Žurnal organičeskoj himii

We investigated the dynamic structure of benzalaniline derivatives, in which an important factor is the inhibited internal rotation of benzene rings. The parameters of conformational processes of this type are characterized based on NMR spectroscopy data and quantum mechanical calculations. In these compounds, nitrogen atoms play a key role. It has been shown that important information is provided by NMR parameters with the direct participation of nitrogen, which become available in experiments with ¹⁵N-enriched compounds. Important new information about the conformation of molecules of this class can be provided by the spin-spin interaction constants involving ¹⁵N nuclei. A series of [¹⁵N]enriched benzalaniline derivatives with substituents in the ortho position of the benzene ring distant from the nitrogen was studied. It has been shown that substituents can act as both a stabilizing (R = F, OH, OCH₃) and a destabilizing factor (R = CH₃). The influence of medium acidity on these conformational equilibria was studied. This type of structural motif can be used to design pH-induced molecular switches. According to our estimates, the molecular switching energy of [¹⁵N]-2-fluorobenzalaniline is ~7 kcal/mol, which is one of the highest values for molecular switches of this type.

By reacting the previously synthesized 4-(1,4-benzodioxan-6-yl)tetrahydro-2H-pyran-4-carboxylic acid chloride with hydrazine hydrate a symmetrically substituted diacylhydrazine was synthesized, cyclized with phosphorus oxychloride to 2,5-bis-(4-(1,4-benzodioxan-6-yl)tetrahydro-2H-pyran-4-yl)-1,3,4-oxadiazole. For the synthesis of unsymmetrically 2,5-disubstituted 1,3,4-oxadiazoles, the condensation reaction of the above mantione acid chloride with various hydrazides was carried out, and the subsequent cyclization of the resulting diacyl-substituted hydrazines under action of phosphorus oxychloride. The antiarrhythmic properties of the synthesized compounds were studied.

The products of diazotization of 2-, 3-, and 4-aminopyridin-1-oxides in the presence of TsOH, TfOH, and camphorsulfonic acid were investigated by IR, NMR, X-ray diffraction analysis, ESI/MS and MS2 spectroscopy, and B3LYP/aug-cc-pVDZ. The structures of the products and their stability during storage depend on the type of the starting aminopyridine. 4-Aminopyridin-1-oxide reacts to give stable diazonium sulfonates, and the 2-aminoisomer gives [1,2,3,5]oxotriazol[5,4-a]pyridinium-2 sulfonates. All products readily undergo reactions typical for diazonium salts. By the B3LYP/aug-cc-pVDZ method it was determined that 4-diazonium-pyridinium-1-oxide and benzoldiazonium cation have the highest stability in the series of diazonium cations of pyridine, pyridine-1-oxide and benzoldiazonium cation.

For the first time, amides of (5Z,9Z)-eicosa-5,9-dienoic acid, which exhibits a high inhibitory activity of topoisomerases I and II, were synthesized using aliphatic and O-containing 1,2-dienes at the key stage of the intermolecular cross-cyclomagnesiation reaction, catalyzed by Cp₂TiCl₂.