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Angewandte Chemie

Julietta Yedoyan, Nikolai Wurzer, Urszula Klimczak, Thomas Ertl, Oliver Reiser
The palladium-catalyzed coupling between aryl halides and monocyclopropanated pyrroles or furans has been developed leading to valuable six-membered N- and O-heterocycles. As the key step, a selective cleavage of the non-activated endocyclic C-C bond of the 2-heterobicyclo-[2.1.0]hexane framework is achieved. The developed method offers an access to highly functionalized piperidines, pyridines and pyrans that are challenging to access by traditional methods.
November 12, 2019: Angewandte Chemie
Dana Kaizerman-Kane, Maya Hadar, Noam Tal, Roman Dobtovetsky, Yossi Zafrani, Yoram Cohen
We describe the preparation of the first water-soluble pH-responsive supramolecular hexagonal boxes (SHBs) based on multiple charge-assisted hydrogen bonds between peramino-pillar[6]arenes 2 with the molecular "lid" mellitic acid (1a). The interaction between 2 and 1a, as well as the other "lids" pyromellitic and trimesic acids (1b and 1c, respecively) were studied by a combination of experimental and computational methods. Interestingly, the addition of 1a to the complexes of the protonated form of pillar[6]arene 2, i...
February 20, 2019: Angewandte Chemie
Qingjing Yang, Yanbo Wang, Shihui Luo, Jun Wang
A highly efficient kinetic resolution and dynamic kinetic resolution of chromene is reported for the first time via a Rh-catalyzed asymmetric hydroarylation pathway. This newly developed approach offers a versatile access of various chiral 2,3-diaryl-chromenes containing two vicinal stereogenic centers as well as the recovered chiral flavenes in high yields with excellent ee (s factor is up to 532). Particularly noteworthy is that this strategy can be further extended to the establishment of a dynamic version of kinetic resolution of chromene acetals, in which it allows complete access of chiral isoflavanes and α-aryl hydrocoumarin successfully...
February 20, 2019: Angewandte Chemie
Austin D Marchese, Florian Lind, Áine E Mahon, Hyung Yoon, Mark Lautens
A diastereoselective dearomative carboiodination reaction is reported. We report a novel metal-catalyzed approach to install reactive secondary benzylic iodides. Utilizing the unique reactivity of nickel, we have expanded the carboiodination reaction onto non-activated aromatic double bonds forming a previously unattainable class of iodides. We also report a broadly applicable method to avoid the use of a metallic reducing agent by utilizing an alkyl phosphite as the ligand. The reaction is thought to proceed through a syn intramolecular carbonickelation onto a 2-substituted indole followed by a diastereoretentive reductive elimination of the carbon-iodine bond...
February 20, 2019: Angewandte Chemie
Hans-Jörg Himmel
Electron-deficient small boron rings are unique in their formation of sigma- and pi-delocalized electron systems, and the avoidance of "classical" structures in terms of two-center-two-electron (2c,2e) bonds. These rings are tolerant to several skeletal electron numbers, making their redox-chemistry highly interesting. In the past decades, the synthesis of a range of stable compounds with varying electron numbers in the B3 and B4 cores was achieved. In alliance with quantum-chemical calculations the electronic structures were evaluated...
February 20, 2019: Angewandte Chemie
Philipp Gotico, Bernard Boitrel, Régis Guillot, Marie Sircoglou, Annamaria Quaranta, Zakaria Halime, Winfried Leibl, Ally Aukauloo
Inspired by nature's orchestra of chemical subtleties to activate and reduce CO2 , we have developed a family of iron porphyrin derivatives in to which we have introduced urea groups functioning as multipoint hydrogen-bonding pillars on the periphery of the porphyrinic ring. This structure closely resembles the hydrogen-bond stabilization scheme of the carbon dioxide (CO2 ) adduct in the carbon monoxide dehydrogenase (CODH). We found that such changes to the second coordination sphere significantly lowered the overpotential for CO2 reduction in this family of molecular catalysts and importantly increased the CO2 binding rate while maintaining high turnover frequency (TOF) and selectivity...
February 20, 2019: Angewandte Chemie
Alexey Alexandrovich Popov, Georgios Velkos, Denis Krylov, Kyle Kirkpatrick, Lukas Spree, Vasilii Dubrovin, Bernd Büchner, Stanislav Avdoshenko, Valeriy Bezmelnitsyn, Sean Davis, Paul Faust, James Duchamp, Harry Dorn
The azafullerene Tb2@C79N is found to be a single molecule magnet with a high 100-s blocking temperature of magnetization of 24 K and large coercivity. Tb magnetic moments with an easy-axis single-ion magnetic anisotropy are strongly coupled by the unpaired spin of the single-electron Tb-Tb bond. Relaxation of magnetization in Tb2@C79N below 15 K proceeds via quantum tunneling of magnetization with the characteristic time τQTM = 16462±1230 s. At higher temperature, relaxation follows the Orbach mechanism with a barrier of 757±4 K, corresponding to the excited states, in which one of the Tb spins is flipped...
