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https://www.readbyqxmd.com/read/28621913/visible-light-promoted-generation-of-alpha-ketoradicals-from-vinyl-bromides-and-molecular-oxygen-synthesis-of-indenones-and-dihydroindeno-1-2-c-chromenes
#1
Santosh K Pagire, Peter Kreitmeuer, Oliver Reiser
Ortho-alkynylated α-bromocinnamates can be converted by a visible light mediated photocascade reaction with molecular oxygen either to indenones or to dihydroindeno[1,2-c]chromenes. The one-step process features two photochemical key steps, i.e. the activation of vinyl bromides by energy transfer giving rise to α-ketoradicals in the reaction with molecular oxygen and the α-hydroxylation of an arene moiety.
June 16, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28571386/glassy-dynamics-of-polymethylphenylsiloxane-in-one-and-two-dimensional-nanometric-confinement-a-comparison
#2
Wycliffe K Kipnusu, Mohamed Elsayed, Reinhard Krause-Rehberg, Friedrich Kremer
Glassy dynamics of polymethylphenylsiloxane (PMPS) is studied by broadband dielectric spectroscopy in one-dimensional (1D) and two-dimensional (2D) nanometric confinement; the former is realized in thin polymer layers having thicknesses down to 5 nm, and the latter in unidirectional (thickness 50 μm) nanopores with diameters varying between 4 and 8 nm. Based on the dielectric measurements carried out in a broad spectral range at widely varying temperatures, glassy dynamics is analyzed in detail in 1D and in 2D confinements with the following results: (i) the segmental dynamics (dynamic glass transition) of PMPS in 1D confinement down to thicknesses of 5 nm is identical to the bulk in the mean relaxation rate and the width of the relaxation time distribution function; (ii) additionally a well separated surface induced relaxation is observed, being assigned to adsorption and desorption processes of polymer segments with the solid interface; (iii) in 2D confinement with native inner pore walls, the segmental dynamics shows a confinement effect, i...
May 28, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28567460/ni-and-cu-catalyzed-one-pot-synthesis-of-unsymmetrical-1-3-di-hetero-aryl-1h-indazoles-from-hydrazine-o-chloro-hetero-benzophenones-and-hetero-aryl-bromides
#3
Carson Wiethan, Christopher M Lavoie, Andrey Borzenko, Jillian S K Clark, Helio G Bonacorso, Mark Stradiotto
The nickel-catalyzed cyclization of in situ generated ortho-chlorobenzophenone hydrazone derivatives, to afford 3-(hetero)aryl-1H-indazoles, is documented for the first time. The product 1H-indazoles can be transformed subsequently in a one-pot procedure into 1,3-di(hetero)aryl-1H-indazoles via copper-catalyzed N-arylation with (hetero)aryl bromides.
June 14, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28561101/on-the-outside-looking-in-rethinking-the-molecular-mechanism-of-1-3-dipolar-cycloadditions-from-the-perspective-of-bonding-evolution-theory-the-reaction-between-cyclic-nitrones-and-ethyl-acrylate
#4
A I Adjieufack, I M Ndassa, I Patouossa, J K Mbadcam, V S Safont, M Oliva, J Andrés
In this work we report on the progress that has been made towards gaining an understanding of the molecular mechanism of 1,3-dipolar cycloadditions using the bonding evolution theory (BET). A detailed analysis of the flow of electron density along the reaction pathway of the formal 1,3-dipolar cycloaddition reaction between cyclic nitrones (pyrroline-1-oxide and 2,3,4,5-tetrahydropyridine-1-oxide) and ethyl acrylate, as a case study, allowed the nature of the molecular mechanisms to be characterized. The present study provides a deep insight into the reaction mechanism, based on the electron density rearrangements given by the structural stability domains, and their connection with the bond breaking/forming processes along the reaction pathway...
May 31, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28511010/%C3%AF-extended-and-curved-antiaromatic-polycyclic-hydrocarbons
#5
Junzhi Liu, Ji Ma, Ke Zhang, Prince Ravat, Peter Machata, Stanislav Avdoshenko, Felix Hennersdorf, Hartmut Komber, Wojciech Pisula, Jan J Weigand, Alexey A Popov, Reinhard Berger, Klaus Müllen, Xinliang Feng
Synthesis of antiaromatic polycyclic hydrocarbons (PHs) is challenging because the high energy of their highest occupied molecular orbital and low energy of their lowest unoccupied molecular orbital cause them to be reactive and unstable. In this work, two large antiaromatic acene analogues, namely, cyclopenta[pqr]indeno[2,1,7-ijk]tetraphene (CIT, 1a) and cyclopenta[pqr]indeno[7,1,2-cde]picene (CIP, 1b), as well as a curved antiaromatic molecule with 48 π-electrons, dibenzo[a,c]diindeno[7,1,2-fgh:7',1',2'-mno]phenanthro[9,10-k]tetraphene (DPT, 1c), are synthesized on the basis of the corona of indeno[1,2-b]fluorene...
