bluuebunny/crossref_metadata_2025_split huggingface dataset:
Übergangsmetallkatalysierte Wasserstofftransferanellierungen: Zugang zu heterocyclischen Gerüsten
Authors: Nandakumar Avanashiappan , Midya Siba Prasad , Landge Vinod Gokulkrishna , Balaraman Ekambaram 
Published: August 2015

AbstractÜbergangsmetall‐Wasserstofftransferkatalysatoren ermöglichen ausgehend von einfachen Ausgangsmaterialien einen schnellen Zugang zu wichtigen Strukturmotiven, so auch zu Heterocyclen. Übergangsmetallkatalysierte Wasserstofftransferanellierungen sind umweltverträglich und in hohem Maße atomökonomisch, da sie Wasser und Wasserstoff als Nebenprodukt freisetzen und erneuerbare Alkohole als Ausgangsmaterialien verwenden. Hier werden neueste Fortschritte auf diesem Gebiet im Hinblick auf Anellierungen von Alkoholen mit verschiedenen nucleophilen Reaktionspartnern vorgestellt, bei denen heterocyclische Gerüste gebildet werden.
Formation and Characterization of the Boron Dicarbonyl Complex [B(CO)2]−
Authors: Zhang Qingnan , Li Wan‐Lu , Xu Cong‐Qiao , Chen Mohua , Zhou Mingfei , Li Jun , Andrada Diego M. , Frenking Gernot 
Published: August 2015

AbstractWe report the synthesis and spectroscopic characterization of the boron dicarbonyl complex [B(CO)2]−. The bonding situation is analyzed and compared with the aluminum homologue [Al(CO)2]− using state‐of‐the‐art quantum chemical methods.
Efficient Dynamic Nuclear Polarization at 800 MHz/527 GHz with Trityl‐Nitroxide Biradicals
Authors: Mathies Guinevere , Caporini Marc A. , Michaelis Vladimir K. , Liu Yangping , Hu Kan‐Nian , Mance Deni , Zweier Jay L. , Rosay Melanie , Baldus Marc , Griffin Robert G. 
Published: August 2015

AbstractCross‐effect (CE) dynamic nuclear polarization (DNP) is a rapidly developing technique that enhances the signal intensities in magic‐angle spinning (MAS) NMR spectra. We report CE DNP experiments at 211, 600, and 800 MHz using a new series of biradical polarizing agents referred to as TEMTriPols, in which a nitroxide (TEMPO) and a trityl radical are chemically tethered. The TEMTriPol molecule with the optimal performance yields a record 1H NMR signal enhancement of 65 at 800 MHz at a concentration of 10 mM in a glycerol/water solvent matrix. The CE DNP enhancement for the TEMTriPol biradicals does not decrease as the magnetic field is increased in the manner usually observed for bis‐nitroxides. Instead, the relatively strong exchange interaction between the trityl and nitroxide moieties determines the magnetic field at which the optimum enhancement is observed.
The Synthesis of Stable, Complex Organocesium Tetramic Acids through the Ugi Reaction and Cesium‐Carbonate‐Promoted Cascades
Authors: Martinez‐Ariza Guillermo , Ayaz Muhammad , Roberts Sue A. , Rabanal‐León Walter A. , Arratia‐Pérez Ramiro , Hulme Christopher 
Published: August 2015

AbstractTwo structurally unique organocesium carbanionic tetramic acids have been synthesized through expeditious and novel cascade reactions of strategically functionalized Ugi skeletons delivering products with two points of potential diversification. This is the first report of the use of multicomponent reactions and subsequent cascades to access complex, unprecedented organocesium architectures. Moreover, this article also highlights the first use of mild cesium carbonate as a cesium source for the construction of cesium organometallic scaffolds. Relativistic DFT calculations provide an insight into the electronic structure of the reported compounds.
Oxidative Allene Amination for the Synthesis of Azetidin‐3‐ones
Authors: Burke Eileen G. , Schomaker Jennifer M. 
Published: August 2015

