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https://www.readbyqxmd.com/read/28431318/assessing-seasonal-variation-of-synthetic-musks-in-beach-sands-from-oporto-coastal-area-a-case-study
#1
Vera Homem, Inês Magalhães, Arminda Alves, Lúcia Santos
Synthetic musk compounds are widely used in the formulation of several cosmetics, personal care and household products. Due to their massive and widespread use, together with some health concerns, they are considered emerging pollutants and have been detected in different environmental compartments. This study focused on the evaluation of the concentration of synthetic musks (five nitro, five polycyclic and one macrocyclic musks) in beach sands, from Oporto coastal area (Portugal), contributing to the enhancement of the knowledge of levels, trends and behaviour of these compounds in this particular matrix...
April 18, 2017: Environmental Pollution
https://www.readbyqxmd.com/read/28431257/integrated-antimicrobial-and-antifouling-ultrafiltration-membrane-by-surface-grafting-peo-and-n-chloramine-functional-groups
#2
Shuhua Hou, Jialin Xing, Xue Dong, Jifu Zheng, Shenghai Li
Ultrafiltration membranes with integrated antimicrobial and antifouling properties were fabricated using an engineering thermoplastic (carboxylated cardopoly(aryl ether ketone, PEK-COOH). Different molecular weights of PEO (Mw: 120, 350, 550) were grafted to the PEK-COOH membrane surface via EDC/NHS methodology. N-chloramine modified membranes then were prepared by simple exposure to dilute sodium hypochlorite solution. The surface grafting processes were all performed in water (i.e. without organic solvent)...
April 11, 2017: Journal of Colloid and Interface Science
https://www.readbyqxmd.com/read/28430444/molecular-structuring-and-percolation-transition-in-hydrated-sulfonated-poly-ether-ether-ketone-membranes
#3
Madhusmita Tripathy, Sunil Kumar P B, Abhijit P Deshpande
The extent of phase separation and water percolation in sulfonated membranes are the key to their performance in fuel cells. Toward this, the effect of hydration on the morphology and transport characteristics of sulfonated poly(ether ether ketone), sPEEK, membrane is investigated using atomistic molecular dynamics simulation at various hydration levels($\lambda$: number of water molecules per sulfonate group). The evolution of local morphology is investigated using structural correlations and minimum pair distances...
April 21, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28429413/vanadium-v-induced-oxidative-cross-coupling-of-various-boron-and-silyl-enolates
#4
Toru Amaya, Yuma Osafune, Yusuke Maegawa, Toshikazu Hirao
Intermolecular oxidative cross-coupling of two different enolates is one of the most useful reactions to synthesize unsymmetrical 1,4-dicarbonyl compounds. In this study, the oxovanadium(V)-induced intermolecular oxidative cross-coupling of enolates was achieved to give the corresponding unsymmetrical 1,4-dicarbonyl compounds, where combination of various boron and silyl enolates such as ketone-ester, ester-ketone, ester-ester, amide-ketone, and amide-ester enolates was adapted. These results clearly exhibit the versatility of the present oxidative cross-coupling protocol...
April 20, 2017: Chemistry, An Asian Journal
https://www.readbyqxmd.com/read/28429384/enantioselective-silver-and-amine-co-catalyzed-desymmetrizing-cycloisomerization-of-alkyne-linked-cyclohexanones
#5
Rubén Manzano, Swarup Datta, Robert S Paton, Darren J Dixon
A silver(I) and amine co-catalyzed desymmetrization of 4-propargylamino cyclohexanones for the direct enantioselective synthesis of 2-azabicyclo[3.3.1]nonanes is described. Exploiting reactivity arising from dual activation of the pendant terminal alkyne by silver(I) and the ketone moiety through transient enamine formation, this synthetically relevant transformation is easy to perform, efficient and broad in scope. High enantioselectivity (up to 96 % ee) was achieved by exploiting a significant matching effect between the chirality of a cinchona alkaloid-derived aminophosphine ligand for the silver(I) salt and the 2-bis(aryl)methylpyrrolidine catalyst which was rationalized by DFT calculations...
