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https://www.readbyqxmd.com/read/28453268/ir-catalyzed-ortho-borylation-of-phenols-directed-by-substrate-ligand-electrostatic-interactions-a-combined-experimental-in-silico-strategy-for-optimizing-weak-interactions
#1
Buddhadeb Chattopadhyay, Jonathan E Dannatt, Ivonne L Andújar-de Sanctis, Kristin A Gore, Robert E Maleczka, Daniel A Singleton, Milton R Smith
A strategy for affecting ortho versus meta/para selectivity in Ir-catalyzed C-H borylations (CHBs) of phenols is described. From selectivity observations with ArylOBpin (pin = pinacolate), it is hypothesized that an electrostatic interaction between the partial negatively charged OBpin group and the partial positively charged bipyridine ligand of the catalyst favors ortho selectivity. Experimental and computational studies designed to test this hypothesis support it. From further computational work a second generation, in silico-designed catalyst emerged, where replacing Bpin with Beg (eg = ethylene glycolate) was predicted to significantly improve ortho selectivity...
April 28, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28449253/amide-directed-c-h-sodiation-by-a-sodium-hydride-iodide-composite
#2
Yinhua Huang, Guo Hao Chan, Shunsuke Chiba
A new protocol for amide-directed ortho and lateral C-H sodiation is enabled by sodium hydride (NaH) in the presence of either sodium iodide (NaI) or lithium iodide (LiI). The transient organosodium intermediates could be transformed into functionalized aromatic compounds.
April 27, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28448911/adsorption-of-polar-organic-molecules-on-sediments-case-study-on-callovian-oxfordian-claystone
#3
S Rasamimanana, G Lefèvre, R V H Dagnelie
The release and transport of anthropogenic organic matter through the geosphere is often an environmental criterion of safety. Sedimentary rocks are widely studied in this context as geological barriers for waste management. It is the case of Callovian-Oxfordian claystone (COx), for which several studies report adsorption of anthropogenic organic molecules. In this study, we evaluated and reviewed adsorption data of polar organic molecules on COx claystone. Experiments were performed on raw claystone, decarbonated and clay fractions...
April 21, 2017: Chemosphere
https://www.readbyqxmd.com/read/28445070/enantioselective-4-2-cycloaddition-of-o-quinone-methides-and-vinyl-sulfides-indirect-access-to-generally-substituted-chiral-chromanes
#4
Zhaobin Wang, Jianwei Sun
A catalytic asymmetric [4 + 2] cycloaddition of ortho-quinone methides (o-QMs) is described. With the readily available vinyl sulfides as the key 2π partner and a properly chosen chiral phosphoric acid catalyst, the reaction proceeded under mild conditions to form the corresponding adduct with high enantio- and diastereoselectivity. Owning to the easy removal and conversion of the sulfenyl group in the product, the present process provides indirect access to generally substituted chromanes previously lacking easy access...
April 26, 2017: Organic Letters
https://www.readbyqxmd.com/read/28444012/are-there-differences-between-comparison-methods-used-to-evaluate-the-accuracy-and-reliability-of-digital-models
#5
Leonardo Tavares Camardella, Hero Breuning, Oswaldo de Vasconcellos Vilella
OBJECTIVES: The accuracy and reliability of plaster models and digital models acquired with two different surface laser scanners were tested by means of three methods: measurement with calipers, digital measurement with proper software and superimposition of the digital models. METHODS: Thirty plaster models with permanent dentition that met the inclusion criteria were selected and scanned with two laser scanners (R700 and Xcad). Three examiners measured distances on plaster models with a digital caliper and on digital models using Ortho Analyzer software...
February 2017: Dental Press Journal of Orthodontics
https://www.readbyqxmd.com/read/28443934/hg-ii-and-pd-ii-complexes-with-a-new-selenoether-bridged-biscarbene-ligand-efficient-mono-and-bis-arylation-of-methyl-acrylate-with-a-pincer-biscarbene-pd-ii-precatalyst
#6
Rishu, Billa Prashanth, Deependra Bawari, Ushnish Mandal, Aditya Verma, Angshuman Roy Choudhury, Sanjay Singh
Two equivalents of 1-benzyl-3-bromoethylbenzimidazolium bromide couple with Na2Se to produce the first selenoether bridged bis-benzimidazolium salt (LH2)Br2. The nitrate (LH2)(NO3)2 and tetrafluoroborate (LH2)(BF4)2 salts were also synthesized from (LH2)Br2. The reaction of Hg(OAc)2 with (LH2)Br2 gave the first pseudo pincer carbene mercury complex, [Hg(L-κ(2)C)][HgBr4] (C1). Different complexes of Pd(ii) with selenoether bridged carbene were obtained using (LH2)Br2 and (LH2)(NO3)2. Syntheses of these complexes were dependent on the counter anion and the temperature...
April 26, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
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
#7
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...