AbstractRegioselectivity in the aziridination of silyl‐substituted homoallenic sulfamates is readily diverted to the distal double bond of the allene to yield endocyclic bicyclic methyleneaziridines with excellent stereocontrol. Subsequent reaction with electrophilic oxygen sources initiates facile rearrangement to densely functionalized, fused azetidin‐3‐ones in excellent d.r., effectively transferring the axial chirality of the allene to central chirality in the products. The steric nature of the silyl group dictates which of the two rings of the fused azetidin‐3‐one will undergo further functionalization, providing an additional element of diversity for the preparation of enantioenriched azetidine scaffolds with potential biological activity.
Induction of Stem‐Cell‐Derived Functional Neurons by NanoScript‐Based Gene Repression
Authors: Patel Sahishnu , Chueng Sy‐Tsong Dean , Yin Perry T. , Dardir Kholud , Song Zhichao , Pasquale Nicholas , Kwan Kelvin , Sugiyama Hiroshi , Lee Ki‐Bum 
Published: August 2015

AbstractEven though gene repression is a powerful approach to exogenously regulate cellular behavior, developing a platform to effectively repress targeted genes, especially for stem‐cell applications, remains elusive. Herein, we introduce a nanomaterial‐based platform that is capable of mimicking the function of transcription repressor proteins to downregulate gene expression at the transcriptional level for enhancing stem‐cell differentiation. We developed the “NanoScript” platform by integrating multiple gene repression molecules with a nanoparticle. First, we show a proof‐of‐concept demonstration using a GFP‐specific NanoScript to knockdown GFP expression in neural stem cells (NSCs‐GFP). Then, we show that a Sox9‐specific NanoScript can repress Sox9 expression to initiate enhanced differentiation of NSCs into functional neurons. Overall, the tunable properties and gene‐knockdown capabilities of NanoScript enables its utilization for gene‐repression applications in stem cell biology.
Stability of Fe‐N‐C Catalysts in Acidic Medium Studied by Operando Spectroscopy
Authors: Choi Chang Hyuck , Baldizzone Claudio , Grote Jan‐Philipp , Schuppert Anna K. , Jaouen Frédéric , Mayrhofer Karl J. J. 
Published: August 2015

AbstractFundamental understanding of non‐precious metal catalysts for the oxygen reduction reaction (ORR) is the nub for the successful replacement of noble Pt in fuel cells and, therefore, of central importance for a technological breakthrough. Herein, the degradation mechanisms of a model high‐performance Fe‐N‐C catalyst have been studied with online inductively coupled plasma mass spectrometry (ICP‐MS) and differential electrochemical mass spectroscopy (DEMS) coupled to a modified scanning flow cell (SFC) system. We demonstrate that Fe leaching from iron particles occurs at low potential (<0.7 V) without a direct adverse effect on the ORR activity, while carbon oxidation occurs at high potential (>0.9 V) with a destruction of active sites such as FeNxCy species. Operando techniques combined with identical location‐scanning transmission electron spectroscopy (IL‐STEM) identify that the latter mechanism leads to a major ORR activity decay, depending on the upper potential limit and electrolyte temperature. Stable operando potential windows and operational strategies are suggested for avoiding degradation of Fe‐N‐C catalysts in acidic medium.
Uncovering the Role of Metal Catalysis in Tetrazole Formation by an In Situ Cycloaddition Reaction: An Experimental Approach
Authors: Zhong Di‐Chang , Wen Ya‐Qiong , Deng Ji‐Hua , Luo Xu‐Zhong , Gong Yun‐Nan , Lu Tong‐Bu 
Published: August 2015

AbstractUsing an experimental approach, the role of metal catalysis has been investigated in the in situ cycloaddition reaction of nitrile with azide to form tetrazoles. It has been shown that metal catalysis serves to activate the cyano group in the nitrile reagent by a coordinative interaction.
Photon‐Upconverting Ionic Liquids: Effective Triplet Energy Migration in Contiguous Ionic Chromophore Arrays
Authors: Hisamitsu Shota , Yanai Nobuhiro , Kimizuka Nobuo 
Published: August 2015

