Asymmetric Cyclic Phosphorothonamides Containing Substituted Pyridine

In order to find high-acitivity and low-toxicity pesticidal lead compounds, a type of novel, asymmetric cyclic phosphorothonamides containing substituted pyridine were synthesized via the condensation reactions of 2-chloro-4-substitutedphenyl-5,5-dimethyl-1,3,2-dioxaphosphinane 2-sulfide with 3-aminomethylpyridine. The cis and trans isomers of the products were isolated by column chromatography on silica gel. The structures of the products were characterized by ¹ H NMR, ³¹ P NMR, MS, and elemental analyses. The configuration of 3a was determined by X-ray diffraction analysis. The results of the preliminary bioassay showed that the new compounds possess potential fungicidal activities.     

α‐Cyanodithioic Acids and Their Corresponding Mono‐ and Dithiolate Salts as Building Blocks for the Synthesis of Novel Mercaptothiophenes

A novel and efficient method for the synthesis of mercaptothiophenes using cyanodithioic acids and their corresponding mono‐ and dithiolate salts as starting components is described.     

Synthesis of oxazole and furan derivatives via Rh2(OAc)4-catalyzed C≡X bond insertion of cyclic 2-diazo-1,3-diketones with nitriles and arylacetylenes

Abstract

A convenient and efficient procedure for the synthesis of 2-substituted-6,7-dihydrobenzo[d]oxazol-4(5H)-ones and 2-aryl-6,7-dihydrobenzofuran-4(5H)-ones through a Rh₂(OAc)₄-catalyzed C≡X (X?=?N, C) insertion of cyclic 2-diazo-1,3-diketones with nitriles and aromatic alkynes has been developed. This reaction uses readily available starting materials and stable cyclic 2-diazo-1,3-diketone compounds, with desired products formed in good to high yields. A tentative mechanism involving a C≡X bond insertion and 1,5-dipolar electrocyclization/ring opening and cyclization sequence for this reaction is proposed.     

Weight distributions of a class of cyclic codes with arbitrary number of nonzeros in quadratic case

Cyclic codes are an important class of linear codes, whose weight distribution have been extensively studied. So far, most of previous results obtained were for cyclic codes with no more than three nonzeros. Recently, the authors of [37] constructed a class of cyclic codes with arbitrary number of nonzeros, and computed the weight distribution for several cases. In this paper, we determine the weight distribution for a new family of such codes. This is achieved by introducing certain new methods, such as the theory of Jacobi sums over finite fields and subtle treatment of some complicated combinatorial identities.     

Solvent free synthesis,characterization, DFT,cyclic voltammetry and biological assay of Cu(II), Hg(II) and UO2(II) – Schiff base complexes

A series of metal ion complexes was prepared in solid state from Cu(II), Hg(II) and UO₂(II) ions with 3-oxo-3-(2-(2-oxoindolin-3-ylidene)hydrazineyl)-N-phenylpropanamide (H₃L) ligand through solvent free synthesis methodology. The chemical formulae of the new compounds were estimated according to variable spectral and analytical investigations. The ligand exhibited a neutral or mononegative tetradentate mode of coordination towards the central ions inside the octahedral arrangement that proposed for the three complexes. The DFT/B3LYP method was applied under different basis sets (6-31G*or SDD) to optimize the structures of new compounds except the UO₂(II) complex. The computational data were investigated to verify the binding mode that suggested spectrally. Moreover, studies in solution regarding Cu(II) ion via cyclic voltammetry were performed in absence or presence of H₃L, to realize the significant effect of complex formation on the electrochemical manners of copper. The shifts in the potential peaks accompanied by the changes in the values of parameters correspond to kinetic and thermodynamic. Also, the solvation and kinetic characteristics for the cathodic and anodic potential of Cu(II) ion in absence or presence of H₃L at different scan rates, were estimated. Finally, the ligand and copper ion exhibited high affinity towards complexation in solution. Furthermore, the activity of the new compounds towards inhibiting microbes was studied against Staphylococcus aureus (G+) and Escherichia coli (G-) bacteria as well as Candida albicans (fungus) by determining the inhibition zone diameter. Also, both the antioxidant and cytotoxic activity of the isolated compounds were evaluated. Commonly, a remarkable antimicrobial and anticancer activity was appeared with UO₂(II) complex and the ligand. While, the antioxidant activity of all compounds appeared lower.     