April 21, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28425958/reactions-of-5-indolizyl-lithium-compounds-with-some-bielectrophiles
#6
Sergey A Rzhevskii, Victor B Rybakov, Victor N Khrustalev, Eugene V Babaev
Abstract: Indolizyl-5-lithium anions react with succinic and phtalic anhidrides giving 1,4-keto acids, with oxallyl chloride giving 1,2-diketone, and with ethyl pyruvate giving 1,2-hydroxyacid. However, with α-halocarbonyl compounds, they react in different ways, forming the products of selective bromination at C-5 (with α-bromo ketones and esters of α-bromo acids) and 5-chloroacetyl indolizines.
April 20, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/28425852/discovery-of-novel-2-amino-5-substituted-1-3-4-thiadiazole-derivatives-new-utilities-for-colon-cancer-treatment
#7
Vinit Raj, Amit Rai, Ashok K Singh, Amit K Keshari, Prakruti Harshvardhanbhai Trivedi, Balaram Ghosh, Umesh Kumar, Dinesh Kumar, Sudipta Saha
In this study, we designed and synthesized (VR1 to VR35) a novel series of 1,3,4-thiadiazole derivatives from 2-amino-5-(substituted)-1,3,4-thiadiazole condensed with substituted aldehyde or ketone in the presence of glacial acetic acid via Wolff-Kishner reduction. Further, synthesized compounds were characterized by FTIR, NMR (1H and 13C), MS and elemental analyses. Before the synthesis, docking studies were performed using various molecular targets of colon cancer like IL-2, IL-6, COX-2, caspase-3, and caspase-8...
April 19, 2017: Anti-cancer Agents in Medicinal Chemistry
https://www.readbyqxmd.com/read/28425592/mesoporous-titanium-oxide-with-high-specific-surface-area-as-a-coating-for-in-tube-solid-phase-microextraction-combined-with-hplc-for-the-analysis-of-polycyclic-aromatic-hydrocarbons
#8
Xiuqin Wang, Juanjuan Feng, Yanan Bu, Yu Tian, Chuannan Luo, Min Sun
Stainless-steel wires coated with mesoporous titanium oxide were placed into a polyether ether ketone tube for in-tube solid-phase microextraction, and the coating sorbent was characterized by X-ray diffraction and scanning electron microscopy. It was combined with high performance liquid chromatography to build an online system. Using eight polycyclic aromatic hydrocarbons as the analytes, some conditions including sample flow rate, sample volume, organic solvent content and desorption time were investigated...
April 20, 2017: Journal of Separation Science
https://www.readbyqxmd.com/read/28425169/a-highly-active-manganese-catalyst-for-enantioselective-ketone-and-ester-hydrogenation
#9
Magnus B Widegren, Gavin J Harkness, Alexandra M Z Slawin, David B Cordes, Matthew L Clarke
A new hydrogenation catalyst based on a manganese complex of a chiral P,N,N ligand has been found to be especially active for the hydrogenation of esters down to 0.1 mol % catalyst loading, and gives up to 97 % ee in the hydrogenation of pro-chiral deactivated ketones at 30-50 °C.
April 20, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28423201/highly-enantioselective-allylation-of-ketones-an-efficient-approach-to-all-stereoisomers-of-tertiary-homoallylic-alcohols
#10
Marcus Brauns, Marvin Mantel, Julie Schmauck, Marian Guder, Martin Breugst, Joerg Pietruszka
Optimized protecting group for allylboronates allows the use of ketones to synthesize all isomers of quaternary homoallylic alcohols with high enantioselectivities. All symmetric isomers of the allylboronate can be prepared in high yields and diastereoselectivities using SN2' reactions. The improved reactivity of the novel protecting group is verified via 1H-NMR kinetics. Mechanistic studies using DFT calculations are conducted to investigate the new findings. Thus, the stereochemical outcome and enhanced reactivity can be rationalized...
