- Ultrafine silver nanoparticles supported on a covalent carbazole framework as high-efficiency nanocatalysts for nitrophenol reduction
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A novel conjugated microporous polymer (CMP) material CZ-TEB was synthesized with a carbazole analogue and 1,3,5-triethynylbenzene. It possessed a high specific surface area, excellent thermal stability and layered-sheet morphology. Furthermore, ultrafine silver nanoparticles were successfully immobilized on CZ-TEB, thus preparing a nanocatalyst Ag0@CZ-TEB. To evaluate its catalytic performance, Ag0@CZ-TEB was exploited in the reduction reaction of nitrophenols, a family of priority pollutants. Ag0@CZ-TEB exhibited high catalytic ability, convenient recovery and excellent reusability. Strikingly, the normalized rate constant (knor) of the reduction reaction of 4-NP to 4-AP is as high as 21.49 mmol-1 s-1. This result shows a significant improvement over all previously reported work. We purposed to use a "capture-release" model to explain the high catalytic ability of Ag0@CZ-TEB. This explanation is supported by further experimental results that agree well with the "capture-release" model.
- Gong, Wei,Wu, Qianqian,Jiang, Guoxing,Li, Guangji
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Read Online
- Polymer-anchored [Fe(III)Azo] complex: An efficient reusable catalyst for oxidative bromination and multi-components reaction for the synthesis of spiropiperidine derivatives
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A heterogeneous catalyst was prepared by attaching Fe(III) into organically modified chloromethylated polytstyrene and characterized by AAS, IR, PXRD, TG-DTA, UV–Vis, and SEM studies. In presence of H2O2 and KBr as bromine source, the catalyst showed remarkably high conversion with para-selectivity towards the oxidative bromination reaction in acetic acid medium. The catalyst was also very active and highly efficient for the production of spiropiperidine derivatives through multi-component reaction in isopropyl alcohol at room temperature. The catalyst was not leached during the catalytic reactions, moreover, after five cycles the catalytic activity and selectivity of the catalyst were not decreased very significantly.
- Khatun, Resmin,Biswas, Surajit,Ghosh, Swarbhanu,Islam, Sk. Manirul
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- Zwitterionic Surfactant stabilized palladium nanoparticles as catalysts in aromatic nitro compound reductions
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Palladium nanoparticles (NPs) stabilized by ImS3-14, a zwitterionic surfactant structurally related to ionic liquids, are revealed here to be good catalysts for the reduction of a large number of substituted aromatic nitro compounds. Our mass spectrometry results are consistent with the formation of amino products in a direct route, where the aromatic nitro compounds are initially reduced to nitroso compounds, which are then reduced to the hydroxylamine derivatives and finally to the anilines. Activation parameters showed that for most Pd catalysts reported in the literature, the mechanism seems to be similar, with lower enthalpy of activation (ΔH?) being compensated by more negative entropy of activation (ΔS?). As a result, the reaction is thermally compensated and the rate constants for most reactions rather similar. Furthermore, Pd NPs stabilized by ImS3-14 showed efficient catalytic activities for the reduction of aromatic nitro compounds, with high conversion and good selectivity even using very low loadings of metal.
- Souza, Franciane D.,Fiedler, Haidi,Nome, Faruk
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p. 372 - 381
(2016/03/19)
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- Polymer-anchored Cu(II) complex as an efficient catalyst for selective and mild oxidation of sulfides and oxidative bromination reaction
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A new polymer-anchored Cu(II) complex has been tested for the oxidation of sulfides and in oxidative bromination reaction with hydrogen peroxide as oxidant. Sulfides have been selectively oxidized to corresponding sulfoxides in excellent yields and in presence of KBr as bromine source, organic substrates have been selectively converted to mono bromo substituted compounds. The polymer-anchored Cu(II) catalyst could be easily recovered by simple filtration and reused more than six times without appreciable loss of its initial activity. Graphical Abstract: [Figure not available: see fulltext.]
