An Efficient Recyclable Polymer Supported Copper(II) Catalyst for C–N Bond Formation by <Emphasis Type=Italic>N</Emphasis>-Arylation

Abstract  

Polymer supported Cu(II) catalyst was prepared, characterized and employed for the N-arylation and amination reaction of N–H heterocycles with aryl halides as well as arylboronic acids to afford the corresponding coupled products in good to excellent yields. This catalyst can be used several times with consistent catalytic activity.     

Copper and Iron Determination with [<Emphasis Type=Italic>N</Emphasis>,<Emphasis Type=Italic>N</Emphasis>′-Bis(salicylidene)-2,2′-dimethyl-1,3-propanediaminato] in Edible Oils Without Digestion

A new method for the determination of copper(II) and iron(III) in liquid edible oils which does not require a digestion step was developed. The suggested method involves extraction of metals with [N,N′-bis(salicylidene)-2,2′-dimethyl-1,3-propanediaminato] (LDM) followed by flame atomic absorption spectrometry measurement. As a first step, metal complexes of copper(II) and iron(III) ions with LDM were investigated spectrophotometrically. After the analytical properties and experimental conditions of the complexation had been determined, these findings were used to determine the extraction period as a second step. Experimental conditions were optimized using a central composite design. Optimum conditions for Cu(II) and Fe(III) extractions from oil were found: the ratios of the volume of Schiff base solution used to the mass of oil (V _LDM/m _oil; mL g⁻¹) were 0.76 and 1.19 mL g⁻¹, the stirring times were 73 and 67 min, and the temperatures were 31 and 28 °C, respectively. The developed extraction and determination method was tested on certified reference materials; the recovery percentages were found to be 99.4 ± 2.8 and 100.2 ± 5.6 for Cu(II) and Fe(III), respectively. The suggested method was performed on real samples such as olive oil, sunflower oil, corn oil, canola oil and recovery values between 97.2–102.1 for Cu(II) and 94.5–98.6 for Fe(III) were determined. It was concluded that the developed method has some advantages over the common traditional method including rapidity, sensitivity, accuracy, reduced risk and cost.     

On the Chemical Origin of the Gap Bowing in (GaAs)<Subscript>1−<Emphasis Type=Italic>x</Emphasis></Subscript>Ge<Subscript>2<Emphasis Type=Italic>x</Emphasis></Subscript> Alloys: A Combined DFT–QS<Emphasis Type=Italic>GW</Emphasis> Study

Motivated by the research and analysis of new materials for photovoltaics and by the possibility of tailoring their optical properties for improved solar energy conversion, we have focused our attention on the (GaAs)_{1− x} Ge_2x series of alloys. We have investigated the structural properties of some (GaAs)_{1− x} Ge_2x compounds within the local-density approximation to density-functional theory, and their optical properties within the Quasiparticle Self-consistent GW approximation. The QSGW results confirm the experimental evidence of asymmetric bandgap bowing. It is explained in terms of violations of the octet rule, as well as in terms of the order–disorder phase transition.     

Improvement of passivity of Fe–<Emphasis Type=Italic>x</Emphasis>Cr Alloys (<Emphasis Type=Italic>x</Emphasis> < 10%) by cycling through the reactivation potential

Classically, 13% Cr is required for stable passivity of a Fe–Cr alloy in acidic and neutral solutions not containing inhibitors. Some authors (Mansfeld, Fujimoto) have published potential cycling procedures that generate thick Cr-rich films. In this work, a similar technique, but with a far smaller potential cycle, was used to enrich a surface layer in chromium, thereby increasing corrosion-resistance in otherwise non-passivating steels. This was achieved by potential stepping across the iron reactivation potential, firstly forming passive iron(III) oxide, then reducing it to soluble iron(II) ions, while ensuring the passivity of chromium. The use of potential stepping was found to result in a more robust film than that formed through a single continuous passivation step.     

