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https://www.readbyqxmd.com/read/28734151/magnetically-recyclable-reduced-graphene-oxide-nanosheets-magnetite-palladium-aerogel-with-superior-catalytic-activity-and-reusability
#1
Yan Feng, Hui Zhang, Baifu Xin, Jie Wu
A two-step method was employed to synthesize reduced graphene oxide nanosheets/magnetite-palladium (rGSs/Fe3O4-Pd) aerogel, with excellent catalytic activity and recyclability. Firstly, graphene oxide nanosheet (GS) hydrogels were formed by the self-assembly of GSs during the hydrothermal process. Meanwhile, hematite (α-Fe2O3) and Pd nanoparticles (NPs) were synthesized and anchored onto the surface of the hydrogel. During heat-treatment, GSs were reduced to rGSs, while nonmagnetic α-Fe2O3NPs were converted to magnetic Fe3O4 NPs...
July 14, 2017: Journal of Colloid and Interface Science
https://www.readbyqxmd.com/read/28731717/hydrogen-bond-direction-enables-palladium-catalyzed-branch-and-enantioselective-allylic-aminations-and-beyond
#2
Ya-Ni Wang, Bao-Cheng Wang, Mao-Mao Zhang, Xiao-Wen Gao, Tian-Ren Li, Liang-Qiu Lu, Wen-Jing Xiao
The palladium-catalyzed branch- and enantioselective allylic amination of vinyl benzoxazinones was accomplished through controlling the hydrogen bond direction. This protocol provides a rapid and efficient route for synthesizing an important building block, chiral amino alkene, from widely available aliphatic amines in 64 → 99% yields with up to 99% ee. Furthermore, this transformation and the accompanying products were utilized to develop one-pot reactions through dual catalysis, affording chiral indolines with good synthetic efficiency and excellent enantiocontrol...
July 21, 2017: Organic Letters
https://www.readbyqxmd.com/read/28731701/a-model-for-the-enantioselectivity-of-asymmetric-intramolecular-alkylations-by-bis-quaternized-cinchona-alkaloid-derived-catalysts
#3
Cyndi Qixin He, Adam Simon, Yu-Hong Lam, Andrew P J Brunskill, Nobuyoshi Yasuda, Jiajing Tan, Alan M Hyde, Edward C Sherer, Kendall N Houk
A model for the stereoselectivity of intramolecular alkylations by N,N'-disubstituted cinchona alkaloids reported by Xiang et al. was established using density functional theory (DFT) calculations. The stereocontrol is based on the minimal distortion of the TS and catalyst required to achieve favorable electrostatic interactions in the favored TS. Counterions must be included in computational modeling of ion-paired catalysis in order to reproduce experimental enantioselectivity.
July 21, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28731593/synthesis-characterization-and-efficient-catalytic-activities-of-a-nickel-ii-porphyrin-remarkable-solvent-and-substrate-effects-on-participation-of-multiple-active-oxidants
#4
Cheal Kim, Hye Ahn, Jeong Bae, Min Kim, Kwon Bok, Ha Jeong, Suk Lee
A new nickel(II) porphyrin complex, [NiII(porp)] (1) has been synthesized and characterized by 1H NMR, 13C NMR and mass spectrometry analysis. This NiII porphyrin complex 1 catalyzed quantitatively the epoxidation reaction of a wide range of olefins with meta-chloroperoxybenzoic acid (MCPBA) under mild conditions. Reactivity and Hammett studies, H218O-exchange experiments, and the use of PPAA (peroxyphenylacetic acid) as a mechanistic probe suggested that participation of multiple active oxidants NiII-OOC(O)R 2, NiIV-Oxo 3, and NiIII-Oxo 4 in olefin epoxidation reactions by nickel porphyrin complex is markedly affected by solvent polarity and concentration and type of substrate...
July 21, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28731357/visible-light-induced-and-oxygen-promoted-oxidative-cyclization-of-aromatic-enamines-for-the-synthesis-of-quinolines-derivatives
#5
Xiao-Feng Xia, Guo-Wei Zhang, Dawei Wang, Su-Li Zhu
The dual transition metal-visible light photoredox catalysis for the synthesis of quinoline derivatives by using dioxygen as an oxygen source is developed. By using visible light, the direct oxidative cyclization of aromatic enamines with alkynes or alkenes can be achieved at mild conditions with an aide of copper or palladium catalysts, and a variety of multi-substituted quinoline derivatives could be obtained in good to moderate yields under mild reaction conditions.
