Vol. 22 No. 4 (2024): Issue in Progress

A new synthetic procedure for preparing tetrabutylammonium closo-dodecaborate (Bu₄N)₂B₁₂H₁₂ by the solvent-free pyrolysis of tetrabutylammonium tetrahydroborate Bu₄NBH₄ has been developed. The procedure also provides isolation of pure tetrabutylammonium octahydrotriborate Bu₄NB₃H₈ as a by-product. The main advantages of the route proposed are convenience and utilization of readily available starting materials. The compounds prepared have been characterized by NMR and IR spectroscopy. Based on the DFT calculations of normal modes of the [B₃H₈]^- and [B₁₂H₁₂]^2- anions, the assignment of the main absorption bands in the IR spectra of the compounds synthesized has been performed.

A simple and efficient method for synthesizing aromatic compounds with a difluoro(methoxy)methyl fragment (CF₂OCH₃) by the fluorodesulfurization of thionoesters has been developed. Systematic screening identified SnCl₄/DAST as the optimal reagent combination, providing excellent selectivity and high yields of target products. A series of aromatic difluoro(methoxy)methyl compounds was synthesized under these conditions. Further studies of the electronic properties of the difluoro(methoxy)methyl group using ¹⁹F NMR allowed us to determine its Hammett constants for inductive (σ_I) and resonance (σ_R) effects. The results show that CF₂OCH₃ acts as a moderately electron-withdrawing substituent, underscoring its potential as a versatile group for designing organic molecules with precisely tuned electronic characteristics.

A series of 6-aryl[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole derivatives has been synthesized. Their anti-inflammatory activity has been studied in vivo in a carrageenan model of the paw inflammatory edema in rats. 3-(2-Fluorophenyl)-6-phenyl-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole (3c) and 3-(2-fluorophenyl)-6-(4-methoxy-phenyl)[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole (3d) have been identified as hit compounds with the anti-exudative activity. The crucial role of the fluorine atom in the anti-inflammatory activity has been determined, which value considerably correlates with the calculated values of lipophilicity and solubility.

It has been shown that the oxidation of ketones – analogs of cyclohexanone – by hydrogen peroxide in the presence of Cu₃(btc)₂ (btc^3- = 1,3,5-benzenetricarboxylate) occurred mainly by the radical mechanism, rather than by the Baeyer-Villiger reaction mechanism, and led to a mixture of products formed due to the ring cleavage and reduction of the hydrocarbon chain length. Unlike aliphatic ketones, α-tetralone hardly underwent conversion in the reaction with H₂O₂ in the presence of HKUST-1, and the oxidation of the same ketone in the presence of Fe₂(OH)₃(btc) led to the formation of a number of products; among them, 1,4-naphthoquinone was dominant.

The study considers the possibility of using 3,3',5,5'-tetramethylbenzidine (TMB) as an indicator in the enzymatic analysis for the quantitative determination of quaternary ammonium compounds on the example of ethonium. The feasibility of using TMB as an indicator in the kinetic photometric method has been confirmed. Kinetic curves showing the relationship between the optical density and the ethonium concentration have been constructed. The reaction rates of acetylcholinesterase inhibition by ethonium have been estimated using the tangents of the angles of these curves with TMB as an indicator. The degree of enzyme inhibition has been calculated, and a linear relationship between the ethonium concentration and the degree of inhibition has been determined. This method was applied to determine the ethonium content in 0.1% ethonium gel. The relative standard deviation of the method does not exceed 2.5 %. The approach suggested offers a reliable and accurate method for the quantitative analysis of ethonium in dosage forms.