bluuebunny/crossref_metadata_2025_split huggingface dataset:
Enantioselective Organocatalytic Diels–Alder Trapping of Photochemically Generated Hydroxy‐o‐Quinodimethanes
Authors: Dell'Amico Luca , Vega‐Peñaloza Alberto , Cuadros Sara , Melchiorre Paolo 
Published: January 2016

AbstractThe photoenolization/Diels–Alder strategy offers straightforward access to synthetically valuable benzannulated carbocyclic products. This historical light‐triggered process has never before succumbed to efforts to develop an enantioselective catalytic approach. Herein, we demonstrate how asymmetric organocatalysis provides simple yet effective catalytic tools to intercept photochemically generated hydroxy‐o‐quinodimethanes with high stereoselectivity. We used a chiral organic catalyst, derived from natural cinchona alkaloids, to activate maleimides toward highly stereoselective Diels–Alder reactions. An unconventional mechanism of stereocontrol is operative, wherein the organocatalyst is actively involved in both the photochemical pathway, by leveraging the formation of the reactive photoenol, and the stereoselectivity‐defining event.
Radical Fluoroalkylation of Isocyanides with Fluorinated Sulfones by Visible‐Light Photoredox Catalysis
Authors: Rong Jian , Deng Ling , Tan Ping , Ni Chuanfa , Gu Yucheng , Hu Jinbo 
Published: January 2016

AbstractThe radical fluoroalkylation of isocyanides with fluorinated sulfones is enabled by visible‐light photoredox catalysis. A wide range of readily available mono‐, di‐, and trifluoromethyl heteroaryl sulfones can thus be used as efficient radical fluoroalkylation reagents under mild conditions. This method not only describes a new synthetic application of fluorinated sulfones, but also provides a new route to fluoroalkyl radicals.
Rapid Access to 2‐Methylene Tetrahydrofurans and γ‐Lactones: A Tandem Four‐Step Process
Authors: Liang Renxiao , Chen Kai , Zhang Qiaohui , Zhang Jiantao , Jiang Huanfeng , Zhu Shifa 
Published: January 2016

AbstractA one‐pot tandem process involving hydrolysis, Knoevenagel condensation, Michael addition, and Conia‐ene (HKMC) reactions has been developed for the rapid synthesis of indanone‐fused 2‐methylene tetrahydrofurans from the reaction of enynals and propynols. In this process, two rings and four bonds are generated with 100 % atom‐economy and high step‐efficiency. The resulting tetrahydrofurans were readily oxidized into α‐methylene γ‐lactones, which are one of the most important substructures in natural and bioactive compounds.
A simple and rapid resonance Rayleigh scattering method for detection of indigo carmine in soft drink
Authors: Li Qin , Yang Jidong , Tan Xuanping , Zhang Zhan , Hu Xiaomei , Yang Menghuan 
Published: January 2016

AbstractA novel method that uses acridine orange (AO) to detect indigo carmine (IC) in soft drinks was developed. The method is highly sensitive and is based on a resonance Rayleigh scattering (RRS) technique. In Britton–Robinson (BR) buffer solution, pH 4.3, the weak RRS intensity of AO was greatly enhanced by the addition of IC, with the maximum peak located at 332 nm. Under optimum conditions, it was found that the enhanced RRS intensity was proportional to the concentration of IC over a range of 2–32 × 10−6 mol/L. A low detection limit of 2.4 × 10−8 mol/L was achieved. The sensitivity and selectivity of the method are high enough to permit the determination of trace amounts of IC without any significant interference from high levels of other components such as common anions and other amino acids. Finally, the concentration of IC in three different soft drinks was determined with satisfactory results. Copyright © 2016 John Wiley & Sons, Ltd.
Design and Synthesis of an Alkynyl Luciferin Analogue for Bioluminescence Imaging
Authors: Steinhardt Rachel C. , O'Neill Jessica M. , Rathbun Colin M. , McCutcheon David C. , Paley Miranda A. , Prescher Jennifer A. 
Published: January 2016

