Chemistry - A European Journal

Cover image for Vol. 17 Issue 43

October 17, 2011

Volume 17, Issue 43

Pages 11937–12211

  1. Cover Picture

    1. Top of page
    2. Cover Picture
    3. Inside Cover
    4. Graphical Abstract
    5. News
    6. Concept
    7. Communications
    8. Full Papers
    9. Preview
    1. Cover Picture: Competitive Reactions of Organophosphorus Radicals on Coke Surfaces (Chem. Eur. J. 43/2011) (page 11937)

      Dr. Saron Catak, Dr. Ir. Karen Hemelsoet, Dr. Laura Hermosilla , Prof. Dr. Michel Waroquier and Prof. Dr. Ir. Veronique Van Speybroeck

      Article first published online: 11 OCT 2011 | DOI: 10.1002/chem.201190210

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      Organophosphorus additives are used as coke-inhibiting agents to reduce coking, an undesirable process that occurs in cracking units. DFT calculations show that organophosphorus radicals compete with coke-inducing carbonaceous radicals for the peripheral sites of the growing coke layer. The figure illustrates the organophosphorus radical that adds to the edge of the growing polyaromatic hydrocarbon, strategically blocking the peripheral site, preventing further coke growth. For more details see the Full Paper by S. Catak, V. Van Speybroeck et al. on page 12027 ff.

  2. Inside Cover

    1. Top of page
    2. Cover Picture
    3. Inside Cover
    4. Graphical Abstract
    5. News
    6. Concept
    7. Communications
    8. Full Papers
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    1. Inside Cover: Investigating Cation Binding in the Polyoxometalate-Super-Crown [P8W48O184]40− (Chem. Eur. J. 43/2011) (page 11938)

      Thomas Boyd, Dr. Scott G. Mitchell, David Gabb, Dr. De-Liang Long and Prof. Leroy Cronin

      Article first published online: 11 OCT 2011 | DOI: 10.1002/chem.201190211

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      The complex host–guest chemistry of the crown-type cluster [P8W48O184]40− has been studied by a combination of 31P NMR spectroscopy and isothermal titration calorimetry. This cluster which was originally reported in 1985 is witnessing a recent surge in interest. Herein its selectivity for potassium over ammonium is demonstrated, and its unique and intriguing aqueous behavior is deciphered. For details see the Communication by L. Cronin et al. on page 12010 ff.

  3. Graphical Abstract

    1. Top of page
    2. Cover Picture
    3. Inside Cover
    4. Graphical Abstract
    5. News
    6. Concept
    7. Communications
    8. Full Papers
    9. Preview
    1. Graphical Abstract: Chem. Eur. J. 43/2011 (pages 11941–11950)

      Article first published online: 11 OCT 2011 | DOI: 10.1002/chem.201190212

  4. News

    1. Top of page
    2. Cover Picture
    3. Inside Cover
    4. Graphical Abstract
    5. News
    6. Concept
    7. Communications
    8. Full Papers
    9. Preview
  5. Concept

    1. Top of page
    2. Cover Picture
    3. Inside Cover
    4. Graphical Abstract
    5. News
    6. Concept
    7. Communications
    8. Full Papers
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    1. Flow Chemistry

      The Microwave-to-Flow Paradigm: Translating High-Temperature Batch Microwave Chemistry to Scalable Continuous-Flow Processes (pages 11956–11968)

      Dr. Toma N. Glasnov and Prof. Dr. C. Oliver Kappe

      Article first published online: 20 SEP 2011 | DOI: 10.1002/chem.201102065

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      Microwaves not required! Conventionally heated flow reactors (coils or chips) fitted with back-pressure regulators can mimic the high temperatures and pressures attainable in a sealed-vessel microwave instrument. Such devices can therefore be used to perform otherwise difficult to scale microwave chemistry (see scheme).

