bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and Structural Studies of Rhenium(V) Complexes Stabilized by a Monoanionic Cyclen Ligand
Authors: Xavier Catarina , Paulo António , Domingos Angela , Santos Isabel 
Published: January 2004

AbstractThe novel cationic (oxo)ReV complexes [ReO(cyclen‐H)Cl]X [X = Cl (3a), BPh4 (3b)] and [ReO(cyclen‐H)I]I (4) have been prepared by treating cyclen (1,4,7,10‐tetrazacyclododecane) with (Bu4N)[ReOCl4] (1) and cis‐[ReO2I(PPh3)2] (2), respectively. The X‐ray structural analyses of 3a and 4, as well as 1H NMR spectroscopy, showed that the macrocyclic ligand is coordinated in the unprecedented monoanionic form. 1H and 13C NMR spectroscopy also demonstrated that 3a,b and 4 exist in solution as single isomers. To the best of our knowledge, 3a and 4 are the first examples of structurally characterized oxo complexes of d transition elements with cyclen bound to the metal atom through one amido and three amine groups. In both complexes, the geometry around the ReV center is best described as distorted octahedral. The terminal oxo and halo ligands are coordinated in relative cis positions, and the amido and three amino nitrogen atoms from cyclen occupy the four remaining coordination positions. The Re−N(amido) bonds [1.894(9) Å in 3a and 1.888(12) Å in 4] are trans to the halo ligands and, as expected, are considerably shorter than the Re−N(amine) bonds, which span from 2.110(6) to 2.246(8) Å and from 2.124(8) to 2.268(10) Å for cations the cations of 3a and 4, respectively. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
(Neocuproin)zinc Thiolates: Attempts at Modeling Cobalamin‐Independent Methionine Synthase
Authors: Seebacher Jan , Ji Mian , Vahrenkamp Heinrich 
Published: January 2004

AbstractSeveral new complexes [(neo)Zn(SR)2] [neo = neocuproin (2,9‐dimethylphenanthroline)] have been synthesized and structurally characterised. They react in a stepwise fashion with the alkylating agents CH3I and (CH3)2SO4 to afford the thioethers CH3SR and first the mixed complexes [(neo)Zn(SR)X] (X = I, CH3SO4) and then [(neo)ZnX2]. Similar alkylations occur with benzyl iodide, but not with trimethyl phosphate in nonpolar media. Under these conditions, thiolate exchange with [PPN]SR does not occur which indicates that the alkylations take place at the zinc‐bound thiolates. In polar solvents (methanol, DMSO), thiolate exchange occurs readily, and at higher temperatures (CH3)3PO4 also acts as an alkylating agent which indicates that under these conditions free thiolate is available in solution. Qualitative kinetic data support the associative alkylation mechanism in nonpolar media and the change of mechanism in polar media. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Novel Room Temperature Inorganic Ionic Liquids
Authors: Dai Liyi , Yu Shuyuan , Shan Yongkui , He Mingyuan 
Published: January 2004

AbstractNew inorganic ionic liquids (IIL) consisting of an inorganic polyoxometalate anion with the Keggin structure and a sodium cation, that is Na13[Ln(TiW11O39)2]·xH2O [where Ln = lanthanide (type 1)], Na5[MTiW11O39]·xH2O and Na6[MTiW11O39]·xH2O [where M = transition metal (type 2)], were prepared and their physicochemical properties were investigated. These ionic liquids were characterized by NMR and IR spectroscopy and by elemental analysis. Their melting point, viscosity, conductivity, thermal stability, and miscibility with water and organic solvents were determined. When the temperature is below ambient temperature (about 298 K) these ionic liquids are almost immiscible with water. When the temperature is raised, the solubility of the new ionic liquids increases sharply. The influence of the size and of the charge density of both the cations and anions on these properties was examined. The most remarkable feature of IILs is that water is their indispensable component. The role of the water molecule in ionic liquids is similar to that of crystalline water in hydrated compounds. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Solid‐State Models of Ion Solvation: Crystal Structures of Dimethyl Sulfoxide Solvates of Alkaline Earth Cations
Authors: Harrowfield Jack M. , Richmond William R. , Skelton Brian W. , White Allan H. 
Published: January 2004