July 21, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28731264/high-yield-synthesis-of-crystal-phase-heterostructured-4h-fcc-au-pd-core-shell-nanorods-for-electrocatalytic-ethanol-oxidation
#6
Ye Chen, Zhanxi Fan, Zhimin Luo, Xiaozhi Liu, Zhuangchai Lai, Bing Li, Yun Zong, Lin Gu, Hua Zhang
Noble-metal nanomaterials are attracting increasing research interest due to their promising applications in electrochemical catalysis, for example. Although great efforts have been devoted to the size-, shape-, and architecture-controlled synthesis of noble-metal nanomaterials, their crystal-phase-controlled synthesis is still in its infancy. Here, for the first time, this study reports high-yield synthesis of Au nanorods (NRs) with alternating 4H/face-centered cubic (fcc) crystal-phase heterostructures via a one-pot wet-chemical method...
July 21, 2017: Advanced Materials
https://www.readbyqxmd.com/read/28731229/macroscopic-polarization-enhancement-promoting-photo-and-piezoelectric-induced-charge-separation-and-molecular-oxygen-activation
#7
Hongwei Huang, Shuchen Tu, Chao Zeng, Tierui Zhang, A H Reshak, Yihe Zhang
We report that both efficient photo- and piezoelectric- induced molecular oxygen activation are achieved via macroscopic polarization enhancement on a noncentrosymmetric piezoelectric semiconductor BiOIO3. The replacement of V5+ ions for I5+ in IO3 polyhedra gives rise to strengthened macroscopic polarization of BiOIO3, which facilitates the charge separation in the photocatalytic and piezoelectric-catalytic process, and renders largely promoted photo- and piezoelectric induced reactive oxygen species (ROS) evolution, such as superoxide radicals (*O2-) and hydroxyl radicals (*OH)...
July 21, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28731109/the-preference-for-dual-gold-i-catalysis-in-the-hydro-alkoxylation-vs-phenoxylation-of-alkynes
#8
Èric Casals-Cruañas, Oscar F González-Belman, Pau Besalú-Sala, David J Nelson, Albert Poater
Dinuclear gold complexes and their use in catalysis have received significant recent attention, but there are few critical comparisons of mono- versus dual gold-catalysed pathways. Herein we study the hydroalkoxylation and hydrophenoxylation of alkynes using density functional theory calculations, and compare two possible mechanisms that have been proposed previously on the basis of theoretical and experimental studies, which unravel different preferences because of both the nature of the alkyne and alcohol and the non-innocent role of the counter-anion of a dual gold based catalyst...
July 21, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28730207/asymmetric-br%C3%A3-nsted-acid-catalysis-with-chiral-carboxylic-acids
#9
REVIEW
Chang Min, Daniel Seidel
Chiral Brønsted acids have found widespread applications as organocatalysts. Weakly acidic species such as diols and (thio)ureas, typically classified as hydrogen bonding catalysts, as well as stronger phosphoric acids, have proven to be highly effective in catalyzing a wide range of asymmetric transformations. In contrast, the use of chiral carboxylic acids as Brønsted acid catalysts is much less developed but has recently garnered increased attention. Given that their pKa's generally lie between those of typical hydrogen bond donors and chiral phosphoric acids, chiral carboxylic acids provide the opportunity to activate a different set of substrates requiring intermediate catalyst acidity...
July 21, 2017: Chemical Society Reviews
https://www.readbyqxmd.com/read/28729757/protein-protein-interfaces-are-vdw-dominant-with-selective-h-bonds-and-or-electrostatics-towards-broad-functional-specificity
#10
Christina Nilofer, Anshul Sukhwal, Arumugam Mohanapriya, Pandjassarame Kangueane
Several catalysis, cellular regulation, immune function, cell wall assembly, transport, signaling and inhibition occur through Protein- Protein Interactions (PPI). This is possible with the formation of specific yet stable protein-protein interfaces. Therefore, it is of interest to understand its molecular principles using structural data in relation to known function. Several interface features have been documented using known X-ray structures of protein complexes since 1975. This has improved our understanding of the interface using structural features such as interface area, binding energy, hydrophobicity, relative hydrophobicity, salt bridges and hydrogen bonds...
