Vol 89, No 4 (2019)

The reaction of 1-alkenes with C₂D₅MgBr in the presence of TaCl₅ has been studied. Basing on the distribution of the deuterium label in the alkyl chain of the regioisomeric organomagnesium compounds, a tentative mechanism of their formation as key intermediates of 3-substituted tantalocyclopentanes has been proposed. The energy profiles of the reactions of carbomagnesation and β-reductive magnesaethylation of 1-alkenes have been obtained using the DFT method.

The synthesis of 2-hydroxybenzylidene-4-[(aza, thio)xantenyl]anilines has been carried out via the reaction of 2-hydroxybenzaldehyde, aniline, and (aza, thio)xanthydrol in acetic acid or ethanol medium. Two competing pathways leading the formation of 2-hydroxybenzylidene-4-[(aza, thio)xantenyl]anilines have been revealed by means of chromato-mass spectrometry. The growth-regulating activity of 2-hydroxybenzylidene-4-(5H-benzopyrano[2,3-b]-pyridin-5-yl)aniline towards spring wheat (Gornouralskaya variety) has been studied.

Continuing the search for biologically active compounds among functionally substituted azoles, new 1,2,4-triazole-3-thiols and 1,3,4-thiadiazoles derivatives bearing pharmacologically active carboxamide, hydroxyl or carboxyalkyl moieties, as well as N-acyclonucleoside, N-cyano- or carboxyethyl fragments were synthesized. Ability of some compounds obtained to inhibit the methylation of tumor DNA in vitro was revealed. The compound with the highest activity was selected for further in vivo studies.

A novel and efficient method for the synthesis of biologically active organic di-, tri- and tetrasulfides has been proposed. Different methods of redox activation of sulfur, hydrogen sulfide, and thiols in the reactions with organic compounds have been considered. Electrochemical initiation of the reactions of the mediator–H₂S–S₈ system with cyclohexane, methylcyclohexane, and benzene has occurred to the formation of polysulfides R₂S_n (n = 2–4). The application of tetrabutylammonium bromide as a mediator of H₂S oxidation has allowed to decrease the anodic overpotential of electrosynthesis. Di- and tetrasulfides have been obtained under anodic activation of the cycloalkanethiols (C₅, C₆) or thiophenol in the reaction with sulfur. Electroreduction of S₈ in the presence of the same thiols has favored the formation of di- and trisulfides. The yield and the ratio of the R₅S_n (n = 2–4) depend on the method of redox activation of the thiolating reagent.

Arylation of 2-acetylfuran with o-, m-, and p-nitrophenyldiazonium salts under the conditions of the Gomberg-Bachmann reaction has afforded the corresponding 5-(nitrophenyl)-2-acetylfurans. Their carbo-ethoxyhydrazones have undergone the cyclization into stable 4-(5-nitrophenylfur-2-yl)-1,2,3-thiadiazoles under the conditions of the Hurd-Mori reaction. Analogous semicarbazones have afforded the corresponding selenadiazoles upon oxidation with selenium dioxide. The analysis of electronic absorption spectra of the obtained hybrid heterocycles has shown that the conjugation of the phenyl and the furan ring in o-nitrophenyl derivatives is distorted due to steric hindrance, whereas the effect of direct polar conjugation leading to strong bathochromic shift of the absorption band has been observed in the case of the p-nitro derivatives. The position and intensity of the bands in the electronic absorption spectra of the studied compounds are determined by electronic as well as steric factors. The difference in the length of conjugation chain determined by the position of the nitro group in the phenyl fragment also contributes to the observed trend. The introduction of selenadiazole fragment instead of thiadiazole one has caused slight bathochromic shift of the band in the electron absorption spectra.

