bluuebunny/crossref_metadata_2025_split huggingface dataset:
Asymmetric Synthesis of Isoquinoline Alkaloids: (R)‐ and (S)‐2‐Ethoxycarbonyl‐1‐Formyl‐6, 7‐Dimethoxy‐1,2,3,4‐Tetrahydroisoquinoline as Versatile Precursors
Authors: Czarnocki Zbigniew , Maclean David B. , Szarek Walter A. 
Published: September 2010

AbstractA method is described for the preparation of (R)‐ and (S)‐2‐ethoxycarbonyl‐1‐formyl‐6,7‐dimethoxy‐1,2,3,4‐tetrahydroisoquinoline involving a Swerntype oxidation of (R)‐ and (S)‐2‐ethoxycarbonyl‐1‐hydroxymethyl‐6, 7‐dimethoxy‐1,2,3,4‐tetrahydroisoquinoline {(R)‐ and (S)‐2‐(ethoxycarbonyl)calycotomine}. The utility of these aldehydes in asymmetric synthesis of isoquinoline alkaloids has been demonstrated by their conversion into (S)‐ and (R)‐xylopinine, respectively; also, the (R)‐aldehyde has been employed for the synthesis of (8S,14S)‐coralydine.
Formation of Pyrazoles and of Imidazoles from Phenacyl Ketal Hydrazones of Aldehydes
Authors: Scarpetti† David , Kano†† Kunio , Anselme Jean‐Pierre 
Published: September 2010

AbstractThe cyclization of phenacyl ethylene ketal (pek) hydrazones of glyoxals, benzaldehyde and acetaldehyde to the pyrazoles is described; in the case of the hydrazones of benzaldehyde and acetaldehyde, the corresponding imidazoles are also formed. A mechanism is suggested for the formation of the imidazoles.
Infrared study of the Proton Acceptor Ability of Nicotine
Authors: De Taeye J. , Zeegers‐Huyskens Th. 
Published: September 2010

AbstractThe interaction between nicotine and phenol derivatives has been studied by infrared spectrometry in solvents of low polarity. The enthalpies of complex formation ranged from 24 to 36 kJmol−1 and the ΔvOH values from 440 to 580 cm−1, indicating a rather strong interaction. The FT‐Infrared spectra (1100‐600 cm−1) strongly suggest that the interaction occurs at the N atom of the pyridine ring showing that hydrogen bond formation is governed by the accessibility of the lone pair of the base.
Spectroscopic Study of the PD(II) Complexes with 2 Amino‐4,6 Dimethylpyrimidine
Authors: Kovala‐Demertzi D. , Tsangaris J. M. , Desseyn H. O. , van Der Veken B. J. 
Published: September 2010

AbstractComplexes of Pd(II) with 2 amino‐4,6 dimethylpyrimidine have been studied employing elemental analysis, thermal analysis, U. V.‐Vis, infrared and Raman techniques. The complexes have been isolated at PdL2Cl2(A). Pd2L3Cl4(B). PdCl2.3H2O(C) and Pd2L2Br3.3H2O(D). The metal is bound to the ligand through the nitrogen atom of the pyrimidine ring system while the amino group is not involved in the complex formation.
Deoxygenation, Deaeration and Degassing: A Survey and Evaluation of Methods
Authors: Luyckx Geert , Ceulemans Jan 
Published: September 2010

AbstractTechniques for the removal of dissolved gases from liquids are reviewed and classified according to their working principles. Consideration of these working principles reveals some inherent limitations of certain techniques and it may be concluded that the different methods complement each other in a number of aspects. Proton spin‐lattice relaxation time measurements and polarographic analyses are used for evaluation of different deoxygenation methods. It is concluded that for most purposes the different methods yield satisfactory results if applied properly and within the inherent limitations of the techniques. When the presence of oxygen is very critical and its concentration must be reduced to very small amounts, a combination of methods appears advisable.
Pyrolyse‐Éclair Sous Vide de 1,2,4‐Triazolides = Une Étude par Spectrométrie de Masse en Tandem
Authors: Maquestiau A. , Puk E. , Flammang R. 
Published: September 2010