February 20, 2019: Angewandte Chemie
Oliver Trapp, Jan Felix Scholtes
Supramolecular ligands offer a variety of possibilities to control selectivity in catalysis due to their non-covalent interactions with other molecules. Conceptionally, enantioselectivity can be induced by interaction of chiral additives or products with the interaction sites of a supramolecular catalyst. However, the design of such catalysts is very challenging due to the complex fusion of recognition sites and catalytically active center. Here, we report the design of a new class of fluxional biphenyl bisphosphinite (BIBIPHOS) ligands decorated with amino acid-based diamide interaction sites that undergo spontaneous desymmetrization...
February 20, 2019: Angewandte Chemie
Xu Liu, Chen-Gang Wang, Atsushi Goto
Molecular weight distribution of polymer, termed dispersity (Đ), is a fundamental key parameter for determining polymer material properties. This paper reports a novel approach for controlling Đ, exploiting a temperature-selective radical generation in organocatalyzed living radical polymerization. The polymers with tailored Đ were synthesized in a batch system without the assistance of an external pump. A unique aspect of this approach is that Đ was tuneable from 1.11 to 1.50 in any segments in diblock, triblock, and multi-block copolymers and any forms of star and brush polymers without segmental or topological restriction...
February 20, 2019: Angewandte Chemie
Klara Edel, Jacob S A Ishibashi, Shih-Yuan Liu, Holger F Bettinger
The BN analogue of ortho-benzyne, 1,2-azaborine, is shown to bind carbon monoxide and a xenon atom under matrix isolation conditions, demonstrating its strongly Lewis acidic superelectrophilic nature. The Lewis acid-base complexes involving CO and Xe can be cleaved photochemically and reformed by mildly annealing the matrices. The interaction energy of 1,2-azaborine with Xe is 3 kcal mol-1 according to quantum chemical computations, and is similar to that of the superelectrophilic carbene difluorovinylidene...
February 20, 2019: Angewandte Chemie
Yang Zheng, Junqi Zhang, Xinpeng Cheng, Xinfang Xu, Liming Zhang
Gold-catalyzed oxidations of alkynes by N-oxides offer a direct access to reactive α-oxo gold carbene intermediates from benign and readily available alkynes instead of hazardous diazo carbonyl compounds. Despite various versatile synthetic methods developed based on this strategy, one of the hallmarks of α-oxo carbene/carbenoid chemistry, i.e., the Wolff rearrangement, has not been realized in this context. This study discloses the first examples that the Wolff rearrangement can be readily realized by α-oxo gold carbenes oxidatively generated from TBS-terminated alkynes...
February 20, 2019: Angewandte Chemie
Huile Jin, Jun Li, James Iocozzia, Xin Zeng, Pai-Chun Wei, Chao Yang, Nan Li, Zhaoping Liu, Jr Hau He, Tiejun Zhu, Jichang Wang, Zhiqun Lin, Shun Wang
Hybrid organic-inorganic materials have been considered as a new candidate in the field of thermoelectric materials from the last decade due to their great potential to enhance the thermoelectric performance by utilizing the low thermal conductivity of organic materials and the high Seebeck coefficient, and high electrical conductivity of inorganic materials. Herein, we provide an overview of interfacial engineering in the synthesis of various organic-inorganic thermoelectric hybrid materials, along with the dimensional design for tuning their thermoelectric properties...
February 20, 2019: Angewandte Chemie
Alberto Credi
The controlled transport of molecular and ionic substrates across bilayer membranes is a fundamental task for the operation of living organisms. It is also a highly fascinating and demanding challenge for artificial molecular machines. The recent report of a synthetic transmembrane molecular shuttle that can transport potassium ions selectively down a gradient in a liposomal system makes a small but significant step towards this goal.
February 20, 2019: Angewandte Chemie
Yishai Albeck, Katharine Lunny, Yanice Benitez, Ashley Shin, Daniel Strasser, Robert Continetti
The photoexcitation of cold oxyallyl anions was studied below the adiabatic detachment threshold at a photon energy of 1.60 eV. Photodetachment was observed through two product channels, delayed electron emission from a long-lived anionic state and dissociative photodetachment via absorption of a second photon. The former produced stable C₃H₄O neutrals, while the latter resulted in the concerted elimination of CO + C₂H₄ products. The neutral oxyallyl singlet state has a barrier-free route to cyclopropanone as well as zwitterionic character with a large charge separation and dipole moment...
