Synthesis of N-benzylated indole-, indazole- and benzotriazole-4,7-diones

The benzylation of 4,7-dimethoxy-1H-indole (5) followed by an oxidative demethylation led to 1-benzyl-1H-indole-4,7-dione (2) with a 73% overall yield. From the commercially available 7-nitro-1H-indazole (7), a three-step pathway was developed to access 1-benzyl-1H-indazole-4,7-dione (3). Two of these steps were investigated in order to improve the process. The direct synthesis of 1-benzyl-1H-benzotriazole-4,7-dione (4), through a 1,3-dipolar cycloaddition between benzyl azide and para-benzoquinone (13), was also studied. The simplicity of the methodologies described offers wide perspectives in obtaining 1-alkylated indole-, indazole- and benzotriazole-4,7-diones.     

Electroentrapment of Polyaniline in [3-(2,3-Epoxypropoxy)propyl]trimethoxysilane-Derived Xerogel: A Facile Methodology Towards Molecularly Imprinted Xerogels

A novel polyaniline (PANI)/silica hybrid composite, as a selective coating, was synthesized by the simultaneous sol–gel process and in situ electro-polymerization of aniline and employed for imprinting naproxen. The synthesized composite was chemically bonded inside a copper tube for online capillary microextraction (CME) in combination with high-performance liquid chromatography (HPLC). The copper tube was intended for use as an unbreakable substrate for CME and the HPLC injection loop. Four copper tubes containing different coatings were prepared accordingly to achieve the most appropriate extracting medium for naproxen. Coating 1 was a xerogel of [3-(2,3-epoxypropoxy)propyl]trimethoxysilane (EPPTMOS) synthesized by sol–gel technology and PANI as a conductive polymer (CP) was electrochemically prepared as coating 2. Coating 3 (sol–gel–CP) included the electroentrapped PANI into the xerogel of EPPTMOS, representing the non-imprinted xerogel (NIX) and coating 4, the molecularly imprinted xerogel (MIX), contained entrapped PANI into the xerogel of EPPTMOS, while naproxen template was already imprinted into the composite structure. Extraction efficiency of MIX towards naproxen was about 4–30 times greater than the others. Electroentrapped PANI into the silica xerogel might be responsible for the enhanced extraction efficiency, originating from high surface area of PANI as well as its role in π–π interactions. The mild conditions used in this process enabled the incorporation of organic species such as PANI into the silica particles without degradation. The main advantage of addition of PANI during the sol–gel process was the reduction of gelation time from more than a week to a few hours and, therefore, achieving a facile and controllable method for preparation of selective media. Furosemide, clodinafop-propargyl and haloxyfop-etotyl were also selected to investigate selectivity of the prepared MIX towards naproxen. Ratio of MIX/NIX, a criterion of selectivity, was 3.8, 1.1, 1.2, and 1.4 for naproxen, clodinafop, haloxyfop and furosemide, respectively. The linearity of the HPLC method for naproxen was in the range of 10–1,000 µg L^?1. The limit of detection value was found to be 5 µg L^?1 and RSD % of 2.9 (n = 5) was obtained. Real samples such as blood plasma and urine species were analyzed by the developed method and the relative recovery percentages of 76 and 94 % were obtained for the spiked samples.     

Chitosan-poly(m-phenylenediamine)@Fe3O4 nanocomposite for magnetic solid-phase extraction of polychlorinated biphenyls from water samples

A extraction medium based on chitosan-poly(m-phenylenediamine) (CS-PPD) @Fe₃O₄ nanocomposite was synthesized by chemical polymerization of m-phenylenediamine in the presence of chitosan coated magnetic nanocomposite, and for the first time, used as the sorbent for the magnetic solid-phase extraction (MSPE) of seven polychlorinated biphenyls (PCB28, PCB52, PCB101, PCB118, PCB138, PCB153, and PCB180) at trace levels in water samples. Gas chromatography-triple quadrupole mass spectrometry (GC-MS/MS) was used for PCBs quantification and detection. Several factors related to MSPE efficiencies, such as type and amount of sorbent, extraction time, sample pH, and desorption conditions were investigated. Under the optimized conditions, an excellent linearity was observed in the range of 1.0–200 ng L^–1 for PCB180, 0.5–200 ng L^–1 for the other six PCBs with the correlation coefficients ranging from 0.9954 to 0.9993. The good recoveries at spiked levels of 10.0, 20.0, and 50.0 ng L^–1 were obtained in the range of 94 %–108 %, and the coefficients of variations were less than 6 %. The proposed method was feasible, rapid, and easy to operate for the trace analysis of the PCBs in local aquaculture water, livestock breeding water, and sewage water samples. Graphical Abstract

Fig. 1 Schematic diagram for the preparation of chitosan–poly(m-phenylenediamine) @Fe₃O₄ nanocomposite.     

