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Catalysis

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https://www.readbyqxmd.com/read/28222257/an-iron-ii-ylide-complex-as-a-masked-open-shell-iron-alkylidene-species-in-its-alkylidene-transfer-reactions-with-alkenes
#1
Jian Liu, Lianrui Hu, Lei Wang, Hui Chen, Liang Deng
Transition-metal alkylidenes are important reactive organometallic intermediates, and our current knowledge on them has been mainly restricted to those with closed-shell electronic configurations. In this study, we present the exploration on open-shell iron alkylidenes with a weak-field tripodal amido-phosphine-amido ligand. We found that a high-spin (amido-phosphine-amido)iron(II) complex can react with (p-tolyl)2CN2 to afford a high-spin (amido-ylide-amido)iron(II) complex, 2, which could transfer its alkylidene moiety to a variety of alkenes, either the electron-rich or electron-deficient ones, to form cyclopropane derivatives...
February 21, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28221698/monoprotected-l-amino-acid-l-mpaa-accelerated-bromination-chlorination-and-iodination-of-c-sp2-h-bonds-by-iridium-iii-catalysis
#2
Subban Kathiravan, Ian A Nicholls
Halogenated arenes are important structural motifs commonly found in biologically active molecules and used for a variety of transformations in organic synthesis. Herein, we report the mono-protected L-amino acid (L-MPAA) accelerated iridium(III) catalyzed halogenation of (hetero)anilides at room temperature. This reaction constitutes the first example of an iridium(III)/L-MPAA catalyzed general halogenation of (hetero)arenes through C(sp2)-H activation. Furthermore, we demonstrate the potential utility of our method through its use in the synthesis a quinolone derivative...
February 21, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28221384/switchable-divergent-asymmetric-synthesis-via-organocatalysis
#3
Gu Zhan, Wei Du, Ying-Chun Chen
The development of switchable chemo-, regio-, or diastereodivergent reactions, in which two or more structurally and stereogenically different types of chiral products could be produced efficiently from an identical set of starting materials under readily tunable catalytic conditions, is one of the ultimate goals in asymmetric catalysis. This tutorial review will focus on the application of a variety of chiral organic catalysts, including Lewis bases, and Brønsted bases and acids, in a diverse range of stereoselective reactions in a switchable manner...
February 21, 2017: Chemical Society Reviews
https://www.readbyqxmd.com/read/28221379/bridgehead-isomer-effects-in-bis-phosphido-bridged-diiron-hexacarbonyl-proton-reduction-electrocatalysts
#4
Ahibur Rahaman, Carolina Gimbert-Suriñach, Arne Ficks, Graham E Ball, Mohan Bhadbhade, Matti Haukka, Lee Higham, Ebbe Nordlander, Stephen B Colbran
The influence of the substitution, orientation and structure of the phosphido bridges in [Fe2(CO)6(μ-PR2)2] electrocatalysts of proton reduction has been studied. The isomers e,a-[Fe2(CO)6{μ-P(Ar)H}2] (1a(Ar): Ar = Ph, 2'-methoxy-1,1'-binaphthyl (bn')), e,e-[Fe2(CO)6{μ-P(Ar)H}2] (1b(Ar): Ar = Ph, bn') were isolated from reactions of iron pentacarbonyl and the corresponding primary phosphine, syntheses that also afforded the phosphinidene-capped tri-iron clusters, [Fe3(CO)9(μ-CO)(μ3-Pbn')] (2) and [Fe3(CO)9(μ3-PAr)2] (3(Ar), Ar = Ph, bn')...
February 21, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28221017/change-in-heat-capacity-for-enzyme-catalysis-determines-temperature-dependence-of-enzyme-catalyzed-rates
#5
Joanne K Hobbs, Wanting Jiao, Ashley D Easter, Emily J Parker, Louis A Schipper, Vickery L Arcus
No abstract text is available yet for this article.
