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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
Borja Cendón, Noelia Casanova, Cezar Comanescu, Rebeca García-Fandiño, Andrés Seoane, Moisés Gulías, José L Mascareñas
2-Alkenyltriflylanilides react with allenes upon treatment with catalytic amounts of Pd(OAc)2 and Cu(II) to give highly valuable 2,3-dihydro-1H-benzo[b]azepines, in good yields, and with very high regio- and diastereoselectivities. Density functional theory (DFT) calculations suggest that the C-H activation of the alkenylanilide involves a classical concerted metalation-deprotonation (CMD) mechanism.
March 27, 2017: Organic Letters
Sebastian Bruckner, Robert G Haase, Rainer Schobert
3-Acyltetramic acids derived from β-hydroxytyrosine are synthetically challenging. We present the first route to this structural motif, based upon a condensation between a Meldrum's acid conjugate bearing the acyl side chain, and a β-hydroxytyrosinate, N-protected by an ortho-nitrobenzyl group. This group enables the Dieckmann cyclization of the resulting N-(β-ketoacyl)amino ester, after which it can be removed photolytically without com¬promising the delicate 3'-hydroxy group. This strategy was applied to the first total synthesis of the fungal metabolite F-14329 (1)...
March 27, 2017: Chemistry: a European Journal
Ali Othman, Daniel Andreescu, Dinusha P Karunaratne, Suryadevara V Babu, Silvana Andreescu
Development of systems for capture, sequestration and tracking of nanoparticles (NPs) is becoming a significant focus in many aspects of nanotechnology and environmental research. These systems enable a broad range of applications for evaluating concentration, distribution and effects of NPs for environmental, clinical, epidemiological and occupational exposure studies. Herein, we describe the first example of a ligand-graft multifunctional platform for capture and detection of cerium oxide (CeO2 or ceria) NPs...
March 24, 2017: ACS Applied Materials & Interfaces
Ahmad Alobeid, Tarek El-Bialy, Said Khawatmi, Cornelius Dirk, Andreas Jäger, Christoph Bourauel
Background/objective: The aim of this study was to evaluate force levels exerted by levelling arch wires with labial and lingual conventional and self-ligating brackets. Materials/methods: The tested orthodontic brackets were of the 0.022-in slot size for labial and 0.018-in for lingual brackets and were as follows: 1. Labial brackets: (i) conventional bracket (GAC-Twin, Dentsply), (ii) passive self-ligating (SL) brackets (Damon-Q®, ORMCO; Ortho classic H4™, Orthoclassic; FLI®SL, Rocky Mountain Orthodontics) and (iii) active SL brackets (GAC In-Ovation®C, DENTSPLY and SPEED™, Strite)...
January 25, 2017: European Journal of Orthodontics
Donald C McAteer, Erman Javed, Lily Huo, Shouquan Huo
A unique, platinum-catalyzed, direct C-H acylation of 2-(aryloxy)pyridines with acyl chlorides is discovered. The reaction requires neither an oxidant nor other additives. When both ortho positions of the aryl group are accessible, the double acylation occurs readily to produce the diacylated products. Aliphatic, aromatic, and α,β-unsaturated acyl groups can all be introduced. The acylation reaction may proceed through an analogous aromatic electrophilic substitution triggered by the nucleophilic attack of the platinum at the acyl chloride...
March 24, 2017: Organic Letters
Jiancong Xu, Yang Liu, Ying Wang, Yajuan Li, Xiaohua Xu, Zhong Jin
The Pd-catalyzed direct C(sp(2))-H arylation of aromatic ketones using a transient directing group is described. The ketimine/carboxylate bidentate directing group in situ generated from aromatic ketone and glycine enabled a palladium-catalyzed ortho-C-H arylation, which shows extensive substrate compatibility.
March 24, 2017: Organic Letters
Chongqing Pan, Zixi Zhu, Mingkai Zhang, Zhenhua Gu
The palladium-catalyzed asymmetric synthesis of enone-based atropisomers from 2-iodo-3-methylcyclohex-2-enones and aryl boronic acid is reported. BoPhoz-type phosphine-aminophosphine ligands showed superior enantioselectivity over other ligands. These cyclohexenone-based atropisomers are useful compounds for further elaboration. The divergent synthesis of biaryl atropisomers with different ortho substituents was demonstrated.
March 24, 2017: Angewandte Chemie
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: Appl In Vitro Toxicol
Fei Jin, Shangfeng Yang, Erhard Kemnitz, Sergey I Troyanov
A classical fullerene is composed of hexagons and pentagons only, and its stability is generally determined by the Isolated-Pentagon-Rule (IPR). Herein, high-temperature chlorination of a mixture containing a classical IPR-obeying fullerene C88 resulted in isolation and X-ray crystallographic characterization of non-IPR, nonclassical (NC) fullerene chloride C84(NC2)Cl30 (1) containing two heptagons. The carbon cage in C84(NC2)Cl30 contains 14 pentagons, 12 of which form two pairs of fused pentagons and two groups of quaternary sequentially fused pentagons, which have never been observed in reported carbon cages...
March 27, 2017: Journal of the American Chemical Society
Danuta Rusinska-Roszak
Intramolecular hydrogen bonding (HB) is one of the most studied noncovalent interactions of molecules. Many physical, spectral, and topological properties of compounds are under the influence of HB, and there are many parameters used to notice and to describe these changes. Hitherto, no general method of measurement of the energy of intramolecular hydrogen bond (EHB) has been put into effect. We propose the molecular tailoring approach (MTA) for EHB calculation, modified to apply it to Ar-O-H∙∙∙O=C systems...