2017: Bioinformation
https://www.readbyqxmd.com/read/28729736/the-relationship-between-folding-and-activity-in-ureg-an-intrinsically-disordered-enzyme
#11
Marta Palombo, Alessio Bonucci, Emilien Etienne, Stefano Ciurli, Vladimir N Uversky, Bruno Guigliarelli, Valérie Belle, Elisabetta Mileo, Barbara Zambelli
A growing body of literature on intrinsically disordered proteins (IDPs) led scientists to rethink the structure-function paradigm of protein folding. Enzymes are often considered an exception to the rule of intrinsic disorder (ID), believed to require a unique structure for catalysis. However, recent studies revealed the presence of disorder in several functional native enzymes. In the present work, we address the importance of dynamics for catalysis, by investigating the relationship between folding and activity in Sporosarcina pasteurii UreG (SpUreG), a P-loop GTPase and the first discovered native ID enzyme, involved in the maturation of the nickel-containing urease...
July 20, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28728754/copper-based-reactions-in-analyte-responsive-fluorescent-probes-for-biological-applications
#12
Ho Yu Au-Yeung, Chung Ying Chan, Ka Yan Tong, Zuo Hang Yu
Copper chemistry has been capitalized on in a wide spectrum of biological events. The central importance of copper in biology lies in the diverse chemical reactivity of the redox-active transition metal ranging from electron transfer, small molecule binding and activation, to catalysis. In addition to its many different roles in natural biological systems, the diverse chemical reactivity of copper also represents a rich opportunity and resource to develop synthetic bioanalytical tools for the study of biologically important species and molecules...
July 4, 2017: Journal of Inorganic Biochemistry
https://www.readbyqxmd.com/read/28727454/a-route-to-substituted-furan-2-5h-ones-from-cyclo-alkenecarboxylic-acids-and-acrylates-via-c-h-activation
#13
You-Quan Zhu, Ting-Feng Han, Jing-Li He, Man Li, Jun-Xian Li, Kun Zhu
Under rhodium (III) catalysis, four kinds of cyclo-alkenecarboxylic acids successfully reacted with acrylates via direct activation of β-alkenyl C-H bond. The present protocol provides the facile and highly efficient synthesis of substituted furan-2(5H)-ones from readily available starting materials with moderate to good yields. In addition, their possible reaction mechanisms were also discussed.
July 20, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28727424/enantioselective-construction-of-tertiary-c-o-bond-via-allylic-substitution-of-vinylethylene-carbonates-with-water-and-alcohols
#14
Ajmal Khan, Sardaraz Khan, Ijaz Khan, Can Zhao, Yuxue Mao, Yan Chen, Yong Jian Zhang
An efficient method for the enantioselective construction of tertiary C-O bond via asymmetric allylic substitution of racemic vinylethylene carbonates with water and alcohols has been developed. Under the cooperative catalysis system of an in situ generated chiral palladium complex and boron reagent in mild conditions, the process allowed rapid access to valuable tertiary alcohols and ethers in high yields with complete regioselectivities and high enantioselectivities. This protocol represented the first example of direct enantioselective formation of tertiary C-O bond with water as an oxygen donor...
July 20, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28726962/recent-advances-in-functional-mesoporous-graphitic-carbon-nitride-mpg-c3n4-polymers
#15
REVIEW
Shaodong Sun, Shuhua Liang
Mesoporous micro-/nanostructures acting as supports for catalysts or used directly in catalysis reactions generally show fascinating performances that could lead to great potential for application. In the past few decades, extensive efforts have been devoted to the exploration and enrichment of graphitic carbon nitride (g-C3N4) based research. Especially, mesoporous g-C3N4 (mpg-C3N4) with controllable porosity and electronic/atomic structure can bring to bear unique physicochemical properties and has been widely applied in the fields of photocatalysis, adsorbents, sensors and chemical templates...
