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Journal Cover Angewandte Chemie International Edition
  [SJR: 6.229]   [H-I: 397]   [236 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1433-7851 - ISSN (Online) 1521-3773
   Published by John Wiley and Sons Homepage  [1592 journals]
  • Synthesis and Electronic Structure of Boron-Graphdiyne with an
           sp-Hybridized Carbon Skeleton and Its Application in Sodium Storage
    • Authors: Ning Wang; Xiaodong Li, Zeyi Tu, Fuhua Zhao, Jianjiang He, Zhaoyong Guan, Changshui Huang, Yuanping Yi, Yuliang Li
      Abstract: Boron-graphdiyne (BGDY), which has a unique π-conjugated structure comprising an sp-hybridized carbon skeleton and evenlydistributed boron heteroatoms in a well-organized 2D molecular plane, is prepared through a bottom-up synthetic strategy. Excellent conductivity, a relatively low band gap and a packing mode of the planar BGDY are observed. Notably, the unusual bonding environment of the all sp-carbon framework and the electron-deficient boron centers generates affinity to metal atoms, and thus provides extra binding sites. Furthermore, the expanded molecule pores of the BGDY molecular plane can also facilitate the transfer of metal ions in the perpendicular direction. The practical effect of the all sp-carbon structure and boron heteroatoms on the properties of BGDY are demonstrated in its performance as the anode in sodium-ion batteries.The Bs needs: Boron-graphdiyne (BGDY) is prepared through a bottom-up chemical strategy. BGDY has a unique structure with molecular pores decorated with boron atoms. The pure sp-hybridized-carbon skeleton and boron heteroatoms can stabilize the metal atoms intercalated in the BGDY framework. As a result of this unique structure, BGDY shows remarkable electrochemical performance in sodium-ion half cells.
      PubDate: 2018-02-21T05:55:55.555675-05:
      DOI: 10.1002/anie.201800453
       
  • Conformation-Enabled Total Syntheses of Ohmyungsamycins A and B and
           Structural Revision of Ohmyungsamycin B
    • Authors: Joonseong Hur; Jaebong Jang, Jaehoon Sim, Woo Sung Son, Hee-Chul Ahn, Tae Sung Kim, Yern-Hyerk Shin, Changjin Lim, Seungbeom Lee, Hongchan An, Seok-Ho Kim, Dong-Chan Oh, Eun-Kyeong Jo, Jichan Jang, Jeeyeon Lee, Young-Ger Suh
      Abstract: The first total syntheses of the bioactive cyclodepsipeptides ohmyungsamycin A and B are described. Key features of our synthesis include the concise preparation of a linear cyclization precursor that consists of N-methyl amides and non-proteinogenic amino acids, and its macrolactamization from a bent conformation. The proposed structure of ohmyungsamycin B was revised based on its synthesis. The cyclic core of the ohmyungsamycins was shown to be responsible for the excellent antituberculosis activity, and ohmyungsamycin variants with truncated chains were evaluated for their biological activity.Turn by turn: The first total syntheses of the bioactive cyclodepsipeptide ohmyungsamycin A and the proposed structure of ohmyungsamycin B are based on the concise preparation of a linear cyclization precursor followed by macrocyclization. In addition, the proposed structure of ohmyungsamycin B was revised, and the correct position of the additional methyl group was elucidated.
      PubDate: 2018-02-21T05:53:03.851717-05:
      DOI: 10.1002/anie.201711286
       
  • Copper-Catalyzed Highly Stereoselective Trifluoromethylation and
           Difluoroalkylation of Secondary Propargyl Sulfonates
    • Authors: Xing Gao; Yu-Lan Xiao, Xiaolong Wan, Xingang Zhang
      Abstract: It is challenging to stereoselectively introduce a trifluoromethyl group (CF3) into organic molecules. To date, only limited strategies involving direct asymmetric trifluoromethylation have been reported. Herein, we describe a new strategy for direct asymmetric trifluoromethylation through the copper-catalyzed stereospecific trifluoromethylation of optically active secondary propargyl sulfonates. The reaction enables propargylic trifluoromethylation with high regioselectivity and stereoselectivity. The reaction could also be extended to stereospecific propargylic difluoroalkylation. Transformations of the resulting enantiomerically enriched fluoroalkylated alkynes led to a variety of chiral fluoroalkylated compounds, thus providing a useful protocol for applications in the synthesis of fluorinated complexes.Just the beginning: The title reaction enables propargylic trifluoromethylation and difluoroalkylation with high regioselectivity and stereoselectivity (see scheme) to provide versatile building blocks that undergo a wide variety of transformations. Inversion of configuration was observed for the copper-catalyzed process, thus demonstrating that SN2-type oxidative addition of copper to the secondary propargyl sulfonate may be involved in the reaction.
      PubDate: 2018-02-21T05:52:45.316115-05:
      DOI: 10.1002/anie.201711463
       
  • Supramolecular Nested Microbeads as Building Blocks for Macroscopic
           Self-Healing Scaffolds
    • Authors: Ziyi Yu; Ji Liu, Cindy Soo Yun Tan, Oren A. Scherman, Chris Abell
      Abstract: The ability to construct self-healing scaffolds that are injectable and capable of forming a designed morphology offers the possibility to engineer sustainable materials. Herein, we introduce supramolecular nested microbeads that can be used as building blocks to construct macroscopic self-healing scaffolds. The core–shell microbeads remain in an “inert” state owing to the isolation of a pair of complementary polymers in a form that can be stored as an aqueous suspension. An annealing process after injection effectively induces the re-construction of the microbead units, leading to supramolecular gelation in a preconfigured shape. The resulting macroscopic scaffold is dynamically stable, displaying self-recovery in a self-healing electronic conductor. This strategy of using the supramolecular assembled nested microbeads as building blocks represents an alternative to injectable hydrogel systems, and shows promise in the field of structural biomaterials and flexible electronics.Self-healable scaffolds: Supramolecular nested microbeads that are capable of isolating a pair of complementary polymers were developed for the construction of macroscopic self-healing scaffolds. This protocol promotes the polymer flowability for injection while retaining self-healing behaviour on account of the dynamic molecular interactions.
      PubDate: 2018-02-21T05:52:28.189113-05:
      DOI: 10.1002/anie.201711522
       
  • Metal-Free and Alkali-Metal-Catalyzed Synthesis of Isoureas from Alcohols
           and Carbodiimides
    • Authors: Arnaud Imberdis; Guillaume Lefèvre, Pierre Thuéry, Thibault Cantat
      Abstract: The first addition of alcohols to carbodiimides catalyzed by transition-metal-free compounds employs 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) and its alkali metal salts. Isoureas are obtained in short reaction times and high yields when TBDK is used as the catalyst. Control of the coordination sphere of potassium with exogenous chelating ligands, in combination with mechanistic DFT calculations, demonstrated the role and positive influence of the alkali-metal cation on the kinetics.The addition of alcohols to carbodiimides is catalyzed by transition-metal-free compounds such as 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) and its alkali-metal salts. Isoureas are obtained in short reaction times and high yields when TBDK is used as the catalyst.
      PubDate: 2018-02-21T05:52:09.174529-05:
      DOI: 10.1002/anie.201711737
       
  • Catalytic CO Oxidation by O2 Mediated by Noble-Metal-Free Cluster Anions
           Cu2VO3–5−
    • Authors: Li-Na Wang; Xiao-Na Li, Li-Xue Jiang, Bin Yang, Qing-Yu Liu, Hong-Guang Xu, Wei-Jun Zheng, Sheng-Gui He
      Abstract: Catalytic CO oxidation by molecular O2 is an important model reaction in both the condensed phase and gas-phase studies. Available gas-phase studies indicate that noble metal is indispensable in catalytic CO oxidation by O2 under thermal collision conditions. Herein, we identified the first example of noble-metal-free heteronuclear oxide cluster catalysts, the copper–vanadium bimetallic oxide clusters Cu2VO3–5− for CO oxidation by O2. The reactions were characterized by mass spectrometry, photoelectron spectroscopy, and density functional calculations. The dynamic nature of the Cu−Cu unit in terms of the electron storage and release is the driving force to promote CO oxidation and O2 activation during the catalysis.Noble-metal-free heteronuclear oxide cluster catalysts, the copper–vanadium bimetallic oxide clusters Cu2VO3–5− for CO oxidation by O2, have been experimentally identified. The catalysis is driven by the electron cycling on the Cu−Cu unit in Cu2VO3–5− clusters.
      PubDate: 2018-02-21T05:52:03.67941-05:0
      DOI: 10.1002/anie.201712129
       
  • Direct Observation of an Imidoylnitrene: Photochemical Formation of
           PhC(=NMe)−N and Me−N from 1-Methyl-5-phenyltetrazole
    • Authors: Manabu Abe; Didier Bégué, Hugo Santos-Silva, Alain Dargelos, Curt Wentrup
      Abstract: The imidoylnitrene 8, N-methyl-C-phenylimidoylnitrene, has been generated by laser photolysis of 1-methyl-5-phenyltetrazole 6 at 5 K and characterized by its ESR spectrum ( D/hc =0.9602, E/hc =0.0144 cm−1). In addition, the triplet excited states of 6 and of 2-methyl-5-phenyltetrazole 11 were also observed by ESR spectroscopy in the 5 K matrices (6: D/hc =0.123 cm−1, E/hc=0.0065 cm−1, 11: D/hc =0.126 cm−1, E/hc =0.0056 cm−1). The imidoylnitrene 8 is unstable both thermally (disappearing at 80 K) and photochemically (disappearing on continued irradiation at 266 nm). Methyl(phenyl)carbodiimide is the end product of photolysis.Trapped in the cold: N-methyl-C-phenylimidoylnitrene (3) has been generated together with methylnitrene (1) and characterized in its triplet ground state by ESR spectroscopy at 5 K ( D/hc =0.9602, E/hc =0.0144 cm−1). Furthermore, the ESR spectra of the triplet excited states of its precursor, 1-methyl-5-phenyltetrazole (2) as well as 2-methyl-5-phenyltetrazole, were also observed.
      PubDate: 2018-02-21T05:51:58.276227-05:
      DOI: 10.1002/anie.201712689
       
  • Dicationic E4 Chains (E=P, As, Sb, Bi) Embedded in the Coordination Sphere
           of Transition Metals
    • Authors: Luis Dütsch; Martin Fleischmann, Stefan Welsch, Gábor Balázs, Werner Kremer, Manfred Scheer
      Abstract: The oxidation chemistry of the complexes [{CpMo(CO)2}2(μ,η2:η2-E2)] (E=P (A), As (B), Sb (C), Bi (D)) is compared. The oxidation of A–D with [Thia]+ (=[C12H8S2]+) results in the selective formation of the dicationic E4 complexes [{CpMo(CO)2}4(μ4,η2:η2:η2:η2-E4)]2+ (E=P (1), As (2), Sb (3), Bi (4)), stabilized by four [CpMo(CO)2] fragments. The formation of the corresponding monocations [A]+, [C]+, and [D]+ could not be detected by cyclic voltammetry, EPR, or NMR spectroscopy. This finding suggests that dimerization is fast and that there is no dissociation in solution, which was also predicted by DFT calculations. However, EPR measurements of 2 confirmed the presence of small amounts of the radical cation [B]+ in solution. Single-crystal X-ray diffraction revealed that the products 1 and 2 feature a zigzag E4 chain in the solid state while 3 and 4 bear a central E4 cage with a distorted “butterfly-like” geometry. Additionally, 1 can be easily and reversibly converted into a symmetric and an unsymmetric form.Unprecedented dicationic E4 chains and cages (E=pnictogen) are obtained by the oxidation of [{CpMo(CO)2}2(μ,η2:η2-E2)] complexes through E−E bond formation. The dicationic cores are free of organic substituents and are stabilized in the coordination sphere of molybdenum atoms.
      PubDate: 2018-02-21T05:51:49.90653-05:0
      DOI: 10.1002/anie.201712884
       
  • An Intracellular H2O2-Responsive AIEgen for the Peroxidase-Mediated
           Selective Imaging and Inhibition of Inflammatory Cells
    • Authors: Yong Cheng; Jun Dai, Chunli Sun, Rui Liu, Tianyou Zhai, Xiaoding Lou, Fan Xia
      Abstract: Inflammatory cells have gained widespread attention because inflammatory diseases increase the risk for many types of cancer. Therefore, it is urgent and important to implement detection and treatment methods for inflammatory cells. Herein, we constructed a theranostic probe with aggregation-induced emission (AIE) characteristics, in which tetraphenylethene (TPE) was modified with two tyrosine (Tyr) moieties. Owing to the H2O2-dependent, enzyme-catalyzed dityrosine formation, Tyr-containing TPE (TT) molecules crosslink through dityrosine linkages to induce the formation of hydrophobic aggregates, activating the AIE process in inflammatory cells that contain H2O2 and overexpress myeloperoxidase. The emission turn-on resulting from the crosslinking of TT molecules could be used to distinguish between inflammatory and normal cells. Moreover, the massive TT aggregates induced mitochondria damage and cell apoptosis. This study demonstrates that the H2O2-responsive peroxidase-activated AIEgen holds great promise for inflammatory-cell selective imaging and inhibition.Aggregate therapy: An intracellular H2O2-responsive and peroxidase-mediated therapeutic strategy with AIEgens has been developed. The method described provides a theranostic tool for inflammatory-cell selective imaging and inhibition to achieve the precise detection and treatment.
      PubDate: 2018-02-21T05:51:40.422103-05:
      DOI: 10.1002/anie.201712803
       
  • Nitrogen-Based Lewis Acids: Synthesis and Reactivity of a Cyclic
           (Alkyl)(Amino)Nitrenium Cation
    • Authors: Jiliang Zhou; Liu Leo Liu, Levy L. Cao, Douglas W. Stephan
      Abstract: A room-temperature-stable crystalline cyclic (alkyl)(amino)nitrenium cation 2 features cationic nitrogen atom with a smaller HOMO–LUMO gap compared to that of a 1,2,3-triazolium 5 (an N-heterocyclic nitrenium cation). The low-lying LUMO of 2 results in an enhanced electrophilicity, which allowed for the formation of Lewis adducts with neutral Lewis bases, such as Me3P, nBu3P, and IiPr. The N-based Lewis acid 2 also forms an FLP with tBu3P but subsequently reacts with (PrS)2 to cleave the S−S bond. Both experimental and theoretical results suggest that the Lewis acidity of 2 is stronger than its N3 analogues.The room-temperature-stable crystalline cyclic (alkyl)(amino) nitrenium features a cationic nitrogen atom and exhibits enhanced electrophilicity, yielding Lewis adducts with Me3P, nBu3P, and IiPr and an FLP with tBu3P.
      PubDate: 2018-02-21T05:51:29.604903-05:
      DOI: 10.1002/anie.201713118
       
  • Potassium-Zincate-Catalyzed Benzylic C−H Bond Addition of
           Diarylmethanes to Styrenes
    • Authors: Yu-Feng Liu; Dan-Dan Zhai, Xiang-Yu Zhang, Bing-Tao Guan
      Abstract: Direct functionalization of the benzylic C−H bond of diarylmethanes is an important strategy for the synthesis of diarylmethine-containing compounds. However, the methods developed to date for this purpose require a stoichiometric amount (usually more) of either a strong base or an oxidant. Reported here is the first catalytic benzylic C−H bond addition of diarylmethanes to styrenes and conjugated dienes. A potassium zincate complex, generated from potassium benzyl and zinc amide, acts as a catalyst and displays good activity and chemoselectivity. Considering the atom economy of the reaction and the ready availability of the catalyst, this reaction constitutes a practical, efficient method for diarylalkane synthesis.‘Zinc’ into it: The catalytic addition of the benzylic carbon center of diarylmethanes to styrenes and conjugated dienes was achieved for the first time by using a potassium zincate catalyst. The reaction demonstrates wide scope and high yields.
      PubDate: 2018-02-21T05:51:23.953491-05:
      DOI: 10.1002/anie.201713165
       
  • Contra-Thermodynamic, Photocatalytic EZ Isomerization of Styrenyl Boron
           Species: Vectors to Facilitate Exploration of Two-Dimensional Chemical
           Space
    • Authors: John J. Molloy; Jan B. Metternich, Constantin G. Daniliuc, Allan J. B. Watson, Ryan Gilmour
      Abstract: Designing strategies to access stereodefined olefinic organoboron species is an important synthetic challenge. Despite significant advances, there is a striking paucity of routes to Z-α-substituted styrenyl organoborons. Herein, this strategic imbalance is redressed by exploiting the polarity of the C(sp2)−B bond to activate the neighboring π system, thus enabling a mild, traceless photocatalytic isomerization of readily accessible E-α-substituted styrenyl BPins to generate the corresponding Z-isomers with high fidelity. Preliminary validation of this contra-thermodynamic EZ isomerization is demonstrated in a series of stereoretentive transformations to generate Z-configured trisubstituted alkenes, as well as in a concise synthesis of the anti-tumor agent Combretastatin A4.It's EZ: Exploitation of the polarity of the C(sp2)−B bond to activate the neighboring π system enables a mild, traceless photocatalytic isomerization of readily accessible E-α-substituted styrenyl BPins to generate the corresponding Z-isomers with high fidelity. The method is used for a series of stereoretentive transformations to generate Z-configured trisubstituted alkenes, as well as in a concise synthesis of the anti-tumor agent combretastatin A4.
      PubDate: 2018-02-21T05:51:13.906905-05:
      DOI: 10.1002/anie.201800286
       
  • N-Carboxyanhydride Polymerization of Glycopolypeptides that Activate
           Antigen-Presenting Cells through Dectin-1 and Dectin-2
    • Authors: Matthew N. Zhou; Corleone S. Delaveris, Jessica R. Kramer, Justin A. Kenkel, Edgar G. Engleman, Carolyn R. Bertozzi
      Abstract: The C-type lectins dectin-1 and dectin-2 contribute to innate immunity against microbial pathogens by recognizing their foreign glycan structures. These receptors are promising targets for vaccine development and cancer immunotherapy. However, currently available agonists are heterogeneous glycoconjugates and polysaccharides from natural sources. Herein, we designed and synthesized the first chemically defined ligands for dectin-1 and dectin-2. They comprised glycopolypeptides bearing mono-, di-, and trisaccharides and were built through polymerization of glycosylated N-carboxyanhydrides. Through this approach, we achieved glycopolypeptides with high molecular weights and low dispersities. We identified structures that elicit a pro-inflammatory response through dectin-1 or dectin-2 in antigen-presenting cells. With their native proteinaceous backbones and natural glycosidic linkages, these agonists are attractive for translational applications.Causing a response: The first chemically defined ligands for dectin-1 and dectin-2 were designed and synthesized. These consisted of glycopolypeptides built through the polymerization of glycosylated N-carboxyanhydrides. Structures that elicit a proinflammatory response through dectin-1 or dectin-2 in antigen-presenting cells were identified.
      PubDate: 2018-02-21T05:51:01.88301-05:0
      DOI: 10.1002/anie.201713075
       
  • Highly Efficient Artificial Light-Harvesting Systems Constructed in
           Aqueous Solution Based on Supramolecular Self-Assembly
    • Authors: Shuwen Guo; Yongshang Song, Yuling He, Xiao-Yu Hu, Leyong Wang
      Abstract: Highly efficient light-harvesting systems were successfully fabricated in aqueous solution based on the supramolecular self-assembly of a water-soluble pillar[6]arene (WP6), a salicylaldehyde azine derivative (G), and two different fluorescence dyes, Nile Red (NiR) or Eosin Y (ESY). The WP6-G supramolecular assembly exhibits remarkably improved aggregation-induced emission enhancement and acts as a donor for the artificial light-harvesting system, and NiR or ESY, which are loaded within the WP6-G assembly, act as acceptors. An efficient energy-transfer process takes place from the WP6-G assembly not only to NiR but also to ESY for these two different systems. Furthermore, both of the WP6-G-NiR and WP6-G-ESY systems show an ultrahigh antenna effect at a high donor/acceptor ratio.Light-harvesting systems were fabricated in aqueous solution by supramolecular self-assembly of a water-soluble pillar[6]arene (WP6), a salicylaldehyde azine derivative (G, acting as donor), and two different fluorescence dyes, Nile Red or Eosin Y, which is loaded within the WP6-G assembly, acts as acceptor.
      PubDate: 2018-02-21T05:50:52.941798-05:
      DOI: 10.1002/anie.201800175
       
  • Isolation of an Eleven-Atom Polydentate Carbon-Chain Chelate Obtained by
           Cycloaddition of a Cyclic Osmium Carbyne with an Alkyne
    • Authors: Congqing Zhu; Jun Zhu, Xiaoxi Zhou, Qin Zhu, Yuhui Yang, Ting Bin Wen, Haiping Xia
      Abstract: Carbon ligands have long played an important role in organometallic chemistry. However, previous examples of all-carbon chelating ligands are limited. Herein, we present a novel complex with an eleven-atom carbon chain as a polydentate chelating ligand. This species was formed by the [2+2+2] cycloaddition reaction of two equivalents of an alkyne with an osmapentalyne that contains the smallest carbyne bond angle (127.9°) ever observed. Density functional calculations revealed that electron-donating groups play a key role in the stabilization of this polydentate carbon-chain chelate. This process is also the first [2+2+2] cycloaddition reaction of an alkyne with a late-transition-metal carbyne complex. This study not only enriches the chemistry of polydentate carbon-chain chelates, but also deepens our understanding of the chelating ability of carbon ligands.Polydentate carbon ligands: The first organometallic compound with an eleven-atom carbon chain as a polydentate chelating ligand was obtained by [2+2+2] cycloaddition of an alkyne with a late-transition-metal carbyne complex, and provides further insight into the coordinating ability of carbon ligands.
      PubDate: 2018-02-21T05:50:44.266914-05:
      DOI: 10.1002/anie.201713391
       
  • Highly Stable Lithium Metal Batteries Enabled by Regulating the Li+
           Solvation in Nonaqueous Electrolyte
    • Authors: Xue-Qiang Zhang; Xiang Chen, Xin-Bing Cheng, Bo-Quan Li, Xin Shen, Chong Yan, Jia-Qi Huang, Qiang Zhang
      Abstract: Safe and rechargeable lithium (Li) metal batteries have been hindered by the uncontrollable Li dendrites, where nonaqueous electrolyte always plays a significant role in practical batteries. Herein an emerging electrolyte based on a simple solvation strategy was proposed for highly stable Li metal anodes in both coin and pouch cells. Fluoroethylene carbonate (FEC) and lithium nitrate (LiNO3) were concurrently introduced into electrolyte, altering the solvation sheath of Li ions and then forming uniform solid electrolyte interphase (SEI) with abundant LiF and LiNxOy on a working Li metal anode that contributes to dendrite-free Li deposition. Ultrahigh Coulombic efficiency (99.96%) and long lifespans (1000 cycles) were achieved when FEC/LiNO3 electrolyte was applied in working batteries. The solvation chemistry of electrolyte was further explored by molecular dynamics simulations and first-principles calculations. This work provides a fruitful insight on understanding the critical role of the solvation of Li ions in forming SEI and delivers an effective route to optimize electrolytes for safe Li metal batteries.
      PubDate: 2018-02-21T05:20:44.352259-05:
      DOI: 10.1002/anie.201801513
       
  • Site-Specific Studies of Nucleosome Interactions by Solid-State NMR
    • Authors: ShengQi Xiang; Ulric B. le Paige, Velten Horn, Klaartje Houben, Marc Baldus, Hugo van Ingen
      Abstract: Chromatin function depends on a dense network of interactions between nucleosomes and wide range of proteins. A detailed description of these protein-nucleosome interactions is required to reach a full molecular understanding of chromatin function in both genetics and epigenetics. Here, we show that the structure, dynamics and interactions of nucleosomes can be interrogated in a residue-specific manner using state-of-the-art solid-state NMR. Using sedimented nucleosomes, high-resolution spectra are obtained for both flexible histone tails and the non-mobile histone core. Through co-sedimentation of a nucleosome-binding peptide, we demonstrate that protein binding sites on the nucleosome surface can be determined. We believe that this approach holds great promise as it is generally applicable, extendable to include the structure and dynamics of the bound proteins, and scalable to interactions of proteins with higher-order chromatin structures, including isolated or cellular chromatin.
      PubDate: 2018-02-21T05:20:40.39264-05:0
      DOI: 10.1002/anie.201713158
       