April 19, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28422492/a-concise-efficient-and-scalable-total-synthesis-of-thapsigargin-and-nortrilobolide-from-r-carvone
#11
Dezhi Chen, P Andrew Evans
A concise, efficient and scalable synthesis of thapsigargin and nortrilobolide from commercially available (R)-(-)-carvone was developed. Our synthetic strategy is inspired by nature's carbon-carbon bond formation sequence, which facilitates the construction of a highly functionalized sesquiterpene lactone skeleton in five steps via an enantioselective ketone alkylation and a diastereoselective pinacol cyclization. We envision that this strategy will permit the construction of other members of the family, structural analogs and provide a practical synthetic route to these important bioactive agents...
April 19, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28422317/a-molecular-mechanics-and-ab-initio-prediction-of-the-1-h-chemical-shifts-of-pinanes
#12
Raymond J Abraham, M Ashley Cooper
Molecular mechanics calculations plus the application of a refined Karplus equation gave the conformations of 19 pinanes. These range from a Y-shaped geometry in the apopinene and α-pinene series to a pseudo chair conformation in β-pinene, nopinone and verbanone, a flattened chair in pinocarvone and the pinocarveols and a distorted Y shape for iso-verbanone. These structures were then used as input to predict the (1) H chemical shifts of these compounds by semi-empirical (HSPEC) and ab initio GIAO calculations, the latter at the B3LYP hybrid DFT level using 6-31++G** basis set...
April 19, 2017: Magnetic Resonance in Chemistry: MRC
https://www.readbyqxmd.com/read/28421770/selective-synthesis-of-e-and-z-allyl-nitriles-via-decarboxylative-reactions-of-alkynyl-carboxylic-acids-with-azobis-alkylcarbonitriles
#13
Francis Mariaraj Irudayanathan, Sunwoo Lee
Allyl nitriles were synthesized from the reactions of arylpropiolic acids with azobis(alkylcarbonitriles) (AIBN or ACCN). In the presence of Cu(OAc)2 as a catalyst and pyridine as the solvent, the (E)-stereoisomer was formed as the major product. This transformation shows good tolerance toward alkoxy, halogen, alcohol, amine, ester, and ketone functional groups. When the reaction was conducted with the sterically bulky amine, ethyldiisopropylamine, in the absence of a copper catalyst, the corresponding (Z)-stereoisomers were formed preferentially...
April 19, 2017: Organic Letters
https://www.readbyqxmd.com/read/28421769/x-ray-absorption-and-electron-paramagnetic-resonance-guided-discovery-of-the-cu-catalyzed-synthesis-of-multiaryl-substituted-furans-from-aryl-styrene-and-ketones-using-dmso-as-the-oxidant
#14
Yong Wu, Zhiyuan Huang, Yi Luo, Dong Liu, Yi Deng, Hong Yi, Jyh-Fu Lee, Chih-Wen Pao, Jeng-Lung Chen, Aiwen Lei
The first example of DMSO serving not only as a solvent but also as an oxidant to promote the oxidation of Cu(I) to Cu(II) has been demonstrated. X-ray absorption and electron paramagnetic resonance evidence revealed a single-electron redox process where DMSO could oxidize Cu(I) to Cu(II). The novel discovery guided the rational design of copper-catalyzed oxidative cyclization of aryl ketones with styrenes to furans, providing a new method for the synthesis of multiaryl-substituted furans from cheap and readily available starting materials...
April 19, 2017: Organic Letters
https://www.readbyqxmd.com/read/28421764/total-synthesis-of-the-claimed-structure-of-%C3%A2-hyptinin-and-structural-revision-of-natural-hyptinin
#15
Kazuto Maeda, Toshiyuki Hamada, Satoaki Onitsuka, Hiroaki Okamura
A total synthesis of (±)-hyptinin was achieved via a convergent route using the key phosphonate, cyclic ketone, and aryl Grignard components. The (1)H and (13)C NMR spectra of natural hyptinin did not agree with those of the synthesized compound. In particular, there were considerable differences between the signals assigned to the protons and carbons surrounding the lactone carbonyl group for the natural and synthesized compounds. The NMR data strongly suggested that the naturally occurring compound, hyptinin, was a structural isomer of the synthesized compound...