June 7, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28503205/substitution-of-fluorine-in-m-c6f5bf3-with-organolithium-compounds-distinctions-between-o-and-n-nucleophiles
#6
Anton Yu Shabalin, Nicolay Yu Adonin, Vadim V Bardin
Borates M[C6F5BF3] (M = K, Li, Bu4N) react with organolithium compounds, RLi (R = Me, Bu, Ph), in 1,2-dimethoxyethane or diglyme to give M[4-RC6F4BF3] and M[2-RC6F4BF3]. When R is Me or Bu, the nucleophilic substitution of the fluorine atom at the para position to boron is the predominant route. When R = Ph, the ratio M[4-RC6F4BF3]/M[2-RC6F4BF3] is ca. 1:1. Substitution of the fluorine atom at the ortho position to boron is solely caused by the coordination of RLi via the lithium atom with the fluorine atoms of the BF3 group...
2017: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28485602/metal-free-sequential-c-sp-2-h-oh-and-c-sp-3-h-aminations-of-nitrosoarenes-and-n-heterocycles-to-ring-fused-imidazoles
#7
Anisha Purkait, Subhra Kanti Roy, Hemant Kumar Srivastava, Chandan K Jana
Hydrogen bond assisted ortho-selective C(sp(2))-H amination of nitrosoarenes and subsequent α-C(sp(3))-H functionalization of aliphatic amines is achieved under metal-free conditions. The annulation of nitrosoarenes and 2-hydroxy-C-nitroso compounds with N-heterocycles provides a facile excess to a wide range of biologically relevant ring-fused benzimidazoles and structurally novel polycyclic imidazoles, respectively. Nucleophilic aromatic hydrogen substitution (SNArH) was found to be preferred over classical SNAr reaction during the C(sp(2))-H amination of halogenated nitrosoarenes...
May 9, 2017: Organic Letters
https://www.readbyqxmd.com/read/28443910/spin-state-variability-in-fe-2-complexes-of-substituted-2-pyridin-2-yl-1-10-phenanthroline-ligands-as-versatile-terpyridine-analogues
#8
Holm Petzold, Paul Djomgoue, Gerald Hörner, Silvio Heider, Charles Lochenie, Birgit Weber, Tobias Rüffer, Dieter Schaarschmidt
Fe(2+) spin crossover complexes [Fe(L)2](2+) (L = 2-(6-R(1)-pyridin-2-yl)-1,10-phenanthroline with R(1) = H, methoxy, bromo, -(1H-pyrazol-1-yl) or L = 2-(3-methoxy-pyridin-2-yl)-1,10-phenanthroline) were prepared. These air stable and durable complexes show SCO behaviour with very different transition temperatures T1/2 ranging from 130 K to 600 K depending on the substitution pattern. The use of (1)H NMR spectroscopy to elucidate the thermodynamics and kinetics of SCO in a solution of this series is described in detail...
May 16, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28441011/synthesis-characterization-and-dft-analysis-of-bis-terpyridyl-based-molecular-cobalt-complexes
#9
Safwan Aroua, Tanya K Todorova, Paul Hommes, Lise-Marie Chamoreau, Hans-Ulrich Reissig, Victor Mougel, Marc Fontecave
Terpyridine ligands are widely used in chemistry and material sciences owing to their ability to form stable molecular complexes with a large variety of metal ions. In that context, variations of the substituents on the terpyridine ligand allow modulation of the material properties. Applying the Stille cross-coupling reaction, we prepared with good yields a new series of terpyridine ligands possessing quinoline-type moieties in ortho, meta, and para positions and dimethylamino substituents at central or distal positions...
April 25, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28435723/formamidinium-iodide-crystal-structure-and-phase-transitions
#10
Andrey A Petrov, Eugene A Goodilin, Alexey B Tarasov, Vladimir A Lazarenko, Pavel V Dorovatovskii, Victor N Khrustalev
At a temperature of 100 K, CH5N2(+)·I(-) (I), crystallizes in the monoclinic space group P21/c. The formamidinium cation adopts a planar symmetrical structure [the r.m.s. deviation is 0.002 Å, and the C-N bond lengths are 1.301 (7) and 1.309 (8) Å]. The iodide anion does not lie within the cation plane, but deviates from it by 0.643 (10) Å. The cation and anion of I form a tight ionic pair by a strong N-H⋯I hydrogen bond. In the crystal of I, the tight ionic pairs form hydrogen-bonded zigzag-like chains propagating toward [20-1] via strong N-H⋯I hydrogen bonds...
