bluuebunny/crossref_metadata_2025_split huggingface dataset:
Iridium and Rhodium Complexes with the Hemilabile Ligand [2‐(1,3‐Dioxolane‐2‐yl)phenyl]diphenylphosphane – Behaviour in Solution and Structural Characterization
Authors: Barquín Montserrat , Ciganda Roberto , Garralda María A. , Ibarlucea Lourdes , Mendicute‐Fierro Claudio , Rodríguez‐Diéguez Antonio , Seco José M. 
Published: December 2012

Abstract[MCl(L2)]2 (M = Ir, L2 = 1,5‐cyclooctadiene; M = Rh, L2 = norbornadiene) reacts with [2‐(1,3‐dioxolane‐2‐yl)phenyl]diphenylphosphane (1) to afford [MCl(L2)(P~O)] (M = Ir, 2; M = Rh, 3), in which the ligand is P‐monodentate. Complex 3 reacts with AgClO4 to give [Rh(Nbd)(PO)]ClO4 (4), in which the ligand is P,O‐bidentate. Complex 2 is static at room temp., whereas 3 and 4 undergo intramolecular exchanges, which are fast at room temperature and slow at 223 K. The conformational changes in 4 are still fast at 223 K. Complexes 2–4 react with CO to afford trans‐[MCl(CO)(P~O)2] (M = Ir, 5; M = Rh, 6) or trans‐[Rh(CO)2(P~O)2]ClO4 (7). Cyclooctadiene complexes react with PPh2(o‐C6H4CHO) to afford [MClH(PPh2(o‐C6H4CO))(PO] (M = Ir, 8; M = Rh, 9), in which 1 is chelating. Complex 8 contains a single diastereomer, is static in the 303–213 K range and reacts with CO to form [IrClH(PPh2(o‐C6H4CO))(P~O)(CO)] (10). Complex 9 contains two diastereomers 9a/9b in a 95:5 ratio that undergo interconversion, which is slow at low temperature, and reacts with CO to undergo reductive elimination of aldehyde, cleavage of the Rh–O bond and scrambling of phosphanes. A mixture of trans‐[RhCl(CO)(κ1‐PPh2(o‐C6H4CHO))(P~O)] (11), 6 and trans‐[RhCl(CO)(κ1‐PPh2(o‐C6H4CHO))2] is formed. Bubbling of nitrogen transforms 11 back into 9. Compound 2 reacts with hydrogen to give the fluxional [IrCl(H)2(P~O)(PO)] (12) with trans P atoms and cis H atoms, which attains coalescence at 203 K. Complex 12 reacts with mono‐ or bidentate ligands to afford static [IrCl(H)2(P~O)2L] (L = CO, 13; py, 14; nPrNH2, 15) or [Ir(H)2(P~O)2(en)]BPh4 (16, en = ethylenediamine). Abstraction of halide from 12 affords [Ir(H)2(PO)2]BPh4 (17), which is fluxional owing to interconversion between only two of the possible four diastereomers, for which ΔH‡ = 54.7 ± 0.7 kJ mol–1 and ΔS‡ = 4.7 ± 0.2 J K–1 mol–1. The X‐ray structures of 8, 15 and 16 are also reported.
Synthesis and Structure of Seven‐Membered Metallacycloalkynes
Authors: Suzuki Noriyuki , Tsuchiya Takashi , Aihara Naoto , Iwasaki Masakazu , Saburi Masahiko , Chihara Teiji , Masuyama Yoshiro 
Published: December 2012

AbstractSeven‐membered metallacycloalkyne compounds were synthesized. The reaction of the zirconocene–ethylene complex and (Z)‐1,4‐bis(trimethylsilyl)buta‐1,2,3‐triene gave a mixture of 1‐zirconacyclopent‐3‐yne and 1‐zirconacyclohept‐3‐yne. In contrast, zirconocene–alkyne complexes, such as those of 1‐(trimethylsilyl)prop‐1‐yne and diphenylacetylene, gave 1‐zirconacyclohept‐2‐en‐5‐yne in good yields. Consideration of structural parameters suggests that both a seven‐membered cyclic alkyne and a five‐membered structure contribute to generation of this complex. Coupling of benzyne and [3]cumulenes on a metal was also found to afford the corresponding metallacycles.
Synthesis and Characterization of [Mo3S4(NDABu)(HNDABu)2]3– and [Mo3S4(HNDAPr)3]2– Anions as Building Blocks for Organic–Inorganic Hybrid Solids
Authors: Duval Sylvain , Dumur Frédéric , Guénée Laure , Marrot Jérôme , Simonnet‐Jégat Corine , Cadot Emmanuel 
Published: December 2012