April 19, 2017: Journal of Natural Products
https://www.readbyqxmd.com/read/28421322/a-colorimetric-and-fluorescent-probe-based-on-michael-acceptor-type-diketopyrrolopyrrole-for-cyanide-detection
#16
Lingyun Wang, Shaochun Zhou, Derong Cao
A new probe 1 was synthesized by incorporating an α,β-unsaturated ketone to a diketopyrrolopyrrole fluorophore. The probe exhibited a selective and sensitive response to cyanide against other anions. Addition of CN(-) aqueous solution to 1 resulted in a rapid color change from pink to light yellow together with a blue shift from 518 to 421 nm, while other anions did not induce any significant color change. Furthermore, the Michael addition of cyanide to 1 elicited 98% fluorescence quenching at 608 nm, which constituted the fluorescence signature for cyanide detection...
April 18, 2017: Journal of Fluorescence
https://www.readbyqxmd.com/read/28418642/structure-and-dynamics-of-individual-diastereomeric-complexes-on-platinum-surface-studies-related-to-heterogeneous-enantioselective-catalysis
#17
Yi Dong, Guillaume Goubert, Michael N Groves, Jean-Christian Lemay, Bjørk Hammer, Peter H McBreen
The modification of heterogeneous catalysts through the chemisorption of chiral molecules is a method to create catalytic sites for enantioselective surface reactions. The chiral molecule is called a chiral modifier by analogy to the terms chiral auxiliary or chiral ligand used in homogeneous asymmetric catalysis. While there has been progress in understanding how chirality transfer occurs, the intrinsic difficulties in determining enantioselective reaction mechanisms are compounded by the multisite nature of heterogeneous catalysts and by the challenges facing stereospecific surface analysis...
April 18, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28418435/fullerenes-for-catalysis-metallofullerenes-in-hydrogen-transfer-reactions
#18
Sara Vidal, Juan Marco-Martínez, Salvatore Filippone, Nazario Martín
[60]Fullerene hybrids have successfully been used as catalysts in hydrogen transfer reactions, namely ketone reduction and N-alkylation with alcohols. Due to their poor solubility in polar solvents, these hybrids behave as homogeneous/heterogeneous catalysts that can be mechanically separated and reused several times while the final products do not need chromatographic separation.
April 18, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28418229/assembly-of-a-benzo-fused-bridged-ketone-scaffold-from-1-5-10-enediynes-through-one-pot-ruthenium-catalyzed-cyclization-iodine-mediated-oxidative-ring-expansion
#19
Yoshihiko Yamamoto, Kei-Ichiro Nishimura, Shota Mori, Masatoshi Shibuya
In the presence of a cationic Ru catalyst, 1,6-diynes bearing a terminal styryl moiety underwent [2+2+2] cyclization to produce dehydrobiphenylenes fused with a five-membered ring. Although the cycloadducts were unstable toward purification, their one-pot iodine-mediated ring expansion successfully afforded unprecedented bridged ketone products containing a benzo-fused bicyclo[3.2.1] framework.
April 18, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28418184/b-c6-f5-3-catalyzed-cascade-reduction-of-pyridines
#20
Zhi-Yun Liu, Zhi-Hui Wen, Xiao-Chen Wang
B(C6 F5 )3 has been found to be an effective catalyst for reduction of pyridines and other electron-deficient N-heteroarenes with hydrosilanes (or hydroboranes) and amines as the reducing reagents. The success of this development hinges upon the realization of a cascade process of dearomative hydrosilylation (or hydroboration) and transfer hydrogenation. The broad functional-group tolerance (e.g. ketone, ester, unactivated olefins, nitro, nitrile, heterocycles, etc.) implies high practical utility.
April 18, 2017: Angewandte Chemie
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