March 18, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Gavin R Kiel, Micah S Ziegler, T Don Tilley
Syntheses of large polycyclic aromatic hydrocarbons (PAHs) and graphene nanostructures demand methods that are capable of selectively and efficiently fusing large numbers of aromatic rings, yet such methods remain scarce. Herein, we report a new approach that is based on the quantitative intramolecular reductive cyclization of an oligo(diyne) with a low-valent zirconocene reagent, which gives a PAH with one or more annulated zirconacyclopentadienes (ZrPAHs). The efficiency of this process is demonstrated by a high-yielding fivefold intramolecular coupling to form a helical ZrPAH with 16 fused rings (from a precursor with no fused rings)...
March 23, 2017: Angewandte Chemie
Lisha Wu, Yinfeng Meng, Jamie Ferguson, Lijie Wang, Fanlong Zeng
Palladium-catalyzed oxidative annulation of ortho-alkenyllanilines and allenes to constitute valuable but synthetically challenging benzo[b]azepines has been developed. The procedure, involving of the cleavage of the terminal C(sp2)-H bond of the vinyl moiety and the participation of allenes as two-carbon cycloaddition partner, is attractive in terms of assembly efficiency and environmentally friendliness. The transformation features mild reaction conditions and good functional group tolerance, resulting in a variety of benzo[b]azepines in good to excellent yields...
March 23, 2017: Journal of Organic Chemistry
Jean-Philip George Lumb, Kenneth Virgel N Esguerra
Azophenols are important chromophores and reagents in organic synthesis, with applications as pigments and molecular switches. Herein, we describe a catalytic aerobic process that couples phenols and hydrazines or hydrazides for their synthesis. The key aromatic C-N bond is formed via condensation between the hydrazine or hydrazide and an ortho-quinone, which triggers a redox-isomerization to install the azo functionality. Notable features include rapid access to highly functionalized azophenols with a range of electronic configurations, including "push-pull" systems, under conditions that employ simple, un-activated substrates, occur at room temperature using an earth-abundant and commercially available copper-catalyst, and produce water as the only stoichiometric byproduct...
March 22, 2017: Chemistry: a European Journal
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
Yuki Miyamoto, Asao Mizoguchi, Hideto Kanamori
The bleaching process in the C-F stretching mode (ν3 band) of CH3F-(ortho-H2)n [n = 0 and 1] clusters in solid para-H2 was monitored using pump and probe laser spectroscopy on the C-H stretching mode (ν1 and 2ν5 bands). From an analysis of the depleted spectral profiles, the transition frequency and linewidth of each cluster were directly determined. The results agree with the values previously derived from a deconvolution analysis of the broadened ν1/2ν5 spectrum observed by FTIR spectroscopy. The complementary increase and decrease between the n = 0 and 1 components were also verified through monitoring the ν1 and 2ν5 bands, which suggests a closed system among the CH3F-(ortho-H2)n clusters...
March 21, 2017: Journal of Chemical Physics
Tao Yang, Ralf I Kaiser, Tyler P Troy, Bo Xu, Oleg Kostko, Musahid Ahmed, Alexander M Mebel, Marsel V Zagidullin, Valeriy N Azyazov
The hydrogen-abstraction/acetylene-addition (HACA) mechanism has been central for the last decades in attempting to rationalize the formation of polycyclic aromatic hydrocarbons (PAHs) as detected in carbonaceous meteorites such as in Murchison. Nevertheless, the basic reaction mechanisms leading to the formation of even the simplest tricyclic PAHs like anthracene and phenanthrene are still elusive. Here, by exploring the previously unknown chemistry of the ortho-biphenylyl radical with acetylene, we deliver compelling evidence on the efficient synthesis of phenanthrene in carbon-rich circumstellar environments...
March 22, 2017: Angewandte Chemie
Tomohiro Morita, Tetsuya Satoh, Masahiro Miura
The rhodium(III)-catalyzed ortho-alkenylation of N-Boc-anilines with alkenes such as acrylate ester and styrene proceeds smoothly through C-H bond cleavage. Obtained o-alkenylanilines can be readily transformed to nitrogen-containing fused heteroaromatic compounds including indoles and quinolines.
March 21, 2017: Organic Letters
Qunfeng Zhang, Meiya Liu, Jianyun Ruan
BACKGROUND: As the predominant secondary metabolic pathway in tea plants, flavonoid biosynthesis increases with increasing temperature and illumination. However, the concentration of most flavonoids decreases greatly in light-sensitive tea leaves when they are exposed to light, which further improves tea quality. To reveal the metabolism and potential functions of flavonoids in tea leaves, a natural light-sensitive tea mutant (Huangjinya) cultivated under different light conditions was subjected to metabolomics analysis...
March 20, 2017: BMC Plant Biology
Yuan-Jun Gao, Xue-Ping Chang, Xiang-Yang Liu, Quan-Song Li, Ganglong Cui, Walter Thiel
The photophysical properties of tetraphenylethene (TPE) compounds may differ widely depending on the substitution pattern, for example with regard to the fluorescence quantum yield phi_f and the propensity to exhibit aggregation-induced emission (AIE). We report combined electronic structure calculations and nonadiabatic dynamics simulations to study the excited-state decay mechanisms of two TPE derivatives with four methyl substituents, either in meta-position (TPE-4mM, phi_f = 0.1%) or in ortho-position (TPE-4oM, phi_f = 64...
March 20, 2017: Journal of Physical Chemistry. A
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