A Self‐contained Two‐electrode Nanosensor for Electrochemical Analysis in Aqueous Microenvironments

We describe the development, fabrication, and characterization of a novel two‐electrode nanosensor contained within the tip of a needle‐like probe. This sensor consists of two, vertically aligned, carbon structures which function as individual electrodes. One of the carbon structures was modified by silver electrodeposition and chlorination to enable it to function as a pseudo‐reference electrode. Performance of this pseudo‐reference electrode was found to be comparable to that of commercially available Ag/AgCl reference electrodes. The unmodified carbon structure was employed as a working electrode versus the silver‐plated carbon structure to form a two‐electrode sensor capable of characterizing redox‐active analytes. The nanosensor was demonstrated to be capable of electrochemically characterizing the redox behavior of para‐aminophenol (PAP) in both bulk solutions and microenvironments. PAP was also measured in cell lysate to show that the nanosensor can detect small concentrations of analyte in heterogenous environments. As the working and reference electrodes are contained within a single nanoprobe, there was no requirement to position external electrodes within the electrochemical cell enabling analysis within very small domains. Due to the low‐cost manufacturing process, this nanoprobe has the potential to become a unique and widely accessible tool for the electrochemical characterization of microenvironments.     

The use of ethylene glycol solution as the running buffer for highly efficient microchip-based electrophoresis in unmodified cyclic olefin copolymer microchips

An ethylene glycol solution was used as the electrophoretic running buffer in unmodified cyclic olefin copolymer (COC) microchips to minimize the interactions between the analytes and the hydrophobic walls of the plastic microchannels, enhance the resolution of the analytes and eliminate the uncontrollable dispersion caused by uneven liquid levels and non-uniform surfaces of the separation channels. Five amino acids that were labeled with fluorescein isothiocyanate (FITC) were used as model analytes to examine the separation efficiency. The effects of ethylene glycol concentration, pH and sodium tetraborate concentration were systematically investigated. The five FITC-labeled amino acids were effectively resolved using a COC microchip with an effective length of 2.5 cm under optimum conditions, which included using a running buffer of 20 mmol/L sodium tetraborate in ethylene glycol:water (80:20, v/v), pH 6.7. A theoretical plate number of 4.8 × 10(5)/m was obtained for aspartic acid. The system exhibited good repeatability, and the relative standard deviations (n=5) of the peak areas and migration times were no more than 3.4% and 0.7%, respectively. Furthermore, the system was successfully applied to elucidate these five amino acids in human saliva.     

Electrochemical methods for analysing and controlling charge transfer at the electrode–tissue interface

There have been rapid advances in the development of new materials for use in electrode–tissue interfacing. The development of conducting polymers, conducting hydrogels, carbon nanotubes, graphene and other conducting materials has provided a rich landscape for controlling charge transfer at the electrode–tissue interface and hence to monitor and manipulate cell behaviour. These materials have been used in tissue-engineered constructs to direct and control cell proliferation, growth and differentiation. However, their translation to clinical devices has been less successful. In this review, the use of electroanalytical techniques to develop an understanding of charge transfer at the electrode–tissue interface is discussed. In particular, the impact of solution and electrode conditions on charge injection capacity is demonstrated. The importance of standardised testing methods and the correlation of electrochemical and electrophysiological performance show the limitations of empirical studies and help define key electrode properties for clinical devices. The development of a sound theoretical basis for charge transfer at this increasingly important interface is being advocated to improve clinical outcomes and device lifetime and reduce power usage.     

Synthesis,Structure, Reactivity and Catalytic Implications of a Cationic,Acetylide-Bridged Trigold–JohnPhos Species

The cationic complex [(JohnPhos–Au)₃(acetylide)][SbF₆] (JohnPhos=(2-biphenyl)di-tert-butylphosphine, L1) has been characterised structurally and features an acetylide–trigold(I)–JohnPhos system; the trinuclear–acetylide unit, coordinated to the monodentate bulk phosphines, adopts an unprecedented μ,η¹,η²,η¹ coordination mode with an additional interaction between distal phenyl rings and gold centres. Other cationic σ,π-[(gold(I)L1)₂] complexes have also been isolated. The reaction of trimethylsilylacetylene with various alcohols (iPrOH, nBuOH, n-HexOH) catalysed by cationic [Au^IL1][SbF₆] complexes in CH₂Cl₂ at 50 °C led to the formation of acetaldehyde acetals with a high degree of chemo- and regioselectivity. The reaction mechanism was studied, and several organic and inorganic intermediates have been characterised. A comparative study with the analogous cationic [Cu^IL1][PF₆] complex revealed different behaviour; the copper metal is lost from the coordination sphere leading to the formation of cationic vinylphosphonium and copper nanoparticles. Additionally, a new catalytic approach for the formation of this high-value cationic vinylphosphonium has been established.