Synthesis of new aryl(hetaryl)vinyl-substituted benzo[<Emphasis Type="Italic">f</Emphasis>]quinolines and 4,7-phenanthrolines

Previously unknown 1-[2-aryl(quinolin-2-yl)ethenyl]-3-[aryl(quinolin-2-yl)]benzo[f]quinolines and 3-aryl-1-(2-arylethenyl)-4,7-phenanthrolines were synthesized by reactions of 1-methylbenzo[f]quinolines and 1-methyl-4,7-phenanthrolines with substituted N-benzylideneanilines and N-(quinolin-2-ylmethylidene)aniline on heating in dimethylformamide in the presence of potassium hydroxide.     

Analysis of urinary vitamin D3 metabolites by liquid chromatography/tandem mass spectrometry with ESI-enhancing and stable isotope-coded derivatization

The determination of the urinary vitamin D₃ metabolites might prove helpful in the assessment of the vitamin D status. We developed a method for the determination of trace vitamin D₃ metabolites, 25-hydroxyvitamin D₃ [25(OH)D₃] and 24,25-dihydroxyvitamin D₃ [24,25(OH)₂D₃], in urine using liquid chromatography/electrospray ionization-tandem mass spectrometry (LC/ESI-MS/MS) combined with derivatization using an ESI-enhancing reagent, 4-(4′-dimethylaminophenyl)-1,2,4-triazoline-3,5-dione (DAPTAD), and its isotope-coded analogue, ²H₄-DAPTAD (d-DAPTAD). The urine samples were treated with β-glucuronidase, purified with an Oasis® hydrophilic–lipophilic balanced (HLB) cartridge, and then subjected to the derivatization. The DAPTAD derivatization enabled the highly sensitive detection (detection limit, 0.25 fmol on the column), and the use of d-DAPTAD significantly improved the assay precision [the intra- (n?=?5) and inter-assay (n?=?3) relative standard deviations did not exceed 9.5 %]. The method was successfully applied to urine sample analyses and detected the increases of the urinary 25(OH)D₃ and 24,25(OH)₂D₃ levels due to vitamin D₃ administration. Graphical Abstract

Scheme of procedure for urinary vitamin D₃ metabolite analysis based on LC/MS/MS with ESI-enhancing and isotope-coded derivatization.     

Dehydrogenation of 4-aryl(hetaryl) spinacine derivatives with dimethyl sulfoxide

Aromatization of 4-aryl(hetaryl)tetrahydroimidazo[4,5-c]pyridine-6-carboxylic acids and their lithium salts by the action of dimethyl sulfoxide has been revealed for the first time. Heating of these compounds in DMSO for 5–7 h at 90–95°C leads to the formation of 4-aryl(hetaryl)imidazo[4,5-c]pyridine derivatives as a result of dehydrogenation and decarboxylation. Heating of the corresponding lithium salts generated in situ (DMSO, 90–95°C, 3–5 h) affords difficultly accessible 4-aryl(hetaryl)imidazo[4,5-c]pyridine-6-carboxylic acids.     

Synthesis of 3-substituted and 1,3-disubstituted 4,7-diazaindoles

On the basis of a study of electrophilic substitution reactions (the Mannich reaction and bromination) it was shown that 4,7-diazaindoles react with greater difficulty with soft electrophilic agents than indoles or 4- and 7-monoazaindoles. 3-Substituted and 1,3-disubstituted 4,7-diazaindoles containing amino(dialkylamino)alkyl substituents in the 1 or 3 positions were synthesized.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 848–852, June, 1976.     

Co3O4/SiO2 nanocomposites for supercapacitor application

In this study, Co₃O₄/SiO₂ nanocomposites have been successfully synthesized by citrate–gel method by utilizing SiO₂ matrix for Co₃O₄ embedment. Spectroscopy analyses confirm the formation of high crystalline Co₃O₄ nanoparticles; meanwhile, microscopy findings reveal that the Co₃O₄ nanoparticles are embedded in SiO₂ matrix. Electrochemical properties of the Co₃O₄/SiO₂ nanocomposites were carried out using cyclic voltammetry (CV), galvanostatic charge–discharge, and electrochemical impedance spectroscopy (EIS) in 5 M KOH electrolyte. The findings show that the charge storage of Co₃O₄/SiO₂ nanocomposites is mainly due to the reversible redox reaction (pseudocapacitance). The highest specific capacitance of 1,143 F g ^?1 could be achieved at a scan rate of 2.5 mV s^?1 in the potential region between 0 and 0.6 V. Furthermore, high-capacitance retention (>92 %) after 900 continuous charge–discharge tests reveals the excellent stability of the nanocomposites. It is worth noting from the EIS measurements that the nanocomposites have low ESR value of 0.33 Ω. The results manifest that Co₃O₄/SiO₂ nanocomposites are the promising electrode material for supercapacitor application.     

