Sequential Copper Research Articles

One-Step Construction of 1,3,4-Oxadiazoles with Anticancer Activity from Tertiary Amines via a Sequential Copper(I)-Catalyzed Oxidative Ugi/aza-Wittig Reaction.

An unparalleled copper(I)-catalyzed synthesis of 1,3,4-oxadiazoles from tertiary amines in one step has been described. The one-pot reactions involving (N-isocyanimine)triphenylphosphorane, tertiary amines, and carboxylic acids resulted in the formation of 1,3,4-oxadiazoles in moderate to good yields through a consecutive oxidative Ugi/aza-Wittig reaction, enabling the direct functionalization of sp3 C-H bonds adjacent to the nitrogen atom. This method offered several notable advantages, including ligands-free, exceptional productivity and a high functional group tolerance. The preliminary biological evaluation demonstrated that compound 4f inhibited hepatoma cells efficiently, suggesting potentially broad applications of the approach for synthesis and medicinal chemistry.

Mineralogical and hydraulic characterisation of historic flotation tailings

A composite flotation tailings sample from historic Medet tailings dam was characterised to understand occurrences of copper and hydraulic properties of the material and to determine if there is an economic benefit of its reprocessing using hydrometallurgical processes. Conventional ICP-OES multi-element scan and carbon and sulphur determination by Leco were followed by sequential copper assay and mineralogical analysis using the Tescan Integrated Mineral Analyser (TIMA) to identify the elemental composition, acid soluble copper and mineral abundance and liberation. The tailings sample contained 0.105% Cu, 0.41 % S and 0.05% C. The analysis of the gangue minerals showed that the bulk of the material is made up of plagioclase feldspar with moderate amounts of K-feldspars and small amounts of mica, chlorite and clay minerals. Copper minerals cuprite and chalcopyrite with minor amounts of covellite and bornite were observed in the mineralogical analysis of the sample by TIMA. Based on the sequential copper assays, it was estimated that approximately 59.8% of copper contained in the sample reports as acid soluble copper. To understand the flow behaviour in the material the main hydraulic properties like hydraulic conductivity and moisture retention capacity were determined.

Effects of Residual Xanthate on Flotation Efficiency of a Cu-Zn Sulfide Ore

Reuse of process water in the flotation of sulfide ores has crucial importance for environmental sustainability and improved process economy. However, the chemistry of process water may be a critical subject for the flotation efficiency as the dissolved ion concentration increases with water reuse. In this study, the effects of water reuse on the flotation efficiency of a Cu-Zn sulfide ore were investigated. The flotation flowsheet consists of a pre-flotation section to remove the naturally floatable talc particles, and sequential copper and zinc flotation sections. Calcium, sulfate, thiosulfate, and xanthate were found as major contaminating ionic species in the process water discharged from flotation circuits. The flotation tests with recirculated water from the zinc rougher tailing revealed that the presence of residual xanthate caused unintentional activation of copper minerals in the pre-float section. Copper recovery increased in the pre-flotation section and resulted in the loss of copper to the pre-float concentrate, which is considered as a tailing stream in the current flowsheet. Various types of activated carbon samples were tested to remove the residual xanthate from the tailing water. The carbon samples could be regenerated by heat treatment and reused for water treatment. Performance of the activated carbon samples was directly related to the pore size and surface area. Carbon-treated tailing water could be re-used in flotation without affecting the flotation performance.

Modular Synthesis of Benzocyclobutanes and Indolines Using Sequential Copper and Palladium Catalysis

Modular Synthesis of Benzocyclobutanes and Indolines Using Sequential Copper and Palladium Catalysis

Comparison of individual and sequential copper piping systems in an experimental artificial ground freezing model

Comparison of individual and sequential copper piping systems in an experimental artificial ground freezing model

Three-Component Cascade Bis-heteroannulation of Aryl or Vinyl Methylketoxime Acetates toward Thieno[3,2-c]isoquinolines.

