Correction: DCID-mediated esterification of carboxylic acids with alcohols under mild conditions.

[This corrects the article DOI: 10.1039/D3RA04048H.].

Long-time irradiation effect on corrosion behavior of aluminum alloy in pool water of low-power research reactor.

This study conducted an evaluation of the corrosion behavior of an aluminum alloy utilized in the Isfahan Miniature Neutron Source Reactor (MNSR). The component analyzed, dry channel (DC), had been exposed to radiation for 12 years in a water environment within the reactor pool since its installation. To determine the effect of radiation on the corrosion of the LT-21 aluminum alloy used in the DC, different parts of the pipe were sampled and various tests were performed. These tests included mechanical strengths (impact, and micro-hardening), XRD, TEM, SEM-EDS, and potentiodynamic polarization (PDP). The parameters measured included corrosion potential, corrosion rate, changes in microscopic structure, and mechanical properties of the aluminum alloy along the entire length of the DC. The neutron and gamma dose distribution along the height of the DC, which was 540 cm, was calculated to determine the correlation between the dose distribution and observed corrosion. The study found that the corrosion mechanisms were complex and resulted from the simultaneous presence of the DC in the pool water and radiation from the reactor core. The observed results are presented and discussed in this study.

DCID-mediated esterification of carboxylic acids with alcohols under mild conditions.

DCID (Dichloroimidazolidinedione) 2 is used as a novel coupling reagent for the esterification of carboxylic acids with alcohols at room temperature. The reaction represents the first DCID-promoted esterification under mild conditions with good to excellent yields. Reactions can proceed smoothly with those bearing electron-withdrawing and donating group(s) on the carboxylic acids and benzyl alcohols at ambient temperature. Furthermore, we proposed a plausible mechanism and confirmed it by isolating and characterizing intermediates 3a and 7. The structures of the synthesized compounds were confirmed by comparison of melting points and NMR spectra.

Synthesis and characterization of epoxide impurities of abiraterone acetate.

Abiraterone acetate is an antiandrogen steroidal drug that is used to treat patients with metastatic prostate cancer. During the process development of abiraterone acetate, two process α and ß-epoxy abiraterone acetate related impurities (2 and 3) were observed along with the final API. In the present work we describe the synthesis of these two known impurities using abiraterone acetate in the presence of hydrogen peroxide and acetic acid as oxidizing agent. The structure of these impurities fully characterized by NMR, Mass, CHN and HPLC analysis.

Novel Method for the Isolation of Proteins and Small Target Molecules from Biological and Aqueous Media by Salt-Assisted Phase Transformation of Their PEGylated Recognition Counterparts.

An efficient and simple method for the application of PEGylated affinity ligands in precipitative isolation of protein target molecules (TMs) from a biological fluid such as blood serum or small target molecules from an aqueous medium is presented for the first time. This approach is based on the high binding specificity of PEGylated recognition molecules (PEG-RMs) to their TMs and the unique physicochemical properties of PEG that result in their salt-assisted phase transformation. Addition of PEG-RM to blood serum results in the formation of an RM-specific macromolecular complex (PEG-RM + TM → PEG-RM.TM) that undergoes facile salt-assisted phase transformation to a separable semisolid with ammonium sulfate. PEG-RM.TM is then dissociated into its components by pH reduction or an increase of ionic strength (PEG-RM.TM → PEG-RM + TM). PEG-RM is salted out to afford pure TM in solution. The same phenomenon is observed when RM or TM are small molecules. The general applicability of the method was validated by PEGylation of two proteins (protein A, sheep antihuman IgG) and a small molecule (salicylic acid) used as model RMs for the isolation of Igs, IgG, and serum albumin from blood serum. The isolated protein TMs were shown to be pure and aggregate-free by gel electrophoresis and dynamic light scattering (DLS). IgG isolated by this method was further characterized by peptide mass fingerprinting. PEGylated protein A was used to demonstrate the recyclability and scale-up potential of PEG-RM. IgG isolated by this method from blood serum of a hepatitis C-vaccinated individual was tested for its binding to sheep antihuman IgG by UV spectroscopy, and its bioactivity was ascertained by comparison of its enzyme-linked immunosorbent assay (ELISA) result to that of a blood sample from the same individual. Reciprocity of RM and TM was ascertained using PEGylated salicylic acid to obtain pure serum albumin, and PEGylated serum albumin was utilized for near-exclusive isolation of one drug from an aqueous equimolar mixture of three drugs (salicylic acid, 91%; capecitabine, 6%; and deferiprone, 3%). Advantages of this approach, including target specificity and general applicability and celerity, over other affinity methods for the isolation of proteins are discussed at a molecular level.