Liquidus and glass transition temperatures of the ammonium nitrate-dimethylsulfoxide-water system

The liquidus temperature was measured in the ammonium nitrate-dimethylsulfoxide-water system over in the concentration range 0–60 mole% ammonium nitrate. The probable formation of the NH₄NO₃·nDMSO solvate with n=1.3–1.5 and the mixed solvate NH₄NO₃·DMSO·H₂O at 30 mole% ammonium nitrate and a DMSO:H₂O ratio of 4∶1 are indicated. The glass transition temperatures T _g were measured over a salt concentration range of 0–50 mol% ammonium nitrate and at various compositions of the mixed solvent (y _DMSO =0.1–0.9 mole fraction). At a constant mixed solvent composition, the dependence of the glass transition temperature on the salt concentration can be approximated by a linear relationship, as can its dependence on the DMSO content in the solution at constant salt concentration. The glass-forming composition regions were found and the limits of this region are discussed.     

Corrosion inhibition investigations of 3-acetylpyridine semicarbazone on carbon steel in hydrochloric acid medium

The corrosion inhibition efficiency of 3-acetylpyridine-semicarbazide (3APSC) on carbon steel (CS) in 1.0 M HCl solution has been investigated using weight loss measurements, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization studies. The results show that inhibition efficiency on metal increases with the inhibitor concentration. 3APSC exhibited marked inhibition towards carbon steel in HCl medium even at low concentrations. The adsorption of inhibitor on the surfaces of the corroding metal obeys the Langmiur isotherm and thermodynamic parameters (K _ads, ?G _ads ⁰ ) were calculated. Activation parameters of the corrosion process (E _a, ?H* and ?S*) were also calculated from the corrosion rates. Polarization studies revealed that 3APSC act as a mixed-type inhibitor. Surface analysis of the metal specimens was performed by scanning electron microscopy.     

On the determination of HCl+ (A,v′) vibrational populations from HCl+ (A→X) fluorescence spectra: direct comparison between photoionization and penning ionization

Using a beam apparatus, we have measured the HCl⁺ (A,v′→X,v″) fluorescence spectra of HCl⁺ (A,v′) ions formed in HeI (58.4 nm), and NeI (73.6 nm) photoionization and, for the first time, in He (2³ S) Penning ionization under single collision conditions with a wavelength bandwidth around 1 nm. In addition, we have studied Ne (3s ³ P _{2, 0}) Penning ionization of HCl at three different collision energies. The procedure and the problems in extracting HCl⁺ (A,v′) vibrational populations from the data are discussed in some detail. Thedirect comparison of photoionization and Penning ionization data allows definitive conclusions to be drawn on the question whether final state interactions in the Penning reaction change the “nascent” vibrational population (determined by electron spectrometry); for He (2³ S)+HCl, such changes are shown to be absent within the experimental uncertainty (<±10%). For Ne (3s ³ P _{2, 0})+HCl, the HCl⁺ (A,v′=0, 1) populations are also found to be close to those measured by electron spectrometry and essentially independent of collision energy in the range 34–96 meV. From measurements of the fluorescence intensity as a function of HCl density, we have evidence for a fast loss of HCl⁺ (A,v′) ions in collisions with HCl (rate constant around 5·10^?9 cm³s^?1).     

Effect of BiFeO3 doping on ferroelectric properties of Na0.5Bi0.5TiO3–BaTiO3 based thin film derived by sol–gel method

0.94Na_0.5Bi_0.5TiO₃–0.06BaTiO₃ (NBT–6BT) and (0.94 ? x)Na_0.5Bi_0.5TiO₃–0.06BaTiO₃–xBiFeO₃ (NBT–6BT–xBFO, x = 0.03, 0.05 and 0.08) thin films were deposited on Pt/Ti/SiO₂/Si substrates by a sol–gel process. Relative permittivity and remnant polarization were maximized at 5 % BFO substitution. Compared with 0.94NBT–0.06BT, the leakage current density of 0.89NBT–0.06BT–0.05BFO at 600 kV/cm is reduced by one order of magnitude. Enhanced ferroelectricity was also achieved in 0.89NBT–0.06BT–0.05BFO, the remnant polarization (2P _r) values of 0.89NBT–0.06BT–0.05BFO and 0.94NBT–0.06BT are 46 and 24 µC/cm².     