  • Bioorthogonal Catalytic Activation of Platinum and Ruthenium Anticancer
           Complexes by FAD and Flavoproteins
    • Authors: Silvia Alonso-de Castro; Aitziber L. Cortajarena, Fernando López-Gallego, Luca Salassa
      Abstract: Flavins and flavoproteins have been employed as photocatalysts for the activation of metal-based prodrugs. In their Communication (
      DOI : 10.1002/anie.201800288), F. López-Gallego, L. Salassa, and co-workers show how these photocatalysts convert PtIV and RuII complexes into potentially toxic PtII or RuII−OH2 species in the presence of electron donors and low doses of blue light. The flavoproteins miniSOG and NADH oxidase catalytically activate PtIV prodrugs with bioorthogonal selectivity. Unconventionally, metal complexes act as substrates in these reactions.
      PubDate: 2018-02-21T05:10:20.269829-05:
       
  • Silica-Supported Pentamethylcyclopentadienyl Cyclopentadienyl
           Ytterbium(II) and Samarium(II) Sites: Ultrahigh Molecular Weight
           Polyethylene without Co-Catalyst
    • Authors: Florian Allouche; Ka Wing Chan, Alexey Fedorov, Richard A. Andersen, Christophe Copéret
      Abstract: Designing highly active supported ethylene polymerization catalysts that do not require a co-catalyst to generate electrophilic metal alkyl species is still a challenge despite its industrial relevance. Described herein is the synthesis and characterization of well-defined silica-supported cyclopentadienyl LnII sites (Ln=Yb and Sm) of general formula [(≡SiO)LnCp*]. These well-defined surface species are highly activite towards ethylene polymerization in the absence of added co-catalyst. Initiation is proposed to occur by single electron transfer.Ready, SET, Go: Well-defined silica-supported lanthanocene(II) [(≡SiO)LnCp*] (Ln=Yb, Sm) were synthesized and fully characterized by extended X-ray absorption fine structure, infrared spectroscopy, solid-state NMR spectroscopy, and elemental analysis. These catalysts demonstrated very high activity for ethylene polymerization, the initiation of which is postulated to occur through a single electron transfer.
      PubDate: 2018-02-21T04:50:32.213248-05:
      DOI: 10.1002/anie.201800542
       
  • Revealing active species for aerobic alcohol oxidation using
           stoichiometrically uniform supported Pd catalysts
    • Authors: Dingsheng Wang; Pingyu Xin, Jia Li, Yu Xiong, Xi Wu, Juncai Dong, Wenxing Chen, Yu Wang, Lin Gu, Jun Luo, Hongpan Rong, Chen Chen, Qing Peng, Yadong Li
      Abstract: Supported metal catalysts are one of the foundations of modern chemical industry. The active species in such catalysts are always elusive to identify, and in the meanwhile large quantities of inert species can cause significant waste. Herein, using a stoichiometrically precise synthetic method, we prepare atomically dispersed palladium-cerium oxide (Pd1/CeO2) and hexapalladium cluster-cerium oxide (Pd6/CeO2), as confirmed by spherical-aberration-corrected transmission electron microscopy and X-ray absorption fine structure spectroscopy. We discover that, for aerobic alcohol oxidation, Pd1/CeO2 shows extremely high catalytic activity with a TOF of 6739 h-1 and satisfactory selectivity (almost 100% for benzaldehyde), while Pd6/CeO2 is inactive, indicating that the true active species are single Pd atoms. Theoretical simulations reveal that the bulkier Pd6 clusters hinder the interactions between hydroxyl groups and the CeO2 surface, thus suppressing synergy of Pd-Ce perimeter. This work provides a new way to maximize material utilization and reduce waste in supported metal catalysts.
      PubDate: 2018-02-21T04:23:54.043892-05:
      DOI: 10.1002/anie.201801103
       
  • Cobalt-Bridged Ionic Liquid Polymer on a Carbon Nanotube for Enhanced
           Oxygen Evolution Reaction Activity
    • Authors: Yuxiao Ding; Alexander Klyushin, Xing Huang, Travis Jones, Detre Teschner, Frank Girgsdies, Tania Rodenas, Robert Schlögl, Saskia Heumann
      Abstract: By taking inspiration from the catalytic properties of single-site catalysts and the enhancement of performance through ionic liquids on metal catalysts, we exploited a scalable way to place single cobalt ions on a carbon-nanotube surface bridged by polymerized ionic liquid. Single dispersed cobalt ions coordinated by ionic liquid are used as heterogeneous catalysts for the oxygen evolution reaction (OER). Performance data reveals high activity and stable operation without chemical instability.Co-operating: A scalable method was developed to get single cobalt ions on CNT surface with polymerized ionic liquid. The polymerized ionic liquid can adjust the electron structure of the atomically dispersed Co which is favorable for the oxygen evolution reaction. The tangled polymerized ionic liquid, as counter ion, make the Co ion stable on CNT surface.
      PubDate: 2018-02-21T03:25:39.774479-05:
      DOI: 10.1002/anie.201711688
       
  • Broadening the Scope for Fluoride-Free Synthesis of Siliceous Zeolites
    • Authors: Vivek Vattipalli; Abdul Mughis Paracha, Weiguo Hu, Huiyong Chen, Wei Fan
      Abstract: Siliceous zeolites are ideally suited for emerging applications in gas separations, sensors, and the next generation of low-k dielectric materials, but the use of fluoride in the synthesis significantly hinders their commercialization. Herein, we show that the dry gel conversion (DGC) technique can overcome this problem. Fluoride-free synthesis of two siliceous zeolites—AMH-4 (CHA-type) and AMH-5 (STT-type), has been achieved for the first time using the method. Siliceous *BEA-, MFI-, and *MRE-type zeolites have also been synthesized to obtain insights into the crystallization process. Charge-balancing interactions between the inorganic cation, organic structure-directing agent (OSDA), and Si−O− defects are found to be an essential aspect. We quantify this factor in terms of the “OSDA charge/silica ratio” of the as-made zeolites and demonstrate that the DGC technique is broadly applicable and opens up new avenues for fluoride-free siliceous zeolite synthesis.No F required: Fluoride-free synthesis of siliceous zeolites remains highly challenging—of the 234 recognized zeolite framework structures, less than 25 have been made in purely siliceous form without using fluoride. The dry gel conversion technique has been used to synthesize two new fluoride-free siliceous zeolites. Systematic studies and analysis reveal mechanistic insights into fluoride-free siliceous zeolite synthesis.
      PubDate: 2018-02-21T03:20:31.483111-05:
      DOI: 10.1002/anie.201712684
       
  • Super-chelators for advanced protein labeling in living cells
    • Authors: Karl Gatterdam; Eike F. Joest, Marina S. Dietz, Mike Heilemann, Robert Tampé
      Abstract: Live-cell labeling, super-resolution microscopy, single-molecule applications, protein localization or chemically induced assembly are emerging approaches, which require specific and very small interaction pairs. The minimal disturbance of protein function is essential to derive unbiased insights into cellular processes. Here, we define a new class of hexavalent N-nitrilotriacetic acid (hexaNTA) chelators, displaying the highest affinity and stability of all NTA-based small interaction pairs described so far. Coupled to bright organic fluorophores with fine-tuned photo-physical properties, these super-chelator probes were delivered into human cells by chemically gated nanopores. These super-chelators permit kinetic profiling, multiplexed labeling of His6 and His12-tagged proteins as well as single-molecule based super-resolution imaging.
      PubDate: 2018-02-20T21:50:51.877753-05:
      DOI: 10.1002/anie.201800827
       
  • Odorant receptor 7D4 activation dynamics
    • Authors: Jerome Golebiowski; claire de march, jeremie topin, hiroaki matsunami, gleb novikov, kentaro ikegami, elise bruguera
      Abstract: Deciphering how an odorant activates an odorant receptor (OR) and how changes in specific OR residues affect its responsiveness are central to understanding how we smell. A joint approach combining site-directed mutagenesis and functional assays with computational modeling has been used to explore the signaling mechanics of OR7D4. In this OR, a genetic polymorphism affects our perception of androstenone. A total of 0.12 ms molecular simulations predicted that, similarly to observations from other G protein-coupled receptors with known experimental structures, an activation pathway connects the ligand and G protein binding site. The 3D model activation mechanism correlates with in vitro data and notably predicts that the OR7D4 WM variant does not activate. Upon activation, an OR-specific sequence motif is the convergence point of the mechanism. Our study suggests that robust homology modeling can serve as a powerful tool to capture OR dynamics related to smell perception.
      PubDate: 2018-02-20T13:50:31.425095-05:
      DOI: 10.1002/anie.201713065
       
  • O2 sensitivity of [Fe]-hydrogenase in the Presence of Reducing Substrates
    • Authors: Gangfeng Huang; Tristan Wagner, Ulrich Ermler, Eckhard Bill, Kenichi Ataka, Seigo Shima
      Abstract: [Fe]-hydrogenase reversibly catalyzes the transfer of a hydride ion from H2 to methenyl-tetrahydromethanopterin (methenyl-H4MPT+) to form methylene-H4MPT. Its iron-guanylylpyridinol (FeGP) cofactor plays a key role in H2 activation. Here, we show that [Fe]-hydrogenase becomes O2-sensitive under turnover conditions in the presence of the reducing-substrates, methylene-H4MPT or methenyl-H4MPT+/H2. Only then, H2O2 is generated and decomposes the FeGP cofactor as demonstrated by spectroscopic analyses and the crystal structure of the inactivated enzyme. O2 reduction to H2O2 requires a reductant, which can be a catalytic intermediate transiently formed during the [Fe]-hydrogenase reaction. The most probable candidate is an iron-hydride species; its presence has already been predicted by theoretical studies of the catalytic reaction. Our finding supported the prediction because the same type of reduction reaction is described for ruthenium hydride complexes that hydrogenate polar compounds.
      PubDate: 2018-02-20T12:50:57.365268-05:
      DOI: 10.1002/anie.201712293
       
  • Customizing the Electrochemical Properties of Carbon Nanodots with
           Quinones in Bottom-Up Syntheses
    • Authors: Maurizio Prato; Francesco Rigodanza, Francesca Arcudi, Luka Dordevich
      Abstract: We show how the redox potentials of Carbon Nanodots (CNDs) can be modulated by employing quinones as electroactive precursors during the microwave-assisted synthetic step. We prepared and characterized a redox library of CNDs, demonstrating that this approach can promote the use of carbon nanodots for ad-hoc applications, including photocatalysis.
      PubDate: 2018-02-20T12:50:53.97888-05:0
      DOI: 10.1002/anie.201801707
       
  • Chiral 1,3,2-Diazaphospholenes as Catalytic Molecular Hydrides for
           Enantioselective Conjugate Reductions
    • Authors: Nicolai Cramer; Solène Miaskiewicz, John H. Reed, Pavel A. Donets, Caio C. Oliveira
      Abstract: Secondary 1,3,2-diazaphospholenes have a polarized P‒H bond and are emerging as molecular hydrides. A class of chiral conformationally restricted methoxy-1,3,2-diazaphospholene catalysts is reported. We demonstrate their catalytic potential in enantioselective 1,4-reduction of α,β-unsaturated carbonyl derivatives comprising enones, acyl pyrroles and amides in enantioselectivities of up to 95.5:4.5 er.
      PubDate: 2018-02-20T11:50:43.374745-05:
      DOI: 10.1002/anie.201801300
       
  • Enzymatic or in vivo installation of propargyl groups in combination with
           click chemistry enables enrichment and detection of methyltransferase
           target sites in RNA
    • Authors: Katja Hartstock; Benedikt Nilges, Anna Ovcharenko, Nicolas Cornelissen, Nikolai Puellen, Sebastian Leidel, Andrea Rentmeister
      Abstract: m6A is the most abundant internal modification in eukaryotic mRNA. It is introduced by METTL3-METTL14 and tunes mRNA metabolism, impacting cell differentiation and development. Precise transcriptome-wide assignment of m6A sites is of utmost importance. However, m6A does not interfere with Watson-Crick base pairing making polymerase-based detection challenging. We developed a chemical-biology approach for the precise mapping of methyltransferase (MTase) target sites based on the introduction of a bioorthogonal propargyl group in vitro and in cells. We show that propargyl can be introduced enzymatically by wild-type METTL3-METTL14. Reverse transcription terminated up to 65 % at m6A sites after bioconjugation and purification, hence enabling detection of METTL3-METTL14 target sites by next generation sequencing. Importantly, we implemented metabolic propargyl labeling of RNA MTase target sites in vivo based on propargyl-L-selenohomocysteine and validated different types of known rRNA methylation sites.
      PubDate: 2018-02-20T11:50:28.775841-05:
      DOI: 10.1002/anie.201800188
       
  • Unprecedented Dearomatized Spirocyclopropane in a Sequential
           Rh(III)-catalyzed C-H Activation and Rearrangement Reaction
    • Authors: Xiaoming Wang; Yingzi Li, Tobias Knecht, Constantin Daniliuc, Ken Houk, Frank Glorius
      Abstract: An unprecedented dearomatized spirocyclopropane intermediate was discovered in a sequential Cp*Rh(III)-catalyzed C-H activation and Wagner-Meerwein-type rearrangement reaction. How the oxidative O-N bond is cleaved and the role of HOAc were uncovered in this study. Furthermore, a Cp*Rh(III)-catalyzed dearomatization reaction of N-(naphthalen-1-yloxy)acetamide with strained olefins was developed, affording a variety of spirocyclopropanes.
      PubDate: 2018-02-20T10:50:26.682028-05:
      DOI: 10.1002/anie.201800803
       
  • One-Pot Tandem Photoredox and Cross-Coupling Catalysis with a Single
           Pd-Carbodicarbene Complex
    • Authors: Tiow-Gan Ong; Yu-Chen Hsu, Vincent C.-C. Wang, Ka-Chun Au-Yeung, Chung-Yu Tsai, Chun-Chi Chang, Bo-Chao Lin, Yi-Tsu Chan, Chao-Ping Hsu, Glenn P. A. Yap, Titel Jurca
      Abstract: The combination of conventional transition metal-catalyzed coupling (2e- process) and photoredox catalysis (1e- process) has emerged as a powerful approach to catalyze difficult cross-coupling reactions under mild conditions. We report a Pd-carbodicarbene (CDC) complex that mediates both Suzuki-Miyaura coupling and photoredox catalysis for C-N bond formation upon visible-light irradiation. These two catalytic pathways can be further merged to promote both conventional transition-metal-catalyzed coupling and photoredox catalysis to mediate C-H arylation under ambient conditions with a single component catalyst in an efficient one-pot process.
      PubDate: 2018-02-20T10:20:59.78983-05:0
      DOI: 10.1002/anie.201800951
       
  • Lewis Acid Catalyzed Enantioselective Desymmetrization of Donor-Acceptor
           Meso-Diaminocyclopropanes
    • Authors: Daniele Perrotta; Ming-Ming Wang, Jerome Waser
      Abstract: The first example of Lewis acid catalyzed enantioselective ring-opening desymmetrization of donor-acceptor meso-diaminocyclopropanes is reported herein. A copper(II)-catalyzed Friedel-Crafts alkylation of indoles and a pyrrole with an unprecedented meso-diaminocyclopropane delivered enantioenriched diastereomerically pure urea products, which are structurally related to natural and synthetic bioactive compounds. The development of a new ligand through the investigation of an underexplored subclass of BOX ligands was essential for obtaining high enantiomeric ratios.
      PubDate: 2018-02-20T10:20:47.339367-05:
      DOI: 10.1002/anie.201800494
       
  • Direct formation of C-C triple bonded structural motifs by on-surface
           dehalogenative homocoupling of tribromomethyl molecules
    • Authors: Qiang Sun; Xin Yu, Meiling Bao, Mengxi Liu, Jinliang Pan, Zeqi Zha, Liangliang Cai, Honghong Ma, Chunxue Yuan, Xiaohui Qiu, Wei Xu
      Abstract: On-surface synthesis shows significant potential in constructing novel nanostructures/nanomaterials, which has been intensely studied over the recent years. The formation of acetylenic scaffoldings provides an important route to the fabrication of emerging carbon nanostructures including carbyne, graphyne and graphdiyne, which involve the chemically vulnerable sp-hybridized carbons. Herein, we designed and synthesized a tribromomethyl group, by using the combination of high-resolution scanning tunneling microscopy and non-contact atomic force microscopy imaging and density functional theory calculations, we demonstrated that it is feasible to achieve the direct formation of C-C triple bonded structural motifs via on-surface dehalogenative homocoupling reactions. Correspondingly, we are able to convert the sp3 hybridized state to sp hybridized state of carbon atoms, i.e., from an alkyl group to an alkynyl one. Moreover, we successfully achieved the formation of dimer structures, one-dimensionalmolecular wires and two-dimensional molecular networks on Au(111) surface,which would inspire further studies towards the two-dimensional graphyne structures.
      PubDate: 2018-02-20T05:21:08.24076-05:0
      DOI: 10.1002/anie.201801056
       
  • Iron-Catalyzed Cross-Coupling in the Synthesis of Pharmaceuticals: In
           Pursuit of Sustainability
    • Authors: Aleksandra Piontek; Elwira Bisz, Michal Szostak
      Abstract: The scarcity of precious metals has given raise to the development of sustainable strategies for metal-catalyzed cross-coupling reactions. The establishment of new catalytic methods using iron is attractive due to low cost, abundance, ready availability and very low toxicity of iron. In the last few years sustainable methods for iron-catalyzed cross-couplings have entered the critical area of pharmaceutical research. Most notably, iron is one of the very few metals that have been successfully field tested as highly effective base-metal catalysts in practical, kilogram-scale industrial cross-couplings, thus validating the potential and promise of iron-catalysis to address the challenge of sustainability for chemical synthesis. In this minireview, we critically discuss the strategic benefits of using iron catalysis as a green and sustainable alternative to precious metals in cross-coupling applications for the synthesis of pharmaceuticals. The minireview provides an essential introduction to the fundamental aspect of practical iron catalysis, highlights areas for improvement and identifies new fields to explore.
      PubDate: 2018-02-19T22:51:14.81763-05:0
      DOI: 10.1002/anie.201800364
       
  • NiH-Catalyzed Reductive Relay Hydroalkylation: A Strategy for Remote sp3
           C-H Alkylation of Alkenes
    • Authors: Fang Zhou; Jin Zhu, Yao Zhang, Shaolin Zhu
      Abstract: The terminal-selective, remote sp3 C-H alkylation of alkenes was achieved by a NiH-catalyzed reductive, chainwalking and sequential alkylation relay process. This method allows the construction of unfunctionalized C(sp3)-C(sp3) bonds, under mild conditions from two simple feedstock chemicals, olefins and alkyl halides. The practical value of this transformation is further demonstrated by the large-scale and regioconvergent alkylation of isomeric mixtures of olefins with low catalyst loading.
      PubDate: 2018-02-19T22:51:08.061295-05:
      DOI: 10.1002/anie.201712731
       
  • Phosphoric Acid Catalyzed Asymmetric [2+2]
           Cyclization/Penicillin-penillonic Acid Rearrangement
    • Authors: Ming Zhang; Changjun Yu, Junqiu Xie, Xudong Xun, Wangsheng Sun, Liang Hong, Rui Wang
      Abstract: The first example of asymmetric penicillin-penillonic acid (PPA) rearrangement was reported that is based on the first [2+2] cyclization followed by acid-catalyzed asymmetric rearrangement. In the presence of a phosphoric acid catalyst, the reaction of azlactones with β-carbolines generates α-amino-β-lactams, which undergo PPA rearrangement with high selectivities. This process represents the first [2+2] cyclization of azlactones with imines and the first PPA rearrangement, which are linked together by the phosphoric acid catalyst.
      PubDate: 2018-02-19T21:51:13.474824-05:
      DOI: 10.1002/anie.201712571
       
  • Atomically dispersed metal sites in MOF-based materials for
           electrocatalytic and photocatalytic energy conversion
    • Authors: Zibin Liang; Chong Qu, Dingguo Xia, Ruqiang Zou, Qiang Xu
      Abstract: Metal sites play an essential role for both electrocatalytic and photocatalytic energy conversion applications. The highly ordered arrangements of the organic linkers and metal nodes and the well-defined pore structures of metal-organic frameworks (MOFs) make them ideal substrates to support atomically dispersed metal sites (ADMSs) located in their metal nodes, linkers, and pores. Besides, porous carbon materials doped with ADMSs can be derived from these ADMS-incorporated MOF precursors through controlled treatments. These ADMSs incorporated in pristine MOFs and MOF-derived carbon materials possess unique merits over the molecular or the bulk metal-based catalysts, bridging the gap between homogeneous and heterogeneous catalysts for energy conversion applications. In this review, recent progress and perspective of design and incorporation of ADMSs in pristine MOFs and MOF-derived materials for energy conversion applications are highlighted, which will hopefully promote further developments of advanced MOF-based catalysts in foreseeable future.
      PubDate: 2018-02-19T21:51:01.859246-05:
      DOI: 10.1002/anie.201800269
       
  • Counting the Clicks in Fluorescent Polymer Networks
    • Authors: Diego Estupiñán; Christopher Barner-Kowollik, Leonie Barner
      Abstract: We introduce a fluorescence-based methodology enabling the quantification of ligation points in photochemically prepared polymer networks, addressing the vexed question of quantifying the number of linkages within networks. Well-defined α,ω-tetrazole-capped polymer strands prepared via RAFT polymerization are crosslinked under UV irradiation by a trimaleimide via nitrile imine-mediated tetrazole-ene cycloaddition. Thus, for each linkage point a fluorescent pyrazoline ring is formed, resulting fluorescent networks, which are degradable by aminolysis of the trithiocarbonate functionalities, resulting in soluble fragments. The fluorescence emission of the soluble network fragments correlates directly with the number of pyrazoline moieties originally present in the network, thus providing a direct measure of the elusive number of ligation points constituting the network. The herein introduced strategy based on a fluorescence readout is a powerful yet simple approach to quantify network formation processes applicable to a wide class of polymers accessible via RAFT.
      PubDate: 2018-02-19T21:50:56.585054-05:
      DOI: 10.1002/anie.201713388
       
  • Visible-Light Photocatalysis: Does it make a difference in Organic
           Synthesis'
    • Authors: Leyre Marzo; Santhosh K. Pagire, Oliver Reiser, Burkhard König
      Abstract: Visible light photocatalysis has evolved over the last decade into a widely used method in organic synthesis. For many important transformations, such as cross-coupling reactions, alpha-amino functionalizations, cycloadditions, ATRA reactions, or fluorinations, photocatalytic variants have been reported. In this review, we try to compare classical and photocatalytic procedures for selected classes of reactions and highlight their advantages and limitations. In many cases, the photocatalytic reactions proceed at milder reaction conditions, typically at room temperature, and stoichiometric reagents are replaced by simple oxidants or reductants, like air oxygen or amines. This way, besides providing alternative protocols for established transformations that allow a broadening of the substrate scope, also new transformations become possible, especially by merging photocatalysis with organo- or metal catalysis. Does visible light photocatalysis make a difference in organic synthesis' The prospect to shuttle electrons back and forth to substrates and intermediates or to selectively transfer energy through a visible light absorbing photocatalyst holds the promise to improve current protocols in radical chemistry and to open up new avenues by accessing reactive species hitherto unknown.
      PubDate: 2018-02-19T14:50:34.198636-05:
      DOI: 10.1002/anie.201709766
       
  • A Stable Metal-Organic Framework Featuring Local Buffer Environment for
           Carbon Dioxide Fixation
    • Authors: Hongming He; Qi Sun, Wenyang Gao, Jason A. Perman, Fuxing Sun, Guangshan Zhu, Briana Aguila, Katherine Forrest, Brian Space, Shengqian Ma
      Abstract: A majority of metal-organic frameworks (MOFs) fail to preserve their physical and chemical properties after exposure to acidic, neutral, or alkaline aqueous solutions, therefore limiting their practical applications in many areas. The strategy demonstrated herein is the design and synthesis of an organic ligand that behaves as a buffer to drastically boost the aqueous stability of a porous MOF (JUC-1000), which maintains its structural integrity at low and high pH values. The local buffer environment resulting from the weak acid-base pairs of the custom-designed organic ligand also greatly facilitates the performance of JUC-1000 in the chemical fixation of carbon dioxide under ambient conditions, outperforming a series of benchmark catalysts.
      PubDate: 2018-02-19T12:50:34.872509-05:
      DOI: 10.1002/anie.201801122
       
