bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and properties of poly(imide siloxane) block copolymers with different block lengths
Authors: Pei Xueliang , Chen Guofei , Fang Xingzhong 
Published: March 2013

AbstractSeveral poly(imide siloxane) block copolymers with the same bis(γ‐aminopropyl)polydimethylsiloxane (APPS) content were prepared. The polyimide hard block was composed of 4,4′‐oxydianiline and 3,3′,4,4′‐diphenylthioether dianhydride (TDPA), and the polysiloxane soft block was composed of APPS and TDPA. The length of polysiloxane soft block increased simultaneously with increasing the length of polyimide hard block. For better understanding the structure–property relations, the corresponding randomly segmented poly(imide siloxane) copolymer was also prepared. These copolymers were characterized by FT‐IR, 1H‐NMR, dynamic mechanical thermal analysis, thermogravimetric analysis, polarized optical microscope, rheology and tensile test. Two glass transition temperatures (Tg) were found in the randomly segmented copolymer, while three Tgs were found in the block copolymers. In addition, the Tgs, storage modulus, tensile modulus, solubility, elastic recovery, surface morphology and complex viscosity of the copolymers varied regularly with increasing the lengths of both blocks. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Hyperbranched poly(citric acid) and its application as anticancer drug delivery system
Authors: Adeli Mohsen , Rasoulian Bahram , Saadatmehr Farzaneh , Zabihi Fatemeh 
Published: March 2013

AbstractAs citric acid decomposes in its melting point, polycondensation of this monomer to prepare its polymers and copolymers is not possible. This study describes a feasible way to synthesize hyperbranched polyesters consisting of citric acid and glycerol monomers. In the first strategy, different ratios of citric acid and glycerol as AB3 and A3 monomers were mixed and heated step by step to avoid decomposition of citric acid. The produced water, as byproduct of polycondensation, was removed from the mixture by vacuum pump. Synthesized hyperbranched copolymers were characterized by nuclear magnetic resonance, gel permeation chromatography, thermogravimetric analysis, and dynamic light scattering. Ability of the synthesized hyperbranched polyesters to load and transfer cisplatin as an anticancer drug was investigated and it was found that their loading capacity is high and the prepared drug delivery systems are stable in saline buffer for several months. The toxicity of anticancer drug delivery systems against C26 cancer cell line was evaluated. Cisplatin loaded in polyesters showed lower IC50 value than the free cisplatin, confirming the efficacy of the synthesized citric acid–glycerol hyperbranched polyesters as biocompatible cargos to transport anticancer drugs. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Effect of salen‐metal complexes on thermosensitive reversibility of stimuli‐responsive water‐soluble poly(urethane amine)s
Authors: Li Gefei , Liu Yingliang , Zhang Ke , Shi Jun , Wan Xing , Cao Shaokui 
Published: March 2013

AbstractThe double stimuli responsive water‐soluble poly(urethane amine)s are prepared under supercritical carbon dioxide (scCO2) with renewable resources—carbon dioxide and natural α‐amino acids—as the starting materials. The urethane content, which will decide on the thermosensitive behavior of poly(urethane amine)s, is regulated not only by the substituent on aziridine derivatives but also by the coordinated metallic ion of Salen‐metal complexes as a catalyst. Interestingly, the thermosensitive reversibility is also changed through the application of Salen‐metal complexes in the copolymerization reaction of CO2 with aziridine derivatives. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Brief Report: Incidence of Selected Opportunistic Infections Among Children With Juvenile Idiopathic Arthritis
Authors: Beukelman Timothy , Xie Fenglong , Baddley John W. , Chen Lang , Delzell Elizabeth , Grijalva Carlos G. , Mannion Melissa L. , Patkar Nivedita M. , Saag Kenneth G. , Winthrop Kevin L. , Curtis Jeffrey R. ,   on behalf of the SABER Collaboration
Published: March 2013

