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Angewandte Chemie

Takao Noguchi, Seiji Shinkai
The newly developed oligophenylenevinylene (OPV)-based fluorescent (FL) chiral chemosensor (OPV-Me) for the representative enantiomeric guest, 1,2-cyclohexanedicarboxylic acid (1,2-CHDA: RR- and SS-form) showed the high chiral discrimination ability, resulting in the different aggregation modes of OPV-Me self-assembly: RR-CHDA directed the fibrous supramolecular aggregate, whereas SS-CHDA directed the finite aggregate. The consequent FL intensity toward RR-CHDA was maximum 30 times larger than that toward SS-CHDA...
July 27, 2017: Angewandte Chemie
Maurizio Prato, Francesca Arcudi, Volker Strauss, Luka Dordevic, Alejandro Cadranel, Dirk Guldi
We report the synthesis and electron donor-acceptor features of a novel nano-hybrid, in which the light harvesting and electron donating properties of a meso-tetraarylporphyrin (TArP) are combined with the electron accepting features of Nitrogen-Doped Carbon Nanodots (NCNDs). In particular, in a ultrafast process (> 1012 s-1), visible light excitation transforms the strongly quenched porphyrin singlet excited states into 225 ps lived charge separated states. On the other hand, ultraviolet light excitation triggers a non-resolvable transduction of singlet excited state energy from the NCNDs to the porphyrins, followed by the same charge separation observed upon visible light excitation...
July 27, 2017: Angewandte Chemie
Christopher Yuren Li, Shan Mei, Hao Qi, Tian Zhou
In recent decades, extensive studies have been devoted to assembling nanoparticles (NPs) into various ordered structures to achieve novel optical properties. It however still remains a challenging task to assemble NPs into cyclic one-dimensional (1D) shapes such as rings and frames. In this work, we report a directed assembly method to precisely assemble NPs into well-defined, free-standing frames using polymer single crystals (PSCs) as the template. Preformed poly(ethylene oxide) (PEO) single crystals were used as the template to direct the crystallization of block copolymer (BCP) poly(ethylene oxide)-b-poly(4-vinylpyridine) (PEO-b-P4VP), which directed gold NPs (AuNPs) to form AuNP frames...
July 27, 2017: Angewandte Chemie
Doron Shabat, Nir Hananya, Ori Green, Rachel Blau, Ronit Satchi-Fainaro
Singlet oxygen is among the ROS with the shortest life-time in aqueous media due to its extremely high reactivity. Therefore, designing sensors for detection of 1O2 is perhaps one the most challenging tasks in the field of molecular probes. Here we report a highly selective and sensitive chemiluminescence probe (SOCL-CPP) for detection of 1O2 in living cells. The probe reacts with 1O2 to form a dioxetane that spontaneously decomposes under physiological conditions through a chemiexcitation pathway to emit green light with extraordinary intensity...
July 27, 2017: Angewandte Chemie
Yujiro Hayashi, Seitaro Koshino, Kanna Ojima, Eunsang Kwon
Enantioselective total synthesis of estradiol methyl ether has been accomplished in a pot economical manner using five reaction vessels with four purifications. The key reaction is diphenylprolinol silyl ether mediated domino Michael/aldol reaction to afford bicyclo[4.3.0]nonane derivatives with A, C and D rings of steroids as a single isomer with excellent enantioselectivity. Six reactions such as oxidation, hydrogenation, formation of acid chloride, Friedel-Crafts reaction, deprotection and reduction can be carried out in the last one-pot sequence...
July 27, 2017: Angewandte Chemie
Ken-Ichi Fujita, Tomokatsu Wada, Takumi Shiraishi
A new hydrogen storage system based on the hydrogenation and dehydrogenation of nitrogen heterocyclic compounds, employing a single iridium catalyst, has been developed. Efficient hydrogen storage using relatively small amounts of solvent compared with previous systems was achieved by this new system. Reversible transformations between 2,5-dimethylpyrazine and 2,5-dimethylpiperazine, accompanied by the uptake and release of three equivalents of hydrogen, could be repeated almost quantitatively at least four times without any loss of efficiency...
July 27, 2017: Angewandte Chemie
Takashi Nishikata, Syo Ishida, Kentaro Takeuchi, Nobuhiro Taniyama, Yusuke Sunada
There are several reports on the synthesis of alkylamines, but most of the reported methods are not suitable for the synthesis of hindered amines. In this research, we found that a copper catalyst is effective for the formation of congested C-N bonds at room temperature. Control experiments revealed that a copper amide is a key intermediate. Moreover, when a chiral amine was used, a quaternary carbon stereogenic center was created with good selectivity.
