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Gold catalysis

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https://www.readbyqxmd.com/read/28650660/ph-triggered-recovery-and-reuse-of-thiolated-poly-acryl-acid-functionalized-gold-nanoparticles-with-applications-in-colloidal-catalysis
#1
Siyam M Ansar, Benjamin D Fellows, Patrick Mispireta, O Thompson Mefford, Christopher L Kitchens
Thiolated poly(acrylic acid) (PAA-SH) functionalized gold nanoparticles were explored as a colloidal catalyst with potential application as a recoverable catalyst where the PAA provides pH-responsive dispersibility and phase transfer capability between aqueous and organic media. This system demonstrates complete nanoparticle recovery and redispersion over multiple reaction cycles without changes in nanoparticle morphology or reduction in conversion. The catalytic activity (rate constant) was reduced in subsequent reactions when recovery by aggregation was employed, despite unobservable changes in morphology or dispersability...
June 26, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/28646720/nanoporous-gold-based-microbial-biosensor-for-direct-determination-of-sulfide
#2
Zhuang Liu, Hanyue Ma, Huihui Sun, Rui Gao, Honglei Liu, Xia Wang, Ping Xu, Luying Xun
Environmental pollution caused by sulfide compounds has become a major problem for public health. Hence, there is an urgent need to explore a sensitive, selective, and simple sulfide detection method for environmental monitoring and protection. Here, a novel microbial biosensor was developed using recombinant Escherichia coli BL21 (E. coli BL21) expressing sulfide:quinone oxidoreductase (SQR) for sulfide detection. As an important enzyme involved in the initial step of sulfide metabolism, SQR oxidizes sulfides to polysulfides and transfers electrons to the electron transport chain...
June 20, 2017: Biosensors & Bioelectronics
https://www.readbyqxmd.com/read/28629040/3-aminopropyltrimethoxysilane-mediated-solvent-induced-synthesis-of-gold-nanoparticles-for-biomedical-applications
#3
Prem C Pandey, Gunjan Pandey, Alain Walcarius
The effect of acetone on 3-aminopropyltrimethoxysilane (3-APTMS) mediated synthesis of gold nanoparticles (AuNPs) in polar protic, polar aprotic and non polar solvents specifically water, acetone and chloroform has been studied. The findings revealed that acetone promotes the formation of siloxane polymer in chloroform and acetone solvents, but not in water, while AuNPs are formed in all cases. The bifunctional nature of 3-APTMS [NH2(CH2)3Si(OMe)3] controls the formation of siloxane polymer through hydrolysis and condensation of trimethoxysilyl group whereas the amine moieties are likely to form imine linkage, which are involved in the synthesis of gold nanoparticles...
October 1, 2017: Materials Science & Engineering. C, Materials for Biological Applications
https://www.readbyqxmd.com/read/28604863/dual-gold-photoredox-catalyzed-bis-arylative-cyclization-of-chiral-homopropargyl-sulfonamides-with-diazonium-salts-rapid-access-to-enantioenriched-2-3-dihydropyrroles
#4
Ze-Shu Wang, Tong-De Tan, Cai-Ming Wang, Ding-Qiang Yuan, Te Zhang, Pengfei Zhu, Chunyin Zhu, Jin-Mei Zhou, Long-Wu Ye
A novel dual gold/photoredox-catalyzed bis-arylative cyclization of chiral homopropargyl sulfonamides with diazonium salts has been developed, allowing the facile synthesis of various enantioenriched 2,3-dihydropyrroles in generally moderate to good yields with excellent enantioselectivities under very mild conditions without using any strong oxidants. The reaction is proposed to undergo an Au(I)/Au(III) redox cycle promoted by visible-light photoredox catalysis.
June 22, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28603854/gold-redox-catalysis-through-base-initiated-diazonium-decomposition-toward-alkene-alkyne-and-allene-activation
#5
Xiaodong Shi, Boliang Dong, Haihui Peng, Stephen Motika
The discovery of photo-assisted 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 photo-free condition has been developed through Lewis base induced diazonium activation...