AbstractObjectiveTo compare incidence rates of selected opportunistic infections among children with and children without juvenile idiopathic arthritis (JIA).MethodsUsing US national Medicaid administrative claims data from 2000 through 2005, we identified a cohort of children with JIA based on physician diagnosis codes and dispensed medications. We also identified a non‐JIA comparator cohort of children diagnosed as having attention deficit hyperactivity disorder (ADHD). We defined 15 types of opportunistic infection using physician diagnosis or hospital discharge codes; criteria for 7 of these types also included evidence of treatment with specific antimicrobial agents. We calculated infection incidence rates. The rates in the ADHD comparator cohort were standardized to the age, sex, and race distribution of the JIA cohort. We calculated incidence rate ratios (IRRs) with 95% confidence intervals (95% CIs) to compare infection rates.ResultsThe JIA cohort included 8,503 children with 13,990 person‐years of followup. The ADHD comparator cohort included 360,362 children with 477,050 person‐years of followup. When all opportunistic infections were considered together as a single outcome, there were 42 infections in the JIA cohort (incidence rate 300 per 100,000 person‐years; IRR 2.4 [95% CI 1.7–3.3] versus ADHD). The most common opportunistic infections among children with JIA were 3 cases of Coccidioides (incidence rate 21 per 100,000 person‐years; IRR 101 [95% CI 8.1–5,319] versus ADHD), 5 cases of Salmonella (incidence rate 35 per 100,000 person‐years; IRR 3.8 [95% CI 1.2–9.5]), and 32 cases of herpes zoster (incidence rate 225 per 100,000 person‐years; IRR 2.1 [95% CI 1.4–3.0]).ConclusionOpportunistic infections are rare among children with JIA. Nevertheless, children with JIA had a higher rate of opportunistic infections, including an increased rate of Coccidioides, Salmonella, and herpes zoster compared to children with ADHD.
Activation of Hydrogen Peroxide by Ionic Liquids: Mechanistic Studies and Application in the Epoxidation of Olefins
Authors: Markovits Iulius I. E. , Eger Wilhelm A. , Yue Shuang , Cokoja Mirza , Münchmeyer Christian J. , Zhang Bo , Zhou Ming‐Dong , Genest Alexander , Mink János , Zang Shu‐Liang , Rösch Notker , Kühn Fritz E. 
Published: March 2013

AbstractImidazolium‐based ionic liquids that contain perrhenate anions are very efficient reaction media for the epoxidation of olefins with H2O2 as an oxidant, thus affording cyclooctene in almost quantitative yields. The mechanism of this reaction does not follow the usual pathway through peroxo complexes, as is the case with long‐known molecular transition‐metal catalysts. By using in situ Raman, FTIR, and NMR spectroscopy and DFT calculations, we have shown that the formation of hydrogen bonds between the oxidant and perrhenate activates the oxidant, thereby leading to the transfer of an oxygen atom onto the olefin demonstrating the special features of an ionic liquid as a reaction environment. The influence of the imidazolium cation and the oxidant (aqueous H2O2, urea hydrogen peroxide, and tert‐butyl hydrogen peroxide) on the efficiency of the epoxidation of cis‐cyclooctene were examined. Other olefinic substrates were also used in this study and they exhibited good yields of the corresponding epoxides. This report shows the potential of using simple complexes or salts for the activation of hydrogen peroxide, owing to the interactions between the solvent medium and the active complex.
A Facile Method to Determine the Absolute Structure of Achiral Molecules: Supramolecular‐Tilt Structures
Authors: Tejedor Rosa María , Uriel Santiago , Graus Sara , Sierra Teresa , Serrano José Luis , Claramunt Rosa M. , López Concepción , Pérez‐Torralba Marta , Alkorta Ibon , Elguero José 
Published: March 2013

