bluuebunny/crossref_metadata_2025 huggingface dataset:
Exploiting the Divergent Reactivity of Aryl–Palladium Intermediates for the Rapid Assembly of Fluorene and Phenanthrene Derivatives
Authors: Zhao Ya‐Bin , Mariampillai Brian , Candito David A. , Laleu Benoît , Li Mengzhou , Lautens Mark
Published: January 2009

Enorm steigern lässt sich der Nutzen von Dominoprozessen, wenn ausgehend von einem gemeinsamen Intermediat eine selektive Gabelung möglich ist. Hier werden erste Untersuchungen zur dualen Reaktivität von Aryl‐Palladium‐Intermediaten beschrieben. Eine Vielzahl an Fluoren‐ und Phenanthrenderivaten wurde schnell und effizient erhalten (siehe Schema).

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Fast Biosynthesis of GFP Molecules: A Single‐Molecule Fluorescence Study
Authors: Katranidis Alexandros , Atta Diaa , Schlesinger Ramona , Nierhaus Knud H. , Choli‐Papadopoulou Theodora , Gregor Ingo , Gerrits Michael , Büldt Georg , Fitter Jörg
Published: January 2009

Grün sein ist nicht einfach: Die Echtzeit‐Visualisierung markierter Ribosomen und de‐novo‐synthetisierter grün fluoreszierender Proteinmoleküle mithilfe einzelmolekülempfindlicher Fluoreszenzmikroskopie ergibt, dass die Mutante GFPem charakteristischerweise innerhalb von fünf Minuten produziert wird. Die Fluoreszenz der schnellsten GFP‐Moleküle erscheint innerhalb einer Minute (siehe Bild).

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Cobalt Growth on the Tips of CdSe Nanorods
Authors: Maynadié Jérôme , Salant Asaf , Falqui Andrea , Respaud Marc , Shaviv Ehud , Banin Uri , Soulantica Katerina , Chaudret Bruno
Published: January 2009

Best of both worlds: Reduction of an organometallic Co precursor on preformed CdSe nanorods yields two distinct semiconducting–magnetic heterostructures (see picture). The selective growth of Co on the tips of CdSe first gives nanosphere–nanorod dimers, which evolve into nanorod–nanorod structures. In the hybrid objects the magnetic properties of Co remain intact, while the luminescence properties of CdSe are affected but not completely quenched.

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Protein Recognition by an Ensemble of Fluorescent DNA G‐Quadruplexes
Authors: Margulies David , Hamilton Andrew D.
Published: January 2009

Sniffing out proteins: Fluorescent DNA G‐quadruplexes have been used for building versatile signaling receptors for proteins in a single solution. Introducing a protein sample to the ensemble results in a unique emission signature for unambiguous identification (see scheme, R=fluorophore). The self‐assembled, pattern‐based protein detection systems are easily fabricated, have the potential for high‐throughput operations, and have the ability to handle small protein samples.

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Drug Delivery by an Enzyme‐Mediated Cyclization of a Lipid Prodrug with Unique Bilayer‐Formation Properties
Authors: Linderoth Lars , Peters Günther H. , Madsen Robert , Andresen Thomas L.
Published: January 2009

Special delivery: Liposomal drug‐delivery systems in which prodrugs are activated specifically by disease‐associated enzymes have great potential for the treatment of severe diseases, such as cancer. A new type of phospholipid‐based prodrug has the ability to form stable small unilamellar vesicles (see picture). Activation of the prodrug vesicles by the enzyme sPLA2 initiates a cyclization reaction, which leads to the release of the drug.

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Catalytic, Enantioselective Ring Opening of Aziridines
Authors: Schneider Christoph
Published: January 2009

Cooperative metal centers in a bimetallic catalyst facilitate the highly enantioselective ring opening of meso aziridines 1 with silyl nucleophiles (see scheme; TMS=trimethylsilyl). The 1,2‐azidoamides 2 and 1,2‐amidonitriles 3 obtained in this way in high yields and with up to 99 % ee are valuable precursors to enantiomerically pure 1,2‐diamines and β‐amino acids.

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Highly Proton‐Conducting Self‐Humidifying Microchannels Generated by Copolymer Brushes on a Scaffold
Authors: Yameen Basit , Kaltbeitzel Anke , Langer Andreas , Müller Frank , Gösele Ulrich , Knoll Wolfgang , Azzaroni Omar
Published: January 2009

Filling in the gaps: Macroporous silicon membranes modified with sulfonated polymer brushes have been synthesized by pore‐filling surface polymerization (see picture) to give proton‐conducting channels with tailor‐made, finely tuned physicochemical characteristics. These membranes display high conductivity values (ca. 10−2 S cm−1) regardless of the humidity, thus surpassing the performance of nafion.

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Responsive Supramolecular Gels Constructed by Crown Ether Based Molecular Recognition
Authors: Ge Zhishen , Hu Jinming , Huang Feihe , Liu Shiyong
Published: January 2009

Responsive supramolecular gels were constructed from crown ether terminated four‐arm star poly(ε‐caprolactone) (PCL–DB24C8) and dibenzylammonium‐terminated two‐arm PCL–DBAS (see scheme), exploiting the formation of pseudorotaxane linkages between crown ether and ammonium moieties. The resultant supramolecular gels exhibit thermo‐ and pH‐induced reversible gel–sol transition.