AbstractA real‐time analysis of the flash‐vacuum pyrolysis products of some 1,2,4‐triazolides has been performed by tandem mass spectrometry. Beside decay products, ketenes and the parent 1,2,4‐triazole, 1‐acyltriazoles give rise to 5‐alkyloxazoles and nitrogen. This ring transformation reaction implies a sigmatropic shift of the acyl group from nitrogen to carbon, loss of nitrogen and cyclisation of the biradical intermediate. 5‐aryloxazoles are similarly obtained from 1‐aroyltriazoles.
Synthèse des Benzimidazolyl‐2 Méthyl‐5′ Pyrazolyl‐3′ Méthanes a Partir des Acétylméthylène‐4 Benzodiazepine‐1,5 Ones‐2
Authors: Essassi E. M. , Elabbassi M. , Fifani J. 
Published: September 2010

AbstractHydrazionolysis of 4‐acetylmethylene‐1,5‐benzodiazepin‐2‐ones 1, 2 gives, depending on the experimental conditions, either N‐(2‐aminophenyl) 5′‐methyl‐3′‐pyrazolyl acetamides 3‐4 or 2‐benzimidazolyl‐5′‐methyl‐3′‐pyrazolylmethanes 5‐6.
I‐Isocyanoaromadendrane, A New Isonitrile Sesquiterpene from the Sponge Acanthella Acuta
Authors: Braekman J. C. , Daloze D. , Deneubourg F. , Huysecom J. , Vandevyver G. 
Published: September 2010

AbstractTwo isonitrile sesquiterpenes 2 and 3 have been isolated from the toxic dichloromethane extract of the marine sponge Acanthella acuta. Compound 2 was found to be identical with axisonitrile‐3. compound 3, 1‐isocyanoaromadendrane, is a novel sesquiterpene whose structure has been determined on the basis of its spectral properties and by chemical correlation with palustrol.
Mechanism of the Catalytic Reduction of Hydroperoxides by Ebselen : A Selenium ‐ 77 Nmr Study
Authors: Fischer Hartmut , Dereu Norbert 
Published: September 2010

AbstractEbselen (2‐phenyl‐1,2‐benzisoselenazol‐3(2H)‐one 1, a non‐toxic selenium containing heterocyclic compound has been shown to display both anti‐ inflammatory activity in vivo and GSH‐Px‐like activity in vitro. Using 1H and 77Se NMR we investigated the mechanism of reduction of hydroperoxides by thiols in the presence of 1. A catalytic cycle depending on the formation of diselenides and selenenylsulfides was found. The selenenic acid oxidation level present in compound 1 is particularly stable because of the intramolecular cyclisation. This contrasts with previously reported results concerning the oxidation of organoselenium compounds.
Comparative Hydrodesulfurization of Athabasca Oil Sands Coker Gas Oil Over Ni‐Mo and Co‐Mo Catalysts
Authors: George Zacharia Mathew , Mohammed Peter 
Published: September 2010

AbstractThe hydrodesulfurization of Athabasca oil sands coker gas oil has been compared over Ni‐Mo and Co‐Mo catalysts on the basis of rate constants at 400°C, 10.3 MPa (H2) and at an LHSV of 12.0 h−1. Both catalysts were cylindrical extrudates of 3.5 mm × 1.6 mm. A Berty Continuous Stirred Tank Reactor (CSTR) was used for the hydroprocessing. Although the Ni‐Mo catalyst had higher activity per gram of catalyst, on the basis of the rate constant per gram of molybdenum, the Co‐Mo catalyst was slightly more active with lower activation energy than the Ni‐Mo catalyst for HDS.
NMR studies on imidines. VII. The tautomerism of mono‐n‐aryl substituted phthalic imidines. A 1H and 13C nuclear magnetic resonance study
Authors: Spiessens Luc I. , Anteunis M. J. O. 
Published: September 2010