  • Promoted Fixation of Molecular Nitrogen with Surface Oxygen Vacancies on
           Plasmon-Enhanced TiO2 Photoelectrodes
    • Authors: Chengcheng Li; Tuo Wang, Zhi-Jian Zhao, Weimin Yang, Jianfeng Li, Ang Li, Zhilin Yang, Geoffrey A. Ozin, Jinlong Gong
      Abstract: A hundred years on energy-intensive Haber-Bosch process continuously turn the nitrogen in air into fertilizer, nourishing billions of people while causing pollution and greenhouse gas emissions. The urgency of mitigating climate change motivates people to progress towards a more sustainable way in fixing nitrogen based on clean energy. Surface oxygen vacancies (surface Ovac) hold great potential for N2 adsorption and activation, but introducing Ovac on the very surface without affecting bulk properties remains a great challenge. This communication describes the promotional role of surface OVac in outer layers of amorphous TiO2 thin films in the adsorption and activation of nitrogen. This facilitates nitrogen reduction to ammonia by excited electrons from ultraviolet-light-driven rutile TiO2 nanorod arrays and visible-light-driven Au surface plasmons. This demonstration contributes to the ongoing efforts of developing new approaches for nitrogen fixation under ambient conditions. (i.e., room temperature, atmospheric pressure).
      PubDate: 2018-02-19T11:20:55.452865-05:
      DOI: 10.1002/anie.201713229
       
  • Postsynthetic Functionalization of Three-Dimensional Covalent Organic
           Framework for Selective Extraction of Lanthanide Ions
    • Authors: Qianrong Fang; Qiuyu Lu, Yunchao Ma, Hui Li, Xinyu Guan, Yusran Yusran, Ming Xue, Yushan Yan, Shilun Qiu, Valentin Valtchev
      Abstract: Chemical Functionalization of covalent organic frameworks (COFs) is critical to tune their properties and broaden their potential applications. However, the introduction of functional groups especially in three-dimensional (3D) COFs still remains largely unexplored. Here we report a general strategy for generating a 3D carboxyl-functionalized COF through postsynthetic modification of a hydroxyl COF, and for the first time explore the carboxyl COF for selective extraction of lanthanide ions. The obtained COF shows high crystalllinity, good chemical stability, and large specific surface area. Furthermore, the carboxyl COF displays high metal loading capacities together with excellent adsorption selectivity for Nd3+ over Sr2+ and Fe3+ confirmed by the Langmuir adsorption isotherms and ideal adsorbed solution theory (IAST) calculations. This study not only provides a strategy for versatile functionalization of 3D COFs, but also opens the route to their environmental related applications.
      PubDate: 2018-02-19T10:15:25.010286-05:
      DOI: 10.1002/anie.201712246
       
  • Peter J. Dunn Award / International Solvay Chair in Chemistry for Gernot
           Frenking / Max Born Prize for Angel Rubio / Terrae Rarae Prize for Rhett
           Kempe / Frontiers in Chemical Energy Science Award for Karsten Reuter /
           And also in the News
    • PubDate: 2018-02-19T09:30:23.436394-05:
      DOI: 10.1002/anie.201801578
       
  • Dual input regulation and positional control in hybrid
           oligonucleotide-discotic supramolecular wires
    • Authors: Miguel Ángel Alemán García; Eva Magdalena Estirado, Lech-Gustav Milroy, Luc Brunsveld
      Abstract: The combination of oligonucleotides and synthetic supramolecular systems allows for novel and long needed modes of regulation of the self-assembly of both molecular elements. Discotic molecules were conjugated with short oligonucleotides and their assembly into responsive supramolecular wires studied. The self-assembly of the discotics provides additional stability for DNA-duplex formation due to a cooperative effect. Reversely, the appended oligonucleotides allow for positional control of the discotic elements within the supramolecular wire. The programmed assembly of these hybrid architecture can be modulated via the DNA, e.g. by changing the number of base pairs or salt concentration, and via the discotic platform by the addition of discotics without oligonucleotide handles. These hybrid supramolecular-DNA structures allow for advanced levels of control over 1-D dynamic platforms with responsive regulatory elements at the interface with biological systems.
      PubDate: 2018-02-19T09:26:22.149001-05:
      DOI: 10.1002/anie.201800148
       
  • Towards structural studies of self-assembled subviral particles: combining
           cell-free expression with 100 kHz MAS NMR
    • Authors: Guillaume David; Marie-Laure Fogeron, Maarten Schledorn, Roland Montserret, Uta Haselmann, Susanne Penzel, Aurelie Badillo, Lauriane Lecoq, Patrice André, Michael Nassal, Ralf Bartenschlager, Beat H Meier, Anja Böckmann
      Abstract: Viral membrane proteins are prime targets in the combat against infection. Still, their structure determination remains a challenge, both with respect to sample preparation, and the need for structural methods allowing analysis in a native-like lipid environment. Cell-free protein synthesis and solid-state NMR are promising approaches in this context, one with respect to its high potential of native expression of complex proteins, and the other for its ability to analyze membrane proteins in lipids. We here show that milligram amounts of the small envelope protein of the duck hepatitis B virus (DHBV) can be produced using cell-free expression, and that the protein self-assembles into subviral particles. 2D proton-detected NMR spectra recorded at 110 kHz magic angle spinning on < 500 μg protein show a number of isolated peaks with linewidths comparable to model membrane proteins, paving the way for structural studies this homologous protein to a potential drug target in HBV infection.
      PubDate: 2018-02-19T09:22:17.805344-05:
      DOI: 10.1002/anie.201712091
       
  • Designed Long-Lived Emission from CdSe Quantum Dots through Reversible
           Electronic Energy Transfer with a Surface-Bound Chromophore
    • Authors: Marcello La Rosa; Sergey A. Denisov, Gediminas Jonusauskas, Nathan D. McClenaghan, Alberto Credi
      Abstract: The size-tunable emission of luminescent quantum dots (QDs) makes them highly interesting for applications that range from bioimaging to optoelectronics. For the same applications, engineering their luminescence lifetime, in particular, making it longer, would be as important; however, no rational approach to reach this goal is available to date. We describe a strategy to prolong the emission lifetime of QDs through electronic energy shuttling to the triplet excited state of a surface-bound molecular chromophore. To implement this idea, we made CdSe QDs of different sizes and carried out self-assembly with a pyrene derivative. We observed that the conjugates exhibit delayed luminescence, with emission decays that are prolonged by more than 3 orders of magnitude (lifetimes up to 330 μs) compared to the parent CdSe QDs. The mechanism invokes unprecedented reversible quantum dot to organic chromophore electronic energy transfer.Extended play: The first examples of delayed luminescence involving CdSe quantum dots are reported, with by emission decays that are prolonged by more than 3 orders of magnitude (lifetimes up to 330 μs) compared to analogous parent compounds. The mechanism involves unprecedented reversible quantum dot to organic chromophore electronic energy transfer.
      PubDate: 2018-02-19T08:26:16.165037-05:
      DOI: 10.1002/anie.201712403
       
  • Stimuli-Responsive Dual-Color Photon Upconversion: A Singlet-to-Triplet
           Absorption Sensitizer in a Soft Luminescent Cyclophane
    • Authors: Kazuma Mase; Yoichi Sasaki, Yoshimitsu Sagara, Nobuyuki Tamaoki, Christoph Weder, Nobuhiro Yanai, Nobuo Kimizuka
      Abstract: Reversible emission color switching of TTA-UC (triplet–triplet annihilation-based photon upconversion) has been achieved, as shown by N. Yanai, N. Kimizuka et al. in their Communication (
      DOI : 10.1002/anie.201712644). An Os complex sensitizer displays large anti-Stokes shift by direct singlet-to-triplet NIR excitation, and the combination with a luminescent cyclophane emitter allows thermally reversible upconversion color switching between the green-emissive crystalline state and yellow-emissive nematic state.
      PubDate: 2018-02-19T08:26:09.418131-05:
       
  • Porphyrin-Based Symmetric Redox-Flow Batteries towards Cold-Climate Energy
           Storage
    • Authors: Ting Ma; Zeng Pan, Licheng Miao, Chengcheng Chen, Mo Han, Zhenfeng Shang, Jun Chen
      Abstract: Electrochemical energy storage with redox-flow batteries (RFBs) under subzero temperature is of great significance for the use of renewable energy in cold regions. However, RFBs are generally used above 10 °C. Herein we present non-aqueous organic RFBs based on 5,10,15,20-tetraphenylporphyrin (H2TPP) as a bipolar redox-active material (anode: [H2TPP]2−/H2TPP, cathode: H2TPP/[H2TPP]2+) and a Y-zeolite–poly(vinylidene fluoride) (Y-PVDF) ion-selective membrane with high ionic conductivity as a separator. The constructed RFBs exhibit a high volumetric capacity of 8.72 Ah L−1 with a high voltage of 2.83 V and excellent cycling stability (capacity retention exceeding 99.98 % per cycle) in the temperature range between 20 and −40 °C. Our study highlights principles for the design of RFBs that operate at low temperatures, thus offering a promising approach to electrochemical energy storage under cold-climate conditions.Hot stuff when it gets chilly: Redox-flow batteries (RFBs) for energy storage at subzero temperatures would facilitate the use of renewable energy in cold regions. Such non-aqueous RFBs with high volumetric capacity, high voltage, and excellent cycling stability between 20 and −40 °C have been developed with the porphyrin H2TPP as a bipolar redox-active material and a Y-zeolite–poly(vinylidene fluoride) ion-selective membrane.
      PubDate: 2018-02-19T08:25:59.601933-05:
      DOI: 10.1002/anie.201713423
       
  • Total Synthesis of Astellatol
    • Authors: Nan Zhao; Shuqiang Yin, Shengling Xie, Hao Yan, Pan Ren, Gui Chen, Fang Chen, Jing Xu
      Abstract: Chinese paper cutting is a long-standing tradition in China, and often used to decorate doors and windows during the Spring Festival. The Chinese character 福 means blessing and happiness and the character 春 means spring. With this backdrop, J. Xu et al. present in their Communication (
      DOI : 10.1002/anie.201800167) the first enantiospecific synthesis for a three-decade-old synthetic challenge, astellatol.
      PubDate: 2018-02-19T08:25:51.172183-05:
       
  • A C=O⋅⋅⋅Isothiouronium Interaction Dictates Enantiodiscrimination in
           Acylative Kinetic Resolutions of Tertiary Heterocyclic Alcohols
    • Authors: Mark D. Greenhalgh; Samuel M. Smith, Daniel M. Walden, James E. Taylor, Zamira Brice, Emily R. T. Robinson, Charlene Fallan, David B. Cordes, Alexandra M. Z. Slawin, H. Camille Richardson, Markas A. Grove, Paul Ha-Yeon Cheong, Andrew D. Smith
      Abstract: A combination of experimental and computational studies have identified a C=O⋅⋅⋅isothiouronium interaction as key to efficient enantiodiscrimination in the kinetic resolution of tertiary heterocyclic alcohols bearing up to three potential recognition motifs at the stereogenic tertiary carbinol center. This discrimination was exploited in the isothiourea-catalyzed acylative kinetic resolution of tertiary heterocyclic alcohols (38 examples, s factors up to>200). The reaction proceeds at low catalyst loadings (generally 1 mol %) with either isobutyric or acetic anhydride as the acylating agent under mild conditions.Test your resolve: Experimental and computational studies have identified a C=O⋅⋅⋅isothiouronium interaction as key to efficient enantiodiscrimination in the kinetic resolution of tertiary heterocyclic alcohols with up to three potential recognition motifs at the stereogenic tertiary carbinol center. The kinetic resolution of a range of such alcohols was achieved with an isothiourea catalyst and either isobutyric or acetic anhydride.
      PubDate: 2018-02-19T08:21:06.151866-05:
      DOI: 10.1002/anie.201712456
       
  • Isotope Substitution of Promiscuous Alcohol Dehydrogenase Reveals the
           Origin of Substrate Preference in the Transition State
    • Authors: Enas M. Behiry; J. Javier Ruiz-Pernia, Louis Luk, Iñaki Tuñón, Vicent Moliner, Rudolf K. Allemann
      Abstract: The origin of substrate preference in promiscuous enzymes was investigated by enzyme isotope labelling of the alcohol dehydrogenase from Geobacillus stearothermophilus (BsADH). At physiological temperature, protein dynamic coupling to the reaction coordinate was insignificant. However, the extent of dynamic coupling was highly substrate-dependent at lower temperatures. For benzyl alcohol, an enzyme isotope effect larger than unity was observed, whereas the enzyme isotope effect was close to unity for isopropanol. Frequency motion analysis on the transition states revealed that residues surrounding the active site undergo substantial displacement during catalysis for sterically bulky alcohols. BsADH prefers smaller substrates, which cause less protein friction along the reaction coordinate and reduced frequencies of dynamic recrossing. This hypothesis allows a prediction of the trend of enzyme isotope effects for a wide variety of substrates.Take the bad with the good: The origin of substrate preference in promiscuous enzymes was investigated by enzyme isotope labelling of the alcohol dehydrogenase from BsADH. The results show that “good” substrates induce fewer recrossing events along the antisymmetric reaction coordinate due to efficient electrostatic preorganization. In contrast, “bad” substrates cause substantial active-site reorganization, and electrostatic preorganization is suboptimal.
      PubDate: 2018-02-19T08:10:31.111218-05:
      DOI: 10.1002/anie.201712826
       
  • Accessing Tetravalent Transition-Metal Nitridophosphates through
           High-Pressure Metathesis
    • Authors: Simon D. Kloß; Sophia Wandelt, Andreas Weis, Wolfgang Schnick
      Abstract: Advancing the attainable composition space of a compound class can lead to fascinating materials. The first tetravalent metal nitridophosphate, namely Hf9−xP24N52−4xO4x (x≈1.84), was prepared by high-pressure metathesis. The Group 4 nitridophosphates are now an accessible class of compounds. The high-pressure metathesis reaction using a multianvil setup yielded single crystals that were suitable for structure analysis. Magnetic properties of the compound indicate Hf in oxidation state +IV. Optical measurements show a band gap in the UV region. The presented route unlocks the new class of Group 4 nitridophosphates by significantly improving the understanding of this nitride chemistry. Hf9−xP24N52−4xO4x (x≈1.84) is a model system and its preparation is the first step towards a systematic exploration of the transition-metal nitridophosphates.Working under pressure: A tetravalent transition-metal nitridophosphate, namely Hf9−xP24N52−4xO4x (x≈1.84), was prepared by high-pressure metathesis. Its preparation highlights the systematic access to transition-metal nitridophosphates, which is potentially granted by high-pressure metathesis.
      PubDate: 2018-02-19T08:00:27.594479-05:
      DOI: 10.1002/anie.201712006
       
  • Carbon Atom Hybridization Matters: Ultrafast Humidity Response of
           Graphdiyne Oxides
    • Authors: Lanqun Mao; Hailong Yan, Shuyue Guo, Fei Wu, Ping Yu, Huibiao Liu, Yuliang Li
      Abstract: Graphdiyne (GDY), a new kind of 2D carbon allotrope consisting of sp- and sp2-hybridized carbon atoms, has been envisaged to be promising in fundamental studies and various applications due to their unique atomic arrangement and electronic structure as well as surface chemistry. We herein for the first time find that graphdiyne oxide (GDO) exhibits an ultrafast humidity response with an unprecedented response speed (~ 7 ms), which is considered to benefit from the unique carbon hybridization of GDO that contains acetylenic bonds with stronger electron-withdrawing property than ethylenic bonds in GO. The GDO-based humidity sensor shows an ultrafast response speed, good selectivity and high sensitivity. These properties well validate the sensor to monitor the respiration rate change of human and hypoxic rats. This study not only demonstrates the unprecedented humidity-sensing capability of GDO but also provides new insight into the structure-property relationship of 2D carbon materials.
      PubDate: 2018-02-19T07:15:31.889848-05:
      DOI: 10.1002/anie.201709417
       
  • Features of protonation of the simplest weakly basic molecules, SO2, CO,
           N2O, CO2, and others, by solid carborane superacids
    • Authors: Evgenii Stoyanov; Irina S Stoyanova
      Abstract: Experimental study on protonation of simple weakly basic molecules (L) by the strongest solid superacid, H(CHB11F11), showed that basicity of SO2 is high enough (during attachment to the acidic H atoms at partial pressure of 1 atm) to break the bridged H-bonds of the polymeric acid and to form a mixture of solid mono- and disolvates, LH+‧‧‧An˗ and L-H+-L. With a decrease in the basicity of L = CO (via C), N2O, and CO (via O), only proton monosolvates are formed, which approach L-H+-An species with convergence of the strengths of bridged H-bonds. The molecules with the weakest basicity, such as CO2 and weaker, when attached to the proton, cannot break the bridged H-bond of the polymeric superacid, and the interaction stops at stage of physical adsorption. It is shown here that under the conditions of acid monomerization, it is possible to protonate such weak bases as CO2, N2, and Xe.
      PubDate: 2018-02-19T06:21:13.012362-05:
      DOI: 10.1002/anie.201704645
       
  • Frontispiece: Enantio- and Diastereoselective Cyclopropanation of
           1-Alkenylboronates: Synthesis of 1-Boryl-2,3-Disubstituted Cyclopropanes
    • Authors: Javier Carreras; Ana Caballero, Pedro J. Pérez
      Abstract: Asymmetric Cyclopropanation A. Caballero, P. Pérez et al. describe in their Communication on page 2334 ff. a method for the highly selective conversion of terminal alkynes into 2,3-disubstituted 1-borylcyclopropanes.
      PubDate: 2018-02-19T05:32:57.215226-05:
      DOI: 10.1002/anie.201880961
       
  • The Dewar isomer of 1,2-dihydro-1,2-azaborinines: Isolation,
           fragmentation, and energy storage
    • Authors: Holger Bettinger; Klara Edel, Xinyu Xinyu, Jacob Ishibashi, Ashley Lamm, Cäcilia Maichle-Mössmer, Zachary Giustra, Shih-Yuan Liu
      Abstract: The photochemistry of 1,2-dihydro-1,2-azaborinine derivatives was studied under matrix isolation conditions and in solution. Photoisomerization occurs exclusively to the Dewar valence isomers upon irradiation with UV light (> 280 nm) with high quantum yield (46 %). Further photolysis with UV light (254 nm) results in the formation of cyclobutadiene and iminoborane. The thermal electrocyclic ring opening reaction of the Dewar valence isomer back to the 1,2-dihydro-1-tert-butyldimethylsilyl-2-mesityl-1,2-azaborinine has an activation barrier of 27.0 ± 1.2 kcal·mol-1. In the presence of Wilkinson's catalyst, the ring opening occurs rapidly and exothermically (H = -48 ± 1 kcal·mol-1) at room temperature.
      PubDate: 2018-02-19T05:22:50.724463-05:
      DOI: 10.1002/anie.201712683
       
  • Tailored microstructured hyperpolarizing matrices for optimal magnetic
           resonance imaging
    • Authors: Matthieu Cavaillès; Aurélien bornet, Xavier Jaurand, Basile Vuichoud, David Baudouin, Mathieu Baudin, Laurent Veyre, Geoffrey Baudenhausen, Jean-Nicolas Dumez, Sami Jannin, Christophe Copéret, Chloé Thieuleux
      Abstract: Tailoring the physical features and the porous network architecture of silica-based hyperpolarizing solids containing TEMPO radicals, known as HYPSO (HYbrid Polarizing SOlids), enable unprecedented performance of dissolution Dynamic Nuclear Polarization (d-DNP). High polarization values up to P(1H) = 99 % were reached for samples impregnated with a mixture of H2O:D2O and loaded in a 6.7 T polarizer at temperatures around 1.2 K. These HYPSO materials combine the best performance of homogeneous DNP formulations with the advantages of solid polarizing matrices which provide hyperpolarized solutions free of any - potentially toxic - additives (radicals and glass-forming agents). The hyperpolarized solutions can be expelled from the porous solids, filtered and rapidly transferred either to a Nuclear Magnetic Resonance (NMR) spectrometer or to a Magnetic Resonance Imaging (MRI) system.
      PubDate: 2018-02-19T05:21:32.507433-05:
      DOI: 10.1002/anie.201801009
       
  • On the Upper Limits of Oxidation States in Chemistry
    • Authors: Shu-Xian Hu; Wan-Lu Li, Jun-Bo Lu, Junwei Lucas Bao, Haoyu S. Yu, Donald G. Truhlar, John K. Gibson, Joaquim Marçalo, Mingfei Zhou, Sebastian Riedel, W. H. Eugen Schwarz, Jun Li
      Abstract: The concept of oxidation state (OS) is based on the concept of Lewis electron pairs, in which the bonding electrons are assigned to the more electronegative element. This approach is useful for keeping track of the electrons, predicting chemical trends, and guiding syntheses. Experimental and quantum-chemical results reveal a limit near +8 for the highest OS in stable neutral chemical substances under ambient conditions. OS=+9 was observed for the isolated [IrO4]+ cation in vacuum. The prediction of OS=+10 for isolated [PtO4]2+ cations is confirmed computationally for low temperatures only, but hasn't yet been experimentally verified. For high OS species, oxidation of the ligands, for example, of O−2 with formation of .O−1 and O−O bonds, and partial reduction of the metal center may be favorable, possibly leading to non-Lewis type structures.The highest oxidation state (OS) of elements in compounds is limited not only by the number and the ionization energies of their valence electrons, but also by the electronic properties of the ligands. Spontaneous oxidation of the ligand and reduction of the metal center results in strongly correlated, open-shell, multicenter bonds. A joint theoretical–experimental case study of PtO42+ isomers reveals a maximum OS near +8 for chemical substances under ambient conditions.
      PubDate: 2018-02-19T03:04:36.916527-05:
      DOI: 10.1002/anie.201711450
       
  • A Non-Heme Iron Photocatalyst for Light-Driven Aerobic Oxidation of
           Methanol
    • Authors: Juan Chen; Stepan Stepanovic, Apparao Draksharapu, Maja Gruden, Wesley R. Browne
      Abstract: Non-heme (L)FeIII and (L)FeIII-O-FeIII(L) complexes (L=1,1-di(pyridin-2-yl)-N,N-bis(pyridin-2-ylmethyl)ethan-1-amine) underwent reduction under irradiation to the FeII state with concomitant oxidation of methanol to methanal, without the need for a secondary photosensitizer. Spectroscopic and DFT studies support a mechanism in which irradiation results in charge-transfer excitation of a FeIII−μ-O−FeIII complex to generate [(L)FeIV=O]2+ (observed transiently during irradiation in acetonitrile), and an equivalent of (L)FeII. Under aerobic conditions, irradiation accelerates reoxidation from the FeII to the FeIII state with O2, thus closing the cycle of methanol oxidation to methanal.Cut out the middlecat: Non-heme (L)FeIII and (L)FeIII−O−FeIII(L) complexes were reduced under irradiation to the FeII state (see scheme) with concomitant oxidation of methanol to methanal, without a photosensitizer. Spectroscopic and DFT studies support a mechanism involving charge-transfer excitation of a FeIII−μ-O−FeIII complex to generate [(L)FeIV=O]2+ and (L)FeII. Irradiation accelerates reoxidation of FeII with O2 to close the catalytic cycle.
      PubDate: 2018-02-19T02:51:23.521235-05:
      DOI: 10.1002/anie.201712678
       
  • Palladium-Catalyzed C−H Silylation through Palladacycles Generated
           from Aryl Halides
    • Authors: Ailan Lu; Xiaoming Ji, Bo Zhou, Zhuo Wu, Yanghui Zhang
      Abstract: A highly efficient palladium-catalyzed disilylation reaction of aryl halides through C−H activation has been developed for the first time. The reaction has broad substrate scope. A variety of aryl halides can be disilylated by three types of C−H activation, including C(sp2)−H, C(sp3)−H, and remote C−H activation. In particular, the reactions are also unusually efficient. The yields are essentially quantitative in many cases, even in the presence of less than 1 mol % catalyst and 1 equivalent of the silylating reagent under relatively mild conditions. The disilylated biphenyls can be converted into disiloxane-bridged biphenyls.Choice of three: A palladium-catalyzed disilylation reaction of aryl halides has been developed through C−H activation. The reaction has broad substrate scope and is unusually efficient. A variety of aryl halides can be disilylated by three types of C−H activation, including C(sp2)−H, C(sp3)−H, and remote C−H activation, in excellent yields. The method is scalable and features high atom economy.
      PubDate: 2018-02-19T02:51:15.159871-05:
      DOI: 10.1002/anie.201800330
       
  • Confined Self-Assembly in Two-Dimensional Interlayer Space: Monolayered
           Mesoporous Carbon Nanosheets with In-Plane Orderly Arranged Mesopores and
           a Highly Graphitized Framework
    • Authors: Jie Wang; Yunling Xu, Bing Ding, Zhi Chang, Xiaogang Zhang, Yusuke Yamauchi, Kevin C.-W. Wu
      Abstract: Mesoporous carbon nanosheets are prepared through assembly of a carbon precursor and a block copolymer in the confined interlayer space of montmorillonite. X. Zhang, K. C.-W. Wu, and co-workers show in their Communication (
      DOI : 10.1002/anie.201712959) that ordered mesopores exposed on the carbon nanosheet realize efficient diffusion of guest molecules from outside. The confined environment favors the formation of highly graphitic carbon, which can achieve fast electron transportation.
      PubDate: 2018-02-19T02:51:06.888892-05:
       