AbstractAchiral compounds 4‐methoxy‐4‐(p‐methoxyphenyl)cyclohexanoneethylene ketal (2), 4‐hydroxy‐4‐(p‐methoxy phenyl)cyclohexanoneethylene ketal (3), and 3,5‐dimethyl‐4‐nitropyrazole (4) crystallized in chiral structures and the samples showed an enantiomeric excess. We have determined the absolute structures of these compounds by using X‐ray diffraction with copper radiation at low temperatures. Moreover, we have also established the prevalent absolute structures in these samples, by comparing their calculated and solid‐state vibrational circular dichroism (VCD) spectra. The consistency of this method was confirmed by using (R,R)‐2,8‐diiodo‐4,10‐dimethyl‐6 H,12H‐5,11‐methano‐dibenzo[b,f][1,5]diazocine, Tröger′s base, (R,R)‐1, as a chiral compound of known absolute configuration.
UV‐Light‐Induced Hydrogen Transfer in Guanosine–Guanosine Aggregates
Authors: Hunger Katharina , Buschhaus Laura , Biemann Lars , Braun Michaela , Kovalenko Sergey , Improta Roberto , Kleinermanns Karl 
Published: March 2013

AbstractAggregates of a lipophilic guanine (G) derivative have been studied in n‐hexane by femtosecond‐to‐microsecond UV‐visible broadband transient absorption, stationary infrared and UV‐visible spectroscopy and by quantum chemical calculations. We report the first time‐resolved spectroscopic detection of hydrogen transfer in GG aggregates, which leads to (G−H). radicals by means of G+G− charge transfer followed by proton transfer. These radicals show a characteristic electronic spectrum in the range 300–550 nm. The calculated superimposed spectrum of the species that result from NH⋅⋅⋅N proton transfer agrees best with the experimental spectrum.
ChemInform Abstract: MgCuAl2‐Type Intermetallics REPdCd2 (RE: Ce, Pr, Nd, Sm).
Authors: Johnscher Michael , Peottgen Rainer 
Published: March 2013

AbstractThe title compounds are prepared by high‐frequency melting of the elements in Nb ampules followed by annealing at 900 K for 2 h.
ChemInform Abstract: Pyrochlore to Fluorite Transition: The Y2(Ti1‐xZrx)2O7 (0.0 ≤ x ≤ 1.0) System.
Authors: Norberg Stefan T. , Hull Stephen , Eriksson Sten G. , Ahmed Istaq , Kinyanjui Francis , Biendicho Jordi Jacas 
Published: March 2013

AbstractThe title system is characterized by neutron powder diffraction.
ChemInform Abstract: Hexagonally Ordered KLaF4 Host: Phase‐Controlled Synthesis and Luminescence Studies.
Authors: Ahmad Shahzad , Prakash G. Vijaya , Nagarajan R. 
Published: March 2013

AbstractThe title compound is synthesized by reaction of KF and La(acac)3 in MeOH at 65°C and by reaction of KF and La(O‐iPr)3 in a mixture of isopropyl alcohol and methanol at 65 °C.
ChemInform Abstract: CsHgInS3: A New Quaternary Semiconductor for γ‐Ray Detection.
Authors: Li Hao , Malliakas Christos D. , Liu Zhifu , Peters John A. , Jin Hosub , Morris Collin D. , Zhao Lidong , Wessels Bruce W. , Freeman Arthur J. , Kanatzidis Mercouri G. 
Published: March 2013

AbstractThe new layered title compound is synthesized by solid state reaction of In, HgS, Cs2S, and sulfur (silica tube, 600 °C for 24 h, 800 °C for 8 h; 70% yield).
ChemInform Abstract: The Synthesis and Structure of New Transition Metal Lithium Calcium Nitride Compounds.
Authors: Hunting Janet L. , Szymanski Marta M. , Lowalsick Amanda L. , Downie Craig M. , DiSalvo Francis J. 
Published: March 2013

AbstractThe the new nitrides (IV), (V), and (VII) are synthesized in a reactive lithium nitride flux.
ChemInform Abstract: High‐Pressure Synthesis and Characterization of the Alkali Metal Borate HP‐RbB3O5.
Authors: Sohr Gerhard , Neumair Stephanie C. , Huppertz Hubert 
Published: March 2013

AbstractThe title high‐pressure phase is synthesized in a Walker‐type multianvil apparatus (1000 °C, 6 GPa, 10 min).
ChemInform Abstract: A Ruthenium‐Catalyzed Coupling of Alkynes with 1,3‐Diketones.
Authors: Pennington‐Boggio Megan K. , Conley Brian L. , Williams Travis J. 
Published: March 2013