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Exploiting the Divergent Reactivity of Aryl–Palladium Intermediates for the Rapid Assembly of Fluorene and Phenanthrene Derivatives
Authors: Zhao Ya‐Bin , Mariampillai Brian , Candito David A. , Laleu Benoît , Li Mengzhou , Lautens Mark
Published: January 2009

They all fall down: The value of domino processes can be greatly enhanced when the possibility exists for one to selectively diverge from a common intermediate. In preliminary studies the dual reactivity of aryl–palladium intermediates is exploited. A diverse array of fluorene and phenanthrene derivatives were synthesized in a rapid and efficient manner (see scheme).

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Fast Biosynthesis of GFP Molecules: A Single‐Molecule Fluorescence Study
Authors: Katranidis Alexandros , Atta Diaa , Schlesinger Ramona , Nierhaus Knud H. , Choli‐Papadopoulou Theodora , Gregor Ingo , Gerrits Michael , Büldt Georg , Fitter Jörg
Published: January 2009

It's not easy being green: Real‐time visualization of labeled ribosomes and de novo synthesized green fluorescent protein molecules using single‐molecule‐sensitive fluorescence microscopy demonstrates that the mutant GFPem is produced with a characteristic time of five minutes. Fluorescence of the fastest GFP molecules appears within one minute (see picture).

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Cover Picture: Microcontainers with Fluorescent Anisotropic Zeolite L Cores and Isotropic Silica Shells (Angew. Chem. Int. Ed. 7/2009)
Authors: Guerrero‐Martínez Andrés , Fibikar Sandra , Pastoriza‐Santos Isabel , Liz‐Marzán Luis M. , De Cola Luisa
Published: January 2009

Nanocontainers composed of zeolite L crystals were filled with fluorescent dyes and used as the core of a silica “box‐in‐a‐box” construction as in Russian matryoshka dolls, as described by A. Guerrero‐Martínez, L. de Cola, and co‐workers in their Communication on page 1266 ff. The anisotropic cores and isotropic shells of the multicolor emitting systems are separated by a polyelectrolyte layer and can be addressed independently. This approach opens fascinating routes for the construction of multifunctional nanosystems.

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Inside Cover: Self‐Assembly of One‐ and Two‐Dimensional Hemoprotein Systems by Polymerization through Heme–Heme Pocket Interactions (Angew. Chem. Int. Ed. 7/2009)
Authors: Kitagishi Hiroaki , Kakikura Yasuaki , Yamaguchi Hiroyasu , Oohora Koji , Harada Akira , Hayashi Takashi
Published: January 2009

Supramolecular protein polymers consisting of cytochrome b562 monomers with heme covalently attached to the protein surface are presented by T. Hayashi and co‐workers in their Communication on page 1271 ff. Not only one‐dimensional hemoprotein fibers with submicrometer lengths have been prepared, but when a heme triad was added as a pivot molecule, two‐dimensional protein assembly networks resulted, which cover over 100 square micrometers.

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Effect of hot air aging on the properties of ethylene‐vinyl acetate copolymer and ethylene‐acrylic acid copolymer blends
Authors: Chen Shuangjun , Zhang Jun , Su Jun
Published: January 2009

The aim of this investigation is to evaluate the effect of hot air aging on properties of ethylene‐vinyl acetate copolymer (EVA, 14 wt % vinyl acetate units), ethylene‐acrylic acid copolymer (EAA, 8 wt % acrylic acid units), and their blends. Attenuated total reflection‐Fourier transform infrared spectroscopy, differential scanning calorimeter (DSC), wide angle X‐ray diffraction, and mechanical tests are employed to investigate the changes of copolymer blends' structures and properties. Increase of carbonyl index derived from ATR measurements with aging time suggests the incorporation of oxygen into the polymeric chain. By DSC measurements, the enthalpy at low temperature endothermic peak (Tm2) of EAA becomes less and disappears after 8 weeks aging, but enthalpy at Tm2 of EVA is not influenced by the hot air aging and remains stable despite of the aging time. For various proportions of EAA and EVA blends, enthalpy at Tm2 decreases as the EAA proportion increases when aging time is 8 weeks; after several weeks of hot air aging, the various blends appear a same new peak just over the aging temperature 70°C which is due to the completion of crystals which are not of thermodynamic equilibrium state. Mechanical tests show that increase of crystallinity and hot air aging deterioration both have influence on the hardness, tensile strength, and elongation at break. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Chain extension reactions of unsaturated polyesters with epoxy compounds
Authors: Taylan E. , Küsefoğlu S. H.
Published: January 2009

Unsaturated polyesters (UPE) were chain extended with three different epoxy group containing compounds. The molecular weight increase was monitored using gel permeation chromatography (GPC). The polymers obtained were characterized by FTIR and 1H NMR, and styrene solubility and gel time. The polyesters were then diluted with styrene and cured with a radical initiator and compared with a commercial reference polyester. Thermal and mechanical properties of the cured polyesters were characterized by dynamic mechanical analysis (DMA) and thermal gravimetric analysis (TGA). The results show that UPE can be chain extended with epoxy containing compounds which substantially shortens the condensation polymerization during manufacture, without compromising their thermal and mechanical properties. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Mechanisms of molecular interactions in polybase–polyacid complex formed by copolymers of N,N‐dimethylaminoethylmethacrylate with alkylmethacrylates and methacrylic acid with ethylacrylate
Authors: Feldstein Mikhail M. , Kiseleva Tatiana I. , Bondarenko Galina N. , Kostina Julia V. , Singh Parminder , Cleary Gary W.
Published: January 2009