AbstractHerein, the synthesis and characterization of an alkyne‐modified luciferin is reported. This bioluminescent probe was accessed using C−H activation methodology and was found to be stable in solution and capable of light production with firefly luciferase. The luciferin analogue was also cell permeant and emitted more redshifted light than d‐luciferin, the native luciferase substrate. Based on these features, the alkynyl luciferin will be useful for a variety of imaging applications.
Upconverting Nanoparticles Prompt Remote Near‐Infrared Photoactivation of Ru(II)–Arene Complexes
Authors: Ruggiero Emmanuel , Garino Claudio , Mareque‐Rivas Juan C. , Habtemariam Abraha , Salassa Luca 
Published: January 2016

AbstractThe synthesis and full characterisation (including X‐ray diffraction studies and DFT calculations) of two new piano‐stool RuII–arene complexes, namely [(η6‐p‐cym)Ru(bpy)(m‐CCH‐Py)][(PF)6]2 (1) and [(η6‐p‐cym)Ru(bpm)(m‐CCH‐Py)][(PF)6]2 (2; p‐cym=p‐cymene, bpy=2,2′‐bipyridine, bpm=2,2′‐bipyrimidine, and m‐CCH‐Py=3‐ethynylpyridine), is described and discussed. The reaction of the m‐CCH‐Py ligand of 1 and 2 with diethyl‐3‐azidopropyl phosphonate by Cu‐catalysed click chemistry affords [(η6‐p‐cym)Ru(bpy)(P‐Trz‐Py)][(PF)6]2 (3) and [(η6‐p‐cym)Ru(bpm)(P‐Trz‐Py)][(PF)6]2 (4; P‐Trz‐Py=[3‐(1‐pyridin‐3‐yl‐[1,2,3]triazol‐4‐yl)‐propyl]phosphonic acid diethyl ester). Upon light excitation at λ=395 nm, complexes 1–4 photodissociate the monodentate pyridyl ligand and form the aqua adduct ions [(η6‐p‐cym)Ru(bpy)(H2O)]2+ and [(η6‐p‐cym)Ru(bpm)(H2O)]2+. Thulium ‐doped upconverting nanoparticles (UCNPs) are functionalised with 4, thus exploiting their surface affinity for the phosphonate group in the complex. The so‐obtained nanosystem UCNP@4 undergoes near‐infrared (NIR) photoactivation at λ=980 nm, thus producing the corresponding reactive aqua species that binds the DNA‐model base guanosine 5′‐monophosphate.
Organocatalytic Asymmetric Reactions of Epoxides: Recent Progress
Authors: Meninno Sara , Lattanzi Alessandra 
Published: January 2016

AbstractIn this Minireview recent advances in the asymmetric reactions of meso and racemic epoxides promoted by organocatalysts is reviewed. Organic promoters, such as chiral phosphoric acids, amino‐ and peptidyl thioureas, and sulfinamides, have been successfully used for a variety of enantioselective transformations of epoxides under catalytic conditions, involving direct nucleophilic attack at the oxirane ring, base‐catalysed β‐eliminations and Brønsted acid catalysed 1,2‐rearrangements. Accordingly, highly valuable enantioenriched 1,2‐functionalised alcohols, carbonyl compounds and nitroepoxides are attainable. Dual activation of the reagents, provided by the organocatalysts, appears to be the most recurrent strategy, potentially suitable to face other unmet challenges in asymmetric ring‐opening reactions of epoxides.
Rapid Synthesis of D‐A′‐π‐A Dyes through a One‐Pot Three‐Component Suzuki–Miyaura Coupling and an Evaluation of their Photovoltaic Properties for Use in Dye‐Sensitized Solar Cells
Authors: Irie Shunsuke , Fuse Shinichiro , Maitani Masato M. , Wada Yuji , Ogomi Yuhei , Hayase Shuzi , Kaiho Tatsuo , Masui Hisashi , Tanaka Hiroshi , Takahashi Takashi 
Published: January 2016

