Read by QxMD icon Read

Chemistry: a European Journal

Xiang Ren, Qihang Guo, Jianhui Chen, Hujun Xie, Qing Xu, Zhan Lu
The visible-light-promoted diastereodivergent intramolecular oxyamination of alkenes and amination of unactivated C(Sp3)-H bonds is described to construct oxazolindinones, pyrrolidinones and imidazolidones via mild generation of primary amidyl radicals from functionalized hydroxylamines. A unique phenomenon on highly diastereoselective ring-opening of aziridines controlled by electron sacrifices was observed. High diastereoselective amino alcohols derivatives were obtained efficiently through this protocol in gram scales...
October 22, 2016: Chemistry: a European Journal
Jingzhao Xia, Guoqiang Yang, Ruijing Zhuge, Yangang Liu, Wanbin Zhang
An iridium-catalyzed asymmetric hydrogenation of unfunctionalized exocyclic C=C bonds was achieved using an axially flexible chiral phosphine-oxazoline ligand, providing the desired (S)-1-benzyl-2,3-dihydro-1H-indene products with up to 98% ee. This represents the first general hydrogenation of unfunctionalized exocyclic olefins with the highest selectivity reported thus far. The additive acetate ion plays an important role in the reaction's high enantioselectivity. The chiral product can be further transformed to key intermediates required for the synthesis of an important insecticide and a drug compound...
October 22, 2016: Chemistry: a European Journal
Salma Al-Karmi, Silvia A Albu, Alyssa Vito, Nancy Janzen, Shannon Czorny, Laura Banevicius, Max Nanao, Jon Zubieta, Alfredo Capretta, John F Valliant
Hydrocyanine dyes are sensitive "turn-on" type optical probes that can detect reactive oxygen species (ROS). We have developed a method to prepare an 18F-labeled hydrocyanine dye as a multi-modal PET and optical "turn-on" probe. A commercially available NIR dye was modified with a fluorinated prosthetic group that did not alter its ROS sensing properites in the presence of superoxide and hydroxyl radicals. The 18F-labeled analogue was produced using a single step terminal fluorination procedure. PET imaging and quantitative in vivo biodistribution studies indicated this novel probe had remarkably different pharmacokinetics compared to the oxidized cyanine analogue...
October 21, 2016: Chemistry: a European Journal
Martin Heberle, Stefanie Tschierlei, Nils Rockstroh, Mark Ringenberg, Wolfgang Frey, Henrik Junge, Matthias Beller, Stefan Lochbrunner, Michael Karnahl
A series of heteroleptic copper(I) photosensitizers of the type [(P^P)Cu(N^N)]+ with an extended π-system in the backbone of the diimine ligand have been prepared. The structures of all complexes are completely characterized by NMR spectroscopy, mass spectrometry and X-ray crystallography. These novel photosensitizers were assessed with respect to the photocatalytic reduction of protons in the presence of triethylamine and [Fe3(CO)12]. While the solid state structures and computational results show no significant impact of the π-extension on the structural properties decreased activities were observed...
October 21, 2016: Chemistry: a European Journal
Oriana Brea, Ines Corral Perez, Otilia Mo, Manuel Yañez, Ibon Alkorta, Jose Elguero
Through the use of high-level ab initio and density functional calculations we have shown that 1,8-diBeX-naphthalene (X = H, F, Cl, CN, CF₃, C(CF₃)₃) derivatives behave as anion sponges, very much as 1,8-bis(dimethylamino)naphthalene derivatives behave as proton sponges. The electron deficient nature of the BeX substituents, which favors strong charge transfer from the anion towards the former, results into anion affinities which are among the largest ones reported in the literature for single neutral molecules...
October 21, 2016: Chemistry: a European Journal
Yashwant D Vankar, Parasuraman Rajasekaran, Govind Pratap Singh, Mohammad Hassam
A "Prins-pinacol type rearrangement followed by C4-OBn participation" in a cascade manner has been observed while probing the fate of carbocation in some carbohydrate derived homoallylic alcohols in the Prins reaction. This has led to an easy access to tetrahydrofuran-fused bridged bicyclic ketals (or tetrahydrofuran-fused 1,6-anhydro-heptopyranose frameworks) which are further converted into some annulated sugars and C2-branched heptoses.
October 21, 2016: Chemistry: a European Journal
Jingquan Liu, Hongjing Ma, Huihui Zhu, Zhen Liu, Degang Jiang, Jizhen Zhang, Wenrong Yang
The determination of oxygeneous groups, conjugated area ratio and reduction efficiency of graphene oxide (GO) is a difficult task because of its heterogeneous structure. Herein, we describe a novel approach for the detailed understanding of the surface chemistry of GO using pyrene as a fluorescent probe via π-π stacking interaction.