  6. Communications

    1. Top of page
    2. Cover Picture
    3. Inside Cover
    4. Graphical Abstract
    5. News
    6. Concept
    7. Communications
    8. Full Papers
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    1. Free Radicals

      Free Radical Reactivity of Mono- and Dichlorosilylene with Muonium (pages 11970–11973)

      Prof. Paul W. Percival, Dr. Jean-Claude Brodovitch, Mina Mozafari, Dr. Amitabha Mitra, Prof. Robert West, Dr. Rajendra S. Ghadwal, Dr. Ramachandran Azhakar and Prof. Dr. Herbert W. Roesky

      Article first published online: 9 SEP 2011 | DOI: 10.1002/chem.201102405

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      The H atom analogue muonium (Mu) has been used to explore the free radical reactivity of two novel chlorosilylenes. Spectroscopic and computational investigations show that Mu adds to the silicon in the NHC-stabilised dichlorosilylene. In contrast, Mu reacts at the carbon of a siladiazirene ring in the monochlorosilylene. Muon and Cl hyperfine constants are consistent with flipping of the Si[BOND]Cl bond from one side of the ring to the other.

    2. C[BOND]H Activation

      Palladium-Catalyzed C[BOND]H Bond Functionalization of a Metal–Organic Framework (MOF): Mild, Selective, and Efficient (pages 11974–11977)

      Thomas Dröge, Andreas Notzon, Dr. Roland Fröhlich and Prof. Dr. Frank Glorius

      Article first published online: 16 SEP 2011 | DOI: 10.1002/chem.201101850

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      Mild-mannered MOFs: A selective and efficient palladium-catalyzed C[BOND]H phenylation of a UMCM-1-type metal–organic framework (MOF) under mild conditions is reported. This highly regioselective postsynthetic modification obviates the need for a pre-existing classical functional group at the reaction site (see scheme). The concept of site-specific C[BOND]H activation could potentially be extended to many classes of MOF structures.

    3. Biosensors

      A Gold Nanoparticle-Based Fluorescence Turn-On Probe for Highly Sensitive Detection of Polyamines (pages 11978–11982)

      Tae-Il Kim, Jihye Park and Prof. Youngmi Kim

      Article first published online: 16 SEP 2011 | DOI: 10.1002/chem.201102060

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      Free to be bright: Highly sensitive and convenient fluorescence turn-on detection of polyamines, important biomarkers for cancers, was achieved with a probe that consists of a cationic BODIPY adsorbed on gold nanoparticles (AuNPs), in which the fluorescence of the dye is completely quenched through efficient energy transfer, and is selectively recovered upon addition of the analyte (see figure).

    4. Configuration Determination

      Residual Dipolar Coupling Enhanced NMR Spectroscopy and Chiroptics: A Powerful Combination for the Complete Elucidation of Symmetrical Small Molecules (pages 11983–11986)

      Dr. Carlos Pérez-Balado, Han Sun, Prof. Christian Griesinger, Prof. Ángel R. de Lera and Dr. Armando Navarro-Vázquez

      Article first published online: 16 SEP 2011 | DOI: 10.1002/chem.201101385

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      Absolute configuration assignment: Residual dipolar coupling (RDC)-enhanced NMR spectroscopy provides detailed configurational and conformational information on a symmetric homodimeric chiral organic compound. This allows unequivocal assignment of absolute configuration by using electronic circular dichroism and time-dependent (TD)-DFT computations.

    5. Biosensors

      NIR-Emissive Alkynylplatinum(II) Terpyridyl Complex as a Turn-On Selective Probe for Heparin Quantification by Induced Helical Self-Assembly Behaviour (pages 11987–11990)

      Margaret Ching-Lam Yeung and Prof. Dr. Vivian Wing-Wah Yam

      Article first published online: 13 SEP 2011 | DOI: 10.1002/chem.201101762

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      NIR-emissive heparin sensor: A convenient and selective sensing protocol has been established for the quantification of both unfractionated and low-molecular-weight heparin, based on the heparin-induced helical self-assembly feature of a NIR-emissive alkynylplatinum(II) terpyridyl complex (see scheme), for which the detection range covers the clinical dosage level.