June 12, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28603606/synthesis-and-properties-of-magnetic-optical-core-shell-nanoparticles
#6
Elyahb Allie Kwizera, Elise Chaffin, Yongmei Wang, Xiaohua Huang
Due to their high integrity, facile surface chemistry, excellent stability, and dual properties from the core and shell materials, magnetic-plasmonic core-shell nanoparticles are of great interest across a number of science, engineering and biomedical disciplines. They are promising for applications in a broad range of areas including catalysis, energy conversion, biological separation, medical imaging, disease detection and treatment. The technological applications have driven the need for high quality nanoparticles with well controlled magnetic and optical properties...
March 19, 2017: RSC Advances
https://www.readbyqxmd.com/read/28598637/access-to-benzo-a-carbazoles-and-indeno-1-2-c-quinolines-by-a-gold-i-catalyzed-tunable-domino-cyclization-of-difunctional-1-2-diphenylethynes
#7
Xiaoshi Peng, Lifeng Zhu, Yuqian Hou, Yadong Pang, Yangming Li, Jiayue Fu, Lu Yang, Bin Lin, Yongxiang Liu, Maosheng Cheng
The cyclization order of the difunctional 1,2-diphenylethynes was precisely tuned under the catalysis of gold by changing the nitrogen substitution of the substrates, leading to the facile preparation of benzo[a]carbazole and indeno[1,2-c]quinoline derivatives. The mechanisms of these domino cyclizations were probed by control experiments, and an insight into the selectivity of the cyclization was gained by density functional theory (DFT) calculations. This research represents a unified and common method to access benzo[a]carbazoles and indeno[1,2-c]quinolines...
June 9, 2017: Organic Letters
https://www.readbyqxmd.com/read/28590758/cross-coupling-reactions-of-aryldiazonium-salts-with-allylsilanes-under-merged-gold-visible-light-photoredox-catalysis
#8
Manjur O Akram, Pramod S Mali, Nitin T Patil
A method for the cross-coupling reactions of aryldiazonium salts with trialkylallylsilanes via merged gold/photoredox catalysis is described. The reaction is proposed to proceed through a photoredox-promoted generation of an electrophilic arylgold(III) intermediate that undergoes transmetalation with allyltrimethylsilane to form allylarenes.
June 7, 2017: Organic Letters
https://www.readbyqxmd.com/read/28571532/rapid-access-to-oxazine-fused-furocoumarins-and-in-vivo-and-in-silico-studies-of-theirs-biological-activity
#9
Alla V Lipeeva, Dmitry S Baev, Margarita P Dolgikh, Tatijana G Tolstikova, Elvira E Shults
BACKGROUND: The synthesis of 1,2-oxazine-fused linear furocoumarins was performed involving the transition metal catalysis reaction of plant coumarin oreoselone derivatives. OBJECTIVE AND METHODS: The Pd-catalyzed desulfonative cross-coupling reactions of 2-(tosyl)oreoselone with terminal alkynes and the successive treatment of the obtained 2-(arylethynyl)furocoumarins with an excess of hydroxylamine gave the expected (Z,E)-3-(hydroxyimino)-2-(arylethynyl)furocoumarins with an (Z:E) ratio of about 1:0...
May 31, 2017: Medicinal Chemistry
https://www.readbyqxmd.com/read/28557174/polyunsaturated-c-glycosidic-4-hydroxy-2-pyrone-derivatives-total-synthesis-shows-that-putative-orevactaene-is-likely-identical-with-epipyrone%C3%A2-a
#10
Johannes Preindl, Saskia Schulthoff, Conny Wirtz, Julia Lingnau, Alois Fürstner
Orevactaene and epipyrone A were previously thought to comprise the same polyunsaturated tail but notably different C-glycosylated 4-hydroxy-2-pyrone head groups. Total synthesis now shows that the signature bicyclic framework assigned to orevactaene is a chimera; the compound is almost certainly identical with epipyrone A, whose previously unknown stereochemistry has also been established during this study. Key to success was the ready formation of the bicyclic core of putative orevactaene by a sequence of two alkyne cycloisomerization reactions using tungsten and gold catalysis...
May 30, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28553527/dual-gold-and-photoredox-catalysed-c-h-activation-of-arenes-for-aryl-aryl-cross-couplings
#11
V Gauchot, D R Sutherland, A-L Lee
A mild and fully catalytic aryl-aryl cross coupling via gold-catalysed C-H activation has been achieved by merging gold and photoredox catalysis. The procedure is free of stoichiometric oxidants and additives, which were previously required in gold-catalysed C-H activation reactions. Exploiting dual gold and photoredox catalysis confers regioselectivity via the crucial gold-catalysed C-H activation step, which is not present in the unselective photocatalysis-only counterpart.