AbstractStructural studies of the dimethyl sulfoxide solvates of the perchlorates of Mg, Sr and Ba show the presence of a variety of complex ion species indicative of the forms possible in solution. While Mg(ClO4)2·6dmso contains the expected [Mg(dmso)6]2+ cation, the crystallised strontium species contains a mononuclear [Sr(dmso)6]2+ cation and two dinuclear species, the complex [(dmso‐O)5Sr(μ‐dmso‐O)3Sr(OH2)(dmso‐O)3]4+ containing both seven‐ and eight‐coordinate Sr metal centres, and [{(dmso‐O)5Sr(μ‐dmso‐O)}2]4+ containing seven‐coordinate Sr metal centres. The barium complex, of empirical formula Ba(ClO4)2·5dmso, contains a centrosymmetric dimer, [Ba2(dmso‐O)6(μ‐dmso‐O)4(O2ClO2)2]2+, involving an unsymmetrically chelating perchlorate and a nine‐coordinate Ba metal centre. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Palladium‐Catalyzed Regioselective Cyclotrimerization of Acetylenes in Supercritical Carbon Dioxide
Authors: Cheng Jin‐Sheng , Jiang Huan‐Feng 
Published: January 2004

AbstractThe cyclotrimerization process of different substituted alkynes occurred smoothly in supercritical carbon dioxide for the first time. The reactions are catalyzed by palladium chloride. High yields and regioselectivities were observed when 2 equiv. of CuCl2 and 5 mL of MeOH were added. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Cavitands at Work: From Molecular Recognition to Supramolecular Sensors
Authors: Pinalli Roberta , Suman Michele , Dalcanale Enrico 
Published: January 2004

AbstractExploitation of the molecular recognition properties of a given receptor in analytical applications requires mastering of specific host‐guest interactions at interfaces. This review outlines the issues involved in turning PV‐bridged cavitands into selective layers for mass sensors, as a case study for gas‐solid interfaces. The specific interactions operating at each phase level can be ferreted out by use of MS and crystallographic analyses, respectively. Their influence on sensor selectivity can be enhanced by exposure of the guest (analyte) to a network of cooperative interactions encoded in a single cavitand receptor. On the other hand, high layer permeability − necessary to achieve fast and reversible sensor responses − increases non‐specific dispersion interactions. Shifting of the balance towards selectivity without loss of reversibility represents the major challenge facing those wishing to venture into the field of supramolecular sensors. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Mechanism of Photoinduced Reactions between 1‐Acetylisatin and Aldehydes
Authors: Zhang Yan , Wang Lei , Zhu Ye , Xu Jian‐Hua 
Published: January 2004

