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61.
Arturo Zizumbo Rosa Maria Félix-Navarro Jorge Cervantes-Jáuregui Felípe Avalos-Belmontes 《Silicon Chemistry》2005,2(5-6):265-269
Electrochemical formation of poly(phenylmethylsilane) in a divided cell containing a Teflon® neutral membrane was studied. The electrolysis of dichlorosilanes was carried out in a solution containing tetrahydrofuran + hexamethylphosphoramide as the solvent, tetrabutylammonium perchlorate as the support electrolyte and stainless steel as the cathode, with Pt and graphite as the resistant anodes or stainless steel as the sacrificial anode. Polysilanes with a number-average molecular weight in the range from 2,600 to 130,000 g/mol were obtained, depending on the conditions used. 相似文献
62.
Jorge A. R. Alarcon A. T. Soldatenkov S. A. Soldatova Alicia U. Samalloa Juan U. Obando N. S. Prostakov 《Chemistry of Heterocyclic Compounds》1993,29(9):1054-1058
2,3,8,9-Tetramethoxy-11-phenyldibenz[2,3;7,8]indolizine was obtainedinhighyieldfrom (6,7-dimethoxyisoquinolin-1-yl)-(3,4-dimethylphenyl)phenylcarbinol by cyclization in the presence of formic acid. The behavior of (6,7-dimethoxyisoquinolin-1-yl)-(3,4-dimethoxyphenyl)methylcarbinol and (6,7-dimethoxyisoquinolin-1-yl-(3,4-dimethoxyphenyl)carbinol was studied under these same conditions. 2,3,7,8-Tetramethoxy-11-phenyl-5,6-dihydrodibenz[2,3;7,8]indolizine was obtained by hydrogenation on rhenium heptasulfide.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1233–1238, September, 1993. 相似文献
63.
A phytochemical investigation in plantlets of the Brazilian medicinal tree Virola surinamensis resulted in the isolation and structural determination of four new compounds: 3-hydroxy-4-methyl-2-(11'-piperonyl-n-undecyl)-butenolide; 3-hydroxy-4-methyl-2-(7'-piperonyl-n-heptyl)-butanolide; 9'-(3,4-methylenedioxy-phenyl)-nonanoic acid and 13'-(3,4-methylene-dioxyphenyl)-tridecanoic acid. Thirteen compounds previously isolated from seeds and adult plants were also reported. 相似文献
64.
Jorge M. Pinheiro M. Isabel Ismael J. Albertino Figueiredo Artur M. S. Silva 《Journal of heterocyclic chemistry》2004,41(6):877-882
This work reports the synthesis of isoxazoles linked to sugar derivatives in different positions of furanosidic rings, by intramolecular oxidative cyclization of α,β‐unsaturated oximes with iodine, potassium iodide and sodium hydrogen carbonate. These oximes were obtained from aldehyde‐sugar derivatives. 相似文献
65.
Alvarez-Lueje A Valenzuela C Squella JA Núñez-Vergara LJ 《Journal of AOAC International》2005,88(6):1631-1636
In this work, a liquid chromatography stability-indicating method was developed and applied to study the hydrolytic behavior of simvastatin in different pH values and temperatures. The selected chromatographic conditions were a C18 column; acetonitrile-28 mM phosphate buffer solution, pH 4 (65 + 35) as the mobile phase; 251 degrees C column temperature; and flow rate 1 mL/min. The developed method exhibited an adequate repeatability and reproducibility (coefficient of variation 0.54 and 0.74%, respectively) and a recovery higher than 98%. Furthermore, the detection and quantification limits were 9.1 x 10(-7) and 2.8 x 10(-6) M, respectively. The degradation of simvastatin fitted to pseudo-first order kinetics. The degradation was pH dependent, being much higher at alkaline pH than at acid pH. Activation energy, kinetic rate constants (k) at different temperatures, the half life (t1/2) and the time for 10% degradation to occur (t90) values are also reported. 相似文献
66.
Jorge M.M. Verkade Peter J.L.M. Quaedflieg Floris L. van Delft 《Tetrahedron letters》2006,47(46):8109-8113
Mild and efficient procedures for deprotection of the amine nitrogen protecting p-methoxyphenyl (PMP) group are described. Periodic acid and trichloroisocyanuric acid (TCCA) were found to be particularly effective in realizing amine liberation using 1 and 0.5 equiv of the oxidant, respectively. Extension of the periodic acid-mediated conditions to simultaneous alcohol oxidation by combination with a catalytic amount of sodium dichromate led to smooth conversion of PMP-protected Mannich products into the corresponding β-amino acids in a one-pot procedure. 相似文献
67.
Garcia-Galdo JE Cobas-Rodriguez J Jáuregui-Haza UJ Guiochon G 《Journal of chromatography. A》2004,1024(1-2):9-14
This work presents a modification to the real adsorbed solution model using a Flory-Huggins type of expression that was reported previously. This modification consists in replacing the Flory-Huggins activity coefficient by the spreading pressure dependent approach. This new model takes into account explicitly the adsorbate-adsorbate interactions taking place in the adsorbed phase. It provides an excellent prediction of the competitive, ternary adsorption equilibrium of benzyl alcohol, 2-phenylethanol and 2-methyl benzyl alcohol observed in a reversed-phase liquid chromatographic system using information merely derived from the single-component adsorption experimental data. 相似文献
68.
Bismuth(III) salts are efficient catalysts for the selective allylic oxidation using tert-butyl hydroperoxide. BiCl3 is especially effective and can be easily recovered and reused as BiOCl. Using BiCl3/K-10 as catalyst, an increase in the reaction rate was observed. 相似文献
69.
Abstract— The triplet state characteristics (spectrum, lifetime and quantum yield) for four dye sensi tisers [methylene blue (MB), erythrosin (ER), haematoporphyrin (HP) and riboflavin (RF)] were determined in methanol by laser flash photolysis and singlet oxygen yields (0.60 to 0.48) from time-resolved measurements of the 1270 nm near infrared emission. The reaction of singlet oxygen with four long chain unsaturated phenyl esters [oleate (18: 1), linoleate (18: 2), linolenate (18: 3) and arachidonate (20: 4)] was followed quantitatively using the singlet oxygen luminescence technique and also, after continuous420–700 nm irradiation, by HPLC and other analysis of the isomeric product monohydroperoxides. The overall quantum yield of photooxidation (∼10-2 ) was shown to be consistent with the observed singlet oxygen quenching constants(2–12 times 104 dm3 mol-1 s-1 ) for the four esters studied and the singlet oxygen lifetime in methanol (τ∼ 9 μs). The isomer product distribution was interpreted in terms of a dual singlet oxygen and radical mechanism, the radical contribution increasing with sensitiser in the order ER = MB < HP ≪ RF, but also showing some dependence on substrate unsaturation. Evidence is presented for singlet oxygen quenching by MB and RF ( kO = 1.6 and 6.0 times 107 dm3 mol-1 s-1 ) and for the accelerated photobleaching of the dye sensitisers in the presence of the unsaturated esters. 相似文献
70.