April 1, 2017: Acta Crystallographica. Section E, Crystallographic Communications
https://www.readbyqxmd.com/read/28426213/role-of-mediator-and-effects-of-temperature-on-ortho-c-n-bond-fusion-reactions-of-aniline-using-ruthenium-templates-isolation-and-characterization-of-new-ruthenium-complexes-of-the-in-situ-generated-ligands
#11
Suman K Roy, Debabrata Sengupta, Santi Prasad Rath, Tanushri Saha, Subhas Samanta, Sreebrata Goswami
In this work, ortho-C-N bond fusion reactions of aniline are followed by the use of two different ruthenium mediators. Reaction of aniline with [Ru(III)(terpy)Cl3] (terpy = 2,2':6',2″-terpyridine) resulted in a trans bis-aniline ruthenium(II) complex [1](+) which upon oxidation with H2O2 produced compound [2](+) of a bidentate ligand, N-phenyl-1,2-benzoquinonediimine, due to an oxidative ortho-C-N bond fusion reaction. Complex [1](+) and aniline (neat) at 185 °C produced a bis-chelated ruthenium complex (3)...
April 20, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28406298/reaction-of-aniline-with-singlet-oxygen-o2-1-%C3%AE-g
#12
Jomana Al-Nu'airat, Mohammednoor Altarawneh, Xiangpeng Gao, Phillip R Westmoreland, Bogdan Z Dlugogorski
Dissolved organic matter (DOM) acts as an effective photochemical sensitizer that produces the singlet delta state of molecular oxygen (O2(1)Δg), a powerful oxidizer that removes aniline from aqueous solutions. However, the exact mode of this reaction, the p- to o-iminobenzoquinone ratio, and the selectivity of one over the other remain largely speculative. This contribution resolves these uncertainties. We report, for the first time, a comprehensive mechanistic and kinetic account of the oxidation of aniline with the singlet delta oxygen using B3LYP and M06 functionals in both gas and aqueous phases...
May 4, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28358500/molecular-mechanism-of-dioxin-formation-from-chlorophenol-based-on-electron-paramagnetic-resonance-spectroscopy
#13
Lili Yang, Guorui Liu, Minghui Zheng, Yuyang Zhao, Rong Jin, Xiaolin Wu, Yang Xu
Few studies have investigated the free radical intermediates involved in the formation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) from chlorophenol. This study clarified the reaction pathways during thermochemical formation of PCDDs from 2,3,6-trichlorophenol (TCP) over a Cu(II)O/silica matrix, which was used to simulate fly ash, at 298-523 K. The reaction was studied using electron paramagnetic resonance (EPR) spectroscopy and theoretical calculations. In situ EPR indicated the TCP radical (TCPR) formed by hydrogen abstraction of TCP...
May 2, 2017: Environmental Science & Technology
https://www.readbyqxmd.com/read/28346278/effects-of-myopic-orthokeratology-on-visual-performance-and-optical-quality
#14
Guihua Liu, Zhi Chen, Feng Xue, Jing Li, Mi Tian, Xingtao Zhou, Ruihua Wei
OBJECTIVES: To analyze the changes in visual performance and optical quality after orthokeratology (ortho-k) treatment and its correlation with the magnitude of lens decentration and the diameter of treatment zone (TxZ). METHODS: A prospective study was conducted in 27 eyes of 27 patients wearing ortho-k contact lens. Area under log contrast sensitivity function (AULCSF), modulation transfer function cutoff values (MTFcutoff), Strehl ratio (SR), and objective scattering index (OSI) were measured and compared before and 1 month after ortho-k lens treatment...
March 24, 2017: Eye & Contact Lens
https://www.readbyqxmd.com/read/28337465/inflammatory-response-and-barrier-dysfunction-by-different-e-cigarette-flavoring-chemicals-identified-by-gas-chromatography-mass-spectrometry-in-e-liquids-and-e-vapors-on-human-lung-epithelial-cells-and-fibroblasts
#15
Janice Gerloff, Isaac K Sundar, Robert Freter, Emily R Sekera, Alan E Friedman, Risa Robinson, Todd Pagano, Irfan Rahman
Recent studies suggest that electronic cigarette (e-cig) flavors can be harmful to lung tissue by imposing oxidative stress and inflammatory responses. The potential inflammatory response by lung epithelial cells and fibroblasts exposed to e-cig flavoring chemicals in addition to other risk-anticipated flavor enhancers inhaled by e-cig users is not known. The goal of this study was to evaluate the release of the proinflammatory cytokine (interleukin-8 [IL-8]) and epithelial barrier function in response to different e-cig flavoring chemicals identified in various e-cig e-liquid flavorings and vapors by chemical characterization using gas chromatography-mass spectrometry analysis...