A three-component cascade bis-heteroannulation reaction is described that provides access to a variety of benzo[4,5]thieno[3,2-c]isoquinoline and thieno[3,2-c]isoquinoline compounds from easily available methylketoximes, o-halobenzaldehydes, and elemental sulfur. Mechanistic studies reveal a two-step process involving a sequential copper and sulfur catalysis relay.

Bimetallic nanostructures on porous silicon with controllable surface plasmon resonance

The most intensive surface plasmon resonance (SPR) band is typical for the metallic particles of 10-150nm diameters. The SPR band of such nanoparticles is usually narrow and allows using just one laser (i.e. limited range of excitation wavelength) to achieve the maximal enhancement of electromagnetic field near metallic nanostructures caused by surface plasmon oscillations. It hinders usability of plasmonic nanostructures in some application including surface enhanced Raman scattering (SERS) spectroscopy. To overcome this hurdle enlarged metallic nanostructures are fabricated resulting in a broadening of the SPR band due to additional oscillation modes. However, the SPR bands of the enlarged particles are characterized by less intensity and weak enhancement at different wavelengths. In this paper, we proposed an alternative way for the SPR band broadening by use of bimetallic nanostructures on a sculptured template. Plasmonic substrates were fabricated by sequential copper electroplating and silver electroless deposition on porous silicon. Presented data implies that variation in morphology and ratio of the silver/copper nanostructures allow to control position of their SPR band from blue to near-infrared (IR) range. It is shown that SERS-spectroscopy with the fabricated nanostructures provide equal detection limits of rhodamine 6G under red and near-IR excitation wavelengths.

ChemInform Abstract: Concise Enantioselective Synthesis of Oxygenated Steroids via Sequential Copper(II)‐Catalyzed Michael Addition/Intramolecular Aldol Cyclization Reactions.

AbstractDepending on the base used for induction of the aldol cascade reaction either natural or non‐natural steroid skeleton are selectively accessed.

Concise Enantioselective Synthesis of Oxygenated Steroids via Sequential Copper(II)-Catalyzed Michael Addition/Intramolecular Aldol Cyclization Reactions.

A new scalable enantioselective approach to functionalized oxygenated steroids is described. This strategy is based on chiral bis(oxazoline) copper(II) complex-catalyzed enantioselective and diastereoselective Michael reactions of cyclic ketoesters and enones to install vicinal quaternary and tertiary stereocenters. In addition, the utility of copper(II) salts as highly active catalysts for the Michael reactions of traditionally unreactive β,β'-enones and substituted β,β'-ketoesters that results in unprecedented Michael adducts containing vicinal all-carbon quaternary centers is also demonstrated. The Michael adducts subsequently undergo base-promoted diastereoselective aldol cascade reactions resulting in the natural or unnatural steroid skeletons. The experimental and computational studies suggest that the torsional strain effects arising from the presence of the Δ(5)-unsaturation are key controlling elements for the formation of the natural cardenolide scaffold. The described method enables expedient generation of polycyclic molecules including modified steroidal scaffolds as well as challenging-to-synthesize Hajos-Parrish and Wieland-Miescher ketones.

Synthesis of double-clickable functionalised graphene oxide for biological applications.

Azide- and alkyne-double functionalised graphene oxide (Click(2) GO) was synthesised and characterised with attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), thermogravimetric analysis (TGA) and Raman spectroscopy. Fourteen-percentage increase in azide content was found, after pre-treatment of GO with meta-chloroperoxybenzoic acid (mCPBA), determined with elemental analysis. No effect on A549 cell viability was found, up to 100 μg mL(-1) and 72 h of incubation, determined with the modified lactate dehydrogenase (mLDH) assay. Two sequential copper(i) catalysed azide-alkyne cycloaddition (CuAAC) reactions were performed to conjugate the propargyl-modified blood-brain barrier targeting peptide Angiopep-2, and a bis-azide polyethylene glycol (MW = 3500), to the Click(2) GO. The final conjugate was characterised with ATR-FTIR and TGA.