AbstractThe polymetallic cation [Mo3S4(H2O)9]4+ was used as an inorganic precursor to generate new hybrid organic–inorganic chalcogenide clusters. Three organic compounds with flexible and hanging arms were synthesized and investigated as ligands for coordination complexes with the rigid and electroactive inorganic {Mo3S4} unit. Interestingly, the {Mo3S4} core formed hybrid structures with the flexible H3NDABu [N‐(3‐carboxypropyl)iminodiacetic acid] and H3NDAPr [N‐(2‐carboxyethyl)iminodiacetic acid] ligands, which were characterized by X‐ray crystallography. Surprisingly, no crystals were isolated, when the more rigid H3NDABn [N‐(4‐methoxycarbonylbenzyl)iminodiacetic acid] ligand was used. The two coordination complexes [Mo3S4(NDABu)(HNDABu)2]3– and [Mo3S4(HNDAPr)3]2– were characterized by X‐ray diffraction (XRD), IR spectroscopy, thermal gravimetric analysis (TGA), 1H NMR spectroscopy, elemental analysis, and electrochemistry. The organic ligands H3NDABu, H3NDAPr, and H3NDABn were characterized by XRD, IR, HR mass, and 13C and 1H NMR spectroscopy. [Mo3S4(NDABu)(HNDABu)2]3– and [Mo3S4(HNDAPr)3]2– constitute promising preformed building blocks to generate new organic–inorganic hybrid molecular or extended materials.
One‐Pot Synthesis of Alkyl Styryl Sulfides Free from Transition Metal/Ligand Catalyst and Thiols
Authors: Heredia Adrián A. , Peñéñory Alicia B. 
Published: December 2012

AbstractA new protocol for the one‐pot synthesis of styryl alkyl sulfides was developed. This methodology involves the in situ generation of thiolate anions by nucleophilic substitution between potassium thioacetate and alkyl halides followed by fragmentation. Further reactions of these thiolate anions with substituted (E,Z)‐β‐styryl halides gave the corresponding sulfides with retention of stereochemistry in good to excellent yields. This procedure does not require a metal catalyst, it proceeds under mild conditions and in short times, and it is free from malodorous and air‐sensitive alkyl thiols.
Asymmetric Organocatalytic 1,4‐Addition Reactions Starting from Enals with gem‐Difluoroalkyl Side Chains
Authors: Khalaf Ali , Grée Danielle , Abdallah Hassan , Jaber Nada , Hachem Ali , Grée René 
Published: December 2012

Abstractgem‐Difluoroenals are excellent substrates for asymmetric organocatalytic 1,4‐additions of thiols and anilines. By using diarylsilylprolinol ether as a catalyst, good to excellent yields with ee values in the same range (up to 98 %) were obtained. The CF2R group strongly activates the enals towards these organocatalytic additions.
Cardiomyocyte proliferation and progenitor cell recruitment underlie therapeutic regeneration after myocardial infarction in the adult mouse heart
Authors: Malliaras Konstantinos , Zhang Yiqiang , Seinfeld Jeffrey , Galang Giselle , Tseliou Eleni , Cheng Ke , Sun Baiming , Aminzadeh Mohammad , Marbán Eduardo 
Published: December 2012

