bluuebunny/crossref_metadata_2025_split huggingface dataset:
Syntheses of Chiral C=N Dienophiles: Sulfonyloxyimino‐Malononitrile and Alkyl Sulfonyloxyiminocyanoacetates
Authors: Blanco José M. , Caamaño Olga , Eirin Ana , Fernandez Franco , Medina Lucía 
Published: September 2010

AbstractHigh yield syntheses of one chiral sulfonyloxyiminomalononitrile and four alkyl sulfonyloxyiminocyanoacetate derivatives (3a‐e), to be used in asymmetric hetero‐Diels‐Alder additions, are described.
Synthesis of 2′‐Chloro‐2′,3′‐Dideoxy‐2′,3′‐Didehydro Nucleosides
Authors: van Aerschot A. , Herdewijn P. 
Published: September 2010

AbstractTreatment of O2,2′‐anhydrouridine with triphenylmethyl chloride in pyridine at 80°C gives mainly the 2′‐chlorinated nucleoside 3. Reaction of 2′‐chloro‐3′‐0‐trifluoromethane‐sulfonyl‐5′‐0‐trityl‐2′‐deoxyuridine (4) with NaOH led exclusively to the elimination product 5, opening the way to 2‐chloro substituted glycero‐pent‐2‐enofuranosyl nucleosides.
2,3′‐Difluoro‐and 3′‐Azido‐2′‐Fluoro Substituted Dideoxypyrimidines as Potential Anti‐HIV Agents
Authors: van Aerschot A. , Herdewijn P. 
Published: September 2010

Abstract2′‐Deoxy‐2′‐fluorouridine (2) was obtained by reaction of the arabinofuranosyl nucleoside 1 with diethylaminosulfur trifluoride followed by detritylation. After inversion of the configuration at the 3′‐position, 4 was used as starting material for the preparation of the 2′,3′‐disubstituted derivatives 6, 7, 8 and 10.
Réactivité des β‐enaminoesters cycliques derives de la quinoxaline
Authors: Essassi El Mokhtar , Ferfra Souad , Salem Moussa , Zniber Rachid 
Published: September 2010

AbstractAction of alkylant agent in phase transfer catalysis conditions on 3‐ (ethoxy carbonyl methylene)2‐oxo quinoxalines have been studied. Reaction of bromination following by nucleophile substitution reaction in presence of potassium cyanure, sodium azoture and sodium nitrite have been examinated.
Spectrométrie de masse de triazolides et de leurs produits de transformation par pyrolyse‐éclair sous vide
Authors: Maquestiau André , Abdelouahab Fouad Bachir Ben , Flammang Robert 
Published: September 2010

AbstractBesides the formation of acylium ions, the molecular ions of 1‐acyl‐1,2,4‐triazoles substituted (R) at position 3 lose competitively ketene and carbon monoxide after electron impact ionization, but the ketene loss dominates largely if R is a strong electron‐donating substituent. This supports the occurrence of an ion‐molecule complex which incorporates a substituted triazole and ionized ketene before the decarbonylation (methylene transfer) or the ketene elimination (hydrogen transfer).Flash‐vacuum pyrolysis (FVP) of these triazolides yields oxazoles with specific substitution at positions 2 (R) and 5 which implies an irreversible sigmatropic [1,5(1,2)] transformation. Oxazole formation dominates largely a competitive ketene loss if the triazolides bear a strong electron‐donating substituent like N(CH3)2; this kind of substitution does not however allow the migration of groups like CO2CH3 and CONH2 which have a lower migratory aptitude.The fragmentation of the ionized oxazoles is highly dependent upon the nature of the substituent at position 5 (methyl or phenyl) and is directed by ring cleavages, mainly of the 1,2‐bond. Moreover, compounds bearing a N(CH3)2 group undergo a complex rearrangement which eliminates (C, H3, N) from the molecular ions (for the oxazoles) or from the fragment ions [M‐C2H2O]−+ (for the azolides).
Heteropoly Acid‐Catalyzed Reactions of Terpenes I. Direct Hydration of Camphene
Authors: Schwegler M. A. , van Bekkum H. 
Published: September 2010

