The Conjugate Addition-Cyclization of 3-Oxoacid Thioanilides to β-Nitrostyrenes. An Efficient Synthesis of Functionalized Thiophenes and their Transformation to Pyrroles

Summary. A new and simple method for synthesis of 2-, 3-, and 4-pyridylcarbonyl-2-aryliminothiophene derivatives based on the conjugate addition-cyclization of 3-oxoacid thioamides to β-nitrostyrenes was developed. Thiophene derivatives in acidic medium undergo ring transformation yielding corresponding pyrroles.     

The thermal transformations in Zn(No3)2-H2O (1:6) system

Using thermal analysis as well as isothermal gravimetric measurements, the thermal stability of the zinc nitrate(V) hexahydrate has been determined. Some intermediate products are the results of melting, evaporation, hydrolysis, polycondensation and decomposition processes occurring in the salt - water system up to 300°C. Solid phases were characterized by means of chemical analyses and X-ray powder diffraction method. This revised version was published online in July 2006 with corrections to the Cover Date.     

Measurement of Small One-Bond Proton–Carbon Residual Dipolar Coupling Constants in Partially Oriented C Natural Abundance Oligosaccharide Samples: Analysis of Heteronuclear JCH-Modulated Spectra with the BIRD Inversion Pulse

Two 2D J-modulated HSQC-based experiments were designed for precise determination of small residual dipolar one-bond carbon–proton coupling constants in ¹³C natural abundance carbohydrates. Crucial to the precision of a few hundredths of Hz achieved by these methods was the use of long modulation intervals and BIRD pulses, which acted as semiselective inversion pulses. The BIRD pulses eliminated effective evolution of all but ¹J_CH couplings, resulting in signal modulation that can be described by simple modulation functions. A thorough analysis of such modulation functions for a typical four-spin carbohydrate spin system was performed for both experiments. The results showed that the evolution of the ¹H–¹H and long-range ¹H–¹³C couplings during the BIRD pulses did not necessitate the introduction of more complicated modulation functions. The effects of pulse imperfections were also inspected. While weakly coupled spin systems can be analyzed by simple fitting of cross peak intensities, in strongly coupled spin systems the evolution of the density matrix needs to be considered in order to analyse data accurately. However, if strong coupling effects are modest the errors in coupling constants determined by the “weak coupling” analysis are of similar magnitudes in oriented and isotropic samples and are partially cancelled during dipolar coupling calculation. Simple criteria have been established as to when the strong coupling treatment needs to be invoked.     

Sol-gel material as a support of organometallic catalyst for ethylene polymerization

The sol-gel procedure was applied to obtain powdery materials with different structures and morphology. It was possible to produce almost non-porous silica powder, with an extremely low surface area (ca. 4 m²/g) and very high uniformity of spherical particles as well as materials with various uniformity of particles and different porosity, most likely associated with increasing pore volume. Dependent on the properties of the carrier, the resulting supported vanadium catalysts (VOCl₃/AlEt₂Cl) showed significant differences concerning activity and stability. It was confirmed that improved hydrophobicity of the carrier’s surface may be useful and improve the activity of the system in the polymerization. It was found that the two-step modification procedure, involving a reaction with alkylaluminum, acts beneficially for the efficiency of supported catalysts. The system supported on sol-gel material with methyl groups, additionally pre-treated with diethylaluminum chloride, showed the highest activity as well as the lowest deactivation rate constant among all those studied.     

Solid-phase extraction procedure for determination of phenolic acids and some flavonols in honey

The solid-phase extraction procedure (SPE) for isolation and preconcentration of phenolic acids (gallic, p-HBA, p-coumaric, vanillic, caffeic and syringic acid) and some flavonols (rutin, quercetin and kaempferol) from honey samples prior to their determination by HPLC is reported. Different solid sorbents such as Bond Elut octadecyl C(18), Oasis HLB, Strata-X and Amberlite XAD-2 were tested for this purpose. The best results were obtain when aqueous solution of honey (100 mL) was adjusted to pH 2 and passed through the microcolumn containing 2.5 g of Oasis HB followed by washing the sorbent with 50 mL of acidified water (pH 2). The analytes were then eluted with methanol. The proposed method permits the quantification of the studied compounds with the limit of detections ranged from 25 ng kg(-1) to 0.75 microg kg(-1) for p-HBA and quercetin, respectively. The precision of the overall analytical procedure was estimated by measuring the within-day repeatability and the relative standard deviations of the parallel (n=3) results were in the range of 1.9-10.1%. The method was tested for real honey samples from different botanical origins.     

Photocytotoxicity of platinum(IV)-chloride surface modified TiO2 irradiated with visible light against murine macrophages

Phototoxicity of titanium dioxide modified with platinum(IV)-chloride complexes, [TiO2/PtCl4], irradiated with visible light was tested on murine macrophage cell line (RAW 264.7) in vitro. Presence of antioxidants such as alpha-tocopherol or beta-carotene during photodynamic treatment significantly increased cells viability. Our results indicate that observed cell death induced by [TiO2/PtCl4] was due to photogeneration of reactive species.     

Spectroscopic investigations into degradation of polymer membranes for fuel cells applications

The research was focused on synthesis of proton conductive, easily degradable polymer membranes, which can be used as a model system to verify the efficiency of transition metal ions (TMI) in prevention of polymer degradation. Two polymers composed of 2-hydroxyethyl methacrylate (HEMA), 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPS), and styrenesulfonic acid (SS) were synthesized. The copolymers were characterized by gel permeation chromatography (GPC), elementary analysis, and FTIR and fluorescence spectroscopies. The results allowed determination of weight-average molecular weight and the copolymer composition. The protons of sulfonic groups were substituted by paramagnetic transition metal ions of various spin states (Cr(3+), S=3/2 and Mn(2+), S=5/2) with the loading varying from 0.5 up to 10 mol%. The effectiveness of spin catalysis was checked by EPR. The results obtained indicate enhancement of polymer stability in the presence of Mn(2+).     

Determination of anti-inflammatory drugs and estrogens in water by HPLC with UV detection

An analytical method based on LC and UV detection has been developed for the determination of anti-inflammatory compounds and estrogens in water samples. The drugs investigated were diclofenac, ketoprofen, ibuprofen, naproxen, clofibric acid, estriol, 17beta-estradiol, estrone and ethynylestradiol. The detection limits were in the range of 6-74 microg/L and 0.041 -0.16 mg/L for acidic pharmaceuticals and estrogens, respectively, using narrow-bore C18 analytical column. Analyte enrichment from water samples was achieved by SPE procedure using polymeric Strata-X cartridges. Average recoveries obtained from 2.5 L of surface water sample were in the range of 77-98%.