An alginate-PHMB-AgNPs based wound dressing polyamide nanocomposite with improved antibacterial and hemostatic properties.

Wound dressing should be impenetrable against microorganisms and it should keep the wound wet. Gauze and polyamide (PA) substrate were treated with various concentrations of AgNPs (25, 50, 75, and 100 ppm), PHMB (0.2, 0.4, 0.6, 0.8, and 1% w/v), and constant concentration of alginate (0.5% W/V) using a simple dipping method. Prepared samples were characterized by various techniques including Fourier transform infrared spectroscopy and scanning electron microscopy. The results indicated that the particles were successfully applied onto both substrates with an average diameter of particle size of 78 nm on gauze and 172 nm on the PA substrate surface (based on 50 nanoparticles). Antibacterial activity of the prepared nanocomposite against Staphylococcus aureus (gram-positive) bacteria on PA substrate and gauze were evaluated using the disc diffusion method. The results indicated that the prepared nanocomposites offer favorable antibacterial properties and bacteria would not grow in culture media. The water uptake capacity test of the treated samples was assessed and the data demonstrated that the water absorption rate significantly increases on both treated substrates (gauze and PA substrate) due to the presence of alginate polymer. Also, observing the results of the coagulation test showed that treated samples caused blood clots on the dressing. This is due to the presence of alginate polymer. The present work demonstrates that the prepared samples offer excellent antibacterial properties and good water uptake capacity that capable of being a potential candidate for wound dressings. Due to the results, the produced PA substrate could be an appropriate replacement for the cotton gauze as a wound dressing.

Direct synthesis of amides and imines by dehydrogenative homo or cross-coupling of amines and alcohols catalyzed by Cu-MOF.

Oxidative dehydrogenative homo-coupling of amines to imines and cross-coupling of amines with alcohols to amides was achieved with high to moderate yields at room temperature in THF using Cu-MOF as an efficient and recyclable heterogeneous catalyst under mild conditions. Different primary benzyl amines and alcohols could be utilized for the synthesis of a wide variety of amides and imines. The Cu-MOF catalyst could be recycled and reused four times without loss of catalytic activity.

Ethanol-Drop Grinding Approach: Cadmium Oxide Nanoparticles Catalyzed the Synthesis of [1,3]Dioxolo[g][1]benzopyran-6-carboxylic Acids and Pyrido[d]pyrimidine-7-carboxylic Acids.

