Chemistry of benzo[b]furan. V.. Synthesis of substituted thia-analogs and oxa-analogs of dihydrorutecarpine and evodiamine

Cycloaddition of 3,4-dihydrobenzo[b]thieno[2,3-c]pyridine ( 6 ) with the sulfinamide anhydride 9 (R = H) afforded the thia-analog of dihydrorutecarpine ( 2a ). Condensation of the imine 6 with the sulfinamide anhydride 9 (R = CH₃) gave the thia-analog of evodiamine ( 2b ). Starting from 1-methyl-3,4-dihydrobenzo[b]thieno[2,3-c]pyridine ( 12 ) and 1-methyl-3,4-dihydrobenzo[b]furo[2,3-c]pyridine ( 14 ), a series of 3-methyl derivatives of thia-analogs of dihydrorutecarpine and evodiamine ( 2c-2i ) and oxa-analogs of dihydrorutecarpine and evodiamine ( 1a-1g ) were similarly prepared.     

Radiochemical separation of99Mo from natural uranium irradiated with thermal neutrons

⁹⁹Mo was separated from uranium and insoluble fission product hydroxides. More than 98% of⁹⁹Mo radioactivity was extracted with bis (2-ethylhexyl)phosphoric acid. The organic phase was washed and⁹⁹Mo was back-extracted from the organic phase with NH₄OH solution. The percent recovery from the organic phase was 91% and the purity of⁹⁹Mo was more than 99%. Pure^99mTc was also extracted from the organic phase with a saline solution. Reversed-phase partition chromatography was used for the purification of⁹⁹Mo from¹³¹I and other fission products (10% HDEHP on kieselguhr bed).¹³¹I and other isotopes were quantitatively eluted with 0.1M H₂SO₄,⁹⁹Mo was eluted using a mixture of 0.5 M HCl and 30% H₂O₂.     

Selenium heterocycles. XLI . Syntheses of substituted thiazolo,selenazolo, 1,2,3-thiadiazolo and 1,2,3-selenadiazoloquinolines

The reaction of thionyl chloride with the semicarbazone 2 gave 4,5-dihydro[1,2,3]thiadiazolo[4,5-f]quinoline. Selenium dioxide oxidaion of compound 2 gave 4,5-dihydro[1,2,3]selenadiazolo[4,5-f]quinoline ( 4 ) and the aromatic analog 5 . Thermolysis of compound 5 yielded [1,4]diselenino[2,3-f:5,6-f′]diquinoline ( 6 ). Reaction of selenourea with α-bromoketone 7 gave 2-amino-4,5-dihydroselenazolo[4,5-f]quinoline ( 8 ). Compounds 9 and 10 were prepared from the reaction of selenobenzamide and thiobenzamide with compound 7 .     

Thermoanalytical study of linkage isomerism in coordination compounds: Part I. Reinvestigation of thermodynamic and thermokinetic of solid state interconversion of nitrito (ONO) and nitro (NO2) isomers of pentaaminecobalt(III) chloride by means of DSC

Solid state thermal isomerization of [Co(NH₃)₅(ONO)]Cl₂ (nitrito isomer) to [Co(NH₃)₅(NO₂)]Cl₂ (nitro isomer) and reverse reaction were investigated by non-isothermal differential scanning calorimetry (DSC) and found to be essentially an equilibrium process. The interconversions are accelerated at above 65 °C and reach to equilibrium state at about 155 °C. After establishment of the equilibrium the relative amounts of two isomers at any temperature are governed by Gibbs free energy relationship. The experimental enthalpy changes of isomerization of pure nitrito and nitro solid samples to the equilibrium state are −4.67 (±0.19) and 0.99 (±0.05) kJ mol⁻¹, respectively. From these values, total enthalpy change was calculated as: ΔH°=−5.66(±0.20) kJ mol⁻¹. Using Gibbs free energy relationship, equilibrium constant, total free energy and entropy changes were estimated at 60 °C as: K=7.72(±0.8),  kJ mol⁻¹ and  J K⁻¹ mol⁻¹.An initial rate method has been developed to determine the kinetic parameters of these reactions from non-isothermal DSC data. Both nitro to nitrito and reverse reactions obey first order kinetic law in solid state. Estimated activation parameters of forward and reverse paths at 60 °C are , , and , respectively. The negative activation entropy of both directions support the intramolecular mechanism of isomerization, including formation of a seven coordinate transition state, which formerly suggested based on spectral and X-ray methods.     

