The thermolysis of 1,2-dialkynylimidazoles in benzene solution affords high yields of 7-phenyl-5H-cyclopentapyrazines, which presumably form by solvent trapping of cyclopentapyrazine carbene intermediates. In cases where dialkynylimidazole contains side chains that can participate in intramolecular carbene C-H insertion or olefin addition, these processes compete with solvent addition to afford novel tri- and tetracyclic pyrazines, which can be obtained in good yield when the thermolysis is carried out in hexafluorobenzene. 相似文献
Molecules of the form Cp(6,6-dmch)ZrX(2) (Cp = eta(5)-cyclopentadienyl, X = Cl, Br, I; 6,6-dmch = eta(5)-6,6-dimethylcyclohexadienyl) have been synthesized, and the molecular and electronic structures have been investigated. These molecules allow direct comparison of the bonding and properties of pentadienyl and cyclopentadienyl ligands in the same high-oxidation-state metal complexes. Unlike the well-known Cp(2)ZrX(2) analogues, these Cp(6,6-dmch)ZrX(2) molecules are intensely colored, indicating significantly different relative energies of the frontier orbitals. Also unusual, the average Zr-C distances to the 6,6-dmch pentadienyl ligand are about 0.1 A longer than the average Zr-C distances to the cyclopentadienyl ligand for these Zr(IV) complexes, opposite of what is observed for the Zr(II) complex Cp(2,6,6-tmch)Zr(PMe(3))(2) (tmch = eta(5)-2,6,6-trimethylcyclohexadienyl), reflecting a dramatic reversal in the favorability of the bonding depending on the metal oxidation state. The experimental and computational results indicate that the color of the Cp(6,6-dmch)ZrX(2) complexes is due to a 6,6-dmch ligand-to-metal charge-transfer band. Compared to the Cp(2)ZrX(2) analogues, the Cp(6,6-dmch)ZrX(2) molecules have a considerably less stable HOMO that is pentadienyl-based and an essentially unchanged metal-based LUMO. Also, the lowest unoccupied orbital of pentadienyl is stabilized relative to cyclopentadienyl and becomes a better potential delta electron acceptor, thus contributing to the differences in structure and reactivity of the low-valent and high-valent metal complexes. 相似文献
Summary Amperometric ascorbimetric determinations of cerium(IV) and ferric iron have been carried out at 50°C with two polarized electrodes at 200 and 100 mV respectively. The results obtained are fairly accurate and precise within ±1.0 per cent. A simple method for successive determination of cerium and iron has been developed; and conditions for such estimations have been established. At an acidity of 2.5 M with respect to sulphuric acid, it is possible to ward off the reduction of ferric iron and thereby cerium(IV) is successfully titrated with ascorbic acid in this medium. After completion of the reaction and then lowering the acid concentration to pH 1.5 with aid of ammonium hydroxide, FeIII is titrated with standard ascorbic acid yielding good results. 相似文献
A novel high-performance thin-layer chromatographic (HPTLC) analytical method has been developed and optimized for the quantification of quetiapine fumarate (QF) and its two genotoxic impurities in drug substance and drug product. The desired separation was achieved on 60F254 pre-coated HPTLC plates using combination of green solvents, ethyl acetate‒ethanol‒n-heptane (5:1:4, V/V) as developing solvents. The detection wavelength used for quantification was 229 nm. QF and its two related genotoxic impurities, namely, 2-chloroaniline and 2-aminodiphenylsulfide, were well resolved from one another with retention factor values of 0.13 ± 0.02, 0.57 ± 0.02 and 0.76 ± 0.02, respectively. The optimized method was validated according to the guidelines laid down by the International Council for Harmonisation. The linearity was determined in the range of 100–600 ng/spot for QF and 10‒60 ng/spot for its two related genotoxic impurities; R2 ≥ 0.993. The method exhibited precision along with good accuracy, where 0.51, 0.86 and 1.86. The percentage recoveries obtained for 2-chloroaniline and 2-aminodiphenylsulfide were 99.04‒101.04%. The developed method can be successfully used for the analysis of drug samples.
In this study, we report a copper-catalyzed ligand-free Cadiot–Chodkiewicz coupling reaction. No additives or ligands are required for this Cu-catalyzed C(sp)–C(sp) coupling reaction of terminal alkynes with alkynyl halides. The low cost of copper catalyst, excellent yield of the products, suppression of side-products and mild reaction conditions are the major advantages of this protocol. 相似文献
Three different types of iron(III) complexes, Fe(A)3, Fe(A)2(A') and Fe(A)(A')2, whereA is either piperidyldithiocarbamate or morpholyl dithiocarbamate andA' is glycine(oxine) acetylacetone have been prepared by reacting Fe(III) salt with sodium salt of piperidinedithiocarbamic acid or morpholine-dithiocarbamic acid and acetylacetone(oxine)-glycine in different ratios. The mixed ligand complexes have been characterised by elemental analysis, magnetic susceptibility measurements, infrared, electronic spectral techniques and by thermal analysis. Electronic spectral studies suggests that all the complexes possess distorted octahedral geometry. The magnetic moment of the high spin iron(III) complexes lies in the range of 5.88–6.00 and for low spin lies in the range of 3.36–4.34 B.M. TG studies show one step decomposition of complexes and formation of Fe2O3 at the end of the step. 相似文献
A dry media procedure has been developed for the synthesis of a series of new class of pyrazolo [4,3-c][1,5]benzothiazepines 6 under microwave irradiation using montmorillonite K10 as solid support. The catalyst can be recovered and reused. Thus, the procedure provides a simple and green synthetic methodology under environmentally friendly conditions. Antifungal screening of synthesized compounds has shown promising activity. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. 相似文献
Abstract— An action spectrum of the relaxation of supercoied plasmid DNA(induction fo the firt single-strand break) by photoactivated 4'-aminomethyl-4, 5',8-trimethylpsoralen(AMT) has been determined using monochormatic UV photons from 254 to 405 nm. The spectrum of AMT-induced plasmid DNA relaxation fits closely with the absorbance spectrum of AMT in the spectral region between 313 nm and 405nm but deviates at wavelengths shorter than 313nm. This asay also reveals that the psoralen photosensitization reaction with DNA also produces piperidinelabile sites. Addition of mannitol and azide partially quenches the supercoil realaxation reaction, evidence for a role of Type II photosensitization pathway. 相似文献