Eine neue Methods zur Einführung von CF3- und C2F5-Gruppen in Pyrimidinderivate und die Anti-Herpes-Aktivität der Verbindungen

A New Method of the Introduction of CF₃- and C₂F₅-Groups into Pyrimidine Derivatives and their Antiherpes Activity A new method of the perfluoroalkylation of uracil derivatives is described. The irradiation of aqueous solutions of uracil and uracilnucleosides with bis-(perfluoroalkyl) mercury (C_nF_2n+1)₂Hg n = 1, 2 under the exclusion of oxygen in the presence of catalytic amounts of azo-bis-isobutyronitril at 254 nm for several hours gave new 5-perfluoroalkylated compounds. In this way we obtained 5-trifluoromethyluracil ( 5a ), 5-pentafluoroethyluracil ( 5b ), 5-trifluoromethyl-2′-deoxyuridine ( 6a ), 5-pentafluoroethyl-2′-deoxyuridine ( 6b ) and 1-(ß-D-arabinofuranosyl)-5-trifluoromethyluracil ( 7a ) in different yields. The perfluoroalkylated compounds were tested against HSV-1 and HSV-2 viruses on human lungefibroblasts. The compounds are markedly less potent than other known nonfluorinated compounds.     

Aryl Migrations During Pulping

Aryl migrations taking place during pulping processes are described. Migrations from C_αto C_β are given by “condensed” β-O-4 units and result in fragmentation and the formation of potential chromophoric systems of the stilbene type. Migrations from C_βto C_α, on the other hand, are observed with stilbenoid units and their precursors (β-1 and β-5 units) and afford 1,1-diaryl-2-oxo structures. Both types of aryl migration proceed via 3-membered spiro-cyclohexadienone intermediates. The direction of the aryl migrations may affect the ease and extent of lignin fragmentation and the formation of potential chromophoric groups during pulping processes     

Direct Hydroxylation of Benzene to Phenol with Molecular Oxygen over Phase Transfer Catalysts: Cyclodextrins Complexes with Vanadium-Substituted Heteropoly Acids

Cyclodextrins (CyDs) complexes with vanadium-substituted heteropoly acids (PMoV _n -β-CyDs, n = 1, 2) were prepared by simple mixing and their structures were characterized by FT-IR. Among various catalysts, PMoV₁-β-CyDs, an efficient phase transfer catalyst, exhibited the highest yield (13.1%) of phenol without observing the formation of catechol, hydroquinone and benzoquinone in direct hydroxylation of benzene to phenol in 80 vol% aqueous acetic acid with molecular oxygen and ascorbic acid used as the oxidant and the reducing reagent, respectively. The influences of the reaction temperature, the pressure of oxygen, the amount of ascorbic acid, the amount of catalyst, and the reaction time on the yield of phenol were investigated to obtain the optimal reaction conditions for phenol formation.     

Oxidation of aqueous sulfur dioxide catalyzed by poly-4-vinylpyridine–Cu(II) complex. Part 1: Homogeneous phase oxidation

The oxidation of aqueous sulfur dioxide in the presence of polymer-supported copper(II) catalyst is also accompanied by homogeneous oxidation of aqueous sulfur dioxide catalyzed by leached copper(II) ions. Aqueous phase oxidation of sulfur dioxide of low concentrations by oxygen in the presence of dissolved copper(II) has therefore been studied. The solubility of SO₂ in aqueous solutions is not affected by the concentration of copper(II) in the solution. In the oxidation reaction, only HSO is the reactive S(IV) species. Based on this observation a rate model which also incorporates the effect of sulfuric acid on the solubility of SO₂ is developed. The rate model includes a power-law type term for the rate of homogeneous phase reaction obtained from a proposed free-radical chain mechanism for the oxidation. Experiments are conducted at various levels of concentrations of SO₂ and O₂ in the gas phase and Cu(II) in the liquid phase. The observed orders are one in each of O₂, Cu(II) and HSO. This suggests a first-order termination of the free radicals of bisulfite ions.     