The DFT and MP2 theoretical conformational analysis of the recently synthesized (1,1′-phenyl-1,1′-silacyclohex-1-yl)disiloxane has revealed the energetic preference of the Ph_ax,Ph_ax conformer. The Ph_ax,Ph_ax: Ph_ax,Ph_eq: Ph_eq,Ph_eq conformers ratio has been estimated as of 46.6: 33.1: 20.3 from the M062X/6-311G(d,p) free energy simulation, suggesting the possibility of detecting individual conformers experimentally, e.g., by low-temperature ¹H and ¹³C NMR spectroscopy. However, only the presence of several conformers has been detected by means of ¹H NMR spectroscopy at 113 K; determination of the Δν (Hz) and ΔG^# (kcal/mol) parameters for the 6-membered ring interconversion has been impossible due to the signals broadening at low temperature, signal temperature shifts, and extremely low barrier of ring inversion at T_c < 113 K.

The reaction of tris(2-hydroxyethyl)amine with Fe(III) and Mn(II) carboxylates was studied for the first time. The complexes formation was confirmed by the IR spectroscopy and elemental analysis data. Crystal structure of manganese cinnamate(II) was established and its thermal stability was studied.

Nitro-substituted 2,3,7,7,8,12,18-hexamethyl-5-phenyl-13,17-diethylporphins with nitro groups in positions 10 and 20 of the porphyrin core and in the para-position of the benzene ring have been synthesized. The structure of the obtained compounds has been confirmed by H¹ NMR, UV, and IR spectroscopy as well as mass spectrometry. The kinetics of dissociation of zinc, copper, cobalt, and manganese complexes of the obtained porphyrins in proton-donor media has been studied. The stability of the porphyrin metal complexes has been related to the electronic effects of the substituents in the tetrapyrrole cycle and spatial distortion of the latter.

The UV spectral study of the interaction of titanium, zirconium, and hafnium metallocene dichlorides with styrene or methyl methacrylate in the media of different polarity (carbon tetrachloride and ethanol) has been carried out using the isomolar series method. The formation of weak intermediate complexes has been shown, the solvent polarity significantly affecting the process of their formation. It has been found for the first time that charge-transfer complexes between metallocene dichlorides and styrene are formed only in polar solvent (ethanol). Possible structures of intermediate complexes have been proposed.

The modifying effect of a titanium tetrachloride solution in hexane on carboxymethyl cellulose in the sodium salt and free acid forms was studied. The features of the structure, morphology, and thermal behavior of the modified carboxymethyl cellulose were revealed by IR spectroscopy, thermogravimetry, and X-ray diffraction analysis, as well as by scanning electron microscopy.

A series of novel 5-phenyl-substituted 1,3,4-thiadiazole-2-amines were designed, synthesized, and screened for their antitumor and antitubercular activities. The target compounds were synthesized starting from isocyanates and acid hydrazides by conventional and microwave-assisted protocols. The structures of the products were confirmed by ¹H NMR, ¹³C NMR, high-resolution mass spectrometry, and IR spectroscopy and elemental analysis. Some of the synthesized compounds showed significant invitro antitumor activities against breast cancer and normal human cell lines. Among them, N-benzyl-5-(4-fluorophenyl)-, N-benzyl-5-(4-nitrophenyl)-, and 5-phenyl-N-(p-tolyl)-1,3,4-thiadiazole-2-amines demonstrated higher inhibitory activities against the MDA-MB-231 cell line than the cisplatin control (IC₅₀ 3.3 ώM). N-Benzyl-5-(4-methoxyphenyl)-, 5-phenyl-N-[4-(trifluoromethyl)phenyl]methyl-, N-benzyl-5-(4-fluorophenyl)-, and N-benzyl-5-(4-nitrophenyl)-1,3,4-thiadiazole-2-amines exhibited high inhibitory activities against the HEK293T cell line (IC₅₀ 52.63, 42.67, 34.71, and 33.74 ώM, respectively), which were higher compared to the cisplatin control. In antitubercular activity testing against mycobacterium smegmatis MC155, 5-phenyl-N-[4-(trifluoromethyl)-phenyl]methyl-1,3,4-thiadiazole-2-amine proved to be a more potent agent (MIC 26.46 ώg/mL) compared to the Isoniazid control (12 ώg/mL). Potential bioactivities of the synthesized compounds were computed using Molinspiration and Molsoft software tools.