AbstractThe heteropoly acids 12‐tungstophosphoric and 12‐tungstosilicic acid are excellent catalysts in the homogeneous hydration of camphene to isoborneol. The effects of a number of reaction variables are reported.
Nouveaux décontaminants. Destruction chimique totale, rapide et douce d'insecticides et de toxiques de guerre par les peracides
Authors: Lion C. , Charvy C. , Hedayatullah Mir , Bauer P. , Sentenac‐Roumanou H. , Despagne B. , Delmas G. 
Published: September 2010

AbstractPeroxyacids RCOOOH (R = n C7H15 to n C13H27) are very good decontamination reagents. Paraoxon (O,O‐diethyl O‐p nitrophenyl phosphate, VX [O‐ethyl S (2‐diisopropylaminoethyl)methylphos‐phorothiolate] and HD (2,2′‐dichlorodiethylsulfide) react for example, with perdodecanoïc acid, completely in a few seconds. The reaction rate is enhanced by micellar catalysis.
Improving the One‐Electron States of ab initio GTO Calculations in Momentum Space. Tests on two‐Electron Systems: H−, He and Li−+
Authors: Delhalle Joseph , Fripiat Joseph G. , Defranceschi Mireille 
Published: September 2010

AbstractA study of a one‐step iteration method expressed in momentum space to improve properties calculated at the Hartree‐Fock level is presented. The results obtained for two‐electron atoms H−, He and Li−+ show substantial and consistent improvement in their 1s ground‐state orbital initially expressed as a linear combination of four gaussian functions.
Synthèse dans la chimie des phenanthridines. III. Préparation de quelques modèles d'acides ω‐(diamino ‐3,8 phenanthridinyl‐6) carboxyliques
Authors: Lion C. , Boukou‐Poba J. P. , Charvy C. 
Published: September 2010

AbstractNew series of ω‐(3,8‐diamino‐6‐phenanthridinyl) alkanoic acids are obtained from the acid chloride‐esters ROCO(CH2)nCOCl (n = 0,3 to 8; R = Me or Et). Reaction of these with 2‐amino‐3,8‐ dicarbethoxyaminobiphenyl leads to the expected 2‐acylamino‐3,8‐ dicarbethoxy‐aminobiphenyls which by cyclization lead to the corresponding methyl or ethyl (3,8‐dicarbe‐thoxyamino‐6‐phenanthridinyl)alkanoates. Quaternarization followed by hydrolysis has been performed to obtain some ω‐(3,8‐diamino‐6‐phenanthridinium) alkanoic acid salts.
The N‐Alkane Solvent Effect on the Dipole Moment of the Trans‐1,2‐Dibromocyclohexane
Authors: Dionísio Madalena , Almeida Luís N. , Moura‐Ramos Joaquim 
Published: September 2010

AbstractDipole moment techniques have been applied to the study of the n‐alkane environmental influence on the conformational equilibrium of trans‐1,2‐dibromocyclohexane. Both the Debye and the Onsager theories have been used in order to calculate the dipole moment from the dielectric constants of the liquid solutions, and the results have been obtained in five different n‐alkane solvents. The eventual influence of the solvent molecular order in the position of the equilibrium is discussed.
Infrared Study of Surface Properties of Alumina Supported Chromia: Nitric Oxide Adsorption
Authors: Batis H. , Younes M. K. , Ghorbel A. 
Published: September 2010

AbstractInfrared study of NO adsorption on chromia/alumina catalysts gives interesting information concerning both the surface heterogeneity and the reactivity of alumina‐supported Cr ions.On a preoxidized surface NO interacts with oxygen ligands to form nitrite and nitrate species. However in the presence of chemisorbed NH3 on oxidized catalyst the mobility of oxygen is strongly increased and can be displaced by NO molecules to form surface complexes with bands at 1715 and 1855 cm−1On a prereduced surface, coordinatively insaturated Cr ions are created. A small fraction of these ions with one coordination vacancy adsorb weakly one NO molecule giving rise to a band at 1810 cm−1. These ions are poisoned by most strongly adsorbed NH3 as would be expected for Cr−4+ ions. Most of the Cr ions coordinate a couple of NO molecules to form stable Cr(NO)2 complexes with bands at 1725 and 1865 cm−1.
Reactions of Thiocarbonyl Ylides With Sulfur Dioxide; A Route to a Novel Heterocyclic System
Authors: Mlostoń Grzegorz 
Published: September 2010