Mechanisms of molecular interaction in the blends of a polybase, a copolymer of N,N‐dimethylaminoethylmethacrylate with methylmethacrylate and butylmethacrylate (PDMAEMA–MMA/BMA), with a polyacid, a copolymer of methacrylic acid with ethylacrylate (PMAA‐co‐EA), and plasticizer, triethylcitrate (TEC), have been investigated with FTIR Spectroscopy and potentiometry. To evaluate the strengths of hydrogen and ionic bonds in the polyelectrolyte complexes, quantum‐chemical calculations were performed. According to this analysis, the energy of ionic and hydrogen bonding diminishes in the order: multi‐component complexes involving protonated aminogroup of DMAEMA (ammonium cation) in the presence of chlorine counterion with ionized or unchanged carboxyl groups and water molecules (690–520 kJ/mol) > ternary H‐bonded acid‐base complexes associated with molecule of water (520–420 kJ/mol) > binary ionic complex of carboxylate anion and ammonium cation (404 kJ/mol) > H‐bonded complex of carboxylate and ammonium ions (257 kJ/mol) > binary H‐bonded complex of uncharged carboxyl group with ammonium cation (114 kJ/mol) > ternary H‐bonded complex of uncharged carboxyl group, aminogroup and water molecule (43 kJ/mol) > binary H‐bonded complex between nonionized carboxyl and amino groups (26 kJ/mol). Proton‐donating capability of functional groups in the studied polyelectrolyte blends diminishes in the order: HN+(CH3)2 − > HOOC > HO. The proton‐donating capacity can be significantly improved in the presence of Cl− ions, the effect of which may be appreciably inhibited if Na+ cations are available in the blend or solution. Proton‐accepting capability weakens in the order: uncharged aminogroup > carboxylate anion > uncharged carboxyl group > hydroxyl group. The results of quantum chemical calculations facilitate interpretation of FTIR spectra. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Thermal and mechanical properties of cast polyurethane resin based on soybean oil
Authors: Wang Chengshuang , Yang Liting , Ni Baolian , Wang Linyun
Published: January 2009

The soy polyols were prepared from epoxidation of soybean oil followed by ring opening of oxirane obtained by using methanol as the ring opener. Polyols of hydroxyl (OH) numbers ranging from 128 to 174 mg of KOH/g were obtained by the variation of epoxidation time of soybean oil. A novel cast polyurethane resin has been synthesized by these polyols and 2,4‐toluene diisocyanate. Swelling of networks in toluene showed that the sol fraction varies from 1.13 to 72.06%. The thermal and mechanical properties of cast resins were characterized by differential scanning calorimetry and thermogravimetric analysis. The results showed that the glass transition temperature increases with the increase of OH number and that the thermal stability of the resins was slightly decreased with the increasing OH number. The tensile strength at break increases with the increase of OH number. Polyols with OH number of 174 mg of KOH/g gave glassy polymers, whereas those below this value gave rubbers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Combined effect of shear and nucleating agent on the multilayered structure of injection‐molded bar of isotactic polypropylene
Authors: Cao Jing , Wang Ke , Cao Wen , Zhang Qin , Du RongNi , Fu Qiang
Published: January 2009

Molten polymers are usually exposed to varying levels of shear flow and temperature gradient in most processing operations. Many studies have revealed that the crystallization and morphology are significantly affected under shear. A so‐called “skin‐core” structure is usually formed in injection‐molded semicrystalline polymers such as isotactic polypropylene (iPP) or polyethylene (PE). In addition, the presence of nucleating agent has great effect on the multilayered structure formed during injection molding. To further understand the morphological development in injection‐molded products with nucleating agent, iPP with and without dibenzylidene sorbitol (DBS) were molded via both dynamic packing injection molding (DPIM) and conventional injection molding. The structure of these injection‐molded bars was investigated layer by layer via SEM, DSC, and 2 days‐WAXD. The results indicated that the addition of DBS had similar effect on the crystal size and its distribution as shear, although the later decreased the crystal size more obviously. The combination of shear and DBS lead to the formation of smaller spherulites with more uniform size distribution in the injection‐molded bars of iPP. A high value of c‐axis orientation degree in the whole range from the skin to the area near the core center was obtained in the samples molded via DPIM with or without DBS, while in samples obtained via conventional injection molding, the orientation degree decreased gradually from the skin to the core and the decreasing trend became more obvious as the concentration of DBS increased. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Synthesis and In‐Vitro Cytotoxicity Evaluation of Novel Naphtindolizinedione Derivatives, Part II: Improved Activity for Aza‐Analogues
Authors: Defant Andrea , Guella Graziano , Mancini Ines
Published: January 2009

Our previous investigation on potential antitumor agents now got enriched by the evaluation of in‐vitro activity against a full panel of NCI cancer cell lines for five new compounds. The concurrent presence in the molecular structure of a nitrogen atom in the aromatic system and a N,N‐dimethylaminoethyl amide chain play a decisive role to enhance cytotoxicity. The N,N‐anti compound 14 shows a higher activity than its N,N‐syn isomer, exhibiting the best selective inhibition against the melanoma MALME‐3M cell line, with a GI50‐value (= 30 nM) corresponding to a 330‐fold increase in activity compared to the corresponding deaza‐analogue. Compound 14 is efficiently synthesized by aminolysis of the ester obtained as a single regio‐isomer by an one‐pot three‐component procedure involving metal‐assisted cyclization under microwave irradiation conditions.
Context recognition for hierarchical text classification
Authors: Liu Rey‐Long
Published: January 2009