AbstractCardiosphere‐derived cells (CDCs) have been shown to regenerate infarcted myocardium in patients after myocardial infarction (MI). However, whether the cells of the newly formed myocardium originate from the proliferation of adult cardiomyocytes or from the differentiation of endogenous stem cells remains unknown. Using genetic fate mapping to mark resident myocytes in combination with long‐term BrdU pulsing, we investigated the origins of postnatal cardiomyogenesis in the normal, infarcted and cell‐treated adult mammalian heart. In the normal mouse heart, cardiomyocyte turnover occurs predominantly through proliferation of resident cardiomyocytes at a rate of ∼1.3–4%/year. After MI, new cardiomyocytes arise from both progenitors as well as pre‐existing cardiomyocytes. Transplantation of CDCs upregulates host cardiomyocyte cycling and recruitment of endogenous progenitors, while boosting heart function and increasing viable myocardium. The observed phenomena cannot be explained by cardiomyocyte polyploidization, bi/multinucleation, cell fusion or DNA repair. Thus, CDCs induce myocardial regeneration by differentially upregulating two mechanisms of endogenous cell proliferation.→See accompanying article http://dx.doi.org/10.1002/emmm.201202345
Spliceosome integrity is defective in the motor neuron diseases ALS and SMA
Authors: Tsuiji Hitomi , Iguchi Yohei , Furuya Asako , Kataoka Ayane , Hatsuta Hiroyuki , Atsuta Naoki , Tanaka Fumiaki , Hashizume Yoshio , Akatsu Hiroyasu , Murayama Shigeo , Sobue Gen , Yamanaka Koji 
Published: December 2012

AbstractTwo motor neuron diseases, amyotrophic lateral sclerosis (ALS) and spinal muscular atrophy (SMA), are caused by distinct genes involved in RNA metabolism, TDP‐43 and FUS/TLS, and SMN, respectively. However, whether there is a shared defective mechanism in RNA metabolism common to these two diseases remains unclear. Here, we show that TDP‐43 and FUS/TLS localize in nuclear Gems through an association with SMN, and that all three proteins function in spliceosome maintenance. We also show that in ALS, Gems are lost, U snRNA levels are up‐regulated and spliceosomal U snRNPs abnormally and extensively accumulate in motor neuron nuclei, but not in the temporal lobe of FTLD with TDP‐43 pathology. This aberrant accumulation of U snRNAs in ALS motor neurons is in direct contrast to SMA motor neurons, which show reduced amounts of U snRNAs, while both have defects in the spliceosome. These findings indicate that a profound loss of spliceosome integrity is a critical mechanism common to neurodegeneration in ALS and SMA, and may explain cell‐type specific vulnerability of motor neurons.
ZrC–C and ZrO2–C as Novel Supports of Pd Catalysts for Formic Acid Electrooxidation
Authors: Qu W.‐L. , Wang Z.‐B. , Sui X.‐L. , Gu D.‐M. , Yin G.‐P. 
Published: December 2012

AbstractThe Pd/ZrC–C and Pd/ZrO2–C catalysts with zirconium compounds ZrC or ZrO2 and carbon hybrids as novel supports for direct formic acid fuel cell (DFAFC) have been synthesized by microwave‐assisted polyol process. The Pd/ZrC–C and Pd/ZrO2–C catalysts have been characterized by X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), energy dispersive analysis of X‐ray (EDAX), transmission electron microscopy (TEM), and electrochemical measurements. The physical characteristics present that the zirconium compounds ZrC and ZrO2 may promote the dispersion of Pd nanoparticles. The results of electrochemical tests show that the activity and stability of Pd/ZrC–C and Pd/ZrO2–C catalysts show higher than that of Pd/C catalyst for formic acid electrooxidation due to anti‐corrosion property of zirconium compounds ZrC, ZrO2, and metal–support interaction between Pd nanoparticles and ZrC, ZrO2. The Pd/ZrC–C catalyst displays the best performance among the three catalysts. The peak current density of formic acid electrooxidation on Pd/ZrC–C electrode is nearly 1.63 times of that on Pd/C. The optimal mass ratio of ZrC to XC‐72 carbon is 1:1 in Pd/ZrC–C catalyst with narrower particle size distribution and better dispersion on surface of the mixture support, which exhibits the best activity and stability for formic acid electrooxidation among all the samples.
Coordination of Ligands That Contain Thiocarbonyl, Carbonyl, or Thiolate Functionalities to Complex Fragments of Palladium in Various Oxidation States
Authors: Dobrzańska Liliana , Stander‐Grobler Elzet , Strasser Christoph E. , Cronje Stephanie , Raubenheimer Helgard G. 
Published: December 2012

