Ya. P. Nizhnik

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.

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.

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.

Reaction of 2,4-Dibromoquinoline with Hydrogen Chloride

It is known that nucleophilic aromatic substitution in nitrogen-containing heterocycles by the action of such weak nucleophiles as halide ions is very difficult to occur, even when the heteroring is activated by N-oxide moiety. For example, replacement of nitro group in heteroaromatic N-oxides requires severe conditions: heating with concentrated hydrohalic acids at the boiling boint or using acetyl or phosphinoyl halides [1]. According to the recent data, SN reactions of 4-nitroquinoline N-oxide in aprotic solvents are favored by formation of molecular complexes with p(tetracyanoethylene) [2] and especially v-acceptors (H, BF3, AlCl3) [3]. As a result, the corresponding products are formed in quantitative yield under mild conditions.

Molecular complexes of 4-nitropyridine and 4-nitroquinoline N-oxides with boron trifluoride and hydrogen chloride as intermediates in SNAr reactions

Complexation of 4-nitropyridine N-oxides with ν- (BF3, HCl) and π-acceptors (tetracyanoethylene, chloranil, 2,3-dichloro-5,6-dicyano-1,4-benzoquinone, 7,7,8,8-tetracyanoquinodimethane) activates the nitro group to nucleophilic replacement by chlorine. Adducts formed by 4-nitropyridine and 4-nitroquinoline N-oxides with boron trifluoride and hydrogen chloride were studied by IR spectroscopy. It was shown that these complexes belong to the n,ν type and that the donor-acceptor interaction therein involves the oxygen atom of the N-oxide group.

Reactions of 4-Nitroquinoline 1-Oxide with Aluminum Chloride

Abstract4-Nitroquinoline 1-oxide reacts with aluminum chloride to give 4-chloroquinoline 1-oxide. Aluminum chloride with 4-nitroquinoline 1-oxide forms a molecular complex in which it acts as electron acceptor and effective nucleophilic reagent (a source of chloride ions).