- Islam, Sk. M.,Roy, Anupam Singha,Mondal, Paramita,Salam, Noor,Paul, Sumantra
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p. 225 - 233
(2013/03/13)
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- Selective oxidation of sulfides and oxidative bromination of organic substrates catalyzed by polymer anchored Cu(II) complex
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A new polymer-anchored Cu(II) complex has been synthesized and characterized. The catalytic performance of the complex has been tested for the oxidation of sulfides and in oxidative bromination reaction with hydrogen peroxide as the oxidant. Sulfides have been selectively oxidized to the corresponding sulfoxides in excellent yields and in the presence of KBr as the bromine source, organic substrates have been selectively converted to mono bromo substituted compounds using polymer-anchored Cu(II) catalyst. This catalyst showed excellent catalytic activity, high selectivity, and recyclability. The polymer-anchored Cu(II) catalyst could be easily recovered by filtration and reused more than five times without appreciable loss of its initial activity.
- Islam,Roy, Anupam Singha,Mondal, Paramita,Tuhina, Kazi,Mobarak, Manir,Mondal, John
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supporting information; experimental part
p. 127 - 131
(2012/01/17)
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- Regioselective and high-yielding bromination of phenols and anilins using N-bromosaccharin and amberlyst-15
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A regioselective and facile conversion method for bromination of anilines and phenols using N-bromosaccharine in the presence of a catalytic amount of Amberlyst-15 lead to enhancement of the reaction rate and yielded brominated products in good to excellent yields and short reaction times.
- Baharfar,Alinezhad,Azimi,Salehian
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experimental part
p. 863 - 865
(2012/04/23)
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- Vilsmeier-haack bromination of aromatic compounds with KBr and N-bromosuccinimide under solvent-free conditions
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Bromination of aromatic hydrocarbons is triggered by Vilsmeier-Haack reagent [N,N-dimethyl formamide (DMF-POCl3 system)] in the presence of KBr or N-bromosuccinimide (NBS) under solvent-free conditions by grinding the reactants in a mortar with a pestle. The reactions afforded corresponding bromo derivatives in very good yield with high regioselectivity. The results are comparable with those obtained under reflux conditions. Copyright Taylor & Francis Group, LLC.
- Chakradhar,Roopa,Rajanna,Saiprakash
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experimental part
p. 1817 - 1824
(2009/10/02)
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- PYRROLIDINE DERIVATIVES AS ERK INHIBITORS
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Disclosed are the ERK inhibitors of Formula (1.0): and the pharmaceutically acceptable salts and solvates thereof. Q is a piperidine or piperazine ring that can have a bridge or a fused ring. The piperidine ring can have a double bond in the ring. All other substitutents are as defined herein. Also disclosed are methods of treating cancer using the compounds of Formula (1.0).
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Page/Page column 175-176
(2010/11/28)
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- Fused ring 4-oxopyrimidine derivative
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The present invention provides a compound represented by formula (I) below, or a pharmaceutically acceptable salt thereof, which, having histamine H3 receptor antagonist or inverse agonist activity, is useful in the prophylaxis or therapy of metabolic diseases, circulatory diseases, or nervous system diseases. [where, for example, Ar is a divalent group formed by eliminating two hydrogen atoms from benzene, X1 is a nitrogen atom, sulfur atom or oxygen atom, R1 is a 5- to 6-membered heteroaryl group, Ring A is a 5- to 6-membered heteroaryl ring, R2 and R3 are amino groups or alkylamino groups, and X2 is represented by formula (II): (where R4 and R5 are lower alkyl groups, and n is an integer from 2 to 4).]
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Page/Page column 62
(2008/06/13)
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- Hair colouring and conditioning compositions
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A hair colouring and conditioning composition comprising: (a) a hair colouring agent; and (b) a hair conditioning agent; wherein the composition provides an Average Combing Index Value of greater than 1.2 as measured by the Combing Technical Test Method. The products can provide excellent hair colouring together with excellent conditioning, reduced hair damage, brittleness and dryness, and is convenient and easy to use.