Information is often organized as a text hierarchy. A hierarchical text‐classification system is thus essential for the management, sharing, and dissemination of information. It aims to automatically classify each incoming document into zero, one, or several categories in the text hierarchy. In this paper, we present a technique called CRHTC (context recognition for hierarchical text classification) that performs hierarchical text classification by recognizing the context of discussion (COD) of each category. A category's COD is governed by its ancestor categories, whose contents indicate contextual backgrounds of the category. A document may be classified into a category only if its content matches the category's COD. CRHTC does not require any trials to manually set parameters, and hence is more portable and easier to implement than other methods. It is empirically evaluated under various conditions. The results show that CRHTC achieves both better and more stable performance than several hierarchical and nonhierarchical text‐classification methodologies.
Total Synthesis of (−)‐Spirangien A, an Antimitotic Polyketide Isolated from the Myxobacterium Sorangium Cellulosum
Authors: Paterson Ian , Findlay Alison D. , Noti Christian
Published: January 2009

A stereocontrolled total synthesis of the cytotoxic spiroacetal‐containing polyketide (−)‐spirangien A is described. This utilizes an aldol‐based strategy to construct a common stereotetrad intermediate that was elaborated into the spiroacetal core, followed by the introduction of the unstable pentaene‐containing side chain, performed with exclusion of light, using sequential Stille cross‐coupling reactions.

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An expedient first total synthesis of (−)‐spirangien A, a potent cytotoxic and antifungal polyketide of myxobacterial origin, is described. By using a common 1,3‐diol intermediate obtained by an efficient aldol‐reduction sequence for installation of the C15–C18 and C25–C28 stereotetrads and a reagent‐controlled boron aldol coupling followed by spiroacetalization, a highly convergent strategy was developed for construction of the elaborate spiroacetal core. Conversion of this advanced spiroacetal intermediate into (+)‐spirangien diene, obtained previously by controlled degradation of spirangien A, was then achieved by installation of the truncated side‐chain using an allylboration–Peterson sequence. The total synthesis of (−)‐spirangien A was then achieved by the controlled attachment of the unsaturated C1–C12 side‐chain, avoiding exposure to light. A Stork–Wittig olefination and double Stille cross‐coupling sequence was exploited to install the delicate conjugated pentaene chromophore featuring alternating (Z)‐ and (E)‐olefins, leading initially to the methyl ester of spirangien A, which proved significantly more stable than the corresponding free acid. Subsequent careful hydrolysis afforded (−)‐spirangien A, validating the relative and absolute configuration.
Translation and rotation movements of the mandible during mouth opening and closing
Authors: Mapelli Andrea , Galante Domenico , Lovecchio Nicola , Sforza Chiarella , Ferrario Virgilio F.
Published: January 2009

To assess the relative contribution of rotation and translation of the temporomandibular condyle‐disc assembly during opening and closing movements, free movements of maximum mouth opening and closing were recorded in healthy subjects (12 men, 14 women) using an optoelectronic three‐dimensional motion analyzer. For each subject, the displacement of the lower interincisal point, the path of the condylar reference point, the degree of rotation around the three orthogonal rotational axes, and the relative contribution of translation and rotation were calculated during all movement of mouth opening and closing. The distance covered by the interincisor point and the rotational angle about the transverse axis at maximum mouth opening were larger in men than in women, but the difference cancelled after correcting for mandibular radius in the sagittal plane; mandibular rotation was always larger than translation, but never approaching 100%; opening and closing translations were similar within sex, but their paths were longer in men than in women (P < 0.05); rotational angles around vertical and sagittal axes were negligible; the linear correlation between maximum mandibular opening and condylar translation was minor and not significant. In normal subjects, mouth opening and closing as modeled at the interincisor point was determined more by mandibular rotation than by translation, but in no occasion a pure rotation was found. The percentage rotation was not identical during mouth opening and closing; female and male paths were not totally coincident; no correlation between maximum mandibular opening and condylar translation was found. Clin. Anat. 22:311–318, 2009. © 2009 Wiley‐Liss, Inc.
Improvements in power system transient simulation by application of trigonometric trapezoidal rule
Authors: Hosseinian S. H.
Published: January 2009

This article describes a user‐friendly simulation program for teaching and modeling power system transient and power quality issues. The main reason for the development of the program is to provide students with a useable tool for gaining an intuitive feel for power system transient and power quality problems. Emphasis was consistently laid on the development, validation and application of software for transient studies. To this end the primary focus of the research was the development of a generally oriented program in the form of a single module which is able to simulate any arbitrary configuration of power system in the time domain. Apart from the main program, sub‐programs have been developed to derive the required data for transmission line, transformer, machine and other equipment parameters. A novel variety of trapezoidal integration (called trigonometric) has been used, it has accuracy and therefore speed advantages over ordinary trapezoidal integration. This method is compared with ordinary trapezoidal integration, backward Euler, Gear second order and Simpson. The comparison is based upon the error and the performance of each method as differentiator. At each step, the variables associated with the switches are checked and if any constraints are violated, the process backtracks to the time when the violation occurred and the node voltages and branch currents are calculated for this time instant. In order to reduce the simulation time the program accepts the branch currents and node voltages as initial conditions which allow the steady state to be reached in less time. © 2009 Wiley Periodicals, Inc. Comput Appl Eng Educ 18: 277–289, 2010; Published online in Wiley InterScience (www.interscience.wiley.com); DOI 10.1002/cae.20253
Domestic violence against women: Understanding social processes and women's experiences
Authors: Bostock Jan , Plumpton Maureen , Pratt Rebekah
Published: January 2009

