Aminopyrazoles. Part 3. Synthesis of the novel ring systems pyrazolo[4′,3′:5,6]pyrido[2,3-b][1,5]benzoxazepine and [1,5]benzothiazepine

Two-step synthesis of the novel fused heterocycles pyrazolo[4′,3′:5,6]pyrido[2,3-b][1,5]benzoxazepine ( 8 ) and pyrazolo[4′,3′:5,6]pyrido[2,3-b][1,5]benzothiazepine ( 9 ) from the pyrazolo[3,4-b]pyridine derivative 1 is described.     

Effect of solvents on the selectivity of terbutylazine imprinted polymer sorbents used in solid-phase extraction

A solid-phase extraction sample preparation method using a molecularly imprinted polymer (MIP) selective for the triazine type pesticide terbutylazine has been developed. The method involves preconcentration from large volumes of water samples on a C18 disk coupled to selective clean-up on the MIP. The method has been optimised by studying the recovery and retention of terbutylazine and some other structurally related triazine derivates as a function of the selective washing solvent used. The effect of the water content of the selective washing solvent was also investigated on the recovery of the MIP. River water samples were analysed with the coupled technique, and efficient clean-up of the samples was observed.     

Structural and temperature effects in the high-performance liquid chromatographic enantioseparation of 1-(alpha-aminobenzyl)-2-naphthol and 2-(alpha-aminobenzyl)-1-naphthol analogs

The enantiomers of 1-(alpha-aminobenzyl)-2-naphthol and 2-(alpha-aminobenzyl)-1-naphthol analogs were separated isothermally on a cellulose-tris-3,5-dimethylphenyl carbamate-based chiral stationary phase (Chiralcel OD-H), at 10 degrees C increments in the range of 5-35 degrees C, using n-hexane/2-propanol/diethylamine as mobile phase. The mobile phase composition and temperature were varied to achieve baseline resolutions in a single chromatographic run. The dependence of the natural logarithms of selectivity factors, In alpha, on the inverse of temperature, 1/T, was used to determine the thermodynamic data of the enantiomers. The thermodynamic data revealed that all the compounds in this study separate via the same enthalpy-driven chiral recognition mechanism.     

Enthalpic Relaxation of 25Na2O·xTiO2·(75-x)SiO2 Glasses

The enthalpic relaxation of the title glasses, studied by differential scanning calorimetry, is well described by a mathematical model based on the stretched exponential relaxation function with the relaxation time proportional to the actual viscosity. The dependence of viscosity on temperature and the fictive temperature was expressed by Mazurin's approximation. The relaxation parameters obtained correlated significantly with the glass composition, indicating the changes in the structural of the TiO₂ role near a TiO₂ content of 3–4 mol%. This revised version was published online in August 2006 with corrections to the Cover Date.     

Efficient and selective hydration of nitriles to amides in aqueous systems with Ru(II)-phosphaurotropine catalysts

A simple and efficient synthesis of amides by selective hydration of aromatic and aliphatic nitriles is described. The catalysts are prepared in situ from easily available Ru-precursors and ligands using water as the solvent. The most active catalyst, is obtained from [RuCl₂(dmso)₄] and benzylated 1,3,5-triaza-7-phosphaadamantane. Of the 16 substrates examined, 92–99% conversions of 14 nitriles were achieved in one hour at reflux temperature.     

Design of a Vitamin B1‐Selective Electrode Based on an Ion‐Pair and Its Application to Pharmaceutical Analysis

Vitamin B₁‐selective electrodes with PVC membrane were developed that contain ion associates of vitamin B₁ with an inorganic anion, BiI₄^?, and an organic anion, brilliant yellow, as electrode‐active substances. The linearity ranges of the electrode function are 1.0×10^?5–1.0×10^?2 and 1.0×10^?4–1.0×10^?2 M, the electrode function slopes are 33.0±1.0 and 33.1±1.1 mV decade^?1, the detection limits are 5.5×10^?6 and 8.3×10^?5 M for BiI₄^? and brilliant yellow respectively. The working range of pH is 5–12. The efficiency of the use of electrodes for the vitamin B₁ content control in multivitamin pharmaceutical preparations was shown by direct potentiometry and potentiometric titration methods.     

Synthesis of aminomethylazetidines regioselective reactions of mesyloxymethylazetidinones with nucleophiles II

Two efficient methods have been developed for the synthesis of variously substituted 2‐aminomethylazetidine derivatives 5 by regioselective nucleophilic substitution of 4‐mesyloxymethylazetidin‐2‐ones 3 followed by reduction or by reduction of the appropriate 4‐oxo‐azetidine‐2‐carboxamides 7 . A novel ring transformation of 4‐oxoazetidine‐2‐carboxamides 7 into tetrahydroquinolines 16 by reaction with lithium aluminium hydride/aluminium trichloride has been investigated.     

Nitroxide bound beta-cyclodextrin: is there an inclusion complex?

236CDTIPNO, a derivative of the persistent free radical TIPNO (1,1-dimethylethyl 2-methyl-1-phenylpropyl nitroxide) covalently bound to a permethylated-beta-cyclodextrin, was prepared. Self-association of 236CDTIPNO in water was proved by solvent- and competition-dependent EPR spectroscopy experiments with 2,6-di-O-Me-beta-cyclodextrin (DIMEB) and permethylated-beta-cyclodextrin (TRIMEB) as external hosts competing for accommodation of the TIPNO moiety. Temperature-dependent EPR spectra were simulated with a novel two-dimensional (field-temperature) EPR simulation program that afforded a full determination of the thermodynamic parameters characterizing the rate constants of the self-inclusion reaction derived from Arrhenius and Eyring models. This method allows separating the line broadening effects due to relaxation from a chemical exchange, even if only the fast exchange regime is accessible experimentally. The activation parameters for the forward and backward steps were consistent with an equilibrium between a nonassociated form and a weakly associated form, with activation free enthalpies for each reaction of around 34 kJ.mol(-)(1).