  • Dynamic Interconversion between Boroxine Cages Based on Pyridine Ligation
    • Authors: Kosuke Ono; Shunsuke Shimo, Kohei Takahashi, Nobuhiro Yasuda, Hidehiro Uekusa, Nobuharu Iwasawa
      Abstract: The dynamic interconversion of large covalent organic cages was achieved simply by heating or acid/base treatment. In their Communication (
      DOI : 10.1002/anie.201713221), N. Iwasawa and co-workers show that a mixture of the boroxine cages 12-mer and 15-mer was cleanly converted into a pyridine adduct of the boroxine cage 9-mer upon treatment with pyridine, and the geometry of N-coordinated boron atoms changed from trigonal to tetrahedral. This is the first covalent organic cage molecule that undergoes a reversible transformation between different cage structures.
      PubDate: 2018-02-19T02:51:04.438949-05:
       
  • Tailored Organic Electrode Material Compatible with Sulfide Electrolyte
           for Stable All-Solid-State Sodium Batteries
    • Authors: Xiaowei Chi; Yanliang Liang, Fang Hao, Ye Zhang, Justin Whiteley, Hui Dong, Pu Hu, Sehee Lee, Yan Yao
      Abstract: All-solid-state sodium batteries require chemical and electrochemical compatibility between cathode materials and solid-state sodium-ion electrolytes for a stable cycling performance. In their Communication (
      DOI : 10.1002/anie.201712895), Y. Yao et al. report a solid-state sodium battery with record-high cycling stability and one of the highest specific energies based on an organic quinone (Na4C6O6) as the cathode material that is compatible with sulfide electrolytes.
      PubDate: 2018-02-19T02:51:02.016622-05:
       
  • A New Portal to SuFEx Click Chemistry: A Stable Fluorosulfuryl Imidazolium
           Salt Emerging as an “F−SO2+” Donor of Unprecedented Reactivity,
           Selectivity, and Scope
    • Authors: Taijie Guo; Genyi Meng, Xiongjie Zhan, Qian Yang, Tiancheng Ma, Long Xu, K. Barry Sharpless, Jiajia Dong
      Abstract: A fluorosulfuryl imidazolium salt delivers an “F−SO2+” group to phenols and amines with phenomenal efficiency. In their Communication (
      DOI : 10.1002/anie.201712429), K. B. Sharpless, J. Dong, and co-workers present the practical, mole-scale synthesis of this stable, powerful reagent that provides clickable RNHSO2F, dramatically expands the scope of SuFEx products, and constitutes a complementary alternative to SO2F2 gas delivery.
      PubDate: 2018-02-19T02:50:27.143531-05:
       
  • IR Spectrum and Structure of Protonated Monosilanol: Dative Bonding
           between Water and the Silylium Ion
    • Authors: Martin Andreas Robert George; Nguyen Xuan Truong, Marco Savoca, Otto Dopfer
      Abstract: Dative bonding between the highly reactive silyl cation and water in a protonated silanol was probed with infrared spectroscopy and DFT calculations by O. Dopfer and co-workers in their Communication (
      DOI : 10.1002/anie.201712999). The determined structure, bonding, and infrared fingerprint of this simplest but elusive silanol cation may guide its identification in interstellar space as well as in terrestrial silane plasmas used for the fabrication of microelectronic devices.
      PubDate: 2018-02-19T02:50:22.166068-05:
       
  • From Linear to Angular Isomers: Achieving Tunable Charge Transport in
           Single Crystal Indolocarbazoles via Delicate Synergetic CH/NH···Pi
           Interactions
    • Authors: Hui Jiang; Peng Hu, Jun Ye, Apoorva Chaturvedi, Keke K. Zhang, Yongxin Li, Yi Long, Denis Fichou, Christian Kloc, Wenping Hu
      Abstract: Four five fused-ring isomers were rationally designed and synthesized to investigate the isomeric influence of linear and angular shapes in affecting their molecular packing and resultant electronic properties. Single-crystal field-effect transistors showed mobility order of 5,7-ICZ (3.61 cm2 V-1 s-1)> 5,11-ICZ (0.55 cm2 V-1 s-1)> 5,12-ICZ (~10-5 cm2 V-1 s-1) and 11,12-ICZ (~10-6 cm2 V-1 s-1). Theoretical calculations based on density functional theory (DFT) and polaron transport model revealed that 5, 7-ICZ can reach higher mobilities than the others thanks to relatively higher hole transfer integral that links to stronger intermolecular interaction due to the presence of multiple NH···pi and CH···pi(py) interactions with energy close to common NH···N hydrogen bonds, as well as overall lower hole-vibrational coupling owing to the absence of coupling of holes to low frequency modes due to better pi conjugation.
      PubDate: 2018-02-18T23:47:16.953547-05:
      DOI: 10.1002/anie.201713288
       
  • Electrochemical Exfoliation of Pillared-layer Metal-Organic Framework for
           Boosting the Oxygen Evolution Reaction
    • Authors: Jin Huang; Yu Li, Rui-Kang Huang, Chun-Ting He, Li Gong, Qiong Hu, Lishi Wang, Yan-Tong Xu, Xiao-Yun Tian, Si-Yang Liu, Zi-Ming Ye, Fuxin Wang, Dong-Dong Zhou, Wei-Xiong Zhang, Jie-Peng Zhang
      Abstract: Having high surface areas and fully exposed active sites, two-dimensional (2D) materials and ultrathin nanosheets are advantageous for elevating the catalysis performance and elucidating the catalysis mechanism. 2D materials are mostly restricted to inorganic or organic materials based on covalent bonds, because strong bonding within two dimensions and weak interactions in the third dimension are beneficial to stabilize the 2D structure. Here, we report an electrochemical exfoliation strategy for synthesizing metal-organic 2D materials based on coordination bonds. A catechol functionalized ligand is used as the redox active pillar to construct a pillared-layer framework. As an electrocatalyst for water oxidation, the pillar ligand can be in-situ oxidized and removed to yield ultrathin (2 nm) nanosheets, giving extraordinary catalytic activity at pH = 13 with overpotential as low as 211 mV at 10 mA cm^-2 and turnover frequency as high as 34 s^-1 at an overpotential of 300 mV.
      PubDate: 2018-02-18T21:50:31.458708-05:
      DOI: 10.1002/anie.201801029
       
  • Tracking the Dynamic Folding and Unfolding of RNA G-Quadruplexes in Live
           Cells
    • Authors: Xiu-Cai Chen; Shuo-Bin Chen, Jing Dai, Jia-Hao Yuan, Tian-Miao Ou, Zhi-Shu Huang, Jia-Heng Tan
      Abstract: Due to the absence of methods for tracking RNA G-quadruplex dynamics, especially the folding and unfolding of this attractive structure in live cells, understanding of the biological roles of RNA G-quadruplexes is so far limited. Here we reported a new red-emitting fluorescent probe, QUMA-1, for a selective, continuous and real-time visualization of RNA G-quadruplexes in live cells. The applications of QUMA-1 in several previously intractable applications, including live-cell imaging of the dynamic folding, unfolding and movement of RNA G-quadruplexes and visualizing the unwinding of RNA G-quadruplexes by RNA helicase have been demonstrated. Notably, our real-time results revealed the complexity of the dynamics of RNA G-quadruplexes in live cells. We anticipate that the further application of QUMA-1 in combination with appropriate biological and imaging methods to explore the dynamics of RNA G-quadruplexes will uncover more information about the biological roles of RNA G-quadruplexes.
      PubDate: 2018-02-17T10:40:36.042823-05:
      DOI: 10.1002/anie.201801999
       
  • Lewis Acid Catalyzed Stereoselective Dearomative Coupling of Indolylboron
           Ate Complexes with D-A Cyclopropanes and Alkyl Halides
    • Authors: Saikat Das; Constantin Gabriel Daniliuc, Armido Studer
      Abstract: Indolylboron ate complexes readily generated from 2-lithio indoles and boronic esters undergo multicomponent dearomative coupling with D-A cyclopropanes and alkyl halides in the presence of Sc(OTf)3 as a catalyst. Reactions proceed with complete diastereoselectivity and excellent stereospecificity to provide indolines bearing three contiguous stereocenters. The valuable boronic ester moiety remains in the product and allows for subsequent functionalization.
      PubDate: 2018-02-17T04:40:45.398446-05:
      DOI: 10.1002/anie.201711923
       
  • N-Heterocyclic Carbene-Treated Gold Surfaces in Pentacene Organic
           
    • Authors: Aifeng Lv; Matthias Freitag, Kathryn M. Chepiga, Andreas H. Schäfer, Frank Glorius, Lifeng Chi
      Abstract: N-Heterocyclic carbene (NHC) molecules, which reacted with the surface of Au electrodes, have been successfully applied in the pentacene transistors. With the application of NHCs, the charge carrier mobility of pentacene transistors increased by five times, while the contact resistance at the pentacene-Au interface reduced down to 85%. Even after annealing the NHC-Au electrodes at 200 oC for two hours before pentacene deposition, the charge carrier mobility of the pentacene transistors did not decrease. The distinguished performance renders the NHCs as excellent alternatives to thiols as metal modifiers for the application in organic field-effect transistors (OFETs).
      PubDate: 2018-02-16T21:40:33.903869-05:
      DOI: 10.1002/anie.201713415
       
  • Nucleopeptide Assemblies Selectively Sequester ATP in Cells
    • Authors: Huaimin Wang; Zhaoqianqi Feng, Yanan Qin, Jiaqing Wang, Bing Xu
      Abstract: Here we report that assemblies of nucleopeptides selectively sequestrate ATP in complex conditions (e.g., serum and cytosol). We develop assemblies of nucleopeptides that selectively sequester ATP over ADP. Counteracting enzymes interconvert ATP and ADP to modulate the nanostructures formed by the nucleopeptides and the nucleotides. The nucleopeptides, sequestering ATP effectively in cells, slow down efflux pumps in multidrug resistance cancer cells, thus boosting the efficacy of an anticancer drug. Examining additional 11 nucleopeptides (including D- and L-enantiomers) yields five more nucleopeptides that differentiate ATP and ADP via either precipitation or gelation. As the first example of using assemblies of nucleopeptides for interacting with ATP and disrupting intracellular ATP dynamics, this work illustrates the use of supramolecular assemblies to interact with small and essential biological molecules for controlling cell behaviors
      PubDate: 2018-02-16T15:40:35.06672-05:0
      DOI: 10.1002/anie.201712834
       
  • One-Step Synthesis of Hybrid Core-Shell Metal-Organic Frameworks
    • Authors: Xinyu Yang; Shuai Yuan, Lanfang Zou, Hannah Drake, Yingmu Zhang, Junsheng Qin, Ali Alsalme, Hongcai Zhou
      Abstract: Epitaxial growth of MOF-on-MOF composite is an evolving research topic. In current methods, the core-shell MOFs are synthesized via a stepwise strategy which involves growing the shell-MOFs on top of the preformed core-MOFs with matched lattice parameters. However, the inconvenient stepwise synthesis and the strict lattice-matching requirement have limited the development of core-shell MOFs. Herein, we demonstrate that hybrid core-shell MOFs with mismatching lattices can be synthesized under the guidance of nucleation kinetics. A series of MOF composites with mesoporous core and microporous shell were constructed and characterized by optical microscopy, powder X-ray diffraction, gas sorption measurement, and scanning electron microscopy. Isoreticular expansion of microporous shells and orthogonal modification of the core was realized to produce multifunctional MOF composites, which acted as size selective catalysts for olefin epoxidation with high activity and selectivity.
      PubDate: 2018-02-16T15:10:28.722138-05:
      DOI: 10.1002/anie.201710019
       
  • Direct Measurement of Charge Regulation in Metalloprotein Electron
           Transfer
    • Authors: Collin T. Zahler; Hongyu Zhou, Alireza Abdolvahabi, Rebecca L. Holden, Sanaz Rasouli, Peng Tao, Bryan Shaw
      Abstract: Quantifying how a protein regulates its net electrostatic charge during electron transfer (ET) is a means of directly measuring factors that contribute to either redox potential and/or reorganization energy. Charge regulation by proteins during ET has never been measured because few tools exist to measure the net charge of a folded protein in solution at different oxidation states. Here, by using protein charge ladders and capillary electrophoresis, we determined that the net charge of myoglobin, cytochrome c, and azurin changed by 0.62 ± 0.06, 1.19 ± 0.02, and 0.51 ± 0.04 units upon single ET. Computational analysis predicts that these fluctuations in charge arise from changes in the pKa of multiple non-coordinating residues (predominantly histidine) and require between 0.42-0.90 eV. These results suggest that ionizable residues can tune the reactivity of redox centers via charge regulation.
      PubDate: 2018-02-16T13:40:35.68446-05:0
      DOI: 10.1002/anie.201712306
       
  • Enhanced Photodynamic Therapy by Reduced Intracellular Glutathione Levels
           Employing Nano-MOF with Cu (II) as Active Center
    • Authors: Wei Zhang; Jun Lu, Xiaonan Gao, Ping Li, Wen Zhang, Yu Ma, Hui Wang, Bo Tang
      Abstract: In photodynamic therapy (PDT), the level of reactive oxygen species (ROS) produced in the cell directly determines therapeutic effect. Therefore, the development of photosensitizers combining the ability of reducing GSH levels through synergisticallyimproving ROS concentration to strengthen the efficacy of PDT for tumor is important. We report a nano-metal-organic framework based on Cu (II) as active center for PDT. This MOF-2 is readily uptaken by breast cancer cells, and high-level ROS is generated under light irradiation. Meanwhile, intracellular GSH is considerably decreased owing to absorption on MOF-2, synergistically increasing ROS concentration and accelerating apoptosis, thereby enhancing the effect of PDT. Notably, through the direct adsorption of GSH, MOF-2 showed comparable effect with commercial antitumor drug camptothecin in mouse breast cancer treatment. This work provides strong evidence for MOF-2 as a promising new PDT candidate and anti-cancer drug.
      PubDate: 2018-02-16T10:40:33.017094-05:
      DOI: 10.1002/anie.201710800
       
  • Selective sp3 C-H Aerobic Oxidation enabled by Deca-tungstate
           Photocatalysis in Flow
    • Authors: Gabriele Laudadio; Sebastian Govaerts, Ying Wang, Davide Ravelli, Hannes Koolman, Maurizio Fagnoni, Stevan Djuric, Timothy Noel
      Abstract: A mild and selective sp3 C-H aerobic oxidation enabled by deca-tungstate photocatalysis has been developed. The reaction can be significantly improved in a microflow reactor enabling the safe use of oxygen and the enhanced irradiation of the reaction mixture. Our method allows for the oxidation of both activated and unactivated C-H bonds (30 examples). The ability to selectively oxidize natural scaffolds, such as (-)-ambroxide, pregnenolone acetate, (+)-sclareolide and artemisinin exemplifies the utility of this new method.
      PubDate: 2018-02-16T10:05:48.637222-05:
      DOI: 10.1002/anie.201800818
       
  • Phosphinic Acid Based Linkers: New Building Block in MOF Chemistry
    • Authors: Jan Hynek; Petr Brázda, Jan Rohlíček, Michael G.S. Londesborough, Jan Demel
      Abstract: Metal-organic frameworks (MOFs) are a chemically and topologically diverse family of materials composed of inorganic nodes and organic linkers bound together by coordination bonds. In this contribution we present two significant innovations in this field. The first is the use of a new coordination group in phenylene-1,4-bis(methylphosphinic acid) (PBPA), a phosphinic acid analogue of commonly-used terephtalic acid. We show that the use of this new linker group leads to the formation of a hydrothermally stable permanently porous MOF structure. The second innovation is the application of electron diffraction tomography (EDT), coupled with dynamical refinement of the EDT data, to the elucidation of the structure of the new material including the localization of hydrogen atoms.
      PubDate: 2018-02-16T09:10:29.24026-05:0
      DOI: 10.1002/anie.201800884
       
  • Kallol Ray
    • PubDate: 2018-02-16T06:47:48.822027-05:
      DOI: 10.1002/anie.201801205
       
  • Dynamic Covalent Chemistry. Principles, Reactions, and Applications Edited
           by Wei Zhang and Yinghua Jin.
    • Authors: Stefan Kubik
      Abstract: John Wiley and Sons, Hoboken 2018. 464 pp., hardcover, € 182.00.—ISBN 978-1119075639
      PubDate: 2018-02-16T06:47:42.718754-05:
      DOI: 10.1002/anie.201801152
       
  • Supramolecular Modulation of Structural Polymorphism in Pathogenic
           α-Synuclein Fibrils Using Copper(II) Coordination
    • Authors: Tae Su Choi; Jeeyoung Lee, Jong Yoon Han, Byung Chul Jung, Piriya Wongkongkathep, Joseph A. Loo, Min Jae Lee, Hugh I. Kim
      Abstract: Structural variation of α-synuclein (αSyn) fibrils has been linked to the diverse etiologies of synucleinopathies. However, little is known about what specific mechanism provides αSyn fibrils with pathologic features. Herein, we demonstrate Cu(II)-based supramolecular approach for unraveling the formation process of pathogenic αSyn fibrils and its application in a neurotoxic mechanism study. The conformation of αSyn monomer was strained by macrochelation with Cu(II), thereby disrupting the fibril elongation while promoting its nucleation. This non-canonical process formed shortened, β-sheet enriched αSyn fibrils (
      PubDate: 2018-02-16T06:47:28.553282-05:
      DOI: 10.1002/anie.201712286
       
  • Phosphine-Catalyzed anti-Carboboration of Alkynoates with 9-BBN-Based
           1,1-Diborylalkanes: Synthesis and Use of Multisubstituted
           γ-Borylallylboranes
    • Authors: Ayaka Yamazaki; Kazunori Nagao, Tomohiro Iwai, Hirohisa Ohmiya, Masaya Sawamura
      Abstract: Trialkylphosphine organocatalysis has enabled the regioselective anti-carboboration of alkynoates with 9-BBN-based 1,1-diborylalkanes to produce secondary allylboranes with β-alkoxycarbonyl and γ-boryl substituents. The utility of the densely functionalized allylboranes was demonstrated by the highly diastereoselective allylation of N-(trimethylsilyl)aldimines to produce homoallylamines containing tertiary allylborane and acrylate moieties.B selective, B versatile: Trialkylphosphine organocatalysis enabled the regioselective anti-carboboration of alkynoates with 1,1-diborylalkanes to produce secondary allylboranes with β-alkoxycarbonyl and γ-boryl substituents (see scheme). The densely functionalized allylboranes underwent highly diastereoselective allylation of N-(trimethylsilyl)aldimines to produce homoallylamines containing tertiary allylborane and acrylate moieties.
      PubDate: 2018-02-16T06:46:47.484817-05:
      DOI: 10.1002/anie.201712351
       
  • Unsymmetrical, Cyclic Diborenes and Thermal Rearrangement to a
           Borylborylene
    • Authors: Tom Stennett; James Mattock, Ivonne Vollert, Alfredo Vargas, Holger Braunschweig
      Abstract: Cyclic diboranes(4) based on a chelating monoanionic benzylphosphine linker were prepared by boron-silicon exchange between arylsilanes and B2Br4. Coordination of Lewis bases to the remaining sp2 boron atom yielded unsymmetrical sp3-sp3 diboranes, which were reduced with KC8 to their corresponding trans-diborenes. These compounds were studied by a combination of spectroscopic methods, X-ray diffraction and DFT calculations. PMe3-stabilized diborene 6 was found to undergo thermal rearrangement to gem-diborene 8. DFT calculations on 8 reveal a polar boron-boron bond, and indicate that the compound is best described as a borylborylene.
      PubDate: 2018-02-16T06:44:55.958109-05:
      DOI: 10.1002/anie.201800671
       
  • Synthesis of Biaryls via Hypervalent Iodine-Tethered Sigmatropic
           Rearrangement
    • Authors: Mitsuki Hori; Jing-Dong Guo, Tomoyuki Yanagi, Keisuke Nogi, Takahiro Sasamori, Hideki Yorimitsu
      Abstract: Metal-free dehydrogenative coupling of aryliodanes with phenols to afford 2-hydroxy-2'-iodobiaryls has been developed. This reaction proceeds via ligand exchange on the hypervalent iodine atom, followed by [3,3] sigmatropic rearrangement, to realize exclusive regioselectivity. This coupling, in combination with in situ oxidation by mCPBA, facilitates the convenient conversion of iodoarenes into the desired biaryls. The obtained biaryls have convertible iodo and hydroxy groups in close proximity, and are thus synthetically useful, as exemplified by the controlled syntheses of π-expanded furans and a substituted [5] helicene. DFT calculations clearly revealed that the rearrangement is sigmatropic and involves C-C bond formation and I-O bond cleavage in a concerted manner. Acetic acid, which was found to be the best solvent for this protocol, would make the iodine atom more cationic and thus accelerate the sigmatropic rearrangement.
      PubDate: 2018-02-16T06:41:45.902494-05:
      DOI: 10.1002/anie.201801132
       
  • N-Functionalized Ferrocenes. Subvalent Group XIV Element Chlorides and an
           tButyl Lithium-Induced C─C Bond Cleavage Under Mild Conditions
    • Authors: Bastian Nayyar; Hazem Alnasr, Wolf Hiller, Klaus Jurkschat
      Abstract: The ferrocene derivative η5-CpFeη5-C5H3-1-(ArNCH)-2-(CH2NMe2) (1, Ar = 2,6-iPr2C6H3)) reacts diastereoselectively with LiR under carbolithiation and subsequent hydrolysis to give η5-CpFeη5-C5H3-1-(ArHNCHR)-2-(CH2NMe2) (3, R = tBu; 4, R = Ph; 5, R = Me) in high yields. For R = tBu the organolithium derivative η5-CpFeη5-C5H3-1-(ArLiNCHR)-2-(CH2NMe2) (2) was isolated. Compound 2 reacts with GeCl2∙dioxane and SnCl2, respectively, giving the metallylene amide chlorides η5-CpFeη5-C5H3-1-(ArMNCHtBu)-2-(CH2NMe2) (6, M = GeCl; 7, M = SnCl) containing each three stereogenic centres. The potential of 7 as ligand in transition metal chemistry is demonstrated by formation of its complex η5-CpFeη5-C5H3-1-(ArMNCHtBu)-2-(CH2NMe2) [9, M = Sn(Cl)W(CO)5]. Treatment at room temperature of 3 with tert-butyllithium causes an unprecedented carbon-carbon bond cleavage while under kinetic control lithiation at the Cp-3 position takes place allowing the isolation of η5-CpFeη5-C5H3-1-(ArHNCHtBu)-2-(CH2NMe2)-3-SiMe3 (10).
      PubDate: 2018-02-16T04:40:36.048346-05:
      DOI: 10.1002/anie.201800128
       
  • Imaging Nano–Bio Interactions in the Kidney: Toward a Better
           Understanding of Nanoparticle Clearance
    • Authors: Junqing Wang; Gang Liu
      Abstract: All clear! Highlighted is work aimed at a better understanding of nano–bio interactions for rational design of renal-clearable nanoparticles in diseased kidneys. Renal clearance of ultra-small gold nanoparticles (AuNPs) is not only dependent upon the Choi criteria but is also affected by the microphysiological structure of the glomerular barrier and the pathophysiological changes in the nephron.
      PubDate: 2018-02-16T04:03:05.102049-05:
      DOI: 10.1002/anie.201711705
       
  • Organometallic-Mediated Radical Polymerization of Vinylidene Fluoride
    • Authors: Sanjib Banerjee; Vincent Ladmiral, Antoine Debuigne, Christophe Detrembleur, Rinaldo Poli, Bruno Améduri
      Abstract: An unprecedented level of control for the radical polymerization of vinylidene fluoride (VDF), yielding well-defined PVDF (at least up to 14 500 g mol−1) with low dispersity (≤1.32), was achieved using organometallic-mediated radical polymerization (OMRP) with an organocobalt compound as initiator. The high chain-end fidelity was demonstrated by the synthesis of PVDF- and PVAc-containing di-and triblock copolymers. DFT calculations rationalize the efficient reactivation of both head and tail chain end dormant species.Head and tails above the rest: An organocobalt compound allows organometallic-mediated radical polymerization (OMRP) of vinylidene fluoride (VDF) yielding well-defined PVDF (at least up to 14 500 g mol−1) with low dispersity (≤1.32). The PVDF could be reactivated at both the head and tail chain ends, as evidenced by DFT calculations.
      PubDate: 2018-02-16T04:02:58.915514-05:
      DOI: 10.1002/anie.201712347
       