AbstractTwenty‐four D‐A′–π‐A dyes were rapidly synthesized through a one‐pot three‐component Suzuki–Miyaura coupling reaction, which was assisted by microwave irradiation. We measured the absorption spectra, electrochemical properties, and solar‐cell performance of all the synthesized dyes. The D5 πA4 dye contained our originally designed rigid and nonplanar donor and exerted the highest efficiency at 5.4 %. The short‐circuit current (Jsc) was the most important parameter for the conversion efficiency (η) in the case of the organic D‐A′‐π‐A dyes. Optimal ranges for the D‐A′‐π‐A dyes were observed for high values of Jsc/λmax at λ=560–620 nm, an optical‐absorption edge of λ=690–790 nm, and EHOMO and ELUMO values of <1.14 and −0.56 to −0.76 V, respectively.
Highly Efficient Visible‐to‐NIR Luminescence of Lanthanide(III) Complexes with Zwitterionic Ligands Bearing Charge‐Transfer Character: Beyond Triplet Sensitization
Authors: Pan Mei , Du Bin‐Bin , Zhu Yi‐Xuan , Yue Mei‐Qin , Wei Zhang‐Wen , Su Cheng‐Yong 
Published: January 2016

AbstractTwo zwitterionic‐type ligands featuring π–π* and intraligand charge‐transfer (ILCT) excited states, namely 1,1′‐(2,3,5,6‐tetramethyl‐1,4‐phenylene)bis(methylene)dipyridinium‐4‐olate (TMPBPO) and 1‐dodecylpyridin‐4(1 H)‐one (DOPO), have been prepared and applied to the assembly of lanthanide coordination complexes in an effort to understand the ligand‐direction effect on the structure of the Ln complexes and the ligand sensitization effect on the luminescence of the Ln complexes. Due to the wide‐band triplet states plus additional ILCT excitation states extending into lower energy levels, broadly and strongly sensitized photoluminescence of f→f transitions from various Ln3+ ions were observed to cover the visible to near‐infrared (NIR) regions. Among which, the Pr, Sm, Dy, and Tm complexes simultaneously display both strong visible and NIR emissions. Based on the isostructural feature of the Ln complexes, color tuning and single‐component white light was achieved by preparation of solid solutions of the ternary systems Gd‐Eu‐Tb (for TMPBPO) and La‐Eu‐Tb and La‐Dy‐Sm (for DOPO). Moreover, the visible and NIR luminescence lifetimes of the Ln complexes with the TMPBPO ligand were investigated from 77 to 298 K, revealing a strong temperature dependence of the Tm3+ (3H4) and Yb3+ (2F5/2) decay dynamics, which has not been explored before for their coordination complexes.
Chondroitin Sulfate Tetrasaccharides: Synthesis, Three‐Dimensional Structure and Interaction with Midkine
Authors: Solera Cristina , Macchione Giuseppe , Maza Susana , Kayser M. Mar , Corzana Francisco , de Paz José L. , Nieto Pedro M. 
Published: January 2016

AbstractThe biological activity of midkine, a cytokine implicated in neuro‐ and tumourigenesis, is regulated by its binding to glycosaminoglycans (GAGs), such as heparin and chondroitin sulfate (CS). To better understand the molecular recognition of GAG sequences by this growth factor, the interactions between synthetic chondroitin sulfate‐like tetrasaccharides and midkine were studied by using different techniques. Firstly, a synthetic approach for the preparation of CS‐like oligosaccharides in the sequence GalNAc–GlcA was developed. A fluorescence polarisation competition assay was then employed to analyse the relative binding affinities of the synthetic compounds and revealed that midkine interacted with CS‐like tetrasaccharides in the micromolar range. The 3D structure of these tetramers was studied in detail by a combination of NMR spectroscopy experiments and molecular dynamics simulations. Saturation transfer difference (STD) NMR spectroscopy experiments indicate that the CS tetrasaccharides bind to midkine in an extended conformation, with similar saturation effects along the entire sugar chain. These results are compatible with docking studies that suggest an interaction of the tetrasaccharide with midkine in a folded structure. Overall, this study provides valuable information on the interaction between midkine and well‐defined, chemically synthesised CS oligosaccharides and these data can be useful for the design of more active compounds that modulate the biological function of this protein.
[32]π Fused Core‐Modified Heptaphyrin with Möbius Aromaticity
Authors: Ghosh Arindam , Chaudhary Arvind , Srinivasan A. , Suresh Cherumuttathu H. , Chandrashekar Tavarekere K. 
Published: January 2016