February 19, 2019: Angewandte Chemie
Rui Feng, Li Zhang, Huapeng Ruan, Yue Zhao, Gengwen Tan, Xinping Wang
The first main-group element radical based one-dimensional magnetic chain (1K)n was realized by one-electron reduction of the pyridinyl functionalized borane 1 with elemental potassium in THF in the absence of 18-crown-6 (18-c-6). The electron spin density of (1K)n mainly resides at the boron centers with a considerable contribution from central benzene and pyridine moieties. The spin centers exhibit an antiferromagnetic interaction as demonstrated by magnetic measurements and theoretical calculations. In contrast, the reduction in the presence of 18-c-6 afforded the separated radical anion salt 1K(Crown), in which the potassium cation was trapped by THF and 18-c-6 molecules...
February 19, 2019: Angewandte Chemie
Alexandria Mullins, Nicholas Pinkin, Joshua Hardin, Marcey L Waters
The methylation states of Lys and Arg represent a particularly challenging set of targets to distinguish selectively in water using synthetic receptors. To date, Kme3 is the only post translational modification (PTM) of the eight possible methylation states of Lys and Arg that can be recognized selectively. Here we report the first synthetic receptor capable of selectively recognizing Rme2a. This was achieved using a biased DCC library to generate a receptor mimicking the 5-sided box-like shape of Rme2 reader proteins, a feature that has been hypothesized to impart selectivity...
February 19, 2019: Angewandte Chemie
Lucrezia Angelini, Jacob Davies, Marco Simonetti, Laia Malet Sanz, Nadeem S Sheikh, Daniele Leonori
Here we report a strategy for the generation of nitrogen-radicals by ground-state single electron transfer with organyl-Ni(I) species. Depending on the philicity of the N-radical, two types of processes have been developed. In the case of nucleophilic aminyl radicals direct N-arylation with aryl organozinc, organoboron and organosilicon reagents was achieved. In the case of electrophilic amidyl radicals, cascade processes involving intramolecular cyclization, followed by reaction with both aryl and alkyl organometallics have been developed...
February 19, 2019: Angewandte Chemie
Shang-Fu Yuan, Cong-Qiao Xu, Jun Li, Quan-Ming Wang
A "golden fullerene" Au32 cluster has been synthesized with amido and phosphine ligands as the protecting agents. Single crystal X-ray structural analysis reveals that this gold nanocluster [Au32(Ph3P)8(dpa)6] (SbF6)2 (Hdpa = 2, 2'-dipyridylamine) has a stable pseudo-Ih Au328+ core with S6 symmetry, which features an Au12@Au20 Keplerate cage co-protected by Ph3P and dpa ligands. Quantum chemical studies elucidate the nature of the special stability of this cluster and suggest that it is electronically stabilized via metal-ligand interaction...
February 19, 2019: Angewandte Chemie
Tom Stennett, Philipp Bissinger, Stefanie Griesbeck, Stefan Ullrich, Ivo Krummenacher, Michael Auth, Andreas Sperlich, Matthias Stolte, Krzysztof Radacki, Chang-Jiang Yao, Frank Würthner, Andreas Steffen, Todd Marder, Holger Braunschweig
In this work, two new quadrupolar A-π-D-π-A chromophores have been prepared featuring a strongly electron-donating diborene core and strongly electron-accepting dimesitylboryl (BMes2) and bis(2,4,6-tris(trifluoromethyl)phenyl)boryl (BFMes2) end groups. Analysis of the compounds by NMR spectroscopy, X-ray crystallography, cyclic voltammetry and UV-vis-NIR absorption and emission spectroscopy indicated that the compounds possess extended conjugated π-systems spanning their B4C8 cores. The combination of exceptionally potent π-donor (diborene) and π-acceptor (diarylboryl) groups, both based on trigonal boron, leads to very small HOMO-LUMO gaps, resulting in strong absorption in the near-IR region with maxima in THF at 840 and 1092 nm, respectively, and very high extinction coefficients of ca...
February 19, 2019: Angewandte Chemie
Zhao-Quan Yao, Jian Xu, Bo Zou, Zhenpeng Hu, Kang Wang, Yi-Jia Yuan, Ya-Ping Chen, Rui Feng, Jian-Bo Xiong, Jialei Hao, Xian-He Bu
We herein report a new coordination network that deforms in a smooth and reversible manner under either thermal or pressure stimulation. Concomitantly, the organic fluorophores coordinatively bound to the channel in a face-to-face arrangement respond to this structural deformation by finely adapting their conformation and arrangement. As a result, the material exhibits a remarkable dual-stimuli-responsive luminescence shift across almost the entire visible region: The emission color of the crystal gradually changes from cyan to green by heating and then to red by pressure compression...
February 19, 2019: Angewandte Chemie
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