February 21, 2017: ACS Chemical Biology
https://www.readbyqxmd.com/read/28220966/nhc-based-tri-organyl-zn-alkyl-cations-synthesis-structure-isomerization-for-improved-stability-and-use-in-co2-functionalization
#6
Samuel Dagorne
Tri-organyl and tri-coordinate N-heterocyclic carbene Zn-NHC alkyl cations (nNHC)2Zn-Me+ (nNHC = C2-bonded-IMes/-IDipp; 3+ and 4+) were first synthesized and structurally characterized via ionization of the corresponding neutral precursors (NHC)ZnMe2 with [Ph3C][B(C6F5)4] in the presence of 1 equiv. of free NHC. Cations 3+-5+ are the first Zn cations of the type Zn(C)(C')(C'')+ (C, C', C'' = σ-donor carbyl ligand). While cation (nIMes)2Zn-Me+ (3+) is stable, its sterically congested analogue (nIDipp)2Zn-Me+ (4+) readily undergoes a nNHC-to-aNHC isomerization in the presence of THF or IDipp to afford the more thermodynamically stable (aDipp)(nIDipp)Zn-Me+ (aIDipp = C5-bonded IDipp, 5+), reflecting the adaptable-to-sterics coordination chemistry of these cations for improved stability...
February 21, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28220774/proteasomes-caught-in-the-act
#7
Robert J Tomko
Although energy-dependent protein destruction by the proteasome has been known for over 30 years, how this intricate molecular machine uses ATP to power protein degradation has remained very poorly understood. In a recently published paper, Ding et al. present a snapshot of the proteasome mid-catalysis, yielding new and unexpected insights into the catalytic mechanism of this ATP-powered multisubunit machine.
February 21, 2017: Cell Research
https://www.readbyqxmd.com/read/28220164/an-efficient-noble-metal-free-supported-copper-catalyst-for-selective-nitrocyclohexane-hydrogenation-to-cyclohexanone-oxime
#8
Qian-Qian Zhang, Jing Dong, Yong-Mei Liu, Yong Cao, He-Yong He, Yang-Dong Wang
It was shown for the first time that cyclohexanone oxime (CHO) can be selectively produced by heterogeneous copper-catalyzed hydrogenative transformation of nitrocyclohexane (NC). The combination of Cu(0) and Cu(+) and their cooperative interaction with weakly acidic SiO2 supports elicited a significantly unique and selective catalysis in the hydrogenation of NC to CHO.
February 21, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28219529/challenges-and-prospects-of-xylitol-production-with-whole-cell-bio-catalysis-a-review
#9
REVIEW
Diptarka Dasgupta, Sheetal Bandhu, Dilip K Adhikari, Debashish Ghosh
Xylitol, as an alternative low calorie sweetener is well accepted in formulations of various confectioneries and healthcare products. Worldwide it is industrially produced by catalytic hydrogenation of pure d-xylose solution under high temperature and pressure. Biotechnological xylitol production is a potentially attractive replacement for chemical process, as it occurs under much milder process conditions and can be based on sugar mixtures derived from low-cost industrial and agri-waste. However, microbial fermentation route of xylitol production is not so far practiced industrially...
April 2017: Microbiological Research
https://www.readbyqxmd.com/read/28219034/preparation-of-core-shell-nanostructure-fe3o4-peg400-so3h-as-heterogeneous-and-magnetically-recyclable-nanocatalyst-for-one-pot-synthesis-of-substituted-pyrroles-by-paal-knorr-reaction-at-room-temperature
#10
Fahimeh Bonyasi, Malak Hekmati, Hojat Veisi
An efficient procedure has been proposed for the loading of sulfonic acid groups on the surface of polyethylene glycol 400 (PEG400)-encapsulated Fe3O4 nanoparticles to synthesize a core-shell Fe3O4@PEG400-SO3H nano catalyst. Surface functionalization of magnetic particles in such a way is a refined method of bridging the gap amongst heterogeneous and homogeneous catalysis. The procured nano catalyst was classified through Fourier transformed infrared spectroscopy (FT-IR), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), wavelength-dispersive X-ray spectroscopy (WDX), thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM), X-ray photoelectron spectroscopy (XPS), BET, and back titration...