AbstractThiocarbonyl ylides generated from Δ−3‐1,3,4‐thiadiazolines la‐c by thermal extrusion of nitrogen undergo 1,3‐dipolar cycloadditions with sulfur dioxide, giving 1,2,4‐oxadithiolane 2‐oxides 3a‐c in good yields.
Mössbauer Study of Some Polymeric Iron(II) Complexes of Halo‐Salicylhydroxamic Acids
Authors: Kane S. N. , Ali S. M. , Gupta Ajay , Khadikar P. V. 
Published: September 2010

AbstractPolymeric complexes of iron (II) salicylhydroxamic acids: Fe‐SHA, Fe‐5CSHA, Fe‐3,5DCSHA along with Fe‐BHA, where SHA = salicylhydroxamic acid, 5CSHA = ‐5‐chloro salicylhydroxamic acid, 3,5DCSHA = 3,5 di‐chloro salicylhydroxamic acid and BHA = Benzohydroxamic acid, have been prepared, characterized by elemental and spectral analysis and identified by the electronic spectra as ML2.2H2O, where L stands for the salicylhydroxamic acid moiety and M stands for Fe(II). Various Mössbauer parameters obtained at room temperature, change with respect to the kinds of chelating agent which may be attributed to the effect of substitution in the salicylhydroxamic acid moiety. Quadrupole splitting and isomer shift values have been explained in terms of restricted rotation between C6H5‐°C‐ bond due to the π‐electron system in the benzene nucleus.
Transport of Amino Acids Methyl Esters by a Bicyclic Crown Ether
Authors: Janus Stephan , Kraïmi Khalil , Sonveaux Etienne 
Published: September 2010

AbstractRacemic protonated amino acid methyl esters were efficiently transported through a dichloromethane phase using L,L‐Cbz‐bis(15‐crown‐5)DOPA‐OMe as a carrier. The enantioselectivity was however marginal. The (15‐crown‐5) rings of the carrier were essential for affinity, as Cbz‐bis(12‐crown‐4)DOPA‐OMe was not a good host.
Oxidation of Benzylamines by Alkyl Sulphoxides
Authors: Azran Jacques , Buchman Ouri , Pri‐Bar Ilan 
Published: September 2010

AbstractPrimary, secondary and tertiary benzylamines were oxidized to aromatic aldehydes and ketones when their HX (X = Br, I) salts were heated, under anhydrous conditions, in excess of alkyl sulphoxide. Quaternary benzylammonium salts also react, to give lower yields of carbonyl compounds. Benzylamine is being oxidized in the presence of anhydrous HX formed in situ by the reaction of alkyl halide and hydrosiloxane, but not in the presence of aqueous HX.
Diverse CO2− Radicals in γ‐ and α‐Irradiated Synthetic Calcite
Authors: Debuyst RenÉ , Bidiamambu Mawete , Dejehet Fernand 
Published: September 2010

AbstractModifications in the synthesis procedure of calcite involve statistically significant changes in the relative intensities of the EPR lines of the irradiated samples.Of the 6 (or 8) paramagnetic centres produced by γ‐ (or α‐) irradiations, four are attributed to the CO2− radical:
The first one is an unstable anisotropic species with g1 ≃ 2.0028, g2 ≃ 2.0022, g3 ≃ 1.9971 and a hyperfine coupling of ∼2.6 gauss with 2 equivalent I = 1/2 nuclei.
The second one is a more stable species with a larger linewidth and g1 ≃ 2.0028, g2 ≃ 2.0011 and g3 ≃ 1.9972.
The third one is an isotropic species with g = 2.0007.
The last one is an axial species with g∥ = 2.0032 and g⟂ = 1.9995 solely produced by an α‐particle bombardment
.
Catalysed Quantitative Synthesis of 2,3,3‐Trichlorotetrahydrofuran
Authors: Buyck Laurent De , De Lepeleire Carine 
Published: September 2010

