 Wiley Periodicals, Inc.

Improved synthesis of aryltrialkoxysilanes via treatment of aryl Grignard or lithium reagents with tetraalkyl orthosilicates.

PubMed

Manoso, Amy S; Ahn, Chuljin; Soheili, Arash; Handy, Christopher J; Correia, Reuben; Seganish, W Michael; Deshong, Philip

2004-11-26

General reaction conditions for the synthesis of aryl(trialkoxy)silanes from aryl Grignard and lithium reagents and tetraalkyl orthosilicates (Si(OR)(4)) have been developed. Ortho-, meta-, and para-substituted bromoarenes underwent efficient metalation and silylation at low temperature to provide aryl siloxanes. Mixed results were obtained with heteroaromatic substrates: 3-bromothiophene, 3-bromo-4-methoxypyridine, 5-bromoindole, and N-methyl-5-bromoindole underwent silylation in good yield, whereas a low yield of siloxane was obtained from 2-bromofuran, and 2-bromopyridine failed to give silylated product. The synthesis of siloxanes via organolithium and magnesium reagents was limited by the formation of di- and triarylated silanes (Ar(2)Si(OR)(2) and Ar(3)SiOR, respectively) and dehalogenated (Ar-H) byproducts. Silylation at low temperature gave predominantly monoaryl siloxanes, without requiring a large excess of the electrophile. Optimal reaction conditions for the synthesis of siloxanes from aryl Grignard reagents entailed addition of arylmagnesium reagents to 3 equiv of tetraethyl- or tetramethyl orthosilicate at -30 degrees C in THF. Aryllithium species were silylated using 1.5 equiv of tetraethyl- or tetramethyl orthosilicate at -78 degrees C in ether.

Synthesis of 8-Aryl-O-methylcyanidins and Their Usage for Dye-Sensitized Solar Cell Devices

PubMed Central

Kimura, Yuki; Oyama, Kin-ichi; Murata, Yasujiro; Wakamiya, Atsushi; Yoshida, Kumi

2017-01-01

Anthocyanins as natural pigments are colorful and environmentally compatible dyes for dye-sensitized solar cells (DSSCs). To increase the efficiency, we designed and synthesized unnatural O-methylflavonols and O-methylcyanidins that possess an aryl group at the 8-position. We synthesized per-O-methylquercetin from quercetin, then using selective demethylation prepared various O-methylquercetins. Using the Suzuki-Miyaura coupling reaction, 8-arylation of per-O-methylquercetin was achieved. Using a LiAlH4 reduction or Clemmensen reduction, these flavonols were transformed to the corresponding cyanidin derivatives in satisfactory yields. Using these dyes, we fabricated DSSCs, and their efficiency was investigated. The efficiency of tetra-O-methylflavonol was 0.31%. However, the introduction of the 8-aryl residue increased the efficiency to 1.04%. In comparison to these flavonols, O-methylcyanidins exhibited a lower efficiency of 0.05% to 0.52%. The introduction of the 8-aryl group into the cyanidin derivatives did not result in a remarkable increase in the efficiency. These phenomena may be due to the poor fit of the HOMO-LUMO level of the dyes to the TiO2 conduction band. PMID:28212330

Sulfonamidation of Aryl and Heteroaryl Halides through Photosensitized Nickel Catalysis.

PubMed

Kim, Taehoon; McCarver, Stefan J; Lee, Chulbom; MacMillan, David W C

2018-03-19

Herein we report a highly efficient method for nickel-catalyzed C-N bond formation between sulfonamides and aryl electrophiles. This technology provides generic access to a broad range of N-aryl and N-heteroaryl sulfonamide motifs, which are widely represented in drug discovery. Initial mechanistic studies suggest an energy-transfer mechanism wherein C-N bond reductive elimination occurs from a triplet excited Ni II complex. Late-stage sulfonamidation in the synthesis of a pharmacologically relevant structure is also demonstrated. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

A New Route to Azafluoranthene Natural Products via Direct Arylation

PubMed Central

Ponnala, Shashikanth; Harding, Wayne W.