Fatty Acids Profile of <Emphasis Type=Italic>Alphitonia neocaledonica</Emphasis> and <Emphasis Type=Italic>Grevillea exul</Emphasis> var. <Emphasis Type=Italic>rubiginosa</Emphasis> Seed Oils,Occurrence of an ω5 Series

This is the first report of the chemical composition of Alphitonia neocaledonica (AN) and Grevillea exul var. rubiginosa (GER) seed oils. Using retention indices and gas chromatography–mass spectrometry, an unusual family of unsaturated ω5-fatty acids has been identified. These include 14:1, 16:1, 18:1 and 20:1. Identification of the unsaturated fatty acids was confirmed by formation of DMOX derivatives which gave characteristic and easily interpreted mass spectra. DMDS adducts were used to identify the positions of double bonds in the monounsaturated fatty acids. The major fatty acids were 16:1ω5 (45.6%) and 18:1ω9 (20.9%) for GER and 18:2 (23.6%) and 18:3 (20.4%) for AN. The total ω5-monoenes were 63.4 and 21.5% for GER and AN, respectively. The seed oils of AN and GER can be considered as a good source of ω5-monoenes, especially for GER. The occurrence of the ω5-monoenes in Alphitonia neocaledonica can at present be considered as an exception within the Rhamnaceae family. Except for Ziziphus jujuba var. inermis, no species of this family has been described with a broad profile of ω5-monoene fatty acids.     

A Review of the Application and Pharmacological Properties of <Emphasis Type=Italic>α</Emphasis>-Bisabolol and <Emphasis Type=Italic>α</Emphasis>-Bisabolol-Rich Oils

α-Bisabolol is a naturally occurring sesquiterpene alcohol which was first isolated from Matricaria chamomilla (Asteraceae) in the twentieth century and has since been identified in other aromatic plants such as Eremanthus erythropappus, Smyrniopsis aucheri and Vanillosmopsis species. Recently, α-bisabolol was identified as a major constituent of Salvia runcinata essential oil, a plant indigenous to South Africa. The use of α-bisabolol or bisabolol-rich oil as an anti-inflammatory agent is ubiquitous. This compound also exhibits several other pharmacological properties such as analgesic, antibiotic and anticancer activities. Mutagenicity and genotoxicity of bisabolol have also been investigated. Due to the low toxicity associated with bisabolol the Food and Drug Administration (FDA) has granted this constituent with Generally Regarded as Safe (GRAS) status which has promoted its use as an active ingredient in several commercial products. This review aims to summarise the role of α-bisabolol in pharmacological and/or physiological processes and to discuss some of the possible mechanisms of action of this commercially important molecule.     

Oxygen nonstoichiometry of layered oxides <Emphasis Type=Italic>Ln</Emphasis>BaCuFeO<Subscript>5 + δ</Subscript> (<Emphasis Type=Italic>Ln</Emphasis> = La,Pr)

The oxygen exchange between powders of the layered oxides LnBaCuFeO_{5 + δ} (Ln = La, Pr) and the environment and the oxygen nonstoichiometry index δ of these oxides have been investigated using solidelectrolyte coulometry in the temperature range 20–800°C and at oxygen partial pressures in the range 3–346 Pa. It has been found that the evolution (absorption) of oxygen by the powdered samples proceeds in two stages and that the transition between the stages corresponds to a particular value of the degree of filling of the layers with oxygen (δ ≈ 0.25 for Ln = La and δ ≈ 0.125 for Ln = Pr). The conclusion has been drawn from analyzing the results obtained that, in the layers -LnO_δ-of the crystal structure of the LnBaCuFeO_{5 + δ} phases, oxygen undergoes a sequential ordering and that, in these layers, oxygen can exist in two forms: ordered and disordered. The latter form represents weakly bound oxygen which can be easily exchanged between the samples and the environment.     

Optimization of the fermentation conditions and partial characterization for acido-thermophilic <Emphasis Type=Italic>α</Emphasis>-amylase from <Emphasis Type=Italic>Aspergillus niger</Emphasis> NCIM 548

A high performance thermostable α-amylase at low pH values has been synthesized. Sugarcane bagasse was hydrolyzed in a dilute acid solution and utilized as carbon source for the growth of Aspergillus niger strain NCIM 548. Glucose, xylose and arabinose with the ratio of 1.0: 0.9: 0.3 (w/w/w) were detected in the hydrolyzate by HPLC analysis. Optimization of the fermentation conditions for α-amylase production was performed by varying four influential parameters such as Sugarcane bagasse hydrolyzate (SBH), NH₄Cl, pH and incubation time using a central composite design (CCD) under response surface methodology (RSM). The optimum values of SBH, NH₄Cl, pH and incubation time were 20.49, 2.34 g/l, 5.65 and 76.67 h, respectively. The acido-thermophilic enzyme showed maximum stability at 70°C and pH value of 4. The rate constant, K _m and maximum reaction rate, V _max were 18.79 g/l and 15.85 g/l·min, respectively.     