Hydrogenation of CO2 Over Skeletal Copper Surfaces Containing Precipitated ZnO

Catalysts have been prepared by precipitating different amounts of ZnO on the surface of skeletal copper particles. The precursor copper catalysts were prepared by fully leaching CuAl₂ particles with concentrated NaOH solutions in the presence and absence of sodium chromate. The resulting catalysts contained surface zinc oxide concentrations in the range 0-1.36 mg per m² of catalyst surface.The influence of different concentrations of ZnO on the surface of skeletal copper was examined by the hydrogenation of CO₂ using a mixture of 24% CO₂/76% H₂ at 4 MPa, 493-533K and space velocities up to 410 700 h^-1. The catalysts were found to be highly active and selective for methanol synthesis. Methanol synthesis activity increased linearly with ZnO loadings with a maximum being reached at a loading of around 1.1 mg m^-2 for higher surface area skeletal copper prepared by leaching in the presence of chromate. ZnO loadings were also shown to improve the selectivity of CO₂ hydrogenation over copper by reducing the formation of CO by the reverse water-gas shift reaction.     

Synthese und Strukturaufklärung von 19-Nor-pregnanderivaten mit stickstoffhaltigen Vierringen in 14,15-Stellung

Synthesis and Structural Elucidation of 19-Nor-pregnane Derivatives with Nitrogen-Containing Four-Membered Rings in 14,15-Position The introduction of a C₂ side chain in the 17-position of 3-methoxy-14β, 15β-(3′,4′-azetidine)-estra-1,3,5(10)-trien-17β-ol ( 1 ) is described. Hydroboration of the 17-ethylidene compound 4 gives a mixture of the 17αH and 17α-pregnane derivatives 6 and 6a in 70% and 10% yields, respectively. Birch reaction of 6 , followed by oxidation yields the 14β,15β-(3′,4′-azetidine)-19-nor-pregn-4-ene-3,20-dione ( 12 ). The new compounds were characterized by ¹H-n.m.r. The structure of product 13 was determined by X-ray crystallography.     

Synthesis of atropisomeric chiral MeOBIPHEP analogues via Pd-catalyzed P–C coupling — applications to asymmetric Rh-catalyzed C–C bond formations in water

The preparation and catalytic applications of water-soluble MeOBIPHEP-based atropisomeric chiral congener ligands are described. The optimization of the catalytic system to promote the key P–C coupling revealed the superiority of palladium catalysts versus nickel or copper. Spectroscopic studies of the Pd-catalyzed reaction medium showed the presence of phosphorylated intermediates. The asymmetric Rh-catalyzed 1,4-addition of boronic acids to enones in water was described in the presence of water-soluble MeOBIPHEP derivatives. The 4-CO₂Na-, 3-CO₂Na- and 3,5-(CO₂Na)₂-substituted MeOBIPHEP analogues showed high and complementary reactivities and enantioselectivities, considering either the enone or the boronic acid.     

Cu/Al2O3 catalysts for soot oxidation: Copper loading effect

Cu/Al₂O₃ catalysts with metal loading from 0.64 to 8.8 wt.% have been prepared and characterized by different techniques: N₂ adsorption at −196 °C (BET surface area), ICP (Cu loading), XRD, selective copper surface oxidation with N₂O (Cu dispersion), TPR-H₂ (redox properties), and XPS (copper surface species). The catalytic activity for soot oxidation has been tested both in air and NO_x/O₂. The activity in air depends on the amount of easily-reduced Cu(II) species, which are reduced around 275 °C under TPR-H₂ conditions. The amount of the most active Cu(II) species increases with the copper loading from Cu_1% to Cu_5% and remains almost constant for higher copper loading. In the presence of NO_x, the first step of the mechanism is NO oxidation to NO₂, and the catalytic activity for this reaction depends on the copper loading. For catalysts with copper loading between Cu_1% and Cu_5%, the catalytic activity for soot oxidation in the presence of NO_x depends on NO₂ formation. For catalysts with higher copper loading this trend is not followed because of the low reactivity of model soot at the temperature of maximum NO₂ production. Regardless the copper loading, all the catalysts improve the selectivity towards CO₂ formation as soot oxidation product both under air and NO_x/O₂.     