AbstractTwo phosphine ligands of [Pd(PPh3)4] were substituted by π(CS) coordination of 4‐bromodithiobenzoic acid methyl ester resulting in complex 1. The same ester, after alkylation, afforded the dicationic complex bis(μ‐methanethiolato)tetrakis(triphenylphosphine)dipalladium(2+) bis(tetrafluoroborate) (2) from the same palladium source. A related thiolato‐bridged complex, bis(μ‐methanethiolato)bis(1‐methylpyridin‐2(1H)‐ylidene)bis(triphenylphosphine)dipalladium(2+) bis(tetrafluoroborate) (4) and the trinuclear cluster tris(μ‐methanethiolato)tris(triphenylphosphine)tripalladium(+)(3PdPd) (5) resulted from treatment of a known cationic pyridinylidene complex with MeSLi. The double oxidative substitution reaction of [Pd(PPh3)4] with 1,5‐dichloro‐9,10‐anthraquinone afforded trans‐dichloro[μ‐(9,10‐dihydro‐9,10‐dioxoanthracene‐1,5‐diyl)]tetrakis(triphenylphosphine)dipalladium (6). Some of these complexes could be fully characterized by 1H‐, 13C‐, and 31P‐NMR spectroscopy, mass spectrometry, and elemental analysis. The crystal and molecular structures of all of them, and of trans‐bis(1,3‐dihydro‐1,3‐dimethyl‐2H‐imidazol‐2‐ylidene)diiodopalladium (3), were determined by single‐crystal X‐ray diffraction.
Ab initio MO Theory – An Important Tool in Foldamer Research: Prediction of Helices in Oligomers of ω‐Amino Acids
Authors: Baldauf Carsten , Hofmann Hans‐Jörg 
Published: December 2012

AbstractThe enormous developments of computer technologies allow the broad employment of ab initio MO theory in foldamer research. In this review, we demonstrate the efficiency and reliability of ab initio MO methods for the description of the helix formation in oligomers of ω‐amino acids on the basis of representative examples. Thus, ab initio MO theory successfully accompanies foldamer research by confirmation and interpretation of experimental results and stimulation of future experiments. The high predictive power of the methods opens the way to novel structure classes with special properties. Nowadays, ab initio MO theory has become an inherent part in the arsenal of methods applied in foldamer research.
Fluorine in Peptides: The Synthesis of α‐Fluoro‐β‐Amino Dipeptides by Direct Deoxofluorination/Rearrangement of N‐Seryl Dipeptides
Authors: Smith Daniel L. , Slawin Alexandra M. Z. , O'Hagan David 
Published: December 2012

AbstractThis article describes the stereo‐ and regioselectivity of the deoxofluorination of N‐terminal dipeptides bearing a serine residue to generate, after rearrangement, α‐fluoro‐β‐amine‐terminated dipeptides. The ratio of the rearranged α‐fluorinated regioisomer is increased, relative to the non‐rearranged β‐fluoro isomer, with N‐alkylated amides. Otherwise, an intramolecular H‐bond between the free amine and the amide NH suppresses formation of the key aziridinium intermediate required for α‐fluorination. N‐Methyl and N‐allyl amides give exclusively α‐fluorination products. Subsequent deprotection of the N‐allyl amide to give a α‐fluoro‐β‐amino dipeptide product is demonstrated.
Main‐Chain Scission of a Charged Fifth‐Generation Dendronized Polymer
Authors: Yu Hao , Schlüter A. Dieter , Zhang Baozhong 
Published: December 2012

AbstractDuring divergent synthesis of the next higher‐generation dendronized polymer (DP), the fifth‐generation DP, PG5, with a number‐average degree of polymerization, (i.e., number of monomeric units) Pn, of ca. 500 underwent main‐chain scission. This happened in the step when its peripheral Boc groups were removed by the treatment with trifluoroacetic acid (TFA), and thus a heavily charged polyelectrolyte formed as an intermediate. Atomic Force Mircoscopy (AFM) analysis of the product after drop‐casting onto mica showed a large majority of short deprotected PG5 chains with Pn of ca. 40, as well as some smaller features that by MALDI‐TOF mass spectrometry and 1H‐NMR spectroscopy were assigned to the hypothetical monomer, deprotected MG5. This behavior is compared to a recently reported main‐chain scission of a closely related PG5 which, however, resulted in significantly longer fragments. While this difference cannot yet be fully explained, questions are formulated which will guide future research.
2,3,10,11‐Tetrahydroxytetraphenylene and Its Application in Molecular Recognition
Authors: Cui Jian‐Fang , Chen Chao , Gao Xiang , Cai Zong‐Wei , Han Jian‐Wei , Wong Henry N. C. 
Published: December 2012

