Presence Of Copper Powder Research Articles

A novel leaching process of zinc ferrite and its application in the treatment of zinc leaching residue

Zinc ferrite is a refractory phase generated in the pyrometallurgical process of zinc and steel production. Much energy is invested in the decomposition of zinc ferrite to recycle zinc since zinc ferrite is difficult to leach. In this work, a novel leaching process targeted at decomposition of zinc ferrite was proposed to save energy and improve metal recovery efficiency. The key of this novel leaching process was the use of copper powder as the reductant. Leaching of zinc ferrite in the presence of copper powder was investigated. The extraction of zinc was 100% when molar ratio of copper to zinc ferrite was 1.5 while the extraction of zinc was only 19.3% without copper. Effects of leaching temperature, acid concentration, the ratio of liquid to solid and reaction time were studied. Under the conditions: 60 °C, ≥ 70 g·L1 H2SO4, the ratio of liquid to solid ≥ 25 mL/g and the molar ratio of copper to zinc ferrite ≥ 1.5 at the open system, the synthetic zinc ferrite was dissolved completely within 60 min. Besides, the zinc ferrite-bearing zinc leaching residue from a roast-leach-electrowin plant was analyzed and leached under the optimal conditions. It was found that most of zinc ferrite in the zinc leaching residue was removed, remaining unreacted lead sulphate in the leached residue. The leaching efficiency of zinc in zinc leaching residue reached 94.2%. The results suggest that copper powder enhanced facile and efficient zinc extraction from zinc ferrite without concentrated acid, high temperature, long reaction time and specific investment. The recyclability of copper and its intrinsic commodity value showed the potential application in industrial zinc and iron containing wastes.

Lithium-ion attack on yttrium oxide in the presence of copper powder during Li plating in a super-concentrated electrolyte.

Li plating/stripping on Cu and Y2O3 (Cu + Y2O3) electrodes was examined in a super-concentrated electrolyte of lithium bis(fluorosulfonyl)amide and methylphenylamino-di(trifluoroethyl) phosphate. In principle, Li+ ions cannot intercalate into a Y2O3 crystal because its intercalation potential obtained from first-principles calculations is −1.02 V vs. Li+/Li. However, a drastic decrease in the electrode potential and a subsequent constant-potential region were observed during Li plating onto a Cu + Y2O3 electrode, suggesting that Li+ interacted with Y2O3. X-ray diffraction (XRD) patterns and X-ray absorption fine structure (XAFS) spectra of the Cu + Y2O3 electrodes after the Li plating were recorded to verify this phenomenon. The XRD and XAFS results indicated that the crystallinity of Y2O3 crystals was lowered because of attack by Li+ ions or that the Y2O3 crystal structure was broken while the +3 valence state of Y was maintained.

Iodine Mediated Base‐Controlled Regio‐Selective Annulation of 2‐(Pyridin‐2‐yl)acetate Derivatives with Acrylic Esters for the Synthesis of Indolizines

AbstractAn iodine mediated base‐controlled reaction between 2‐(pyridin‐2‐yl)acetate derivatives and acrylic esters has been developed for the selective synthesis of 1,3‐disubstituted indolizines and 1,2‐disubstituted indolizines. A single‐pot reaction of 2‐(pyridin‐2‐yl)acetate derivatives and acrylic esters in the presence of CsOAc delivers 1,3‐disubstitued indolizines, while KHCO3 promotes the formation of C3‐iodo indolizines, which could be further de‐iodinated in the presence of copper powder, affording 1,2‐disubstituted indolizines via a sequential stepwise fashion. A plausible reaction mechanism involving radical process has been proposed for this reaction. Pd‐catalzyed reaction of C3‐iodo indolizines with aryl boronic acids has been described.magnified image

Synthesis of β-Difluoroalkylated Acrylonitriles in the Presence of Copper Powder.

A highly regio- and stereoselective copper-mediated cyanodifluoroalkylation of alkynes with ethyl difluoroiodoacetate and trimethylsilyl cyanide (TMSCN) is described. The three-component coupling reaction provides straightforward access to a variety of useful difluoroalkyl-substituted acrylonitriles. The introduction of the nitrile unit is of great importance in drug discovery for the modification of this fragment. Preliminary mechanistic investigations indicate that a vinyl iodide intermediate and a difluoroalkyl radical might be involved in this transformation.

