bluuebunny/crossref_metadata_2025_split huggingface dataset:
Titanocene(III)‐Catalyzed Three‐Component Reaction of Secondary Amides, Aldehydes, and Electrophilic Alkenes
Authors: Zheng Xiao , He Jiang , Li Heng‐Hui , Wang Ao , Dai Xi‐Jie , Wang Ai‐E , Huang Pei‐Qiang 
Published: September 2015

AbstractAn umpolung Mannich‐type reaction of secondary amides, aliphatic aldehydes, and electrophilic alkenes has been disclosed. This reaction features the one‐pot formation of CN and CC bonds by a titanocene‐catalyzed radical coupling of the condensation products, from secondary amides and aldehydes, with electrophilic alkenes. N‐substituted γ‐amido‐acid derivatives and γ‐amido ketones can be efficiently prepared by the current method. Extension to the reaction between ketoamides and electrophilic alkenes allows rapid assembly of piperidine skeletons with α‐amino quaternary carbon centers. Its synthetic utility has been demonstrated by a facile construction of the tricyclic core of marine alkaloids such as cylindricine C and polycitorol A.
An Experimentally Established Key Intermediate in Benzene Nitration with Mixed Acid
Authors: Koleva Gergana , Galabov Boris , Hadjieva Boriana , Schaefer Henry F. , Schleyer Paul von R. 
Published: September 2015

AbstractExperimental evidence is reported for the first intermediate in the classic SEAr reaction of benzene nitration with mixed acid. The UV/Vis spectroscopic investigation of the reaction showed an intense absorption at 320 nm (appearing as a band shoulder) arising from a reaction intermediate. Our theoretical modeling shows that the interaction between the two principal reactants with solvent (H2SO4) molecules significantly affects the structure of the initial complex. In this complex, a larger distance between the aromatic ring and nitronium ion precludes the possibility for electronic charge transfer from the benzene π‐system to the electrophile. The computational modeling of the potential energy surface reveals that the reaction favors a stepwise mechanism with intermediate formation of π‐ and σ‐ (arenium ion) complexes.
E–H Bond Activation of Ammonia and Water by a Geometrically Constrained Phosphorus(III) Compound
Authors: Robinson Thomas P. , De Rosa Daniel M. , Aldridge Simon , Goicoechea Jose M. 
Published: September 2015

AbstractThe synthesis of a phosphorus(III) compound bearing a N,N‐bis(3,5‐di‐tert‐butyl‐2‐phenoxy)amide ligand is reported. This species has been found to react with ammonia and water, activating the EH bonds in both substrates by formal oxidative addition to afford the corresponding phosphorus(V) compounds. In the case of water, both OH bonds can be activated, splitting the molecule into its constituent elements. To our knowledge, this is the first example of a compound based on main group elements that sequentially activates water in this manner.
Asymmetric Synthesis of Tetracyclic Pyrroloindolines and Constrained Tryptamines by a Switchable Cascade Reaction
Authors: de Graaff Corien , Bensch Lisa , Boersma Sjoerd J. , Cioc Răzvan C. , van Lint Matthijs J. , Janssen Elwin , Turner Nicholas J. , Orru Romano V. A. , Ruijter Eelco 
Published: September 2015

AbstractThe interrupted Fischer indole synthesis of arylhydrazines and biocatalytically generated chiral bicyclic imines selectively affords either tetracyclic pyrroloindolines or tricyclic tryptamine analogues depending on the reaction conditions. We demonstrate that the reaction is compatible with a variety of functional groups. The products are obtained in high optical purity and in reasonable to good yield. We present a plausible reaction mechanism to explain the observed reaction outcome depending on the stoichiometry of the acid mediator. To demonstrate the synthetic utility of our method, pharmaceutically relevant examples of both product classes were synthesized in highly efficient reaction sequences, including a phenserine analogue as a potential cholinesterase inhibitor and constrained tryptamine derivatives as selective inhibitors of the 5‐HT6 serotonin receptor and the TRPV1 ion channel.
Synthesis of Complexes with Abnormal “Protic” N‐Heterocyclic Carbenes
Authors: Jin Hanpeng , Tan Tristan Tsai Yuan , Hahn F. Ekkehardt 
Published: September 2015