February 13, 2017: Journal of Colloid and Interface Science
https://www.readbyqxmd.com/read/28218922/unravelling-surface-and-interfacial-structures-of-a-metal-organic-framework-by-transmission-electron-microscopy
#11
Yihan Zhu, Jim Ciston, Bin Zheng, Xiaohe Miao, Cory Czarnik, Yichang Pan, Rachid Sougrat, Zhiping Lai, Chia-En Hsiung, Kexin Yao, Ingo Pinnau, Ming Pan, Yu Han
Metal-organic frameworks (MOFs) are crystalline porous materials with designable topology, porosity and functionality, having promising applications in gas storage and separation, ion conduction and catalysis. It is challenging to observe MOFs with transmission electron microscopy (TEM) due to the extreme instability of MOFs upon electron beam irradiation. Here, we use a direct-detection electron-counting camera to acquire TEM images of the MOF ZIF-8 with an ultralow dose of 4.1 electrons per square ångström to retain the structural integrity...
February 20, 2017: Nature Materials
https://www.readbyqxmd.com/read/28218831/new-possibilities-for-magnetic-control-of-chemical-and-biochemical-reactions
#12
Anatoly Buchachenko, Ronald G Lawler
Chemistry is controlled by Coulomb energy; magnetic energy is lower by many orders of magnitude and may be confidently ignored in the energy balance of chemical reactions. The situation becomes less clear, however, when reaction rates are considered. In this case, magnetic perturbations of nearly degenerate energy surface crossings may produce observable, and sometimes even dramatic, effects on reactions rates, product yields, and spectroscopic transitions. A case in point that has been studied for nearly five decades is electron spin-selective chemistry via the intermediacy of radical pairs...
February 20, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28218828/a-simple-and-facile-approach-to-create-charge-reversible-pores-via-hydrophobic-anchoring-of-ionic-amphiphiles
#13
Sonu Kizhakeppura, B V V S Pavan Kumar, Subi J George, Muthusamy Eswaramoorthy
Mesoporous silica based charge reversal systems have gained significant attention in the recent years due to a variety of applications such as drug delivery, dye adsorption, catalysis, chromatography etc. Such systems often use covalent strategies to immobilize functional groups on the silica scaffold. However, lack of dynamism, modularity and post-synthetic flexibility associated with covalent routes limit their wider applicability. Alternatively, supramolecular routes are gaining increased attention owing to their ability to overcome these limitations...
February 20, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28218821/co2-catalysis
#14
EDITORIAL
Arjan W Kleij, Michael North, Atsushi Urakawa
Out of thin air: In this Editorial, the Guest Editors introduce a Special Issue on Carbon Dioxide Conversion Catalysis, discuss its importance in modern chemical processes, and highlight a few examples of its use in industry, such as the synthesis of cyclic carbonates and the conversion of CO2 into fuels.
February 20, 2017: ChemSusChem
https://www.readbyqxmd.com/read/28218438/structural-and-biochemical-characterization-of-the-nucleoside-hydrolase-from-c-elegans-reveals-the-role-of-two-active-site-cysteine-residues-in-catalysis
#15
Ranjan Kumar Singh, Jan Steyaert, Wim Versées
Nucleoside hydrolases (NHs) catalyze the hydrolysis of the N-glycoside bond in ribonucleosides and are found in all three domains of life. Although in parasitic protozoa a role in purine salvage has been well established, their precise function in bacteria and higher eukaryotes is still largely unknown. NHs have been classified into three homology groups based on the conservation of active site residues. While many structures are available of representatives of group I and II, structural information for group III NHs is lacking...