AbstractHydrogen atom abstraction from aliphatic (2a, 2b) and aromatic (2c, 2d, 2e) aldehydes by the triplet nπ* state of 1‐acetylisatin (1) yielded triplet (isatin ketyl‐aldehyde acyl) radical pairs, which follow an out‐of‐cage pathway in subsequent reactions to give a series of radical coupling products 4−7. This out‐of‐cage mechanism is supported by examination of the primary products at various degrees of conversions during the course of the reaction, by the results of addition reactions of thermally generated isatin acyl radical with neutral 1, and by calculation of the charge density distribution in the acyl radicals and in ground state 1. Therefore, the oxygen‐philic attack of the acyl radical, which had escaped out of cage from the triplet radical pair, at the C(3) carbonyl oxygen atom of a ground state 1 selectively afforded the thermodynamically more stable addition radical B. The recombination of two radicals B gave the 3‐indolinone dimers 4 and 5 as diastereomers, while coupling of B with the isatin ketyl furnished the dihydroisoindigo derivative 6. Isatide 7 was also formed by ketyl radical recombination. The product ratio is dependent on the structure of the aldehyde. For 2d and 2e, each with an electron‐donating substituent in the benzene ring, the corresponding acyl radicals are less electrophilic because of a diminished positive charge density at the carbonyl carbon atom, and the formation of the addition radical B is a slow process relative to the encounter and recombination of the isatin ketyl radicals. As a result, products 6d and 6e from cross‐coupling of the isatin ketyl and radical B are formed in much lower yields than 6a, 6b, and 6c. The 3‐acetyloxy‐2‐indolinone 3 turned out to be a secondary product derived from the decomposition of 6 during the workup procedures. Since all the primary products are formed by out‐of‐cage radical pair combination processes, no chain mechanism is involved. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Diastereo‐ and Enantioselective Synthesis of Novel β‐Lactam‐Containing 1,4‐Benzodiazepines through a Ketene−Imine Cycloaddition Reaction
Authors: del Pozo Carlos , Macías Alberto , López‐Ortiz Fernando , Ángel Maestro Miguel , Alonso Eduardo , González Javier 
Published: January 2004

AbstractNovel tricyclic scaffolds that incorporate a β‐lactam ring fused to the d bond of a 1,4‐benzodiazepine seven‐membered ring have been synthesized in a process that constitutes one of the few examples of Staudinger‐type reactions involving ketimines described so far. In addition the creation of an asymmetric quaternary center has been achieved. The combination of these two “privileged structures” in a single compound is bound to confer interesting biological properties upon them. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Convenient Route to 2‐(Trialkylstannyl)cyclopropylamines and Their Application in Palladium‐Catalyzed Cross‐Coupling Reactions
Authors: Wiedemann Stefan , Rauch Karsten , Savchenko Andrei , Marek Ilan , de Meijere Armin 
Published: January 2004

AbstractThe 2‐(trialkylstannyl)‐N,N‐dialkylcyclopropylamines 3 were obtained by titanium‐mediated aminocyclopropanation of tributylvinylstannane with N,N‐dialkylformamides in yields of 80−84% and with excellent diastereoselectivities (trans/cis > 45:1). The resulting stannanes could advantageously be applied in Stille cross‐coupling reactions with aryl iodides, providing the pure trans‐2‐aryl‐(N,N‐dialkylamino)cyclopropanes 8 in yields ranging from 45 to 67% (six examples). The coupling of ethyl (E)‐3‐iodoacrylate (9) gave ethyl cis‐5‐(dibenzylamino)cyclopent‐2‐enecarboxylate (10) as a single diastereomer in 54% yield. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Coupling Reactions of 1,4‐Dicuprio‐1,3‐dienes: Formation of Carbocycles
Authors: Chen Chao , Xi Chanjuan , Lai Chunbo , Wang Ruji , Hong Xiaoyin 
Published: January 2004

AbstractThe coupling reaction of 1,4‐dicuprio‐1,3‐dienes in the presence of benzoquinone forms cyclobutadienes, which are easily transformed into cyclooctatetraene derivatives. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Synthesis and Some Properties of Aryl‐ and Aryloxy‐Substituted Phthalocyanines and Their Metal Complexes: A Comparison with Porphyrazine and Naphthalocyanine Analogues
Authors: Vagin Sergej , Hanack Michael 
Published: January 2004