AbstractEne‐type coupling reactions of alkynes with 1,3‐diketones proceed at mild temperatures under air and in the presence of water.
ChemInform Abstract: Switchable Palladium‐Catalyst Reaction of Bromomethyl Sulfoxides, CO, and N‐Nucleophiles: Aminocarbonylation at Csp3 versus Oxidative Carbonylation of Amines.
Authors: Mollar Cristian , Ramirez de Arellano Carmen , Medio‐Simon Mercedes , Asensio Gregorio 
Published: March 2013

AbstractPd2(dba)3/ Xantphos‐catalyzed coupling of the sulfoxides (I) and (V) with amines and carbon monoxide allows a new and efficient access to amides of type (IV) and (VI).
ChemInform Abstract: An Iterative Method for the Synthesis of Symmetric Polyynes.
Authors: DeCicco Racquel C. , Black Allison , Li Lei , Goroff Nancy S. 
Published: March 2013

AbstractPolyynes containing 4‐7 CC bonds are prepared by Stille coupling of diiodopolyynes with alkynyltin reagents to give the corresponding dialkynylated products.
ChemInform Abstract: Vinyl Azides Derived from Allenes: Thermolysis Leading to Multisubstituted 1,4‐Pyrazines and Mn(III)‐Catalyzed Photochemical Reaction Leading to Pyrroles.
Authors: Sajna K. V. , Swamy K. C. Kumara 
Published: March 2013

AbstractTreatment of the allenes (I) an (XII) with TmsN3 leads to vinyl azides like (II).
ChemInform Abstract: Copper‐Catalyzed Arylation of Alkenyl Aziridines via Three‐Component Coupling Reaction Involving Alkynes and Benzyne.
Authors: Berti Francesco , Crotti Paolo , Cassano Giulio , Pineschi Mauro 
Published: March 2013

AbstractBenzyne, generated in situ, reacts with alkenyl aziridines and alkynes to provide allylic amines with good regioselectivity.
ChemInform Abstract: Arylation of Rhodium(II) Azavinyl Carbenes with Boronic Acids.
Authors: Selander Nicklas , Worrell Brady T. , Chuprakov Stepan , Velaparthi Subash , Fokin Valery V. 
Published: March 2013

AbstractA stereoselective arylation of triazole substrates with concomitant loss of N2 is developed to yield 2,2‐diaryl enamines.
ChemInform Abstract: Rhodium‐Catalyzed Direct C—H Amination of Benzamides with Aryl Azides. A Synthetic Route to Diarylamines.
Authors: Ryu Jaeyune , Shin Kwangmin , Park Sae Hume , Kim Ji Young , Chang Sukbok 
Published: March 2013

AbstractApplied to N‐alkylated benzamides, the method yields 2‐arylaminosubstituted N‐alkylbenzamide derivatives.
ChemInform Abstract: Hydrogen Bonding Directed Intermolecular Cope‐Type Hydroamination of Alkenes.
Authors: Zhao Shu‐Bin , Bilodeau Eric , Lemieux Valerie , Beauchemin Andre M. 
Published: March 2013

AbstractThe reaction of unactivated alkenes proceeds under mild conditions with a high Markovnikov selectivity and a series of vicinal diamine units is available.
ChemInform Abstract: Novel Prolinamide—Ureas as Organocatalysts for the Asymmetric Aldol Reaction.
Authors: Revelou Panagiota , Kokotos Christoforos G. , Moutevelis‐Minakakis Panagiota 
Published: March 2013

AbstractThe novel ligand PRA efficiently catalyzes the reaction of cyclic ketones with aromatic aldehydes.
ChemInform Abstract: Cu(O‐Tf)2‐Catalyzed Cross‐Coupling Reaction of 1,3‐Dicarbonyl Derivatives with 2‐Oxo‐1‐pyrrolidine Compounds.
Authors: Xu Hai‐Yan , Wang Shun‐Yi , Jiang Ran , Xu Xiao‐Ping , Chu Xue‐Qiang , Ji Shun‐Jun 
Published: March 2013