Abstract1H and 13C NMR data indicate the presence of N‐aryl substituted phthalic imidines to exist as 3‐amino‐1‐N‐arylimino‐1H‐isoindole compounds in DMSO‐d6. In CDCl3 a tautomeric equilibrium mixture containing 20% of the imino form is observed. The presence of a dimeric association through intramolecular H bonds is suggested.It is shown that intramolecular NH‐N hydrogen bonds displace the tautomeric equilibrium toward the imino tautomer in 2‐pyridyl substituted phthalic imidines. In the reaction product of phthalic imidine and 2, 6‐diaminopyridine, 11, two pairs of intramolecular NH‐N hydrogen bonds result in the presence of both amino and imino tautomeric forms in the same molecular species.
Azadiene derivatives as synthetic intermediates
Authors: Barluenga José 
Published: September 2010

AbstractThe applicability of 4‐amino‐1‐azabutadienes 1 in synthesis of five‐, six‐, and eight‐membered ring heterocycles is demonstrated; several open‐chain compounds have also been diastereo‐ or enantio‐selectively prepared. The synthesis and reactivity of both neutral and electron‐poor 2‐azabutadienes 2 is presented; these heterodienes rapidly react, in a (4+2)‐fashion, with several dienophiles to form the corresponding cycloadducts. The synthesis of the 2‐aminosubstituted 1,3‐butadienes 3 and their ability to act as dienes in Diels‐Alder reactions has also been explored; the behaviour of 3 as enamine is shown, as well.
L'Évaluation Semi‐Empirique des Densités de Spin π dans les Radicaux Carbones
Authors: Leroy Georges , Peeters D. , Sana M. , Wilante C. 
Published: September 2010

AbstractA critical analysis of the well known McConnell relations a = Qρ π s(Cα) leads us to propose a new value for the parameter Qβ and an additive rule to calculate the πspin densities, ρ πs(Cα). Other values of substituent parameters ΔXi are also proposed. The difference between a(Hβ)/Qβ and the π spin densities calculated by use of the additive relation is generally negative, in captodative‐substituted ethyl radicals. Furtheron, it is found that the observed values of ρπs(Cα) are pretty well correlated to the corresponding thermodynamic stabilization energies, in the case of cd‐substituted radicals.
Molecular structure in the solid state (X‐Ray diffraction) and in solution (1H and 13C NMR) of nifurtimox and two pyrazol‐1‐Yl analogs
Authors: de la Concepción Foces‐Foces Ma , Cano Félix Hernández , Claramunt Rosa Ma , Fruchier Alain , Elguero José 
Published: September 2010

AbstractThe crystal and molecular structure of tetrahydro‐3‐methyl‐4[(5‐nitrofurfurylidene)amino]‐2H‐thiazine 1, 1‐dioxide (Nifurtimox) 1, 1‐[(5‐nitrofurfurylidene)amino]pyrazole 2, and 1‐[(5‐nitrothenylidene)amino] pyrazole 3 have been solved by X‐Ray crystallography. Compound 1 presents the E‐sE conformation along the N = C‐C moiety while 2 and 3 presents an E‐sZ one. In spite of their molecular similarity (sulfur instead of oxygen in the ring), compounds 2 and 3 pack in quite different ways. In solution (1H and 13C NMR) the only difference with the solid structures concerns the ∼ 180° rotation of the furane ring in compound 1 which thus becomes similar to the other two compounds (sZ). A detailed analysis of the seven proton system of the 1,4‐thiazine 1,1‐dioxide ring established that in solution too, the ring has a chair conformation with the C‐methyl group in an equatorial position.
Determination of the Kinetics of SO2 Absorption Using Thermogravimetry
Authors: Duisterwinkel A. E. , Hakvoort G. 
Published: September 2010

AbstractA shrinking core model is proposed for the absorption of SO2 in a sorbent consisting of CaO on γ‐Al2O3, which is made by a sol‐gel method. The model assumes that pore diffusion and bulk gas transfer limit the absorption rate. Tests with a thermobalance, equipped with a special sampleholder to minimize external diffusion limitation, show that this model is very likely correct. In the thermobalance external diffusion limitation is important up to a conversion of approx. 40%. The mean effective pore diffusion coefficient is 5.3±0.5 10−7 m2/s. Relating this value to the Knudsen diffusion coefficient gives very realistic values for the tortuosity factor.
Structure d'une flamme pauvre hydrogène‐oxygène ensemencée ou non par le trifluorométhane
Authors: Richter H. , Vandooren J. , van Tiggelen P. J. 
Published: September 2010

