Preparation and properties of silica gel with immobilized formazan group

A new sorption material, silica gel with covalently immobilized formazan group, was suggested and characterized. The material was prepared by coupling the immobilized aryldiazonium salt with benzaldehyde phenylhydrazone. The equilibrium and kinetic characteristics of the sorption of Cu(II), Co(II), Ni(II), and Cd(II) from solutions onto the modified silica gel were determined. The material proved to efficiently concentrate Cu(II) from multicomponent solutions. The coordination surrounding of Cu(II) in the complex on the sorbent surface was determined by ESR.     

Synthesis of sulfonamide derivatives of pyrido-[2,1-<Emphasis Type="Italic">b</Emphasis>]quinazolin-11-one and pyrido[1,2-<Emphasis Type="Italic">a</Emphasis>]quinazolin-6-one

Methods were developed of indirect introduction of sulfonamide group in the structures of pyrido-[2,1-b]quinazolin-11-one and pyrido[1,2-a]quinazolin-6-one underlain by cyclocondensation of 2-halo-5-(Rsulfamoyl) benzoyl chlorides with derivatives of 2-aminopyridine. The fact of thermal rearrangement of 8-(morpholin-4-ylsulfonyl)pyrido[1,2-a]quinazolin-6-one into isomeric 2-(morpholine-4-ylsulfonyl)pyrido[2,1-b]-quinazolin-11-one was experimentally registered.     

The kinetics of complex formation in the trithiadiazoletri[3,4-di(4-tert-butylphenyl)-pyrrole] macrocycle-copper(II) acetate-DMFA-H2O system

The paper presents the results of a study of the kinetics of coordination of a macroheterocyclic compound with an increased coordination cavity of the (3 + 3) McH₃ composition consisting of sequentially alternating 1,3,4-thiadiazole and 3,4-bis(4-tert-butylphenyl)pyrrole fragments to dehydrated Cu(OAc)₂ in dimethylformamide with and without H₂O admixtures. The reaction could be controlled spectrophotometrically over the salt and ligand concentration ranges (0.175?0.55) × 10^?4 and (0.16?0.64) × 10^?5 mol/l, respectively, at temperatures of 288–303 K. A kinetic equation of an unusual form with a negative order with respect to the salt was for the first time obtained experimentally for a macrocyclic ligand by the method of excess concentrations. The kinetics of the complex formation reaction was given a theoretical interpretation. Quantitative characteristics were obtained, and the role played by water in the kinetics of complex formation was studied. These data were of importance for practical applications, for the development of optimum conditions increasing the yield of complexes when they were synthesized in complex formation reactions.     

Physicochemical properties of 1,2-epoxycyclopentane

Temperature dependences of density, viscosity, and saturated vapor pressure of 1,2-epoxycyclopentane were studied and approximated by interpolation equations. Its refraction index and chromato-mass-spectroscopy data are given.

     

Condensation of 5-(4-methylphenyl)-2,4-dihydro-3H-1,2,4-triazole-3-thione with haloacetic acids

Reactions of triazolethiones with haloacetic acids were studied with 5-(4-methylphenyl)-2,4-dihydro-3H-1,2,4-triazole-3-thione as an example. It was proved for the first time by X-ray diffraction that the cyclocondensation of these compounds proceeds regiospecifically to give 2-(4-methylphenyl)[1,3]thiazolo[3,2-b][1,2,4]triazol-6(5H)-one rather than its isomer 3-(4-methylphenyl)[1,3]thiazolo[2,3-c][1,2,4]triazol-5(6H)-one.     

1 3C-1 3C Spin-Spin Coupling Constants in Structural Studies: XXXV. Stereochemical Study of the Furanose Ring

Theoretical conformational analysis and calculation of ^{1 3}C-^{1 3}C spin-spin coupling constants of aldofuranoses of the D-series were performed in terms of the self-consistent finite perturbation theory in the INDO approximation. All the examined furanoses were found to prefer an envelope conformation. The main factor responsible for the stereospecificity of the ¹ J1,2 coupling constant is mutual orientation of the hydroxy groups on C¹ and C²: s-trans isomers are characterized by greater ¹ J1,2 values (by 2-4 Hz) than the corresponding s-cis isomers.     

Complexes of Macroheterocyclic Compounds Derived from Substituted 1,2,4-Triazoles with Tetravalent Metals

Symmetrical marcoheterocyclic compounds derived from substituted 1,2,4-triazoles were reacted with tin(IV) and titanium(IV) chlorides to prepare the corresponding metal complexes. Macroheterocyclic compounds insoluble in organic solvents give mixtures of products on complex formation.     

Synthesis of 2<Emphasis Type="Italic">N</Emphasis>-Alkyl-substituted 5-Amino-3-imino-1,2,4-thiadiazolines

Conditions for an efficient and a readily reproducible synthesis of a series of 2N-Alkyl-substituted 5-amino-3-imino-1,2,4-thiadiazolines by the direct alkylation of 3,5-diamino-1,2,4-thiadiazole with alkyl bromides in fairly high yields (up to 76%).     

Synthesis of 3,5-disubstituted 4-aminoisoxazoles by cyclization of <Emphasis Type="Italic">O</Emphasis>-(β-oxoalkyl)-substituted α-hydroxyimino nitriles

4-Amino-5-benzoyl(acetyl)isoxazole-3-carboxamides were prepared by cyclization of α-hydroxyimino nitriles O-alkylated with bromoacetophenones (bromoacetone). The purity of the target 4-aminoisoxazoles can be substantially increased by treating O-alkylated oximes with LiClO₄ before cyclization. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1159–1165, May, 2005.     

Electronic spectra of quinoxaline 1-N-oxides

The nature of theπ→π ^* transitions in the spectra of quinoxaline 1-N-oxides as compared with unoxidized quinoxalines was examined on the basis of an experimental, study and calculation by the Pariser-Parr-Pople configurational interaction method.