Novel reduction of perfluoroalkyl ketones with lithium alkoxides

The reaction of tert-butyl N-(2-bromophenyl)carbamate (1) with ethyl perfluorooctanoate in the presence of tert-butyllithium did not give the desired N-(2-perfluorooctanoylphenyl)carbamate (3) but gave 1-hydroxy-1H-perfluorooctyl compound (4), which was supposed to be formed by the reduction of 3. A similar reaction of 2,2,2-trifluoroacetophenone with tert-butyllithium did not gave any reduction product. Detailed investigation showed that lithium ethoxide worked as the reducing agent of this abnormal reduction. By the reaction of lithium isopropoxide, an aldol product from 2,2,2-trifluoroacetophenone with acetone was isolated, while perfluoroheptyl or perfluoropropyl phenyl ketones were reduced by this alkoxide in a high yield without formation of the aldol adduct.     

Interaction of manganese(II), iron(II), cobalt(II), nickel(II), copper(II) and zinc(II) with acetylhydrazine, formed in situ; first crystal structure of tris(acetylhydrazine) nickel(II) perchlorate

A series of transition metal complexes of the type [M(ah)₃](ClO₄)₂ (1–6) [M = Mn^II, Fe^II, Co^II, Ni^II, Cu^II and Zn^II, ah = acetylhydrazine] have been prepared by the reaction of M(ClO₄)₂ · 6H₂O with acetylhydrazine formed in situ by the reaction of hydrazine hydrate and acetylsalicylic acid methyl ester. The chelating behaviour of acetylhydrazine and overall geometry of these complexes have been spectroscopically investigated by means of FT-IR, ¹H-n.m.r. and electronic spectral techniques, as well as by elemental analysis data, molar conductance values and magnetic susceptibility measurements. Single X-ray structure determination of complex (4) revealed three acetylhydrazine ligands coordinated to nickel ion in a bidentate manner maintaining an octahedral environment. In all other complexes too, an octahedral geometry has been proposed on the basis of results obtained by various physico-chemical studies.     

Synthesis of some novel 3,7‐dimethyl‐4H‐pyrazolo[5,1‐c][1,2,4]triazin‐4‐ones

Some novel 3,7‐dimethyl‐6H‐pyrazolo[5,1‐c][1,2,4]triazin‐4‐ones were prepared (3a‐g) . Compounds 3a,b were treated with hydrazines to afford various products 7a,b, 8a,b, 9 and lla,b depending on the type of hydrazine derivative and reaction conditions. The benzoyloxyimino‐pyrazolo[5,1‐c][1,2,4]triazines (13a,b) were synthesized by refluxing of compounds 3a,b with hydroxylamine hydrochloride to afford the corresponding oxime derivatives followed by treatment with benzoyl chloride.     

Network structure of molybdenum lead phosphate glasses: Infrared spectra and constants of elasticity

Molybdenum lead phosphate glasses doped with La₂O₃ of the system xMoO₃-5La₂O₃-50P₂O₅-(45−x)PbO, with 0≤x≤25 mol%, have been synthesized and studied by FTIR, ultrasonic and differential scanning calorimetry (DSC) in order to investigate the role of MoO₃ content on their atomic structure. The constants of elasticity and Debye temperatures of the glasses have been investigated using sound velocity measurements at 4 MHz. According to the IR analysis, the vibrations of the phosphate structural units are shifted towards higher wavenumbers associated with the formation of bridging oxygens. The change in density with MoO₃ content reveals that the molybdate units are less dense than the lead units. The observed compositional dependence of the constants of elasticity is interpreted in terms of the effect of MoO₃ on the different phosphate bonds. It is assumed that MoO₃ plays the role of a former by increasing the ultrasonic velocity and the constants of elasticity of the phosphate glasses.     

Rerouting end-face-TIR capable rays to significantly increase evanescent wave signal power

The critical findings associated with end-face total internal reflection (TIR) phenomemon we proved before are reported.In particular,these findings reveal that the end-face-TIR capable rays experience enormous mode mixing when encountering a roughened end face.As a result,94% of the overall detectable power is contributed by this effect.With a smooth fiber end face,this figure is mere 52%.We interpret the mechanism behind these unusual phenomena and its significance for the performance enhancement of fiber optic evanescent wave sensor.     

Synthesis,Reactions, and Antiviral Activity of 1-(1H-Pyrazolo[3,4-b]pyridin-5-yl)ethanone and Pyrido[2′,3′:3,4]pyrazolo[5,1-c][1,2,4]triazine Derivatives

1-(3-Amino-6-methyl-4-pyridin-3-yl-1H-pyrazolo[3,4-b]pyridin-5-yl)ethanone (3) was obtained in very pure state and used as a good starting material for the present study. It diazotized to give the corresponding diazonium salt 9 and also reacted with phenyl isothiocyanate to give the corresponding thiourea derivative 4. Compound 4 was used for the preparation of thiazole derivatives 5–8 via the reaction with active halogen-containing compounds. On the other hand, compound 9 coupled with several active –CH₂- containing compounds to afford the corresponding triazine derivatives 10–17. Considering the data from IR, ¹ H NMR, mass spectra, and elemental analyses, the chemical structures of the newly synthesized heterocyclic compounds were elucidated. Cytotoxicity, anti-HSV1, and anti-HAV-MBB activity were evaluated for the newly synthesized heterocyclic compounds.     