    6. Alkyl–Aryl Coupling

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      Iron-Catalyzed Coupling of Aryl Grignard Reagents with Alkyl Halides: A Competitive Hammett Study (pages 11991–11993)

      Anna Hedström, Ulla Bollmann, Jenny Bravidor and Prof. Per-Ola Norrby

      Article first published online: 16 SEP 2011 | DOI: 10.1002/chem.201100467

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      Competing for electrophiles: The elusive iron-catalyzed C[BOND]C coupling reaction was investigated and analyzed by a Hammett study of the nucleophilic partner. This required finding conditions in which the iron catalyst is stable in the presence of an excess of the Grignard reagent. The selectivity-determining step seems to be the transmetalation, occurring either before or after the oxidative addition step (see scheme).

    7. Chemosensors

      A Molecular Probe for the Highly Selective Chromogenic Detection of DFP, a Mimic of Sarin and Soman Nerve Agents (pages 11994–11997)

      Raúl Gotor, Prof. Ana M. Costero, Dr. Salvador Gil, Dr. Margarita Parra, Prof. Ramón Martínez-Máñez and Dr. Félix Sancenón

      Article first published online: 16 SEP 2011 | DOI: 10.1002/chem.201102241

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      Lethal-weapon visualization: A novel triarylmethanol derivative, which is able to colorimetrically distinguish diisopropylfluorophosphate (DFP; a mimic of Sarin and Soman) from other nerve-agent simulants, is reported (see picture). This probe was designed to contain two reactive sites: an OH group that provides a suitable reactive group for nerve agents and a tert-butyldimethylsilylether moiety that is able to react with fluoride, which is a specific byproduct of the phosphorylation of OH by DFP.

    8. Cooperative Catalysis

      Direct Catalytic Asymmetric Intramolecular Conjugate Addition of Thioamide to α,β-Unsaturated Esters (pages 11998–12001)

      Yuta Suzuki, Ryo Yazaki, Dr. Naoya Kumagai and Prof. Dr. Masakatsu Shibasaki

      Article first published online: 20 SEP 2011 | DOI: 10.1002/chem.201102332

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      Proton transfer allows efficient access to optically active five- and six-membered ring systems bearing ester and thioamide functionalities in an anti fashion; these ring systems are amenable to differential functional group manipulation. Direct catalytic, asymmetric, intramolecular conjugate addition of thioamide to α,β-unsaturated esters is described. In situ generated Cu thioamide enolate, by catalytic deprotonation, underwent the conjugate addition/protonation, to achieve the complete transformation (see scheme).

    9. Hybrid Materials

      Single-Side Organically Functionalized Anderson-Type Polyoxometalates (pages 12002–12005)

      Pingfan Wu, Panchao Yin, Dr. Jin Zhang, Dr. Jian Hao, Dr. Zicheng Xiao and Prof. Dr. Yongge Wei

      Article first published online: 19 SEP 2011 | DOI: 10.1002/chem.201101552

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      An unprecedented single-side trisalkoxo-substituted Anderson-type polyoxometalate (POM) was synthesized (see scheme). As confirmed by single-crystal X-ray diffraction and IR analyses, the single-side-functionalized Anderson-type POM forms interesting supramolecular assemblies, including dimers and 1D chains.

    10. Bolaamphiphiles

      Buildup of Amphiphilic Molecular Bola from Organic–Inorganic Hybrid Polyoxometalates and Their Vesicle-Like Supramolecular Assembly (pages 12006–12009)

      Dr. Fengping Xiao, Dr. Mauricio F. Misdrahi, Dr. Jin Zhang, Panchao Yin, Dr. Jian Hao, Chunlin Lv, Dr. Zicheng Xiao, Prof. Dr. Tianbo Liu and Prof. Dr. Yonggei Wei

      Article first published online: 16 SEP 2011 | DOI: 10.1002/chem.201101966

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      Bisarylamines with o-alkoxy substituents [o-NH2-C6H4-O(CH2)1/2/3]2 react with [nBu4N]4[α-Mo8O26] in anhydrous acetonitrile in the presence of N,N′-dicyclohexylcarbodiimide (DCC) to form a series of nanoscale molecular bola, bisorganoimido-bridged hexamolybdates with flexible alterable lengths, in which two hexamolybdate cages are connected by the bisarylimido linkers (see scheme).