2013-01-01

Microwave-assisted direct arylation was successfully employed in the synthesis of azafluoranthene alkaloids for the first time. Direct arylation reactions on a diverse set of phenyltetrahydroisoquinolines produces the indeno[1,2,3-ij]isoquinoline nucleus en route to a high yielding azafluoranthene synthesis. The method was used as a key step in the efficient preparation of the natural products rufescine and triclisine. As demonstrated herein, this synthetic approach should be generally applicable to the preparation of natural and un-natural azafluoranthene alkaloids as well as “azafluoranthene-like” isoquinoline alkaloids. PMID:23503080

Triphenylphosphine as Ligand for Room Temperature Ni(0)-Catalyzed Cross-Coupling Reactions of Aryl Chlorides with Arylboronic Acids

PubMed Central

Tang, Zhen-Yu; Hu, Qiao-Sheng

2008-01-01

Room temperature Ni(0)-catalyzed cross-coupling reactions of deactivated aryl chlorides with arylboronic acids with inexpensive triphenylphosphine (PPh3) as a supporting ligand have been accomplished in good to excellent yields. Air-stable Ni(PPh3)2Cl2 has also been established as catalyst precursor and highly active nickel catalysts were obtained when the reduction of Ni(PPh3)2Cl2 with n-BuLi was carried out in presence of an aryl chloride. PMID:16497011

Silica-Supported Catalyst for Enantioselective Arylation of Aldehydes under Batch and Continuous-Flow Conditions.

PubMed

Watanabe, Satoshi; Nakaya, Naoyuki; Akai, Junichiro; Kanaori, Kenji; Harada, Toshiro

2018-05-04

A silica-supported 3-aryl H 8 -BINOL-derived titanium catalyst exhibited high performance in the enantioselective arylation of aromatic aldehydes using Grignard and organolithium reagents not only under batch conditions but also under continuous-flow conditions. Even with a simple pipet reactor packed with the heterogeneous catalyst, the enantioselective production of chiral diarylmethanols could be achieved through a continuous introduction of aldehydes and mixed titanium reagents generated from the organometallic precursors. The pipet reactor could be used repeatedly in different reactions without appreciable deterioration of the activity.

DOE Office of Scientific and Technical Information (OSTI.GOV)

King, W.A.; Kubas, G.J.

The present invention provides: a composition of the formula M{sup +x}(Ga(Y){sub 4}{sup {minus}}){sub x} where M is a metal selected from the group consisting of lithium, sodium, potassium, cesium, calcium, strontium, thallium, and silver, x is an integer selected from the group consisting of 1 or 2, each Y is a ligand selected from the group consisting of aryl, alkyl, hydride and halide with the proviso that at least one Y is a ligand selected from the group consisting of aryl, alkyl and halide; a composition of the formula (R){sub x}Q{sup +}Ga(Y){sub 4}{sup {minus}} where Q is selected from themore » group consisting of carbon, nitrogen, sulfur, phosphorus and oxygen, each R is a ligand selected from the group consisting of alkyl, aryl, and hydrogen, x is an integer selected from the group consisting of 3 and 4 depending upon Q, and each Y is a ligand selected from the group consisting of aryl, alkyl, hydride and halide with the proviso that at least one Y is a ligand selected from the group consisting of aryl, alkyl and halide; an ionic polymerization catalyst composition including an active cationic portion and a gallium based weakly coordinating anion; and bridged anion species of the formula M{sup +x}{sub y}[X(GaY{sub 3}){sub z}]{sup {minus}y}{sub x} where M is a metal selected from the group consisting of lithium, sodium, potassium, magnesium, cesium, calcium, strontium, thallium, and silver, x is an integer selected from the group consisting of 1 or 2, X is a bridging group between two gallium atoms, y is an integer selected from the group consisting 1 and 2, z is an integer of at least 2, each Y is a ligand selected from the group consisting of aryl, alkyl, hydride and halide with the proviso that at least one Y is a ligand selected from the group consisting of aryl, alkyl and halide.« less

Gallium based low-interaction anions

DOEpatents

King, Wayne A.; Kubas, Gregory J.