AIM AND OBJECTIVE: In the last decades, it has extensively been verified that nanostructured transition metal oxides emerge as inexpensive, available and extremely efficient heterogeneous catalysts in chemical transformations. The high electrical conductivity, high carrier concentration, and improved reactivity in cadmium oxide nanoparticles (CdO NPs) make it as a potential candidate for applications in the fields of nanocatalysis. [1]Benzopyran and pyridopyrimidine derivatives compose major classes of heterocyclic compounds, which have a wide spectrum of biological activities. MATERIALS AND METHODS: In the present work, we report a facile and highly effective synthesis of 8- aryl-8H-[1,3]dioxolo[4,5-g][1]benzopyran-6-carboxylic acids and 1,3-dimethyl-2,4-dioxo-5- phenyl-1,2,3,4,5,8-hexahydropyrido[2,3-d]pyrimidine-7-carboxylic acids via CdO NPs catalyzed cyclo condensation reaction of 4-substituted phenylmethylidenepyruvic acids with 3,4- methylenedioxyphenol or 6-amino-1,3-dimethyluracil, which was accomplished under ethanoldrop grinding at room temperature. The described catalyst was prepared successfully by a simple precipitation method and characterized by the Fourier transformed infrared absorption (FT-IR) spectroscopy, X-Ray diffraction (XRD) analytical technique, and scanning electron microscopy (SEM). RESULTS: A number of [1,3]dioxolo[g][1]benzopyran-6-carboxylic acids and pyrido[d]pyrimidine- 7-carboxylic acids were effectively synthesized in high yields (96-98%) within short reaction times (10-15 min). All synthesized compounds were well-characterized by IR, 1H and 13C NMR spectroscopy, and also by elemental analyses. CONCLUSION: In summary, we have developed a very simple and impressive procedure for the synthesis of 8-aryl-8H-[1,3]dioxolo[4,5-g][1]benzopyran-6-carboxylic acids and 1,3-dimethyl- 2,4-dioxo-5-phenyl-1,2,3,4,5,8-hexahydropyrido[2,3-d]pyrimidine-7-carboxylic acids as biologically interesting structures in the presence of CdO NPs as an efficient recyclable heterogeneous catalyst. The remarkable advantages for the offered protocol compared with traditional methods are short reaction time, good yields of the products, and the ease of operation with simple work-up procedure.

Anion recognition by urea metal-organic frameworks: remarkable sensitivity for arsenate and fluoride ions.

Functionalized metal-organic frameworks (F-MOFs) are known as a promising chemical sensors since they have specific merits like fixed functionalized ligands projecting into the pores which can be utilized to enhance sensitivity and selectivity. Due to the important role of anions in biological process and environmental systems, there is an increasing interest in synthesis and design of new receptors for anions. Urea groups can operate as a hydrogen bond donating site with hydrogen bond acceptor molecules. Strong and directional hydrogen-bonding between the positive urea groups and anions could reduce vibrational quenching and enhance the fluorescence intensity. In this study, two luminescent porous urea decorated MOFs have been successfully assembled and structurally characterized. Luminescence studies of these MOFs toward anions revealed that these F-MOFs exhibit high sensitivity and selectivity toward H2AsO4- and F- anions as two major ground water pollutants. Moreover, the proposed materials have been applied for the removal of arsenate and nitrate in contaminant well water samples. Graphical abstract.

Molecular Engineering of Simple Metal-Free Organic Dyes Derived from Triphenylamine for Dye-Sensitized Solar Cell Applications.

Two new metal-free organic sensitizers, L156 and L224, were designed, synthesized, and characterized for application in dye-sensitized solar cells (DSCs). The structures of the dyes contain a triphenylamine (TPA) segment and 4-(benzo[c][1,2,5]thiadiazol-4-yl)benzoic acid as electron-rich and -deficient moieties, respectively. Two different π bridges, thiophene and 4,8-bis(4-hexylphenyl)benzo[1,2-b:4,5-b']dithiophene, were used for L156 and L224, respectively. The influence of iodide/triiodide, [Co(bpy)3 ]2+/3+ (bpy=2,2'-bipyridine), and [Cu(tmby)2 ]2+/+ (tmby=4,4',6,6'-tetramethyl-2,2'-bipyridine) complexes as redox electrolytes and 18 NR-T and 30 NR-D transparent TiO2 films on the DSC device performance was investigated. The L156-based DSC with [Cu(tmby)2 ]2+/+ complexes as the redox electrolyte resulted in the best performance of 9.26 % and a remarkably high open-circuit voltage value of 1.1 V (1.096 V), with a short-circuit current of 12.2 mA cm-2 and a fill factor of 0.692, by using 30 NR-D TiO2 films. An efficiency of up to 21.9 % was achieved under a 1000 lx indoor light source, which proved that dye L156 was also an excellent candidate for indoor applications. The maximal monochromatic incident-photon-to-current conversion efficiency of L156-30 NR-D reached up to 70 %.

