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A number of novel di- and triorganotin(IV) complexes 1–5 (Ph2SnL1, Ph2SnL2, Et2SnL2, Ph3SnL3, Ph3SnL4) with mono- or dianionic forms of thio-Schiff bases containing antioxidant sterically hindered phenol or catechol fragments were synthesized. Compounds 1–5 were characterized by 1H, 13C NMR, IR spectroscopy, and elemental analysis. The molecular structures of complexes 1 and 2 in the crystal state were established by single-crystal X-ray analysis. The antioxidant activity of new complexes as radical scavengers was estimated in DPPH and ABTS assays. It was found that compounds 4 and 5 with free phenol or catechol fragments are more active in these tests than complexes 1–3 with tridentate O,N,S-coordinated ligands. The effect of compounds 1–5 on the promoted oxidative damage of the DNA by 2,2’-azobis(2-amidinopropane) dihydrochloride and in the process of rat liver (Wistar) homogenate lipid peroxidation in vitro was determined. Complexes 4 and 5 were characterized by more pronounced antioxidant activity in the reaction of lipid peroxidation in vitro than compounds 1–3. The antiproliferative activity of compounds 1–5 was investigated against MCF-7, HTC-116, and A-549 cell lines by an MTT test. The values of IC50 are significantly affected by the presence of free antioxidant fragments and the coordination site for binding.

Oxidative coupling of two different thiols bearing aliphatic, alicyclic, aromatic, and hetero-aromatic moieties promoted by mild oxidizing agents, viz., sterically hindered o-benzo(imino)-quinones, carried out in N-methylpyrrolidone at room temperature led to unsymmetrical disulfides. Among the studied oxidizers, the most active was 3,6-di-tert-butyl-o-benzoquinone, which, in contrast to 3,5-di-tert-butyl-o-benzoquinone, was not involved in the Michael addition. Under the optimal reaction conditions, the yields of the target unsymmetrical disulfides reach 81%.

The redox reactions of organic trisulfides containing various hydrocarbon groups with alkenes in aprotic solvents were studied. The electrooxidation of trisulfides proceeds irreversibly by the ECE mechanism, with formation of sulfur-centered RS+ and RSS+ intermediates. The generated cations enter into electrophilic addition reactions with alkenes, forming asymmetric di- and monosulfides. The electrochemical reduction of trisulfides leads to the formation of a radical anion, which is fragmented into the RSS anion and RS radical. In the presence of acetic acid, the cathodic activation of trisulfides is accompanied by the formation of alkyl and phenyl hydrodisulfides (RSSH).

Two approaches to synthesis of unsymmetrical disulfides based on different types of thiol activation, namely, an electrochemical method in the presence of a redox mediator and a microwave irradiation, were discussed. The mediated electrosynthesis procedures were carried out by the oxidative coupling of thiols or by the thiol-disulfide exchange in the presence of redox pairs—substituted o-aminophenol/o-iminobenzoquinone. It has been established that the formation of unsymmetrical disulfides under electrochemical conditions occurs as a result of both the oxidative coupling of sulfur-centered radicals, and a redox-mediator promoted thiol-disulfide exchange, which led to a high yield of heterodimeric products (89%–99%). The microwave-assisted synthesis made it possible to obtain the target products with yields of 13%–86% depending on different irradiation parameters such as power, temperature, and irradiation duration. However, this method requires a rigorous selection of conditions for each reaction and is therefore inferior to the electrochemical approach.

The extraction of various sulfur-containing compounds occurring in the oil and condensate fractions using solutions based on N-methylpyrrolidone was studied. The extracts can later be used in the organic/electrochemical synthesis of valuable organosulfur compounds. By the example of a model mixture, the solvent is shown to be selective to various classes of organic sulfur compounds: thiols, mono-, di-, and trisulfides. It is established that the solvent exhibits the greatest affinity to aromatic sulfur compounds. The extraction degree increases from mono- to di- and trisulfide. In the case of aliphatic thiols, a decrease in the degree of extraction is observed with an increase in the length of the hydrocarbon group. The optimal parameters of extraction with mixtures based on N-methylpyrrolidone for light gasoline fractions BPT-90 °C and BPT-120 °C were set: the temperature – 35 °C, the ratio solvent - feedstock is 1 to 1. In the series of different mixtures of solvents, a selective solvent based on dimethyl carbonate (5% by weight) showed the highest efficiency. At the same time, the highest raffinate yield with a moderate total sulfur content is observed for the solvent with H2O (5% by weight). A multi-stage extraction of sulfur components from gasoline fractions using the mixture N-methylpyrrolidone with H2O allowed reducing the content of organic sulfur compounds by 7-10 times. A combined process based on the extraction of thiols from model mixtures and its oxidation by o-benzoquinones is proposed. Unlike the more aggressive oxidizing agents o-benzoquinones depending on the structure ensure the utilization of thiols to thioethers or disulfides.