2000-01-01

The present invention provides: a composition of the formula M.sup.+x (Ga(Y).sub.4.sup.-).sub.x where M is a metal selected from the group consisting of lithium, sodium, potassium, cesium, calcium, strontium, thallium, and silver, x is an integer selected from the group consisting of 1 or 2, each Y is a ligand selected from the group consisting of aryl, alkyl, hydride and halide with the proviso that at least one Y is a ligand selected from the group consisting of aryl, alkyl and halide; a composition of the formula (R).sub.x Q.sup.+ Ga(Y).sub.4.sup.- where Q is selected from the group consisting of carbon, nitrogen, sulfur, phosphorus and oxygen, each R is a ligand selected from the group consisting of alkyl, aryl, and hydrogen, x is an integer selected from the group consisting of 3 and 4 depending upon Q, and each Y is a ligand selected from the group consisting of aryl, alkyl, hydride and halide with the proviso that at least one Y is a ligand selected from the group consisting of aryl, alkyl and halide; an ionic polymerization catalyst composition including an active cationic portion and a gallium based weakly coordinating anion; and bridged anion species of the formula M.sup.+x.sub.y [X(Ga(Y.sub.3).sub.z ].sup.-y.sub.x where M is a metal selected from the group consisting of lithium, sodium, potassium, magnesium, cesium, calcium, strontium, thallium, and silver, x is an integer selected from the group consisting of 1 or 2, X is a bridging group between two gallium atoms, y is an integer selected from the group consisting 1 and 2, z is an integer of at least 2, each Y is a ligand selected from the group consisting of aryl, alkyl, hydride and halide with the proviso that at least one Y is a ligand selected from the group consisting of aryl, alkyl and halide.

Iron- and cobalt-catalyzed arylation of azetidines, pyrrolidines, and piperidines with Grignard reagents.

PubMed

Barré, Baptiste; Gonnard, Laurine; Campagne, Rémy; Reymond, Sébastien; Marin, Julien; Ciapetti, Paola; Brellier, Marie; Guérinot, Amandine; Cossy, Janine

2014-12-05

Iron- and cobalt-catalyzed cross-couplings between iodo-azetidines, -pyrrolidines, -piperidines, and Grignard reagents are disclosed. The reaction is efficient, cheap, chemoselective and tolerates a large variety of (hetero)aryl Grignard reagents.

Visible-light-driven Photocatalytic N-arylation of Imidazole Derivatives and Arylboronic Acids on Cu/graphene catalyst

PubMed Central

Cui, Yan-Li; Guo, Xiao-Ning; Wang, Ying-Yong; Guo, Xiang-Yun

2015-01-01

N-aryl imidazoles play an important role as structural and functional units in many natural products and biologically active compounds. Herein, we report a photocatalytic route for the C-N cross-coupling reactions over a Cu/graphene catalyst, which can effectively catalyze N-arylation of imidazole and phenylboronic acid, and achieve a turnover frequency of 25.4 h−1 at 25 oC and the irradiation of visible light. The enhanced catalytic activity of the Cu/graphene under the light irradiation results from the localized surface plasmon resonance of copper nanoparticles. The Cu/graphene photocatalyst has a general applicability for photocatalytic C-N, C-O and C-S cross-coupling of arylboronic acids with imidazoles, phenols and thiophenols. This study provides a green photocatalytic route for the production of N-aryl imidazoles. PMID:26189944

One-pot palladium-catalyzed synthesis of sulfonyl fluorides from aryl bromides† †Electronic supplementary information (ESI) available: Experimental details and supporting characterisation data. See DOI: 10.1039/c6sc03924c Click here for additional data file.

PubMed Central

Davies, Alyn T.; Curto, John M.