AbstractThe structure of two premixed lean H2/O2/Ar flames, one uninhibited and the other inhibited by 3% of CF3H has been established at 4.6 kPa by using a mass spectrometric analyzer coupled with molecular beam sampling. The main effect of the CF3H addition concerns the formation of lower quantities of H atoms and the shift of the H, O, OH, H2O and temperature profiles in the inhibited flame. HF, CF2O and CO2 are products of the CF3H combustion. They remain in the burnt gases. CO is only an intermediate, which is formed essentially from CF3 species without going through CF2O as an intermediate.
Fluorinated Heterocycles: Targets in the Search for Bioactive Compounds and Tools for their Preparation
Authors: Differding E. , Frick W. , Lang R. W. , Martin P. , Schmit C. , Veenstra S. , Greuter H. 
Published: September 2010

AbstractTwo strategies for the preparation and use of fluorinated heterocycles are discussed:* thebuilding block approachbeing used mainly for the preparation oftargetheterocycles with fluorinated substituents, and* thedirect fluorination approachin which fluorinated heterocycles are used astoolsfor the preparation of bioactive compounds.Strategies presented in thebuilding block approachinclude electrophilic reactions of building blocks derived from trifluoroacetic acid (1), as well as the use of building blocks obtained from trichlotrifluoroethane (2) and chlorodifluoro acetic acid (3) through organometallic reactions. The preparation und use of N‐fluoro sultams62and66are shown in thedirect fluorination approach. Both strategies can be successfully used in the synthesis of bioactive compounds of pharmaceutical and agrochemical interest.
Synthesis and Reactions of 2H‐Benzimidazole‐2‐Spirocyclohexanes: An Application of ”Umpolung“
Authors: Iddon Brian 
Published: September 2010

AbstractThe title compounds are available through condensation of an o‐phenylenediamine with cyclohexanone followed by oxidation of the resulting product with manganese dioxide. In this article we review their oxidation, reduction, and rearrangement reactions along with their reactions with nitrogen, oxygen, sulphur, and other nucleophiles. As well as the parent compound the reactions of the 5‐chloro‐, 5,6‐dichloro‐, 4,6‐dibromo‐, 5‐phenylsulphonyl‐ and 5‐methoxy‐derivative are discussed in some detail. Some applications of the methodology developed, particularly to the synthesis of actual or potential benzimidazole anthelminthics, are given also.
Ring‐Transformation Graphs in Heterocyclic Chemistry
Authors: Babaev Eugeny V. , Zefirov Nikolai S. 
Published: September 2010

AbstractA novel graph‐theoretical and topological approach is suggested for the description and classification of a great number of simple ring‐transformation reactions of heterocycles. The suggested ring‐bond‐redistribution graphs (which can be easily obtained from the known mechanisms of rearrangements or recyclizations) visualize the degree of similarity of different ring transformations. A simple type of structure of these labelled graphs and the clear chemical sense of the used labels permit us to classify a lot of known simple heterocyclic ring transformations in an hierarchic system, which can be used to predict unknown types, classes and sorts of these reactions.
Syntheses Et Caracterisation Des Derives Methyles Du Tetrathiafulvalene; Nouvelle Voie D'Acces Au Tetrathiafulvalene
Authors: Mora Henri , Fabre Jean‐Marc , Giral Louis , Montginoul Claude 
Published: September 2010

AbstractWe propose an improved general method for the synthesis of tetrathiafulvalene and its methylated derivatives. TTF is obtained in a five steps preparation offering a high Overall yield.Concerning the unsymmetrically methylated tetrathiafulvalenes, four different procedures are analysed. It is shown the best routes to prepare trimethyltetrathiafulvalene are a WITTIG type reaction, and a selective synthesis based on a WITTIG‐HORNER reaction. The monomethyltetrathiafulvalene has been isolated in a 96% state of purity.
Modelling of Photochromic Spiropyrans and Spirooxazines by Molecular Mechanics and Comparison with Experimental Data
Authors: Pottier E. , Samat A. , Guglielmetti R. , Siri D. , Pèpe G. 
Published: September 2010