Hydrogen sulfide and alkanethiols are toxic compounds containing in the production of wells in many oil and gas condensate fields. Because the policy of hydrocarbon processing enterprises aimed at the development of new fundamental research, processes and technologies in order to find rational use of raw materials, the conversion of hydrogen sulfide and alkanethiols into valuable compounds is one of the strategic goals of the oil and gas industry. The methods of "green" chemistry are perspective processes for converting hydrogen sulfide and alkantiols into valuable organic compounds, which allow working in environmentally friendly conditions with minimal energy and resource costs. The reactions of direct nucleophilic substitution of butanol-2, pentanol-1 and hexanol-1 to HS- and RS- group by single-electron reduction of hydrogen sulfide and alkanthiol in acetonitrile and ionic liquid at room temperature and atmospheric pressure with a single by-product - H2O were described. The possibility of conducting an experiment without electrolyte due to the intrinsic electrical conductivity of the ionic liquid allows not only lowering the consumption of reagents, but also facilitating the isolation of the target product. Due to the structuring and the matrix effect in ionic liquids, the duration of electrolysis in the reactions under consideration is 2-3 times less than in the case of aprotic solvents.

Most methods of obtaining aromatic thiols are based on nucleophilic substitution reactions at halogen derivatives of aromatic hydrocarbons when used as nucleophilic reagents sodium thiolate, thiourea or potassium xanthate at high temperatures, pressure and in the presence of catalysts. The direct reaction of nucleophilic substitution of OH-groups in the phenols, pyrocatechol and benzyl alcohol to the HS-group in conditions of one-electron reducrion of hydrogen sulfide in acetonitrile and pyridinium ionic liquid was investigated for the first time. The proposed reactions proceed at room temperature and atmospheric pressure. The use of "green" solvent - ionic liquid - reduces the syntheses time in а half, improves ecological safety friendliness of the process and reduces the consumption of reagents. The main positive feature of these studies is not only ecological safety of reactions of nucleophilic substitution (due to the lack of harmful byproducts), but the use of electrochemical reactions in ionic liquid media, that is very relevant in modern science in terms of new environmental technologies development. For citation: Okhlobystina A.V., Okhlobystin A.O., Berberova N.T., Burmistrova D.A. Hydrogen sulfide in nucleophilic substitution reactions of hydroxy groups in aromatic alcohols. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 9-10. P. 36-41 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

A number of substituted o-aminophenols has been investigated as redox mediators of the thiol oxidation to disulfides. The electrooxidation of o-aminophenols leads to the corresponding o-iminobenzoquinones. These compounds react with thiols in the solution with a formation of disulfides. It was established that the use of 4,6-di-tert-butyl-2-(tert-butylamino)phenol as a redox mediator can reduce the overpotential of the thiol oxidation by 0.2–1.4 V depending on the nature of the coupling thiols. The unsymmetrical disulfides with alkyl, aryl, and heteroaryl substituents were obtained as the result of the indirect electrosynthesis.

Developing pathogen-specific recombinant antibody fragments (especially nanobodies) is a very promising strategy for the treatment of infectious disease. Nanobodies have great potential for gene therapy application due to their single-gene nature. Historically, Mycoplasma hominis has not been considered pathogenic bacteria due to the lack of acute infection and partially due to multiple studies demonstrating high frequency of isolation of M. hominis samples from asymptomatic patients. However, recent studies on the role of latent M. hominis infection in oncologic transformation, especially prostate cancer, and reports that M. hominis infects Trichomonas and confers antibiotic resistance to Trichomonas, have generated new interest in this field. In the present study we have generated specific nanobody against M. hominis (aMh), for which the identified target is the ABC-transporter substrate-binding protein. aMh exhibits specific antibacterial action against M. hominis. In an attempt to improve the therapeutic properties, we have developed the adenoviral vector-based gene therapy approach for passive immunization with nanobodies against M. hominis. For better penetration into the mucous layer of the genital tract, we fused aMh with the Fc-fragment of IgG. Application of this comprehensive approach with a single systemic administration of recombinant adenovirus expressing aMh-Fc demonstrated both prophylactic and therapeutic effects in a mouse model of genital M. hominis infection.