Synthesis, structure and characterization of two new copper(І)-thioarsenates (ІІІ) constructed by the [AsS3]3− and CuSx units

Two new copper(І)-thioarsenates(ІІІ), CsCu2AsS3(1) and KCu4AsS4(2), have been synthesized solvothermally in the presence of copper powder. Compound 1 is built up of trigonal AsS3 pyramid, tetrahedral CuAsS3 and CuS3 moieties forming 4-membered, 5-membered and 6-membered rings. The fusion of these rings produces layered anions [Cu2AsS3]−, and cesium cations are located between metal-sulfide layers. The structure of 2 consists of infinite [Cu2S2]2− chain and layered [Cu6As2S6] linked to form a three-dimensional anionic framework, [Cu4AsS4]–, and containing channels in which the potassium cations reside.

Design and Synthetic Investigation towardgem-difluoromethylenated Fostriecin Analogue

Fostriecin is a promising leading anticancer compound. The α,β-unsaturated lactone in Fostriecin is believed to be the critical pharmacophore, which can covalently bind to the Cys269 residue of the PP2A subunit via a Michael 1,4-conjugate addition. We reasoned that the introduction of strong electron-withdrawing gem-difluoromethylene to replace the methylene group at the γ position of the lactone ring would lead to fostriecin analogue 4 with enhanced enzymatic binding affinity. Ac- cordingly, the synthesis of fostriecin analogue 4 was investigated. The skeleton of target molecule 4 was established conver- gently from fragments a, b and c via an magnesium mediated chelation-controlled addition and Stille coupling using Pd(CH3CN)Cl2 as catalyst. The key steps of synthesizing fragment a included the coupling between alkenyl iodide 8 and ethyl bromodifluoroacetate in the presence of copper powder and the establishment of C-5 stereocenter via lipase AK cata- lyzed kinetic resolution. The construction of C-11 and C-9 stereocenters in fragment b were realized by the lipase AK cata- lyzed kinetic resolution and CBS asymmetric reduction of α,β-unsaturated ketone 23 (BH3•PhNEt2 as reductive agent), re- spectively. The connection of fragments a and b proceeded through the magnesium mediated chelation-controlled addition procedures: fragment a (vinyl stannane) was firstly converted to vinyl lithium reagent 27 by the treatment of BuLi (1.05 equiv.) at -78 ℃, then the i-PrMgCl (2.0 equiv.) solution in THF was added dropwise to produce the critical magne- sium-ate complex intermediate A, finally the addition of fragment b solution in THF to the magnesium-ate complex A gave the coupled product 29. The Stille coupling of fragment c with vinyl iodide 39 prepared from 29 in the presence of Pd(CH3CN)Cl2 gave target molecule skeleton 40 in 85% yield. Finally, the protected fostriecin analogue 42 was successfully synthesized by a longest linear steps of 18 steps in 1.28% overall yield. However, the deprotection of compound 42 failed to give the target molecular 4. This could be caused by the instability of the fluorinated lactone in which the strong electron- withdrawing gem-difluoromethylene group enhanced the polarization of the lactone function. Keywords Fostriecin; difluoromethylene; α,β-unsaturated δ-lactone; enzymatic kinetic resolution; 1,5-oxidative cycliza- tion; hydrolysis of fluorinated lactone

ChemInform Abstract: Synthesis of 1,3-Dioxin-4-ones Having a Trifluoromethyl Group at the 5- Position: Versatile Building Blocks for Trifluoromethylated Compounds.

The reaction of 5-iodo-1,3-dioxin-4-ones with trifluoromethyl iodide in the presence of copper powder in hexamethylphosphoric triamide affords the title compounds, which can be converted either to α-trifluoromethylated β-keto acid derivatives or to uracil or oxazine derivatives bearing a trifluoromethyl group.

Synthesis of 4-Substituted 3,3-Difluoropiperidines

Synthetic strategies toward 4-substituted 3,3-difluoropiperidines were evaluated. 4-Alkoxymethyl- and 4-aryloxymethyl-3,3-difluoropiperidines were synthesized via 1,4-addition of ethyl bromodifluoroacetate to 3-substituted acrylonitriles in the presence of copper powder, followed by borane reduction of the cyano substituent, lactamization, and reduction of the lactam. This method was applied to establish the synthesis of N-protected 3,3-difluoroisonipecotic acid, a fluorinated gamma-amino acid. 4-Benzyloxy-3,3-difluoropiperidine was prepared using an analogous methodology and was converted to N-protected 3,3-difluoro-4,4-dihydroxypiperidine, a compound with high potential as a building block in medicinal chemistry.