Naphthoxazole‐Based Singlet Oxygen Fluorescent Probes

In this study, we report the synthesis and photochemical behavior of a new family of photoactive compounds to assess its potential as singlet oxygen (¹O₂) probes. The candidate dyads are composed by a ¹O₂ trap plus a naphthoxazole moiety linked directly or through an unsaturated bond to the oxazole ring. In the native state, the inherent great fluorescence of the naphthoxazole moiety is quenched; but in the presence of ¹O₂, generated by the addition and appropriate irradiation of an external photosensitizer, a photooxidation reaction occurs leading to the formation of a new chemical entity whose fluorescence is two orders of magnitude higher than that of the initial compound, at the optimal selected wavelength. The presented dyads outperform the commonly used indirect fluorescent ¹O₂ probes in terms of fluorescence enhancement maintaining the required specificity for ¹O₂ detection in solution.     

Xylanase production by Penicillium canescens 10–10c in solid-state fermentation

Filamentous fungi have been widely used to produce hydrolytic enzymes for industrial applications, including xylanases, whose levels in fungi are generally much higher than those in yeast and bacteria. We evaluated the influence of carbon sources, nitrogen sources, and moisture content on xylanase production by Penicillium canescens 10–10c in solid-state fermentation. Among agricultural wastes tested (wheat bran, untreated wheat straw, treated wheat straw, beet pulp, and soja meal), untreated wheat straw gave the highest production of xylanase. Optimal initial moisture content for xylanase production was 83%. The addition of 0.4 g of xylan or easily metabolizable sugar, such as glucose and xylose, at a concentration of 2% to wheat straw enhanced xylanase production. In solid-state fermentation, even at high concentrations of glucose or xylose (10%), catabolic repression was minimized compared to the effect observed in liquid culture. Yeast extract was the best nitrogen source among the nitrogen sources investigated: peptone, ammonium nitrate, sodium nitrate, ammonium chloride, and ammonium sulfate. A combination of yeast extract and peptone as nitrogen sources led to the best xylanase production.     

Viscous dissipation of Rankine vortex profile in zero meridional flow

An analytical solution is given for a time-decay Rankine vortex profile due to viscous effects. The vortex filament is assumed to be isolated, strong, concentrated and having zero-meridional flow (i.e. radial and axial velocities are equal to zero). Zero-meridional renders the governing equations for an unsteady, incompressible and axisymmetric vortex in a simple form. Based on the tangential momentum equation, the spatial-temporal distributions of the swirl velocity are given in terms of Fourier-Bessel series by using separation of variables technique. A general formula is derived by total differentiation of the swirl velocity with respect to time, depicting the viscous dissipation for Oseen and Taylor-like vortex profiles. This analysis is validated by comparison with previous experimental data.     

Simultaneous determination of piracetam and vincamine by spectrophotometric and high-performance liquid chromatographic methods

A mixture of piracetam and vincamine was determined by 3 different methods. The first was the determination of piracetam and vincamine using the ratio-spectra first-derivative (DD1) spectrophotometric technique at 209 and 293 nm in concentration ranges of 10-45 and 2-14 microg/mL with mean recoveries of 99.22 +/- 0.72 and 99.67 +/- 0.79%, respectively. The second method was based on the resolution of the 2 components by bivariate calibration depending on a mathematic algorithm that provides simplicity and rapidity. The method depended on quantitative evaluation of the absorbencies at 210 and 225 nm in concentration ranges of 5-45 and 2-14 microg/mL, with mean recoveries of 100.33 +/- 0.54 and 100.44 +/- 0.98% for piracetam and vincamine, respectively. The third method was reversed-phase liquid chromatography using 0.05 M potassium dihydrogen phosphate-methanol (50 + 50, v/v) as the mobile phase, with the pH adjusted to 3.5 with phosphoric acid. The eluent was monitored at 215 nm in concentration ranges of 5-100 and 2-200 microg/mL, with mean recoveries of 99.62 +/- 0.67 and 99.32 +/- 0.85% for piracetam and vincamine, respectively. The suggested procedures were checked using laboratory-prepared mixtures and were successfully applied for the analysis of their pharmaceutical preparation. The methods retained their accuracy and precision when applying the standard addition technique. The results obtained by applying the proposed methods were statistically analyzed and compared with those obtained by the manufacturer's method.