July 20, 2017: Nanoscale
https://www.readbyqxmd.com/read/28726948/an-expeditious-method-to-synthesize-difluoroboron-complexes-of-%C3%AE-keto-amides-from-%C3%AE-keto-nitriles-and-bf3%C3%A2-oet2
#16
Chuangchuang Xu, Jiaxi Xu
A convenient and expeditious strategy to synthesize difluoroboron complexes of β-keto amides has been developed from β-keto nitriles and BF3·OEt2. BF3·OEt2 serves as both a BF2 source and a Lewis acid catalyst in the synthetic strategy. The formation mechanism of the difluoroboron complexes from β-keto nitriles and BF3·OEt2 was proposed. The difluoroboron complexes can be further converted into β-keto amides by treatment with sodium acetate. The strategy features advantages such as a wide substrate scope, non-metal catalysis, and easy operation...
July 20, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28726794/biological-iron-sulfur-storage-in-a-thioferrate-protein-nanoparticle
#17
Brian J Vaccaro, Sonya M Clarkson, James F Holden, Dong-Woo Lee, Chang-Hao Wu, Farris L Poole Ii, Julien J H Cotelesage, Mark J Hackett, Sahel Mohebbi, Jingchuan Sun, Huilin Li, Michael K Johnson, Graham N George, Michael W W Adams
Iron-sulfur clusters are ubiquitous in biology and function in electron transfer and catalysis. They are assembled from iron and cysteine sulfur on protein scaffolds. Iron is typically stored as iron oxyhydroxide, ferrihydrite, encapsulated in 12 nm shells of ferritin, which buffers cellular iron availability. Here we have characterized IssA, a protein that stores iron and sulfur as thioferrate, an inorganic anionic polymer previously unknown in biology. IssA forms nanoparticles reaching 300 nm in diameter and is the largest natural metalloprotein complex known...
July 20, 2017: Nature Communications
https://www.readbyqxmd.com/read/28726427/rh-iii-catalyzed-c-h-activation-cyclization-of-benzamides-and-diazonaphthalen-2-1h-ones-for-synthesis-of-lactones
#18
Renjie Chen, Sunliang Cui
A Rh(III)-catalyzed C-H activation/cyclization of benzamides and diazonaphthalen-2(1H)-ones for synthesis of lactones has been developed. In the presence of Rh(III) catalysis, the benzamides would form rhodacycle species and could be trapped by diazonaphthalen-2(1H)-ones for arylation, and the following intramolecular lactonization would rapidly furnish the products. Thus, the diazonaphthalen-2(1H)-ones were first revealed as a lactonization component in Rh(III)-catalysis, while the kinetic isotope effect study was conducted and a plausible reaction mechanism was proposed...
July 20, 2017: Organic Letters
https://www.readbyqxmd.com/read/28726416/atropisomeric-chiral-diiododienes-z-z-2-3-di-1-iodoalkylidene-tetralins-synthesis-enantiomeric-resolution-and-application-in-asymmetric-catalysis
#19
Masamichi Ogasawara, Hirotaka Sasa, Hao Hu, Yuta Amano, Hikaru Nakajima, Naoko Takenaga, Kiyohiko Nakajima, Yasuyuki Kita, Tamotsu Takahashi, Toshifumi Dohi
The C2-symmetric tetralin-fused 1,4-diiodo-1,3-butadiene derivatives, (Z,Z)-2,3-di(1-iodoalkylidene)tetralin 1a-c, are atropisomeric and can be resolved into the two persistent axially chiral enantiomers by HPLC on a chiral stationary phase. The enantiomerically pure compounds can serve as chiral organocatalysts for dearomatizing spirolactonization to show good performance in up to 73% ee.
July 20, 2017: Organic Letters
https://www.readbyqxmd.com/read/28726316/deprotonation-states-of-the-two-active-site-water-molecules-regulate-the-binding-of-protein-phosphatase-5-with-its-substrate-a-molecular-dynamics-study
#20
Lingyun Wang, Feng Yan
Protein phosphatase 5 (PP5), mainly localized in human brain, can dephosphorylate tau protein whose high level of phosphorylation is related to Alzheimer's disease. Similar to other protein phosphatases, PP5 has a conserved motif in the catalytic domain that contains two binding sites for manganese (Mn(2+) ) ions. Structural data indicate that two active site water molecules, one bridging the two Mn(2+) ions and the other terminally coordinated with one of the Mn(2+) ions (Mn1), are involved in catalysis. Recently, a density functional theory study revealed that the two water molecules can be both deprotonated to keep a neutral active site for catalysis...
July 20, 2017: Protein Science: a Publication of the Protein Society
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