    11. Polyoxometalates

      Investigating Cation Binding in the Polyoxometalate-Super-Crown [P8W48O184]40− (pages 12010–12014)

      Thomas Boyd, Dr. Scott G. Mitchell, David Gabb, Dr. De-Liang Long and Prof. Leroy Cronin

      Article first published online: 26 SEP 2011 | DOI: 10.1002/chem.201101666

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      An adaptable polyoxometalate macrocycle: The crown-type polyoxometalate [P8W48O184]40− has been prepared in the absence of potassium to give two new mixed lithium/ammonium compounds, allowing cation binding within the heteropolyanion to be investigated. Characterization of binding sites in the {P8W48} cluster could enable prediction of reaction products and selective functionalization of internal and external binding sites.

    12. Enzyme Studies

      Fluorescence Lifetime Analysis of Nitrite Reductase from Alcaligenes xylosoxidans at the Single-Molecule Level Reveals the Enzyme Mechanism (pages 12015–12019)

      Dr. Leandro C. Tabares, Dorota Kostrz, Abdalmohsen Elmalk, Alessio Andreoni, Dr. Christopher Dennison, Prof. Dr. Thijs J. Aartsma and Prof. Dr. Gerard W. Canters

      Article first published online: 16 SEP 2011 | DOI: 10.1002/chem.201102063

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      Lighting the route: Immobilized, fluorescently labeled bacterial nitrite reductase (NiR) has been studied during steady-state turnover by using single-molecule fluorescence lifetime imaging spectroscopy. With this method, two populations of single NiR molecules exhibiting different turnover rates can be distinguished. The two populations are tentatively connected by two enzymatic routes: the reduction-first or the binding-first pathway (see picture).

  7. Full Papers

    1. Top of page
    2. Cover Picture
    3. Inside Cover
    4. Graphical Abstract
    5. News
    6. Concept
    7. Communications
    8. Full Papers
    9. Preview
    1. Self-Propelling Motors

      External-Energy-Independent Polymer Capsule Motors and Their Cooperative Behaviors (pages 12020–12026)

      Guanjia Zhao, Tzu Hui Seah and Prof. Martin Pumera

      Article first published online: 23 SEP 2011 | DOI: 10.1002/chem.201101450

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      Chemical shepherding: A millimeter-sized polymer capsule motor with specific features and functionalities runs without any external energy sources or the consumption of external fuels (see figure). Long-range interaction behaviors and surface-cleaning effects due to the chemotaxis effect are demonstrated when the capsule is functionalized with sodium dodecyl sulfate (SDS).

    2. Coke Inhibition

      Competitive Reactions of Organophosphorus Radicals on Coke Surfaces (pages 12027–12036)

      Dr. Saron Catak, Dr. Ir. Karen Hemelsoet, Dr. Laura Hermosilla , Prof. Dr. Michel Waroquier and Prof. Dr. Ir. Veronique Van Speybroeck

      Article first published online: 28 SEP 2011 | DOI: 10.1002/chem.201100712

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      Don't coke so much! Calculations on a series of organophosphorus additives and their effects on coking—an undesirable process that occurs in cracking units—showed preferred radical attack at the periphery of the polyaromatic hydrocarbon ovalene (see picture), which was used to mimic the graphene-like coke surface. Thus, coke-inhibiting agents work by blocking the peripheral sites that are essential for coke growth.

    3. Peptidomimetics

      Exercises in Pyrrolidine Chemistry: Gram Scale Synthesis of a Pro–Pro Dipeptide Mimetic with a Polyproline Type II Helix Conformation (pages 12037–12044)

      Dipl.-Chem. Cédric Reuter, Dr. Peter Huy, Dr. Jörg-Martin Neudörfl, Dr. Ronald Kühne and Prof. Dr. Hans-Günther Schmalz

      Article first published online: 7 SEP 2011 | DOI: 10.1002/chem.201101704

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      Proline, proline: A practical total synthesis of a tricyclic diproline analogue locked in a polyproline type II conformation was elaborated. The required vinylproline building blocks were prepared from proline in only five and six steps, respectively. The title compound serves as a module for the synthesis of small molecules specifically interfering with protein–protein interactions involving so-called PRDs (proline-rich domains).