Oxidative dehydrogenation of 5-(pyridine-2-yl-methyl)-2-thioxo-4-imidazolidinones in complexation reaction with copper(II) chloride

The treatment of 5-(pyridine-2-yl-methyl)-2-thioxo-4-imidazolidinones with copper(II) chloride dihydrate led to the formation of a dinuclear copper complex L₂Cu₂Cl where L is a dehydrogenated initial organic ligand. X-ray diffraction analysis indicated that the starting 3,5-dihydro-4H-imidazole-4-ones undergo oxidation in the course of the reaction with the formation of an exocyclic double bond at C5 position.     

Syntheses of pyrazole monomers

(1-Phenyl-5-methyl-pyrazolyl-4)-acetylene was prepared by treating 1-phenyl-4-acetyl-5-methyl-pyrazole with Vilsmeier complex. During the first stage of the reaction the β-(1-phenyl-5-methyl-pyrazolyl-4)-β-chloro-acroleine separated, and suffered in the presence of alkali a dechloroformylation to form the ethinylic compound. As the acroleine intermediate is an α,β-unsaturated aldehyde it can react with substituted hydrazines leading to substituted pyrazoline derivatives. The structures of the monomers were confirmed by means of IR and NMR spectral measurements. In the presence of PdCl₂ as catalyst, oligomers were obtained which have then been transformed into charge transfer-complexes. Variation of the ESR signal intensity was followed as a function of A/D ratio.     

Reduction of chalcopyrite with copper (I)

In the presence of Cu(I), chalocopyrite is reduced to Cu₂S and Cu₅FeS₄. Electrochemical studies on polished chalcopyrite crystals establish that this reaction is electrochemical in nature and dependent on the redox potential of the copper(II)/copper(I) couple. A sharp decrease in the initial rate of reduction is observed which is attributed to the rapid formation of bornite and diffusion of Cu(I) through a thickening film. Subsequent reaction of bornite to chalcocite is a slow electrochemical reaction with a Tafel slope of ? 162±5mV.     

Correlation of electrochemical and ellipsometric data in relation to the kinetics and mechanism of Cu2O electroformation in alkaline solutions

The kinetics of copper anodization were studied in the potential range of Cu₂O electroformation in different alkaline solutions by using voltammetric, rotating disc electrode, rotating ring-disc electrode and ellipsometric techniques. Thin layer and massive copper electrodes were employed. Results indicate the formation of soluble Cu(I) species at the early stage of copper anodization. Other soluble Cu(II) species are produced after the Cu₂O layer electroformation. Data are discussed on the basis of a reaction mechanism involving different reaction products and the influence of the copper surface on the initial electrochemical reaction.     

Multinuclear Cu(II) Schiff Base Complex as Efficient Catalyst for the Chemical Coupling of CO2 and Epoxides: Synthesis, X-ray Structural Characterization and Catalytic Activity

Abstract  

The synthesis, X-ray structure, spectroscopic and catalytic properties of sterically hindered Schiff-base ligands (L₁H = N-[allylamine]-3,5-di-tert-butyl salicylaldimine, L₂H=N-[2-amino-5-methyl pyridine]-3,5-di-tert-butyl salicylaldimine and L₃H=N-[2-amino-6-methyl pyridine]-3,5-di-tert-butyl salicylaldimine), and their mononuclear Cu(II) complex for L₁H with multinuclear Cu(II) complexes for L₂H and L₃H, were described. The copper(II) complexes of these ligands were synthesized by treating an methanolic solution of the appropriate ligand with an appropriate amount of CuCl₂·2H₂O. The ligands and their copper(II) complexes were characterized by FT-IR, UV–Vis, ¹H-NMR, elemental analysis, measurement of room temperature magnetic moment, and X-ray structural determination. The reaction of the L₂H and L₃H ligands in a 1:1 mol ratio with CuCl₂·2H₂O afforded ionic copper metal(II) complexes in the presence of NEt₃. The Cu(II) metal complexes tested as catalysts for the formation of cyclic organic carbonates from carbon dioxide and liquid epoxides which served as both reactant and solvent. [Cu₃(L₂)₄]Cl₂·CuCl₂ complex which has 5-methyl substituent on the pyridine ring showed high catalytic activity for chemical coupling carbon dioxide with epoxides (propylene oxide (PO), epichlorohydrine (EC) and 1,2-epoxy butane (EB)) selectively.     

