Vol 59, No 9 (2023)

The proposed communication demonstrates the efforts of researchers undertaken to prove the existence of fundamental analogies in the chemistry of structurally related compounds of carbon and silicon. Stable silicon analogues of ethylene - silenes or silaethylenes R₂C=SiR₂ - were obtained in 1979, disilynes R₂Si=SiR₂ - in 1981, and analogues of ethine or acetylene - disilins RSi≡SiR - only in 2004. Moving towards the intended goals, scientists synthesized a number of unique branched (bulky) organic and organosilicon substituents, attached them to silicon atoms, closed them from the action of oxygen and air moisture, and prevented secondary dimerization (oligomerization) reactions. The created steric protection led to the preparation of kinetically stable unsaturated silicon compounds and made it possible to characterize them by IR, NMR, UV-visible spectroscopy, and X-ray diffraction analysis.

New C³-substituted 5,6-dihydropyrrolo[2,1- a ]isoquinolines were obtained by a three-component domino reaction of 1-aroyl-3,4-dihydroisoquinolines, dimethylacetylenedicarboxylate, and CH-acids. The transformations proceed under microwave irradiation at 130°C in dry acetonitrile.

The reaction of acylation of some 2-amino-3-cyanocycloalkane[ b ]thiophenes with chlorides of various carboxylic acids gave the corresponding cycloalkane[ b ]-2-( N -acylamino)-3-cyanothiophenes, bubbling with hydrochloric gas from an alcoholic solution of amidonitriles to obtain cyclic 2-substituted thienopyrimidin-4-ones. The study of the antibacterial activity of the compounds against gram-positive and gram-negative microorganisms showed that most of them exhibit a weak antibacterial effect against staphylococci.

( Z )-6-alkylamino-2-Amino-4-(2-aryl-1-cyanovinyl)pyridine-3,5-dicarbonitriles were obtained by reaction of ( Z )-2-amino-4-(2-aryl-1-cyanovinyl)-6-chloropyridine-3,5-dicarbonitriles with various amines, including biologically active ones. The study of the spectral-luminescent properties showed the solid state fluorescence with a maxima at 472-562 nm and its absence in solutions. An increase in the volume fraction of water in solutions above a certain level caused the appearance of fluorescence due to the formation of aggregates. The enhancement of fluorescence upon addition of the viscous solvent glycerol confirmed the presence of aggregation-induced emission of the synthesized compounds.

According to quantum chemical calculations CAM-B3LYP/6-311++G(d,p) intramolecular migrations of arylazo groups in 5-arylazo-1,2,3,4,5-pentamethoxycarbonylcyclopentadienes occur by a dissociative mechanism through the intermediate formation of tight ionic pairs with low energy barriers: Δ E ^≠_ZPE, benzonitrile, 14.0 (Ar = C₆H₄NO₂-4) and 16.5 [Ar = C₆H₃(NO₂)₂-2,4] kcal/mol. In 5-arylazo-1,2,3,4,5-pentamethylcyclopentadienes, 1,5-sigmatropic shifts of arylazo groups occur along the perimeter of the five-membered ring in conformers with the exo position of the azo group relative to the cyclopentadiene ring with significantly higher activation barriers: Δ E ^≠_ZPE, benzonitrile, 30.3 (Ar = C₆H₄NO₂-4) and 27.5 [Ar = C₆H₃(NO₂)₂-2,4] kcal/mol. The calculations are in good agreement with the data for these compounds obtained by us earlier by dynamic NMR.

The rate constants of the Diels-Alder reaction of 2,5-dimethylfuran (1) with N -phenylmaleimide (2) in 5 solvents in the range of temperature 25-45°C and pressure 1-1000 bar have been determined. Activation enthalpy, entropy, Gibbs free energy and volume parameters have been calculated. The equilibrium constants of the 1 + 2 reaction in benzene in the temperature range 25-55°C have been determined, and the reaction enthalpy and entropy have been calculated.

For the first time, a new acyl ureide of the anticonvulsant and anti-alcohol drug galodif (3-chlorobenzhydryl urea) with succinic acid was obtained and studied. The synthesis was carried out by the acylation of galodif with succinic anhydride in presence of certain acids. Unlike galodif, which is practically insoluble in water, the resulting benzhydryl ureide is soluble in aqueous media and can potentially exhibit greater bioavailability and can be used as a liquid dosage form and prodrug with prolonged action.

In the presented work, the reaction of two 2-hydroxy-5-methylacetophenone chalcones and guanidine was investigated in the presence of hydrogen peroxide. Depending on the structure of the chalcones a 4.6-diaryl-2-aminopyrimidine or flavanol was obtained. The structures of the obtained products were elucidated by NMR spectroscopy and X-ray crystallography. Reaction route formation of compounds was proposed.