    4. Redox Bistability

      A New Route towards Redox Bistability through the Inspection of Manganese–Porphyrin Complexes (pages 12045–12050)

      Dr. Mikaël Kepenekian, Dr. Valentina Vetere, Dr. Boris Le Guennic, Dr. Pascale Maldivi and Prof. Vincent Robert

      Article first published online: 13 SEP 2011 | DOI: 10.1002/chem.201101184

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      Pyramid scheme: The ab initio inspection of manganese–porphyrin complexes leads to the proposition of a new ‘triangular scheme’ for redox bistability (see scheme) based on a valence tautomerism-like step that involves an MnIII ion and a porphyrin radical.

    5. Platinum(IV) Complexes

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      Insights into the Acid–Base Properties of PtIV–Diazidodiam(m)inedihyroxido Complexes from Multinuclear NMR Spectroscopy (pages 12051–12058)

      Dr. Luca Ronconi, Dr. Ana M. Pizarro, Ruth J. McQuitty and Prof. Dr. Peter J. Sadler

      Article first published online: 16 SEP 2011 | DOI: 10.1002/chem.201002792

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      Which sites can (de)protonate? The acid–base properties of photoactivable platinum(IV) anticancer complexes have been investigated by multinuclear NMR methods and potentiometry; the pKa of approximately 3.4 can be assigned to the hydroxido ligands, but the second inflexion point at a pH of about 7.5 does not appear to involve net proton dissociation.

    6. NMR Spectroscopy

      Probing Platinum Azido Complexes by 14N and 15N NMR Spectroscopy (pages 12059–12066)

      Dr. Nicola J. Farrer, Dr. Peter Gierth and Prof. Dr. Peter J. Sadler

      Article first published online: 16 SEP 2011 | DOI: 10.1002/chem.201101409

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      A tale of two isotopes: 15N and 14N NMR spectroscopies provide insight into the structure and bonding within PtIV azido anticancer complexes. 15N-labelling allows rapid detection of azide signals despite no adjacent protons, and 14N NMR spectra reveal exceptionally broad signals for the coordinated azide nitrogen, a result of highly asymmetric field gradients (see figure). Analysis of the 1J(15N,195Pt) coupling constants reveals that N3 has a moderately strong trans influence, intermediate between that of Cl and NO2.

    7. Helical Structures

      A Rational Design for the Directed Helicity Change of Polyacetylene Using Dynamic Rotaxane Mobility by Means of Through-Space Chirality Transfer (pages 12067–12075)

      Fumitaka Ishiwari, Kei-ichiro Fukasawa, Dr. Takashi Sato, Dr. Kazuko Nakazono, Dr. Yasuhito Koyama and Prof. Toshikazu Takata

      Article first published online: 16 SEP 2011 | DOI: 10.1002/chem.201101727

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      Twisted logic: The rational transformation of the helical structure of polyacetylene was achieved by controlling the position of the optically active wheel on the side chain (see picture). Polymers with optically active wheel components that are far from the main chain form racemic helices. When the wheel components approach the main chain, polymers form a one-handed helix.

    8. Metal–Organic Frameworks

      Co3(HCOO)6 Microporous Metal–Organic Framework Membrane for Separation of CO2/CH4 Mixtures (pages 12076–12083)

      Xiaoqin Zou, Feng Zhang, Dr. Sebastien Thomas, Prof. Dr. Guangshan Zhu, Prof. Dr. Valentin Valtchev and Dr. Svetlana Mintova

      Article first published online: 16 SEP 2011 | DOI: 10.1002/chem.201101733

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      Out of gas: Continuous Co3(HCOO)6 microporous metal–organic framework (MOF) membranes are prepared by a secondary growth approach. The MOF membranes with zigzag channels exhibit a higher permeation flux and excellent selectivity for CO2 over CH4 due to their effective pore size and shape (see picture).