April 1, 2017: Chemical Science
https://www.readbyqxmd.com/read/28553495/dual-gold-and-photoredox-catalysis-visible-light-mediated-intermolecular-atom-transfer-thiosulfonylation-of-alkenes
#12
Haoyu Li, Cuicui Shan, Chen-Ho Tung, Zhenghu Xu
Regioselective difunctionalization of alkenes has attracted significant attention from synthetic chemists and has the advantage of introducing diverse functional groups into vicinal carbons of common alkene moieties in a single operation. Herein, we report an unprecedented intermolecular atom transfer thiosulfonylation reaction of alkenes by combining gold catalysis and visible-light photoredox catalysis. A trifluoromethylthio group (SCF3) and other functionalized thio groups together with a sulfonyl group were regioselectively introduced into alkenes in the most atom economical manner...
April 1, 2017: Chemical Science
https://www.readbyqxmd.com/read/28535055/ionic-liquid-anion-controlled-nanoscale-gold-morphology-grown-at-a-liquid-interface
#13
Nakara Bhawawet, Jeremy B Essner, Durgesh V Wagle, Gary A Baker
Two different ionic liquids comprising the tetrabutylphosphonium cation ([P4444]) paired with the strongly coordinating anions 6-aminocaproate ([6-AC]) or taurinate ([tau]) were prepared and employed in an aqueous/organic liquid bilayer system to generate nanoscale gold by Au(OH)4(-) photoreduction. Generally, as the concentration of ionic liquid in the organic phase was increased, the resulting quasi-spherical gold nanoparticles were smaller in size and presented less aggregation, leading to marked increases in the catalytic efficiency for 4-nitrophenol reduction using borohydride...
June 8, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/28515662/tempo-functionalized-c60-fullerene-deposited-on-gold-surface-for-catalytic-oxidation-of-selected-alcohols
#14
Piotr Piotrowski, Joanna Pawłowska, Jarosław Grzegorz Sadło, Renata Bilewicz, Andrzej Kaim
C60TEMPO10 catalytic system linked to a microspherical gold support through a covalent S-Au bond was developed. The C60TEMPO10@Au composite catalyst had a particle size of 0.5-0.8 μm and was covered with the fullerenes derivative of 2.3 nm diameter bearing ten nitroxyl groups; the organic film showed up to 50 nm thickness. The catalytic composite allowed for the oxidation under mild conditions of various primary and secondary alcohols to the corresponding aldehyde and ketone analogues with efficiencies as high as 79-98%, thus giving values typical for homogeneous catalysis, while retaining at the same time all the advantages of heterogeneous catalysis, e...
2017: Journal of Nanoparticle Research: An Interdisciplinary Forum for Nanoscale Science and Technology
https://www.readbyqxmd.com/read/28513536/resonance-rayleigh-scattering-and-sers-spectral-detection-of-trace-hg-ii-based-on-the-gold-nanocatalysis
#15
Huixiang Ouyang, Chongning Li, Qingye Liu, Guiqing Wen, Aihui Liang, Zhiliang Jiang
Mercury (Hg) is a heavy metal pollutant, there is an urgent need to develop simple and sensitive methods for Hg(II) in water. In this article, a simple and sensitive resonance Rayleigh scattering (RRS) method was developed for determination of 0.008-1.33 µmol/L Hg, with a detection limit of 0.003 μmol/L, based on the Hg(II) regulation of gold nanoenzyme catalysis on the HAuCl₄-H₂O₂ to form gold nanoparticles (AuNPs) with an RRS peak at 370 nm. Upon addition of molecular probes of Victoria blue B (VBB), the surface-enhanced Raman scattering (SERS) peak linearly decreased at 1612 cm(-1) with the Hg(II) concentration increasing in the range of 0...