Electrochemical investigation of copper–DTPI interactions

The electrochemical behavior of copper in the absence and presence of a dithiophosphinate type collector, sodium diisobuthyldithiophosphinate (NaDTPI), was determined to investigate the interactions between a copper surface and NaDTPI as a function of pulp potential (Eh) and pH. The electrochemical studies were performed by Cyclic Voltammetry (CV) in the −355 to +1550 mV (SHE) potential range and at different pHs from slightly acidic to strongly alkaline conditions. The electrochemical studies were carried out for copper and DTPI alone as well as with DTPI added copper system. DTPI addition had considerable effects on the electrochemical behavior of copper. CuDTPI formation was the main reaction at all pHs through a mixed mechanism and oxidation of the copper surface was followed by a chemical reaction between copper and DTPI ions. Formation of a cupric metal-collector complex, Cu(DTPI)₂, was observed only in acidic conditions in the form of an unstable surface compound.     

Reduction of nitric oxide by carbon monoxide on copper catalysts

An experimental study has been carried out of the kinetics and mechanism of the reduction of NO by reaction with CO on unsupported and supported copper catalysts. At low CO concentrations ($\text{3 <}\text{CO}\text{NO}\text{< 10}$), the kinetics of this reaction exhibit an effective reaction order of unity with respect to NO; hence, the fractional conversion is independent of the reactant level. However, relatively high CO concentrations ($\text{CO}\text{NO}\text{> 10}$) in the gas stream cause reaction inhibition. On the basis of the experimental results a reaction mechanism is proposed involving dissociative chemisorption of nitric oxide. The formation of an isocyanate (NCO) species on the copper surface is responsible for reaction inhibition. This species acts as the precursor for ammonia formation in the presence of water vapor. The dissociative chemisorption step of NO on a copper surface has an activation energy of 9.3 kcal/mole, a value unaffected by such supports as SiO₂ or CuAl₂O₄.     

Formation of calcium plumbate: Kinetics and mechanism of reaction

In the presence of excess air the kinetics of reaction between CaO and PbO to form calcium plumbate are governed by the diffusion process described by Jander's kinetic model. The energy of activation of the process, as calculated from the Arrhenius equation, is 50 kcal/mol. In an air and nitrogen atmosphere (ratio 1:16) the reaction rate is 4–5 times slower. It has been shown that formation of calcium plumbate from pure CaO and PbO takes place between 600–800° without formation of intermediate compounds. From the results obtained it is deduced that the mechanism of formation consists of two main stages–diffusion between the CaO and PbO, substantially due to the more diffusible PbO, and chemical reaction in the presence of O₂.     

The initial behaviour of freshly etched copper in moderately acid, aerated chloride solutions

When freshly etched samples of various types of copper were exposed in moderately acid, aerated chloride solutions, two phenomena were observed. First the corrosion potential and the pH of the solution decreased over a shorter time, then the potential increased over a long period (600-1500 min), following an s-shaped pattern. Increase in pH during the second stage was avoided using a pH-stat. The corrosion rate increased little or not at all over the entire period. A tentative interpretation of the short-term behaviour is presented with some reservation. The long-term development of the potential suggests phase formation or transformation following the Avrami pattern. By suitable derivations it was possible to fit the development of potentials to the Avrami equation. Subsequent examinations by Auger spectroscopy proved the presence of thin layers of Cu₂O on the copper surfaces, increasing in thickness with exposure time. The dissolution kinetics can be described in terms of two parallel electrochemical reactions and a simultaneous non-electrochemical dissolution reaction.     