AbstractNeutral 4‐iodo‐N‐ethylimidazole 3 oxidatively adds to [Pt(PPh3)4] to give, in the presence of different tetraalkylammonium salts, complexes trans‐[4], trans‐[5], and trans‐[6] containing an anionic C4‐bound heterocycle with an unsubstituted ring‐nitrogen atom. Complex trans‐[4] reacts with the proton source NH4I under protonation of the ring‐nitrogen atom to produce complex trans‐[7]I which bears an NH,NR‐substituted aNHC ligand. The reaction of trans‐[4] with CH3I yields the complex trans‐[8]I which has a classical aNHC ligand with two alkylated ring‐nitrogen atoms.
Enantioselective Copper(I)‐Catalyzed Alkynylation of Oxocarbenium Ions to Set Diaryl Tetrasubstituted Stereocenters
Authors: Dasgupta Srimoyee , Rivas Thomas , Watson Mary P. 
Published: September 2015

AbstractAn enantioselective, copper(I)‐catalyzed addition of terminal alkynes to isochroman ketals to set diaryl, tetrasubstituted stereocenters has been developed. The success of this reaction relies on identification of a Cu/PyBox catalyst capable of distinguishing the faces of the diaryl‐substituted oxocarbenium ion. This challenging transformation enables efficient conversion of readily available, racemic ketals into high‐value enantioenriched isochroman products with fully substituted stereogenic centers. High yields and enantiomeric excesses are observed for various isochroman ketals and an array of alkynes.
Reduction of Carbon Dioxide to Formate at Low Overpotential Using a Superbase Ionic Liquid
Authors: Hollingsworth Nathan , Taylor S. F. Rebecca , Galante Miguel T. , Jacquemin Johan , Longo Claudia , Holt Katherine B. , de Leeuw Nora H. , Hardacre Christopher 
Published: September 2015

AbstractA new low‐energy pathway is reported for the electrochemical reduction of CO2 to formate and syngas at low overpotentials, utilizing a reactive ionic liquid as the solvent. The superbasic tetraalkyl phosphonium ionic liquid [P66614][124Triz] is able to chemisorb CO2 through equimolar binding of CO2 with the 1,2,4‐triazole anion. This chemisorbed CO2 can be reduced at silver electrodes at overpotentials as low as 0.17 V, forming formate. In contrast, physically absorbed CO2 within the same ionic liquid or in ionic liquids where chemisorption is impossible (such as [P66614][NTf2]) undergoes reduction at significantly increased overpotentials, producing only CO as the product.
Symptom Assessment in Knee Osteoarthritis Needs to Account for Physical Activity Level
Authors: Lo Grace H. , McAlindon Timothy E. , Hawker Gillian A. , Driban Jeffrey B. , Price Lori Lyn , Song Jing , Eaton Charles B. , Hochberg Marc C. , Jackson Rebecca D. , Kwoh C. Kent , Nevitt Michael C. , Dunlop Dorothy D. 
Published: September 2015

