Interaction of 1-vinylpyrazoles with alkanethiols

It was found that vinylpyrazoles react with thiols both according to ionic and according to free-radical mechanisms, with the formation of products of - and -addition. Radical thiylation of 1-vinylpyrazoles is a convenient method of synthesis of pyrazoles with sulfur-containing substituents.Institute of Organic Chemistry, Siberian Branch, Russian Academy of Sciences, 664033 Irkutsk. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 8, pp. 1874–1878, August, 1992.     

Calculations for photoelectron spectra of azoles by the AM1 method using a green's function approximation for the outer valence molecular orbital

We have carried out nonempirical (4–31G) and semiempirical (MNDO and AM1) calculations for pyrazole, imidazole, and their 1-vinyl derivatives. The SCF calculations significantly overestimate the value of the orbital energy for n-type MO's. For the 1-vinylpyrazole molecule, all the methods incorrectly give the sequence of energy levels. The best agreement with experimental ionization potentials is obtained when using a Green's function approximation for the outer valence MO's together with the AM1 method.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 6, pp. 716–719, November–December, 1989.     

Azulene‐substituted pyranylium salts. Syntheses and products characterization

The synthesis of 4‐azulene‐substituted 2,6‐diphenyl‐ and 2,6‐dimethyl‐pyranylium salts and 2‐azulenesubstituted 4,6‐dimethyl‐pyranylium salts by nucleophilic substitution at pyranylium moiety with various azulenes was studied. The starting materials for 2,6‐diphenyl derivatives were 4 chlorinated pyranylium salts. They were obtained by the halogenation with PCl₅ of corresponding pyranones and were used either in situ or after separation. For the synthesis of dimethyl derivatives the corresponding pyranones were treated with POCl₃ and the resulted intermediate was reacted in situ with azulene. In the aim to study the influence of dihedral angle between azulene and pyranylium planes on the recorded spectra, both moieties were adequately substituted. The obtained results were in accord with the calculated values.     

Pyranylium Salts as Synthones in the Synthesis of Substituted Benzenes

Starting from 4-(azulen-1-yl)-pyranylium perchlorates, several azulenyl-substituted phenols as well as nitrobenzene and acetophenone derivatives were synthesized. The products were characterized, and the correlations between the compound structures and NMR spectra were investigated.     

Azulene‐substituted pyridines and pyridinium salts. Synthesis and structure. 1. Azulene‐substituted pyridines

4‐Azulen‐1‐yl substituted 2,6‐dimethyl‐and 2,6‐diphenyl‐pyridines are obtained in good yields from the reaction of corresponding 4‐azulen‐1‐yl‐pyranylium salts and ammonium acetate in ethanol or starting from 4‐chloro‐2,6‐diphenyl‐pyranylium salts in two steps: reaction with azulenes followed by in situ treatment with ammonium acetate. The effect of substitution at the 3‐position of the heterocycle was taken into account. The structure assignment was accomplished with NMR and uv‐vis spectra.     

Azulene‐substituted pyridines and pyridinium salts. Synthesis and structure. 2. Azulene‐substituted pyridinium salts

4‐Azulen‐1‐yl substituted 2,6‐dimethyl‐and 2,6‐diphenyl‐pyridinium salts are obtained in yields between 50 % and 100 % in the reaction of corresponding 4‐azulen‐1‐yl‐pyranylim salts and various amines. The effects of amine structure and of substitution in the heterocycle or at azulene moieties on the synthesis have been investigated. The uv‐vis and NMR spectra of reaction products are examined and discussed in correlation with their structure.     

Numerical study of the laminar flame propagation in ethane-air mixtures

The structure of premixed free one-dimensional laminar ethane-air flames was investigated by means of numerical simulations performed with a detailed mechanism (GRI-Mech version 3.0) by means of COSILAB package. The work provides data on ethane-air mixtures with a wide range of concentrations ([C₂H₆] = 3.0–9.5 vol.%) at initial temperatures between 300 and 550 K and initial pressures between 1 and 10 bar. The simulations deliver the laminar burning velocities and the profiles of temperature, chemical species concentrations and heat release rate across the flame front. The predicted burning velocities match well the burning velocities measured in various conditions, reported in literature. The influence of initial concentration, pressure and temperature of ethane-air mixtures on maximum flame temperature, heat release rate, flame thickness and peak concentrations of main reaction intermediates is examined and discussed.      

Hybrid macromolecular antioxidants based on hydrophilic polymers and sterically hindered phenols

A novel class of biologically active substances was created. These are hybrid macromolecular antioxidants (HMAO) based on hydrophilic polymers with chemically grafted sterically hindered phenols with different structural parameters. The antiradical activities of HMAO were assessed in reactions with 2,2-diphenyl-1-picrylhydrazyl and the corresponding sodium sulfonate in various solvents. The mechanism that explains the substantially enhanced activities of HMAO in water was proposed. The state of HMAO in solutions was studied by viscosimetry and photon correlation spectroscopy. HMAO were assayed in biological models. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 751–760, April, 2007.     

Synthesis and biological activity of metal chitosan complexes

A series of complexes of chitosans of various molecular weights (3000–150000) with copper, iron(II), and zinc sulfates were examined. Participation of amino groups of the polymer in coordination bonding with the metal was proved by IR spectroscopy. The affinity of chitosan for iron ions was enhanced by introducing phenolic fragments into the polymer.