Calendula officinalis extract/PCL/Zein/Gum arabic nanofibrous bio-composite scaffolds via suspension, two-nozzle and multilayer electrospinning for skin tissue engineering.

This work investigates the incorporation of the Calendula officinalis (C. officinalis) extract in electrospun fiber scaffolds composed of poly (ε-caprolactone) (PCL), Zein and gum arabic (GA). Three methods of electrospinning were used: suspension electrospinning, in which C. officinalis extract was directly added in the PCL/Zein/GA solution, two-nozzle electrospinning, in which hybrid PCL/Zein/GA and PCL/C. officinalis nanofibrous layers were prepared by two syringes and multilayer electrospinning, in which layer-by-layer scaffold was fabricated of PCL/Zein/GA and PCL/C.officinalis nanofibrous mats. SEM micrographs of fabricated scaffolds depicted beadless nanofibers with interconnected pores. The PCL/Zein/GA/C.officinalis scaffolds possess good hydrophilicity with high porosity (about 80%) and also exhibited desirable mechanical properties and suitable degradability for skin tissue engineering. Multilayer produced scaffold showed more tensile strength than other C. officinalis-loaded PCL/Zein/GA scaffolds. In vitro C.officinalis release exposed gradual and sustained release behavior for fabricated scaffold by multilayer electrospinning. The results of MTT analysis and SEM images confirmed that PCL/Zein/GA/C.officinalis nanocomposite scaffold had favorable proliferation and adhesion against fibroblast cell as compared to PCL/Zein/GA scaffold for regenerating skin. The C. officinalis-loaded PCL/Zein/GA scaffold indicated better antibacterial properties and biocompatibility than PCL/Zein/GA scaffold. The results confirmed that C. officinalis-loaded PCL/Zein/GA nanocomposite scaffolds would be desirable biomaterial for skin regeneration.

One-pot synthesis of amides via the oxidative amidation of aldehydes and amines catalyzed by a copper-MOF.

An efficient method for the oxidative amidation of aldehydes with primary aromatic and aliphatic amines has been developed for the synthesis of a wide variety of amides using inexpensive Cu2(BDC)2DABCO (Cu-metal-organic framework [MOF]) as a recyclable heterogeneous catalyst, and N-chlorosuccinimide and aqueous tert-butyl hydroperoxide as oxidants in acetonitrile. This amidation reaction is operationally straightforward and provides secondary amides in good yields in most cases, utilizing inexpensive and readily available reagents under mild conditions.

Fabrication and characterization of PCL/zein/gum arabic electrospun nanocomposite scaffold for skin tissue engineering.

The main role of tissue engineering is to produce the artificial tissue for replacing the biological functions in tissue regeneration and wounds healing. The purpose of this research was to produce porous nanofiber scaffold by electrospinning to compensate deep skin damages. In order to simulate a scaffold similar to the natural extracellular matrix of the skin, a mixture of corn protein (Zein), polycaprolactone (PCL) and gum arabic (GA) was used with different concentrations and ratios. Zein and GA polymers were used as a protein and polysaccharide component of the scaffold and PCL polymer for elasticity, strength and time setting of scaffold degradability. For investigating morphology and scaffold compounds, scanning electron microscopy (SEM) and Fourier transform infrared techniques were used. Furthermore, mechanical properties, porosity, water absorption and degradability in phosphate buffered saline (PBS) were investigated. Antibacterial properties, cell adhesion and proliferation were also evaluated. SEM results showed that fabricated PCL/Zein/GA scaffolds had a porous structure with bimodal diameters distribution. PCL/Zein/GA scaffolds showed high hydrophilic properties, favorable porosity (about 80%) and tensile strength of 1.36-3 MPa with an elongation of 19.13-44.06% desirable for skin tissue engineering. SEM images of degraded specimens show that the scaffold retains its fibrous structure during its destruction. The results of bacterial culture indicated that the scaffold containing GA had antibacterial properties. Moreover, in vitro assays revealed favorable L929 cells proliferation compared to tissue culture polystyrene (control). Hence, the PCL/Zein/GA scaffold shows a good potential for application in skin tissue engineering.