  • ADUC Prizes / Carl Duisberg Memorial Award for Bill Morandi / New Members
           of the Académie des Sciences / Max Delbrück Junior Prize for Sabrina
           Disch / Novartis Early Career Award
    • PubDate: 2018-02-16T04:02:25.312798-05:
      DOI: 10.1002/anie.201801006
       
  • A Versatile Ligand Platform for Palladium- and Nickel-Catalyzed Ethylene
           Copolymerization with Polar Monomers
    • Authors: Min Chen; Changle Chen
      Abstract: The ability to carry out transition-metal-catalyzed copolymerizations of olefins with polar monomers is a great challenge in the field of olefin polymerization. Palladium has been the dominant player in this field, while its low-cost nickel counterpart has only achieved very limited success. We report the synthesis and evaluation of a highly versatile platform based on diphosphazane monoxide ligands. Both palladium and nickel catalysts bearing these ligands mediate the copolymerization of ethylene with a number of fundamental polar monomers.Lay it on the line: A versatile ligand platform based on diphosphazane monoxide ligands was designed and evaluated. Both palladium and nickel catalysts bearing these ligands mediate the copolymerization of ethylene with a number of fundamental polar monomers.
      PubDate: 2018-02-16T04:01:29.093432-05:
      DOI: 10.1002/anie.201711753
       
  • Two Chiral Events in a Single C-H Activation Step: a route towards
           terphenyl ligands with two atropisomeric axes.
    • Authors: Françoise Colobert; Quentin Dherbassy, Jean-Pierre Djukic, Joanna Wencel-Delord
      Abstract: Herein we disclose the synthesis of original chiral scaffolds - ortho-orientated terphenyls presenting two atropisomeric Ar-Ar axes. These unusual structures are built up using the C-H activation approach and remarkably both chiral axes are controlled with excellent stereoselectivities in a single transformation. During the reaction, not only atroposelective functionalization of the biaryl precursor occurs imposing one chiral axis, but also an unprecedented atropo-stereoselective C-H arylation takes place generating the second chiral element. These functionalized enantiopure ortho-terphenyls present an original tridimensional structure and thus constitute a unique ground to build-up rapidly and efficiently a library of enantiopure mono- and bicoordinating ligands such as new S/N-Biax and diphosphine Biax-Phos ligands.
      PubDate: 2018-02-16T03:11:18.086603-05:
      DOI: 10.1002/anie.201801130
       
  • An Organic Mixed-Valence Ligand for Multistate Redox-Active Coordination
           Networks
    • Authors: Joo yeon Ha; Jin young Koo, Hiroyoshi Ohtsu, Yumi Yakiyama, Kimoon Kim, Daisuke Hashizume, Masaki Kawano
      Abstract: The multi-redox-active/multi-interactive ligand 5,5',8,8'-tetra(4-pyridyl)-2,2'-(1,4-phenylene)bis-1H-perimidine (H2TPP) was designed and synthesized. H2TPP exhibits four one-electron oxidation steps, and was subsequently used for the preparation of a multi-redox-active coordination network via a solid-liquid interface reaction using molten Cd2+ cations. The multiple redox states of H2TPP were confirmed spectroscopically by a stepwise four-electron oxidation. The spectroscopic analysis indicated that the mixed-valence states of the ligand are Class II on the UV-vis-NIR time scale and borderline Class II/Class III on the ESR time scale.
      PubDate: 2018-02-16T01:10:32.494843-05:
      DOI: 10.1002/anie.201713035
       
  • Synthesis of a Helical Bilayer Nanographene
    • Authors: Paul Jameson Evans; Jiangkun Ouyang, Ludovic Favereau, Jeanne Crassous, Israel Fernández, Josefina Perles Hernáez, Nazario Martin
      Abstract: A rigid, inherently chiral bilayer nanographene has been synthesized as both the racemate and enantioenriched M isomer (with an ee of 93%) in three steps from precedented helicenes. This folded nanographene is comprised of two hexa-peri-hexabenzocoronene layers fused to a [10]helicene, with an interlayer distance of 3.6Å as determined by X-ray crystallography. The rigidity of the helicene linker forces the layers to adopt a nearly-aligned AA-stacked conformation rarely observed in few-layer graphene. By combining the advantages of nanographenes and helicenes, we have constructed a bilayer system of 30 fused benzene rings that is also chiral, rigid, and remains soluble in common organic solvents. We present this as a molecular model system of bilayer graphene, with properties of interest in a variety of potential applications.
      PubDate: 2018-02-15T13:10:40.004038-05:
      DOI: 10.1002/anie.201800798
       
  • Ni-catalyzed Umpolung Arylation of Ambiphilic a-Bromo Boronic Esters
    • Authors: Ruben Martin; Shang-Zheng Sun
      Abstract: A Ni-catalyzed reductive arylation of ambiphilic a-bromo boronic esters with aryl halides is described. This platform provides an unrecognized opportunity to promote catalytic umpolung reactivity of ambiphilic reagents with aryl halides, thus unlocking a new cross-coupling strategy that complements existing technologies for the preparation of densely functionalized alkyl organometallic reagents from simple and accessible precursors
      PubDate: 2018-02-15T11:40:34.478784-05:
      DOI: 10.1002/anie.201712428
       
  • The Amyloid Polymorphism in the Protein Folding and Aggregation Energy
           Landscape
    • Authors: Raffaele Mezzenga; Jozef Adamcik
      Abstract: Protein folding (and misfolding) is of paramount importance to an extraordinary vast class of fields, spanning from biochemistry to biology, medicine, biophysics and statistical thermodynamics. The folding process involves a large number of steps and conformations in which the folding protein samples different thermodynamic states characterized by local minima and activation energies in between. The kinetically trapped on- or off-pathway intermediates identifying the relative minima are metastable folding intermediates towards the lowest absolute energy minima, which have been postulated to be the natively folded state for the regime in which the intramolecular interactions dominate, and the amyloid status for the regime where intermolecular interactions rule. This view, however, has largely neglected the rich polymorphism characterizing the various amyloid species. In this article, we review the protein folding energy landscape in view of recent findings identifying specific transition routes among different amyloid polymorphs. Observed transitions such as twisted ribboncrystal or helical ribbonnanotube or forbidden transitions such helical ribbon crystal, are discussed and precisely positioned within the protein folding and aggregation energy landscape. In particular, because these transitions occur without an unfolding/refolding process, the various energetic states can be navigated by relying on continuous mechanic concepts, which concur, together with experimental evidence, to identify amyloid crystals as the ground state of the protein folding and aggregation energy landscape.
      PubDate: 2018-02-15T11:26:39.793559-05:
      DOI: 10.1002/anie.201713416
       
  • Confinement effects on the benzene orientational structure
    • Authors: Marta Falkowska; Daniel T. Bowron, Haresh Manyar, Tristan G. A. Youngs, Christopher Hardacre
      Abstract: Liquids under confinement exhibit different properties compared with their corresponding bulk phases, for example miscibility, phase transitions, and diffusion. The underlying cause is the local ordering of molecules which is usually only studied using pure simulation methods. Herein, we derive experimentally the structure of benzene confined in MCM-41 using total neutron scattering measurements. The study reveals a layering of molecules across a pore, and four concentric cylindrical shells can be distinguished for a pore with the radius of 18 Å. The nanoscale confinement of the liquid has a major effect on the spatial and orientational correlations observed between the molecules, when compared with the structure of the bulk liquid. These differences are most marked for the molecules in the parallel configurations, and this suggests differences in chemical reactivity between the confined and bulk liquids.
      PubDate: 2018-02-15T09:40:29.529213-05:
      DOI: 10.1002/anie.201713115
       
  • Epoxides as Alkylating Reagents for the Catellani Reaction
    • Authors: Hong-Gang Cheng; Chenggui Wu, Han Chen, Ruiming Chen, Guangyin Qian, Zhi Geng, Qiang Wei, Yuanyuan Xia, Jingyang Zhang, Yuming Zhang, Qianghui Zhou
      Abstract: We report a cooperative catalytic system comprising a PdII complex, XPhos, and the potassium salt of 5-norbornene-2-carboxylic acid that enables the use of epoxides as alkylating reagents in the Catellani reaction, thereby expanding the existing paradigm of this powerful transformation. The potassium salt of inexpensive 5-norbornene-2-carboxylic acid acts as both mediator and base in the process. This mild, chemoselective, scalable, and atom-economical protocol is compatible with a wide variety of readily available functionalized aryl iodides and epoxides, as well as terminating olefins. The resulting products undergo facile oxa-Michael addition to furnish ubiquitous isochroman scaffolds.A little cooperation can go a long way: A cooperative catalytic system comprising a PdII/XPhos complex and the potassium salt of 5-norbornene-2-carboxylic acid, which serves dual roles as a mediator and a base, enabled the use of epoxides as alkylating reagents in the Catellani reaction (see scheme). The products could also undergo oxa-Michael addition to furnish valuable isochroman scaffolds.
      PubDate: 2018-02-15T09:27:42.499461-05:
      DOI: 10.1002/anie.201800573
       
  • Formation of NiCo2V2O8 Yolk–Double Shell Spheres with Enhanced
           Lithium Storage Properties
    • Authors: Yan Lu; Jianwei Nai, Xiong Wen (David) Lou
      Abstract: Complex nanostructures with multi-components and intricate architectures hold great potential in developing high-performance electrode materials for lithium-ion batteries (LIBs). Herein, we demonstrate a facile self-templating strategy for the synthesis of metal vanadate nanomaterials with complex chemical composition of NiCo2V2O8 and a unique yolk–double shell structure. Starting with the Ni-Co glycerate spheres, NiCo2V2O8 yolk–double shell spheres are synthesized through an anion-exchange reaction of Ni-Co glycerate templates with VO3− ions, followed by an annealing treatment. By virtue of compositional and structural advantages, these NiCo2V2O8 yolk–double shell spheres manifest outstanding lithium storage properties when evaluated as anodes for LIBs. Impressively, an extra-high reversible capacity of 1228 mAh g−1 can be retained after 500 cycles at a high current density of 1.0 Ag−1.Yolk–double shell NiCo2V2O8 spheres have been successfully synthesized through a facile self-templating approach using the ion-exchange reaction between Ni-Co glycerate spheres and NH4VO3 under reflux conditions, followed by a thermal treatment in air. The as-synthesized NiCo2V2O8 samples exhibit outstanding electrochemical properties when used as an anode material for lithium-ion batteries.
      PubDate: 2018-02-15T09:25:47.533963-05:
      DOI: 10.1002/anie.201800363
       
  • Total Synthesis of Astellatol
    • Authors: Nan Zhao; Shuqiang Yin, Shengling Xie, Hao Yan, Pan Ren, Gui Chen, Fang Chen, Jing Xu
      Abstract: A nearly-30-year-old unanswered synthetic puzzle, astellatol, has been solved in an enantiospecific manner. The highly congested pentacyclic skeleton of this rare sesterterpenoid, which possesses a unique bicyclo[4.1.1]octane motif, ten stereocenters, a cyclobutane that contains two quaternary centers, an exo-methylene group, and a sterically encumbered isopropyl trans-hydrindane motif, makes astellatol arguably one of the most challenging targets for sesterterpenoid synthesis. An intramolecular Pauson–Khand reaction was exploited to construct the right-hand side scaffold of this sesterterpenoid. An unprecedented reductive radical 1,6-addition, mediated by SmI2, forged the cyclobutane motif. Last, a strategic oxidation/reduction step provided not only the decisive solution for the remarkably challenging late-stage transformations, but also a highly valuable unravelling of the notorious issue of trans-hydrindane synthesis. Importantly, the synthesis of astellatol showcases a rapid, scalable strategy to access diverse complex isopropyl trans-hydrindane sesterterpenoids.Thirty something: Reported is the first enantiospecific total synthesis of astellatol, a rare pentacyclic-containing sesterterpenoid. A Pauson–Khand reaction was exploited to construct the right-hand side of astellatol. An unprecedented reductive radical 1,6-addition, mediated by SmI2, forged the unique bicyclo[4.1.1]octane motif. Last, a strategic oxidation/reduction step was key to the remarkably challenging late-stage synthesis of highly substituted trans-hydrindane.
      PubDate: 2018-02-15T09:21:07.312886-05:
      DOI: 10.1002/anie.201800167
       
  • Bioorthogonal Catalytic Activation of Platinum and Ruthenium Anticancer
           Complexes by FAD and Flavoproteins
    • Authors: Silvia Alonso-de Castro; Aitziber L. Cortajarena, Fernando López-Gallego, Luca Salassa
      Abstract: Recent advances in bioorthogonal catalysis promise to deliver new chemical tools for performing chemoselective transformations in complex biological environments. Herein, we report how FAD (flavin adenine dinucleotide), FMN (flavin mononucleotide), and four flavoproteins act as unconventional photocatalysts capable of converting PtIV and RuII complexes into potentially toxic PtII or RuII−OH2 species. In the presence of electron donors and low doses of visible light, the flavoproteins mini singlet oxygen generator (miniSOG) and NADH oxidase (NOX) catalytically activate PtIV prodrugs with bioorthogonal selectivity. In the presence of NADH, NOX catalyzes PtIV activation in the dark as well, indicating for the first time that flavoenzymes may contribute to initiating the activity of PtIV chemotherapeutic agents.Substrate, not catalyst: Flavins function as selective photocatalysts for the activation of metal-based prodrugs in biological environments. Unlike in typical catalysis, metal complexes are substrates and not catalysts in these reactions.
      PubDate: 2018-02-15T09:20:49.192594-05:
      DOI: 10.1002/anie.201800288
       
  • Base-Free Generation of Organic Electron Donors from Air-Stable Precursors
    • Authors: Guillaume Tintori; Pierre Nabokoff, Ruqaya Buhaibeh, David Bergé-Lefranc, Sébastien Redon, Julie Broggi, Patrice Vanelle
      Abstract: Organic electron donors (OEDs) are powerful reducing agents recognized for their potential in the reduction of challenging substrates and in original applications. Nonetheless, their low stability in atmospheric oxygen or over time complicates their manipulation and storage. To overcome these constraints and enhance OED practicality, new air- and moisture-stable aminopyridinium carboxylate and carbonate precursors were synthesized and thermally activated to generate the potent electron donor in situ. Carboxylate adducts proved to be excellent latent OED systems, enabling the facile and efficient reduction of challenging substrates. Their reduction properties were correlated to their structural characteristics by thermogravimetric and spectroscopic analysis.To enhance the practicality of organic electron donors (OEDs), new air- and moisture-stable carboxylate and carbonate precursors were synthesized and thermally activated to generate potent electron donors in situ. Carboxylate adducts proved to be excellent latent OED systems, enabling the efficient reduction of challenging substrates (ET=electron transfer).
      PubDate: 2018-02-15T09:15:59.734993-05:
      DOI: 10.1002/anie.201713079
       
  • Polyvalent Display of Biomolecules on Live Cells
    • Authors: Peng Shi; Nan Zhao, Jinping Lai, James Coyne, Erin R. Gaddes, Yong Wang
      Abstract: Surface display of biomolecules on live cells offers new opportunities to treat human diseases and perform basic studies. Existing methods are primarily focused on monovalent functionalization, that is, the display of single biomolecules across the cell surface. Here we show that the surface of live cells can be functionalized to display polyvalent biomolecular structures through two-step reactions under physiological conditions. This polyvalent functionalization enables the cell surface to recognize the microenvironment one order of magnitude more effectively than with monovalent functionalization. Thus, polyvalent display of biomolecules on live cells holds great potential for various biological and biomedical applications.The more the merrier: Biomolecules on live cells play essential roles in determining how cells recognize the environment. The surface of live cells can be functionalized to display polyvalent biomolecular structures for enhanced molecular recognition compared to monovalent functionalization.
      PubDate: 2018-02-15T09:15:52.498033-05:
      DOI: 10.1002/anie.201712596
       
  • Kinetic Resolution of sec-Thiols by Enantioselective Oxidation with
           Rationally Engineered 5-(Hydroxymethyl)furfural Oxidase
    • Authors: Mathias Pickl; Alexander Swoboda, Elvira Romero, Christoph K. Winkler, Claudia Binda, Andrea Mattevi, Kurt Faber, Marco W. Fraaije
      Abstract: Various flavoprotein oxidases were recently shown to oxidize primary thiols. Herein, this reactivity is extended to sec-thiols by using structure-guided engineering of 5-(hydroxymethyl)furfural oxidase (HMFO). The variants obtained were employed for the oxidative kinetic resolution of racemic sec-thiols, thus yielding the corresponding thioketones and nonreacted R-configured thiols with excellent enantioselectivities (E≥200). The engineering strategy applied went beyond the classic approach of replacing bulky amino acid residues with smaller ones, as the active site was additionally enlarged by a newly introduced Thr residue. This residue established a hydrogen-bonding interaction with the substrates, as verified in the crystal structure of the variant. These strategies unlocked HMFO variants for the enantioselective oxidation of a range of sec-thiols.Engineered to fit: Rationally designed variants of 5-(hydroxymethyl)furfural (HMF) oxidase catalyze the enantioselective oxidation of 1-phenylethanethiols, thus achieving their kinetic resolution with unprecedented selectivities. The crystal structure of one of the variants explains this unique finding.
      PubDate: 2018-02-15T09:10:28.55453-05:0
      DOI: 10.1002/anie.201713189
       
  • Catalytic Gas-Phase Production of Lactide from Renewable Alkyl Lactates
    • Authors: Rik De Clercq; Michiel Dusselier, Ekaterina Makshina, Bert F. Sels
      Abstract: A new route to lactide, which is a key building block of the bioplastic polylactic acid, is proposed involving a continuous catalytic gas-phase transesterification of renewable alkyl lactates in a scalable fixed-bed setup. Supported TiO2/SiO2 catalysts are highly selective to lactide, with only minimal lactide racemization. The solvent-free process allows for easy product separation and recycling of unconverted alkyl lactates and recyclable lactyl intermediates. The catalytic activity of TiO2/SiO2 catalysts was strongly correlated to their optical properties by DR UV/Vis spectroscopy. Catalysts with high band-gap energy of the supported TiO2 phase, indicative of a high surface spreading of isolated Ti centers, show the highest turnover frequency per Ti site.Closing the ring: An efficient process is described for the synthesis of lactide—a cyclic building block of bioplastics—which involves gas-phase transesterification of alkyl lactates. Supported TiO2/SiO2 catalysts exhibit high selectivity to lactide. Catalytic activity correlates with band-gap energy and increases strongly upon reduction of Ti-polymerization.
      PubDate: 2018-02-15T09:06:06.305313-05:
      DOI: 10.1002/anie.201711446
       
  • Ge14Br8(PEt3)4: A Subhalide Cluster of Germanium - First Step into a Novel
           Field in Germanium Chemistry
    • Authors: Andreas Bernd Schnepf; Claudio Schrenk, Tanja Kunz
      Abstract: Heating a metastable solution of Ge(I)Br to room temperature leads to the first structurally characterized metalloid subhalide cluster Ge14Br8(PEt3)4 (1). Furthermore 1 can be seen as the first isolated binary halide cluster on the way from Ge(I)Br to elemental germanium, giving insight into the complex reaction mechanism of its disproportionation reaction. Quantum chemical calculations further indicate that within 1 a classical bonding situation is realized and that the last step of the formation of 1 might include the trapping of GeBr2 units.
      PubDate: 2018-02-15T07:41:13.39469-05:0
      DOI: 10.1002/anie.201712247
       
  • Coumarin Photocages Modified with an Electron-Rich Styryl Moiety at the
           3-Position: Long Wavelength Excitation, Rapid Photolysis and
           Photobleaching
    • Authors: Linyong Zhu; Qiuning Lin, Lipeng Yang, Zhiqiang Wang, Yujie Hua, Dasheng Zhang, Bingkun Bao, Chunyan Bao, Xueqing Gong
      Abstract: A new class of coumarin photocages modified with an electron-rich styryl moiety at the 3-position was constructed. The large π-conjugated structure and stabilization of the carbocation intermediates by electron-donors endowed the new photocages excellent long wavelength absorption, large two-photon absorption cross-sections and high uncaging quantum yields. Moreover, the new photocages displayed unique photobleaching property after photocleavage as a result of the intramolecular cyclization rearrangement of carbocation intermediate to form five-membered ring byproducts and block the styryl conjugation at the 3-position. These superior properties of the new photocages are extremely beneficial for high concentration samples and thick specimens, thus extending the application of photocages in many fields.
      PubDate: 2018-02-15T06:11:19.074787-05:
      DOI: 10.1002/anie.201800713
       
  • Co-assembly of Polyoxometalates and Zwitterionic Amphiphiles into
           Supramolecular Hydrogels: From Crystalline Fibrillar to Amorphous Micellar
           Networks
    • Authors: Aoli Wu; Xinpei Gao, Panpan Sun, Fei Lu, Liqiang Zheng
      Abstract: Gelation mechanism is of utmost importance to the rational design of supramolecular hydrogelators. Although both kinetic and thermodynamic controlling self-assembly processes have been widely studied in hydrogels, the evolution relationship between crystalline and amorphous gel networks still remains ambiguous. Herein, a gelation transformation from kinetic to thermodynamic process was achieved by balancing the rigidity and flexibility of the inorganic-organic co-assemblies. And for the first time, the transition morphologies between crystalline and amorphous hydrogel networks were evidenced as ordered wormlike micelles. Given the versatile applications of hydrogels in biological systems and material science, we expect our findings may highlight the potential of inorganic-organic binary supramolecular hydrogelators and fill in the blank between kinetic and thermodynamic controlling gelation processes.
      PubDate: 2018-02-15T05:35:33.606768-05:
      DOI: 10.1002/anie.201800939
       
  • A Sulfoxide-Based Isobaric Labelling Reagent for Accurate Quantitative
           Mass Spectrometry
    • Authors: Michael Stadlmeier; Jana Bogena, Miriam Wallner, Martin Wühr, Thomas Carell
      Abstract: Modern proteomics requires reagents for exact quantification of peptides in complex mixtures. Peptide labelling is most typically achieved with isobaric tags that consist of a balancer and a reporter part that separate in the gas phase. An ingenious distribution of stable isotopes provides multiple reagents with identical molecular weight but a different mass of the reporter groups, allowing relative quantification of multiple samples in one measurement. Here we report a new isobaric labelling reagent, where the balancer and the reporter are linked by a sulfoxide group, which, based on the sulfoxide pyrolysis, leads to easy and asymmetric cleavage at low fragmentation energy. The fragmentation of our new design is significantly improved, yielding more intense complementary ion signals, allowing complementary ion cluster analysis as well.Tagged for success: A new reagent (SulfOxide Tag) for quantitative proteomics was developed that shows easier cleavage and hence higher reporter- and complementary-ion intensity.
      PubDate: 2018-02-15T05:00:36.305909-05:
      DOI: 10.1002/anie.201708867
       
  • Synergistic Photoredox and Organocatalysis for Inverse Hydroboration of
           Imines
    • Authors: Jin Xie
      Abstract: The first catalytic inverse hydroboration of imines with N-heterocyclic carbene boranes has been realized by means of cooperative organocatalysis and photocatalysis. This catalytic combination brings a promising platform to promote NHC-boryl radical chemistry under sustainable and radical initiator free conditions. The highly important functional group compatibility and possible application in late-stage hydroboration represent an important step-forward to an enhanced -amino organoboron lead library.
      PubDate: 2018-02-15T04:36:37.268063-05:
      DOI: 10.1002/anie.201800421
       
  • Stereodivergent Evolution of Artificial Enzymes for the Michael Reaction
    • Authors: Xavier Garrabou Pi; Duncan Stuart Macdonald, Basile I. M. Wicky, Donald Hilvert
      Abstract: Enzymes are valuable biocatalysts for asymmetric synthesis due to their exacting stereocontrol. Changing the selectivity of an existing catalyst for new applications is, however, challenging. Here we show that, in contrast, the stereoselectivity of an artificial enzyme created by design and directed evolution is readily tunable. We engineered a promiscuous artificial retro-aldolase into four stereocomplementary catalysts for the Michael addition of a tertiary carbanion to an unsaturated ketone. Notably, this selectivity is also preserved with alternative Michael nucleophiles. Complete stereodiversification of other designer enzymes should similarly be possible by extension of these approaches.
      PubDate: 2018-02-15T03:40:25.709544-05:
      DOI: 10.1002/anie.201712554
       