AbstractInspired by the bicontinuous ionic‐network structure of ionic liquids (ILs), we developed a new family of photofunctional ILs which show efficient triplet energy migration among contiguously arrayed ionic chromophores. A novel fluorescent IL, comprising an aromatic 9,10‐diphenylanthracene 2‐sulfonate anion and an alkylated phosphonium cation, showed pronounced interactions between chromophores, as revealed by its spectral properties. Upon dissolving a triplet sensitizer, the IL demonstrated photon upconversion based on triplet–triplet annihilation (TTA‐UC). Interestingly, the TTA‐UC process in the chromophoric IL was optimized at a much lower excitation intensity compared to the previous nonionic liquid TTA‐UC system. The superior TTA‐UC in this IL system is characterized by a relatively high triplet diffusion constant (1.63×10−6 cm2 s−1) which is ascribed to the presence of ionic chromophore networks in the IL.
Enantioselective ortho‐CH Cross‐Coupling of Diarylmethylamines with Organoborons
Authors: Laforteza Brian N. , Chan Kelvin S. L. , Yu Jin‐Quan 
Published: August 2015

AbstractThe commonly used para‐nitrobenzenesulfonyl (nosyl) protecting group is employed to direct the CH activation of amines for the first time. An enantioselective ortho‐CH cross‐coupling between nosyl‐protected diarylmethylamines and arylboronic acid pinacol esters has been achieved utilizing chiral mono‐N‐protected amino acid (MPAA) ligands as a promoter.
Thermosensitive Ion Channel Activation in Single Neuronal Cells by Using Surface‐Engineered Plasmonic Nanoparticles
Authors: Nakatsuji Hirotaka , Numata Tomohiro , Morone Nobuhiro , Kaneko Shuji , Mori Yasuo , Imahori Hiroshi , Murakami Tatsuya 
Published: August 2015

AbstractControlling cell functions using external photoresponsive nanomaterials has enormous potential for the development of cell‐engineering technologies and intractable disease therapies, but the former currently requires genetic modification of the target cells. We present a method using plasma‐membrane‐targeted gold nanorods (pm‐AuNRs) prepared with a cationic protein/lipid complex to activate a thermosensitive cation channel, TRPV1, in intact neuronal cells. Highly localized photothermal heat generation mediated by the pm‐AuNRs induced Ca2+ influx solely by TRPV1 activation. In contrast, the use of previously reported cationic AuNRs that are coated with a conventional synthetic polymer also led to photoinduced Ca2+ influx, but this influx resulted from membrane damage. Our method provides an optogenetic platform without the need for prior genetic engineering of the target cells and might be useful for novel TRPV1‐targeted phototherapeutic approaches.
Copper‐Catalyzed Enantioselective 1,6‐Boration of para‐Quinone Methides and Efficient Transformation of gem‐Diarylmethine Boronates to Triarylmethanes
Authors: Lou Yazhou , Cao Peng , Jia Tao , Zhang Yongling , Wang Min , Liao Jian 
Published: August 2015

AbstractPresented is the first enantioselective copper‐catalyzed 1,6‐conjugate addition of bis(pinacolato)diboron to para‐quinone methides. The reaction proceeds with excellent yields and good to excellent enantioselectivities, and provides an attractive approach to the construction of optically active gem‐diarylmehtine boronic esters. Additionally, the subsequent conversion of the derived potassium trifluoroborates into triarylmethanes with highly enantiospecificity was realized.
Modular Architecture of Protein Binding Units for Designing Properties of Cellulose Nanomaterials
Authors: Malho Jani‐Markus , Arola Suvi , Laaksonen Päivi , Szilvay Géza R. , Ikkala Olli , Linder Markus B. 
Published: August 2015

AbstractMolecular biomimetic models suggest that proteins in the soft matrix of nanocomposites have a multimodular architecture. Engineered proteins were used together with nanofibrillated cellulose (NFC) to show how this type of architecture leads to function. The proteins consist of two cellulose‐binding modules (CBM) separated by 12‐, 24‐, or 48‐mer linkers. Engineering the linkers has a considerable effects on the interaction between protein and NFC in both wet colloidal state and a dry film. The protein optionally incorporates a multimerizing hydrophobin (HFB) domain connected by another linker. The modular structure explains effects in the hydrated gel state, as well as the deformation of composite materials through stress distribution and crosslinking. Based on this work, strategies can be suggested for tuning the mechanical properties of materials through the coupling of protein modules and their interlinking architectures.
Detection of the Short‐Lived Radical Cation Intermediate in the Electrooxidation of N,N‐Dimethylaniline by Mass Spectrometry
Authors: Brown Timothy A. , Chen Hao , Zare Richard N. 
Published: August 2015