One-pot template synthesis and crystal structure of two new polyaza copper(II) complexes

A new 14-membered hexazamacrocyclic copper(II) complex [Cu(H₂L¹)](ClO₄)₄(L¹=1,8-bis(2-aminoethyl)-1,3,6,8,10,13-hexaazacyclotetradecane) has been prepared by the one-pot reaction of ethylenediamine and formaldehyde in the presence of the Cu(II) ion. The crystal structure of [Cu(H₂L¹)](ClO₄)₄ was determined by X-ray diffraction. It crystallizes in the triclinic space group P−1 with a=12.118(2) Å, b=12.438(2) Å, c=12.466(2) Å, α=102.26(1)°, β=112.82(1)°, γ=111.51(1)°, and Z=2. The coordination geometry around the copper(II) ions is axially elongated octahedral with four nitrogen atoms of the macrocycle [Cu–N 2.012(7) Å for Cu(1) and 2.013(6) Å for Cu(2), average value] and two oxygen atoms of two ClO₄⁻ anions [Cu–O=2.550 Å for Cu(1) and 2.601(6) Å for Cu(2)]. [CuL²](ClO₄)₂(L²=3,7-bis(2-aminoethyl)-1,3,5,7-tetraazabicyclo[3,3,2]decane) with a novel tetraazabicyclic ligand was obtained from the same reaction system as an additional product. Crystal structure of [CuL²](ClO₄)₂: monoclinic space group Cc, a=16.393(3) Å, b=8.8640(18) Å, c= 13.085(3) Å, β=105.01(3)°, and Z=4.     

Copper inducing Aβ42 rather than Aβ40 nanoscale oligomer formation is the key process for Aβ neurotoxicity

Copper is known to be a critical factor in Alzheimer's disease (AD) pathogenesis, as it is involved in amyloid-β (Aβ) peptide related toxicity. However, the relationship between neurotoxicity and Aβ peptide in the presence of copper remains unclear. The effect of copper has not been clearly differentiated between Aβ42 and Aβ40, and it is still debated whether copper-mediated neurotoxicity is due to reactive oxygen species (ROS) accumulation or other molecular mechanisms. Here, we describe that copper dramatically affects Aβ42 aggregation and enhances Aβ42 cytotoxicity while it shows no significant effects on Aβ40. These phenomena are mainly because that the strong interactions between copper and Aβ42 lead to great conformation changes, and stabilize Aβ42 aggregates at highly toxic nanoscale oligomer stage, whereas copper shows no similar impact on Aβ40. We also propose a possible molecular mechanism that copper enhances Aβ42 cytotoxicity via perturbing membrane structure. Moreover, we test the effect of an analogue of copper, nickel, on Aβ aggregation and cytotoxicity, finding that nickel also enhances cytotoxicity via Aβ42 nanoscale oligomer formation. These results clarify that the copper-induced Aβ42 nanoscale oligomer formation is the key process for Aβ neurotoxicity, and suggest that disrupting the interactions between copper and Aβ42 peptide to inhibit nanoscale oligomerization process, deserves more attention in AD drug development.     

An Ullmann C?O Coupling Reaction Catalyzed by Magnetic Copper Ferrite Nanoparticles

Herein, an efficient method for the Ullmann C O coupling reaction between various kinds of phenols and aryl halides, including amino, ketone, cyano, methyl, methoxy, fluoro, chloro and bromo derivatives, is described. The catalyst used, copper ferrite (CuFe₂O₄) nanoparticles, are easily made, air‐stable, and of low cost. The catalyst can be recycled easily just by using an external magnet. Even in the presence of sensitive substituents, the reaction proceeds successfully to provide the desired products in high yields without protection of other functional groups.