ChemInform Abstract: Copper Powder‐Mediated Homocoupling Reactions of Iodoacetylenes to Synthesize Symmetrical 1,3‐Butadiynes.

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Copper Powder–Mediated Homocoupling Reactions of Iodoacetylenes to Synthesize Symmetrical 1,3-Butadiynes

A new route to synthesize symmetrical 1,3-butadiynes from iodoacetylenes in the presence of copper powder and pyridine was developed. Moderate to excellent yields were obtained through an efficient and simple process involving the copper powder without any further activation.

Highly Practical “Ligand‐Free‐Like” Copper‐Catalyzed N‐Arylation of Azoles in Lower Nitrile Solvents

AbstractIn lower nitrile solvents, the N‐arylation of azoles with aryl halides was achieved efficiently in the presence of copper powder without any additional ligands. Thus, the first nitrile type of monodentate ligand‐mediated, “ligand‐free‐like” copper‐catalyzed N‐arylation procedure was established.

Effect of size of copper nanoparticles on its catalytic behaviour in Ullman reaction

The condensation of iodobenzene to biphenyl is an industrially important reaction due to its significant role in organic synthesis as drug intermediates. The reaction takes place in the presence of copper powder as catalyst. We have shown in this paper that the size of the copper nanoparticles as well as its exposed surface area is responsible for the yield of chemical reaction. The uncapped copper powder showed a 43% conversion of iodobenzene to biphenyl in 5 h under our experimental conditions. Same amount of copper nanoparticles (size, ∼66 nm diameter) prepared by citrate capping showed 88% conversion of iodobenzene to biphenyl, which increased to about 95% when 8 nm diameter capped copper nanoparticles are used. Surprisingly, 5 nm size copper nanoparticles showed no change in the yield of about 95%.

Reactions of Ethyl Bromodifluoroacetate in the Presence of Copper Powder

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Synthesis of novel highly heat-resistant fluorinated silane coupling agents

Novel fluorinated silane coupling agents with a biphenyl structure, C n F 2 n+1 (C 6H 4) 2 CH 2CH 2Si(OCH 3) 3 ( n = 4, 6, and 8), were synthesized with the aim to improve the heat-resistance, oxidation-resistance, and acid-resistance of the surface modified with a common fluorinated silane coupling agent. Alcohols, Rf (C 6H 4) 2 CH(OH)CH 3, were obtained by reducing the intermediates, Rf (C 6H 4) 2 COCH 3, the products of the reaction of 4-acetyl-4′-bromobiphenyl with perfluoroalkyl iodides in the presence of copper powder. The reaction of the alcohols with phosphorus tribromide gave olefins, Rf (C 6H 4) 2 CH CH 2, which were then allowed to react with tetramethoxysilane in the presence of hexachloroplatinate(IV) catalyst to yield novel fluorinated silane coupling agents with a biphenyl structure. The coupling agents with four and six carbon atoms in their fluorocarbon chains were obtained as a colorless liquid while that with 8 carbon atoms was a white gel. Evaluations were made of the coupling agents using surfaces modified with them in terms of water contact angles, heat-resistance, oxidation-resistance, and acid-resistance. The agents behaved similarly to the conventional fluorinated silane coupling agents with respect to water contact angles, oxidation-resistance, and acid-resistance, whereas the former showed an extremely higher heat-resistance (up to 350 °C). In addition, C 6H 5 C 6H 4 CH 2CH 2Si(OCH 3) 3 and CH 3 (C 6H 4) 2 CH 2CH 2Si(OCH 3) 3 with no fluoroalkyl group were synthesized and the heat-resistance of glass surfaces modified with these compounds was examined.

Addition of α,α‐Difluoroiodomethyl Ketones to Alkenes with a Copper Catalyst.