AbstractTetrahydrofuran was chlorinated in the presence of N,N‐dimethyloctylamine (1 mmol per mol optimal) with an excess of sulfuryl chloride at 55‐80°C. After a first stage producing trans 2,3‐trichloro THF (1) the reaction proceeded to complete conversion to 2,3,3‐trichloro THF (2) in less than 22 h.The mechanism is discussed in terms of an inhibitory effect of hydrogen chloride and a catalytic role for anions unintentionally derived from the sulfuryl chloride.Equilibration of 2 with the isomer 2,2,4‐trichlorobutanal (3) was observed at 130‐170°C with hydrogen chloride catalysis, at 70°C with titanium tetrachloride or zinc chloride.
Aromaticity: A new Multilinear Approach
Authors: Párkányi Cyril , Boniface Christian 
Published: September 2010

AbstractSix equations obtained by multiple regression analysis were developed to characterize aromaticity of alternant and nonalternant hydrocarbons. Three equations are applicable to alternant systems, three to nonalternant systems. The quantities used in the equations are the various experimental and theoretical (HMO and SCF‐MO) data reflecting aromatic behavior of delocalized π–electron systems. The aromaticity index, AI, is given as a numerical value and the equations can be used to predict aromaticity of various compounds on a quantitative basis.
Studies on the Thermal Rearrangement of 2‐Methoxypyridine N‐Oxides to 1‐Methoxypyridin‐2‐Ones
Authors: Ballesteros Paloma , Senent Salvador , Elguero José 
Published: September 2010

AbstractA study of the influence of the solvent polarity on the rearrangement of 2‐methoxypyridine N‐oxides to 1‐methoxypyridin–2‐ones suggests an ionic mechanism.
Design, Synthesis, and Properties of Macrocyclic Receptors for Tetrahedral Substrates
Authors: Collet André , Dutasta Jean‐Pierre , Lozach Bénédicte 
Published: September 2010

AbstractIn order to complex lipophilic molecules of tetrahedral shape, hosts made of two cyclotriveratrylene caps have been designed and named ”cryptophanes“. Cryptophanes can be synthesised in two different ways from vanillyl alcohol. In a first method, a C3‐cyclotriveratrylene of suitable structure is prepared and used as a template for intramolecular assemblage of the second cap. In a second method, much shorter, the two cyclotriveratrylene caps of the cryptophane are simultaneously built from appropriate vanillyl alcohol dimers. The complexation of halogenomethanes, aliphatic hydrocarbons, and polymethylammonium ions by certain D3‐cryptophanes has been studied. Neutral molecules such as chloroform and isobutane are comparatively strongly bound in organic solvents (1,1,2,2‐tetrachloroethane‐d2) and very strongly bound in water, whereas the tetramethylammonium cation shows an inverse behaviour. Choline and acetylcholine are bound in water at pH 5‐8. Some possible applications of these results are discussed.
Non Steady‐State Transient Kinetic Approach with Deuterium Labelling. I. Improved Method to Relate Catalytic Activity to Surface Coverage
Authors: Lienard G. , Degols L. 
Published: September 2010

AbstractA method is described to acquire, in addition to catalytic reaction rates, the reactant adsorption rate, the surface coverage and its rate of formation. It is based on a non steady‐state transient technique, initiated by a pressure step of one reactant corresponding to adsorption (build up of the catalytic active surface) or to desorption (titration of adsorbed species). Deuterium is used instead of light hydrogen to differentiate by labelling, in the adsorption step, the reactant molecules (deuterated isomers) being desorbed without further reaction. The relaxation of the catalytic system is followed and time constants are defined (exponential variations with time), characterizing the different rates.A novel UHV apparatus, working in the pressure range 10−5 to 1 Torr, is described. Data are acquired by a computer that controls the electromagnet of a magnetic deflection mass spectrometer. A complete spectrum is scanned in less than 12s by a peak jumping method. The technique is applied to a typical experiment of hydrogenolysis of ethane, on a Rhodium evaporated film. Ethane rate of adsorption remains constant during the build up transient effect while the rate of hydrogenolysis and of perdeuterated isomer increase with time and are characterized by the same time constant as the rate of formation of the carbonaceous layer (Rcs). This indicates that the observed activity variations are not directly related to the adsorption rate. A quantitative relationship between Rcs, the rate of hydrogenolysis and the rate of formation of perdeutered isomer is established. The role of deuterium for the determination of the adsorption rate is analysed.
Non Steady‐State Transient Kinetic Approach with Deuterium Labelling. II. Ensemble Effect and Mechanism Proposal in Ethane Hydrogenolysis Over Model Rh Catalyst
Authors: Lienard G. , Degols L. 
Published: September 2010