ObjectivePain is not always correlated with severity of radiographic osteoarthritis (OA), possibly because people modify activities to manage symptoms. Measures of symptoms that consider pain in the context of activity level may therefore provide greater discrimination than a measure of pain alone. We undertook this study to compare discrimination provided by a measure of pain alone with that provided by combined measures of pain in the context of physical activity across radiographic OA severity levels.MethodsThis was a cross‐sectional study nested within the Osteoarthritis Initiative (OAI). The population was drawn from 2,127 persons enrolled in an OAI accelerometer monitoring substudy, including those with and those without knee OA. Two composite pain and activity knee symptom (PAKS) scores were calculated as the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain score (plus 1) divided by a physical activity measure (step count for the first PAKS score [PAKS1 score] and activity count for the second PAKS score [PAKS2 score]). Symptom score discrimination across Kellgren/Lawrence (K/L) grades was evaluated using histograms and quantile regression.ResultsA total of 1,806 participants (55.5% of whom were women) were included (mean ± SD age 65.1 ± 9.1 years, mean ± SD body mass index 28.4 ± 4.8 kg/m2). The WOMAC pain score, but not the PAKS scores, exhibited a floor effect. The adjusted median WOMAC pain scores by K/L grades 0–4 were 0, 0, 0, 1, and 3, respectively. The adjusted median PAKS1 scores were 24.9, 26.0, 32.4, 46.1, and 97.9, respectively, and the adjusted median PAKS2 scores were 7.2, 7.2, 9.2, 12.9, and 23.8, respectively. The PAKS scores had more statistically significant comparisons between K/L grades than did the WOMAC pain score.ConclusionSymptom assessments incorporating pain and physical activity did not exhibit a floor effect and were better able to discriminate radiographic severity than an assessment of pain alone, particularly in milder disease. Pain in the context of physical activity level should be used to assess knee OA symptoms.
Characterization of intracranial atherosclerotic stenosis using high‐resolution MRI study – rationale and design
Authors: Turan Tanya N. , LeMatty Todd , Martin Renee , Chimowitz Marc I. , Rumboldt Zoran , Spampinato M. Vittoria , Stalcup Seth , Adams Robert J. , Brown Truman 
Published: September 2015

AbstractBackgroundIntracranial atherosclerosis is a leading cause of stroke, but little is known about the composition of the intracranial atherosclerotic lesion and how intracranial plaque morphology is related to the risk of stroke. High‐resolution magnetic resonance imaging (HR MRI) has been used in patients with extracranial carotid atherosclerosis as an in vivo tool to identify, with high‐interrater agreement, histologically defined plaque components (i.e., intraplaque hemorrhage, fibrous cap, and lipid core), which have been shown to be predictors of recurrent stroke. With careful imaging the components of atherosclerotic plaque can be visualized in the intracranial arteries using HR MRI, but there are no reports of reproducibility or interrater reliability.Methods/Study designThe Characterization of intracranial atherosclerotic stenosis using high‐resolution MRI (CHIASM) study is a single‐center NIH‐funded prospective observational study, to (1) demonstrate high ‐interrater agreement for identifying intracranial plaque components on HR MRI, (2) determine the frequency of these components in symptomatic versus asymptomatic plaques, and (3) estimate the 1‐year rate of stroke in the territory of high‐risk plaque components. CHIASM will recruit 90 patients with 50–99% intracranial atherosclerosis to undergo HRMRI of the intracranial artery plaque at enrollment and 1‐year follow‐up. Both symptomatic and asymptomatic subjects will be recruited.ConclusionDetermination of good interrater reliability is an important first step in the development of HR MRI as a tool to predict risk in patients with intracranial atherosclerosis. This study will inform the design of future multicenter studies to determine the prevalence and prognosis of intracranial atherosclerotic plaque components. Such studies could lead to new understanding of the pathophysiological mechanisms of cerebral ischemia in patients with atherosclerotic intracranial stenosis, improvements in risk stratification, and potentially to new treatments of this common and serious disease.
Use of T1‐weighted/T2‐weighted magnetic resonance ratio images to elucidate changes in the schizophrenic brain
Authors: Iwatani Jun , Ishida Takuya , Donishi Tomohiro , Ukai Satoshi , Shinosaki Kazuhiro , Terada Masaki , Kaneoke Yoshiki 
Published: September 2015