  • Rh-Catalyzed Arylation of Cyclopropenes Based on Asymmetric Directed
           Functionalization of Three-Membered Carbocycles
    • Authors: Ilan Marek; Longyang Dian
      Abstract: A large variety of highly diastereo- and enantiomerically enriched arylcyclopropanes is obtained through the asymmetric Rh-catalyzed arylation reaction of achiral non-functionalized cyclopropene derivatives with commercially available aryl boronic acids and (R,S)-Josiphos
      PubDate: 2018-02-15T03:11:21.530398-05:
      DOI: 10.1002/anie.201713324
       
  • Stabilizing and Organizing Bi3Cu4 and Bi7Cu12 Nanoclusters in
           Two-Dimensional Metal-Organic Networks
    • Authors: Linghao Yan; Bowen Xia, Qiushi Zhang, Guowen Kuang, Hu Xu, Jun Liu, Pei Nian Liu, Nian Lin
      Abstract: Multinuclear heterometallic nanoclusters with controllable stoichiometry and structure are anticipated to possess promising catalytic, magnetic, and optical properties. Here we demonstrate that heterometallic nanoclusters with precise stoichiometry of Bi3Cu4 and Bi7Cu12 can be stabilized in the scaffold of two-dimensional metal-organic networks on a Cu(111) surface through on-surface metallosupramolecular self-assembly processes. The atomic structures of the nanoclusters were resolved using scanning tunnelling microscopy and density functional theory calculations. The nanoclusters feature highly symmetric planar hexagonal shapes and core-shell charge modulation. The clusters are arranged as triangular lattices with a periodicity that can be tuned by choosing molecules of different size. This work shows that on-surface metallosupramolecular self-assembly creates unique possibilities for the design and synthesis of multinuclear heterometallic nanoclusters.
      PubDate: 2018-02-15T03:10:25.723091-05:
      DOI: 10.1002/anie.201800906
       
  • Entropy-Driven Diastereoselectivity Improvement in the Paternò-Büchi
           Reaction of 1-Naphthylarylethenes with Chiral Cyanobenzoate through Remote
           Alkylation
    • Authors: Keisuke Nagasaki; Yoshihisa Inoue, Tadashi Mori
      Abstract: Precisely stereocontrolling photocycloaddition is still a significant challenge, due to mechanistic complexity and highly reactive and short-lived nature of intermediates. Attempts have hitherto been made through structural modifications, mostly by introducing steric conflicts, to increase difference in enthalpic barrier. Here, we show that entropy plays a crucial role in manipulating diastereoselectivity of Paternò-Büchi reaction. A remote meta-alkylation of donor caused nominal changes in photophysical properties as well as exciplexes derived therefrom. Nevertheless, diastereomeric excess of oxetane produced was greatly improved by ca. 40%. This enhancement without accompanying any significant photophysical property changes is difficult to rationalize by conventional enthalpic control concept based on repulsive steric and/or attractive intermolecular interactions as well as electronic perturbations. Differential activation parameters and compensatory enthalpy-entropy relationship revealed that the diastereoselectivity enhancement is not simply enthalpic but also entropic in origin.
      PubDate: 2018-02-14T21:41:00.600906-05:
      DOI: 10.1002/anie.201801330
       
  • The Solution of the Puzzle of Smectic-Q: The Phase Structure and the
           Origin of Spontaneous Chirality
    • Authors: Huanjun Lu; Xiangbing Zeng, Goran Ungar, Christian Dressel, Carsten Tschierske
      Abstract: Liquid crystals (LC) present a wide diversity of structures, offering many opportunities for their application in nanotechnology. However, for 35 years the structure of one particular LC phase, the Smectic-Q phase, withstood numerous attempts to solve it. At last the code has been cracked. In their Communication (
      DOI : 10.1002/anie.201712812), X. B. Zeng, G. Ungar, C. Tschierske et al. show it to be a mind-boggling array of orthogonal helical columns, homochiral even without molecular chirality.
      PubDate: 2018-02-14T08:31:02.787098-05:
       
  • Identification of Tumor Initiating Cells with a Small-Molecule Fluorescent
           Probe by Using Vimentin as a Biomarker
    • Authors: Yong-An Lee; Jong-Jin Kim, Jungyeol Lee, Jia Hui Jane Lee, Srikanta Sahu, Haw-Young Kwon, Sung-Jin Park, Se-Young Jang, Jun-Seok Lee, Zhenxun Wang, Wai Leong Tam, Bing Lim, Nam-Young Kang, Young-Tae Chang
      Abstract: Tumor initiating cells (TICs) have been implicated in clinical relapse and metastasis of a variety of epithelial cancers, including lung cancer. While efforts toward the development of specific probes for TIC detection and targeting are ongoing, a universal TIC probe has yet to be developed. We report the first TIC-specific fluorescent chemical probe, TiY, with identification of the molecular target as vimentin, a marker for epithelial-to-mesenchymal transition (EMT). TiY selectively stains TICs over differentiated tumor cells or normal cells, and facilitates the visualization and enrichment of functionally active TICs from patient tumors. At high concentration, TiY also shows anti-TIC activity with low toxicity to non-TICs. With the unexplored target vimentin, TiY shows potential as a first universal probe for TIC detection in different cancers.What makes tumors TIC' The first tumor initiating cell (TIC)-selective probe, TiY, was developed, with vimentin as the molecular target. TiY facilitates the visualization and enrichment of functionally active TICs from patient-derived tumors and all of the tested cancer cell lines. Furthermore, TiY showed anti-TIC activity at high concentrations.
      PubDate: 2018-02-14T08:31:00.326171-05:
      DOI: 10.1002/anie.201712920
       
  • Nucleophile Promiscuity of Engineered Class II Pyruvate Aldolase
           YfaU from E. Coli
    • Authors: Karel Hernández; Jesús Joglar, Jordi Bujons, Teodor Parella, Pere Clapés
      Abstract: Pyruvate-dependent aldolases exhibit a stringent selectivity for pyruvate, limiting application of their synthetic potential, which is a drawback shared with other existing aldolases. Structure-guided rational protein engineering rendered a 2-keto-3-deoxy-l-rhamnonate aldolase variant, fused with a maltose-binding protein (MBP-YfaU W23V/L216A), capable of efficiently converting larger pyruvate analogues, for example, those with linear and branched aliphatic chains, in aldol addition reactions. Combination of these nucleophiles with N-Cbz-alaninal (Cbz=benzyloxycarbonyl) and N-Cbz-prolinal electrophiles gave access to chiral building blocks, for example, derivatives of (2S,3S,4R)-4-amino-3-hydroxy-2-methylpentanoic acid (68 %, d.r. 90:10) and the enantiomer of dolaproine (33 %, d.r. 94:6) as well as a collection of unprecedented α-amino acid derivatives of the proline and pyrrolizidine type. Conversions varied between 6–93 % and diastereomeric ratios from 50:50 to 95:5 depending on the nucleophilic and electrophilic components.Diverse and easy: Structure-guided rational protein engineering resulted in a 2-keto-3-deoxy-l-rhamnonate aldolase variant fused with a maltose-binding protein (MBP-YfaU W23V/L216A), which can provide straightforward access to chiral building blocks and a series of unprecedented proline and pyrrolizidine α-amino acid derivatives.
      PubDate: 2018-02-14T08:30:51.337011-05:
      DOI: 10.1002/anie.201711289
       
  • Transition-Metal-Catalyzed Selective Functionalization of C(sp3)−H
           Bonds in Natural Products
    • Authors: Rashad R. Karimov; John F. Hartwig
      Abstract: Direct functionalization of natural products is important for studying the structure–activity and structure–property relationships of these molecules. Recent advances in the transition-metal-catalyzed functionalization of C(sp3)−H bonds, the most abundant yet inert bonds in natural products, have allowed natural product derivatives to be created selectively. Strategies to achieve such transformation are reviewed.Direct derivatization: Direct functionalization of natural products is important for studying their structure–activity and structure–property relationships. Recent advances in the transition-metal-catalyzed functionalization of C(sp3)−H bonds have shown that natural product derivatives can be selectively produced. Strategies for achieving such transformations are discussed.
      PubDate: 2018-02-14T08:30:40.290795-05:
      DOI: 10.1002/anie.201710330
       
  • CO2-Triggered Switchable Hydrophilicity of a Heterogeneous Conjugated
           Polymer Photocatalyst for Enhanced Catalytic Activity in Water
    • Authors: Jeehye Byun; Wei Huang, Di Wang, Run Li, Kai A. I. Zhang
      Abstract: Water compatibility for heterogeneous photocatalysts has been pursued for energy and environmental applications. However, there exists a trade-off between hydrophilicity and recyclability of the photocatalyst. Herein, we report a conjugated polymer photocatalyst with tertiary amine terminals that reversibly binds CO2 in water, thereby generating switchable hydrophilicity. The CO2-assisted hydrophilicity boosted the photocatalytic efficiency in aqueous medium with minimum dosage. When CO2 was desorbed, the photocatalyst could be simply regenerated from reaction media, facilitating the repeated use of photocatalyst. Hydrophilicity/hydrophobicity control of the polymer photocatalyst was successfully showcased through a variety of organic photoredox reactions under visible-light irradiation in water.Wet wet wet: A tertiary amine-tethered conjugated polymer photocatalyst was designed to exhibit switchable hydrophilicity upon CO2/N2 exchange. The reversible hydrophilicity of the heterogeneous polymer photocatalyst enhances catalytic efficiency and recyclability for organic photoredox reactions in water.
      PubDate: 2018-02-14T08:30:34.323305-05:
      DOI: 10.1002/anie.201711773
       
  • Synthesis of Sub-2 nm Fe-Doped NiSe2 Nanowires and Their Surface Confined
           Oxidation for Oxygen Evolution Catalysis
    • Authors: Shu-Hong Yu; Chao Gu, Shaojin Hu, Xusheng Zheng, Min-Rui Gao, Ya-Rong Zheng, Lei Shi, Qiang Gao, Xiao Zheng, Wangsheng Chu, Hong-Bin Yao, Junfa Zhu
      Abstract: Ultrathin nanostructures are attractive for diverse applications owing to their unique properties compared to their bulks. Transition metal chalcogenides are promising electrocatalysts, yet there remains difficult to make ultrathin structures (sub-2 nm), and the realization of their chemical doping is even more challenging. Here we describe a soft template mediated colloidal synthesis of Fe-doped NiSe2 ultrathin nanowires (UNWs) with diameter down to 1.7 nm. The synergistic interplay between oleylamine and 1-dodecanethiol is crucial to yield these UNWs. The in-situ formed amorphous hydroxide layers that confined on the surface of the ultrathin scaffolds enable efficient oxygen evolution electrocatalysis. The resultant UNW derivatives exhibit a very low overpotential of 268 mV at 10 mA cm-2 in 0.1 M KOH, as well as remarkable long-term stability, representing one of the most efficient noble-metal-free catalysts.
      PubDate: 2018-02-14T07:41:52.107832-05:
      DOI: 10.1002/anie.201800883
       
  • Me3Si−SiMe2[o-CON(i-Pr)2-C6H4]: A New Unsymmetrical Disilane Reagent for
           Regio- and Stereoselective Bis-silylation of Alkynes
    • Authors: Zhen Lei Song; Peihong Xiao, Yanjun Cao, Yingying Gui, Lu Gao
      Abstract: The air-stable unsymmetrical disilane Me3Si−SiMe2[o-CON(i-Pr)2C6H4] has been developed for bis-silylation of alkynes. This reagent tolerates a range of functional groups, providing Z-vinyl disilanes in high yields. The phenyl ring-tethered amide group is proposed to direct oxidative addition of Pd(0) into the Si-Si bond, that might facilitate formation of a six-membered Pd cycle, leading to the observed good to excellent regioselectivity.
      PubDate: 2018-02-14T07:40:57.772557-05:
      DOI: 10.1002/anie.201800513
       
  • Electrolyte additives for lithium metal anodes and rechargeable lithium
           metal batteries: progresses and perspectives
    • Authors: Heng Zhang; Gebrekidan Gebresilassie Eshetu, Xabier Judez, Chunmei Li, Lide M. Rodriguez-Martínez, Michel Armand
      Abstract: Lithium metal (Li°) - based rechargeable batteries (LMBs), such as Li° anode vs. intercalation and/or conversion type cathode batteries, lithium-sulphur (Li-S), and lithium-oxygen (O2)/air (Li-O2/air) are becoming increasingly important for electrifying the modern transportation system, enabling sustainable mobility in the near future. Though some rechargeable LMBs batteries (e.g., Li°/LiFePO4 batteries from Bolloré Bluecar®, Li-S batteries from OXIS Energy and Sion Power) are already commercially viable in niche applications, their large-scale deployment is still hampered due to the existence of a number of formidable challenges, including lithium dendrite growth, electrolyte instability towards high voltage intercalation type cathode, poor electronic and ionic conductivities of sulphur (S8) and O2, as well as their corresponding reduction products (e.g., Li2S and Li2O), dissolution and shuttling of polysulphide (PS) intermediates etc. This ultimately results in short cycle life, low coulombic/energy efficiency, poor safety, and a high self-discharge rate. Among other mitigating strategies, the use of electrolyte additives is considered as one of the most economical, and effective approach for circumventing these dilemmas. Set out to offer an in-depth insight into the rapidly growing research on the account of electrolyte additives for rechargeable LMBs, this review presents an overview of the various functional additives, that are being applied in Li-anode/intercalation cathode-based, Li-S and Li-O2 batteries. This review is believed to assess the status quo of the research and thereby arouse new thoughts and opportunities, opening new avenues for the practical realization of these appealing devices.
      PubDate: 2018-02-14T07:12:24.807315-05:
      DOI: 10.1002/anie.201712702
       
  • The [U2F12]2− Anion of Sr[U2F12]
    • Authors: Benjamin Scheibe; Clemens Pietzonka, Otto Mustonen, Maarit Karppinen, Antti J. Karttunen, Mihail Atanasov, Frank Neese, Matthias Conrad, Florian Kraus
      Abstract: The D2h-symmetric dinuclear complex anion [U2F12]2− of pastel green Sr[U2F12] shows a hitherto unknown structural feature: The coordination polyhedra around the U atoms are edge-linked monocapped trigonal prisms, the UV atoms are therefore seven-coordinated. This leads to a U–U distance of 3.8913(6) Å. A weak UV–UV interaction is observed for the dinuclear [U2F12]2− complex and described by the antiferromagnetic exchange Jexp of circa −29.9 cm−1. The crystalline compound can be easily prepared from SrF2 and β-UF5 in anhydrous hydrogen fluoride (aHF) at room temperature. It was studied by means of single crystal X-ray diffraction, IR, Raman and UV/VIS spectroscopy, magnetic measurements, and by molecular as well as by solid-state quantum chemical calculations.Stuck on U: Sr[U2F12] is synthesized. It contains the D2h symmetric [U2F12]2− anion, which is the first example of a dinuclear fluoridouranate(V) complex. The spectroscopic and magnetic properties could be reproduced by quantum chemical calculations. An antiferromagnetic coupling of the UV atoms is observed.
      PubDate: 2018-02-14T06:10:50.34495-05:0
      DOI: 10.1002/anie.201800743
       
  • Dynamic Interconversion between Boroxine Cages Based on Pyridine Ligation
    • Authors: Kosuke Ono; Shunsuke Shimo, Kohei Takahashi, Nobuhiro Yasuda, Hidehiro Uekusa, Nobuharu Iwasawa
      Abstract: Dynamic interconversion between large covalent organic cages was achieved simply by heating or acid/base treatment. A mixture of the boroxine cages 12-mer and 15-mer was cleanly converted into a pyridine adduct of the 9-mer boroxine cage upon treatment with pyridine, and the geometry of N-coordinated boron atoms changed from trigonal to tetrahedral. The reverse reaction was achieved by heating or acid treatment. In this process, the larger boroxine cages 12-mer and 15-mer were found to be entropically favored owing to the release of free pyridine molecules from 9-mer⋅6 Py.A mixture of the boroxine cages 12-mer and 15-mer was cleanly converted into a pyridine adduct of boroxine cage 9-mer upon treatment with pyridine. The reverse reaction was achieved by heating or acid treatment. The larger boroxine cages 12-mer and 15-mer were entropically favored owing to the release of free pyridine molecules from 9-mer⋅6 Py.
      PubDate: 2018-02-14T06:01:41.064789-05:
      DOI: 10.1002/anie.201713221
       
  • Rhodium(I)-Catalyzed Cycloisomerization of Homopropargylallene-Alkynes
           through C(sp3)−C(sp) Bond Activation
    • Authors: Yasuaki Kawaguchi; Kenya Yabushita, Chisato Mukai
      Abstract: Upon exposure to a catalytic amount of [RhCl(CO)2]2 in 1,4-dioxane, homopropargylallene-alkynes underwent a novel cycloisomerization accompanied by the migration of the alkyne moiety of the homopropargyl functional group to produce six/five/five tricyclic compounds in good yields. A plausible mechanism was proposed on the basis of an experiment with 13C-labeled substrate. The resulting tricyclic derivatives were further converted into the corresponding bicyclo[3.3.0] skeletons with vicinal cis dihydroxy groups.Treatment of homopropargylallene-alkynes with [RhCl(CO)2]2 effected C(sp3)−C(sp) bond fission and migration, resulting in the efficient construction of tricyclic skeletons with a triene motif. Oxidation of the latter produced vicinal cis diols in a stereo- and regioselective fashion.
      PubDate: 2018-02-14T06:01:26.98853-05:0
      DOI: 10.1002/anie.201713096
       
  • The Enantioselective Total Synthesis of Bisquinolizidine Alkaloids: A
           Modular “Inside-Out” Approach
    • Authors: Dagmar Scharnagel; Jessica Goller, Nicklas Deibl, Wolfgang Milius, Matthias Breuning
      Abstract: Bisquinolizidine alkaloids are characterized by a chiral bispidine core (3,7-diazabicyclo[3.3.1]nonane) to which combinations of an α,N-fused 2-pyridone, an endo- or exo-α,N-annulated piperidin(on)e, and an exo-allyl substituent are attached. We developed a modular “inside-out” approach that permits access to most members of this class. Its applicability was proven in the asymmetric synthesis of 21 natural bisquinolizidine alkaloids, among them more than ten first enantioselective total syntheses. Key steps are the first successful preparation of both enantiomers of C2-symmetric 2,6-dioxobispidine by desymmetrization of a 2,4,6,8-tetraoxo precursor, the construction of the α,N-fused 2-pyridone by using an enamine-bromoacrylic acid strategy, and the installation of endo- or, optionally, exo-annulated piperidin(on)es.All in one sweep: A diversity-driven, modular “inside-out” approach to natural bisquinolizidine alkaloids was developed. Its versatility was confirmed in the enantioselective total synthesis of 21 alkaloids of this class. Key steps are a desymmetrization, permitting access to C2-symmetric 2,6-dioxobispidine in both enantiomeric forms, and the annulation of 2-pyridone and endo- or exo-fused piperidines to this chiral core building block.
      PubDate: 2018-02-12T03:11:00.495587-05:
      DOI: 10.1002/anie.201712852
       
  • Carbohydrate-Responsive Surface Adhesion based on the Dynamic Covalent
           Chemistry of Phenylboronic Acid- and Catechol-Containing Polymer Brushes
    • Authors: Sebastian Lamping; Tobias Otremba, Bart Jan Ravoo
      Abstract: A glue, based on dynamic covalent chemistry, with a strong adhesion (2.38 kg cm−2), water resistance and carbohydrate responsive reversibility is presented. Using surface initiated atom transfer radical polymerization (SI-ATRP), glass and silicon surfaces were coated with copolymers functionalized with phenylboronic acids and catechols. In combination with microcontact printing (μCP) these polymer brushes give access to a carbohydrate responsive “supramolecular Velcro”.Glue and release: A supramolecular glue is prepared through the combination of atom-transfer radical polymerization and the dynamic covalent chemistry of phenyl boronic acids and catechols. The glue shows strong adhesion (2.38 kg cm−2), is water resistant, can be reused multiple times, and releases in the presence of a carbohydrate.
      PubDate: 2018-02-09T02:28:57.157338-05:
      DOI: 10.1002/anie.201711529
       
  • Cover Picture: The Enantioselective Total Synthesis of Bisquinolizidine
           Alkaloids: A Modular “Inside-Out” Approach (Angew. Chem. Int. Ed.
           9/2018)
    • Authors: Dagmar Scharnagel; Jessica Goller, Nicklas Deibl, Wolfgang Milius, Matthias Breuning
      Pages: 2261 - 2261
      Abstract: A modular “inside-out” approach to 21 natural bisquinolizidine alkaloids, among them more than ten first enantioselective total syntheses, is reported by M. Breuning et al. in their Communication on page 2432 ff. Key was the successful preparation of both enantiomers of C2-symmetric 2,6-dioxobispidine by desymmetrization and the successive α,N-annulation of a 2-pyridone and endo- or exo-fused piperidines to the chiral core building block.
      PubDate: 2018-02-05T09:56:30.039139-05:
      DOI: 10.1002/anie.201800930
       
  • Inside Cover: Dual Ligand-Enabled Nondirected C−H Olefination of Arenes
           (Angew. Chem. Int. Ed. 9/2018)
    • Authors: Hao Chen; Philipp Wedi, Tim Meyer, Ghazal Tavakoli, Manuel van Gemmeren
      Pages: 2262 - 2262
      Abstract: How many ligands does it take to change a bond' The oxidative C−H arylation of olefins (the Fujiwara–Moritani reaction) has been plagued by low efficiency and the need for excess amounts of valuable arene starting materials. In their Communication on page 2497, M. van Gemmeren and co-workers report a dual ligand strategy for optimizing the palladium catalyst for this reaction.
      PubDate: 2018-02-02T02:31:46.682436-05:
      DOI: 10.1002/anie.201800928
       
  • Graphical Abstract: Angew. Chem. Int. Ed. 9/2018
    • Pages: 2267 - 2278
      PubDate: 2018-02-19T05:32:55.879858-05:
      DOI: 10.1002/anie.201880911
       
  • Spotlights on our sister journals: Angew. Chem. Int. Ed. 9/2018
    • Pages: 2280 - 2283
      PubDate: 2018-02-19T05:33:01.447606-05:
      DOI: 10.1002/anie.201880913
       
  • Keiji Morokuma (1934–2017)
    • Authors: Qiang Cui; Stephan Irle, Jamal Musaev
      Pages: 2288 - 2289
      Abstract: Keiji Morokuma, William Henry Emerson Professor Emeritus of Emory University and Research Leader at the Fukui Institute for Fundamental Chemistry, Kyoto University, passed away at the age of 83 on November 27, 2017. Morokuma made numerous contributions to theoretical methodologies for the determination of reaction mechanisms and the understanding of intermolecular interactions.
      PubDate: 2018-02-02T02:36:31.44338-05:0
      DOI: 10.1002/anie.201800390
       
  • Hot Water Generates Crystalline Organic Materials
    • Authors: Miriam M. Unterlass
      Pages: 2292 - 2294
      Abstract: In hot water: Hydrothermal crystallization was recently used to transform amporphous polymer networks into amide-linked, stable covalent–organic frameworks. This work is highlighted in the context of the synthesis and especially crystallization of organic materials by using high-temperature water.
      PubDate: 2018-01-29T09:00:53.084177-05:
      DOI: 10.1002/anie.201713359
       
  • Increasing Catalyst Efficiency in C−H Activation Catalysis
    • Authors: Tobias Gensch; Michael J. James, Toryn Dalton, Frank Glorius
      Pages: 2296 - 2306
      Abstract: C−H activation reactions with high catalyst turnover numbers are still very rare in the literature and 10 mol % is a common catalyst loading in this field. We offer a representative overview of efficient C−H activation catalysis to highlight this neglected aspect of catalysis development and inspire future effort towards more efficient C−H activation. Examples ranging from palladium catalysis, Cp*RhIII- and Cp*CoIII-catalysis, the C−H borylation and silylation to methane C−H activation are presented. In these reactions, up to tens of thousands of catalyst turnovers have been observed.Go, catalyst, go! C−H activation reactions with high catalyst turnover numbers are still very rare in the literature and 10 mol % is a common catalyst loading in this field. A representative overview of efficient C−H activation catalysis is presented here to highlight this neglected aspect of catalysis development and inspire future effort towards more efficient C−H activation.
      PubDate: 2018-01-29T08:55:38.142026-05:
      DOI: 10.1002/anie.201710377
       