New validated LC-MS/MS method for the determination of three alkylated adenines in human urine and its application to the monitoring of alkylating agents in cigarette smoke

A highly specific liquid chromatography–tandem mass spectrometry (LC–MS/MS) method was developed for simultaneous determination of urinary N ³-methyladenine (N ³-MeA), N ³-ethyladenine (N ³-EtA), and N ³-(2-hydroxyethyl)adenine (N ³-HOEtA). Chromatographic separation was achieved on a hydrophilic interaction liquid chromatography column, with a mobile phase gradient prepared from aqueous 10 mM ammonium formate–acetonitrile (5:95 v/v, pH 4.0). Quantification of the analytes was done by multiple reaction monitoring using a triple-quadrupole mass spectrometer in positive-ionization mode. The limits of quantification were 0.13, 0.02, and 0.03 ng/mL for N ³-MeA, N ³-EtA, and N ³-HOEtA, respectively. Intraday and interday variations (relative standard deviations) ranged from 0.6 to 1.3 % and from 3.7 to 7.5 %. The recovery ranges of N ³-MeA, N ³-EtA, and N ³-HOEtA in urine were 80.1–97.3 %, 83.3–90.0 %, and 100.0–110.0 %, respectively. The proposed method was successfully applied to urine samples from 251 volunteers including 193 regular smokers and 58 nonsmokers. The results showed that the levels of urinary N ³-MeA, N ³-EtA, and N ³-HOEtA in smokers were significantly higher than those in nonsmokers. Furthermore, the level of urinary N ³-MeA in smokers was found to be positively correlated with the level of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (r?=?0.48, P?N?=?192). This method is appropriate for routine analysis and accurate quantification of N ³-MeA, N ³-EtA, and N ³-HOEtA. It is also a useful tool for the surveillance of alkylating agent exposure. Figure

A new validated LC-MS/MS method couple with Oasis MCX column for simultaneous determination of three alkylated DNA adducts and evaluation of correlation with 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol in smokers’ urine     

Synthesis and properties of films in the SiO2-Bi2O3 system

The compositions of film-forming solutions for synthesizing films in the SiO₂-Bi₂O₃ system were determined (10–90 mol % Bi₂O₃). The obtained films are characterized by high dielectric constants (2.43–7.89). It was demonstrated how the quantitative ratio between SiO₂ and Bi₂O₃ in the films and powders affects their phase composition, refractive index, and dielectric constant and the acid-base properties of the surface.     

Kinetics of Water-Mediated Fluctuations in Room Temperature Ionic Liquid: N,N-Diethyl-N-methyl-N-(2-methoxyethyl) Ammonium Tetrafluoroborate

The kinetics of small-angle X-ray scattering (SAXS) was assessed in the room temperature ionic liquid (RTIL)–x mol% H₂O system, where the RTIL is N,N-diethyl-N-methyl-N-(2-methoxyethyl) ammonium tetrafluoroborate, [DEME][BF₄]. During equilibration of a non-equilibrium state, the largest time evolution of SAXS was observed at approximately 90 mol% H₂O. Above 85 mol% (x _c), the SAXS intensity increased gradually for 24 h. For the larger q region, the prepeak and principal peak in X-ray diffraction patterns have no time dependence in the water-rich region (70–91 mol%). The long time relaxation process observed in SAXS was related to the outstanding pH oscillations at 90–95 mol% over several days in the [DEME][BF₄]–water system. The x _c for nonequilibrium anomalies is related to the equilibrated crossover concentration from 65–85 mol% (from SAXS) to 85–95 mol% (for the prepeak in X-ray diffraction) in the [DEME][BF₄]–H₂O system. Inside [DEME][BF₄], the dynamic and static properties of hydrogen bonding of water changed drastically at x _c.     