October 21, 2016: Chemistry: a European Journal
Peter Nilsson, Marcus Bäck, Hanna Appelqvist, Harry LeVine
Deposits comprised of amyloid-β(Aβ) are one of the pathological hallmarks of Alzheimer's disease (AD) and small hydrophobic ligands targeting these aggregated species are used clinically for diagnosis of AD. Herein, we observed that anionic oligothiophenes efficiently displaced X-34, a Congo Red analogue, but not Pittsburgh compound B (PIB) from recombinant Aβ amyloid fibrils and Alzheimer's disease brain-derived Aβ. Overall, we foresee that the oligothiophene scaffold offers the possibility to develop novel high-affinity ligands for Aβ pathology only found in human AD brain, targeting a different site than PIB...
October 21, 2016: Chemistry: a European Journal
Xiao-Fang Liu, Ran Ma, Chang Qiao, Han Cao, Liang-Nian He
An effective and inexpensive organocatalyst tetrabutylammonium fluoride (TBAF) was developed for the reductive functionalization of CO2 with amines to selectively afford formamides or methylamines by employing hydrosilanes. Hydrosilanes with different substituents show discriminatory reducing activity. Thus, the formation of formamides and further reduction products, that is, methylamines could be controlled by elegantly tuning hydrosilane types. Formamides were obtained exclusively under an atmospheric pressure of CO2 with triethoxysilane...
October 21, 2016: Chemistry: a European Journal
Ondřej Jankovský, Michal Nováček, Jan Luxa, David Sedmidubský, Vlastimil Fila, Martin Pumera, Zdeněk Sofer
A new member of the family of graphene derivatives, namely, graphene acid with a composition close to C1 (COOH)1 , was prepared by oxidation of graphene oxide. The synthetic procedure is based on repeated oxidation of graphite with potassium permanganate in an acidic environment. The oxidation process was studied in detail after each step. The multiple oxidations led to oxidative removal of other oxygen functional groups formed in the first oxidation step. Detailed chemical analysis showed only a minor amount of other oxygen-containing functional groups such as hydroxyl and the dominant presence of carboxyl groups in a concentration of about 30 wt %...
October 21, 2016: Chemistry: a European Journal
Matthieu Teci, Michael Tilley, Michael A McGuire, Michael G Organ
The conversion of commercially available anilines into biaryl and biarylacetylene products was realized by using a telescoped, three-reactor flow diazotization/iododediazotization/cross-coupling process. The segmented flow stream created by off-gassing during the Sandmeyer sequence was restored to a continuous column of reaction solution by using a specially designed continuous-flow unit controlled by custom software created in-house. The resultant aryl iodide was then combined with a stream of cross-coupling solution that fed into the final reactor...
October 21, 2016: Chemistry: a European Journal
Karl Kaupmees, Robert Järviste, Ivo Leito
The basicity scale of very weak bases has been set up in 1,2-dichloroethane to give, for the first time, reliable quantitative insights into the basic properties of weak bases in a low-polarity solvent. The scale contains 30 compounds, including anilines; phosphanes, and carbonyl bases, such as esters and amides, linked by 53 relative basicity measurements. The scale spans more than 12 pKip units, expanding to as low pKip values as possible with our current experimental methodology.
October 21, 2016: Chemistry: a European Journal
Qihui Chen
A temperature and anions induced coordination-driven self-assembly system based on dynamic Ag6L4 metallocage has been developed. Induced by SbF6- anions, both of kinetic-control [Ag3L2(SbF6)3]n and thermodynamic-control [Ag2L2(SbF6)2]n can be reassembled from discrete Ag6L4(SbF6)6 metallocages at 30 ℃, raising temperature up to 40 ℃ results to selective inhibition of their kinetic product. While driven by BF4- anions, dynamic Ag6L4(BF4)6 metallocages prior to self-assemble into thermodynamic-control polycage at 25 ℃, lowing the temperature down to 0℃ leads to selective inhibition of their thermodynamic product...
October 20, 2016: Chemistry: a European Journal
Cédric Boulho, Harmen S Zijlstra, Alexander Hofmann, Peter H M Budzelaar, Sjoerd Harder
Reaction of (TBBP)AlMe⋅THF with [Cp*2 Zr(Me)OH] gave [(TBBP)Al(THF)-O-Zr(Me)Cp*2 ] (TBBP=3,3',5,5'-tetra-tBu-2,2'-biphenolato). Reaction of [DIPPnacnacAl(Me)-O-Zr(Me)Cp2 ] with [PhMe2 NH](+) [B(C6 F5 )4 ](-) gave a cationic Al/Zr complex that could be structurally characterized as its THF adduct [(DIPPnacnac)Al(Me)-O-Zr(THF)Cp2 ](+) [B(C6 F5 )4 ](-) (DIPPnacnac=HC[(Me)C=N(2,6-iPr2 -C6 H3 )]2 ). The first complex polymerizes ethene in the presence of an alkylaluminum scavenger but in the absence of methylalumoxane (MAO)...