    9. Drug Delivery

      Graphene Oxide Noncovalent Photosensitizer and Its Anticancer Activity In Vitro (pages 12084–12091)

      Dr. Lin Zhou, Wei Wang, Jing Tang, Prof. Dr. Jia-Hong Zhou, Prof. Dr. Hui-Jun Jiang and Prof. Dr. Jian Shen

      Article first published online: 13 SEP 2011 | DOI: 10.1002/chem.201003078

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      Delivery service: A hybrid of functionalized graphene oxide (GO) and hypocrellin A (HA) has been prepared (see picture) and exploited as a drug-delivery system of HA. The complex has obvious photodynamic activity in vitro: cell and nuclear morphological changes in impregnated tumor cells were observed upon irradiation by light.

    10. Gas-Phase Chemistry

      Biomimetic Oxidation Reactions of a Naked Manganese(V)–Oxo Porphyrin Complex (pages 12092–12100)

      Dr. Francesco Lanucara and Prof. Maria Elisa Crestoni

      Article first published online: 8 SEP 2011 | DOI: 10.1002/chem.201101432

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      Revealing the hidden scenario: New insight into the reactivity of bare [(tpfpp)MnVO]+ ions (tpfpp=meso-tetrakis(pentafluorophenyl)porphinato dianion) with substrates (L) containing a heteroatom (e.g., amines, sulfides, phosphites) is obtained by ESI-FT-ICR mass spectrometry. The reaction pathways are initiated by electron transfer and yield products involving O-atom coupling and transfer, besides hydride transfer (see scheme).

    11. Metallocenophanes

      Sterically Demanding Hetero-Substituted [2]Borametallocenophanes of Group IV Metals: Synthesis, Structure and Reactivity (pages 12101–12107)

      Prof. Dr. Holger Braunschweig, Dr. Rainer Dörfler, Jan Mies and Dr. Andreas Oechsner

      Article first published online: 9 SEP 2011 | DOI: 10.1002/chem.201101774

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      Two to tango: The synthesis and characterisation of unprecedented, unstrained [2]diborametallocenophanes of zirconium and hafnium that bear the bulky octamethylfluorenyl (η5-C29H36) system (see figure) is reported, the proligands of which were pre-constructed by a two-step synthesis. Typical reactivities relevant to olefin polymerisation were also investigated.

    12. Supramolecular Chirality

      Left or Right? The Direction of Compression-Generated Vortex-Like Flow Selects the Macroscopic Chirality of Interfacial Molecular Assemblies (pages 12108–12114)

      Dr. Penglei Chen, Xiaoguang Ma, Kaiming Hu, Yunlong Rong and Prof. Dr. Minghua Liu

      Article first published online: 9 SEP 2011 | DOI: 10.1002/chem.201101322

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      Left or right? The macroscopic chiralities of interfacially organized molecular assemblies of an achiral porphyrin, formulated by a horizontal lifting method through an original Langmuir–Blodgett technique, have been found to be well selected by the direction of the compression-generated vortex-like flow (see picture).

    13. Organocalcium Chemistry

      Calcium-Mediated Dearomatization, C[BOND]H Bond Activation, and Allylation of Alkylated and Benzannulated Pyridine Derivatives (pages 12115–12122)

      Phillip Jochmann, Valeri Leich, Dr. Thomas P. Spaniol and Prof. Dr. Jun Okuda

      Article first published online: 9 SEP 2011 | DOI: 10.1002/chem.201101489

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      Calciation of pyridines: Bis(allyl)calcium [Ca(C3H5)2] reacts with a variety of alkylated (2-picoline, 4-picoline, 2,6-lutidine, 4-tert-butylpyridine, 2,2′-bipyridine) and annulated (acridine, quinoline, isoquinoline) pyridine derivatives under either C[BOND]H bond activation or carbometalation (see picture). The regioselective reactions proceed in essentially quantitative yields.