AbstractIntroductionOne leading hypothesis suggests that schizophrenia (SZ) is a neurodevelopmental disorder caused by genetic defects in association with environmental risk factors that affect synapse and myelin formation. Recent magnetic resonance imaging (MRI) studies of SZ brain showed both gray matter (GM) reduction and white matter (WM) fractional anisotropy reduction. In this study, we used T1‐weighted (T1w)/T2‐weighted (T2w) MRI ratio images, which increase myelin‐related signal contrast and reduce receiver‐coil bias.MethodsWe measured T1w/T2w ratio image signal intensity in 29 patients with SZ and 33 healthy controls (HCs), and then compared them against bias‐corrected T1w images.ResultsMean T1w/T2w ratio signal intensity values across all SZ GM and WM voxels were significantly lower than those for the HC values (analysis of covariance with age, gender, handedness, and premorbid intelligence quotient as nuisance covariates). SZ mean WM T1w/T2w ratio values were related to Global Assessment of Functioning (GAF) scores and were inversely related to the positive psychotic symptoms of the Positive and Negative Syndrome Scale. Voxel‐based analysis revealed significantly lower T1w/T2w ratio image signal intensity values in the right ventral putamen in SZ GM. T1w image intensities did not differ between the SZ and HC groups.ConclusionsT1‐weighted/T2‐weighted ratio imaging increased the detectability of SZ pathological changes. Reduced SZ brain signal intensity is likely due to diminished myelin content; therefore, mapping myelin‐related SZ brain changes using T1w/T2w ratio images may be useful for studies of SZ brain abnormalities.
Understanding Ni Promotion of MoS2/γ‐Al2O3 and its Implications for the Hydrogenation of Phenanthrene
Authors: Schachtl Eva , Zhong Lei , Kondratieva Elena , Hein Jennifer , Gutiérrez Oliver Y. , Jentys Andreas , Lercher Johannes A. 
Published: September 2015

AbstractThe chemical composition and structure of NiMo sulfides supported on γ‐Al2O3 and its properties for hydrogenation of polyaromatic compounds is explored. The presence of Ni favors the formation of disperse octahedrally coordinated Mo in the oxide precursors and facilitates its reduction during sulfidation. This decreases the particle size of MoS2 (measured by transmission electron microscopy) and increases the concentration of active sites up to a Ni/(Mo+Ni) atomic ratio of 0.33. At higher Ni loadings, the size of the MoS2 did not decrease further, although the concentration of adsorption sites and accessible Ni atoms decreased. This is attributed to the formation of NiSx clusters at the edges of MoS2. Nickel also interacts with the support, forming separated NiSx clusters, and is partially incorporated into the γ‐Al2O3, forming a Ni‐spinel. The hydrogenation of phenanthrene follows two pathways; by adding one or two H2 molecules, 9,10‐dihydrophenanthrene or 1,2,3,4‐tetrahydrophenanthrene are formed as primary products. Only symmetric hydrogenation, leading to 9,10‐dihydrophenanthrene, was observed on unpromoted MoS2/γ‐Al2O3. In contrast, symmetric and deep hydrogenation (leading to 9,10‐dihydrophenanthrene and 1,2,3,4‐tetrahydrophenanthrene, respectively) occur with similar selectivity on Ni‐promoted MoS2/γ‐Al2O3. The rates of both pathways increase linearly with the concentration of Ni atoms in the catalyst. The higher rates for symmetric hydrogenation are attributed to increasing concentrations of reactive species at the surface, and deep hydrogenation is concluded to be catalyzed by Ni at the edge of MoS2 slabs.
Synthesis of Supported RhMo and PtMo Bimetallic Catalysts by Controlled Surface Reactions
Authors: Alba‐Rubio Ana C. , Sener Canan , Hakim Sikander H. , Gostanian Thomas M. , Dumesic James A. 
Published: September 2015

AbstractWe previously described a synthesis method to prepare bimetallic catalysts with narrow nanoparticle size and composition distributions by means of controlled surface reactions (CSR) between a reduced supported metal nanoparticle and an organometallic precursor of an oxophilic promoter metal. Herein, we report a comparison of such catalysts with those prepared by traditional incipient wetness impregnation. STEM/EDS analysis indicates that catalysts prepared by CSR exhibit more effective interaction of metals, thereby minimizing the undesirable formation of component‐rich nanoparticles and/or monometallic domains. Reaction kinetics studies using these bimetallic catalysts reveal that optimal conversion rates in a selective CO hydrogenolysis reaction (i.e., hydrogenolysis of 2‐(hydroxymethyl)tetrahydropyran to 1,6‐hexanediol) could be achieved using a lower amount of the oxophilic promoter metal for the catalysts prepared by the CSR approach, as compared to their impregnated counterparts.
Distribution of Metal Cations in Ni‐Mo‐W Sulfide Catalysts
Authors: Hein Jennifer , Gutiérrez Oliver Y. , Schachtl Eva , Xu Pinghong , Browning Nigel D. , Jentys Andreas , Lercher Johannes A. 
Published: September 2015