May 17, 2017: Nanomaterials
https://www.readbyqxmd.com/read/28508542/dynamic-self-assembly-of-homogenous-microcyclic-structures-controlled-by-a-silver-coated-nanopore
#16
Rui Gao, Yao Lin, Yi-Lun Ying, Xiao-Yuan Liu, Xin Shi, Yong-Xu Hu, Yi-Tao Long, He Tian
The self-assembly of nanoparticles is a challenging process for organizing precise structures with complicated and ingenious structures. In the past decades, a simple, high-efficiency, and reproducible self-assembly method from nanoscale to microscale has been pursued because of the promising and extensive application prospects in bioanalysis, catalysis, photonics, and energy storage. However, microscale self-assembly still faces big challenges including improving the stability and homogeneity as well as pursuing new assembly methods and templates for the uniform self-assembly...
May 16, 2017: Small
https://www.readbyqxmd.com/read/28507665/versatile-routes-for-synthesis-of-diarylamines-through-acceptorless-dehydrogenative-aromatization-catalysis-over-supported-gold-palladium-bimetallic-nanoparticles
#17
Kento Taniguchi, Xiongjie Jin, Kazuya Yamaguchi, Kyoko Nozaki, Noritaka Mizuno
Diarylamines are an important class of widely utilized chemicals, and development of diverse procedures for their synthesis is of great importance. Herein, we have successfully developed novel versatile catalytic procedures for the synthesis of diarylamines through acceptorless dehydrogenative aromatization. In the presence of a gold-palladium alloy nanoparticle catalyst (Au-Pd/TiO2), various symmetrically substituted diarylamines could be synthesized starting from cyclohexylamines. The observed catalysis of Au-Pd/TiO2 was heterogeneous in nature and Au-Pd/TiO2 could be reused several times without severe loss of catalytic performance...
March 1, 2017: Chemical Science
https://www.readbyqxmd.com/read/28502180/metal-nanoparticle-growth-within-clay-polymer-nacre-inspired-materials-for-improved-catalysis-and-plasmonic-detection-in-complex-biofluids
#18
Eric H Hill, Christoph Hanske, Alexander Johnson, Luis Yate, Hans Jelitto, Gerold A Schneider, Luis M Liz-Marzán
Recent studies have shown that layered silicate clays can be used to form a nacre-like bioinspired layered structure with various polymer fillers, leading to composite films with good material strength, gas-barrier properties, and high loading capacity. We go one step further by in situ growing metal nanoparticles in nacre-like layered films based on layered silicate clays, which can be used for applications in plasmonic sensing and catalysis. The degree of anisotropy of the nanoparticles grown in the film can be controlled by adjusting the ratio of clay to polymer or gold to clay and reducing agent concentration, as well as silver overgrowth, which greatly enhances the surface enhanced Raman scattering activity of the composite...
May 24, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/28492626/alkynyl-sulfoxides-as-%C3%AE-sulfinyl-carbene-equivalents-gold-catalysed-oxidative-cyclopropanation
#19
Matthew J Barrett, Ghulam F Khan, Paul W Davies, Richard S Grainger
Alkynyl sulfoxides are shown to act as α-sulfinyl metallocarbene synthons under oxidative gold catalysis, enabling reactions that are not available from diazo-precursors. This strategy is exemplified in the synthesis of fused α-sulfinyl cyclopropanes.
May 11, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28485941/soft-ultraviolet-uv-photopatterning-and-metallization-of-self-assembled-monolayers-sams-formed-from-the-lipoic-acid-ester-of-%C3%AE-hydroxy-1-acetylpyrene-the-generality-of-acid-catalyzed-removal-of-thiol-on-gold-sams-using-soft-uv-light
#20
Laurynas Pukenas, Panida Prompinit, Boda Nishitha, Daniel J Tate, N D Pradeep Singh, Christoph Wälti, Stephen D Evans, Richard J Bushby
Under a layer of 0.1 M HCl in isopropanol, soft ultraviolet (UV) (365 nm) photolysis of the thiol-on-gold self-assembled monolayer (SAM) derived from the lipoic acid ester of α-hydroxy-1-acetylpyrene results in the expected removal of the acetylpyrene protecting group. When photolyzing through a mask, this can be used to produce a patterned surface and, at a controlled electrochemical potential, it is then possible to selectively and reversibly electrodeposit copper on the photolyzed regions. Rather surprisingly, under these photolysis conditions, there is not only the expected photodeprotection of the ester but also partial removal of the lipoic acid layer which has been formed...
May 19, 2017: ACS Applied Materials & Interfaces
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