AbstractA new fused core‐modified 32π heptaphyrin with Möbius aromatic character is reported. The 1H NMR data indicated a weak Möbius aromaticity at 298 K; however, at 213–183 K, the molecule predominates [4n]π Möbius conformation with strong diatropic ring current, which was further confirmed by X‐ray analysis. The protonation experiment led to preservation of the Möbius aromaticity at 298 K. Nevertheless, the experimental results were further supported by theoretical studies. Overall, this study represents the first example of Möbius aromatic fused core‐modified expanded porphyrin.
Assembly of an Achiral Chromophore into Light‐Responsive Helical Nanostructures in the Absence of Chiral Components
Authors: Han Mina , Cho Sung June , Norikane Yasuo , Shimizu Masaki , Seki Takahiro 
Published: January 2016

AbstractThe chirality found in living organisms is one of unsolved mysteries on Earth. It is crucial to understand the manner in which small achiral molecules evolve into helical superstructures in the absence of chiral components because this process can provide important insights regarding the origin of chirality in nature. 1) the uncommon helical assembly of an achiral trigonal chromophore into helical nanostructures with aggregation‐induced emission enhancement (AIEE) characteristics and 2) the tunability of the helical pitch and fluorescence intensity in response to light is reported. The Rietveld refinement of X‐ray diffraction (XRD) patterns and the growth process suggest that a striking transformation from an achiral to an asymmetric molecule can occur as a result of specific interactions with certain solvents, presumably leading to the unique helical assembly. More importantly, exposure to UV or visible light promoted not only the formation of irregular helical structures with a wide range of pitch lengths but also an increase in fluorescence intensity.
Selecting Resolving Agents with Respect to Their Eutectic Compositions
Authors: Szeleczky Zsolt , Semsey Sándor , Bagi Péter , Pálovics Emese , Faigl Ferenc , Fogassy Elemér 
Published: January 2016

AbstractIn order to develop a resolution procedure for a given racemic compound, the first and the most important step is finding the most suitable resolving agent. We studied 18 individual resolutions that were carried out with resolving agents having high eutectic composition. We found that very high enantiomeric excess values were obtained in all cases. We assume that the eutectic composition of a given resolving agent is one of the most important properties that should always be considered during the search for the most efficient resolving agent. Chirality 28:230–234, 2016. © 2016 Wiley Periodicals, Inc.
Enantiomeric Neolignans and a Sesquiterpene from Solanum erianthum and Their Absolute Configuration Assignment
Authors: Li Hang , Peng Shi‐Yi , Yang De‐Po , Bai Bai , Zhu Long‐Ping , Mu Chun‐You , Tian Yi‐Jing , Wang Dong‐Mei , Zhao Zhi‐Min 
Published: January 2016

AbstractOne pair of new C‐8–C‐3′/C‐7–O–C‐4′ linked neolignan enantiomers (1a/1b) and one new guaiane sesquiterpene (2) first featuring the 1(2),9(10)‐conjugated double bond were isolated from the stems of Solanum erianthum (Solanceae). Their structures were characterized on the basis of extensive spectroscopic analyses, especially from their 2D nuclear magnetic resonance (NMR) spectra. The absolute configurations of 1a/1b were rigorously elucidated by electronic circular dichroism (ECD) experiments combined with the reversed helicity rule for the 2,3‐dihydrobenzo[b]furan chromophore, and compound 2 is the first report on the sterochemical assignment of a guaiane sesquiterpene by using the allylic axial chirality rule for the conjugated diene chromophore in combination with the calculated ECD spectrum. Chirality 28:259–263, 2016. © 2016 Wiley Periodicals, Inc.
Continuous Preparation of Copper/Carbon Nanotube Composite Films and Application in Solar Cells
Authors: Luo Xiao Gang , Le Wu Min , Wang Xiao Xia , Zhong Xin Hua , Zhao Ke , Wang Jian Nong 
Published: January 2016