Erodibility of calcareous soils as influenced by land use and intrinsic soil properties in a semiarid region of central Iran.

The most important properties affecting the soil loss and runoff were investigated, and the effects of land use on the soil properties, together with the erodibility indices in a semiarid zone, central Iran, were evaluated. The locations of 100 positions were acquired by cLHS and 0-5-cm surface soil layer samples were used for laboratory analyses from the Borujen Region, Chaharmahal-Va-Bakhtiari Province, central Iran. To measure in situ runoff and soil erodibility of three different land uses comprising dryland, irrigated farming, and rangeland, a portable rainfall simulator was used. The results showed that the high variations (coefficient of variation, CV) were obtained for electrical conductivity (EC), mean weight diameter (MWD), soil organic carbon (SOC), and soil erodibility indices including runoff volume, soil loss, and sediment concentration (CV ~ 43.6-77.4%). Soil erodibility indices showed positive and significant correlations with bulk density and negative correlations with SOC, MWD, clay content, and soil shear strength in the area under investigation. The values of runoff in the dryland, irrigated farming, and rangeland were found 1.5, 28.9, and 58.7 cm3; soil loss in the dryland, irrigated farming, and rangeland were observed 0.25, 2.96, and 76.8 g; and the amount of sediment concentration in the dryland, irrigated farming, and rangeland were found 0.01, 0.11, and 0.15 g cm-3. It is suggested that further investigations should be carried out on soil erodibility and the potential of sediment yield in various land uses with varying topography and soil properties in semiarid regions of Iran facing the high risk of soil loss.

Cu-MOF: an efficient heterogeneous catalyst for the synthesis of symmetric anhydrides via the C-H bond activation of aldehydes.

In this paper, an efficient and straightforward synthetic approach for the preparation of a number of symmetric carboxylic anhydrides was reported using Cu2(BDC)2(DABCO) as an efficient heterogeneous catalyst via the C-H bond activation of aldehydes with excellent yields and simple work up. This C-H bond activation reaction appears simple and convenient, has a wide substrate scope and makes use of cheap, abundant, and easily available reagents. The Cu-MOF catalyst was recycled and reused four times without any loss of catalytic activity.

Molecular Design of Efficient Organic D-A-π -A Dye Featuring Triphenylamine as Donor Fragment for Application in Dye-Sensitized Solar Cells.

A metal-free organic sensitizer, suitable for the application in dye-sensitized solar cells (DSSCs), has been designed, synthesized and characterized both experimentally and theoretically. The structure of the novel donor-acceptor-π-bridge-acceptor (D-A-π-A) dye incorporates a triphenylamine (TPA) segment and 4-(benzo[c][1,2,5]thiadiazol-4-ylethynyl)benzoic acid (BTEBA). The triphenylamine unit is widely used as an electron donor for photosensitizers, owing to its nonplanar molecular configuration and excellent electron-donating capability, whereas 4-(benzo[c][1,2,5]thiadiazol-4-ylethynyl)benzoic acid is used as an electron acceptor unit. The influences of I3- /I- , [Co(bpy)3 ]3+/2+ and [Cu(tmby)2 ]2+/+ (tmby=4,4',6,6'-tetramethyl-2,2'-bipyridine) as redox electrolytes on the DSSC device performance were also investigated. The maximal monochromatic incident photon-to-current conversion efficiency (IPCE) reached 81 % and the solar light to electrical energy conversion efficiency of devices with [Cu(tmby)2 ]2+/+ reached 7.15 %. The devices with [Co(bpy)3 ]3+/2+ and I3- /I- electrolytes gave efficiencies of 5.22 % and 6.14 %, respectively. The lowest device performance with a [Co(bpy)3 ]3+/2+ -based electrolyte is attributed to increased charge recombination.

Resolution of Racemic Mixtures by Phase Transition of PEGylated Resolving Agents.