AbstractThe N,N‐dimethylaniline (DMA) radical cation DMA.+, a long‐sought transient intermediate, was detected by mass spectrometry (MS) during the electrochemical oxidation of DMA. This was accomplished by coupling desorption electrospray ionization (DESI) MS with a waterwheel working electrode setup to sample the surface of the working electrode during electrochemical analysis. This study clearly shows that DESI‐based electrochemical MS is capable of capturing electrochemically generated intermediates with half‐lives on the order of microseconds, which is 4–5 orders of magnitude faster than previously reported electrochemical mass spectrometry techniques.
Silver‐Mediated Oxidative Trifluoromethylation of Phenols: Direct Synthesis of Aryl Trifluoromethyl Ethers
Authors: Liu Jian‐Bo , Chen Chao , Chu Lingling , Chen Zeng‐Hao , Xu Xiu‐Hua , Qing Feng‐Ling 
Published: August 2015

AbstractAryl trifluoromethyl ethers (ArOCF3) are prevalent in pharmaceuticals, agrochemicals, and materials. However, methods for the general and efficient synthesis of these compounds are extremely underdeveloped and limited. Herein, we describe a highly efficient and general procedure for the direct O‐trifluoromethylation of unprotected phenols through a silver‐mediated cross‐coupling reaction using CF3SiMe3 as the CF3 source and exogenous oxidants. This novel oxidative trifluoromethylation provides access to a wide range of aryl trifluoromethyl ethers from simple phenols. The mild process was also applied to the late‐stage trifluoromethylation of a medicinally relevant compound.
Preparation of a Silanone through Oxygen Atom Transfer to a Stable Cyclic Silylene
Authors: Linden Michael M. , Reisenauer Hans Peter , Gerbig Dennis , Karni Miriam , Schäfer Annemarie , Müller Thomas , Apeloig Yitzhak , Schreiner Peter R. 
Published: August 2015

AbstractWe report the evaporation of a stable cyclic silylene and its oxidation (with ozone or N2O) through oxygen atom transfer to form the corresponding silanone under matrix isolation conditions. As uncomplexed silanones are rare owing to their very high reactivity, this method provides an alternative route to these sought‐after molecules. The silanone, as well as a novel bicyclic silane with a bridgehead silicon atom derived from an intramolecular silylene CH bond insertion, were characterized by comparison of high‐resolution infrared spectra with density functional theory (DFT) computations at the M06‐2X/cc‐pVDZ level of theory.
Hollow Zn/Co ZIF Particles Derived from Core–Shell ZIF‐67@ZIF‐8 as Selective Catalyst for the Semi‐Hydrogenation of Acetylene
Authors: Yang Jian , Zhang Fengjun , Lu Haiyuan , Hong Xun , Jiang Hailong , Wu Yuen , Li Yadong 
Published: August 2015

AbstractThe rational design of metal–organic frameworks (MOFs) with hollow features and tunable porosity at the nanoscale can enhance their intrinsic properties and stimulates increasing attentions. In this Communication, we demonstrate that methanol can affect the coordination mode of ZIF‐67 in the presence of Co2+ and induces a mild phase transformation under solvothermal conditions. By applying this transformation process to the ZIF‐67@ZIF‐8 core–shell structures, a well‐defined hollow Zn/Co ZIF rhombic dodecahedron can be obtained. The manufacturing of hollow MOFs enables us to prepare a noble metal@MOF yolk‐shell composite with controlled spatial distribution and morphology. The enhanced gas storage and porous confinement that originate from the hollow interior and coating of ZIF‐8 confers this unique catalyst with superior activity and selectivity toward the semi‐hydrogenation of acetylene.
Biological Chitin–MOF Composites with Hierarchical Pore Systems for Air‐Filtration Applications
Authors: Wisser Dorothea , Wisser Florian M. , Raschke Silvia , Klein Nicole , Leistner Matthias , Grothe Julia , Brunner Eike , Kaskel Stefan 
Published: August 2015