Spectrophotometric determination of beryllium in water samples after micelle-mediated extraction preconcentration

A new micelle-mediated phase preconcentration method for preconcentration of ultra-trace quantities of beryllium as a prior step to its determination by spectrophotometry has been developed. Chrome Azurol S (CAS) and cetyltrimethylammonium bromide (CTAB) were used as chelating agent and cationic surfactant, respectively. The method evaluates and eliminates the blank bias error present in such procedures using mean centering of ratio spectra. This procedure gives more accurate results than the traditional approach using absorbance values against reagent blank. The optimal extraction and reaction conditions were studied and the analytical characteristics of the method (e.g., limit of detection, linear range, preconcentration and improvement factors) were obtained. Linearity was obeyed in the range of 0.9-18.0 ng mL⁻¹ (1.00 × 10⁻⁷-2.00 × 10⁻⁶ mol L⁻¹) of beryllium. The detection limit of the method is 0.51 ng mL⁻¹ (5.66 × 10⁻⁸ mol L⁻¹) of beryllium. The interference effect of some anions and cations was also tested. The method was applied to the determination of beryllium in spring water samples.     

Structural characterization of nickel oxide nanowires by X-ray absorption near-edge structure spectroscopy

Nickel oxide nanowires modified by poly(vinylpyrrolidone) (PVP) were synthesized via a simple chemical pattern. For the first time NiO nanowires with diameters ranging from 40 to 100 nm with the expected ratio (length vs diameter) ranging from 54 to 90 were grown using a simple solution-phase approach (mild method). These nickel nanowires exhibited unique photoluminescence features and displayed a significant UV luminescence. X-ray absorption near-edge spectroscopy has been used to characterize the local Ni environment and identify the electronic structure. Comparing experimental and theoretical spectra at the Ni and O K edges, we determine the lattice distortion via the analysis of the characteristic preedge features and the multiple-scattering structures detected in the X-ray absorption near-edge structure spectra. The correlation between experimental features and the disordered or distorted local structures is also discussed.     

Synthesis of 3-formylbenzo[b]furan and 1-methyl-3,4-dihydrobenzo[b]-furo[2,3-c]pyridine

Starting from the readily available 3-methylcoumarilate, 3-formylbenzo[b]furan was synthesized in high yield. The latter could be converted to 1-methyl-3,4-dihydrobenzo[b]furo-[2,3-c]pyridine in moderate yield.     

Simultaneous kinetic spectrophotometric determination of cyanide and thiocyanate using the partial least squares (PLS) regression

The partial least squares (PLS-1) calibration model based on spectrophotometric measurement, for the simultaneous determination of CN⁻ and SCN⁻ ions is described. The method is based on the difference in the rate of the reaction between CN⁻ and SCN⁻ ions with chloramine-T in a pH 4.0 buffer solution and at 30 °C. The produced cyanogen chloride (CNCl) reacts with pyridine and the product condenses with barbituric acid and forms a final colored product. The absorption kinetic profiles of the solutions were monitored by measuring absorbance at 578 nm in the time range 20-180 s after initiation of the reaction with 2 s intervals. The experimental calibration matrix for partial least squares (PLS-1) calibration was designed with 31 samples. The cross-validation method was used for selecting the number of factors. The results showed that simultaneous determination could be performed in the range 10.0-900.0 and 50.0-1200.0 ng mL⁻¹ for CN⁻ and SCN⁻ ions, respectively. The proposed method was successfully applied to the simultaneous determination of cyanide and thiocyanate in water samples.     

Synthesis and calcium channel antagonist activities of new derivatives of dialkyl 1,4-dihydro-2,6-dimethyl-4-(5-phenylisoxazol-3-yl)pyridine-3,5-dicarboxylates

The new analogues of nifedipine, in which 2-nitrophenyl group at position 4 is replaced by phenylisoxazolyl substituent, were synthesized. The symmetrical dialkyl 1,4-dihydro-2,6-dimethyl-4-(5-phenylisoxazol-3-yl)pyridine-3,5-dicarboxylates were prepared by classical Hantzsch condensation, and the asymmetrical analogues were synthesized using a procedure reported by Dagnino that involved the condensation of alkyl acetoacetate with alkyl 3-aminocrotonate and 5-phenylisoxazole-3-carboxaldehyde. The structure of all compounds was confirmed by IR, ¹H NMR and Mass spectra. In vitro calcium channel antagonist activities were evaluated as calcium channel antagonists using the high K⁺ concentration of guinea-pig ileum longitudinal smooth muscle (GPILSM) assay. These compounds exhibited moderate calcium antagonist activity (IC₅₀ = 10^?7 to 10^{? 5} M range) relative to the reference drug nifedipine (IC₅₀ = 1.10 ± 0.40 × 10^?8 M).