    14. Dendrimers

      Autoinductive Exponential Signal Amplification: A Diagnostic Probe for Direct Detection of Fluoride (pages 12123–12128)

      Dr. Rotem Perry-Feigenbaum, Eran Sella and Prof. Doron Shabat

      Article first published online: 9 SEP 2011 | DOI: 10.1002/chem.201101796

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      Probing questions: A new example of an exponential signal amplification strategy for direct detection of fluoride is demonstrated. The amplification occurred through reaction of fluoride with a responsive chromogenic probe (see picture). The probe activity is based on a unique dendritic chain reaction that generates a fluoride anion during the disassembly pathway of the dendritic probe.

    15. Dehydrogenation

      Surface-Inspired Molecular Vanadium Oxide Catalysts for the Oxidative Dehydrogenation of Alcohols: Evidence for Metal Cooperation and Peroxide Intermediates (pages 12129–12135)

      C. Gunnar Werncke, Prof. Dr. Christian Limberg, Dr. Christina Knispel and Dr. Stefan Mebs

      Article first published online: 13 SEP 2011 | DOI: 10.1002/chem.201101442

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      Oxidovanadium thiobisphenolates were investigated as molecular model compounds for surface species proposed to be present on supported V2O5 catalysts for the oxidative dehydrogenation (ODH) of alkanes and methanol (see scheme). Mechanistic and kinetic studies on these compounds provide valuable insights into potential surface reactivity.

    16. Computational Chemistry

      Oxidation State Changes and Electron Flow in Enzymatic Catalysis and Electrocatalysis through Wannier-Function Analysis (pages 12136–12143)

      Dr. Patrick H.-L. Sit, Dr. Federico Zipoli, Jia Chen, Prof. Roberto Car, Dr. Morrel H. Cohen and Prof. Annabella Selloni

      Article first published online: 9 SEP 2011 | DOI: 10.1002/chem.201101916

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      Revealing the intimate details: Wannier centers and Wannier functions reveal details of bonding configurations and oxidation states (see figure for an example) and their changes during chemical reactions. They are a powerful tool for unraveling reaction mechanisms by first-principles computations. Two catalytic systems were investigated, the enzyme superoxide reductase and the H2-producing catalyst [FeFe]p.

    17. Ion Channels

      Synthesis of Skeletal Analogues of Saxitoxin Derivatives and Evaluation of Their Inhibitory Activity on Sodium Ion Channels NaV1.4 and NaV1.5 (pages 12144–12152)

      Ryoko Shinohara, Takafumi Akimoto, Dr. Osamu Iwamoto, Dr. Takatsugu Hirokawa, Prof. Dr. Mari Yotsu-Yamashita, Prof. Dr. Kaoru Yamaoka and Prof. Dr. Kazuo Nagasawa

      Article first published online: 16 SEP 2011 | DOI: 10.1002/chem.201101058

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      Skeleton crew: Newly synthesized fused-type skeletal analogues of saxitoxins, (−)-FD-STX and (−)-FD-dcSTX, inhibited sodium ion channels NaV1.4 and NaV1.5, whereas (−)-FD-doSTX was inactive (see scheme). Uniquely, inhibition of NaV1.5 by (−)-FD-dcSTX was “irreversible”.

    18. Phosphaalkenes

      Acetylene-Expanded Dendralene Segments with Exotopic Phosphaalkene Units (pages 12153–12162)

      Dr. Xue-Li Geng and Prof. Sascha Ott

      Article first published online: 14 SEP 2011 | DOI: 10.1002/chem.201101358

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      Pretty heavy! Bis-TMS-protected, C,C-diacetylenic phosphaalkene has been used for the construction of butadiyne-expanded dendralene fragments in which a heavier main-group element features in the exotopic double bonds (see scheme). The P centers contribute considerably to the frontier molecular orbitals of the compounds, which leads to smaller HOMO–LUMO gaps than all-carbon-based congeners.

    19. Buckybelts

      Evidence for Fully Conjugated Double-Stranded Cycles (pages 12163–12174)

      Dr. Malte Standera, Rolf Häfliger, Renana Gershoni-Poranne, Prof. Amnon Stanger, Prof. Gunnar Jeschke, Dr. Jacco D. van Beek, Louis Bertschi and Prof. A. Dieter Schlüter

      Article first published online: 14 SEP 2011 | DOI: 10.1002/chem.201100443

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      Beyond reasonable doubt! The double-stranded, fully conjugated cycle shown can be generated in a mass spectrometer and possibly even in solution. It is concluded that the fully aromatic targets truly exist in the gas phase. Whether they can be generated in solution under the applied conditions cannot yet be firmly decided; theoretical evidence suggests not.