AbstractA rationally designed 2,3,10,11‐tetrahydroxytetraphenylene (1) has been synthesized. Employing 1 as a building block, a structurally novel tweezer‐like host 2 containing dibenzo‐24‐crown‐8 moieties has been prepared. Host 2 showed excellent molecular‐recognition ability toward paraquat (=1,1′‐dimethyl‐4,4′‐bipyridinium dichloride) derivative 3a to form a 1 : 1 stable complex in solution.
A Capture‐and‐Release Catalytic Flow System
Authors: Suzuki Yoshikazu , Laurino Paola , McQuade D. Tyler , Seeberger Peter H. 
Published: December 2012

AbstractSupported transition‐metal catalysts offer the promise of catalyst reuse in order to make chemical transformations more environmentally friendly and less expensive; however, catalysts that are supported on insoluble scaffolds often exhibit significantly reduced selectivities and rates. A capture/release strategy that unites the benefits of heterogeneous and homogeneous catalysis would overcome these current shortcomings. Herein, we report on a novel capture‐and‐release flow system that takes advantage of a non‐covalent pyrenesingle wall nanotube (SWNT) interaction. We demonstrate that a Pd complex containing one or two pyrene arms is captured and released from a SWNT column at different rates and can be utilized for the homogeneous catalysis of Suzuki and Heck reactions.
Carboboration Reactions of 1,2‐Bis[(diarylphosphino)ethynyl]benzenes with Tris(pentafluorophenyl)borane
Authors: Liedtke René , Kehr Gerald , Fröhlich Roland , Daniliuc Constantin G. , Wibbeling Birgit , Petersen Jeffrey L. , Erker Gerhard 
Published: December 2012

AbstractThe 1,2‐bis[(diarylphosphino)ethynyl]benzene derivatives 1a (R=Ph) and 1b (R=o‐tolyl) undergo 1,1‐carboboration at one of their acetylene units upon treatment with (C6F5)3B at elevated temperature to give the products 5a and 5b, respectively. At room temperature, we observed the formation of the corresponding phosphireniumborate zwitterions, 7a and 7b, respectively, which may be intermediates of the 1,1‐carboboration reactions. The reaction of the more bulky 1,2‐bis[(dimesitylphosphino)ethynyl]benzene 1c with (C6F5)3B takes a different course. At 110°, we observed the complete conversion to the benzopentafulvene derivative 8 which is probably formed in a typical carbocation rearrangement sequence after the initial (C6F5)3B Lewis acid‐addition step. The compounds 5a, 5b, 7b, and 8 were characterized by X‐ray crystal‐structure analyses.
Organocatalysis of CN/CN and CC/CN Exchange in Dynamic Covalent Chemistry
Authors: Wilhelms Nadine , Kulchat Sirinan , Lehn Jean‐Marie 
Published: December 2012

AbstractThe reversibly formed CN bond plays a very important role in dynamic covalent chemistry and the CN/CN exchange of components between different imine constituents to create dynamic covalent libraries has been extensively used. To facilitate diversity generation, we have investigated an organocatalyzed approach, using L‐proline as catalyst, to accelerate the formation of dynamic libraries of [n×n] imine components. The organocatalysis methodology has also been extended, under somewhat modified conditions, to reversible CC/CN exchange processes between Knoevenagel derivatives of barbituric acid and imines, allowing for the generation of increased diversity.
The Structural Characterization of Folded Peptides Containing the Conformationally Constrained β‐Amino Acid Residue β2,2Ac6c
Authors: Basuroy Krishnayan , Karuppiah Vasantham , Shamala Narayanaswamy , Balaram Padmanabhan 
Published: December 2012