AbstractWith the help of molecular mechanics (program GenMol), suitable molecular geometries were obtained for photochromic spiropyrans and spirooxazines to evaluate substituent effects on the spectroscopic and physicochemical properties. The results were compared to X‐ray structures and used to explain relevant 1H NMR data.
Synthesis of Hydrazone Derivatives From 1,2:5,6‐Di‐O‐Isopropylidene‐α‐D‐Ribo‐Hexofuranos‐3‐Ulose
Authors: De Wit D. , Qing Cui Yi , van Rantwijk F. , Maat L. , Kieboom A. P. G. 
Published: September 2010

AbstractProtected D‐ribo‐hexos‐3‐ulose, 1,2:5,6‐di‐O‐isopropylidene‐α‐D‐glucofuranos‐3‐ulose, is converted into the corresponding hydrazone derivatives by reaction with hydrazine, methyl‐, phenyl, and tert‐butylhydrazine. Two isomeric (Z and E) hydrazono‐carbohydrates were obtained. The structures of these isomers were established by 1H and 13C NMR as well as by single‐crystal X‐ray analysis.
Influence of the Degree of Ion Exchange on the Sorption Properties of Coked Zeolite Y
Authors: Rozwadowski M. , Włoch J. , Erdmann K. , Kornatowski J. 
Published: September 2010

AbstractThe influence of the degree of exchange of Na+ for H+ in zeolite Y on both the structure of coke deposits formed during the conversion of methanol and on the sorption properties of the coked material was studied. It was found that the amount of the deposits depended on the degree of ion exchange only to a small extent. The determined water‐vapor adsorption isotherms could be described by the Dubinin‐Astakhov (DA) equation. The parameters of the DA equation varied with the level of ion exchange of the zeolite and with the content of coke.
Oxidation of Hydrazines with Carbon Tetrachloride
Authors: Sun† Han‐Li , McNamara Bruce , Anselme J.‐P. 
Published: September 2010

AbstractSome hydrazines, especially 1,2‐dialkylhydrazines are oxidized to the corresponding diazenes (azo compounds) by carbon tetrachloride presumably via nucleophilic attack by nitrogen on chlorine. Monacylhydrazines are converted to the corresponding diacylhydrazines.
Synthèse de β‐Aminoacides Pontes Et Leur Thermolyse En Déhydro β‐Aminoacide Et En Oxauracile
Authors: Akssira M. , Dahdouh A. , Kasmi H. 
Published: September 2010

AbstractReactions of bridged dicarboxylic anhydride derivatives with sodium azide in THF give the corresponding, N‐tert‐butyloxycarbonyl β‐aminoesters 2(a‐c), which can be cyclized to oxanorborno‐ and norbornouracils 6(a‐c). Pyrolysis of these adducts leads to dehydro‐β‐alanine 5 and oxauracil 7.
Synthesis and Acid‐Base Properties of a Pyridine Containing Macrocycle with Nitrogen And Sulfur as Donor Atoms
Authors: Steenland Mathieu W. A. , Lippens Werner , Herman Gerrit G. , Goeminne André M. 
Published: September 2010

AbstractThe macrocyclic Schiff base has been prepared by a [2+2] condensation with and in absence of a metal ion as template. A subsequent reduction with NaBH, yielded the polyamine of which the acid‐base properties in water were investigated.
The Prototropic Structural Transformations of Pyridoxal‐Benzoylhydrazone and Other Synthetic Chelating Ligands
Authors: Fakhrayan Hussein , Doucet Jean‐Pierre , El Hage Chahine Jean‐Michel 
Published: September 2010

AbstractThis paper deals with the pH‐dependent structural distributions of three synthetic chelating ligands of pharmacological interest for the treatment of iron overload, PBH, SIH and SBH. PBH can be isolated in aqueous media as four prototropic species: H3L+ at pH < 3, H2L at 6 < pH < 7, HL− in the vicinity of pH 10 and L2‐ at pH > 12. SIH can also be isolated as four species: H3L+ at pH < 2, H2L at 5 < pH < 7, HL− in the vicinity of pH 10 and L2‐ at pH > 12. Finally, SBH only exists as three species: H2L at pH < 4, HL− in the vicinity of pH 8 and L2‐ at pH > 11. These results indicate that the affinity of PBH and SIH for iron would not be affected by the acidity of the endosomes where complex formation occurs in natural media. However, in these conditions of acidity the affinity of SBH for iron will probably be decreased by ligand protonation.
Action des O‐Phénylènediamines Sur La 2,6‐Diméthyl Pyr‐4‐One Et La 1,3‐Diacétylacétone
Authors: Djerrari B. , Essassi E. M. , Fifani J. 
Published: September 2010