AbstractRealizing the continuous and large scale preparation of particle/carbon nanotube (CNT) composites with enhanced functionalities, and broad applications in energy conversion, harvesting, and storage systems, remains as a big challenge. Here, we report a scalable strategy to continuously prepare particle/CNT composite films in which particles are confined by CNT films. This is achieved by the continuous condensation and deposition of a cylindrical assembly of CNTs on a paper strip and the in situ incorporation of particles during the layer‐by‐layer deposition process. A Cu/CNT composite film is prepared as an example; such a film exhibits very high power conversion efficiency when it is used as a counter electrode in a solar cell, compared with previous materials under otherwise identical conditions. The proposed method can be extended to other CNT‐based composite films with excellent functionalities for wide applications.
Beamforming‐based feature extraction and RVM‐based method for attacker node classification in CRN
Authors: S. Senthilkumar , C. Geetha Priya 
Published: January 2016

SummaryCognitive radio is a promising technology for the future wireless spectrum allocation to improve the utilization rate of the licensed bands. However, the cognitive radio network is susceptible to various attacks. Hence, there arises a need to develop a highly efficient security measure against the attacks. This paper presents a beamforming‐based feature extraction and relevance vector machine (RVM)‐based method for the classification of the attacker nodes in the cognitive radio network. Initially, the allocation of the Rayleigh channel is performed for the communication. The quaternary phase shift keying method is used for modulating the signals. After obtaining the modulated signal, the extraction of the beamforming‐based features is performed. The RVM classifier is used for predicting the normal nodes and attacker nodes. If the node is detected as an attacker node, then communication with that node is neglected. Particle swarm optimization is applied for predicting the optimal channel, based on the beamforming feature values. Then, signal communication with the normal nodes is started. Finally, the signal is demodulated. The signal‐to‐noise ratio and bit‐error rate values are computed to evaluate the performance of the proposed approach. The accuracy, sensitivity, and specificity of the RVM classifier method are higher than the support vector machine classifier. The proposed method achieves better performance in terms of throughput, channel sensing/probing rate, and channel access delay. Copyright © 2016 John Wiley & Sons, Ltd.
Adherence to a Mediterranean diet is associated with reduced risk of heart failure in men
Authors: Tektonidis Thanasis G. , Åkesson Agneta , Gigante Bruna , Wolk Alicja , Larsson Susanna C. 
Published: January 2016

AimsWe examined the hypothesis that high adherence to a Mediterranean diet reduces the risk of developing heart failure (HF) as well as the risk of death from HF.Methods and resultsThe study population comprised 37 308 men from the Cohort of Swedish Men who were free from cardiovascular disease at baseline. The modified Mediterranean diet (mMED) score was created from a self‐administered food frequency questionnaire, based on consumption of presumed beneficial/detrimental foods, on a 0–8 scale. Incident HF events were ascertained by linkage to the Swedish National Patient and the Cause of Death Registers. Relative risks (RR) with 95% confidence intervals (CI), adjusted for potential confounders, were estimated by Cox proportional hazards regression models. We identified 146 deaths from HF and 1269 incident HF events over a median follow‐up of 10.9 years (1998–2008). The mMED score was inversely associated with risk of HF (multivariable RR for the highest vs. lowest quartile 0.69, 95% CI 0.57, 0.83); the corresponding RR of HF mortality was 0.55 (95% CI 0.31, 0.98). The multivariable RR for every two‐point increment in the mMED score was 0.85 (95% CI 0.78, 0.91) for incidence of HF and 0.78 (95% CI 0.62, 0.98) for mortality from HF, respectively.ConclusionsHigh adherence to a Mediterranean diet was associated with a lower risk of HF and mortality from HF in men. Further studies are needed to replicate these findings in other populations.
Amino Acid Interleaved Layered Double Hydroxides as Promising Hybrid Materials for AA2024 Corrosion Inhibition
Authors: Stimpfling Thomas , Vialat Pierre , Hintze‐Bruening Horst , Keil Patrick , Shkirskiy Viacheslav , Volovitch Polina , Ogle Kevin , Leroux Fabrice 
Published: January 2016