Synthesis and structure of the rhodium complex [Ph3MeP][RhBr4(DMSO)2-trans]

The ionic complex, methyltriphenylphosphonium(I) trans-bis(dimethylsulfoxido)tetrabromorhodiate, was prepared by the reaction of sodium hexabromorhodiate with methyltriphenylphosphonium bromide in dimethyl sulfoxide and studied by X-ray diffraction. The phosphorus atom in the [Ph₃MeP]⁺ cation has an almost undistorted tetragonal coordination (the CPC angles are 108.3(2)°–110.5(2)°, the P-C bonds are 1.779(6)–1.798(4) Å). In the octahedral complex anion [RhBr₄(DMSO)₂-trans]^?, the dimethyl sulfoxide ligands are coordinated by the sulfur atoms (Rh-S, 2.344(1), 2.336(1); Rh-Br, 2.4839(7)–2.4934(7) Å; SRhS, 179.56(7)°; trans-BrRhBr, 179.30(3)°, 179.56(7)°) (CIF file CCDC no. 978748).     

Preparation of Cu (II)/PEI–QPEI/SiO2 nanopowder as antibacterial material

The silica nanoparticles were prepared by the sol–gel process, and then twice modified and grafted by polyethylenimine (PEI) on their surface. After quaternary ammonium reaction and chelated copper reaction, the PEI/SiO₂, QPEI/SiO₂, PEI–QPEI/SiO₂ and Cu (II)/PEI–QPEI/SiO₂ nanopowders were obtained in turn. The morphology and structure of the products were characterized through SEM, EDX, HRTEM, FTIR and element analysis. At the same time, the antibacterial activity of the products to E. coli and Candida were evaluated through quantification and qualitative ways, e.g. microcalorimetric method and culture dish method. The results suggested that the Cu (II)/PEI–QPEI/SiO₂, a novel three-component functional nanopowder, presented the best antibacterial activity to both E. coli and Candida duo to the synergistic sterilization capability of the ammonium salt and copper ions, compared with other products. It indicated that the Cu (II)/PEI–QPEI/SiO₂ nanopowder could be a novel antibacterial nanomaterial to widely application in preventing and minimizing bacteria of the organism and environment in future.     

Structure of Na2O–MgO–CaO–SiO2 glasses by combined Raman spectroscopy and thermodynamic modeling approach

The present contribution deals with the Raman spectra and structure of Na₂O–MgO–CaO–SiO₂ glasses. Six glasses with the trisilicate overall composition 15Na₂O·xMgO·(10–x)CaO·75SiO₂ (x = 0, 2, 4, 6, 8, 10) were studied. The structure of studied glasses was described by the thermodynamic model of Shakhmatkin and Vedishcheva. From the 27 components with the stoichiometry given by the composition of stable crystalline phases, only eight were found in significant abundance in the studied glasses—namely: SiO₂, 2MgO·SiO₂ (M2S), MgO·SiO₂ (MS), Na₂O·3CaO·6SiO₂ (NC3S6), Na₂O·CaO·5SiO₂ (NCS5), Na₂O·MgO·4SiO₂ (NMS4), Na₂O·SiO₂ (NS), and Na₂O·2SiO₂ (NS2). The correlation analysis points out that the strong positive correlations between the equilibrium molar amounts of: {M2S–MS–SiO₂}, {NC3S6–NCS5}, and {NMS4–NS–NS2}. From the components of significant abundance, only the content of MS and NC3S6 change significantly within the studied compositional series. These two components were identified with the result of the principal component analysis of Raman spectra that indicated the presence of two independent spectral components. Using the method of Malfait the partial Raman spectra of MS and NC3S6 components were found. The obtained results very well reproduce the experimental Raman spectra and confirmed in such way the thermodynamic model.     

Toward mechanized peptide synthesis via polymeric reagents approach

Simultaneous application of high-molecular-weight active esters and polyvinylN,N- diethylbenzylamine was used as a basis for a continuous peptide synthesis via the polymeric reagents approach. Using the synthetic procedure developed, the hexapeptide Boc-L-Pro-L-Val-L-Lys[Z(p-NO₂)]-L-Val-L-Tyr(Dnp)-L-Pro-OBzr¹ and the tetrapeptide Boc-l-Lys[Z(p-NO₂)]-L-Lys[Z(p-NO₂)]-L-Arg(NO₂)-L-Arg(NO₂)-OBzr, corresponding to residues 19–24 and 15–18 of human ACTH, were synthesized in 63 and 70% overall yields, respectively.     

Synthesis of 4-substituted 1,5-diaryl-3-diphenylmethoxy-3-pyrrolin-2-ones and their [1,5]-sigmatropic rearrangement

Reactions of 1,4,5-trisubstituted 3-hydroxy-3-pyrrolin-2-ones with diphenyldiazomethane yield the O-alkylation products. Thermolysis of 1,5-diaryl-4-heteroyl-3-hydroxy-3-pyrrolin-2-ones is accompanied with suprafacial [1,5]-sigmatropic rearrangement.