L. N. Divaeva

The novel azomethine ligands for binuclear copper(II) complexes with ferro- and antiferromagnetic properties

A series of novel binuclear ferro- and antiferromagnetic Cu(2+) chelates of structurally broadly varied Schiff bases (derived from o-tosylamino(hydroxyl)benzaldehydes and monoalkylated o-phenylenediamine, o-aminophenol, o-aminothiophenol, 1,2-diaminobenzimidazole, 1-aminobenzimidazoline-2-thione) and β-diketimines (derived from 2,6-di-i-Pr-aniline) has been prepared. The tautomerism of the ligands and structureof their copper complexes have been studied with the use of IR, 1H NMR EPR and EXAFS spectroscopy. Molecular and crystal structure of a β-diketimine copper dimer has been determined by X-ray crystallography. The magnetic measurements (2–300 K) performed for all the complexes showed that the ferro- and antiferromagnetic character of the exchange interaction depends both on the structure of the coordination site (origin of the ligating centers) and the structure of the ligands (in particular, on the type of the cycle annelated to the bridging fragment). Whereas S-binding metal chelates 13 (X = NTs, Y = S, R = H) are diamagnetic, the complexes 15 with annelated azole moieties are ferromagnetic.

1-amino-2-thiobenzimidazoleimines as novel ambidentate ligand systems

Azomethine derivatives of 1-amino-2-thiobenzimidazole (H2L) were synthesized and studied by IR and 1H NMR spectroscopy. Thiobenzimidazoline tautomeric form of these compounds was found to predominate in a solid state and DMSO solution. Novel mono-and binuclear metal chelates M(HL)2 and M2L2 (M = Ni(II), Cu(II), Co(II), Zn(II), Cd(II)) were synthesized on the basis of H2L derivatives and their composition and structures were established from IR, 1H NMR, EXAFS, and magnetochemical data. The composition of coordination sphere was shown to produce no effect on ferromagnetic exchange in binuclear Cu(II) complexes.

Molecular Design of New Magnetically Active Copper Complexes with Heteroaromatic Schiff Bases and Azo Compounds

Copper chelates with tridentate ligands containing pyridine or pyrazole ring at the azomethine or azo fragment were synthesized by chemical electrochemical methods, and their structure was characterized by the EXAFS spectra. Thermal magnetochemical analysis of the complexes revealed antiferromagnetic exchange interaction in all complexes. The exchange interaction parameter of the complex containing an N-tosylamino group in the ortho position with respect to the azomethine group is much lesser than that of the corresponding complex having an oxygen atom in the same position. The copper chelate derived from azopyrazole ligand shows low-temperature ferromagnetic phase transition.

Synthesis and structures of nickel(ii) complexes with thioether-containing β-aminovinyl ketones

New ligands, viz., thioether-containing β-aminovinyl ketones, and NiII complexes with these ligands were synthesized. The compounds were characterized by X-ray diffraction analysis, EXAFS, NMR, and IR spectroscopy, and magnetochemistry.

Synthesis and some conversions of N-substituted benzimidazole-2-sulfonic acids

A series of N-substituted benzimidazole-2-sulfonic acids was synthesized in good yield by the N-alkylation of benzimidazole-2-sulfonic acids by alkylation with simple and functionalized alkylating agents under mild conditions. The corresponding N-substituted benzimidazolones and also primary, secondary, and tertiary amines were obtained by the action on the obtained compounds of alkali, ammonia, ammonium acetate, and amines.

Prototropic equilibrium in 1(11)H-2, 3, 4, 5-tetrahydro[1, 3]diazepino[1, 2-a]benzimidazole, synthesis and pharmacological properties of its N-substituted derivatives

