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2-Mercapto-1,3,4-triazoles and 2-amino-1,3,4-thiadiazoles were synthesized by successive transformations of 5-arylisoxazole- and 4,5-dichloroisothiazole-3-carboxylic acids and their derivatives. The amino group of 5-(4,5-dichloroisothiazol-3-yl)-1,3,4-thiadiazol-2-amine was acylated with 5-phenylisoxazole-3-carboxylic acid chloride. Simple approaches to the preparation of previously unknown heterocyclic assemblies containing two or three azole rings with a high potential for biological activity are described.

The reaction of 4-substituted anilines with 3,4,4-trichloro-1,1-bis(3,5-dimethyl-1H-pyrazol-1-yl)-2-nitrobuta-1,3-dienes led to 1-arylamino-3,4,4-trichloro-1-(3,5-dimethyl-1H-pyrazol-1-yl)-2-nitrobuta-1,3-dienes, which under the action of 2-aminopyridines underwent heterocyclization to the corresponding 2-arylamino-substituted 4-(dichloromethylidene)-3-nitro-4H-pyrido[1,2-a]pyrimidines. The molecular structure of 4H-pyrido[1,2-a]pyrimidine containing the (4-ethoxyphenyl)amine substituent at position 2 was determined by X-ray structural analysis.

3-benzyl-6-isobutylpiperazin-2,5-dione [cyclo(leucylphenylalanyl)], 3-isobutylpiperazin-2,5-dione [cyclo(-leucylglycyl)] and 3-(sec-butyl-)-6-isobutyl-piperazine-2,5-dione [cyclo(leucylisoleucine)] have been obtained by cyclization of methyl esters of tert-butyloxycarbonyl derivatives of dipeptides, for the synthesis of which both carbodiimide-promoted peptide bond formation and the mixed anhydride method were used.

The reaction of 3,4,4-trichloro-1,1-bis(3,5-dimethyl-1H-pyrazol-1-yl)-2-nitrobuta-1,3-diene with 2-aminopyridine gave a polysubstituted pyrido[1,2-a]pyrimidine derivative with an aminopyridine residue in the 2-position, whereas heterocyclization of 3,4,4-trichloro-1,1-bis(1H-benzotriazol-1-yl)-2-nitrobuta-1,3-diene with substituted 2-aminopyridines afforded 2-(1H-berrzotriazol-1-yl)pyrido[1,2-a]pyrimidines. 2-(Morpholin-4-yl), 2-amino, and 2-(2-hydroxyethylamino) derivatives of polysubstituted pyrido[1,2-a]pyrimidines were synthesized, and those containing a 2-hydroxyethylamino group were converted to the corresponding 4,5-dichloro-1,2-thiazole-1-carboxylates. Specific features of heterocyclizations of benzotriazolyl and dimethylpyrazolyl derivatives of trichloronitro-1,3-butadiene to pyrimidine and pyrazole systems were revealed.

Tert-butyloxycarbonylprolylleucylglycinamide is obtained both by the interaction of tert-butyloxycarbonylprol ylleucylglycine ethyl ester with a methanolic ammonia solution and by the reaction of glycine amide with a mixed anhydride which was synthesized from tert-butyloxycarbonylprolylleucine and isobutylchloroformate. The removal of the tert-butyloxycarbonyl group by the action of formic acid or a dioxane solution of hydrogen chloride and treatment of the resulting salts with the corresponding base yielded a prolylleucylglycinamide, by the interaction of which with acetic, benzoic or 5-phenylisoxazole-3-carboxylic acids chlorides acyl derivatives of prolylleucylglycinamide are obtained.

Acylation of vanillin with isonicotinoyl chloride gave 4-formyl-2-methoxyphenyl pyridine-4-carboxylate which was converted into a number of functional derivatives, including those containing isoxazole and isothiazole heterocycles. In particular, the condensation of the title compound with primary amines afforded the corresponding Schiff bases. 4-Formyl-2-methoxyphenyl pyridine-4-carboxylate and one of the Schiff bases derived therefrom were reduced with sodium triacetoxohydridoborate to the corresponding alcohol and amine which were acylated with 5-arylisoxazole- and 4,5-dichloroisothiazole-3-carbonyl chlorides to obtain esters and amides having isoxazole and isothiazole fragments. The synthesized compounds readily formed complexes with palladium(II) chloride, which showed a high catalytic activity in the Suzuki reaction of 3-bromobenzoic acid with 4-methoxyphenylboronic acid in water in the absence of an organic solvent.

