Liquid-phase chlorination ofC-chlorovinylsilanes

Liquid-phase chlorination of a number of chloro(chlorovinyl)methylsilanes was investigated. A number of novelC-chlorosilanes were characterized by IR and¹H NMR spectra. Some regularities of these reactions were determined; correlations between the structure of chloro(chlorovinyl)methylsilanes and their reactivities were identified.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2256–2260, November, 1995.     

Direct atomic-absorption determination of the Ni and V content in oil

A direct (without sample pretreatment) atomic-absorption method of V and Ni determination in oil with electrothermal atomization and Zeeman correction of background was developed.     

Diastereoselective synthesis of 1-α-phenylethyl-3,3-dimethyldiaziridine. Conformation and configuration of three-membered ring nitrogen heterocycles containing an asymmetric substituent on the nitrogen atom

The synthesis of 1-(S)--phenylethyl-3,3-dimethyldiaziridine from N-(S)--phenylacetonimine and hydroxylamine-O-sulfonic acid has been carried out with high diastereoselectivity. The absolute configuration of the diastereomers was established by comparison with oxaaziridine analogs based on their NMR and CD spectra, and atom-atomic potential calculations. A test has been proposed to establish the absolute configuration of N--phenylethyl-substituted three-membered ring heterocycles using NMR, and the mechanism of epimination of imines is discussed, which is similar to their oxidation mechanism.Communication 60 in the series Asymmetric Nitrogen; for Communication 59, see [1].Translated from Geterotsiklicheskikh Soedinenii, No. 11, pp. 1461–1465, November, 1988.     

Push-Pull Structures Based on 2-Aryl/thienyl Substituted Quinazolin-4(3H)-ones and 4-Cyanoquinazolines

Design and synthesis of 2-(aryl/thiophen-2-yl)quinazolin-4(3H)-ones and 4-cyano-2-arylquinazolines with Et₂N-, Ph₂N- or carbazol-9-yl- electron donating fragment are described. The key photophysical properties of these compounds have been studied by UV/Vis absorption and fluorescence spectroscopy in solvents of different polarity (toluene and MeCN). 2-(Aryl/thiophen-2-yl)quinazolin-4(3H)-ones show fluorescence in blue-green region in toluene solution with quantum yields up to 89% in the case of 2-(4’-N,N-diphenylamino[1,1’-biphenyl]-4-yl)-quinazolin-4(3H)-one. Moreover, triphenylamino derivative based on quinazolin-4(3H)-one with para-phenylene linker displays the highest quantum yield of 40% in powder. The fluorescence QY of Et₂N and Ph₂N derivatives decrease when going from toluene to MeCN solution, whereas carbazol-9-yl counterparts demonstrate strengthening of intensity that emphasizes the strong influence of donor fragment nature on photophysical properties. 4-Cyanoquinazolines are less emissive in both solvents, as well as, in solid state. The introduction of cyano group into position 4 leads to orange/red colored powder and dual emission bands. Some molecules demonstrate the increase in emission intensity upon addition of water to MeCN solution. According to frontier molecular orbitals (HOMO, LUMO) calculations, the energy gap of 4-cyanoquinazoline decreases by more than 1 eV compared to quinazolin-4-one, that is consistent with experimental data.     

Synthesis of New Fluorinated Derivatives of Quinolinecarboxylic Acids

Ethyl esters of 1-(7-Z-1-ethyl-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carbamoyl)-5-X-6,7,8-trifluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic acids (X = H, F; Z = pyrrolidino-, piperidino-, hexamethylenimino-, morpholino-, thiomorpholino-) have been synthesized by the interaction of quinolone-3-carboxylic acid hydrazides with ethyl esters of 3-ethoxy-2-(polyfluorobenzoyl)acrylic acid . It was shown possible to cyclize intramolecularly the esters obtained with the formation of 1,3,4-oxadiazino[6,5,4-i,j]quinoline derivatives.     

Mechanism of the oxidative carbonylation of terminal alkynes at the ≡C-H bond in solutions of palladium complexes

The formation mechanism of the active catalyst in the oxidative carbonylation of terminal alkynes at the ≡C-H bond has been investigated for the catalytic system Pd(OAc)₂-PPh₃-p-benzoquinone (Q)-MeOH. It has been demonstrated by NMR spectroscopy, X-ray crystallography, and kinetic measurements that the catalytically active palladium is in the oxidation state 0 and is bound into complexes stabilized by p-benzoquinone (PdL₂Q, where L = PPh₃). A mechanism is suggested for the catalytic process, which includes the formation of the complex PdL₂Q, the oxidative addition of the alkyne to this complex at the ≡C-H bond, the insertion of CO into the Pd-C bond, and steps in which hydride hydrogen is intramolecularly transferred to the p-quinone.     

Pericyclic reactions in the synthesis of new 5-aryl-5,6-dihydroquinolino[2,1-b]quinazolin-12-ones

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Fluorinated 1,3-benzothiazin-4-ones containing fluoroquinolone fragment

Chemistry of Heterocyclic Compounds - We have developed an efficient synthetic approach to potential antibacterial agents with double mechanism of action through the combination of antibacterial...     

A highly efficient white-light-emitting diode based on a two-component polyfluorene/quantum dot composite

Organic light-emitting diodes (OLEDs) are attracting great interest of the scientific community and industry because they can be grown on flexible substrates using relatively simple and inexpensive technologies (solution processes). However, a problem in the fabrication of white OLEDs is that it is difficult to achieve a balance between the intensities of individual emission components in the blue, green, and red spectral regions. In this work, we try to solve this problem by creating a two-component light-emitting diode based on modified polyfluorene (PF-BT), which efficiently emits in the blue–green region, and CdSe/ZnS/CdS/ZnS semiconductor quantum dots emitting in the orange–red region with a fluorescence quantum yield exceeding 90%. By changing the mass ratio of components in the active light-emitting composite within 40–50%, it is possible to transform the diode emission spectrum from cold to warm white light without loss of the diode efficiency. It is very likely that optimization of the morphology of multilayer light-emitting diodes will lead to further improvement of their characteristics.     

Structural trends of 29Si–1H spin–spin coupling constants across double bond

The calculations of geminal and vicinal ²⁹Si–¹H spin–spin coupling constants across double bond in 15 alkenylmethylsilanes and alkenylchlorosilanes were carried out at the second‐order polarization propagator approach level in a good agreement with experiment. Two structural trends, namely, (i) the geometry of the coupling pathway and (ii) the effect of the electrowithdrawing substituent, have been interpreted in terms of the natural J‐coupling analysis within the framework of the natural bond orbital approach. Thus, the marked difference between cisoidal and transoidal ²⁹Si–¹H spin–spin coupling constants across double bond was accounted for the delocalization contributions including bonding and antibonding Si–C and C–H orbitals, whereas the chlorine effect was explained in terms of the steric contributions including bonding Si–Cl orbitals. Copyright © 2012 John Wiley & Sons, Ltd.