The prevalence of domestic abuse against women has been estimated as high as one in four. The risk is particularly high for women who are younger, economically dependent, unemployed and with children. Research about the factors that maintain situations of abuse has generally focused separately on the coping strategies of women, barriers to leaving the relationship and the perpetrators' means of abuse. In this study we used a community psychology perspective to seek a broader understanding of what maintains situations of abuse, in order to suggest interventions in a rural County in the North of England. Twelve women who had experienced domestic abuse and had used voluntary sector services agreed to be interviewed about their experiences and the resources and strategies available to them. Using grounded theory we generated four themes: (1) Commonalities and contradictions in the experience of abuse; (2) living with abuse; (3) the response of systems reinforced or challenged the abuse and (4) dealing with abuse beyond the relationship. These findings illustrate how situations of domestic abuse can be prolonged by limited options available to victims for support and protection, and a lack of active public acknowledgement that domestic abuse is unacceptable. Copyright © 2009 John Wiley & Sons, Ltd.
Women's human rights violations: Cameroonian students' perceptions
Authors: Kassea Raul , Sakki Inari , Pirttilä‐Backman Anna‐Maija
Published: January 2009

Cameroonian university students (N = 666) assessed whether certain different societal positions that the law grants to women and men (the husband chooses the marital home, the husband wields parental power, a married woman cannot freely engage in trade, the husband administers his wife's personal property) and certain cultural practices (female genital mutilation, parents arranging their children's marriage) were seen as violations of women's human rights. Justifications for the choices were also analysed. Female genital mutilation was most often seen as a violation of women's human rights, and the husband selecting the marital home was least often seen as a violation. These differences were explained by cultural specificities. Women more often than men saw the cases as violations of rights. Respondents coming from the North saw the cases less often as violations of rights than respondents from other geocultural areas, which was in accordance with their previously observed higher collectivism. Copyright © 2009 John Wiley & Sons, Ltd.
“Helter‐Skelter‐Like” Perylene Polyisocyanopeptides
Authors: Schwartz Erik , Palermo Vincenzo , Finlayson Chris E. , Huang Ya‐Shih , Otten Matthijs B. J. , Liscio Andrea , Trapani Sara , González‐Valls Irene , Brocorens Patrick , Cornelissen Jeroen J. L. M. , Peneva Kalina , Müllen Klaus , Spano Frank C. , Yartsev Arkady , Westenhoff Sebastian , Friend Richard H. , Beljonne David , Nolte Roeland J. M. , Samorì Paolo , Rowan Alan E.
Published: January 2009

Exciton migration! Spectroscopic analyses and extensive molecular dynamics studies revealed a well‐defined 41 helix in which the perylene molecules (see figure) form four “helter‐skelter‐like” overlapping pathways along which excitons and electrons can rapidly migrate.

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We report on a combined experimental and computational investigation on the synthesis and thorough characterization of the structure of perylene‐functionalized polyisocyanides. Spectroscopic analyses and extensive molecular dynamics studies revealed a well defined 41 helix in which the perylene molecules form four “helter skelter‐like” overlapping pathways along which excitons and electrons can rapidly migrate. The well‐defined polymer scaffold stabilized by hydrogen bonding, to which the chromophores are attached, accounts for the precise architectural definition, and molecular stiffness observed for these molecules. Molecular‐dynamics studies showed that the chirality present in these polymers is expressed in the formation of stable right‐handed helices. The formation of chiral supramolecular structures is further supported by the measured and calculated bisignated Cotton effect. The structural definition of the chromophores aligned in one direction along the backbone is highlighted by the extremely efficient exciton migration rates and charge densities measured with Transient Absorption Spectroscopy.
B Values as a Sensitive Measure of Steric Effects
Authors: Ruzziconi Renzo , Spizzichino Sara , Lunazzi Lodovico , Mazzanti Andrea , Schlosser Manfred
Published: January 2009

Someone who says “A” should be prepared to also say “B”: In contrast to cyclohexane model‐based A values, biphenyl model‐derived B values are powerful tools to quantify steric repulsion in and conformational behavior of ortho‐substituted aromatic compounds.

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Torsional barriers of 15 ortho‐substituted biphenyls have been determined computationally using the B3LYP density functional and experimentally by variable‐temperature (“dynamic”) nuclear magnetic resonance. Taking advantage of the 3′‐isopropyldimethylsilyl group as a novel and superior diastereotopicity probe and tracking coalescence temperatures down to −173 °C (100 K), activation energies of aryl–aryl rotation as small as 5 kcal mol−1 can be assessed. The 2‐X/2′‐H repulsion increments thus derived are powerful parameters for rationalizing and predicting the conformational behavior of aromatic compounds carrying ortho substituents.
Enantioselective Friedel–Crafts Alkylation of Indoles with Alkylidene Malonates Catalyzed by N,N′‐Dioxide–Scandium(III) Complexes: Asymmetric Synthesis of β‐Carbolines
Authors: Liu Yanling , Shang Deju , Zhou Xin , Liu Xiaohua , Feng Xiaoming
Published: January 2009

An efficient catalytic asymmetric Friedel–Crafts alkylation of indoles with alkylidene malonates has been developed by using a chiral N,N′‐dioxide–Sc(OTf)3 complex as the catalyst (see scheme). Some optically active intermediates containing the indole skeleton have been synthesized, such as indolepropionic acid, tryptamines, and β‐carbolines. The coordination between the scandium atom and the chiral N,N′‐dioxide compound has been revealed by X‐ray structure analysis.

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Organocatalytic Domino Michael–Knoevenagel Condensation Reaction for the Synthesis of Optically Active 3‐Diethoxyphosphoryl‐2‐oxocyclohex‐3‐enecarboxylates
Authors: Albrecht Łukasz , Richter Bo , Vila Carlos , Krawczyk Henryk , Jørgensen Karl Anker
Published: January 2009

Versatile dominoes: A novel, organocatalytic, Michael–Knoevenagel condensation domino reaction of ethyl 4‐diethoxyphosphoryl‐3‐oxobutanoate with various aryl‐ and aliphatic‐substituted α,β‐unsaturated aldehydes catalyzed by a chiral diarylprolinol ether has been successfully performed. The reaction proceeds in a highly enantio‐ and diastereoselective manner giving access to optically active 6‐substituted‐3‐diethoxyphosphoryl‐2‐oxocyclohex‐3‐enecarboxylates (see scheme).