Production of an antimicrobial compound by <Emphasis Type=Italic>Bacillus subtilis</Emphasis> LS 1–2 using a citrus-processing byproduct

The aim of this study was to investigate the antimicrobial activity of Bacillus subtilis LS 1–2 grown on citrus juice waste (CJW). Citrus-juice waste (CJW) was obtained from the residue of squeezed citrus fruits. To use CJW as a raw material for the growth of B. sutilitis, a citrus-juice medium (CJM) was prepared by treating CJW with Ca(OH)₂. No antimicrobial activity was observed either in the culture broth of Luria Broth medium or in CJM itself. The maximum antimicrobial activity was obtained after 24 hr of cultivation (culture) of Bacillus sutilitis LS 1–2 in CJM. The culture supernatant exhibited inhibitory activity against E. coli O-157 (140 AU/mL), Staphylococcus aureus (180 AU/mL), and Candida albicans (260 AU/mL), respectively. Bacillus subtilus LS 1–2 also produced protease (3,600 U/ml) and amylase (290 U/ml) in CJM. Antimicrobial activity of the culture broth was stable for 1 hr at 100 °C, pH 2–10, and bile acid (concentration needs, 1 mM TDOC and 0.27 mM DOCmM), respectively. These results indicate the potential of CJW as a novel bioresource and the scope of probiotic applications of Bacillus subtilis LS 1–2 in various industrial applications.     

Improvement of ATP regeneration efficiency and operation stability in porcine interferon-<Emphasis Type=Italic>α</Emphasis> production by <Emphasis Type=Italic>Pichia pastoris</Emphasis> under lower induction temperature

The performance of traditional heterologous protein production by Pichia pastoris with methanol induction at 30 °C is poor, characterized by low ATP regeneration rate and weak operation stability. A low temperature induction strategy at 20 °C was thus adopted for efficient porcine interferon-α production in a 10 L fermentor. With the strategy, maximal methanol tolerance level could reach about 40 g/L to effectively deal with methanol concentration variations, so that the complicated on-line methanol measurement system could be eliminated. Moreover, metabolic analysis based on multiple state-variables measurements indicated that pIFN-α antiviral activity enhancement profited from the formation of an efficient ATP regeneration system at 20 °C induction. Compared to the induction strategy at 30 °C, the proposed strategy increased the ATP regeneration rate by 49–66%, the maximal pIFN-α antiviral activity was enhanced about 20-fold and reached a higher level of 1.5×10⁶ IU/mL.     

Relaxation phenomena in (As<Subscript>2</Subscript>Se<Subscript>3</Subscript>)<Subscript>100 − <Emphasis Type=Italic>x</Emphasis></Subscript>Bi<Subscript><Emphasis Type=Italic>x</Emphasis></Subscript> layers

The physical parameters, which describe the relaxation phenomena occurring in both the bulk and contact regions of the systems under investigation, have been calculated using experimental curves of isothermal relaxation of polarization current in thin films of modified (As₂Se₃)_{100 − x} Bi _x . The relation between the change in the internal structure of the studied materials and the processes of charge transfer and charge accumulation has been revealed. The results obtained have been discussed with invoking the relay-race mechanism of charge transfer.     

Biomimetic Cleavage of Aryl–Nitrogen Bonds in <Emphasis Type="Italic">N</Emphasis>-Arylazoles Catalyzed by Metalloporphyrins

The cleavage of C–N single bonds of N-containing compounds provides either an excellent nitrogen source or an excellent carbon source. In this study, an efficient metalloporphyrins/H₂O₂ cleavage of C–N bonds of arylpyrazoles was investigated. The effects of different factors, including different catalysts, catalyst dosages, H₂O₂ dosages, reaction temperature and reaction time were studied. The experimental results showed that the optimal catalyst was FeTPPCl, and the yield of pyrazole derivatives could reach up to 12.3%, which was fourfold higher than hemin catalyzed reaction and closed to ceric ammonium nitrate catalyzed reaction, respectively. Compared with transition-metal-catalyzed and strong-oxidization cleavage of C–N bonds, this protocol is characterized by environmentally-friendly, stable, mild reaction conditions and simplified operation procedures.

Graphical Abstract

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Bulky <Emphasis Type="Italic">N</Emphasis>-acyl-pyridylbenzamidine Ligands for Palladium Catalyzed Suzuki–Miyaura Reaction

Abstract  

In this letter, a series of bulky N-acyl-pyridylbenzamidine ligands were synthesized and characterized. Under the optimized reaction conditions, these bulky ligands were applied to catalyze Suzuki–Miyaura reactions of various aryl bromides and chlorides. The desired biaryl products were obtained in good to high yields.