AbstractThe preparation of new octakis[m‐(trifluoromethyl)phenyl]‐ and octakis[m‐(trifluoromethyl)phenoxy]phthalocyanines (6a and 6b) and their complexes with magnesium (5a, 5b) and indium (7a, 7b) is described. Their spectroscopic properties and solubilities are discussed in relation to those of metal‐free and metallated octakis[m‐(trifluoromethyl)phenyl]porphyrazine, as well as those of metal m‐(trifluoromethyl)phenyl‐ and m‐(trifluoromethyl)phenoxy‐substituted 2,3‐naphthalocyanines. A drastic decrease in the solubilities of the metal‐free phthalocyanines in CH2Cl2 was observed on comparing them with m‐CF3‐phenyl‐substituted porphyrazine. However, their solubilities in THF were high enough for NMR spectra to be recorded. Insertion of (chloro)indium into the cavities of these phthalocyanines noticeably enhances the solubilization of the macrocycles, including in CH2Cl2. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Immunomodulatory α‐Galactoglycosphingolipids: Synthesis of a 2′‐O‐Methyl‐α‐Gal‐GSL and Evaluation of Its Immunostimulating Capacity
Authors: Barbieri Lucia , Costantino Valeria , Fattorusso Ernesto , Mangoni Alfonso , Aru Elisabetta , Parapini Silvia , Taramelli Donatella 
Published: January 2004

AbstractThe total synthesis of 1‐2‐docosanoylamino‐O‐(2‐O‐methyl‐α‐D‐galactopyranosyl)‐1,3,4‐octadecanetriol (2), a 2′‐methoxy analog of the immunostimulating α‐galactoglycosphingolipid 1, is reported. Stereoselective α‐glycosylation of the azido precursor of sphingosine was successfully performed for the first time using an improved Mukaiyama reaction. When assayed in a 72 h splenocyte proliferation test, compound 2 was significantly less stimulatory than the non‐methylated compound 1, suggesting that the galactose 2‐OH group is essential for the immunostimulatory activity of α‐Gal‐GSLs. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Phosphane‐Catalyzed Knoevenagel Condensation: A Facile Synthesis of α‐Cyanoacrylates and α‐Cyanoacrylonitriles
Authors: Yadav Jhillu S. , Reddy Basi V. Subba , Basak Ashok K. , Visali Boddapati , Narsaiah Akkirala Venkat , Nagaiah Kommu 
Published: January 2004

AbstractTriphenylphosphane (TPP) has been utilized as a novel and efficient catalyst for the Knoevenagel condensation of aldehydes with acidic methylene compounds such as ethyl cyanoacetate and malononitrile to afford substituted olefins. The reaction proceeds smoothly under mild and solvent‐free conditions and the products are obtained in excellent yields with an E‐geometry. This method is applicable for a wide range of aldehydes including aromatic, aliphatic and heterocyclic substrates. Microwave irradiation has been used to achieve enhanced reaction rates and improved yields. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Chemical Resolution of 1,2‐O‐Cyclohexylidene‐3,4‐O‐(tetraisopropyldisiloxane‐1,3‐diyl)‐myo‐inositol and Synthesis of Phosphatidyl‐D‐myo‐inositol 3,5‐Bisphosphate from Both L‐ and D‐Enantiomers
Authors: Han Fushe , Hayashi Minoru , Watanabe Yutaka 
Published: January 2004

AbstractChemical resolution of a versatile starting material, 1,2‐Ocyclohexylidene‐3,4‐O‐(tetraisopropyldisiloxane‐1,3‐diyl)myo‐inositol, which is used to access naturally occurring inositol phosphates and phosphatidylinositol phosphates, is described. Starting from both D‐ and L‐enantiomers of the material, the synthesis of phosphatidyl‐D‐myo‐inositol 3,5‐bisphosphate [PtdIns(3,5)P2] has been conveniently accomplished via convergent routes. One of the key reactions in the synthetic procedure was the regioselective phosphorylation of suitably protected 1,2,4‐triol derivatives of inositol. Phosphorylation of the triol attempted in a 1:12 (v/v) pyridine/CH2Cl2 mixture did not proceed at all, whereas in an optimized solvent system, pyridine/CH2Cl2 (1.1:1, v/v), the reaction afforded 68% of the desired 1‐O‐phosphate as a single product. Further investigation by 1H NMR spectroscopy indicated that the reactivity of the three OHs on 1,2,4‐triol derivatives is governed by intermolecular hydrogen bonding, which may be disrupted by an increase in the proportion of pyridine in the reaction solvent. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Synthesis Routes Towards the Farnesyl Protein Transferase Inhibitor ZARNESTRATM
Authors: Angibaud Patrick R. , Venet Marc G. , Filliers Walter , Broeckx Rudy , Ligny Yannick A. , Muller Philippe , Poncelet Virginie S. , End Dave W. 
Published: January 2004