July 26, 2017: Angewandte Chemie
Yugen Zhu, Wei He, Wei Wang, Chloe Pitsch, Xiaotai Wang, Xiang Wang
We report the enantioselective synthesis of tetracyclic indolines using cooperative silver(I) and chiral phosphoric acid catalysis. A variety of alkyne-tethered indoles are suitable for this process. Mechanistic studies suggest that the in situ-generated silver(I) chiral phosphate activates both the alkyne and the indole nucleophile in the initial cyclization step through an intermolecular hydrogen bond and the phosphate anion promotes proton transfer. In addition, further modifications of the cyclization products enabled stereochemistry-function studies of a series of bioactive indolines...
July 26, 2017: Angewandte Chemie
Giuseppe Ferrauto, Enza Di Gregorio, Marta Ruzza, Valeria Catanzaro, Sergio Padovan, Silvio Aime
Mobile proton containing solutes can be detected by MRI via Chemical Exchange Saturation Transfer(CEST)method. The CEST sensitivity is dramatically enhanced by using, as exchanging protons, the water molecules confined inside liposomes, properly shifted by a paramagnetic Shift Reagent. The chemical shift of the intraliposomal water resonance(δIL) is affected by the overall shape of the supramolecular system. Herein, it is shown that δIL of a spherical LipoCEST acts as a sensitive reporter of the distribution of Streptavidin proteins anchored at the Liposomes'surface by biotinylated phospholipids...
July 26, 2017: Angewandte Chemie
Sara Cuadros, Luca Dell'Amico, Paolo Melchiorre
Reported herein is a light-triggered organocatalytic strategy for the desymmetrization of achiral 2-fluoro substituted cyclopentane-1,3-diketones. The chemistry is based on an intermolecular aldol reaction of photochemically generated hydroxy-o-quinodimethanes that simultaneously forges two adjacent fully substituted carbon stereocenters, one bearing a carbon-fluorine stereogenic unit. The method uses readily available substrates, a simple chiral organocatalyst, and mild reaction conditions to afford an array of highly functionalized chiral 2-fluoro-3-hydroxycyclopentanones...
July 26, 2017: Angewandte Chemie
Liuzhu Gong, Hua-Jie Jiang, Kun Liu, Jie Yu, Ling Zhang
Brønsted acids of anionic chiral CoIII complexes have been first found to act as bifunctional phase-transfer catalysts to shuttle the substrates across interface and control stereoselectivity. The diastereomeric chiral CoIII-templated Brønsted acids with the same chiral ligands enabled a switchably enantioselective bromoamino-cyclization of olefins to afford two opposite enantiomers of 2-substituted pyrrolidines with high enantioselectivities (up to 99:1 e.r.), respectively.
July 26, 2017: Angewandte Chemie
Nikolaos Drosos, Gui-Juan Cheng, Erhan Ozkal, Bastien Cacherat, Walter Thiel, Bill Morandi
A catalytic pinacol-type, reductive rearrangement reaction of 1,2-internal diols is reported herein. Several scaffolds not usually amenable to pinacol-type reactions, such as aliphatic secondary-secondary diols, work well without the need for prefunctionalization. The reaction uses a simple boron catalyst and two silanes and proceeds through a concerted, stereoinvertive mechanism that enables the preparation of highly enantioenriched products. Computational studies have been used to rationalize the preference for migration over direct deoxygenation...
July 26, 2017: Angewandte Chemie
Jan Welch, Danny Müller, Christian Knoll, Martin Wilkovitsch, Gerald Giester, Johannes Ofner, Bernhard Lendl, Peter Weinberger, Georg Steinhauser
Crystallization of terbium 5,5'-azobis[1H-tetrazol-1-ide] (ZT) in the presence of trace amounts (~1 pmol) of americium results in 1) the concentration of Am tracer in the crystalline solids and 2) material that adopts a different crystal structure than that formed in the absence of Am. The structure found for Am-doped Tb(Am)2ZT3·24 H2O is isostructural to those found for the light Ln (La-Gd) ZT compounds, rather than that of the heavy Ln (Tb-Lu) ZT compounds. Traces of Am seem to force the Tb compound into a structure normally preferred by the lighter Ln, despite a 1E8-fold Tb excess...