AbstractBackbone alkylation has been shown to result in a dramatic reduction in the conformational space that is sterically accessible to α‐amino acid residues in peptides. By extension, the presence of geminal dialkyl substituents at backbone atoms also restricts available conformational space for β and γ residues. Five peptides containing the achiral β2,2‐disubstituted β‐amino acid residue, 1‐(aminomethyl)cyclohexanecarboxylic acid (β2,2Ac6c), have been structurally characterized in crystals by X‐ray diffraction. The tripeptide Boc‐Aib‐β2,2Ac6c‐Aib‐OMe (1) adopts a novel fold stabilized by two intramolecular H‐bonds (C11 and C9) of opposite directionality. The tetrapeptide Boc‐[Aib‐β2,2Ac6c]2‐OMe (2) and pentapeptide Boc‐[Aib‐β2,2Ac6c]2‐Aib‐OMe (3) form short stretches of a hybrid αβ C11 helix stabilized by two and three intramolecular H‐bonds, respectively. The structure of the dipeptide Boc‐Aib‐β2,2Ac6c‐OMe (5) does not reveal any intramolecular H‐bond. The aggregation pattern in the crystal provides an example of an extended conformation of the β2,2Ac6c residue, forming a ‘polar sheet’ like H‐bond. The protected derivative Ac‐β2,2Ac6c‐NHMe (4) adopts a locally folded gauche conformation about the CβCα bonds (θ=−55.7°). Of the seven examples of β2,2Ac6c residues reported here, six adopt gauche conformations, a feature which promotes local folding when incorporated into peptides. A comparison between the conformational properties of β2,2Ac6c and β3,3Ac6c residues, in peptides, is presented. Backbone torsional parameters of H‐bonded αβ/βα turns are derived from the structures presented in this study and earlier reports.
The Effects of Scenario Planning on Participant Perceptions of Learning Organization Characteristics
Authors: Haeffner Melissa , Leone Deanna , Coons Laura , Chermack Thomas 
Published: December 2012

AbstractScenario planning is often used by organizations to think about future uncertainties. However, what it does in terms of changing perceptions is difficult to assess and quantify. To address this need, this article builds on previous studies documenting the effectiveness of scenario planning. Specifically, this article contributes to the data on perceptions of learning organization characteristics. This study compiles quantitative data gathered from 133 individuals working in 10 United States companies who participated in scenario planning. The Dimensions of the Learning Organization Questionnaire (DLOQ) instrument was used in a pre‐ and post‐test research design and differences were analyzed using a t‐test. Results show a positive relationship between scenario planning and improved perceptions of learning organization characteristics for six of the seven dimensions of the DLOQ. Interpretation of the results suggests that scenario planning can change participants' views of their organizations' adaptive learning characteristics.
Synthesis and characterization of thermoresponsive copolymers for drug delivery
Authors: Aerry Swati , De Arnab , Kumar Ajeet , Saxena Amit , Majumdar D. K. , Mozumdar Subho 
Published: December 2012

AbstractWe report the synthesis and characterization of two nontoxic, thermogelling drug delivery systems which are liquid at room temperatures but become a gel at physiological temperature (37°C) potentially leading to release of a drug molecule. We selected temperature as the stimulus for drug release as it is physiologically invariant. A free radical polymerization of N‐isopropylacrylamide (NIPAM) and N‐vinylpyrrolidone (VP) was carried out under nitrogen atmosphere in double‐distilled water at two different temperatures (30°C and 70°C), and the copolymers obtained were characterized by various analytical techniques. The molar ratios of the two monomers were altered with increasing NIPAM content and their cloud point temperature or least critical solution temperature (LCST) was determined. The copolymer at 9:1 ratio of NIPAM to VP resulted in the formation of nanoparticle‐based gel (NG1) at 30°C; however, at 70°C, a microgel (MG1) was formed. The LCST of the nanogel and microgel was 33.5–34°C and 36.5–37°C, respectively. Thus, both the copolymers are water soluble at room temperature, but distinct phases appear at physiological temperatures. We hypothesized that these copolymers on entrapment with a drug could be used for topical application to the skin or eye for controlled drug delivery applications. Toxicological studies revealed that the copolymers are nontoxic in HeLa cells. Finally, our experiments show that a model drug [bovine serum albumin (BSA)] is released at 37°C with zero‐order kinetics and confirmed using multiple well‐known mathematical models. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2013.