AbstractThe discovery that post‐translational farnesylation of Ras oncoprotein was an essential step in exercising its biological effect led to the design of farnesyl protein transferase inhibitors (FTIs) in order to control growth of tumors bearing Ras mutations. Pre‐clinical studies on murine models have confirmed their inhibitory effect on tumor growth and enabled clinical development. R115777 (ZARNESTRATM) is currently undergoing clinical evaluation and recent studies have confirmed its antitumor potential and low toxicity. We wish to describe here the chemical synthesis routes that our group have developed to access ZARNESTRATM. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Calix[4]arene‐Supported N‐Heterocyclic Carbene Ligands as Catalysts for Suzuki Cross‐Coupling Reactions of Chlorotoluene
Authors: Frank Markus , Maas Gerhard , Schatz Jürgen 
Published: January 2004

AbstractStable N‐heterocyclic carbenes are generated starting from 5,17‐(bis‐imidazolium)‐substituted calix[4]arenes. Addition of Pd(OAc)2 to these carbenes leads to macrocyclic cis‐palladium chelate complexes in which the distal bridging of the upper rim leads to a strong distortion of the calix[4]arene skeleton which was proven by X‐ray crystal structure determination. Using an in‐situ catalytic system consisting of a calixarene‐imidazolium salt, Cs2CO3 as a base and a source of palladium, a species is formed which can be used to catalyse the Suzuki cross‐coupling of 4‐chloro toluene. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Highly Stereoselective Conversion of Aryl Peptidyl Ketones into the Corresponding Peptide Alcohols
Authors: Di Gioia Maria Luisa , Leggio Antonella , Le Pera Adolfo , Liguori Angelo , Siciliano Carlo 
Published: January 2004

AbstractIn this paper we describe the conversion of aryl peptidyl ketones, by a hydride reduction, into the corresponding peptide alcohols. The developed methodology is highly stereoselective and represents a very important application in peptide chemistry for obtaining peptide alcohols. It provides peptide alcohols with definite stereochemistry and in moderate, but satisfactory, yields. The reducing procedure, performed with NaBH3CN and TiCl4, probably proceeds via two diastereomeric cyclic intermediates that show different reactivity. The stereochemistry of the resulting alcohols was established after obtaining them by an alternative synthetic procedure. Furthermore, the methodology adopted keeps the urethane protecting group on the amino function of the N‐terminal amino acid residue. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Synthesis of 1‐(Alkoxycarbonyl)methylene‐1,3‐dihydroisobenzofurans and 4‐(Alkoxycarbonyl)benzo[c]pyrans by Palladium‐Catalysed Oxidative Carbonylation of 2‐Alkynylbenzyl Alcohols, 2‐Alkynylbenzaldehydes and 2‐Alkynylphenyl Ketones
Authors: Bacchi Alessia , Costa Mirco , Della Cà Nicola , Fabbricatore Marcella , Fazio Alessia , Gabriele Bartolo , Nasi Cristina , Salerno Giuseppe 
Published: January 2004