The results of surface snow monitoring in Vecherny Oasis, Thala Hills, East Antarctica, for evaluation of Belarusian Antarctic Station environmental impact are presented. Snow samples from the depth up to 15–20 cm were collected during 4–5th and 7–10th seasonal Belarusian Antarctic expeditions in the period from 2012 to 2018. Chemical-analytical study and determination of Ag, Al, As, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, K, Na, Mg, Mn, Mo, Ni, Pb, Sb, Se, Th, Tl, V, U, and Zn content were performed using ISP-MS method. Altogether 85 snow samples were analyzed. High spatial variability of trace elements content in the surface snow and differences between human impacted and non-impacted areas are shown. The elevated average content of trace elements in surface snow within the human impacted areas in comparison with ice sheet has been revealed. Based on the concentration of elements and EFc, the anthropogenic origin of Sb, Se, As, Cd, Zn, Cr, Cu, Mo, V, and Pb in the surface snow were suggested. Contribution of local sources of trace elements is considered to be more important for Vecherny Oasis than their regional or transboundary transfers. The development of guidelines for unified procedure of snow sampling for the goal of local impact monitoring in Antarctica would be useful for data comparison across Antarctic.

New substituted 3-((1H-1,2,3-triazol-1-yl)methyl)-5-arylisoxazoles (aryl = Ph, p-Tol) and 2-(5-phenylisoxazol-3-yl)-5-(2-(1-((5-(p-tolyl)isoxazol-3-yl)methyl)-1H-1,2,3-triazol-4-yl)ethyl)-1,3,4-oxadiazole were synthesized by means of click-chemistry procedures. The obtained compounds were used as ligands in preparation of palladium(II) complexes, and the latter proved to be high-turnover-number catalysts for C C cross-coupling reactions under Green Chemistry conditions. One of the ligands was structurally characterized by single crystal X-ray diffraction, and the structure of complexes was determined by 1H, 13C, 15N NMR spectroscopy and quantum-chemical modeling.

Alkylation of fluorophenols and phenolic aldehydes with 5-phenyl(p-tolyl)-3-chloromethylisoxazole under the Williamson reaction conditions afforded the corresponding ethers. Condensation of the resulting phenolic aldehyde derivatives and 5-phenyl(p-tolyl)isoxazole-3-carbaldehydes with p-fluoroaniline resulted in fluorine-containing azomethines. Acylation of fluorinated amines with 5-(p-tolyl)isoxazole- and 4,5- dichloroisothiazole-3-carbonyl chlorides gave rise to fluorinated amides bearing isoxazole and isothiazole fragments, representatives of which showed a synergistic effect in compositions with insecticides.

In the article the results of major and trace elements investigation in freshwater lakes of Vecherny Oasis (Enderby Land, East Antarctica) are considered. Water sampling was carried out during seasonal Belarusian Antarctic expeditions in 2011-2017. Totally 22 water samples from four lakes, three temporal ponds and one water course were collected for major and trace elements determination. The total concentrations of Ag, Al, As, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, K, Na, Mg, Mn, Mo, Ni, Pb, Sb, Se, Th, Tl, V, W, Zn in all samples as well as more than 40 additional trace elements in 3 samples from lakes were determined using ICP-MS method. It is shown that increase of heavy metals concentration (Cd, Pb, Zn, Sb, Co, Ni, Se, Mn) and As in the lakes compared to temporary ponds can be explained by anthropogenic impact including previous human activity in the oasis in late 1970th - early 1990th. The maximum concentrations of a number of technophilic elements (Pb, Mo, Mn, V, Sb, Zn) in Lake Nizhneye are possibly connected with the its lowest hypsometric location in catchment and the drainage of the territory impacted by past and present human activity.

From (4,5-dichloroisothiazol-3-yl)phenylmethanol by Ritter reaction a substituted acetamide was synthesized that at hydrolysis with HCl afforded (4,5-dichloroisothiazol-3-yl)phenylmethylamine hydrochloride. By reaction of (5-arylisoxazol-3-yl)- and 4,5-dichloroisothiazol-3-yl)arylmethanol with thionyl chloride the corresponding (1,2-azol-3-yl)arylchloromethanes were obtained. At treatment with O- and N-nucleophiles chlorine atom in chloromethylеne fragment of obtained compounds was substituted by residues of benzylamine, morpholine, vanillin, and ethoxy group.