Sequential and parallel dual labeling of nanoparticles using click chemistry

Bioorthogonal ‘click’ reactions have recently emerged as promising tools for chemistry and biological applications. By using a combination of two different ‘click’ reactions, ‘double-click’ strategies have been developed to attach multiple labels onto biomacromolecules. These strategies require multi-step modifications of the biomacromolecules that can lead to heterogeneity in the final conjugates. Herein, we report the synthesis and characterization of a set of three trifunctional linkers. The linkers having alkyne and cyclooctyne moieties that are capable of participating in sequential copper(I)-catalyzed and copper-free cycloaddition reactions with azides. We have also prepared a linker comprised of an alkyne and a 1,2,4,5-terazine moiety that allows for simultaneous cycloaddition reactions with azides and trans-cyclooctenes, respectively. These linkers can be attached to synthetic or biological macromolecules to create a platform capable of sequential or parallel ‘double-click’ labeling in biological systems. We show this potential using a generation 5 (G5) polyamidoamine (PAMAM) dendrimer in combination with the clickable linkers. The dendrimers were successfully modified with these linkers and we demonstrate both sequential and parallel ‘double-click’ labeling with fluorescent reporters. We anticipate that these linkers will have a variety of application including molecular imaging and monitoring of macromolecule interactions in biological systems.

Synthesis and characterization of perylene diimide based molecular multilayers using CuAAC: towards panchromatic assemblies

Three perylene diimides (PDI) were synthesized with propargyl groups at the diimide positions to enable the fabrication of molecular multilayer thin films via sequential copper(I) catalyzed azide-alkyne cycloaddition (CuAAC) coupling reactions in a layer-by-layer (LbL) fashion. The new PDIs with phenoxy (PhO-PDI), dodecylthiol (Thiol-PDI), and pyrrolidine (Pyrr-PDI) substituents in bay positions have optical absorption spectra that span a large portion of the visible region. Multilayer growth on 11-azidoundecylsiloxane coated silica glass and indium tin oxide (ITO) surfaces was demonstrated up to 10 bilayers of each PDI with 1,3,5-tris(azidomethyl)-benzene (N3Mest) via optical and infrared spectroscopy. Polarized UV-visible absorption measurements showed a strong dependence on the orientation of the film in the light path and was consistent with a preferential orientation of the PDI molecules in the film at 40–42° with respect to the substrate surface. Grazing-angle attenuated total reflectance (GATR) infrared spectra of the films show an increase in content of unreacted azides during multilayer growth from N3Mest as a result of the smaller molecular footprint as compared to the PDI components. Electrochemical scans of the multilayer films grown on ITO exhibited reversible two-electron reduction waves for the PDIs with linear increases in charge with bilayer growth. The electrochemically derived surface coverages of PDIs averaged 1.2–1.3 × 1014 molecules per cm2 for each layer added to the multilayer films. The flexibility of the CuAAC based LbL assembly methodology is highlighted by the assembly of a mixed multilayer film containing five layers of each PDI, resulting in a panchromatic film that is a summation of individual chromophores.

A Light and pH Dual-Stimuli-Responsive Block Copolymer Synthesized by Copper(0)-Mediated Living Radical Polymerization: Solvatochromic, Isomerization, and “Schizophrenic” Behaviors

A "schizophrenic" block copolymer (poly[1'-(2-methacryloxyethyl)-3',3'-dimethyl-6-nitrospiro-(2H-1-benzopyran-2,2'-indoline)]-b-poly(acrylic acid) (PSPMA-b-PAA)) was synthesized by sequential copper(0)-mediated living radical polymerization (Cu(0)-mediated LRP) at 30 °C in an oxygen-tolerant system followed by hydrolysis of the resulting polymer. The solvatechromic behaviors of the PSPMA10-b-poly(t-butyl acrylate)40 (PSPMA10-b-PtBA40) and PSPMA10-b-PAA40 block copolymers in organic solvents were investigated by UV-vis spectroscopy. The PSPMA10-b-PtBA40 stabilizes the nonpolar photoisomer and is not sensitive to the polarity of the solvent, while the PSPMA10-b-PAA40 stabilizes the planar zwitterionic form without irradiation. Furthermore, light-induced isomerization of spiropyran (Sp) moieties from Sp to merocyanine (Mc) was demonstrated. Finally, the "schizophrenic" micellization behavior of as-prepared copolymer in aqueous solution regulated by light and pH stimuli was vividly demonstrated, and the reversibility of micellization processes performed in this study was also examined. The large compound micelles can bring out a gradually extended and even transformed conformation with increasing deprotonation degree at pH > pKa.