AbstractMetal–organic frameworks (MOFs) are promising materials for gas‐separation and air‐filtration applications. However, for these applications, MOF crystallites need to be incorporated in robust and manageable support materials. We used chitin‐based networks from a marine sponge as a non‐toxic, biodegradable, and low‐weight support material for MOF deposition. The structural properties of the material favor predominant nucleation of the MOF crystallites at the inside of the hollow fibers. This composite has a hierarchical pore system with surface areas up to 800 m2 g−1 and pore volumes of 3.6 cm3 g−1, allowing good transport kinetics and a very high loading of the active material. Ammonia break‐through experiments highlight the accessibility of the MOF crystallites and the adsorption potential of the composite indicating their high potential for filtration applications for toxic industrial gases.
Regioregular Synthesis of Azaborine Oligomers and a Polymer with a syn Conformation Stabilized by NH⋅⋅⋅π Interactions
Authors: Baggett Andrew W. , Guo Fang , Li Bo , Liu Shih‐Yuan , Jäkle Frieder 
Published: August 2015

AbstractThe regioregular synthesis of the first azaborine oligomers and a corresponding conjugated polymer was accomplished by Suzuki–Miyaura coupling methods. An almost perfectly coplanar syn arrangement of the heterocycles was deduced from an X‐ray crystal structure of the dimer, which also suggested that NH⋅⋅⋅π interactions play an important role. Computational studies further supported these experimental observations and indicated that the electronic structure of the longer azaborine oligomers and polymer resembles that of poly(cyclohexadiene) more than poly(p‐phenylene). A comparison of the absorption and emission properties of the polymer with those of the oligomers revealed dramatic bathochromic shifts upon chain elongation, thus suggesting highly effective extension of conjugation.
Fluorine‐Free Anti‐Smudge Polyurethane Coatings
Authors: Rabnawaz Muhammad , Liu Guojun , Hu Heng 
Published: August 2015

AbstractConventionally, low‐surface‐tension fluorinated reagents are incorporated into anti‐smudge (oil‐ and water‐repellent) coatings for oil repellency. However, fluorinated compounds are expensive and an environmental concern because of their high stability and bioaccumulation. These factors limit their widespread application. We report herein the development of fluorine‐free anti‐smudge polyurethane coatings that are clear at thicknesses up to tens of micrometers and are able to sustain extensive surface damage. We demonstrate that these coatings can be applied readily onto a diverse range of substrates.
Activation of α‐Diazocarbonyls by Organic Catalysts: Diazo Group Acting as a Strong N‐Terminal Electrophile
Authors: Li Lei , Chen Jia‐Jia , Li Yi‐Jin , Bu Xiu‐Bin , Liu Qun , Zhao Yu‐Long 
Published: August 2015

AbstractFor the first time α‐diazocarbonyls have been used as highly active N‐terminal electrophiles in the presence of bicyclic amidine catalysts. The CN bond‐forming reactions of active methylene compounds as C nucleophiles with α‐diazocarbonyls as N‐terminal electrophiles proceed quickly under ambient conditions, in the presence of 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU), because of the formation of the reactive N‐terminal electrophilic intermediates. DBU activates both the active methylene and α‐diazocarbonyl. Importantly, this reaction is general for both active methylenes and α‐diazocarbonyls, and the activation mode will lead to new synthetic applications of α‐diazocarbonyls.
Selective Ruthenium‐Catalyzed Hydrochlorination of Alkynes: One‐Step Synthesis of Vinylchlorides
Authors: Dérien Sylvie , Klein Hubert , Bruneau Christian 
Published: August 2015