AbstractCondensation of o‐phenylenediamines with 2,6‐dimethylpyr‐4‐ones gave 2‐methyl benzimidazoles and 1‐(o‐aminophenyl)‐2,6‐dimethyl pyrid‐4‐ones. These laters compounds and 2‐acetonylidene‐4‐methyl‐1,5‐benzodiazepines are obtained when o‐phenylenediamines are reacted with 1,3‐diacetylacetone.
Evidence of Native Metal–S2−–Metallothionein Complexes Confirmed by the Analysis of Cup1 Divalent‐Metal‐Ion Binding Properties
Authors: Orihuela Rubén , Monteiro Freddy , Pagani Ayelén , Capdevila Mercè , Atrian Sílvia 
Published: September 2010

AbstractIt has previously been shown that recombinant synthesis, under metal‐supplemented conditions, of diverse metallothioneins (MTs) results in the recovery of a subpopulation of S2−‐containing complexes in addition to the S2−‐devoid canonical metal–MT species. Further significance of this finding has remained veiled by the possibility of it being a mere consequence of synthesis in a heterologous bacterial system. Herein, we present definitive evidence that S2− ligands are also constituents of native metal–MT complexes. Because, although practically universal, the highest S2− content is incorporated by copper‐thioneins when coordinating divalent metal ions, we adapted the Saccharomyces cerevisiae Cup1 protein, which is the most paradigmatic copper‐thionein, as an experimental model. Most significantly, native Cd–Cup1 complexes were purified and fully spectroscopically and spectrometrically characterized from the 301N mutant yeast strain, which allows Cup1 synthesis even in the absence of copper. These results undoubtedly revealed the presence of a Cd–S2−–Cup1 species in native preparations, which were only recovered when carefully avoiding the use of ion‐exchange chromatography in the purification protocol. Furthermore, complete analysis of recombinant (Escherichia coli) Zn–Cup1, Cd–Cup1, and Cu–Cup1 and those complexes that result from Zn/Cd and Zn/Cu replacements in vitro and acidification/renaturalization processes yielded a comprehensive and comparative overview of the metal‐binding abilities of Cup1. Overall, we consider the main conclusions of this study to go beyond the mere study of the particular Cup1 MT, so that they should be considered to delineate a new point of view on the interaction between copper‐thioneins and divalent metal ions, still an unexplored aspect in MT research.
Electrophilic Reactivities of Azodicarboxylates
Authors: Kanzian Tanja , Mayr Herbert 
Published: September 2010

AbstractThe kinetics of the reactions of the azodicarboxylates 1 with the enamines 2 have been studied in CH3CN at 20 °C. The reactions follow a second‐order rate law and can be described by the linear free energy relationship log k2(20 °C)=s(N+E) (E=electrophilicity parameter, N=nucleophilicity parameter, and s=nucleophile‐specific slope parameter). With E parameters from −12.2 to −8.9, the electrophilic reactivities of 1 turned out to be comparable to those of α,β‐unsaturated iminium ions, amino‐substituted benzhydrylium ions, and ordinary Michael acceptors. While the E parameters of the azodicarboxylates 1 determined in this work also hold for their reactions with triarylphosphines, they cannot be used for estimating rate constants for their reactions with amines. Comparison of experimental and calculated rate constants for cycloadditions and ene reactions of azodicarboxylates provides information on the concertedness of these reactions.
ChemInform Abstract: Group VI Trimers (Se3, Te3, and Po3). Electronic States and Potential Energy Surfaces
Authors: BALASUBRAMANIAN K. , DAI D. 
Published: September 2010

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: Linear and Nonlinear Optical Properties of TeO2 Glass.
Authors: KIM S.‐H. , YOKO T. , SAKKA S. 
Published: September 2010

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.