2017-01-01

A mild, efficient synthesis of sulfonyl fluorides from aryl and heteroaryl bromides utilizing palladium catalysis is described. The process involves the initial palladium-catalyzed sulfonylation of aryl bromides using DABSO as an SO2 source, followed by in situ treatment of the resultant sulfinate with the electrophilic fluorine source NFSI. This sequence represents the first general method for the sulfonylation of aryl bromides, and offers a practical, one-pot alternative to previously described syntheses of sulfonyl fluorides, allowing rapid access to these biologically important molecules. Excellent functional group tolerance is demonstrated, with the transformation successfully achieved on a number of active pharmaceutical ingredients, and their precursors. The preparation of peptide-derived sulfonyl fluorides is also demonstrated. PMID:28451264

Mechanism of action for the cytotoxic effects of the nitric oxide prodrug JS-K in murine erythroleukemia cells.

PubMed

Kaczmarek, Monika Z; Holland, Ryan J; Lavanier, Stephen A; Troxler, Jami A; Fesenkova, Valentyna I; Hanson, Charlotte A; Cmarik, Joan L; Saavedra, Joseph E; Keefer, Larry K; Ruscetti, Sandra K

2014-03-01

The nitric oxide (NO) prodrug JS-K, a promising anti-cancer agent, consists of a diazeniumdiolate group necessary for the release of NO as well as an arylating ring. In this study, we research the mechanism by which JS-K kills a murine erythroleukemia cell line and determine the roles of NO and arylation in the process. Our studies indicate that JS-K inhibits the PI 3-kinase/Akt and MAP kinase pathways. This correlates with the activation of the tumor suppressor FoxO3a and increased expression of various caspases, leading to apoptosis. The arylating capability of JS-K appears to be sufficient for inducing these biological effects. Overall, these data suggest that JS-K kills tumor cells by arylating and inactivating signaling molecules that block the activation of a tumor suppressor. Published by Elsevier Ltd.

Novel structural hybrids of pyrazolobenzothiazines with benzimidazoles as cholinesterase inhibitors.

PubMed

Aslam, Sana; Zaib, Sumera; Ahmad, Matloob; Gardiner, John M; Ahmad, Aqeel; Hameed, Abdul; Furtmann, Norbert; Gütschow, Michael; Bajorath, Jürgen; Iqbal, Jamshed

2014-05-06

Two series of novel pyrazolobenzothiazine-based hybrid compounds were efficiently synthesized starting from saccharin sodium salt. Pyrazolo[4,3-c][1,2]benzothiazine scaffolds were N-arylated by using p-fluorobenzaldehyde, followed by the incorporation of a benzimidazole or similar ring systems by treatment with arylenediamines. These phenylene-connected hybrid compounds were investigated as potential inhibitors of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). Compounds 12d and 12k were the most potent AChE inhibitors with IC50 values of 11 and 13 nM, respectively, while 6j (IC50 = 17 nM) proved to be the most active inhibitor against BuChE with remarkable selectivity for BuChE over AChE. Molecular docking studies were also performed on human AChE and BuChE to suggest possible binding modes in which the inhibitor's extended structure is accommodated along the active site gorge of both enzymes. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

Tetrahydrofuran Calpha-tetrasubstituted amino acids: two consecutive beta-turns in a crystalline linear tripeptide.

PubMed

Maity, Prantik; Zabel, Manfred; König, Burkhard

2007-10-12

The synthesis of tetrahydrofuran Calpha-tetrasubstituted amino acids (TAAs) and their effect on the conformation in small peptides are reported. The synthesis starts from the protein amino acid methionine, which is protected at the C and N terminus and converted into the corresponding sulfonium salt by alkylation. Simple base treatment in the presence of an aryl aldehyde leads to the formation of tetrahydrofuran tetrasubstituted Calpha-amino acids in a highly diastereoselective (trans/cis ratio up to 97:3) reaction with moderate to good yields (35-78%) depending on the aldehyde used. Palladium-catalyzed coupling reactions allow a subsequent further functionalization of the TAA. The R,S,S-TAA-Ala dipeptide amide adopts a beta-turn type I conformation, whereas its S,R,S isomer does not. The R,S,S-Gly-TAA-Ala tripeptide amide shows in the solid state and in solution a conformation of two consecutive beta-turn type III structures, stabilized by i+3-->i intramolecular hydrogen bonds.