W-Band Micro-Fabricated Coaxially-Fed Frequency Scanned Slot Arrays

In this communication we describe a frequency scanning slot array in μcoaxial technology operating from 87-102 GHz. The array achieves a 30° scanning angle over a 15 GHz bandwidth. The device is fabricated using the PolyStrata sequential copper deposition process, which guarantees low loss and small size. A double-array prototype, with a gain of 14 dB at 94 GHz, is fabricated and tested.

ChemInform Abstract: Asymmetric Synthesis of Dihydropyranones from Ynones by Sequential Copper(I)‐Catalyzed Direct Aldol and Silver(I)‐Catalyzed Oxy‐Michael Reactions.

AbstractA facile and general method for the title synthesis is developed.

Micro-Fabricated 130–180 GHz Frequency Scanning Waveguide Arrays

This paper describes frequency scanning slot arrays operating from 130 to 180 GHz. The arrays are micro-fabricated using the PolyStrata sequential copper deposition process. Measured reflection coefficient and radiation patterns agree with HFSS full-wave simulations. The voltage standing wave ratio is less than 1.75:1 over the entire frequency range, and the measured scanning is 1.04°/ GHz from 130 to 150 GHz and 32.5° over the full frequency range. The measured gain is 15.5 dBi for a 10-element array at 150 GHz and 18.9 dBi for a 20-element array at 150 GHz with about 3 dB of variation over the scan range.

Asymmetric Synthesis of Dihydropyranones from Ynones by Sequential Copper(I)‐Catalyzed Direct Aldol and Silver(I)‐Catalyzed Oxy‐Michael Reactions

Ynones as diene surrogates: the asymmetric synthesis of enantiomerically enriched substituted dihydropyranones is described. The products are obtained in two steps by a copper(I)-catalyzed direct aldol reaction of ynones followed by a silver-catalyzed oxy-Michael reaction. This easy method is compatible with both aromatic and aliphatic substrates, and provides excellent chemoselectivity under mild reaction conditions.

Asymmetric Synthesis of Dihydropyranones from Ynones by Sequential Copper(I)‐Catalyzed Direct Aldol and Silver(I)‐Catalyzed Oxy‐Michael Reactions

Asymmetric Synthesis of Dihydropyranones from Ynones by Sequential Copper(I)‐Catalyzed Direct Aldol and Silver(I)‐Catalyzed Oxy‐Michael Reactions

Modular synthesis of mono, di, and tri-1,4-disubstituted-1,2,3-triazoles through copper-mediated alkyne–azide cycloaddition

The synthesis of 1,2,3-triazoles was developed employing sequential copper azide–alkyne cycloaddition, tosylation, sodium azide, and copper azide–alkyne steps. This approach allowed the synthesis of two and three 1,2,3-triazole rings. A preliminary study to gain further insight into the reaction was performed using in situ ReactIR technology.

Synthesis of Unsymmetrical 1,1′-Disubstituted Bis(1,2,3-triazole)s Using Monosilylbutadiynes

Bis(1,2,3-triazole)s have attracted recent interest as coordinating ligands for transition metals. Here we report a rapid, modular method for the synthesis of 1,1'-disubstituted-4,4'-linked unsymmetrical bis(1,2,3-triazole)s. The method employs sequential copper catalyzed azide-alkyne cycloaddition and deprotection steps on a monosilylbutadiyne. TMS (trimethylsilyl) and TIPS (triisopropylsilyl) were both investigated with TIPS being the preferred protecting group due to increased stability. The reactions were amenable to one-pot synthesis, and an optimized one-pot, three-step procedure was developed.