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A novel, organocatalytic, highly enantio‐ and diastereoselective synthetic approach towards optically active 6‐substituted‐3‐diethoxyphosphoryl‐2‐oxocyclohex‐3‐enecarboxylates is presented. Our methodology utilizes a Michael–Knoevenagel domino reaction sequence of ethyl 4‐diethoxyphosphoryl‐3‐oxobutanoate and α,β‐unsaturated aldehydes catalyzed by a chiral diarylprolinol ether. The cyclohexenecarboxylates obtained are particularly well suited for the preparation of highly functionalized cyclohexene and cyclohexane derivatives, with up to four chiral centers and high levels of stereocontrol.
Iron‐Catalyzed Ligand‐Free Three‐Component Coupling Reactions of Aldehydes, Terminal Alkynes, and Amines
Authors: Li Pinhua , Zhang Yicheng , Wang Lei
Published: January 2009

A tri‐umph in many respects: The iron‐catalyzed ligand‐free, one‐pot three‐component coupling reactions of aldehydes, terminal alkynes, and amines in the presence of 4 A molecular sieves yields the corresponding propargylamines in good to excellent yields, displays a broad substrate scope, and is economical and environmentally friendly (see scheme).

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Cover Picture: The Chemistry of Escapin: Identification and Quantification of the Components in the Complex Mixture Generated by an L‐Amino Acid Oxidase in the Defensive Secretion of the Sea Snail Aplysia californica (Chem. Eur. J. 7/2009)
Authors: Kamio Michiya , Ko Ko‐Chun , Zheng Shilong , Wang Binghe , Collins Stacy L. , Gadda Giovanni , Tai Phang C. , Derby Charles D.
Published: January 2009

Defensive chemicals such as the ink secretion of this marine gastropod mollusk—the sea hares Aplysia californica—are released following attacks from predators for protection. One might expect these secretions to be complex mixtures of products, given that they must work against a diversity of predators. In their Full Paper on page 1597 ff., C. D. Derby et al. describe some of the chemical complexity of the ink of sea hares attributable to the enzyme “escapin”. Escapin is an L‐amino acid oxidase that oxidatively deaminates its major substrate, L‐lysine, to produce an equilibrium mixture of the molecules shown in this image. Photograph from Genny Anderson (Santa Barbara City College).

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Der Beitrag zur Sicherheit verfahrenstechnischer Anlagen des DECHEMA/GVC‐Forschungsausschusses „Sicherheitstechnik in Chemieanlagen”︁
Authors: Pilz V.
Published: January 2009

Der DECHEMA/GVC‐Forschungsausschuss Sicherheitstechnik in Chemieanlagen war in den vergangenen 30 Jahren seit seiner Gründung an nahezu allen sicherheitstechnischen Entwicklungen beteiligt. Die Fachgemeinschaft hat die erforderliche Forschung gefördert, das Wissen unter Fachleuten verbreitet sowie politischen Gremien zugearbeitet. Heutzutage ist die Sicherheit verfahrenstechnischer Anlagen wesentlich transparenter und das Sicherheitsmanagement erheblich systematischer. Jetzt liegt der Fokus der Weiterentwicklung daher eher auf der Nutzung von interdisziplinärem Wissen zur Entwicklung neuer Sicherheitskonzepte, um eine Optimierung von Produktivität und Sicherheit gleichermaßen zu erreichen. Der Forschungsausschuss wird auch zukünftig dafür Sorge tragen, dass sich die Sicherheit von Chemieanlagen ständig weiter entwickelt.
Europäisches Recht in der physikalisch‐chemischen Sicherheitstechnik: Beispiele in Verordnungen, Richtlinien und Normen
Authors: Bothe rer. nat. H. , Schendler T.
Published: January 2009

Grundlegende Anforderungen des Brand‐ und Explosionsschutzes im weitesten Sinn und entsprechende sicherheitstechnische Standards werden in europäischen Richtlinien und Normen beschrieben. Der Beitrag skizziert beispielhaft aktuelle Entwicklungen und in einigen Fällen deren Auswirkungen auf das entsprechende nationale Regelwerk.
Sicherheit in der Mikroreaktionstechnik
Authors: Gödde Markus , Liebner Christian , Hieronymus Hartmut
Published: January 2009

Die Mikroverfahrenstechnik beschäftigt sich mit Apparaten, deren innere Abmessungen kleiner als ein Millimeter sind. Mikroreaktoren sind zurzeit Gegenstand intensiver Forschungsarbeit. Aus Sicht der chemischen Sicherheitstechnik besteht eines von mehreren Zielen bei der Entwicklung von Mikroreaktoren darin, schwer beherrschbare Reaktionen bei Reaktionsbedingungen zu realisieren, die in konventionellen Chemieanlagen wegen ihrer besonderen Gefährlichkeit nicht mehr beherrscht werden können. Der große spezifische Wärmeaustausch kann das thermische Durchgehen der Reaktion verhindern, die engen Abmessungen können die Ausbreitung von Explosionen unterdrücken. Bei mehrstufigen Synthesen kann die Lagerung giftiger oder zersetzungsfähiger Zwischenprodukte durch unverzügliche weitere Umsetzung in einem folgenden Reaktionsschritt vermieden werden. Der vorliegende Beitrag widmet sich sicherheitstechnischen Aspekten der Mikroverfahrenstechnik.
Temperaturen und Funkenentstehung bei Trockenreibung zwischen metallischen Reibpartnern
Authors: Ott T. , Welzel F. , Beyer M. , Klages C.‐P.
Published: January 2009