March 1, 2017: Applied in Vitro Toxicology
https://www.readbyqxmd.com/read/28330347/the-interaction-of-no-x-2-%C3%AE-with-h2-ab-initio-potential-energy-surfaces-and-bound-states
#16
Jacek Kłos, Qianli Ma, Millard H Alexander, Paul J Dagdigian
We determine from first principles two sets of four-dimensional diabatic potential energy surfaces (PES's) for the interaction of NO(X(2)Π) with H2, under the assumption of fixed NO and H2 bond distances. The first set of PES's was computed with the explicitly correlated multi-reference configuration interaction method [MRCISD-F12 + Q(Davidson)], and the second set with an explicitly correlated, coupled-cluster method [RCCSD(T)-F12a] with the geometry scan limited to geometries possessing a plane of symmetry...
March 21, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28316808/crystal-structure-of-the-monoclinic-phase-phase-iv-of-bis-tetra-methyl-ammonium-tetra-chlorido-cuprate-ii
#17
Gorgui Awa Seck, Libasse Diop, Allen G Oliver
The crystal structure of the low-temperature monoclinic phase of the title compound, [(CH3)4N]2[CuCl4], was determined at 120 K. The structure of the room-temperature phase has been determined in the ortho-rhom-bic space group Pmcm [Morosin & Lingafelter (1961 ▸). J. Phys. Chem. 50-51; Clay et al. (1975 ▸). Acta Cryst. B31 289-290]. The asymmetric unit consists of one discrete tetra-chlorido-cuprate anion with a distorted tetra-hedral geometry and two tetra-methyl-ammonium cations. In the crystal, the cations and the anions are linked via weak C-H⋯Cl hydrogen bonds...
March 1, 2017: Acta Crystallographica. Section E, Crystallographic Communications
https://www.readbyqxmd.com/read/28316195/-analysis-of-corneal-complications-in-children-wearing-orthokeratology-lenses-at-night
#18
C X Miao, X Y Xu, H Zhang
Objective: To explore the characteristics, prognoses and corneal complications of children wearing orthokeratology lenses (Ortho-K) at night. Methods: Retrospective case analysis. A total of 113 cases (219 eyes) wore Ortho-K for myopia at night, including 7 cases with unilateral glass wear. The average age was (11.5±2.0) years old. The myopia ranged from -1.00 D to -9.00 D in all eyes and from -2.00 D to -4.00 D in 157 of them. Examinations were performed before lens wearing, at 1 hour, the next morning, 2 days, 3 days, 1 week and 2 weeks after lens wearing, and thereafter once a month...
March 11, 2017: [Zhonghua Yan Ke za Zhi] Chinese Journal of Ophthalmology
https://www.readbyqxmd.com/read/28299841/fluorinated-unsymmetrical-n-n-diaryl-imidazolium-salts-new-functionalized-nhc-ligand-precursors
#19
Maxim A Topchiy, Maria A Zotova, Salekh M Masoud, Artur K Mailyan, Ivan V Ananyev, Sergey E Nefedov, Andrey F Asachenko, Sergey N Osipov
An efficient and scaled-up synthesis of the imidazol-2-ylidene-based unsymmetrical NHC precursors bearing the sterically demanding hexafluoroisopropylalkoxy group [(CF3 )2 (OR)C-] at the ortho position of the N-aryl substituent was developed. The key step of the method involved the transformation of a Mes-substituted oxazolinium tetrafluoroborate salt through the reaction with the corresponding binucleophilic fluoroalkyl-substituted aniline. The subsequent post-modification of the resulting hydroxyl-containing salt through a simple one-step O-alkylation protocol provided access to a new family of unsymmetrical fluorinated NHC precursors...
May 11, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28298110/near-infrared-overtone-voh-2-%C3%A2-0-spectroscopy-of-ne-h2o-clusters
#20
Michael P Ziemkiewicz, Christian Pluetzer, Michael Wojcik, Jérôme Loreau, Ad van der Avoird, David J Nesbitt
Vibrationally state selective overtone spectroscopy and dynamics of weakly bound Ne-H2O complexes (D0((para)) = 31.67 cm(-1), D0((ortho)) = 34.66 cm(-1)) are reported for the first time, based on near infrared excitation of van der Waals cluster bands correlating with vOH = 2 ← 0 overtone transitions (|02(-)⟩←|00(+)⟩ and |02(+)⟩←|00(+)⟩) out of the ortho (101) and para (000) internal rotor states of the H2O moiety. Quantum theoretical calculations for nuclear motion on a high level ab initio potential energy surface (CCSD(T)/VnZ-f12 (n = 3,4), corrected for basis set superposition error and extrapolated to the complete basis set limit) are employed for assignment of Σ←Σ,Π←Σ, and Σ←Π infrared bands in the overtone spectra, where Σ(K = 0) and Π (K = 1) represent approximate projections (K) of the body angular momentum along the Ne-H2O internuclear axis...
March 14, 2017: Journal of Chemical Physics
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