Diels-Alder versus heterodiene reaction: The effect of acid catalysis.

The difference between thermal, AlCl₃- and CF₃ COOH-catalyzed reaction of (E)-4-benzal-1-phenyl-5-pyrazolone and 2,3-dimethylbutadiene is discussed in terms of Diels-Alder $\text{versus}$ heterodiene reactivity.     

Separation and detection of oxidation products of fluorodeoxyglucose and glucose by high-performance liquid chromatography-electrospray ionisation mass spectrometry

2-Deoxy-2-[18F]fluoro-D-glucose ([18F] FDG), the most popular positron emitting radiopharmaceutical, may oxidise by autoradiolysis in aqueous solution. The aim of this work was to use LC-MS for determination of the oxidation products of fluorodeoxyglucose and glucose (Glc) obtained by oxidation with Fenton's reagent. Asahipak NH2P-50 polyamide silica column and acetonitrile-0.025% aqueous ammonium formate (80:20 (v/v)) eluent were utilised with an Agilent 1100 HPLC-MS instrument. Ten major oxidation products of FDG and Glc were separated and identified by mass spectrometry: 2-fluorogluconic acid, 2-fluoroglucuronic acid, 2-oxoerythronic acid, arabinose, arabonic acid, araburonic acid, erythrose, erythrulose, gluconic acid, and glucuronic acid. The most intensive electrospray ionisation signals were found in the negative ion spectra and were due to HCOO- adducts, the other acids being in their lactone forms.     

Unsymmetrical diaryl sulfones through palladium-catalyzed coupling of aryl boronic acids and arylsulfonyl chlorides

[reaction: see text] A simple and efficient method for the synthesis of unsymmetrical diaryl sulfones using the palladium-catalyzed coupling of aryl boronic acids and arylsulfonyl chlorides has been developed. High product yields, a short reaction time, and mild reaction conditions are important features of this method.     

Kinetic Aspects of Dimethylamine Hydroxyethylation in the Presence of Water

The kinetics of dimethylamine hydroxyethylation at an ethylene oxide : dimethylamine : water molar ratio of 1 : 3 : (0.1–0.5) was studied in the temperature range 20–50°C. A kinetic model of the reaction, which adequately describes the experimental data, was suggested.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 4, 2005, pp. 687–689.Original Russian Text Copyright © 2005 by Danov, Kolesnikov, Efremov, Mezhenin.     

Synthesis,structure, and dynamic behavior in solution of arylamino-1,3,5-triazines

Ten unsymmetrically substituted arylamino-1,3,5-triazines were synthesized and studied by dynamic NMR spectroscopy. The free energies of the hindered rotation ΔG^≠?are in 59–77 kJ mol^{? 1} range. Using difference-mode NOE NMR experiments, the structures of the major and minor rotation isomers were proved. The DFT B3LYP/6-31G* calculations were performed. The difference between the calculated rotation barriers and the experimental values obtained by line shape analysis is less than 7.6 kJ mol^?1. The height of the rotation barrier varies in a 18 kJ mol^?1 range depending on the substituents in the triazine ring.     

2-Carbethoxymethyl-4H-3,1-benzoxazin-4-one. 3. Condensation of o-phenylenediamive

3-(2-Benzimidazolyl)-4-hydroxy-2-quinolone was unexpectedly obtained as the principal reaction product on fusion of 2-carbethoxymethyl-4H-3,1-benzoxazin-4-one with o-phenylenediamine. A possible mechanism of its formation is presented.For Communication 2 see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 239–241, February, 1992.     

Liquid chromatography of platinum metals and prospects of development

Summary A survey of the authors' work on liquid chromatography of platinum metals in the form of chelates with 1-(2-pyridylazo)-2-naphthol (PAN) is given. Extraction chromatography with PAN in isopentanol as a stationary phase was used to achieve a group concentration of these metals (Pd, Pt and Rh, concentration coefficient 100) from large volumes of aqueous solutions and a selective extraction of palladium from solutions containing other platinum, nonferrous and heavy metals on a 85–98° C thermostatted chromatographic column. The prospects for the use of liquid chromatography in the analysis of platinum metals are discussed.

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Flüssig-Chromatographie von Platinmetallen und zukünftige Entwicklungen

     

Dependence of the efficiency of a multicapillary column on the liquid phase loading method

One of the main approaches employed to reach fast chromatographic separation is based on using columns containing up to 1000 capillaries with the diameter size down to 10-100 microm. The efficiency of such columns depends on the dispersion of the capillary radius and on the way of the liquid-film loading. We present general equations describing these effects. Specifically, we show theoretically and experimentally that the separation efficiency can be improved by using the loading methods specially designed in order to take into account correlation between the film thickness and capillary radius.     

BISPHENYLENECOSAN as highly selective Cs+ extraction agent

A new reagent for the highly selective extraction of cesium (e-1,7–2,2)4,8–8,4-(bis--o-phenylene)bisdicarbollidocobalt(1–)ate, [(C₂B₉H₉)₂(C₆H₄)₂Co]^–, abbreviated as BISPHECOSAN is described in this paper. The choice of organic solvent and solubilizer, dependence of distribution ratio of Cs⁺ on acidity and other parameters are studied. The extraction mechanism based on selective binding of Cs⁺ cation between two phenylene rings is presented and factors influencing the chemical stability of the reagent are determined.     

Time Positron Diagnostics of Metal β-Diketonates

The effects of the nature of the metal atom and -substituents in aluminum(III), chromium(III), cobalt(III), and iron(III) acetylacetonates on the lifetime and intensity of a long-lived component in positron and positronium annihilation were studied by the method of positron diagnostics. An addition of a positron to the -system of a chelate ring is supposed, which makes it possible to qualitatively estimate the basicities of the complexes. Annihilation of positrons and halogen-containing positronium -diketonates is accompanied by the formation of a protonated complex; for -organylthioacetylacetonates, annihilation follows the inhibition mechanism.