February 20, 2017: Protein Science: a Publication of the Protein Society
https://www.readbyqxmd.com/read/28218314/implicating-the-contributions-of-surface-and-bulk-states-on-carrier-trapping-and-photocurrent-performance-of-bivo4-photoanodes
#16
B Pattengale, J Huang
Monoclinic-scheelite BiVO4 has been widely studied as a promising oxygen evolution reaction (OER) catalyst in artificial photosynthesis. Though significant progress to improve or augment its catalysis performance has been made, fundamental understanding of its relatively poor performance as a bare material is lacking. In this paper, we report the correlation of the surface structure and trap states with charge separation efficiency and OER performance of bare BiVO4 photoanodes via varying the sample thickness...
February 20, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28217990/telomerase-activity-detection-with-amplification-free-single-molecule-stochastic-binding-assay
#17
Xin Su, Zehao Li, Xinzhong Yan, Lei Wang, Xu Zhou, Lin Wei, Lehui Xiao, Changyuan Yu
Since the elongation of telomeres is associated with tumorigenesis, it is of great interest to develop rapid and high-confidence telomerase activity detection methods for disease diagnosis. Currently, amplification based strategies have been extensively explored for telomerase detection in vitro and in vivo. However, amplification typically associated with poor reproducibility and high background which hamper their further applications particularly for real sample assay. Here, we demonstrated a new amplification-free single molecule imaging method for telomerase activity detection in vitro based on nucleic acid stochastic binding with total internal reflection fluorescence microscopy (TIRFM)...
February 20, 2017: Analytical Chemistry
https://www.readbyqxmd.com/read/28217896/detection-of-palladium-i-in-aerobic-oxidation-catalysis
#18
Jonathan N Jaworski, Scott D McCann, Ilia A Guzei, Shannon S Stahl
Palladium(II)-catalyzed oxidation reactions exhibit broad utility in organic synthesis; however, they often feature high catalyst loading and low turnover numbers relative to non-oxidative cross-coupling reactions. Insights into the fate of the Pd catalyst during turnover could help to address this limitation. Herein, we report the identification and characterization of a dimeric Pd(I) species in two prototypical Pd-catalyzed aerobic oxidation reactions: allylic C-H acetoxylation of terminal alkenes and intramolecular aza-Wacker cyclization...
February 20, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28217844/chiral-assembly-of-aie-active-achiral-molecules-an-odd-effect-in-self-assembly
#19
Anuradha, Duong Duc La, Mohammad Al Kobaisi, Akhil Gupta, Sheshanath V Bhosale
The induction of chirality in supramolecular structures through hierarchical self-assembly of achiral compounds and the control of their handedness are closely related to the evolution of life and the chiral amplification found in nature. Herein, it is shown that the combination of achiral tetraphenylethylene, an aggregation-induced emission (AIE)-active luminophore bearing four alkyl chains with an odd or even number of carbon atoms via an amide linkage in the molecular structure allows the induction and control of supramolecular chirality in well-defined helical superstructures by controlling the solvent composition and polarity...
January 16, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28217784/br%C3%A3-nsted-acid-catalyzed-stereoselective-4-3-cycloadditions-of-ortho-hydroxybenzyl-alcohols-with-n-n-cyclic-azomethine-imines
#20
Guang-Jian Mei, Zi-Qi Zhu, Jia-Jia Zhao, Chen-Yu Bian, Jie Chen, Ruo-Wei Chen, Feng Shi
The first [4+3] cycloaddition of ortho-hydroxybenzyl alcohols has been established by making use of N,N'-cyclic azomethine imines as suitable 1,3-dipoles under Brønsted acid catalysis. By using this strategy, biologically important seven-membered heterocyclic scaffolds have been constructed in good yields and excellent diastereoselectivities (up to 92% yield, most >95 : 5 dr).
February 20, 2017: Chemical Communications: Chem Comm
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