July 26, 2017: Angewandte Chemie
Atsuhiro Osuka, Yasuhiro Okuda, Norihito Fukui, Jinseok Kim, Taeyeon Kim, Hua-Wei Jiang, Graeme Copley, Masaaki Kitano, Dongho Kim
meso-meso β-β β-β Triply linked subporphyrin dimer 6 was synthesized via stepwise reductive elimination of β-to-β doubly PtII-bridged subporphyrin dimer 9. Dimer 6 was characterized by spectroscopic and electrochemical measurements, theoretical caluculations, and picosecond time-resolved transient absorption spectroscopy. The X-ray diffraction analysis revealed that 6 took a bowl-shaped structure with a positive Gaussian curvature. Despite the curved structure, 6 exhibited a remarkably red-shifted absorption band at 942 nm and a small electrochemical HOMO-LUMO gap (1...
July 26, 2017: Angewandte Chemie
Robert Schlögl
Since the reduction of greenhouse gases is the top priority of the Energy Transition, primary electricity should be converted to material energy carriers. In this way electricity can be "stored" and made accessible for other applications. This Essay focuses on the integration of mobility in the Energy Transition and the development of sustainable alternatives to electricity-based transportation.
July 26, 2017: Angewandte Chemie
Jinlong Gong, Zhibin Luo, Tuo Wang, Jijie Zhang, Chengcheng Li, Huimin Li
This paper describes the introduction of a thin titanium dioxide interlayer that serves as passivation layer and dopant source for hematite (α-Fe2O3) nanoarray photoanode. This interlayer is demonstrated to boost the photocurrent by suppressing the substrate/hematite interfacial charge recombination, and increase the electrical conductivity by enabling Ti4+ incorporation. A dendritic nanostructure of this photoanode with enhanced solid-liquid junction area further improves to the surface charge collection efficiency, generating a photocurrent of ~2...
July 25, 2017: Angewandte Chemie
James Patrick Morken, Matteo Chierchia, Chunyin Law
Catalytic enantioselective conjunctive cross-coupling be-tween 9-BBN boronate complexes and aryl electrophiles can be accomplished with Ni salts in the presence of a chiral diamine ligand. The reactions furnish chiral 9-BBN derivatives in an enantioselective fashion and these are converted to chiral alcohols and amines, or engaged in other stereospecific C-C bond forming reactions.
July 25, 2017: Angewandte Chemie
Jessica Mary Walker, Bartosz Marzec, Fabio Nudelman
Early stage reaction mechanisms for aragonite promoting systems are relatively unknown, compared to the more thermodynamically stable calcium carbonate polymorph, calcite. Using cryoTEM and SEM, we identified the early reaction stages taking place during aragonite formation in a highly supersaturated solution using an alcohol-water solvent, and described an overall particle attachment growth mechanism for the system. We provide the first evidence for the solid-state transformation of amorphous calcium carbonate to aragonite, demonstrating the co-existence of both amorphous and crystalline material within the same aragonite needle...
July 25, 2017: Angewandte Chemie
Weiwei Lu, Bo Jia, Beilei Cui, Yuan Zhang, Kaisheng Yao, Yuling Zhao, Jian Ji Wang
Photoelectrochemical (PEC) reduction of CO2 is a potential way to produce fuels and chemicals by using C1-feedstock accumulated in the atmosphere. However, low solubility of CO2 in water and complicated processes of capture and conversion make the conversion efficiency quite low. In this study, a new conception of "ionic liquid assisted capture and conversion of CO2 in PEC system" is proposed and demonstrated by using 1-aminopropyl-3-methylimidazolium bromide aqueous solution as both the absorbent and electrolyte at ambient temperature and pressure...
July 25, 2017: Angewandte Chemie
Yosuke Matsuo, Ayane Yoshida, Yoshinori Saito, Takashi Tanaka
Goupiolones A and B are unique phenolic compounds with significant DNA-damaging activity. In this study, the structure of goupiolone B was revised on the basis of DFT calculations of the ¹³C NMR chemical shifts and biosynthetic considerations. The dibenzobicyclo[3.2.2]nonane skeleton of the revised structure suggested that goupiolone B was produced by oxidative coupling between catechol and goupiolone A, which was strongly supported by this biomimetic synthesis. Furthermore, the racemization of goupiolone B was observed during the examination for the chiral separation of its racemic mixture...
July 25, 2017: Angewandte Chemie
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