AbstractOptimized conditions are developed for the cross‐coupling with symmetrical and unsymmetrical 1,3‐dicarbonyl compounds.
ChemInform Abstract: Copper‐Mediated Trifluoromethylation of α‐Diazo Esters with TMSCF3: The Important Role of Water as a Promoter.
Authors: Hu Mingyou , Ni Chuanfa , Hu Jinbo 
Published: March 2013

AbstractCuCF3 is generated in solution and directly applied in the process where water is found be an efficient activating agent for the trifluoromethylation step.
ChemInform Abstract: Efficient Synthesis of Pentasubstituted Pyrroles via One‐Pot Reactions of Arylamines, Acetylenedicarboxylates, and 3‐Phenacylideneoxindoles.
Authors: Han Ying , Sun Yan , Sun Jing , Yan Chao‐Guo 
Published: March 2013

AbstractThe approach to substituted pyrroles (IV) involves sequential addition of arylamines to acetylenedicarboxylate (II), Michael addition of the resulting β‐enamino ester to substrates (I) followed by intramolecular nucleophilic addition and dehydration.
ChemInform Abstract: Palladium‐Catalyzed Synthesis of Benzimidazoles and Quinazolinones from Common Precursors.
Authors: Sadig Jessie E. R. , Foster Radleigh , Wakenhut Florian , Willis Michael C. 
Published: March 2013

AbstractBoth pathways, which produce the desired N‐heterocyclic skeletons, tolerate a broad spectrum of functionalities.
ChemInform Abstract: Synthesis and Antitumor Activity of α‐Aminophosphonates Containing Thiazole[5,4‐b]pyridine Moiety.
Authors: Gu Lijun , Jin Cheng 
Published: March 2013

AbstractTitle compounds (IVb) and (IVc) show the most efficient antitumor activities of the prepared compounds in the standard MTT assay.
ChemInform Abstract: Lewis Acid Triggered Selective Zincation of Chromones, Quinolones, and Thiochromones: Application to the Preparation of Natural Flavones and Isoflavones.
Authors: Klier Lydia , Bresser Tomke , Nigst Tobias A. , Karaghiosoff Konstantin , Knochel Paul 
Published: March 2013

AbstractRegioselective metallations of chromone (I), N‐methylquinolone (X), and thiochromone (XVI) are developed and investigated with a broad spectrum of subsequent metal‐catalyzed couplings.
ChemInform Abstract: Synthesis of 8‐Aryl‐Substituted Benzo[a]phenanthridine Derivatives by Consecutive Three‐Component Tandem Reaction and 6‐endo Carbocyclization.
Authors: Mandadapu Anil K. , Dathi Meena D. , Arigela Rajesh K. , Kundu Bijoy 
Published: March 2013

AbstractThe ICl‐promoted reaction of quinolines (I) introduces a 7‐iodo substituent into the benzo[a]phenanthridine skeleton and allows further functionalization by Pd‐catalyzed coupling reactions.
ChemInform Abstract: Palladium‐Catalyzed Regioselective [3 + 2] Annulation of Internal Alkynes and Iodopyranoquinolines with Concomitant Ring Opening.
Authors: Aggarwal Trapti , Jha Rajeev R. , Tiwari Rakesh K. , Kumar Sonu , Kotla Siva K. Reddy , Kumar Sushil , Verma Akhilesh K. 
Published: March 2013

AbstractUnsymmetrical internal alkynes such as (X) or (XII) generate selectively a single isomers [cf.(XI) or (XIII)].
ChemInform Abstract: A One‐Pot, Three‐Component Synthesis of Spiro[indoline‐isoxazolo[4′,3′:5,6]pyrido[2,3‐d]pyrimidine]triones in Water.
Authors: Rahmati Abbas , Khalesi Zahra 
Published: March 2013

AbstractA simple procedure is developed which allows the access to various biologically interesting heterocyclic systems.
ChemInform Abstract: Enantioselective Halocyclization Using Reagents Tailored for Chiral Anion Phase‐Transfer Catalysis.
Authors: Wang Yi‐Ming , Wu Jeffrey , Hoong Christina , Rauniyar Vivek , Toste F. Dean 
Published: March 2013