AbstractAn unprecedented ruthenium‐catalyzed direct and selective alkyne hydrochlorination is reported and leads to vinylchlorides in excellent yields with atom economy. The reaction proceeds at room temperature from terminal alkynes and provides a variety of chloroalkenes. Only the regioisomer resulting from the formal Markovnikov addition is selectively formed. Mechanistic studies show the stereoselective syn addition of HCl to alkynes at room temperature and suggest a chloro hydrido RuIV species as a key intermediate of the reaction.
Biomimetic Total Syntheses of (−)‐Leucoridines A and C through the Dimerization of (−)‐Dihydrovalparicine
Authors: Kokkonda Praveen , Brown Keaon R. , Seguin Trevor J. , Wheeler Steven E. , Vaddypally Shivaiah , Zdilla Michael J. , Andrade Rodrigo B. 
Published: August 2015

AbstractConcise biomimetic syntheses of the Strychnos‐Strychnos‐type bis‐indole alkaloids (−)‐leucoridine A (1) and C (2) were accomplished through the biomimetic dimerization of (−)‐dihydrovalparicine (3). En route to 3, the known alkaloids (+)‐geissoschizoline (8) and (−)‐dehydrogeissoschizoline (10) were also prepared. DFT calculations were employed to elucidate the mechanism, which favors a stepwise aza‐Michael/spirocyclization sequence over the alternate hetero‐Diels–Alder cycloaddition reaction.
Polymeric Micelle Assembly for the Smart Synthesis of Mesoporous Platinum Nanospheres with Tunable Pore Sizes
Authors: Li Yunqi , Bastakoti Bishnu Prasad , Malgras Victor , Li Cuiling , Tang Jing , Kim Jung Ho , Yamauchi Yusuke 
Published: August 2015

AbstractA facile method for the fabrication of well‐dispersed mesoporous Pt nanospheres involves the use of a polymeric micelle assembly. A core–shell–corona type triblock copolymer [poly(styrene‐b‐2‐vinylpyridine‐b‐ethylene oxide), PS‐b‐P2VP‐b‐PEO] is employed as the pore‐directing agent. Negatively charged PtCl42− ions preferably interact with the protonated P2VP+ blocks while the free PEO chains prevent the aggregation of the Pt nanospheres. The size of the mesopores can be finely tuned by varying the length of the PS chain. Furthermore, it is demonstrated that the metallic mesoporous nanospheres thus obtained are promising candidates for applications in electrochemistry.
Definitive Molecular Level Characterization of Defects in UiO‐66 Crystals
Authors: Trickett Christopher A. , Gagnon Kevin J. , Lee Seungkyu , Gándara Felipe , Bürgi Hans‐Beat , Yaghi Omar M. 
Published: August 2015

AbstractThe identification and characterization of defects, on the molecular level, in metal‐organic frameworks (MOFs) remain a challenge. With the extensive use of single‐crystal X‐ray diffraction (SXRD), the missing linker defects in the zirconium‐based MOF UiO‐66, Zr6O4(OH)4(C8H4O4)6, have been identified as water molecules coordinated directly to the zirconium centers. Charge balancing is achieved by hydroxide anions, which are hydrogen bonded within the pores of the framework. Furthermore, the precise nature of the defects and their concentration can be manipulated by altering the starting materials, synthesis conditions, and post‐synthetic modifications.
Synthesis of ent‐Ketorfanol via a C–H Alkenylation/Torquoselective 6π Electrocyclization Cascade
Authors: Phillips Eric M. , Mesganaw Tehetena , Patel Ashay , Duttwyler Simon , Mercado Brandon Q. , Houk Kendall N. , Ellman Jonathan A. 
Published: August 2015

AbstractThe asymmetric synthesis of ent‐ketorfanol from simple and commercially available precursors is reported. A RhI‐catalyzed intramolecular CH alkenylation/torquoselective 6π electrocyclization cascade provides a fused bicyclic 1,2‐dihydropyridine as a key intermediate. Computational studies were performed to understand the high torquoselectivity of the key 6π electrocyclization. The computational results demonstrate that a conformational effect is responsible for the observed selectivity. The ketone functionality and final ring are introduced in a single step by a redox‐neutral acid‐catalyzed rearrangement of a vicinal diol to give the requisite carbonyl, followed by intramolecular Friedel–Crafts alkylation.