AbstractA direct synthesis of 1‐(alkoxycarbonyl)methylene‐1,3‐dihydroisobenzofurans 2 and 5 and 4‐(alkoxycarbonyl)benzo[c]pyrans 3 and 6 by oxidative Pd‐catalysed cyclization/alkoxycarbonylation of 2‐alkynylbenzyl alcohols 1, and of 2‐alkynylbenzaldehydes or 2‐alkynylphenyl ketones 4 is reported. Reactions were carried out in ROH or CH3CN/ROH (R = Me, iPr) as the solvent at 70−105 °C in the presence of catalytic amounts of PdI2 in conjunction with KI under a 4:1 or 3:1 CO/air mixture (2.0 or 3.2 MPa total pressure at 25 °C). The reaction occurs through intramolecular attack by the nucleophilic oxygen atom (either already present in the starting material, as in 1, or generated in situ by ROH attack on carbonyl group, as in 4) on the triple bond coordinated to PdII, followed by alkoxycarbonylation. The presence of substituents at the alkyne terminal position and at the carbon atom α to the hydroxy group play a key role in the selectivity of the process towards the formation of a five‐ or six‐membered ring. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
The Regiochemistry of the Addition of PhSeCl to Arylferrocenylethynes: A Cooperative Effect?
Authors: Brunetti Tiziana , Diddoro Massimo , Di Vona Maria Luisa , Floris Barbara , Galloni Pierluca , Licoccia Silvia 
Published: January 2004

AbstractPhSeCl adds to arylferrocenylethynes giving two regioisomers, ArC(Cl)=C(SePh)Fc and ArC(SePh)=C(Cl)Fc in different amounts, due to a favourable Se−Fe interaction.77Se NMR spectroscopy was useful for identifying the addition products.Kinetic experiments were also performed and a correlation was found using Hammett σ values. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Cover Picture: Cavitands at Work: From Molecular Recognition to Supramolecular Sensors (Eur. J. Org. Chem. 3/2004)
Authors: Pinalli Roberta , Suman Michele , Dalcanale Enrico 
Published: January 2004

AbstractThe cover picture shows the operating principle of a supramolecular mass sensor. The cavitand receptor is coated on the surface of a quartz crystal microbalance (QCM) and exposed to a flux of the analyte (methanol) in the gas phase (center). All complexation events occurring at the gas/solid interface are collectively recorded by the transducer as a frequency drop (bottom). The molecular interactions responsible for the selective alcohol detection are evidenced in the crystal structure of the complex (top). The Microreview by R. Pinalli, M. Suman and E. Dalcanale covers the issues involved in turning a synthetic receptor into an effective supramolecular gas sensor, namely design and preparation of the receptor as function of the analytes to be detected, evaluation of the complexation properties of the receptor in the solid state and in the gas phase, sensor reversibility and selectivity as function of layer permeability, on p. 451 ff.
Calibrationless quantitative analysis by indirect UV absorbance detection in capillary zone electrophoresis: The concept of the conversion factor
Authors: Beckers Jozef L. , Boček Petr 
Published: January 2004

AbstractA new, fast and efficient procedure is described for the simultaneous quantitative analysis of various non‐UV absorbing species in a sample, by capillary zone electrophoresis with indirect UV absorbance detection. The procedure is based on the concept of the conversion factor (CF). The CF of an analyte is defined as the ratio of the measured temporal peak area and the product of its migration time and transfer ratio (TR). Thus defined, the CF is of general validity for all analytes separated and detected in a given background electrolyte (BGE), since it has the same value for the same amounts of various analytes. If a sample is enriched with a known concentration of a standard component and analyzed by CZE, the CF of this standard component can be calculated and then the concentrations of all other analytes can be determined, without the use of any calibration graph. The individual TRs can be determined a priori from tabulated ionic mobilities and pK values of the analytes and of the constituents of the BGE or, for strong analytes, by using experimental data from the electropherogram of the analysis itself. The practical procedure of the analysis includes enrichment of the sample with a known quantity of a suitable standard and a single CZE run of the resulting mixture. The injected volume does not need to be known and thus the procedure also eliminates the injection error. The proposed procedure has been verified experimentally and reproducible and accurate values were obtained by using four different CZE apparatus for the analyses of standard mixtures of cations in three different BGEs.