AbstractReaction of ethane over rhodium model catalyst is studied using a method combining non steady‐state transient effect and labelling with a large excess of deuterium. Relaxation of the catalytic system after an ethane pressure jump as well as rates at steady‐state activity are measured, at 50°C, in a deuterium pressure range from 10−3 to 10−1 Torr. The method differentiates the part of ethane adsorption rate (Rac) that produce carbonaceous species, intermediates for hydrogenolysis.The important variations of the rates of ethane adsorption Rac and of hydrogenolysis with hydrogen pressure and temperature are analyzed in the frame of the ensemble model developped preciously. Both rates are regulated by the demanding character of finding an ensemble of free sites but a larger ensemble is required for hydrogenolysis than for ethane adsorption. In using the formalism of the ensemble model, activation energies are calculated as low as 17 kJ/mole for adsorption and 8kJ/mole for hydrogenolysis. The temperature factors experimentaly measured are strongly depending on the hydrogen coverage θH.It is concluded that all the steps in the reaction scheme, except the desorption one, are reversible but in a more or less degree, depending on the hydrogen coverage. Thus the ethane adsorption step may vary, according to the experimental conditions (p,T) from complete irreversibility (hydrogenolysis formation), at low θH, to nearly complete reversibility, for high θH coverage values. In this case ethane adsorption still proceeds without hydrogenolysis.
Growth of Large Crystals of Aluminophosphate Molecular Sieve AlPO4‐5
Authors: Kornatowski Jan , Finger Gerd 
Published: September 2010

AbstractLarge crystals of the molecular sieve AIPO4‐5 up to 920 μm in length have been grown during hydrothermal synthesis by using triethylamine as a templating agent. The yield of the AlPO4‐5 phase is within a range of 50 ‐ 60%.
Gradients in the Composition of Enamel and Dentin Mineral in Rat Incisors
Authors: Driessens F. C. M. , Goldberg M. , Heijligers H. J. M. , Carreau J. P. , Verbeeck R. M. H. 
Published: September 2010

AbstractIn order to investigate possible differences in the mineral composition of rat incisors, Wistar rats received either a zinc‐deficient or a normal diet (the latter were pair fed or ad libitum). Three incisors from each group were subjected to microanalysis by the electron microprobe. No differences were found in mineral composition between the three groups. The average molar Ca/P ratio in the enamel and the dentin were (1.62 ± 0.05) and (1.50 ± 0.05), respectively. The distribution of sodium and magnesium over the dentin was homogeneous and inhomogeneous, respectively. Dentin did not contain detectable amounts of chlorine. The gradients for sodium, magnesium and chlorine as a function of depth in enamel were similar to those reported for these elements in human and rhesus monkey enamel: sodium and magnesium had a low concentration at the enamel surface, whereas chlorine had a high concentration there.
Sorption of organic compounds from water with new polymer sorbents
Authors: Martel Bernard , Delporte Michèle , Lekchiri Yahya , Morcellet Joëlle , Morcellet Michel 
Published: September 2010

AbstractNew organic polymer sorbents based on macroporous polymers containing amino groups and β‐cyclodextrin residues have been synthesized by suspension polymerization. The sorption capacity of these sorbents with respect to organic pollutants such as phenol has been determined and discussed in terms of polarity and specific interactions.
Polymerization of methyl and phenyl oxazoline initiated with alkyl chloroformates
Authors: Dworak Andrzej , Schulz Rolf C. 
Published: September 2010

AbstractIt has been shown that alkyl chloroformates are capable of initiating the polymerization of oxazolines. Esters itself initiate rather slowly and the polymerization proceeds via covalent growing species. Exchange of counter ions with triflate or iodide anions leads to faster initiation and higher reaction rates. The polymerization is of living character.
Facilitated passive copper(II) ion transport through binary liquid membrane
Authors: Szpakowska Mariola , Nagy Ottó B. 
Published: September 2010