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Copper-induced fluoroalkylation of porphyrins: solvent-dependent synthesis of fluoroalkyl chlorins and porphyrins from fluoroalkyl iodides

Treatment of copper(II) or nickel(II) porphyrins with fluoroalkyl iodides ( R f I ) in the presence of copper powder in dioxane, diglyme(DG) or tetrahydrofuran ( THF ) at 70-90°C gave β-fluoroalkyl chlorins in moderate yields. Unexpectedly, when dimethylsulphoxide ( DMSO ), hexamethylphosphoric triamide ( HMPA ) or N , N -dimethylformamide ( DMF ) was used as the solvent, with chlorobenzene as a co-solvent, the β-fluoroalkylporphyrins were obtained. In the first three solvents the reaction can be completely suppressed by p-dinitrobenzene (p- DNB ) or hydroquione ( HQ ), but not at all in the last three solvents. Apparently, a single electron-transfer mechanism may be involved in the formation of β-fluoroalkyl chlorins while fluoroalkylcopper intermediates may play a role in the production of β-fluoroalkylporphyrins. The metallofluoroalkylchlorins can be converted quantitatively to 2-hydoxyl-3-fluoroalkylchlorins by air/ SiO 2 or air/ Al 2 O 3. Additionally, the metallofluoroalkylchlorins and metallofluoroalkylporphyrins can be converted into the corresponding free-base chlorins and porphyrins, respectively, with H 2 SO 4. On the other hand, the metallohydoxyfluoroalkylchlorins under the same conditions afforded β-fluoroalkylporphyrins. Metallohydroxyfluoroalkylchlorins were readily also etherified to the corresponding metallomethoxyfluoroalkylchlorins with dimethyl sulfate ( Me 2 SO 4).

Addition of α,α-Difluoroiodomethyl Ketones to Alkenes with a Copper Catalyst

The addition reactions of <TEX>$\alpha$</TEX>,<TEX>$\alpha$</TEX>-difluoroiodomethyl n-butyl ketone, α,α-difluoroiodomethyl cyclohexyl ketone, or <TEX>$\alpha$</TEX>,<TEX>$\alpha$</TEX>-difluoroiodomethyl phenyl ketone to alkenes were successfully accomplished in good yields in the presence of copper powder. The reaction was also applicable to alkenes containing a variety of functional groups such as ester, trimethylsilyl, or ether group. Acetonitrile was determined to be the best solvent in the present study and the reaction was performed at 55 <TEX>${^{\circ}C}$</TEX> for 15-22 h. This reaction provides a new, efficient and general method for the synthesis of <TEX>$\alpha$</TEX>,<TEX>$\alpha$</TEX>-difluoro functionalized ketones.

Reactions of ethyl bromodifluoroacetate in the presence of copper powder

We have examined the reaction of ethyl bromodifluoroacetate ( 1) in the presence of copper powder as a procedure for the synthesis of compounds containing a CF 2 group. The complex formed in the above reaction reacted with vinyl or aryl iodides to give cross-coupling products, with Michael acceptors to give 1,4-addition products and with olefins to give radical addition products. The cross-coupling reaction was applied to the synthesis of 4,4-difluoro-α-tocopherol.

Synthesis of and Glass Surface Modification with Fluorinated Silane Coupling Agents with a Benzene Ring as a Spacer

Fluorinated silane coupling agents with a benzene ring as a spacer, CnF2n + 1-C6H4-SiX3 (n = 4, 6 and 8; X = Cl, OCH3 and NCO), were synthesized and their properties were examined to improve the surface modifying properties of the conventional fluorinated silane coupling agents. The silane coupling agents with a chloro- and methoxy-type hydrolytic groups were synthesized by the reactions of tetrachlorosilane and tetramethoxysilane with the intermediate, Rf-C6H4-MgBr, obtained through the Grignard reaction of the product of the reaction between p-dibromobenzene and perfluoroalkyl iodide in the presence of copper powder. The isocyanato-type silane coupling agents were obtained by allowing the chloro-type coupling agents synthesized to react with silver cyanate. All of the silane coupling agents thus synthesized were colorless transparent liquids. Evaluations were made on the glass surface modified with each of the coupling agents in terms of water contact angle, thermal stability, oxidation resistance, and acid resistance. The coupling agents had the properties similar to those of the conventional fluorinated silane coupling agents with the exception of thermal stability, showing that the newly synthesized agents were thermally stable up to about 300°C.

1,4-Addition reaction of ethyl bromodifluoroacetate to Michael acceptors in the presence of copper powder: Improvement of the reaction using TMEDA as an additive

Reaction of ethyl bromodifluoroacetate with a variety of Michael acceptors was tremendously improved by the addition of TMEDA. Using this additive, 1,4-adducts were formed exclusively, and any 1,2-adducts or radical adducts were not obtained. THF or other low boiling solvents can be used as a solvent. This simplifies the work-up of the reaction effectively.