AbstractVarious α‐amino acid (αAA) molecules were screened for their ability to retard the corrosion of AA2024 aluminum alloy substrate. The αAAs screened were L‐arginine (L‐Arg), L‐asparagine (L‐Asn), L‐cysteine (L‐Cys), L‐cystine, L‐histidine (L‐His), L‐methionine (L‐Met), L‐phenylalanine (L‐Phe), L‐serine (L‐ser), L‐tryptophan (L‐Trp), and L‐tyrosine (L‐Tyr). From their performances compared with that of the reference additives chromate and 2‐mercaptobenzothiazolate (MBT), L‐Cys and L‐Phe were selected, and their layered double hydroxide (LDH) interleaved derivatives were further scrutinized. Different LDH phases, namely, LiAl2, Mg2Al, MgZnAl, and Zn2Al, were tested as hosts for the inhibitor αAA substances, and the materials were characterized by XRD, FTIR spectroscopy, and SEM. The efficiencies and durable performances of the hybrid materials as an anticorrosion agents for aluminum alloy 2024 (AA2024) were demonstrated through direct current (DC) polarization measurements, and the evolution of the polarization resistance was recorded. The mechanism of inhibition focused on the most promising hybrid material LDH/L‐Cys and was tentatively explained as anion exchange and dissolution of the inorganic framework at the cathodic and anodic corrosion zones, respectively, with the particular occurrence of Cu‐rich intermetallic zones. The obtained results evidence that the LDH/L‐CYS assembly embedded in the polymer coating retards the corrosion process of the AA2024 substrate after a prolonged immersion time.
Catalytic Oxidative Coupling of Primary Amines under Air: A Flexible Route to Benzimidazole Derivatives
Authors: Nguyen Khac Minh Huy , Largeron Martine 
Published: January 2016

AbstractBenzimidazoles are of fundamental importance in chemistry and biology, and the development of efficient, environmentally benign methods for their preparation remains a key challenge for organic chemists. In a biomimetic approach inspired by copper amine oxidases, we disclose herein the scope and factors influencing the success of the cooperative action of CuBr2 as electron‐transfer mediator and a topaquinone‐like substrate‐selective catalyst in the oxidative cyclocondensation of primary amines with o‐aminoanilines. This one‐pot atom‐economic multistep process, which works under green conditions with ambient air as the terminal oxidant, low loadings of catalyst, and equimolar amounts of commercially available amine substrates, is particularly suitable for the preparation of 1,2‐disubstituted benzimidazoles. Furthermore, it allows the functionalization of nonactivated primary aliphatic amines, which are known to be challenging substrates for non‐enzymatic catalytic aerobic systems.
Recent Progress in Synthesis, Characterization and Evaluation of Non‐Precious Metal Catalysts for the Oxygen Reduction Reaction
Authors: Dombrovskis J. K. , Palmqvist A. E. C. 
Published: January 2016

AbstractThe oxygen reduction reaction (ORR) is usually catalyzed by precious metals. As the kinetics of the reaction are sluggish comparatively large amounts of precious metal are needed to achieve satisfactory reaction rates. This results in high cost of technologies utilizing the ORR, like low temperature fuel cells. Recent years have seen tremendous research efforts in the development of non‐precious metal catalysts (NPMCs) with a wide range of newly developed materials resulting in improved catalyst materials, an increased understanding of the ORR mechanism on NPMC materials and better knowledge of the active site structure. Here we summarize the developments from 2011 and onwards with a special focus on carbon‐based NPMCs developed for use in acid environments. We include explicit comparisons of PEMFC measurement results in all referenced studies and detailed information on the physical characterization methods used in various publications.