Based on the X-ray crystallography and 1H NMR spectroscopy data and quantum chemical studies, it was found that 1(11)H-2, 3, 4, 5-tetrahydro[1, 3]diazepino[1, 2-a]benzimidazole (1) exists almost exclusively in the 1H-prototropic form. To prepare the fixed 11H-diazepinobenzimidazole forms of 1, 1-R-2-(4-chlorobutylamino)benzimidazoles (R = Me, N=CHAr) were synthesized, which underwent thermal cyclization with the formation of a mixture of 11-Rsubstituted diazepine 1 and 1-R-2-(pyrrolidin-1-yl)benzimidazole. Alkylation of diazepine 1 in a neutral medium regioselectively gave 11-R-diazepinobenzimidazoles in high yield. Their 1-substituted isomers were obtained by carrying out this reaction in the system NaH—THF. The N(11)-derivatives of diazepinobenzimidazole 1 were found to inhibit dipeptidyl peptidase 4 (DPP-4), but less actively than a comparator drug sitagliptin. The compounds under study did not exhibit antiglycation action in vitro and virtually did not affect activity of α-glucosidase and glycogen phosphorylase. However, they are characterized by a strong antiaggregant effect, making these derivatives promising for further studies.

Synthesis of 9-bromocotarnine and its recyclization into 4-acyl-9-bromo-7,8-methylenedioxy-1,2-dihydro-3-benzazepines with anti-infective activity

Abstract9-Bromocotarnine in the stable perchlorate form has been obtained by the interaction of cotarnine with bromine. The reaction of 9-bromocotarnine with α-haloketones is accompanied by the extension of the six-membered hetero-ring to seven-membered ring and led to previously unknown 4-acyl-9-bromo-3-methyl-6-methoxy-7,8-methylendioxy-1,2-dihydro-3-benzazepines. Some of these compounds have been shown to have only moderate antibacterial (against Staphylococcus aureus, Escherichia coli) and fungistatic (Penicillium italicum) activities, but none of them has been shown to have a pronounced protistocidal activity against Colpoda steinii.

1-Amino-2-hydrazinobenzimidazole and its reactions with some carbonyl compounds

Abstract1-Amino-2-hydrazinobenzimidazole was obtained for the first time by treating 1-aminobenzimidazole-2-sulfonic acid with hydrazine hydrate. This compound readily condensed with aromatic aldehydes involving both amino groups. The condensation with 2,4-pentanedione affords 1-amino-2-(3,5-dimethylpyrazol-1-yl)benzimidazole, and with α-ketoacids in glacial acetic acid yields mixtures of 10-acetylamino-3-R-1,2,4-triazino[4,3-a]benzimidazol-4(10H)-ones and 4-amino-2-R-1,2,4-triazino[2,3-a]benzimidazol-3(4H)-ones.

Regioselectivity of N-substitution in bis-alkylation of 1,2,4-triazolo[1,5-a]benzimidazole-2-thione

Cyclization of the corresponding N-substituted 1,2-diaminobenzimidazoles with carbon disulfide in refluxing DMF leads to 3-methyl- and 3-benzyl-1,2,4-triazolo[1,5-a]benzimidazole-2-thiones. Based on the results of their S-alkylation, quantum chemical calculations by the density functional theory method, and 1D and 2D NMR spectroscopic studies, it was concluded that the bis-alkylation of N-unsubstituted 1,2,4-triazolo[1,5-a]benzimidazole-2-thione in the presence of a base proceeds with the formation of N(4)-derivatives of 2-alkylthio-1,2,4-triazolo[1,5-a]benzimidazole, rather than N(3)-derivatives as was believed earlier.

Recyclization of 9-bromocotarnine under the action of haloacylhetarenes. Synthesis and biological activity of the 4-heteroaroyl-9-bromo-1,2-dihydro-6-methoxy-7,8-methylenedioxy-3-benzazepines

Reaction of 9-bromocotarnine with heterocyclic α-halo ketones is accompanied by the expansion of the six-membered dihydropyridine ring to seven-membered dihydroazepine one and leads to previously unknown 4-heteroaroyl-9-bromo-3-methyl-1,2-dihydro-6-methoxy-7,8-methylenedioxy-3-benzazepines. It has been shown that some of the resulting compounds exhibit a significant antibacterial activity against Staphylococcus aureus and Escherichia coli. At the same time, the synthesized benzazepines have shown no significant protistocidal activity against Colpoda steinii and fungistatic activity against Penicillium italicum.