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961.
Mária Mečiarová Janka Podlesná Štefan Toma 《Monatshefte für Chemie / Chemical Monthly》2004,135(4):419-423
Summary. Nucleophilic aromatic substitution reactions with imidazole of haloarenes having strongly electron-withdrawing groups were studied under ultrasonic and microwave irradiations. The course of the SNAr reactions was found to be strongly dependent on the electron-withdrawing properties of the substituents as well as on the leaving ability of the halogen atom. Microwave irradiation allowed to shorten the reaction time and to increase the yields compared with ultrasonic irradiation. 相似文献
962.
The reaction of 1-carbamoylmethyl-2,3,3-trimethyl-3H-indolium chloride with various aromatic aldehydes in acetic acid and the subsequent workup of the intermediate styrylic derivatives with strong bases yielded 9a-(2-arylethenyl)-1,2,3,9a-tetrahydro-9H-imidazo[1,2-a]indol-2-one derivatives. Condensation of the mentioned salt with salicylaldehyde in acidic or basic medium afforded the derivative of l-carbamoylmethylspiro[benzopyran-2,2-indole]. Alkylation of the latter compound with benzyl chloride in the presence of potassium hydroxide gave 9a-[2-(2-benzyloxyphenyl)ethenyl]-1,2,3,9a-tetrahydro-9H-imidazo[1,2-a]indol-2-one.Department of Organic Chemistry, Kaunas University of Technology, LT-3028 Kaunas, Lithuania Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 761–769, June, 2000. 相似文献
963.
Naphthalene catalyzed lithiation of 1,3-dimethyl-2-phenylimidazolidine led to cleavage of the benzylic carbon-nitrogen bond, with formation of an intermediate dianion. Under similar conditions, 1,3-dimethyl-2-(4-chlorophenyl)imidazolidine underwent regioselective cleavage of the aromatic carbon-chlorine bond, leading to a 4-formylphenyllithium equivalent, whilst 1,3-dimethyl-2-(4-methoxymethylphenyl)imidazolidine underwent regioselective cleavage of the benzylic carbon-oxygen bond, leading to a 4-formylbenzyllithium equivalent. 相似文献
964.
The 1,4-elimination reaction of 2-substituted-(2Z)-4-methoxy-O-alkenyl acetals with n-butyllithium is shown to afford the 2-substituted-(1Z,3E)-O-1,3-dienyl acetals in high stereoselectivities. The Ferrier reaction of the O-1,3-dienyl acetals thus obtained provides the corresponding α-quaternary-β,γ-unsaturated aldehydes in excellent yields with high α-regioselectivities. 相似文献
965.
Michael M. Pollard 《Tetrahedron》2006,62(51):11908-11915
This paper describes a convenient and high yielding three-step approach for the synthesis of trans-tetraphenylporphyrins possessing two thioethers in the ortho positions, which will facilitate the synthesis of more elaborate and complex porphyrin architectures. Their synthesis is realized by a double nucleophilic aromatic substitution of 2 equiv of a thiolate on 2,6-dichlorobenzaldehyde to generate a bis-thioether substituted benzaldehyde. This aldehyde is then condensed with 2 equiv of pyrrole to give a dipyrromethane, which in the final step reacts with an aromatic aldehyde to give a series of thioether-substituted trans-tetraphenylporphyrins. 相似文献
966.
Marc Montana 《Tetrahedron letters》2006,47(37):6573-6576
We report herein an original and rapid synthesis of new α-chloroketones in azaheterocyclic series based on TDAE strategy from the reaction between 2-(trichloromethyl)quinoxaline and aromatic aldehydes. This reactivity has been generalized to a quinolinic trichloride. 相似文献
967.
968.
Wei Liu Lin Ma Xu-Dong Sun Tian-Xiao Sun Yu-Hua Cheng Tie-Jin Li 《Applied biochemistry and biotechnology》1996,56(2):129-139
A fluorometric method for assaying the activity of horseradish peroxidase (HRP) in organic media has been developed. This
method is designed on the basis of the disparity in the spectral properties of substrates and corresponding resultant polymers.
It monitors the fluorescence quenching of substrate during enzymatic catalysis, and works efficiently in a number of organic
media (such as dioxanewater mixture, acetone-water mixture, and alcohol-water mixture, and so forth) toward many substrates.
This assay is simpler, more rapid, and more convenient compared with the commonly used HPLC method. It is qualitatively reproducible
and can also be used for quantitative calculation of the substrate conversion. 相似文献
969.
This article presents a thorough investigation of quantitative parameters for the analysis of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and polychlorinated dibenzofurans (PDBFs) partitioning between an octadecyl silica extraction membrane and microliters of an n-alkane solvent spiked on the surface of the membrane. Shpol'skii spectrometry is directly performed on the surface of the membrane with the aid of a cryogenic fiber optic probe. The analyte concentration in the layer of Shpol'skii solvent follows a linear relationship with the analyte concentration in the water sample and the same is observed for the phosphorescence signal of the cryogenic probe. The accuracy and precision needed for quantitative analysis in aqueous samples is demonstrated. The analytical figures of merit show the feasibility to determine organic pollutants at the parts-per-trillion level with minimum solvent consumption. 相似文献
970.
A study has been made of the effect of additives to the fuel of a turbulent diffusion flame on the formation of soot and polycyclic aromatic hydrocarbons (PAHs). Fuels containing a polystyrene thickener doped with benzene proved to have many advantages over unthickened fuels. Most significant were an increase in the burning time and the flash point. Nevertheless, polystyrene and benzene additives to a considerable extent increased the formation of soot and PAHs. The analysis of PAHs in this study was made by capillary gas chromatography (GC) and capillary gas chromatography/mass spectrometry (GC/MS). A total of 42 individual compounds were characterized by their retention indices and mass spectra. 相似文献