April 26, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28443864/planar-chiral-ferrocenylphosphine-borane-complexes-featuring-agostic-type-b-he-e-hg-sn-interactions
#8
Alain C Tagne Kuate, Roger A Lalancette, F Jäkle
The synthesis of ferrocenylphosphine-borane adducts 1,2-fc(E)(PPh2·BH3) (E = SnR2R', HgX; 1,2-fc = 1,2-ferrocenediyl) that are substituted with organotin or organomercury Lewis acid moieties in ortho-position is presented. Several compounds that feature two ferrocenylphosphine-borane moieties bridged by Sn or Hg are also introduced. The products are fully characterized by multinuclear NMR spectroscopy, high-resolution MALDI-TOF mass spectrometry and elemental analysis. The attachment of the Lewis acid substituent to the same Cp ring of the ferrocene results in planar-chirality and the close proximity between the boron hydride group and the Lewis acid is expected to allow for agostic-type B-HE (E = Sn, Hg) interactions...
April 26, 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/28440829/ruthenium-ii-catalyzed-ortho-c-h-arylation-of-diverse-n-heterocycles-with-aryl-silanes-by-exploiting-solvent-controlled-n-coordination
#10
Pradeep Nareddy, Frank Jordan, Michal Szostak
We report the first method for the direct, regioselective Ru(ii)-catalyzed oxidative arylation of C-H bonds in diverse N-heterocycles with aryl silanes by exploiting solvent-controlled N-coordination. The reaction takes advantage of the attractive features of organosilanes as coupling partners, providing proof of concept for N-directed Ru(ii)-catalyzed C-H arylation. This novel, operationally-simple and versatile protocol utilizes the Ru(ii)/CuF2 reagent system in which CuF2 serves as a dual activator/oxidant in non-coordinating solvents to accommodate for ligand N-coordination...
April 25, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28440592/sequential-reactions-of-alkynes-on-an-ir-iii-single-site
#11
Miguel A Sierra, Mar Gómez-Gallego, Luis Casarrubios, Carmen Ramírez de Arellano, Elena A Giner, Alba D Merinero
Sequential insertion of terminal alkynes on Ir(III) cyclometallated complexes allow the formation of novel metallapolycycles in controlled and efficient manner. ortho-Methylarylethynyl derivatives led to an unprecedented cascade combination of three fundamental processes (C-C bond formation, Csp3-H activation and reductive elimination) on a single Ir(III) center, in a process compatible with functionalized biomolecules and photoactive substrates. The reaction with tert-butylacetylene led to a [6,5,4]-polycycle that incorporates an iridacyclobutenylidene in its structure...
April 25, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28439220/pediatric-reference-intervals-for-transferrin-saturation-in-the-caliper-cohort-of-healthy-children-and-adolescents
#12
Victoria Higgins, Man Khun Chan, Khosrow Adeli
BACKGROUND: Transferrin saturation reference intervals specific for age and sex have not been previously reported for the pediatric population. The reference values for transferrin saturation have been previously reported to be lower in children compared to adults, caused by a combination of low serum iron and high serum transferrin levels in children, warranting specific reference intervals. Here we use the original iron and transferrin data from the CALIPER cohort to establish age- and sex-specific pediatric reference intervals for transferrin saturation...
March 2017: EJIFCC
https://www.readbyqxmd.com/read/28439142/amine-vs-carboxylic-acid-protonation-in-ortho-meta-and-para-aminobenzoic-acid-an-irmpd-spectroscopy-study
#13
Adam P Cismesia, Georgina R Nicholls, Nicolas C Polfer
Infrared multiple photon dissociation (IRMPD) spectroscopy and computational chemistry are applied to the ortho-, meta-, and para- positional isomers of aminobenzoic acid to investigate whether the amine or the carboxylic acid are the favored sites of proton attachment in the gas phase. The NH and OH stretching modes yield distinct patterns that establish the carboxylic acid as the site of protonation in para-aminobenzoic acid, as opposed to the amine group in ortho- and meta-aminobenzoic acid, in agreement with computed thermochemistries...
February 2017: Journal of Molecular Spectroscopy
https://www.readbyqxmd.com/read/28436456/synthesis-and-anti-obesity-effects-in-vivo-of-crotadihydrofuran-c-as-a-novel-ppar%C3%AE-antagonist-from-crotalaria-albida
#14
Qin-Hu Sun, Yu Zhang, Gui-Xin Chou
Crotadihydrofuran C (CC) from the herbs of Crotalaria albida is able to inhibit adipocyte differentiation and lipid accumulation. However, the effects of CC on obesity and metabolic disorders have not yet been elucidated. In our study, the first enantioselective synthesis of the 2-isopropenyl dihydrofuran isoflavone skeleton (CC) is described. The convenient and efficient synthetic protocols developed skilfully solve the problems of the ortho-para directing group and Suzuki coupling reaction using a boronic acid pinacol ester that was more stable and easy to obtain...