A novel, efficient, and simple method for the resolution of racemic mixtures is presented in which PEGylated resolving agents are subjected to diastereomeric complex formation in alcohols. The resulting complexes then undergo temperature-assisted phase transition, affording a precipitate that is enriched in one enantiomer and separable by filtration. In an aqueous solution, phase transition can be caused by the methods used in the precipitation of poly(ethylene glycol) (e.g., addition of ammonium sulfate). A number of racemic amines have been successfully resolved using this method. The first cycle of resolution affords the amines with an optical purity of 72-85% from their corresponding racemic mixture in good yields (78-90%). An additional cycle improved the optical purity to 87-95%. The PEGylated resolving agents can be recovered and reutilized without the loss of resolution efficiency.

Electrospinning of poly(vinyl alcohol)-water-soluble quaternized chitosan derivative blend.

Defect free mats containing a cationic polysaccharide, chitosan derivative such as N-[(2-hydroxy-3-trimethylammonium)propyl] chitosan chloride (HTCC), have been prepared using electrospinning of an aqueous solution of poly(vinyl alcohol) (PVA)-HTCC blends. HTCC, a water-soluble derivative of chitosan, was synthesized via the reaction between glycidyl-trimethylammonium chloride and chitosan. Solutions of PVA-HTCC Blends were electrospun. The morphology, diameter and structure of the produced electrospun nanofibres were examined by scanning electron microscopy (SEM). The average fibre diameter was in the range of 200-600 nm. SEM images showed that the morphology and diameter of the nanofibres were mainly affected by weight ratio of the blend and applied voltage. The results revealed that increasing HTCC content in the blends decreases the average fibre diameter. These observations were discussed on the basis of shear viscosities and conductivities of the spinning solutions. Microbiological assessment showed that the PVA-HTCC mats have a good antibacterial activity against Gram-positive bacteria, Staphylococcus aureus, and Gram-negative bacteria, Escherichia coli.

Kneading ball-milling and stoichiometric melts for the quantitative derivatization of carbonyl compounds with gas-solid recovery.

A ray of hope for the environment is sustainable and green synthesis without the production of (toxic) waste. Solvent-free stoichiometric melting or kneading ball-milling reactions of aldehydes or ketones with carbonyl reagents yields arylhydrazones and oximes in quantitative yield. The carbonyl compounds can be quantitatively recovered from the imino derivatives by using gaseous NO(2).An effective methodology of kneading with a ball mill under temperature control was used for the stoichiometric quantitative preparation of synthetically versatile oximes and 2,4-dinitrophenylhydrazones from low-melting aldehydes and ketones. Also, a large number of phenylhydrazones are obtained by safe stoichiometric quantitative melt reactions. Advantages of this technique are short reaction times, eco-friendliness, and ease of handling under solvent-free conditions, as no waste-producing purifying workup is necessary. The different reactivities of aldehydes and ketones allow for easy separation of mixtures containing aldehydes and ketones. Furthermore, a new effective, gas-solid deprotection methodology for oximes was developed, using nitrogen dioxide as the reagent under solvent-free conditions to recover the aldehydes or ketones. The corresponding aldehydes were obtained free of overoxidized acids in quantitative yields.

Sustainable synthesis of aldehydes, ketones or acids from neat alcohols using nitrogen dioxide gas, and related reactions.

Benzylic alcohols are quantitatively oxidized by gaseous nitrogen dioxide to give pure aromatic aldehydes. The reaction gas mixtures are transformed to nitric acid, which renders the processes free of waste. The exothermic gas-liquid or gas-solid reactions profit from the solubility of nitrogen dioxide in the neat benzylic alcohols. The acid formed impedes further oxidation of the benzaldehydes. The neat isolated benzaldehydes and nitrogen dioxide quantitatively give the benzoic acids. Solid long-chain primary alcohols are directly and quantitatively oxidized with nitrogen dioxide gas to give the fatty acids in the solid state. The oxidations with ubiquitous nitrogen dioxide are extended to solid heterocyclic thioamides, which gives disulfides, and to diphenylamine, which gives tetraphenylhydrazine. These sustainable (green) specific oxidation procedures produce no dangerous residues from the oxidizing agent or from auxiliaries.