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931.
Pseudoelement Compounds. VIII. [1]. On the Coordination Behaviour of Potential Ambidentate Aryl-cyanamidosulfonate Ligands Aryl-cyanamidosulfonates form with metal(II) ions (Co, Ni, Cu, Zn, Cd, Hg, Pd, Pt) complexes of the types MX2, [MX2L2], [MX2L4] and [MX4]2?. The ionic, potentially ambidentate ligand [RSO2NCN]? is monodentately coordinated via the terminal nitrogen atom and bidentately in a bridging function through the nitrile group end-on (equatorial) and one of the two sulfonyl oxygen atoms (axial). The new compounds are characterized by means of ir and uv-vis spectroscopy. In the case of [Ni(NCNSO2C6H4Me-4)2(py)4] the molecular and crystal structure was determined. 相似文献
932.
933.
A. V. Kurkin V. V. Nesterov A. V. Karchava M. A. Yurovskaya 《Chemistry of Heterocyclic Compounds》2003,39(11):1466-1477
A new approach has been proposed to the synthesis of indole derivatives containing a chiral substituent at the nitrogen atom, comprizing Fischer indolization of phenylhydrazines with a chiral substituent at the -nitrogen atom. The initial hydrazines were obtained by the alkylation (Mitsunobu reaction applying optically active esters of lactic acid) of anilines containing an electron-accepting substituent at the amino group. Subsequent removal of the activating acceptor grouping was realized by nitrosation of the chiral secondary aniline followed by reduction of the corresponding N-nitroso compound. 相似文献
934.
Yoichi M.A Yamada 《Tetrahedron》2004,60(18):4097-4105
The efficient heterogeneous Heck reaction was achieved by a new networked and supramolecular catalyst PdAS-V (1b). Employing of PdAS-V in 5.0×10−5 mol equiv. efficiently progressed the heterogeneous Heck reaction of a series of aryl iodides with acrylates, styrenes and acrylic acid. PdAS-V was successfully recycled five times without any decrease in its activity, and showed good stability in toluene and water, and hence the Heck reaction was efficiently performed in both reaction media. The use of 8.0×10−7 mol equiv. of PdAS-V resulted in the coupling product in 92% yield with the turnover number (TON) and the turnover frequency (TOF) of PdAS-V reached up to 1,150,000 and 12,000, respectively. The efficient synthesis of resveratrol was achieved via the PdAS-V-promoted Heck reaction. 相似文献
935.
《Electroanalysis》2003,15(9):787-796
The use of [Cu(bipy)2]Cl2?6H2O as a biomimetic catalyst in the construction of an amperometric sensor for dopamine determination is reported. The sensor was prepared modifying a glassy carbon electrode with a Nafion membrane doped with [Cu(bipy)2]Cl2?6H2O complex. The sensor presented a higher response in 0.25 mol L?1 phosphate buffer solution (pH 7.0), with an applied potential of ?50 mV (vs. SCE). In the optimized operational conditions, a linear response range between 35 and 240 μmol L?1, with a sensitivity of 2.02±0.07 nA l μmoL?1 cm?2 and detection limit of 8.0 μmol L?1 were typically observed for the sensor. The response time presented for this sensor was 0.5 s, presenting the same response for at least 40 successive measurements, with good repeatability (3.0%) expressed as relative standard deviation for n=6. The difference of the response between four sensor preparations was 4%. A detailed investigation about the sensor response for other sixteen phenolic compounds and interfering species were carried out. The sensor was applied in the determination of dopamine in pharmaceutical preparation with success. 相似文献
936.
937.
J.S. Yadav B.V. Subba Reddy A.K. Basak A.V. Narsaiah A. Prabhakar B. Jagadeesh 《Tetrahedron letters》2005,46(4):639-641
Baylis-Hillman acetates undergo SN2′ allylic substitution with indoles in the presence of 20 mol % of indium tribromide under mild conditions to afford a new class of substituted indoles in high yields with (E)-stereoselectivity. The stereochemistry of the products was assigned by various NMR experiments. 相似文献
938.
The interlaboratory variability in the quantification of adsorbable organically bound halogens (AOX) in industrially contaminated
soil is presented. Three consecutive rounds of a proficiency testing scheme, in which between 88 and 119 routine laboratories
participated, yielded relative reproducibility standard deviations between 7 and 20% at AOX contents between 10.9 and 268 mg
kg−1. Nineteen laboratories with established proficiency were invited to participate in the certification of the AOX content in
three soil reference materials meant for the internal quality control in analytical laboratories. The certified values are
(1349 ± 59) mg kg−1, (80 ± 7) mg kg−1 and (102 ± 8) mg kg−1, respectively. 相似文献
939.
940.
Improved quantification limits in chiral capillary electrochromatography by peak compression effects
The peak compression effect has been applied to improve quantification limits in chiral capillary electrochromatography (CEC). A stationary phase based on the chiral selector vancomycin (Chirobiotic V) was used for separations of the enantiomers of mianserin. By adding solvents with a low dielectric constant, e.g. 2-propanol or tetrahydrofuran, to the sample solution, peak compression could be induced. The plate numbers for the minor enantiomer increased from approximately 100,000 to 1.4-1.6 million plates/m, when the composition of the mobile phase was adjusted so that the analyte eluted within either one of two system zones originating from the sample solution. A 10-fold improvement in the quantification limit for the minor enantiomer was obtained compared to elution under non-focused conditions. 相似文献