AbstractBrominated benzoxazines are obtained in high yields and with excellent enantioselectivities using the new brominating agent (I).
ChemInform Abstract: Gold(I)‐Catalyzed Regio‐ and Stereoselective 1,3‐Dipolar Cycloaddition Reactions of 1‐(1‐Alkynyl)cyclopropyl Oximes with Nitrones: A Modular Entry to Highly Substituted Pyrrolo[3,4‐d][1,2]oxazepines.
Authors: Zhang Yanqing , Zhang Junliang 
Published: March 2013

AbstractThe reaction proceeds with excellent diastereoselectivity and is effective only starting from the (E)‐substrates.
ChemInform Abstract: Stereoselective Synthesis of Pseudoglycosides Catalyzed by TeCl4 under Mild Conditions.
Authors: Freitas Juliano C. R. , Couto Tulio R. , Paulino Antonio A. S. , de Freitas Filho Joao R. , Malvestiti Ivani , Oliveira Roberta A. , Menezes Paulo H. 
Published: March 2013

AbstractIn the presence of TeCl4, the O‐glycosylation of glycal (I) proceeds with excellent α‐selectivity.
When directional selection reduces geographic variation in traits mediating species interactions
Authors: Benkman C. W. , Parchman T. L. 
Published: March 2013

AbstractAlthough we often focus on the causes of geographic variation, understanding processes that act to reduce geographic variation is also important. Here, we consider a process whereby adaptive foraging across the landscape and directional selection exerted by a conifer seed predator, the common crossbill (Loxia curvirostra), potentially act to homogenize geographic variation in the defensive traits of its prey. We measured seed predation and phenotypic selection exerted by crossbills on black pine (Pinus nigra) at two sites in the Pindos Mountains, Greece. Seed predation by crossbills was over an order of magnitude higher at the site where cone scale thickness was significantly thinner, which was also the cone trait that was the target of selection at the high predation site. Additional comparisons of selection differentials demonstrate that crossbills exert selection on black pine that is consistent in form across space and time, and increases in strength with increasing seed predation. If predators distribute themselves in relation to the defensive traits of their prey and the strength of selection predators exert is proportional to the amount of predation, then predators may act to homogenize trait variation among populations of their prey in a process analogous to coevolutionary alternation with escalation.
Stereoselective Synthesis of Polyhydroxycycloheptanes and Their Phosphate Derivatives from 8‐Oxabicyclo[3.2.1]octenes
Authors: Khlevin Dmitry A. , Sosonyuk Sergey E. , Proskurnina Marina V. , Zefirov Nikolay S. 
Published: March 2013

AbstractThe first directed synthesis of seven‐membered mono‐ and tris‐phosphates is described. The key steps involve a DIBAL‐H/DIBAL‐Cl‐mediated ring opening of 8‐oxabicyclo[3.2.1]octenes in the presence of [Ni(acac)2] and stereoselective syn‐dihydroxylation with NMO and OsO4. An enantioselective approach to ring opening has been examined with chiral phosphane. The phosphorylation of mono‐ and triols followed by deprotection gave the corresponding phosphates in high yields with structures similar to those of known inhibitors of myo‐inositol monophosphatase (IMPase) and myo‐inositol tris‐phosphate receptor ligands. The inhibitory activities of the monophosphates thus formed were evaluated against IMPase.
Increasing the Dimensionality of Modular Domino Reactions Triggered by Oxidative Cleavage: A Two‐Step Protocol Towards a Variety of Stereodefined Complex Oxygen Heterocycles
Authors: Castillo Rafael R. , Abet Valentina , Aquino Maurizio , Gandara Zoila , Retailleau Pascal , Arseniyadis Siméon 
Published: March 2013

AbstractArylcarbinol‐ and benzyl‐tethered octalin‐diols (1/1′), which differ only by the C11 substitution at the angular position, were transformed selectively into original scaffolds of high complexity through a two‐step protocol. Overall, the (11S*) configuration ensures an intramolecular Friedel–Crafts‐type C13–C4 bonding through a domino process triggered by oxidative cleavage, whereas the (11R*) configuration allows for a Marson‐type Friedel–Crafts C13–C2 bonding through an intramolecular nucleophilic acetal opening.