AbstractFacilitated passive transport of Cu(II) through binary liquid membranes of variable composition has been studied in steady state conditions. It is shown that transport kinetics obeys the competitive preferential solvation(COPS) theory in the whole concentration range. The geometric‐electronic structure of the metal ion‐carrier complex seems to play a decisive role in the preferential solvation.
Synthesis of trideoxyhexopyranosylated and hexenopyranosylated nucleoside analogues as potential anti‐HIV agents
Authors: Herdewijn P. , van Aerschot A. 
Published: September 2010

AbstractThe 2‐deoxy‐D‐arabino‐hexopyranosyl nucleoside analogues of thymidine, deoxyuridine and deoxycytidine have been prepared by sugar‐base condensation and a 3,4‐unsaturated bond was introduced via the bisdithiocarbonates. Hydrogenolysis in the presence of Pd on carbon afforded the 2,3,4‐trideoxy‐D‐glycero‐hexopyranosyl analogues.
Photolytic α‐scission in Acyl Phosphonic Acid Esters
Authors: Majima T. , Schnabel W. 
Published: September 2010

AbstractA re‐investigation of the photolysis of acyl phosphonic acid dimethyl‐ and diethyl esters revealed that commonly α‐scission occurs although the quantum yield ϕ(α) depends on the chemical nature of the acyl group:magnified imageϕ(α) = 0.2‐0.3 in the cases of pivaloyl and substituted benzoyl phosphonates and ϕ(α)=0.03 in the case of benzoyl phosphonic acid diethyl ester (BPDE). The major route of deactivation of electronically excited phosphonates involves intersystem crossing (ISC) to the triplet manifold. ISC was studied by triplet quenching using naphthalene. Quantum yields of triplet formation ϕ(T) = 0.5‐0.6 were found in all cases except BPDE (ϕ(T) = 0.9). The reaction mechanism of a typical phosphonate (2,6‐dichlorobenzoyl phosphonic acid dimethyl ester, DCPME) is discussed on the basis of recent results.
Cationic Photoinitiators: A Laser Flash Photolysis Study of the Interaction of Onium Salts with Ketocoumarins
Authors: Manivannan G. , Wu S. K. , Fouassier J. P. 
Published: September 2010

AbstractTime‐resolved laser‐spectroscopy investigation has been performed for the first time on the excited state interaction of different ketocoumarins with onium salts in methanol. Ketocoumarins'triplet state quenching by monomers lead to evaluate the quantum yield values of charge transfer.
On the Tautomeric Structure of 5‐hydroxy‐ and 5‐mercapto‐1H‐1,2,3‐triazoles: −13C NMR analysis
Authors: L'abbé Gerrit , Delbeke Pieter , van Essche Gonda , Luyten Ingrid , Vercauteren Karin , Toppet Suzanne 
Published: September 2010

AbstractThe title compounds have been analyzed by 13C NMR spectroscopy and compound with the N‐3 methyl and O/S alkyl derivatives. The mesoionic structures 2a,b are rejected in favour of 1a,b on the basis of the C5=CH coupling constants and the chemical shifts. Incremental substituent effects for triazoles are discussed.
Photopolymerization of N,N‐Didodecyl‐N‐Methyl‐N‐(2‐(Methacryloyloxy)ethyl)Ammonium Chloride, a Reverse Micelle and Monolayer Forming Surfactant
Authors: De Schryver Frans , Voortmans Gilbert , Jackers Carine , Wittouck Nadine , Persoons André 
Published: September 2010

AbstractIn previous reports it was shown that the photopolymerization of N,N‐didodecyl‐methylethylmethacrylate ammonium chloride, a reverse micelle forming surfactant, leads to a transparent polymerized inverse micellar solution1,2. The polymerization leads to high molecular weight polymer as determined by GPC. However recent results indicate that GPC, due to the association of the polymer overestimates the molecular weight.In addition a more extensive characterization of the polymeric aggregates is presented. The polymerization of the inverse micellar solution leads to a more stable and less dynamic inverse micellar system. However, the obtained aggregates are much larger then the monomeric inverse micelles. On the basis of the aggregation behaviour of the polymer and the characteristics of the polymer aggregates a model describing the structure of the polymer aggregates is proposed.Finally the monolayer formation and properties of the monomer and polymer are compared.