A novel series of 1,2,3-triazolyl isoxazole derivatives is synthesized from the corresponding propargylated isoxazoles and a number of aryl azides by the Click reaction. The highest yields of the reaction are achieved in the presence of copper sulphate pentahydrate and sodium ascorbate, and using DMF:water (2:1) as a medium. The compounds structures are elucidated from various spectral data. Antimicrobial activity tests of the title compounds demonstrate their moderate to good results compared to the standard.

In this paper, two new complexes of selenium caffeine, [Se(Caf)₄], and zinc α-tocopherol, [Zn(α-Tpl)₂(NO₃)₂], are synthesized. The structures of complexes are characterized by IR, Raman and ¹H NMR spectra, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), and thermogravimetric (TG/DTG) analysis. According to conductivity measurements the complexes are non-electrolytes. Spectroscopic studies of Se⁰ caffeine complex indicate its monodentate coordination via nitrogen atom N⁹ at 1: 4 molar ratio metal-to-ligand. In [Zn(α-Tpl)₂(NO₃)₂], α-Tpl chelate is coordinated as a monodentate ligand via oxygen atom of the hydroxyl group with 1: 2 metal-to-ligand molar ratio. The percentage scavenging activity of hydroxyl radical (IC₅₀ = 0.21 and 0.32 µg/mL), DPPH (0.17 and 0.30 µg/mL) and superoxide anion scavenging activity (0.18 and 0.32 µg/mL) indicate that selenocaffeine complex is of higher potential antioxidant activity than zinc(II) α-tocopherol complex.

Naked-eye colored chemo dosimeters based on symmetrical calix[4]azo dye conjugates A_1–3 are synthesized and characterized. Calix[4]azo dye conjugates exhibit high selectivity and sensitivity in detection of Fe²⁺, Ni²⁺, Co²⁺, and Cr³⁺ ions, and the highest sensitivity is determined for Cu²⁺. For the rapid monitoring of Cu²⁺ ions a simple paper test strip system is developed.

A series of 6-imino-1-aryl-4-(arylimino)-1,3,5-triazinane-2-thione derivatives are synthesized by cyclization of 1-aryl-3-cyanoguanidine with aryl isothiocyante in the presence of sodium methoxide under MW irradiation. Structures of the synthesized compounds 3a-j are elucidated from ¹H and ¹³C NMR, MS, and IR, data. The synthesized compounds are evaluated for their antimicrobial activity against B. subtilis, S. aureus, P. aeruginosa, and E. Coli. Some compounds demonstrate promising activity against the tested strains.

A novel series of 2-(4-chlorobenzylamino)-4-(cyclohexylmethylamino)-pyrimidine-5-carboxamide derivatives are synthesized and their structures are confirmed by ¹H and ¹³C NMR, and MS spectral data. The compounds are screened for their antitubercular activity, and those with aryl moiety 7o, 7q, and 7r demonstrate potent activity against Mycobacterium tuberculosis. Docking studies suggest a mode of interaction of the products with the binding site of enoyl-CoA hydratase demonstrating that the target compounds were potential anti-TB agents.

A method was developed for the synthesis of new fused amines, thieno[3,2-d]pyrimidine derivatives, starting from the corresponding chloride and various amines. Isomeric triazolo[4,3-c]- and -[1,5-c]-pyrimidines were obtained. The absence of azidotetrazole transformation of fused tetrazolo[1,5-c]pyrimidine was revealed.

Batch-type spectroscopic and continuous potentiometric titration of K₄Mo₂Cl₈ with potassium dichromate in 1 M hydrochloric acid was carried out. Intermediate forms of molybdenum compounds in the oxidation process were determined. It was shown that the oxidation is accompanied by a rearrangement of the complex structure with the formation of trinuclear oxo- and hydroxohalide anions of molybdenum into trinuclear oxo- and hydroxohalide molybdenum anions. The standard reduction potential of the pair \(\rm{E}^o_{298}(Mo^{VI}/Mo^{IV}_3=1.003+0.032\;V\) was determined.