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- Hair conditioning compositions and their use in hair colouring compositions
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The present invention relates to a hair care composition comprising a aminofunctional polysiloxane having a specified average effective particle size which provides improved durable conditioning particularly when utilised in conjunction with a hair colouring composition.
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- Hydrolysis and Fe2+-induced Reduction of N-Aryl -O-pivaloylhydroxylamines: Aqueous Solution Chemistry of Model Carcinogens.
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The N-aryl-O-pivaloylhydroxylamines, 1a-d, which serve as models for the carcinogenic metabolites of aromatic amines, decompose in aqueous media by heterolysis of the N-O bond.Substituent effects on rates of reaction and products of the decomposition of 1a-c are entirely consistent with the intermediacy of a singlet nitrenium ion.The least reactive compound in the series N-(4-nitrophenyl)-O-pivaloylhydroxylamine (1d) yields 4-nitroaniline (2d) as its major decomposition product.This material may be formed through H radical abstraction by a triplet ion, but a nitrene reaction appears to be more likely.In the presence of Fe2+ 1a-d undergo rapid reduction to the corresponding anilines 2a-d.This reaction requires complexation of the ester with Fe2+ and proceeds with heterolysis of the N-O bond since nearly quantitative yields of pivalic acid are isolated.The radical cations 25a-d appear to be the most likely precursors to the reduction products.
- Novak, Michael,Lagerman, Robert K.
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p. 4762 - 4769
(2007/10/02)
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- Acid- and Base-Dependent Hydrolysis of N-(Sulfonatooxy)-3-bromoacetanilide: Involvement of N-(3-Bromophenyl)hydroxylamine-O-sulfonate
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N-(Sulfonatooxy)-3-bromoacetanilide (1e) undergoes hydrolysis at 80 deg C in the range pH 1.0-8.0 by acid- and base-dependent processes and by an uncatalyzed path.The uncatalyzed reaction exhibits the same characteristics as the uncatalyzed N-O bond-cleavage reactions of the more reactive N-(sulfonatooxy)acetanilides.The pH-dependent pathways involve the hydrolysis of 1e to form N-(3-bromophenyl)hydroxylamine-O-sulfonate (2).This material cannot be directly detected under the conditions of this study, but its existence can be inferred from product study and trapping data.Although 2 undergoes decomposition entirely by heterolytic N-O bond cleavage to yield nitrenium ion intermediate 14, a less reactive analogue of 2, N-(3-bromophenyl)-O-pivaloylhydroxylamine (4), apparently undergoes competitive homolytic and heterolytic N-O bond cleavage to yield both the arylamino radical 17 and the nitrenium ion 14.Both 2 and 4 serve as models for certain suspected carcinogenic metabolites of polycyclic aromatic amines and amides.
- Novak, Michael,Rovin, Lise H.,Pelecanou, Maria,Mulero, Julio J.,Lagerman, Robert K.
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p. 2002 - 2010
(2007/10/02)
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- Kinetics and Mechanisms of the Bamberger Rearrangement. Part 3. Rearrangement of Phenylhydroxylamines to p-Aminophenols in Aqueous Sulphuric Acid Solutions
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The rates of Bamberger-type rearrangement of phenylhydroxylamine (1a) and its derivatives (1b-d) to the corresponding p-aminophenols were determined in sulphuric acid solution.Plots if the pseudo-first-order rate constants against pH (or H0) indicate that the active species at +H2) which exists in equilibrium with the N-protonated species (ArN+H2OH), while the diprotonated species (ArN+H2O+H2) contributes significantly to the observed reaction rate at > 1.00 N (H0 region).The slope of Hammett plots (ρ) which was obtained by plotting kobs at 1.00 N against the Hammett ? values was -3.19.It was also established that the ΔS* values for the four substrates are all positive.These results suggest that the Bamberger rearrangement occurs by an SN1 mechanism and that the elimination of water from ArNHO+H2 is rate determining.
- Sone, Takaaki,Tokuda, Yuuji,Sakai, Toshimi,Shinkai, Seiji,Manabe, Osamu
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p. 298 - 302
(2007/10/02)
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