April 24, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28435723/formamidinium-iodide-crystal-structure-and-phase-transitions
#15
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/28435705/a-triclinic-polymorph-of-tri-cyclo-hexyl-phosphane-sulfide-crystal-structure-and-hirshfeld-surface-analysis
#16
Yi Jiun Tan, Chien Ing Yeo, Nathan R Halcovitch, Mukesh M Jotani, Edward R T Tiekink
The title compound, (C6H11)3PS (systematic name: tri-cyclo-hexyl-λ(5)-phosphane-thione), is a triclinic (P-1, Z' = 1) polymorph of the previously reported ortho-rhom-bic form (Pnma, Z' = 1/2) [Kerr et al. (1977 ▸). Can. J. Chem. 55, 3081-3085; Reibenspies et al. (1996 ▸). Z. Kristallogr. 211, 400]. While conformational differences exist between the non-symmetric mol-ecule in the triclinic polymorph, cf. the mirror-symmetric mol-ecule in the ortho-rhom-bic form, these differences are not chemically significant...
April 1, 2017: Acta Crystallographica. Section E, Crystallographic Communications
https://www.readbyqxmd.com/read/28434228/rapid-biodegradation-of-the-herbicide-2-4-dichlorophenoxyacetic-acid-by-cupriavidus-gilardii-t-1
#17
Xiangwei Wu, Wenbo Wang, Junwei Liu, Dandan Pan, Xiaohui Tu, Pei Lv, Yi Wang, Haiqun Cao, Yawen Wang, Rimao Hua
Phytotoxicity and environmental pollution of residual herbicides have caused much public concern during the past several decades. An indigenous bacterial strain capable of degrading 2,4-dichlorophenoxyacetic acid (2,4-D), designated T-1, was isolated from soybean field soil and identified as Cupriavidus gilardii. The strain T-1 degraded 2,4-D 3.39 times faster than the model strain Cupriavidus necator JMP134. T-1 could also efficiently degrade 2-methyl-4-chloro-phenoxyacetic acid (MCPA), MCPA isooctyl ester, and 2-(2,4-dicholrophenoxy)-propionic acid (2,4-DP)...
April 24, 2017: Journal of Agricultural and Food Chemistry
https://www.readbyqxmd.com/read/28433513/ortho-group-activation-of-a-bromopyrrole-ester-in-suzuki-miyaura-cross-coupling-reactions-application-to-the-synthesis-of-new-microtubule-depolymerizing-agents-with-potent-cytotoxic-activities
#18
John T Gupton, Scott Yeudall, Nakul Telang, Megan Hoerrner, Ellis Huff, Evan Crawford, Katie Lounsbury, Michael Kimmel, William Curry, Andrew Harrison, Wen Juekun, Alex Shimozono, Joe Ortolani, Kristin Lescalleet, Jon Patteson, Veronica Moore-Stoll, Cristina C Rohena, Susan L Mooberry, Ahmad J Obaidullah, Glen E Kellogg, James A Sikorski
New microtubule depolymerizing agents with potent cytotoxic activities have been prepared with a 5-cyano or 5-oximino group attached to a pyrrole core. The utilization of ortho activation of a bromopyrrole ester to facilitate successful Suzuki-Miyaura cross-coupling reactions was a key aspect of the synthetic methodology. This strategy allows for control of regiochemistry with the attachment of four completely different groups at the 2, 3, 4 and 5 positions of the pyrrole scaffold. Biological evaluations and molecular modeling studies are reported for these examples...
April 11, 2017: Bioorganic & Medicinal Chemistry
https://www.readbyqxmd.com/read/28433034/direct-1-h-nmr-evidence-of-spin-rotation-coupling-as-a-source-of-para-%C3%A2-ortho-h2-conversion-in-diamagnetic-solvents
#19
Camilla Terenzi, Sabine Bouguet-Bonnet, Daniel Canet
At ambient temperature, conversion from 100% enriched para-hydrogen (p-H2; singlet state) to ortho-hydrogen (o-H2; triplet state) leads necessarily to the thermodynamic equilibrium proportions: 75% of o-H2 and 25% of p-H2. When p-H2 is dissolved in a diamagnetic organic solvent, conversion is very slow and can be considered as arising from nuclear spin relaxation phenomena. A first relaxation mechanism, specific to the singlet state and involving a combination of auto-correlation and cross correlation spectral densities, can be retained: randomly fluctuating magnetic fields due to inter-molecular dipolar interactions...
April 21, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28432857/on-the-importance-of-intramolecular-hydrogen-bond-cooperativity-in-d-glucose-an-nmr-and-qtaim-approach
#20
John S Lomas, Laurent Joubert
The idea that hydrogen bond cooperativity is responsible for the structure and reactivity of carbohydrates is examined. Density functional theory and gauge-including atomic orbital calculations on the known conformers of the α and β anomers of D-glucopyranose in the gas phase are used to compute proton NMR chemical shifts and interatomic distances, which are taken as criteria for probing intramolecular interactions. Atom-atom interaction energies are calculated by the interacting quantum atoms approach in the framework of the quantum theory of atoms in molecules...
April 22, 2017: Magnetic Resonance in Chemistry: MRC
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