AbstractThe distribution of metal cations and the morphology of unsupported NiMo, NiW, and NiMoW sulfide catalysts were explored qualitatively and quantitatively. In the bi‐ and trimetallic catalysts, Mo(W)S2 nanoparticles are deposited on Ni sulfide particles of varying stoichiometry and sizes (crystalline Ni9S8, and Ni3S4 were identified). These nanoparticles are stacks of Mo(W)S2 slabs with varying size, degrees of bending and mismatch between the slabs. High resolution electron microscopy and X‐ray absorption spectroscopy based on particle modeling revealed a statistical distribution of Mo and W within individual layers in sulfide NiMoW, forming intralayer mixed Mo1−xWxS2. Ni is associated with MoS2, WS2, and Mo1−xWxS2 creating Ni‐promoted phases. The incorporation of Ni at the edges of the slabs was the highest for sulfide NiMoW. This high concentration of Ni in sulfide NiMoW, as well as its long bent Mo1−xWxS2 slabs, were paralleled by the highest activity for nitrogen and sulfur removal from model hydrocarbons such as o‐propylaniline and dibenzothiophene.
Preparation of Nickel Phosphide Hydrodesulfurization Catalysts Assisted by Supercritical Carbon Dioxide
Authors: Motos‐Pérez Blanca , Uzio Denis , Aymonier Cyril 
Published: September 2015

AbstractThe front cover artwork for Issue 21/2015 is a collaboration between the Catalysis & Separation Division, IFPEN and ICMCB–CNRS. The image shows a new preparation method to obtain silica‐supported nickel phosphide nanoparticles assisted by supercritical carbon dioxide and their application to hydrodesulfurization. See the Communication itself at http://dx.doi.org/10.1002/cctc.201500755.
Synthetic Routes to Coelenterazine and Other Imidazo[1,2‐a]pyrazin‐3‐one Luciferins: Essential Tools for Bioluminescence‐Based Investigations
Authors: Coutant Eloi P. , Janin Yves L. 
Published: September 2015

AbstractIn the last few decades, bioluminescent systems based on the expression of a luciferase and the addition of a luciferin to monitor the emission of light have become very important tools for biological investigations. A growing proportion of these systems use coelenterazine or analogues of imidazo[1,2‐a]pyrazine luciferins along with photoproteins or luciferases from sea creatures such as Aequorea, Renilla, Gaussia or Oplophorus. Central to the success of these tools are the synthetic pathways developed not only to prepare the naturally occurring luciferins, but also to design altered compounds that exhibit improved bioluminescence. Current work is indeed focused on the design of systems exhibiting extended luminescence (“glow” systems) or redshifted wavelengths, as well as constructions better adapted to conditions in cells or in vivo. This review describes the synthetic pathways used to prepare imidazo[1,2‐a]pyrazine luciferins along with the research efforts aimed at preparing analogues even better suited to the design of assays.
Drug Release Properties of a Series of Adenine‐Based Metal–Organic Frameworks
Authors: Oh Hyojae , Li Tao , An Jihyun 
Published: September 2015

