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Chemistry: a European Journal

Bishnu P Joshi, Joseph Hardie, Michelle E Farkas
The accumulation of therapeutic and imaging agents at sites of interest is critical to their efficacy. Similarly, off-target effects (especially toxicity) are a major liability for these agents. For this reason, the use of delivery vehicles to improve the distribution characteristics of bio-active agents has become ubiquitous in the field. However, the majority of traditionally employed, cargo-bearing entities rely on passive accumulation. Even in cases where 'targeting' functionalities are used, the agents must first reach the site in order for the ligand-receptor interaction to occur...
March 15, 2018: Chemistry: a European Journal
Barry M Trost, Chris Kalnmals
Herein, we report a valuable umpolung strategy that highlights the ambiphilic nature of the bis(phenylsulfonyl)methyl synthon and demonstrates its utility as a synthetic linchpin. While the bis(phenylsulfonyl)methyl group is typically introduced as an sp3 carbon nucleophile, we demonstrate that it can also function as an effective sp2 carbon electrophile in the presence of organolithium nucleophiles. Akyl- and aryllithiums couple with the central carbon of the bis(phenylsulfonyl)methyl unit to ultimately generate trisubstituted alkenes, comprising a formal sp3-sp2 and sp2-sp2 cross-coupling between organolithiums and bis(sulfones)...
March 15, 2018: Chemistry: a European Journal
Artur Lik, Sangeth Jenthra, Lars Fritze, Lars Müller, Khai-Nghi Truong, Holger Helten
The application of our newly developed B-C coupling method by catalytic Si/B exchange is demonstrated for the synthesis of a series of triarylboranes (1), monodisperse thienyl- and furylborane dimers (2) and trimers (9), extended oligomers (3) and polymers (3'), as well as mixed (oligo)thienyl-/furylboranes. The structures of 1aaTip, 1bbTip, and 2bbbMes*, determined by X-ray crystallography, reveal largely coplanar hetarene rings and BR3 environments, being most pronounced in the furylborane species. Photophysical investigations, supported by TD-DFT calculations, revealed pronounced pi-electron delocalization over the hetarene backbones including the boron centers...
March 15, 2018: Chemistry: a European Journal
Jun Zhang, Alexander Sandberg, Audun Konsmo, Xiongyu Wu, Sofie Nyström, K Peter Nilsson, Peter Konradsson, Harry LeVine, Mikael Lindgren, Per Hammarström
We revisited the Congo red analogue 2,5-bis(4'-hydroxy-3'-carboxy-styryl)benzene (X-34) to develop this highly fluorescent amyloid dye for imaging Alzheimer's disease (AD) pathology comprising Aβ and Tau fibrils. A selection of ligands with distinct optical properties were synthesized by replacing the central benzene unit of X-34, with other heterocyclic moieties. Full photophysical characterization was performed determining absorbance and fluorescence spectra, Stokes shift, quantum yield and fluorescence lifetimes...
March 15, 2018: Chemistry: a European Journal
Daniel Sutherland, Luke Kinsman, Stuart M Angiolini, Georgina M Rosair, Ai-Lan Lee
Hydroarylation of enantioenriched 1,3-disubstituted allenes has the potential to proceed with axial-to-point chirality transfer to yield enantioenriched allylated (hetero)aryl compounds. However, the gold-catalysed intermolecular reaction was previously reported to occur with no chirality transfer, due to competing allene racemisation. In this full article, we describe the development of the first intermolecular hydroarylations of allenes to proceed with efficient chirality transfer, and summarise some of the key criteria for achieving high regio- and stereoselectivities...
March 15, 2018: Chemistry: a European Journal
Liancheng Bing, Aixiu Tian, Fang Wang, Kaifeng Yi, Xingyuan Sun, Guangjian Wang
Hierarchical SSZ-13 microspheres with abundant mesoporous channels have been successfully synthesized by addition of calcined SSZ-13 crystals in the starting gel in the absence of any organic templates. This strategy not only remarkably reduces the production cost and environmental pollution but also significantly decreases the crystallization time as well as evidently reducing the zeolite crystal sizes in many cases. The synthesized sample was characterized by XRD, BET, ICP, SEM, TEM, TG, and NH3-TPD, which indicates that the organic template free synthesized SSZ-13 exhibits high crystallinity, textural properties, and acidity...
March 15, 2018: Chemistry: a European Journal
Thomas George Back, Kai N Sands, Tyler A Tuck
Selenium compounds play an important role in redox homeostasis in living organisms. One of their major functions is to suppress the harmful effects of hydrogen peroxide, hydroperoxides and downstream reactive oxygen species that lead to oxidative stress, which has in turn been implicated in many diseases and degenerative conditions. The glutathione peroxidase (GPx) family of selenoenzymes plays a key protective role by catalyzing the reduction of peroxides with glutathione. Considerable effort has been expended toward the discovery of small-molecule selenium compounds that mimic GPx...