Bei Fehlfunktionen von explosionsgeschützten mechanischen Geräten kann eine reibende Berührung von sich gegeneinander bewegenden Teilen nicht ausgeschlossen werden. Erreicht die Kontaktzone eine hinreichend hohe Temperatur, können die abgetragenen Partikel mit dem Luftsauerstoff verbrennen. Sowohl die hohen Oberflächentemperaturen als auch die mechanischen Funken sind dabei mögliche potenzielle Zündquelle für explosionsfähige Atmosphären.
Neural organization of first optic neuropils in the littoral crab Hemigrapsus oregonensis and the semiterrestrial species Chasmagnathus granulatus
Authors: Sztarker Julieta , Strausfeld Nicholas , Andrew David , Tomsic Daniel
Published: January 2009

Crustaceans are among the most extensively distributed arthropods, occupying many ecologies and manifesting a great variety of compound eye optics; but in comparison with insects, relatively little is known about the organization and neuronal morphologies of their underlying optic neuropils. Most studies, which have been limited to descriptions of the first neuropil—the lamina—suggest that different species have approximately comparable cell types. However, such studies have been limited with regard to the types of neurons they identify and most omit their topographic relationships. It is also uncertain whether similarities, such as they are, are independent of visual ecologies. The present account describes and compares the morphologies and dispositions of monopolar and other efferent neurons as well as the organization of tangential and smaller centrifugal neurons in two grapsoid crabs, one from the South Atlantic, the other from the North Pacific. Because these species occupy significantly disparate ecologies we ask whether this might be reflected in differences of cell arrangements within the most peripheral levels of the visual system. The present study identifies such differences with respect to the organization of centrifugal neurons to the lamina. We also identify in both species neurons in the lamina that have hitherto not been identified in crustaceans and we draw specific comparisons between the layered organization of the grapsoid lamina and layered laminas of insects. J. Comp. Neurol. 513:129–150, 2009. © 2009 Wiley‐Liss, Inc.
Involvement of R‐type Ca2+ channels in neurotransmitter release from spinal dorsolateral funiculus terminals synapsing motoneurons
Authors: Castro Alberto , Andrade Arturo , Vergara Paula , Segovia Jose , Aguilar Justo , Felix Ricardo , Delgado‐Lezama Rodolfo
Published: January 2009

Molecular studies have revealed the presence of R‐type voltage‐gated Ca2+ channels at pre‐ and postsynaptic regions; however, no evidence for the participation of these channels in transmitter release has been presented for the spinal cord. Here we characterize the effects of SNX‐482, a selective R channel blocker, on the monosynaptic excitatory postsynaptic potentials (EPSPs) evoked in motoneurons by stimulation of dorsolateral funiculus (DLF) terminals in a slice preparation from the adult turtle spinal cord. SNX‐482 inhibited neurotransmission in a dose‐dependent manner, with an IC50 of ∼9 ± 1 nM. The EPSP time course and membrane time constant of the motoneurons were not altered, suggesting a presynaptic mechanism. The toxin inhibited the residual component of the EPSPs recorded in the presence of N‐ and P/Q‐type Ca2+ channel blockers, strongly suggesting a role for the R channels in neurotransmission at the spinal cord DLF terminals. Consistently with this, RT‐PCR analysis of turtle spinal cord segments revealed the expression of the CaV2.3 pore‐forming (α1E) subunit of R channels, whereas the use of anti‐α1E‐specific antibodies resulted in its localization in the DLF fibers as demonstrated by immunohistochemistry coupled with laser confocal microscopy. J. Comp. Neurol. 513:188–196, 2009. © 2009 Wiley‐Liss, Inc.
Growth and characterization of thiourea mixed cadmium – lead chloride – a nonlinear optical crystal
Authors: Nagarajan K. , Raman S. Kumara , Sundaram R.
Published: January 2009

Nonlinear optical (NLO) crystal of thiourea mixed cadmium–lead chloride dihydrate Cd[(PbCl3)(NH2CSNH2)].2H2O (TCCPC) have been grown in solution by slow evaporation technique at room temperature. The powder X‐ray diffraction pattern has been recorded and indexed. The UV‐Vis‐NIR transmittance and FT‐IR spectrum have been recorded in the range 200‐1090 nm and 400‐4000 cm‐1, respectively. The lower cut‐off wavelength is 280 nm in the UV region, which is higher than that of pure Cd(PbCl3) (CCPC) crystal. The presence of functional groups has been confirmed by FT‐IR analysis. The TCCPC crystal was characterized by SEM and EDX spectrum. The second harmonic generation (SHG) of the thiourea mixed cadmium–lead chloride (TCCPC) crystal is demonstrated by the Kurtz Perry method using Nd:YAG laser and the results confirm that the grown crystal is roughly three times more efficient than ADP. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Crystal structure and characterization of a novel organic optical crystal: 4‐chloro‐3‐nitrobenzophenone
Authors: Babu G. Anandha , Thirupugalmani K. , Ramasamy P. , Ravikumar K.
Published: January 2009