    20. Helicenes, Chrysenes, and Fluorenes

      Domino Friedel–Crafts-Type Cyclizations of Difluoroalkenes Promoted by the α-Cation-Stabilizing Effect of Fluorine: An Efficient Method for Synthesizing Angular PAHs (pages 12175–12185)

      Dr. Kohei Fuchibe, Hideharu Jyono, Dr. Masaki Fujiwara, Takao Kudo, Dr. Misaki Yokota and Prof. Dr. Junji Ichikawa

      Article first published online: 16 SEP 2011 | DOI: 10.1002/chem.201100618

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      Nonlinear aromatics: Domino cyclizations of 1,1-difluoroalkenes were studied with the goal of synthesizing nonlinear polycyclic aromatic hydrocarbons (angular PAHs). Carbocations produced from 1,1-difluoroalk-1-enes bearing two aryl substituents afforded helicenes and other PAHs. 1,1-Difluoroalka-1,3-dienes afforded helicene and benzofluorene derivatives in high yields in the presence of milder acids such as CSA and TfOH.

    21. Synthetic Methods

      Zinc-Catalyzed Chemoselective Reduction of Tertiary and Secondary Amides to Amines (pages 12186–12192)

      Shoubhik Das, Dr. Daniele Addis, Dr. Kathrin Junge and Prof. Dr. Matthias Beller

      Article first published online: 13 SEP 2011 | DOI: 10.1002/chem.201101143

      Thumbnail image of graphical abstract

      What are you zincing about? A general and chemoselective catalytic reduction of amides to amines using inexpensive zinc catalysts has been developed. In the presence of inexpensive zinc catalysts, tertiary amides are easily reduced by applying monosilanes, whereas for the reduction of the secondary amides, zinc triflate and disilanes with dual Si[BOND]H moieties are used (see scheme).

    22. Directed Glycosylation

      Neighboring-Group Participation by C-2 Ether Functions in Glycosylations Directed by Nitrile Solvents (pages 12193–12202)

      Dr. Chin-Sheng Chao, Ching-Yu Lin, Shaheen Mulani, Wei-Cheng Hung and Prof. Dr. Kwok-kong Tony Mong

      Article first published online: 14 SEP 2011 | DOI: 10.1002/chem.201100732

      Thumbnail image of graphical abstract

      Highly selective: C-2 ether-protecting functions have been found to play participating roles in glycosylations when the reactions are conducted in alkyl nitrile solvent mixtures (see scheme). The mechanism involves a Ritter-like interaction of the C-2 ether oxygen with an alkyl nitrile molecule. Together with the anomeric effect, this results in a high 1,2-trans selectivity in glycosylations and in an efficient preparation of α-(1[RIGHTWARDS ARROW]5)-arabinan oligomers.

    23. Reductive Coupling

      Triflic Acid Catalyzed Reductive Coupling Reactions of Carbonyl Compounds with O-, S-, and N-Nucleophiles (pages 12203–12209)

      Dipl.-Chem. Beate A. Gellert, Dipl.-Chem. Nils Kahlcke, Dipl.-Chem. Markus Feurer and Dr. Stefanie Roth

      Article first published online: 16 SEP 2011 | DOI: 10.1002/chem.201101819

      Thumbnail image of graphical abstract

      One does it all: Highly efficient metal-free reductive coupling reactions of aldehydes and ketones with a range of nucleophiles in the presence of triflic acid (1–5 mol %) as the catalyst are presented (see picture). The reactions can be performed at ambient temperature without exclusion of moisture or air. A range of symmetrical and unsymmetrical ethers, as well as thioethers and sulfonamides, were obtained in high yields and short reaction times.

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      Preview: Chem. Eur. J. 44/2011 (page 12211)

      Article first published online: 11 OCT 2011 | DOI: 10.1002/chem.201190214

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