March 14, 2018: Chemistry: a European Journal
Nazario Martin, Alicia López-Andarias, Javier López-Andarias, Carmen Atienza, Francisco J Chichón, José L Carrascosa
Supramolecular chemistry has evolved from the traditional focus on thermodynamic on-pathways to the complex study of kinetic off-pathways, which are strongly dependent of the environmental conditions. Moreover, the control over pathway complexity allows obtaining nanostructures that are inaccessible through spontaneous thermodynamic processes. Here, we present a family of peptide-based π-extended tetrathiafulvalene (exTTF) molecules which show two self-assembly pathways leading to two distinct J-aggregates, namely metastable (M) and thermodynamic (T), with different spectroscopic, chiroptical and electrochemical behavior...
March 14, 2018: Chemistry: a European Journal
Yasuaki Kawaguchi, Asami Nagata, Kei Kurokawa, Haruna Yokosawa, Chisato Mukai
Treatment of dodecatrienyne derivatives with [RhCl(CO)2]2 in refluxing toluene effected the cycloisomerization to produce tricyclo[,6]dodecadienes. The one-carbon shortened undecatrienyne derivatives, however, afforded bicyclo[6.3.0]undecatriene derivatives instead of tricyclic compounds, the latter of which are well known as a basic skeleton of naturally occurring octanoids. On the basis of two experiments with deuterated substrates, a plausible reaction mechanism for the construction of these products was proposed...
March 14, 2018: Chemistry: a European Journal
Atsuhiro Osuka, Keisuke Fujimoto
PtII-catalyzed cyclization of β-to-β ethynylene-bridged meso-amino NiII porphyrin dimer 4 followed by oxidation with PbO2 afforded 1,5-naphthyridine-fused porphyrin dimer 5 in good yield. This dimer possesses a redox-active 1,4-diazabutadiene linkage that is interconvertible with its reduced 1,2-diaminoethene linkage upon treatments with NaBH4 or PbO2. The dimer 5 exhibits an intense NIR absorption and a narrow HOMO-LUMO gap with a remarkably low reduction potential mainly owing to effective bonding interaction in the LUMO through the 1,4-diazabutadiene linkage...
March 13, 2018: Chemistry: a European Journal
Etienne Duguet, Jiaji Cheng, Nicolas Mallet, Walid Baaziz, Ovidiu Ersen, Emilie Gombart, Valérie Alard, Jérôme Majimel, Marie-Hélène Delville, Mona Tréguer-Delapierre
Original titania nanocages are fabricated from sacrificial silica/polystyrene tetrapod-like templates. Here are described the template synthesis, titania deposition and nanocage development through polystyrene dissolution and subsequent silica etching. Discussion about the competitive deposition of titania on the biphasic templates is particularly emphasized. The morphology of the nanocages is investigated by TEM, STEM, EDX mapping and electron tomography.
March 13, 2018: Chemistry: a European Journal
Juan García de la Concepción, Martín Ávalos, Pedro Cintas, José Luis Jiménez
Computational strategies have gained increasing impact in the de novo design of large molecular sets targeted to a desired application. Here, we show that DFT-assisted theoretical analyses of cycloadditions involving mesoionic dipoles and strained cycloalkynes unveil a series of unexplored mesomeric betaines as vastly superior candidates for orthogonal applications. Thus, isosydnones, thiosydnones, and a six-membered homolog in particular, 6-oxo-1,3-oxazinium-4-olate, do exhibit enhanced reactivity with respect to sydnones, the archetypal mesoionic ring employed so far in orthogonal chemistry...
March 13, 2018: Chemistry: a European Journal
Anne Harrison-Marchand, Jie Guang, Romain Duwald, Jacques Maddaluno, Hassan Oulyadi, Sami Lakhdar, Annie-Claude Gaumont
The synthesis and identification of unprecedented gem-dianionic phosphorus compounds, i.e. gem-dilithium phosphido-boranes Li2[RP*BH3], with R = Ph or Cy, are reported in THF solution. Those are obtained by double deprotonation of the corresponding primary phosphine-borane precursors RPH2*BH3. Their in-depth structural study, based on multinuclear (1H, 6Li, 7Li, 11B, 13C, 31P) mono- and bi-dimensional NMR analyses, indicates a strong influence of the phosphorus substituent on the structure of the gem-dianionic phosphorus structure: while a monomeric arrangement is obtained when R = phenyl, a cyclic oligomer is observed for R = cyclohexyl...