October 20, 2016: Chemistry: a European Journal
Johanna Novacek, Joseph A Izzo, Mathew J Vetticatt, Mario Waser
Chiral bifunctional urea-containing ammonium salts were found to be very efficient catalysts for asymmetric α-hydroxylation reactions of β-ketoesters with oxaziridines under base-free conditions. The reaction is accompanied by a simultaneous kinetic resolution of the oxaziridine and a plausible and so far unprecedented bifunctional transition-state model has been obtained by means of DFT calculations.
October 20, 2016: Chemistry: a European Journal
Zhong-Xia Wang, Fen-Ying Kong, Wei Wang
Graphene quantum dots-like structures of highly enriched nitrogen-based dual-color single-functional polymer carbon nanosheets (GLNPCNs) with an average diameter as large as 170 nm (~5 layers) are prepared by a facile hydrothermal method. Intermolecular C5H5N5···C5H5N5 or/and C2H5OH chemical polymerization interactions in the liquid state of the peripheral crown ether-like "hole" decorated compound GLNPCNs lead to a fascinating 2D supramolecular polymer architecture, which exhibits near-ultraviolet (NUV) fluorescence, narrow full width at half maximum, and excellent practical application capability...
October 20, 2016: Chemistry: a European Journal
Narcis Avarvari, Thomas Biet, Kévin Martin, Jihane Hankache, Nora Hellou, Andreas Hauser, Thomas Bürgi, Nicolas Vanthuyne, Tal Aharon, Marco Caricato, Jeanne Crassous
Introduction of heterocycles in the helical skeleton of helicenes allows modulation of their redox, chiroptical and photophysical properties. Herein, we describe the straightforward preparation and structural characterization by single crystal X-ray diffraction of thiadiazole-[7]helicene, which has been resolved into (M) and (P) enantiomers by chiral HPLC, together with its S-shaped double [4]helicene isomer, as well as the smaller congeners thiadiazole-[5]helicene and benzothiadiazole-anthracene. A copper(II) complex with two thiadiazole-[5]helicene ligands has been structurally characterized and it shows the presence of both (M) and (P) isomers coordinated to the metal centre...
October 20, 2016: Chemistry: a European Journal
Parthasarathi Dastidar, Koushik Sarkar
A mixed ligand approach was exploited to synthesize a new series of MnII based coordination polymers (CPs), namely, CP1 {[Mn(-dpa)(-4,4-bp)]MeOH}α, CP2 {[Mn3(-dpa)3(2,2-bp)2]}α, CP3 {[Mn3(-dpa)3(1,10-phen)2]2H2O}α, CP4 {[Mn(-dpa)(-4,4-bpe)1.5]H2O}α, CP5 {[Mn2(-dpa)2(-4,4-bpe)2]½DEF}α and CP6 {[Mn(-dpa)(-4,4-bpe)1.5]½DMA}α, [dpa = 3,5-dicarboxy phenyl azide, 2,2-bp = 2,2-bipyridine, 1,10-phen = 1,10-phenanthroline, 4,4-bpe = 1,2-bis(4-pyridyl)ethylene, 4,4-bp = 4,4-bipyridine, DEF = N,N-diethylformamide, DMA = N,N-dimethylacetamide] to develop multifuntional CPs...
October 20, 2016: Chemistry: a European Journal
Yingxiao Cai, Andreas Benischke, Paul Knochel, Corinne Gosmini
A simple and efficient protocol for the direct reductive cross-coupling between alkenyl and benzyl halides using a Co/Mn system has been developed. This reaction proceeds smoothly in the presence of [CoBr2(PPh3)2] as catalyst, with NaI as additive in acetonitrile with a broad scope of functionalized alkenyl and benzyl halides. Different functional groups are tolerated on both coupling partners, thus, significantly extending the general scope of transition-metal-catalyzed benzylation of alkenyl halides. Moderate to excellent yields were obtained...
October 20, 2016: Chemistry: a European Journal
Xiaoyang Shi, Hang Xiao, Klaus Lackner, Xi Chen
A great deal of information exists concerning the hydration of ions in bulk water. Much less noticeable, but equally ubiquitous is the hydration of ions holding on to several water molecules in nanoscopic pores or in natural air at low relative humidity. Such hydration of ions with a high ratio of ions to water molecules (up to 1:1) are essential in determining the energetics of many physical and chemical systems. Here we present a quantitative analysis of the energetics of ion hydration in nanopores based on molecular modeling of a series of basic salts associated with different numbers of water molecules...
October 20, 2016: Chemistry: a European Journal
Fetch more papers »
Fetching more papers... Fetching...
Read by QxMD. Sign in or create an account to discover new knowledge that matter to you.
Remove bar
Read by QxMD icon Read

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"