  • Lessons To Be Learned: The Molecular Basis of Kinase-Targeted Therapies
           and Drug Resistance in Non-Small Cell Lung Cancer
    • Authors: Jonas Lategahn; Marina Keul, Daniel Rauh
      Pages: 2307 - 2313
      Abstract: The treatment of non-small cell lung cancer (NSCLC) is currently experiencing a revolution. Over the last decade, the knowledge gained about the biochemical features of biomarkers and their predictive abilities has led to the development of targeted small-molecule inhibitors that present an alternative to harsh chemotherapy. The use of these new therapies has improved the quality of life and increased the survival of patients. The occurrence of inevitable drug resistance requires the constant development of precision medicine. The detailed understanding of the target biology and the search for innovative chemical approaches has encouraged investigations in this field. Herein, we review selected aspects of the molecular targets and present an overview of current topics and challenges in the rational development of small molecules to target NSCLC.An alternative to chemotherapy: The knowledge gained over the last decade about biomarkers and their predictive abilities has led to the development of precision medicine, which has improved the quality of life and increased the survival of patients. This Minireview highlights selected aspects of the molecular targets and presents an overview of current topics and challenges in targeting lung cancer (NSCLC).
      PubDate: 2018-01-12T05:51:44.324928-05:
      DOI: 10.1002/anie.201710398
       
  • Nanobodies: Chemical Functionalization Strategies and Intracellular
           Applications
    • Authors: Dominik Schumacher; Jonas Helma, Anselm F. L. Schneider, Heinrich Leonhardt, Christian P. R. Hackenberger
      Pages: 2314 - 2333
      Abstract: Nanobodies can be seen as next-generation tools for the recognition and modulation of antigens that are inaccessible to conventional antibodies. Due to their compact structure and high stability, nanobodies see frequent usage in basic research, and their chemical functionalization opens the way towards promising diagnostic and therapeutic applications. In this Review, central aspects of nanobody functionalization are presented, together with selected applications. While early conjugation strategies relied on the random modification of natural amino acids, more recent studies have focused on the site-specific attachment of functional moieties. Such techniques include chemoenzymatic approaches, expressed protein ligation, and amber suppression in combination with bioorthogonal modification strategies. Recent applications range from sophisticated imaging and mass spectrometry to the delivery of nanobodies into living cells for the visualization and manipulation of intracellular antigens.Nano-bodybuilding: Small antigen-recognizing proteins such as nanobodies are powerful tools in the life sciences. By taking advantage of chemical functionalization strategies, they can be used to visualize and manipulate intracellular targets.
      PubDate: 2018-01-26T03:31:43.994675-05:
      DOI: 10.1002/anie.201708459
       
  • Enantio- and Diastereoselective Cyclopropanation of 1-Alkenylboronates:
           Synthesis of 1-Boryl-2,3-Disubstituted Cyclopropanes
    • Authors: Javier Carreras; Ana Caballero, Pedro J. Pérez
      Pages: 2334 - 2338
      Abstract: A novel, highly enantio- and diastereoselective synthesis of 1-boryl-2,3-disubstituted cyclopropanes has been developed by means of the cyclopropanation of alkenylboronates with ethyl diazoacetate in the presence of catalytic amounts of a chiral copper(I) complex. The products can also be directly accessed from alkynes through an operationally simple, sequential hydroboration–cyclopropanation protocol. The resulting enantioenriched 1-boryl-2,3-disubstituted cyclopropanes are versatile synthetic intermediates that undergo further transformations at the carbon–boron bond.Useful handles: 1-Boryl-2,3-disubstituted cyclopropanes can be prepared in high yield and high diastereo- and enantioselectivity from alkenylboronates and ethyl diazoacetate in the presence of catalytic amounts of a copper(I) bisoxazoline species. The resulting cyclopropanes are versatile synthetic intermediates that can undergo further transformations at the carbon–boron bond.
      PubDate: 2018-01-02T08:40:59.478148-05:
      DOI: 10.1002/anie.201710415
       
  • Seeded Polymerization through the Interplay of Folding and Aggregation of
           an Amino-Acid-based Diamide
    • Authors: Soichiro Ogi; Kentaro Matsumoto, Shigehiro Yamaguchi
      Pages: 2339 - 2343
      Abstract: Amino acid based diamides are widely used as a substructure in supramolecular polymers and are also key components of polypeptides that help to understand protein folding. The interplay of folding and aggregation of a diamide was used to achieve seed-initiated supramolecular polymerization. For that purpose, a pyrene-substituted diamide was synthesized in which pyrene is used as a tracer to monitor the supramolecular polymerization. Thermodynamics and time-dependent studies revealed that the folding of the diamide moiety, via the formation of intramolecular hydrogen bonds, effectively prevents a spontaneous nucleation that leads to supramolecular polymerization. Under such out-of-equilibrium conditions, the addition of seeds successfully initiates the supramolecular polymerization. These results demonstrate the utility of such amino acid based diamides in programmable supramolecular polymerizations.Seeded polymerization: The hydrogen-bond-directed folding of a diamide group effectively prevents the spontaneous nucleation in the supramolecular polymerization of extended diamides. The seeded polymerization of pyrene, as an example of luminescent π-conjugated systems, was accomplished under out-of-equilibrium conditions in these coupled equilibria.
      PubDate: 2018-02-02T02:40:56.396822-05:
      DOI: 10.1002/anie.201712119
       
  • The Ideal Ionic Liquid Salt Bridge for the Direct Determination of Gibbs
           Energies of Transfer of Single Ions, Part I: The Concept
    • Authors: Valentin Radtke; Andreas Ermantraut, Daniel Himmel, Thorsten Koslowski, Ivo Leito, Ingo Krossing
      Pages: 2344 - 2347
      Abstract: Described is a procedure for the thermodynamically rigorous, experimental determination of the Gibbs energy of transfer of single ions between solvents. The method is based on potential difference measurements between two electrochemical half cells with different solvents connected by an ideal ionic liquid salt bridge (ILSB). Discussed are the specific requirements for the IL with regard to the procedure, thus ensuring that the liquid junction potentials (LJP) at both ends of the ILSB are mostly canceled. The remaining parts of the LJPs can be determined by separate electromotive force measurements. No extra-thermodynamic assumptions are necessary for this procedure. The accuracy of the measurements depends, amongst others, on the ideality of the IL used, as shown in our companion paper Part II.Extra-free! Can single-ion Gibbs transfer energies be determined without extra-thermodynamic assumptions' So far, the answer to this question has been no. A procedure based on straightforward potentiometric measurements is presented, thus making the answer a yes. Experimental proof for this claim is presented in the following Communication.
      PubDate: 2018-02-05T09:31:15.007432-05:
      DOI: 10.1002/anie.201707333
       
  • The Ideal Ionic Liquid Salt Bridge for Direct Determination of Gibbs
           Energies of Transfer of Single Ions, Part II: Evaluation of the Role of
           Ion Solvation and Ion Mobilities
    • Authors: Andreas Ermantraut; Valentin Radtke, Niklas Gebel, Daniel Himmel, Thorsten Koslowski, Ivo Leito, Ingo Krossing
      Pages: 2348 - 2352
      Abstract: An important intermediate goal to evaluate our concept for the assumption-free determination of single-ion Gibbs transfer energies ΔtrG°(i, S1S2) is presented. We executed the crucial steps a) and b) of the methodology, described in Part I of this treatise, exemplarily for Ag+ and Cl- with S1 being water and S2 being acetonitrile. The experiments showed that virtually all parts of the liquid junction potentials (LJPs) at both ends of a salt bridge cancel, if the bridge electrolyte is an “ideal” ionic liquid, that is, one with nearly identical diffusion of anion and cation. This ideality holds for [N2225]+[NTf2]- in the pure IL, but also in water and acetonitrile solution. Electromotive force measurements of solvation cells between S1 and S2 demonstrated Nernstian behavior for Ag+ concentration cells and constant like cell potentials for solutions with five tested Ag+ counterions.It′s ideal: A step towards measuring single-ion Gibbs transfer energies without extra-thermodynamic assumptions is described. In elementary open-circuit potential experiments utilizing an ideal ionic liquid salt bridge, virtually all parts of the liquid junction potential between different solvents could be circumvented for Ag+-based systems because of the nearly identical diffusion of [N2225]+ and [NTf2]− within the salt bridge and in the medium.
      PubDate: 2018-02-07T02:20:45.459314-05:
      DOI: 10.1002/anie.201707334
       
  • All-in-One Cellulose Nanocrystals for 3D Printing of Nanocomposite
           Hydrogels
    • Authors: Jieping Wang; Annalisa Chiappone, Ignazio Roppolo, Feng Shao, Erika Fantino, Massimo Lorusso, Daniel Rentsch, Kurt Dietliker, Candido Fabrizio Pirri, Hansjörg Grützmacher
      Pages: 2353 - 2356
      Abstract: Cellulose nanocrystals (CNCs) with>2000 photoactive groups on each can act as highly efficient initiators for radical polymerizations, cross-linkers, as well as covalently embedded nanofillers for nanocomposite hydrogels. This is achieved by a simple and reliable method for surface modification of CNCs with a photoactive bis(acyl)phosphane oxide derivative. Shape-persistent and free-standing 3D structured objects were printed with a mono-functional methacrylate, showing a superior swelling capacity and improved mechanical properties.All-rounder: Multifunctional cellulose nanocrystals were achieved by facile surface immobilization of photoactive groups. They serve as highly efficient visible light photoinitiators, cross-linkers and covalently embedded nanofillers for 3D printing of nanocomposite hydrogels, using a mono-functional methacrylate as monomer without any conventional cross-linkers.
      PubDate: 2018-01-16T10:02:02.879944-05:
      DOI: 10.1002/anie.201710951
       
  • Rapid Capture and Release of Nucleic Acids through a Reversible
           Photo-Cycloaddition Reaction in a Psoralen-Functionalized Hydrogel
    • Authors: Yizhe Zhang; Peggy P. Y. Chan, Amy E. Herr
      Pages: 2357 - 2361
      Abstract: Reversible immobilization of DNA and RNA is of great interest to researchers who seek to manipulate DNA or RNA in applications such as microarrays, DNA hydrogels, and gene therapeutics. However, there is no existing system that can rapidly capture and release intact nucleic acids. To meet this unmet need, we developed a functional hydrogel for rapid DNA/RNA capture and release based on the reversible photo-cycloaddition of psoralen and pyrimidines. The functional hydrogel can be easily fabricated through copolymerization of acrylamide with the synthesized allylated psoralen. The psoralen-functionalized hydrogel exhibits effective capture and release of nucleic acids spanning a wide range of lengths in a rapid fashion; over 90 % of the capture process is completed within 1 min, and circa 100 % of the release process is completed within 2 min. We observe no deleterious effects on the hybridization to the captured targets.Reversible capture scaffold for DNA and RNA: A polyacrylamide gel can be modified through copolymerization of acrylamide with allylated psoralen to form an efficient DNA/RNA capture scaffold. Reversible photo-cycloaddition of psoralen and pyrimidine allows DNA/RNA capture in 1 min and release in 2 min under UV irradiation. The capture and release applies to a wide range of DNA/RNA target lengths and is compatible with hybridization.
      PubDate: 2018-01-24T04:31:21.254837-05:
      DOI: 10.1002/anie.201711441
       
  • Optical Control of a Biological Reaction–Diffusion System
    • Authors: Philipp Glock; Johannes Broichhagen, Simon Kretschmer, Philipp Blumhardt, Jonas Mücksch, Dirk Trauner, Petra Schwille
      Pages: 2362 - 2366
      Abstract: Patterns formed by reaction and diffusion are the foundation for many phenomena in biology. However, the experimental study of reaction–diffusion (R–D) systems has so far been dominated by chemical oscillators, for which many tools are available. In this work, we developed a photoswitch for the Min system of Escherichia coli, a versatile biological in vitro R–D system consisting of the antagonistic proteins MinD and MinE. A MinE-derived peptide of 19 amino acids was covalently modified with a photoisomerizable crosslinker based on azobenzene to externally control peptide-mediated depletion of MinD from the membrane. In addition to providing an on–off switch for pattern formation, we achieve frequency-locked resonance with a precise 2D spatial memory, thus allowing new insights into Min protein action on the membrane. Taken together, we provide a tool to study phenomena in pattern formation using biological agents.Leading light: Optical control over the Min system, a biological reaction–diffusion system found in many bacteria, was achieved in vitro with the help of an azobenzene-cross-linked peptide derived from MinE. This system opens up new ways to study pattern formation in biology.
      PubDate: 2018-01-26T03:16:25.376045-05:
      DOI: 10.1002/anie.201712002
       
  • Discovery and Enumeration of Organic-Chemical and Biomimetic Reaction
           Cycles within the Network of Chemistry
    • Authors: Michał D. Bajczyk; Piotr Dittwald, Agnieszka Wołos, Sara Szymkuć, Bartosz A. Grzybowski
      Pages: 2367 - 2371
      Abstract: Analysis of the chemical-organic knowledge represented as a giant network reveals that it contains millions of reaction sequences closing into cycles. Without realizing it, independent chemists working at different times have jointly created examples of cyclic sequences that allow for the recovery of useful reagents and for the autoamplification of synthetically important molecules, those that mimic biological cycles, and those that can be operated one-pot.NOC-ing on heaven′s door: Big-data analysis of the network of organic chemistry (NOC) reveals that, over many decades, chemists have created—unknowingly—millions of cyclic reaction sequences including those that recover valuable substrates, those that amplify useful chemicals, or those that mimic biological cycles. The image shows a special type of a cycle (the so-called clique) in which any member can be made from any other one in one step. Colors correspond to years in which a reaction was first reported.
      PubDate: 2018-02-06T08:06:31.895286-05:
      DOI: 10.1002/anie.201712052
       
  • Palladium-Catalyzed Asymmetric Aminohydroxylation of 1,3-Dienes
    • Authors: Hong-Cheng Shen; Yu-Feng Wu, Ying Zhang, Lian-Feng Fan, Zhi-Yong Han, Liu-Zhu Gong
      Pages: 2372 - 2376
      Abstract: A PdII-catalyzed asymmetric aminohydroxylation of 1,3-dienes with N-tosyl-2-aminophenols was developed by making use of a chiral pyridinebis(oxazoline) ligand. The highly regioselective reaction provides direct and efficient access to chiral 3,4-dihydro-2H-1,4-benzoxazines in high yield and enantioselectivity (up to 96:4 e.r.). The reaction employs readily available N-tosyl-2-aminophenols as a unique aminohydroxylation reagent and is complementary to known asymmetric aminohydroxylation methods.Give me a ring: A palladium-catalyzed asymmetric aminohydroxylation reaction of 1,3-dienes with N-tosyl-2-aminophenols was developed by employing a chiral pyridinebis(oxazoline) ligand. This reaction furnishes optically active 3,4-dihydro-2H-1,4-benzoxazines in high yields and with high levels of regio- and stereoselectivity.
      PubDate: 2018-02-06T02:41:31.586099-05:
      DOI: 10.1002/anie.201712350
       
  • Highly Fluorescent Chiral N-S-Doped Carbon Dots from Cysteine: Affecting
           Cellular Energy Metabolism
    • Authors: Feng Li; Yiye Li, Xiao Yang, Xuexiang Han, Yang Jiao, Taotao Wei, Dayong Yang, Huaping Xu, Guangjun Nie
      Pages: 2377 - 2382
      Abstract: Cysteine-based chiral optically active carbon dots (CDs) and their effects on cellular energy metabolism, which is vital for essential cellular functions, have been barely reported. A green and effective synthesis strategy for chiral N-S-doped CDs (fluorescence quantum yield ca. 41.26 %) based on hydrothermal treatment of l- or d-cysteine at as low as 60 °C has been developed. This suggested that cysteine was instable in aqueous solutions and acts as a warning for high-temperature synthesis of nanomaterials using cysteine as stabilizer. Human bladder cancer T24 cells treated with l-CDs showed up-regulated glycolysis, while d-CDs had no similar effects. In contrast, no disturbance to the basal mitochondrial aerobic respiration of T24 cells was caused by either chiral CD.A green and effective synthesis has been developed for chiral CDs (fluorescence quantum yield ca. 41.26 %) based on hydrothermal treatment of small-molecule l- or d-cysteine at temperatures as low as 60 °C. The l-CDs showed chirality-dependent enhancement in cellular glycolysis, but did not influence the cellular ATP levels of T24 cells.
      PubDate: 2018-02-08T02:56:45.056182-05:
      DOI: 10.1002/anie.201712453
       
  • Electrochemical C−H/N−H Activation by Water-Tolerant Cobalt Catalysis
           at Room Temperature
    • Authors: Cong Tian; Leonardo Massignan, Tjark H. Meyer, Lutz Ackermann
      Pages: 2383 - 2387
      Abstract: Electrochemistry enabled C−H/N−H functionalizations at room temperature by external oxidant-free cobalt catalysis. Thus, the sustainable cobalt electrocatalysis manifold proceeds with excellent levels of chemoselectivity and positional selectivity, and with ample scope, thus allowing electrochemical C−H activation under exceedingly mild reaction conditions at room temperature in water.Electro Co: Cobalt-catalyzed C−H/N−H functionalizations were accomplished in H2O at 23 °C without toxic metal oxidants by using electricity. This sustainable cobalt electrocatalysis manifold proceeds with excellent levels of chemoselectivity and positional selectivity, and with ample scope.
      PubDate: 2018-01-17T09:25:55.739563-05:
      DOI: 10.1002/anie.201712647
       
  • Cationic Metallo-Polyelectrolytes for Robust Alkaline Anion-Exchange
           Membranes
    • Authors: Tianyu Zhu; Shichao Xu, Anisur Rahman, Emir Dogdibegovic, Peng Yang, Parasmani Pageni, Mohammad Pabel Kabir, Xiao-dong Zhou, Chuanbing Tang
      Pages: 2388 - 2392
      Abstract: Chemically inert, mechanically tough, cationic metallo-polyelectrolytes were conceptualized and designed as durable anion-exchange membranes (AEMs). Ring-opening metathesis polymerization (ROMP) of cobaltocenium-containing cyclooctene with triazole as the only linker group, followed by backbone hydrogenation, led to a new class of AEMs with a polyethylene-like framework and alkaline-stable cobaltocenium cation for ion transport. These AEMs exhibited excellent thermal, chemical and mechanical stability, as well as high ion conductivity.Ring-opening metathesis polymerization of cobaltocenium-containing cyclooctene with triazole as the only linker group, followed by backbone hydrogenation, has led to a new class of anion-exchange membranes (AEMs) with a polyethylene-like framework and alkaline-stable cobaltocenium cations for the ion transport. The AEMs show excellent thermal, chemical and mechanical stability, as well as high ion conductivity.
      PubDate: 2018-01-16T04:10:34.292473-05:
      DOI: 10.1002/anie.201712387
       
  • Design of Metal-Free Polymer Carbon Dots: A New Class of Room-Temperature
           Phosphorescent Materials
    • Authors: Songyuan Tao; Siyu Lu, Yijia Geng, Shoujun Zhu, Simon A. T. Redfern, Yubin Song, Tanglue Feng, Weiqing Xu, Bai Yang
      Pages: 2393 - 2398
      Abstract: Polymer carbon dots (PCDs) are proposed as a new class of room-temperature phosphorescence (RTP) materials. The abundant energy levels in PCDs increase the probability of intersystem crossing (ISC) and their covalently crosslinked framework structures greatly suppress the nonradiative transitions. The efficient methods allow the manufacture of PCDs with unique RTP properties in air without additional metal complexation or complicated matrix composition. They thus provide a route towards the rational design of metal-free RTP materials that may be synthesized easily. Furthermore, we find that RTP is associated with a crosslink-enhanced emission (CEE) effect, which provides further routes to design improved PCDs with diverse RTP performance. Our results show the potential of PCDs as a universal route to achieve effective metal-free RTP.Room-temperature phosphorescence: Polymer carbon dots (PCDs) showing metal-free room-temperature phosphorescence (RTP) have been constructed by using a facile method. The contribution of the cross-link-enhanced emission effect to the generation of RTP is verified and proposed as a guideline to forecast and synthesize a series of PCDs with diverse RTP performance (ISC=intersystem crossing).
      PubDate: 2018-02-06T09:26:32.703377-05:
      DOI: 10.1002/anie.201712662
       
  • Orientation Control of Molecularly Functionalized Surfaces Applied to the
           Simultaneous Alignment and Sorting of Carbon Nanotubes
    • Authors: Serxho Selmani; Derek J. Schipper
      Pages: 2399 - 2403
      Abstract: Self-assembly has been relied upon for molecular alignment in many advanced technological applications. However, although effective, it is inherently limited in its capability for optimization. Despite the potential benefits, the seemingly fundamental strategy of external orientation control has yet to be realized. Herein we demonstrate an approach that allows control of the orientation of small molecules covalently bound to a surface. The method exploits an alignment relay technique, passing alignment information through a liquid-crystal medium to small molecules to control surface functionalization events. The method is technically simple and can be carried out on a bench top without the need for specialized equipment. Moreover, we demonstrate the utility of the resulting surfaces to address two long-standing problems in nanoscience: the sorting and alignment of single-walled carbon nanotubes. This new method enabled significant alignment of the nanotubes as well as length and diameter sorting.The ART of science: An alignment relay technique (ART) has been developed for the alignment of organic molecules covalently bound to a surface. The resulting functionalized surface was used to promote the simultaneous alignment and length and diameter sorting of single-walled carbon nanotubes (see picture).
      PubDate: 2018-02-05T10:11:38.697992-05:
      DOI: 10.1002/anie.201712779
       
  • Enzymatic Electrosynthesis of Alkanes by Bioelectrocatalytic
           Decarbonylation of Fatty Aldehydes
    • Authors: Sofiene Abdellaoui; Florika C. Macazo, Rong Cai, Antonio L. De Lacey, Marcos Pita, Shelley D. Minteer
      Pages: 2404 - 2408
      Abstract: An enzymatic electrosynthesis system was created by combining an aldehyde deformylating oxygenase (ADO) from cyanobacteria that catalyzes the decarbonylation of fatty aldehydes to alkanes and formic acid with an electrochemical interface. This system is able to produce a range of alkanes (octane to propane) from aldehydes and alcohols. The combination of this bioelectrochemical system with a hydrogenase bioanode yields a H2/heptanal enzymatic fuel cell (EFC) able to simultaneously generate electrical energy with a maximum current density of 25 μA cm−2 at 0.6 V and produce hexane with a faradaic efficiency of 24 %.The combination of an aldehyde deformylating oxygenase that catalyzes the decarbonylation of fatty aldehydes to alkanes and formic acid with an electrochemical interface yields an enzymatic electrosynthesis system that produces various alkanes from aldehydes and alcohols. Combining this bioelectrochemical system with a hydrogenase bioanode yields a H2/heptanal enzymatic fuel cell that generates electrical energy while producing hexane.
      PubDate: 2018-01-16T10:16:02.122251-05:
      DOI: 10.1002/anie.201712890
       
  • Fe2Si5N8: Access to Open-Shell Transition-Metal Nitridosilicates
    • Authors: Philipp Bielec; Oliver Janka, Theresa Block, Rainer Pöttgen, Wolfgang Schnick
      Pages: 2409 - 2412
      Abstract: Highly condensed nitridosilicates doped with Eu2+ or Ce3+ play an important role in saving energy by converting the blue light of (In,Ga)N-LEDs. Although nitridosilicates are known for great structural variety based on covalent anionic Si-N networks, elemental variety is restricted. Presenting a significant extension of the latter, this work describes a general access to open-shell transition-metal nitridosilicates. As a proof-of-principle, the first iron nitridosilicate, namely Fe2Si5N8, was prepared by exchanging Ca2+ in α-Ca2Si5N8 applying a FeCl2 melt (salt metathesis). The title compound was analyzed by powder X-ray diffraction, EDX, ICP-OES, combustion analysis, TG/DSC, Mössbauer spectroscopy and magnetic susceptibility measurements. Furthermore, the structure of α-Ca2Si5N8 was determined at 1073 and 1173 K confirming the anionic network of α-Ca2Si5N8 providing possible migration pathways for the ion-exchange reaction.Cation exchange is possible in nitridosilicates by applying salt melts. Application of this strategy led to the first iron nitridosilicate Fe2Si5N8, which represents a significant extension in elemental variety for nitridosilicates. Motivated by experimental results, the mechanism of the ion exchange was elucidated by identifying possible migration channels for divalent cations in α-Ca2Si5N8.
      PubDate: 2018-02-05T10:09:37.189477-05:
      DOI: 10.1002/anie.201713006
       