March 13, 2018: Chemistry: a European Journal
Joseph B Sweeney, Anthony Ball, Luke Smith
A 'totally catalytic' nickel(0)-mediated method for base-free direct alkylation of allyl alcohols and allyl amines is reported. The reaction is selective for monoallylation, uses an inexpensive Ni(II) precatalyst system, and requires no activating reagents to be present.
March 13, 2018: Chemistry: a European Journal
Mathieu Jérôme Achard, Hortense Lauwick, Yang Sun, Huriye Akdas-Kilig, Sylvie Derien
The site and regioselective allylation reaction of 2-substituted indoles was carried out by using a ruthenium(IV) precatalyst containing phosphine-sulfonate chelate. Mono-, di- and tri-allylated indoles could be selectively obtained according to reaction conditions and gave only water as byproduct. The preparation of 3-oxindole derivatives was then successfully performed owing to the oxidation under air of the corresponding allylated indoles. Diallylated pseudoindoxyls were proved to be good synthons to perform cyclization through Ring Closing Metathesis affording the corresponding tricyclic adducts...
March 13, 2018: Chemistry: a European Journal
Fengkun Chen, Takayuki Tanaka, Tadashi Mori, Atsuhiro Osuka
Polycyclic heteroaromatic compounds including pyrrole units are promising functional scaffolds owing to their electron-rich nature, bright fluorescence, and applicability to anion recognition at the pyrrolic hydrogen. We report herein the effective synthesis of pseudo-aza[5]helicene and aza[7]helicene derivatives, and unexpected formation of azahepta[8]circulenes by oxidative fusion reactions. By choosing reaction conditions and peripheral substituents attached at the terminal indole moieties, we obtained aza[7]helicenes 10a-c and azahepta[8]circulenes 11a,c selectively in moderate to good yields...
March 13, 2018: Chemistry: a European Journal
Markus Gallei, Christian Rüttiger
: Metallopolymers with metal functionalities are a unique class of functional materials. Their redox-mediated optoelectronic and catalytic switching capabilities, their outstanding structure formation and separation capabilities have been reported recently. Within this Minireview, scope and limitations of intriguing ferrocene-containing systems will be discussed. In the first section recent advances in metallopolymer design will be given leading to a plethora of novel metallopolymer architectures. Discussed synthetic pathways comprise controlled and living polymerization protocols as well as surface immobilization strategies...
March 13, 2018: Chemistry: a European Journal
Mohammadali Foroozandeh, Gareth Morris, Mathias Nilsson
Broadband homodecoupling techniques in NMR, also known as "pure shift" methods, aim to enhance spectral resolution by suppressing the effects of homonuclear coupling interactions to turn multiplet signals into singlets. Such techniques typically work by selecting a subset of "active" nuclear spins to observe, and selectively inverting the remaining, "passive", spins to reverse the effects of coupling. Pure Shift Yielded by Chirp Excitation (PSYCHE) is one such method; it is relatively recent, but has already been successfully implemented in a range of different NMR experiments...
March 13, 2018: Chemistry: a European Journal
Takaaki Yamamoto, Koki Mitsuno, Shigeki Mori, Shuhei Itoyama, Yoshihito Shiota, Kazunari Yoshizawa, Masatoshi Ishida, Hiroyuki Furuta
Complexation of a RuCp* cation with N-confused tetraarylporphyrins (NCPs) forms directly bound ruthenium(II) pentamethylcyclopentadienyl (Cp*) π-complex on a specific meso-aryl group (e.g., phenyl) neighbouring peripheral imino nitrogen of NCPs in high yields. In contrast, in the case of NCPs bearing bulky meso-substituents (e.g., 3,5-di-tert-butylphenyl), novel ruthenocenophane-like complex embedded on an N-confused calix[4]phyrin was formed through multiple C-H bond activation of methyl groups of Cp* ligand...
March 13, 2018: Chemistry: a European Journal
David Parker, Edward Walter, Gareth Williams
A series of three europium(III) complexes has been created in which an APTRA moiety has been integrated into the sensitising chromophore (APTRA = o-aminophenol-N,N,N-triacetate). The constitutionally isomeric complexes EuL1 and EuL2 feature the APTRA unit linked to a metal-bound pyridine ring through an alkynyl unit, differing according to the disposition of the APTRA substituents relative to the C≡C unit (para-N and para-O respectively). In EuL3, the APTRA ring is directly bonded to the Eu-coordinated pyridine (para-O)...
March 13, 2018: Chemistry: a European Journal
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