Vol 61, No 12 (2025)

Based on the analysis of isospectral molecular graphs, possible spatial structures of the transition states of thermal isomerization reactions of C₄H₃FX (X = NH, O, S) molecules in an inert atmosphere were determined. The formation of transition states of aromatic systems is provided by the stabilization effect of fragmented parts of the initial conjugated π-electron system. The structural and energetic characteristics of the ground and transition states of C₄H₃FX (X = NH, O, S) molecules were calculated using the DFT/B3LYP/6-31G(d) method. The proposed pathways of thermal isomerization of 2-fluoropyrrole, 2-fluorofuran, and 2-fluorothiophene molecules were constructed, and the mechanisms of [2,3]-substituent rearrangements in the considered heterocycles were determined. The studies showed that thermal [2,3] rearrangement reactions of 2-fluoropyrrole, 2-fluorothiophene, and 2-fluorofuran proceed via the formation of non-aromatic isomers belonging to the Dewar benzene structural type.

The reactions of 1,1'-biadamantanes in a nitric acid medium, in the presence of N-nucleophiles, have led to the synthesis of a number of symmetric bifunctional derivatives. The syntheses with C-nucleophiles have been carried out using 1,1'-biadamantane-3,3'-diols in a sulfuric acid medium. A variety of new tetra- and hexa-substituted functional derivatives of 1,1'-biadamantane have been synthesized using the H₂SO₄ – HNO₃ system.

By reaction of 1-R-3,3-dimethyl-1,2,3,4-terahydroisoquinolines (R=H, Me) with hexamethylenediisocyanate (HDI) the corresponding N,N′-(hexane-1,6-diyl)bis(1-R-3,3-dimethyl-3,4-dihydroisoquinolin-2(1H)-carboxamides have been synthesized. The reaction of HDI with 1,3,3-trimethyl-3,4-dihydroisoquinoline leads to (2Z,2Z′)-N,N′-(hexane-1,6-diyl)bis[2-(3,3-dimethyl-3,4-dihydroisoquinolin-1(2H)-ylidene) acetamide, the similar product have been obtained for the corresponding benzo[f]isoquinoline. The both amides bis-derivatives were obtained earlier by direct counter synthesis by Ritter cyclisation. When HDI reacted with enaminoamides of the 6,7-diethoxy-1-methylidene-3,3-dimethyl-1,2,3,4-tetrahydroisoquinoline series, carbamylation occurred at the β-carbon atom of the enamine fragment, resulting in the formation of corresponding bis-derivatives of malonic acid diamide.

Functional substituted 1-benzofurans were obtained by three-component condensation of diatomic phenols, phenylglyoxal hydrate, and methylene-active compounds. When pyrocatechol is used, the respective adduct is formed, which does not undergo further cyclization.

The interaction of furyl-substituted anilines with various arylulfonyl chlorides was studied. The reaction proceeds selectively in the case of 2-(2-furyl)anilines. The Hinsberg reaction products formed in the first step undergo repeated spontaneous sulfarylation in the presence of electron-withdrawing groups in the sulfaryl moiety, as clearly confirmed by X-ray diffraction analysis.

A convenient and accessible method was used to synthesize novel heterocyclic hybrid systems: 3-(2-(1H-benzo[d]imidazol-2-yl)ethyl)-4-methylquinolin-2(1H)-ones, 3-(2-(benzo[d]oxazol-2-yl)ethyl)-4-methylquinolin-2(1H)-ones, and 3-(2-(benzo[d]thiazol-2-yl)ethyl)-4-methylquinolin-2(1H)-ones. The synthesis was carried out by reacting ethyl 3-(4-methyl-2-oxo-1,2-dihydroquinolin-3-yl)propanoates, substituted in the benzene ring, with α-phenylenediamine, α-aminophenol, and α-aminobenzenedithiol.