  • Manipulating Band Structure through Reconstruction of Binary Metal Sulfide
           for High-Performance Thermoelectrics in Solution-Synthesized
           Nanostructured Bi13S18I2
    • Authors: Biao Xu; Tianli Feng, Matthias T. Agne, Qing Tan, Zhe Li, Kazuki Imasato, Lin Zhou, Je-Hyeong Bahk, Xiulin Ruan, G. Jeffery Snyder, Yue Wu
      Pages: 2413 - 2418
      Abstract: Reconstructing canonical binary compounds by inserting a third agent can significantly modify their electronic and phonon structures. Therefore, it has inspired the semiconductor communities in various fields. Introducing this paradigm will potentially revolutionize thermoelectrics as well. Using a solution synthesis, Bi2S3 was rebuilt by adding disordered Bi and weakly bonded I. These new structural motifs and the altered crystal symmetry induce prominent changes in electrical and thermal transport, resulting in a great enhancement of the figure of merit. The as-obtained nanostructured Bi13S18I2 is the first non-toxic, cost-efficient, and solution-processable n-type material with z T=1.0.Bi2S3 was rebuilt by adding disordered Bi and weakly bonded I in a solution synthesis. The new structural motifs and the altered crystal symmetry induce prominent changes in electrical and thermal transport. The as-obtained nanostructured Bi13S18I2 is a non-toxic, cost-efficient, and solution-processable n-type thermoelectric material with z T=1.0.
      PubDate: 2018-02-05T10:00:45.075848-05:
      DOI: 10.1002/anie.201713223
       
  • Synthesis and Structure Revision of Dichrocephones A and B
    • Authors: Volker M. Schmiedel; Young J. Hong, Dieter Lentz, Dean J. Tantillo, Mathias Christmann
      Pages: 2419 - 2422
      Abstract: Herein, we report the first enantioselective synthesis of dichrocephones A and B, which are cytotoxic triquinane sesquiterpenes with a dense array of stereogenic centers within a strained polycyclic environment. Key features include the application of a catalytic asymmetric Wittig reaction, followed by stereoselective functionalization of the propellane core into a pentacyclic intermediate. Double reductive ring cleavage yielded the proposed structure of dichrocephone A. Mismatched spectroscopic data for our synthetic material compared to the natural isolate led us to revise the previously proposed configuration based on biosynthetic considerations and NMR calculations. Implementation of these findings culminated in the synthesis of dichrocephones A and B.Cyclize and revise: Total synthesis of the densely functionalized dichrocephones A and B is described. Key features include a catalytic asymmetric Wittig reaction, followed by stereoselective functionalization of the propellane core into a pentacyclic intermediate. Mismatched spectroscopic data for the initial synthetic product compared to the natural isolate led to a revision of the previously proposed configuration.
      PubDate: 2018-01-16T10:15:46.532135-05:
      DOI: 10.1002/anie.201711766
       
  • Mechanochemical Activation of Iron Cyano Complexes: A Prebiotic Impact
           Scenario for the Synthesis of α-Amino Acid Derivatives
    • Authors: Carsten Bolm; Rita Mocci, Christian Schumacher, Mathias Turberg, Francesco Puccetti, José G. Hernández
      Pages: 2423 - 2426
      Abstract: Mechanochemical activation of iron cyano complexes by ball milling results in the formation of HCN, which can be trapped and incorporated into α-aminonitriles. This prebiotic impact scenario can be extended by mechanochemically transforming the resulting α-aminonitriles into α-amino amides using a chemical route related to early Earth conditions.Prebiotic-impact chemistry: Mechanochemistry enabled the study of a prebiotic impact scenario for the formation α-amino acid derivatives under ball milling conditions. Ball milling iron cyano complexes results in the formation of HCN, which can be trapped and incorporated into α-aminonitriles.
      PubDate: 2018-02-05T09:59:30.387851-05:
      DOI: 10.1002/anie.201713109
       
  • MoP Nanoparticles Supported on Indium-Doped Porous Carbon: Outstanding
           Catalysts for Highly Efficient CO2 Electroreduction
    • Authors: Xiaofu Sun; Lu Lu, Qinggong Zhu, Congyi Wu, Dexin Yang, Chunjun Chen, Buxing Han
      Pages: 2427 - 2431
      Abstract: Electrochemical reduction of CO2 into value-added product is an interesting area. MoP nanoparticles supported on porous carbon were synthesized using metal–organic frameworks as the carbon precursor, and initial work on CO2 electroreduction using the MoP-based catalyst were carried out. It was discovered that MoP nanoparticles supported on In-doped porous carbon had outstanding performance for CO2 reduction to formic acid. The Faradaic efficiency and current density could reach 96.5 % and 43.8 mA cm−2, respectively, when using ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate as the supporting electrolyte. The current density is higher than those reported up to date with very high Faradaic efficiency. The MoP nanoparticles and the doped In2O3 cooperated very well in catalyzing the CO2 electroreduction.MoP nanoparticles supported on In-doped porous carbon show outstanding performance for CO2 reduction to formate. The Faradaic efficiency and current density reach 96.5 % and 43.8 mA cm−2, respectively, when using an ionic liquid as the supporting electrolyte. MoP and In-doped carbon support show an excellent synergistic effect for promoting this reaction.
      PubDate: 2018-02-02T02:41:14.587255-05:
      DOI: 10.1002/anie.201712221
       
  • Direct Transformation of Esters into Heterocyclic Fluorophores
    • Authors: Christian Fischer; Christof Sparr
      Pages: 2436 - 2440
      Abstract: Despite the manifold use of heterocyclic fluorophores, only a fraction of the desired dye diversity can be accessed by contemporary synthetic approaches. Herein, we describe a modular method that converts various carboxylic acid esters directly into a broad spectrum of heteroanthrylium fluorophores. The double addition of heteroatom-bridged 1,5-bifunctional organomagnesium reagents to esters leads to the formation of acridinium, xanthylium, and SiR fluorophores after dehydrative acidic work-up. This one-step synthetic method provides access to organophotoredox catalysts for dual catalysis with nickel and dyes amenable to fluorescence enhancement.The spectrum of esters: Heteroatom-bridged 1,5-bifunctional organomagnesium reagents enable the direct transformation of carboxylic acid esters into acridinium, xanthylium, and SiR dyes. Owing to the high diversity of esters, the chemical, photophysical, and electrochemical properties of the fluorophores can be ideally modulated to provide organophotoredox catalysts for dual catalysis with nickel and dyes amenable to fluorescence enhancement.
      PubDate: 2018-01-29T05:00:45.75398-05:0
      DOI: 10.1002/anie.201711296
       
  • Synthesis of α-Chiral Ketones and Chiral Alkanes Using Radical Polar
           Crossover Reactions of Vinyl Boron Ate Complexes
    • Authors: Carolin Gerleve; Marvin Kischkewitz, Armido Studer
      Pages: 2441 - 2444
      Abstract: Vinyl boron ate complexes of enantioenriched secondary alkyl pinacolboronic esters undergo stereospecific radical-induced 1,2-migration in radical polar crossover reactions. In this three-component process various commercially available alkyl iodides act as radical precursors and light is used for chain initiation. Subsequent oxidation and protodeborylation leads to valuable α-chiral ketones and chiral alkanes, respectively, with excellent enantiopurity.Radical and polar! Various chiral vinyl boron ate complexes, readily generated from the corresponding pinacolboronic esters and vinyllithium, react in a radical polar crossover cascade to produce secondary alkyl boronic esters that are either oxidized to valuable α-chiral ketones or protodeborylated to the corresponding alkanes. Products are isolated in good overall yields and excellent stereospecificity. Pin=pinacolate.
      PubDate: 2018-01-16T10:02:12.403432-05:
      DOI: 10.1002/anie.201711390
       
  • Disilenyl Silylene Reactivity of a Cyclotrisilene
    • Authors: Hui Zhao; Kinga Leszczyńska, Lukas Klemmer, Volker Huch, Michael Zimmer, David Scheschkewitz
      Pages: 2445 - 2449
      Abstract: The highly reactive silicon congeners of cyclopropene, cyclotrisilenes (c-Si3R4), typically undergo either π-addition to the Si=Si double bond or σ-insertion into the Si−Si single bond. In contrast, treatment of c-Si3Tip4 (Tip=2,4,6-iPr3C6H2) with styrene and benzil results in ring opening of the three-membered ring to formally yield the [1+2]- and [1+4] cycloaddition product of the isomeric disilenyl silylene to the C=C bond and the 1,2-diketone π system, respectively. At elevated temperature, styrene is released from the [1+2]-addition product leading to the thermodynamically favored housane species after [2+2] cycloaddition of styrene and c-Si3Tip4.Speed is of the essence to ring-open the peraryl-substituted cyclotrisilene (R=2,4,6-iPr3C6H2) and coax disilenyl silylene reactivity towards benzil and styrene from it. In the case of styrene, the kinetic product with a residual R2Si=SiR substituent is transformed into the saturated thermodynamic product by the re-detachment of the styrene reagent at elevated temperature, as confirmed by a control experiment under vacuum.
      PubDate: 2018-02-08T05:06:53.81505-05:0
      DOI: 10.1002/anie.201711833
       
  • Active Molybdenum-Based Anode for Dehydrogenative Coupling Reactions
    • Authors: Sebastian B. Beil; Timo Müller, Sydney B. Sillart, Peter Franzmann, Alexander Bomm, Michael Holtkamp, Uwe Karst, Wolfgang Schade, Siegfried R. Waldvogel
      Pages: 2450 - 2454
      Abstract: A new and powerful active anode system that can be operated in 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) has been discovered. In HFIP the molybdenum anode forms a compact, conductive, and electroactive layer of higher-valent molybdenum species. This system can replace powerful but stoichiometrically required MoV reagents for the dehydrogenative coupling of aryls. This electrolytic reaction is more sustainable and allows the conversion of a broad scope of activated arenes.Electrochemically driven and with a reactivity comparable to that of MoV reagents, a novel active anode system based on 1,1,1,3,3,3-hexafluoro-2-propanol and molybdenum mediates the dehydrogenative coupling of arenes.
      PubDate: 2018-02-05T10:15:04.014613-05:
      DOI: 10.1002/anie.201712718
       
  • RuBisCO-Inspired CO2 Activation and Transformation by an Iridium(I)
           Complex
    • Authors: Jens Langer; Andrea Hamza, Imre Pápai
      Pages: 2455 - 2458
      Abstract: The synthesis of a new iridium(I) complex containing an enamido phosphine anion (dbuP−) and its unique reactivity with CO2 is reported. The complex binds two equivalents of CO2 and initiates a highly selective reaction cascade. The reaction leads to the reversible cleavage of CO2 and the enamido ligand as well. Computational analysis points to the existence of a relatively stable Ir-CO2 complex as a reaction intermediate prior to CO2 cleavage, which was confirmed experimentally. The observed transformation resembles several aspects of enzymatic CO2 fixation by RuBisCO.COO-peration: The highly selective binding and transformation of CO2 by an iridium complex clearly shows cooperative effects between the two CO2 molecules involved. The reversible transformation resembles some aspects of CO2 fixation by the RuBisCO enzyme.
      PubDate: 2018-01-29T09:01:19.416903-05:
      DOI: 10.1002/anie.201712893
       
  • Photocatalytic Aerobic Phosphatation of Alkenes
    • Authors: Christian Depken; Felix Krätzschmar, Rene Rieger, Katharina Rode, Alexander Breder
      Pages: 2459 - 2463
      Abstract: A catalytic regime for the direct phosphatation of simple, non-polarized alkenes has been devised that is based on using ordinary, non-activated phosphoric acid diesters as the phosphate source and O2 as the terminal oxidant. The title method enables the direct and highly economic construction of a diverse range of allylic phosphate esters. From a conceptual viewpoint, the aerobic phosphatation is entirely complementary to traditional methods for phosphate ester formation, which predominantly rely on the use of prefunctionalized or preactivated reactants, such as alcohols and phosphoryl halides. The title transformation is enabled by the interplay of a photoredox and a selenium π-acid catalyst and involves a sequence of single-electron-transfer processes.Once in a blue moon: The aerobic dehydrogenative coupling of simple hydrogen phosphates with non-activated alkenes generates a diverse range of allylic phosphates through the catalytic interplay of a photosensitizer (PS) and a chalcogen Lewis acid (Se). In addition to its operational simplicity and high chemoselectivity, the title reaction also enables the facile consecutive redox alkylation of olefins with organocuprates.
      PubDate: 2018-01-17T09:10:38.323103-05:
      DOI: 10.1002/anie.201711599
       
  • The Catalytic Asymmetric Mukaiyama–Michael Reaction of Silyl Ketene
           Acetals with α,β-Unsaturated Methyl Esters
    • Authors: Tim Gatzenmeier; Philip S. J. Kaib, Julia B. Lingnau, Richard Goddard, Benjamin List
      Pages: 2464 - 2468
      Abstract: α,β-Unsaturated esters are readily available but challenging substrates to activate in asymmetric catalysis. We now describe an efficient, general, and highly enantioselective Mukaiyama–Michael reaction of silyl ketene acetals with α,β-unsaturated methyl esters that is catalyzed by a silylium imidodiphosphorimidate (IDPi) Lewis acid.A reaction half-life of over 35 million years without catalysis: Cinnamate esters belong to the least electrophilic Michael acceptors and react extremely slowly even with strong nucleophiles such as silyl ketene acetals if no catalysis is applied. Extremely active silylium imidodiphosphorimidate (IDPi) Lewis acid catalysts now enable highly efficient Mukaiyama–Michael reactions at low catalyst loadings and with excellent enantio- and diastereocontrol.
      PubDate: 2018-01-26T08:50:41.140689-05:
      DOI: 10.1002/anie.201712088
       
  • Reductive Amination by Photoredox Catalysis and Polarity-Matched Hydrogen
           Atom Transfer
    • Authors: Xingwei Guo; Oliver S. Wenger
      Pages: 2469 - 2473
      Abstract: The excitation of a RuII photosensitizer in the presence of ascorbic acid leads to the reduction of iminium ions to electron-rich α-aminoalkyl radical intermediates, which are rapidly converted into reductive amination products by thiol-mediated hydrogen atom transfer (HAT). As a result, the reductive amination of carbonyl compounds with amines by photoredox catalysis proceeds in good to excellent yields and with broad substrate scope and good functional group tolerance. The three key features of this work are 1) the rapid interception of electron-rich α-aminoalkyl radical intermediates by polarity-matched HAT in a photoredox reaction, 2) the method of reductive amination by photoredox catalysis itself, and 3) the application of this new method for temporally and spatially controlled reactions on a solid support, as demonstrated by the attachment of a fluorescent dye on an activated cellulose support by photoredox-catalyzed reductive amination.Light instead of hydride: A photoredox process for reductive amination is reported, alongside substrate scope studies and in-depth mechanistic investigations. With this new method, reductive amination reactions can be conducted in a temporally and spatially controlled fashion, for example, on solid supports.
      PubDate: 2018-01-18T07:57:26.771075-05:
      DOI: 10.1002/anie.201711467
       
  • Photocontrolled Release of Chemicals from Nano- and Microparticle
           Containers
    • Authors: Christoph Englert; Ivo Nischang, Cornelia Bader, Philipp Borchers, Julien Alex, Michael Pröhl, Martin Hentschel, Matthias Hartlieb, Anja Traeger, Georg Pohnert, Stephanie Schubert, Michael Gottschaldt, Ulrich S. Schubert
      Pages: 2479 - 2482
      Abstract: A benzoin-derived diol linker was synthesized and used to generate biocompatible polyesters that can be fully decomposed on demand upon UV irradiation. Extensive structural optimization of the linker unit was performed to enable the defined encapsulation of diverse organic compounds in the polymeric structures and allow for a well-controllable polymer cleavage process. Selective tracking of the release kinetics of encapsulated model compounds from the polymeric nano- and microparticle containers was performed by confocal laser scanning microscopy in a proof-of-principle study. The physicochemical properties of the incorporated and released model compounds ranged from fully hydrophilic to fully hydrophobic. The demonstrated biocompatibility of the utilized polyesters and degradation products enables their use in advanced applications, for example, for the smart packaging of UV-sensitive pharmaceuticals, nutritional components, or even in the area of spatially selective self-healing processes.Chemicals on demand: Biocompatible polyesters were synthesized that can be fully decomposed by UV irradiation. The formation of nano- and microparticles allows for the defined encapsulation of structurally diverse organic compounds and a controllable cleavage process. These particles can be used for the smart packaging of UV-sensitive pharmaceuticals or for spatially selective self-healing processes.
      PubDate: 2018-01-16T10:01:18.067479-05:
      DOI: 10.1002/anie.201710756
       
  • Controlling the Polymer Microstructure in Anionic Polymerization by
           Compartmentalization
    • Authors: Elisabeth Rieger; Jan Blankenburg, Eduard Grune, Manfred Wagner, Katharina Landfester, Frederik R. Wurm
      Pages: 2483 - 2487
      Abstract: An ideal random anionic copolymerization is forced to produce gradient structures by physical separation of two monomers in emulsion compartments. One monomer (M) is preferably soluble in the droplets, while the other one (D) prefers the continuous phase of a DMSO-in-cyclohexane emulsion. The living anionic copolymerization of two activated aziridines is thus confined to the DMSO compartments as polymerization occurs selectively in the droplets. Dilution of the continuous phase adjusts the local concentration of monomer D in the droplets and thus the gradient of the resulting copolymer. The copolymerizations in emulsion are monitored by real-time 1H NMR kinetics, proving a change of the reactivity ratios of the two monomers upon dilution of the continuous phase from ideal random to adjustable gradients by simple dilution.The selective solubility of two monomers in a DMSO/cyclohexane emulsion forces the production of controllable gradient copolymers.
      PubDate: 2018-01-18T07:57:38.854628-05:
      DOI: 10.1002/anie.201710417
       
  • The Common Intermediates of Oxygen Evolution and Dissolution Reactions
           during Water Electrolysis on Iridium
    • Authors: Olga Kasian; Jan-Philipp Grote, Simon Geiger, Serhiy Cherevko, Karl J. J. Mayrhofer
      Pages: 2488 - 2491
      Abstract: Understanding the pathways of catalyst degradation during the oxygen evolution reaction is a cornerstone in the development of efficient and stable electrolyzers, since even for the most promising Ir based anodes the harsh reaction conditions are detrimental. The dissolution mechanism is complex and the correlation to the oxygen evolution reaction itself is still poorly understood. Here, by coupling a scanning flow cell with inductively coupled plasma and online electrochemical mass spectrometers, we monitor the oxygen evolution and degradation products of Ir and Ir oxides in situ. It is shown that at high anodic potentials several dissolution routes become possible, including formation of gaseous IrO3. On the basis of experimental data, possible pathways are proposed for the oxygen-evolution-triggered dissolution of Ir and the role of common intermediates for these reactions is discussed.Possible routes of Ir dissolution are proposed based on the detection of a common intermediate in the oxygen evolution reaction. At least three dissolution pathways are possible depending on the nature of the electrode and potential. At high current densities two reactions proceed via formation of volatile IrO3. Hindering IrO3 hydrolysis can be a strategy to improve electrode stability in the oxygen evolution reaction.
      PubDate: 2018-02-05T09:31:10.347834-05:
      DOI: 10.1002/anie.201709652
       
  • Lanthanide Complexes Supported by a Trizinc Crown Ether as Catalysts for
           Alternating Copolymerization of Epoxide and CO2: Telomerization Controlled
           by Carboxylate Anions
    • Authors: Haruki Nagae; Ryota Aoki, Shin-nosuke Akutagawa, Julian Kleemann, Risa Tagawa, Tobias Schindler, Gyeongshin Choi, Thomas P. Spaniol, Hayato Tsurugi, Jun Okuda, Kazushi Mashima
      Pages: 2492 - 2496
      Abstract: A new family of heterometallic catalysts based on trimetalated macrocyclic tris(salen) ligands and rare-earth metals was prepared and structurally characterized. The LaZn3 system containing anionic ligands such as acetate plays a critical role in catalyzing the alternating copolymerization of cyclohexene oxide (CHO) and CO2 with a high proportion of carbonate linkages. Among the lanthanide metals, the CeZn3 system exhibits high catalytic activity with a turnover frequency (TOF) of over 370 h−1. NMR analysis of the complex and end-group analysis of the polymer suggest that the acetate ligands are rapidly exchanged, not only among coordinated acetates, but also between coordinated acetates and added carboxylate anions. These unique properties make this the first example of telomerization for the copolymerization of CHO and CO2.Homogeneous heterometallic complexes based on the trizincated macrocycle trisaloph and a rare-earth metal showed high catalytic activity for the alternating copolymerization of cyclohexene oxide and CO2 with a high proportion of carbonate repeat units. The carboxylate anion of the ammonium salt initiates the telomerization, providing the polycarbonate with the corresponding carboxylate.
      PubDate: 2018-01-17T09:15:32.086854-05:
      DOI: 10.1002/anie.201709218
       
  • Dual Ligand-Enabled Nondirected C−H Olefination of Arenes
    • Authors: Hao Chen; Philipp Wedi, Tim Meyer, Ghazal Tavakoli, Manuel van Gemmeren
      Pages: 2497 - 2501
      Abstract: The application of the Pd-catalyzed oxidative C−H olefination of arenes, also known as the Fujiwara–Moritani reaction, has traditionally been limited by the requirement for directing groups on the substrate or the need to use the arene in large excess, typically as a (co)solvent. Herein the development of a catalytic system is described that, through the combined action of two complementary ligands, makes it possible to use directing-group-free arenes as limiting reagents for the first time. The reactions proceed under a combination of both steric and electronic control and enable the application of this powerful reaction to valuable arenes, which cannot be utilized in excess.How many ligands does it take to change a bond' The Pd-catalyzed C−H olefination of arenes as the limiting reagents is reported. The combined action of two ligands, N-acetylglycine and a pyridine, enables this Fujiwara–Moritani reaction under steric/electronic control; traditionally this reaction required use of arenes as (co)solvents or of directing groups on the substrate.
      PubDate: 2018-01-26T12:20:59.300111-05:
      DOI: 10.1002/anie.201712235
       
  • Inside Back Cover: Cationic Metallo-Polyelectrolytes for Robust Alkaline
           Anion-Exchange Membranes (Angew. Chem. Int. Ed. 9/2018)
    • Authors: Tianyu Zhu; Shichao Xu, Anisur Rahman, Emir Dogdibegovic, Peng Yang, Parasmani Pageni, Mohammad Pabel Kabir, Xiao-dong Zhou, Chuanbing Tang
      Pages: 2503 - 2503
      Abstract: Cationic polyelectrolytes are widely used as anion-exchange membranes (AEMs) in alkaline fuel cells for converting fuels into electricity. In their Communication on page 2388 ff., C. Tang et al. report a class of metallo-polyelectrolytes that are conceptualized for chemically inert AEMs under highly basic conditions. The AEMs exhibit excellent thermal, chemical, and mechanical stability, as well as high ion conductivity.
      PubDate: 2018-01-31T02:26:04.578162-05:
      DOI: 10.1002/anie.201800722
       
  • Back Cover: Seeded Polymerization through the Interplay of Folding and
           
    • Authors: Soichiro Ogi; Kentaro Matsumoto, Shigehiro Yamaguchi
      Pages: 2504 - 2504
      Abstract: The utility of an amino acid based diamide in seeded supramolecular polymerization is demonstrated by S. Ogi, K. Matsumoto, and S. Yamaguchi in their Communication on page 2339 ff. The spontaneous aggregation (right pathway) of diamides in an extended form is effectively retarded by folding of the diamide moiety through intramolecular hydrogen bonding. Under such out-of-equilibrium conditions, the time course of the self-assembly was successfully regulated through a seeding approach (left pathway).
      PubDate: 2018-02-02T02:32:29.10255-05:0
      DOI: 10.1002/anie.201800993
       
  • Driving Chemistry and Europe
    • Authors: Gilberte Chambaud
      Pages: 2264 - 2265
      Abstract: “… Mobility that favors individual exchanges between researchers is extremely important for the scientific community. The merging of scientific publications within a consortium of European journals and the creation of the European Chemistry Congresses have been major successes …” Read more in the Guest Editorial by Gilberte Chambaud.
      PubDate: 2017-12-14T04:40:47.574452-05:
      DOI: 10.1002/anie.201709947
       
  • Shunai Che
    • Pages: 2284 - 2284
      Abstract: “The secret of being a successful scientist is to question any known results and conclusions. My favorite molecule is DNA, with the most beautiful structures and amazing functionalities ...” This and more about Shunai Che can be found on page 2284.
      PubDate: 2017-11-17T05:21:10.420399-05:
      DOI: 10.1002/anie.201711485
       
  • Cristina Nevado
    • Pages: 2285 - 2285
      Abstract: “My favorite way to spend a holiday is diving in warm waters. Looking back over my career, I still feel I am at the outset and the last ten years went by way too fast! ...” This and more about Cristina Nevado can be found on page 2285.
      PubDate: 2017-12-20T04:55:27.360819-05:
      DOI: 10.1002/anie.201712494
       
 
 
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