AbstractThe drug uptake and release properties of a series of biomolecule‐based metal–organic frameworks (bMOF‐1, bMOF‐4, bMOF‐100, and bMOF‐102) have been studied. The bMOFs were loaded with the small molecule etilefrine hydrochloride and release profiles were collected in both Nanopure water and simulated body fluid (SBF). Each bMOF exhibited an initial burst of drug release at the initial stages of the experiment followed by a gradual release of the remaining drug molecules over time. bMOF‐1 released 50 % of the drug after 15 days and complete release at 80 days in SBF. bMOF‐4 released 50 % of the drug within two days and complete release at 49 days in SBF. bMOF‐100 and bMOF‐102 released 50 % of the drug after 4 h and complete release at 69 and 54 days in SBF, respectively.
Intrinsic Folding Proclivities in Cyclic β‐Peptide Building Blocks: Configuration and Heteroatom Effects Analyzed by Conformer‐Selective Spectroscopy and Quantum Chemistry
Authors: Alauddin Mohammad , Gloaguen Eric , Brenner Valérie , Tardivel Benjamin , Mons Michel , Zehnacker‐Rentien Anne , Declerck Valérie , Aitken David J. 
Published: September 2015

AbstractThis work describes the use of conformer‐selective laser spectroscopy following supersonic expansion to probe the local folding proclivities of four‐membered ring cyclic β‐amino acid building blocks. Emphasis is placed on stereochemical effects as well as on the structural changes induced by the replacement of a carbon atom of the cycle by a nitrogen atom. The amide A IR spectra are obtained and interpreted with the help of quantum chemistry structure calculations. Results provide evidence that the building block with a trans‐substituted cyclobutane ring has a predilection to form strong C8 hydrogen bonds. Nitrogen‐atom substitution in the ring induces the formation of the hydrazino turn, with a related but distinct hydrogen‐bonding network: the structure is best viewed as a bifurcated C8/C5 bond with the N heteroatom lone electron pair playing a significant acceptor role, which supports recent observations on the hydrazino turn structure in solution. Surprisingly, this study shows that the cis‐substituted cyclobutane ring derivative also gives rise predominantly to a C8 hydrogen bond, although weaker than in the two former cases, a feature that is not often encountered for this building block.
Oligoene‐Based π‐Helicenes or Dispiranes? Winding up Oligoyne Chains by a Multiple Carbopalladation/Stille/(Electrocyclization) Cascade
Authors: Milde Bastian , Leibeling Markus , Hecht Alexander , Jones Peter G. , Visscher Arne , Stalke Dietmar , Grunenberg Jörg , Werz Daniel B. 
Published: September 2015

AbstractA domino approach consisting of up to five consecutive steps to access either highly substituted dispiranes or π‐helicenes from oligoyne chains is reported. The domino sequence consists of several carbopalladation reactions, a Stille cross‐coupling to obtain the helicenes, and, depending on the steric demands of the helicene, a final 6π‐electrocyclization to afford the dispiranes. Formally, the latter transformation contravenes the Woodward–Hoffmann rules, as revealed by X‐ray crystallography of the dispirane. Additionally, the racemization barrier of the (Z,Z,Z)‐triene‐based helicene has been determined by a kinetic analysis and compared with results from density functional theory calculations. Characteristic points on the reaction coordinate were further analyzed according to their relaxed force constants (compliance constants).
Sponge‐Like Behaviour in Isoreticular Cu(Gly‐His‐X) Peptide‐Based Porous Materials
Authors: Martí‐Gastaldo Carlos , Warren John E. , Briggs Michael E. , Armstrong Jayne A. , Thomas K. Mark , Rosseinsky Matthew J. 
Published: September 2015

AbstractWe report two isoreticular 3D peptide‐based porous frameworks formed by coordination of the tripeptides Gly‐L‐His‐Gly and Gly‐L‐His‐L‐Lys to CuII which display sponge‐like behaviour. These porous materials undergo structural collapse upon evacuation that can be reversed by exposure to water vapour, which permits recovery of the original open channel structure. This is further confirmed by sorption studies that reveal that both solids exhibit selective sorption of H2O while CO2 adsorption does not result in recovery of the original structures. We also show how the pendant aliphatic amine chains, present in the framework from the introduction of the lysine amino acid in the peptidic backbone, can be post‐synthetically modified to produce urea‐functionalised networks by following methodologies typically used for metal–organic frameworks built from more rigid “classical” linkers.