V. P. Andreev

Effect of pyridine and quinoline N-oxides on microsomal Na,K-ATPase activity

Some heteroaromatic N-oxides of pyridine and quinoline derivatives at concentrations ranging from 10−4 to 10−10 mole/liter inhibit Na,K-ATPase activity in cattle brain microsomes stronger than does strophanthin K (a drug used for the treatment of cardiac insufficiency). A new Na,K-ATPase activator, 2-(2,4-dimethoxystyryl)quinoline-N-oxide), has been found, which is capable of acting at concentrations within 10−6–10−9 mole/liter. Since these compounds activate the enzyme in very low concentrations, they can probably be effective for the treatment of some disorders involving violation of the Na,K-ATPase function.

New basicity/nucleophilicity scale on the basis of parameters of formation of axial n,ν-complexes derived from tetraphenylporphyrinatozinc(II) and base/nucleophile as ligand

The stability constants of complexes derived from tetraphenylporphyrinatozinc(II) and various ligands in chloroform at 25°C were proposed as nucleophilicity/basicity parameters of the latter, which reflect the effects of electronic and steric factors. Supernucleophilicity of heteroaromatic N-oxides in reactions with electrophiles was interpreted in terms of sp2–sp3 rehybridization of the N-oxide oxygen atom.

Change in the hybridization of the N→O group oxygen atom upon complex formation of pyridine and quinoline N -oxides with v-acceptors

It was shown on the basis of X-ray structural and NMR data that the (sp2→sp3) rehybridization of the oxygen atom of the N→O group can take place in reactions of heteroaromatic N-oxides with Lewis and Bronsted-Lowry acids. The hybridization type depends on the ligand and acceptor natures, composition of a complex, and spatial stresses arising during the complex formation.

Quantitative relations holding in coordination of (Tetraphenylporphyrinato)zinc(II) and nucleophilic substitution with anilines

Thermodynamic parameters (ΔG°, ΔS°) of quasi-isoenthalpic coordination of (tetraphenylporphyrinato) zinc(II) with anilines (except for 4-halo derivatives) in chloroform at 273–313 K in the absence of steric factors are linearly related to shifts of their absorption bands in the electronic spectra in reactions with anilines, as well as with logarithms of the stability constants of the complexes, pKa values of the ligands in water, and Hammett substituent constants σ+. Linear relations were also found between thermodynamic and kinetic parameters of some nucleophilic substitution reactions and complex formation of (tetraphenylporphyrinato) zinc(II) with anilines.

Complex formation of zinc-containing metalloporphyrins and nucleophilic substitution reactions involving pyridines

Linear correlations were found between the thermodynamic and kinetic parameters for the nucleophilic substitution and coordination of metalloporphyrins in various solvents with the participation of pyridines. Complex formation of zinc(II) tetraphenylporphyrin with n-donor ligands in chloroform at 25°C is proposed for use as a model system in the electronic spectroscopic investigation of the nucleophilicity and basicity of compounds capable of forming complexes of the n,ν type.

Complex Formation of Tetraphenylporphyrinatozinc(II) and Nucleophilic Substitution Reactions with Pyridines and Pyridine N -Oxides

Thermodynamic parameters of complexation of tetraphenylporphyrinatozinc(II) with pyridines in chloroform at 273–313 K are linearly related to the corresponding shifts of their absorption maxima in the electronic spectra, logarithms of the stability constants of the complexes, pKa values of the ligands in water, and Hammett substituent constants σ provided that steric factors are absent. Linear correlations also exist between thermodynamic and kinetic parameters of some nucleophilic substitution reactions and complex formation of tetraphenylporphyrinatozinc(II) with pyridines and pyridine N-oxides.

Nucleophilicity of Heteroaromatic N-Oxides in Coordination with Zn(II) Tetraphenylporphyrinate and in the Substitution Reactions

Linear correlations have been revealed between thermodynamic and kinetic parameters of the nucleophilic substitution and coordination reactions of zinc(II) tetraphenylporphyrinate with heteroaromatic Noxides in different solvents. Complex formation of zinc(II) tetraphenylporphyrinate with n-donor ligands in chloroform can serve as model system in spectroscopy studies of nucleophilicity and basicity of the compounds capable of the n,ν type complexes formation.

Complexes of pyridine and quinoline N-oxides with boron trifluoride: the 1H NMR study

The formation of complexes of pyridine and quinoline N-oxides with BF3 was studied by 1H NMR method. It was shown that the molecular complexes obtained are either individual isomers or a mixture of stereoisomers, whose structures are determined by both electronic and steric properties of substituents in a heterocycle. The type of hybridization (sp3 or sp2) of the O atom of the N-oxide group in the above adducts was assumed to be specified also by the above factors.

Donor-acceptor Complexes of Heteroaromatic N-Oxides with Copper and Zinc Chlorides

Thirteen new molecular complexes of pyridine and quinoline N-oxides with CuCl2 and ZnCl2 of composition 1:1 and 2:1 have been obtained and characterized. Their structure depends on the constitution of the ligand, the nature of the metal, and the reactant ratio at complex formation.

Thermooxidative Decomposition of Heterocyclic N-Oxides

Thermooxidative decomposition of pyridine N-oxide, 4-(4-dimethylaminostyryl)pyridine N-oxide, 4-(4-methoxystyryl)pyridine N-oxide, quinoline N-oxide, 2-methylquinoline N-oxide, 4-chloroquinoline N-oxide, 2-styrylquinoline N-oxide, and 2-(4-dimethylaminostyryl)quinoline N-oxide was studied. The kinetic parameters of the thermooxidative processes were calculated according to three independent procedures. The relation between the nature of heterocyclic N-oxide and its stability to thermal oxidation was analyzed.