Single crystals of a novel organic material, 4‐Chloro‐3‐Nitrobenzophenone (4C3N) were grown from acetone solution employing the technique of controlled evaporation. 4C3N belongs to the Orthorhombic system, with a = 12.9665(11) Å, b = 7.4388(6) Å, c = 24.336(2) Å, α = β = γ = 90°. FT‐IR study has been performed to identify the functional groups. The transmittance of 4C3N has been used to calculate the refractive index n; the extinction coefficient K and both the real εr and imaginary εi components of the dielectric constant as functions of photon energy. The optical band gap of 4C3N is 2.7 eV. Thermo gravimetric analysis and differential thermal analysis have also been carried out, and the thermal behavior of 4C3N crystal has been studied. The mechanical properties have been investigated. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Conversion from ZnO nanospindles into ZnO/ZnS core/shell composites and ZnS microspindles
Authors: Li Fei , Liu Xueqin , Kong Tao , Li Zhen , Huang Xintang
Published: January 2009

The formation process of ZnO/ZnS core/shell microcomposites and ZnS microspindles prepared by the reaction of ZnO colloids and thioacetamide under hydrothermal conditions was investigated in detail by X‐ray powder diffraction, field emission scanning electron microscopy, transmission electron microscopy and selected‐area electron diffraction techniques. The precursors of spindlelike ZnO colloids were prepared by a hydrothermal method with the help of a surfactant. A growth mechanism was proposed to account for the formation of ZnO/ZnS core/shell microcomposites and ZnS microspindles. Luminescence measurement revealed that ZnO/ZnS core/shell microcomposites integrated the luminescence effect of ZnO and ZnS. The blue and green emissions were dramatically enhanced, while the orange emission disappeared. The results provide a good approach to tune the visible emission of the ZnO nanostructures by ZnS coating. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Factors affecting the formation of misoriented domains in 6H‐SiC single crystals grown by PVT method
Authors: Peng T. H. , Yang H. , Jian J. K. , Wang W. J. , Wang W. Y. , Chen X. L.
Published: January 2009

Misoriented domains (MDs) are common defects in 6H‐SiC single crystals. We performed an experimental study on the formation of MDs in 2‐inch 6H‐SiC single crystals. Micro‐Raman spectroscopy revealed that the polytype of MDs was mainly 4H‐SiC. By changing growth conditions, it was found that the MDs' formation was closely related to growth rate and the position of highest temperature relative to growth interface. When the growth rate of ingots was relatively high the MDs were more likely to form. Furthermore, the nearer growth interface the position of highest temperature was, the larger the size of the MDs. Based on our experimental findings we suggested that the MDs' formation and the polytype switching from 6H‐ to 4H‐SiC were due to too large axial and/or radial temperature gradients.The results would be helpful to improve the quality of SiC single crystals grown by PVT technique. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Energetic Salts of Low‐Symmetry Methylated 5‐Aminotetrazoles
Authors: Klapötke Thomas M. , Miró Sabaté Carles , Penger Alexander , Rusan Magdalena , Welch Jan M.
Published: January 2009

Ionic salts containing the novel 5‐amino‐2‐methyl‐ and 5‐amino‐1,3‐dimethyltetrazolium cations with energetic anions (perchlorate, nitrate, azide and dinitramide) have been synthesized in high yields and purities and fully characterized. A full structural description by spectroscopic methods (vibrational and 15N NMR spectroscopy) and X‐ray analysis is given. Unexpectedly, salts based on the asymmetric 5‐amino‐1,3‐dimethyltetrazolium cation have higher densities than analogue compounds containing the isomeric 5‐amino‐1,4‐dimethyltetrazolium cation, regardless of the lower symmetry of the former. This can be attributed to secondary interactions between the cation and anion and is reflected in the higher detonation parameters of the new compounds, which represent a new class of nitrogen‐rich, high‐performing materials with low sensitivity and good potential for energetic applications. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Elimination of an Alkyl Group from Imidazolium Salts: Imidazole‐Coordinated Dinuclear Monodentate NHC–Palladium Complexes Driven by Self‐Assembly and Their Application in the Heck Reaction
Authors: Liu Lian‐jun , Wang Feijun , Shi Min
Published: January 2009

A new family of imidazole‐coordinated monodentate NHC–metal complexes 9 was obtained as well as cis‐chelatedbidentate NHC–metal complexes 10 from novel bis(imidazolium) salts 4 with a biphenyl backbone. The structures of complexes 9a and 10b were determined by X‐ray crystal‐structure diffraction, and their application in the Heck reaction showed good to excellent catalytic activities under very mild conditions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
1,8‐Bis(dialkylamino)‐4,5‐dinitronaphthalenes and 4,5‐Bis(dimethylamino)naphthalene‐1,8‐dicarbaldehyde as “Push–Pull” Proton Sponges: When and Why Formyl Groups Become Stronger π‐Electron Acceptors than Nitro Groups
Authors: Ozeryanskii Valery A. , Pozharskii Alexander F. , Artaryan Alexander K. , Vistorobskii Nikolai V. , Starikova Zoya A.
Published: January 2009

Single‐crystal X‐ray studies of four representatives of “push–pull” proton sponges, namely 1,8‐bis(dimethylamino)‐, 1,8‐bis(diethylamino)‐, 1,8‐bis(dipropylamino)‐4,5‐dinitronaphthalenes and 4,5‐bis(dimethylamino)naphthalene‐1,8‐dicarbaldehyde have been performed at low and ambient temperatures. The most interesting and unexpected result is that the formyl groups in the peri‐dialdehyde display stronger π‐acceptor effects than the nitro groups. This phenomenon is ascribed to smaller steric demands of the CHO groups, their lower electrostatic repulsion, and specific packing forces. The naphthalene cores of all but one of the molecules are markedly twisted (21–26°) while that of the diethylamino derivative is not (<5°), providing different and somewhat unpredictable ways of resonance stabilization and steric relaxation. The through‐conjugation in the above compounds is also discussed for gas and solution phases on the basis of theoretical calculations, UV/Vis and 1H NMR spectra.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)