Commercially available epicastasterone has been employed as a starting material for the preparation of [26-(2)H3 ]castasterone. The chemical synthesis has been realized in 13 chemical steps and 4.6% total yield. The target compound is intended to be used as internal standard for the quantitative analysis of brassinosteroids.

Reaction of 3-chloromethyl-5-phenyl(p-tolyl)isoxazoles with substituted phenols under the conditions of Williamson reaction afforded the corresponding 3-aryloxymethyl-5-phenyl(p-tolyl)isoxazoles. Treating the latter with sodium methylate, sodium phenyl(benzyl, furfuryl)thiolates and morpholine in methanol resulted in the replacement of the chlorine atom in 3-chloromethyl-5-phenyl(p-tolyl)isoxazoles by methoxy-, phenyl-(benzyl, furfuryl)sulfanyl groups and morpholine residue.

Accessible 5-phenyl(p-tolyl)isoxazol-3-carboxylic, 4,5-dichlorothiazol-3-carboxylic and 5-(benzylsulfanyl)-4-chlorothiazol-3-carboxylic acids were converted via a series of cascade transformations into the corresponding (1,2-azolyl)-3-carbonyl azides whose reaction with slightly basic aryl(heteryl)amines led to generation of 1-(1,2-azolyl)-3-aryl(heteryl)carbamides. To obtain isoxazolyl(isothiazolyl)carbamides containing the residues of highly basic amines, (1,2-azolyl)-3-carbonyl azides were preliminary transformed into aryl (1,2-azol-3-yl)carbamates by the action of phenol or 4-fluorophenol. Carbamates then were introduced into reaction with aliphatic or heterocyclic amines. Some of the obtained compounds and their precursors show high antitumor activity and are capable to increase the effect of cytostatic drugs applied in the medical practice.

A new method for introduction of one and two iodine atoms into the meta-carborane fragments containing carboxy groups at the core carbon atoms C1/C2 was developed. Reaction proceeded in acetic acid at heating in the presence of concentrated nitric and sulfuric acids.

Tetraiodo-1,2-dicarba-closo-dodecaborane and 9-bromo-8,10,12-triiodo-1,2-dicarba-closo-dodecaborane were synthesized by oxidative iodination of 1,2-dicarba-closo-dodecaborane and 9-bromo-1,2-dicarba-closo-dodecaborane, respectively, in AcOH using a mixture of nitric and sulfuric acid as an oxidant of iodine. The intermediates in the ortho-carborane iodination were identified. By the action of elemental bromine on 9-iodo-1,2-dicarba-closo-dodecaborane in the presence of aluminum chloride catalyst 9-iodo-8,10,12-tribromo-1,2-dicarba-closo-dodecaborane was obtained. Deborination of the synthesized substances with an alcohol solution of KOH led to formation of 1,5,6,10-tetraiodo-5-bromo-1,6,10-triiodo- and 5-iodo-1,6,10-tribromo-7,8-dicarbaundecaborates methylammonium salts.

The reaction of 3,4,4-trichloro-1-(2-thienyl)but-3-en-1-one with hydroxylamine gave 3-hydroxyiminomethyl-5-(2-thienyl)isoxazole which was converted into 5-(2-thienyl)isoxazole-3-carbonitrile by the action of acetic anhydride in pyridine. 5-(2-Thienyl)isoxazole-3-carbonitrile reacted with hydroxylamine to produce the corresponding amide oxime. Heterocyclization of its O-acyl derivatives in acetic acid afforded 5-substituted 3-[5-(2-thienyl)isoxazol-3-yl]-1,2,4-oxadiazoles.

Acylation of thiophene and phenol with 3,4,4-trichloro-3-butenoyl chloride afforded the corresponding 1-(thien-2-yl)- and 1-(4-hydroxyphenyl)-3,4,4-trichloro-3-buten-1-ones, whose reaction with amines led to the formation of 3-amino-1-(thien-2-yl, 4-hydroxyphenyl)-4,4-dichloro-2-buten-1-ones The heterocyclization of the initial ketones into pyrazole structure was not observed, and the reaction with hydrazine hydrate provided bispyrazole products, N,N′-bis(5-thien-2-yl)- and N,N′-bis[5-(4-hydroxyphenyl)-1H-pyrazol-3-ylmethylene]hydrazines.

5-(2,5-Dimethylphenyl)-1,2-oxazole-3-carbaldehyde oxime reacted with acetic anhydride in pyridine to give 5-(2,5-dimethylphenyl)-1,2-oxazole-3-carbonitrile which was converted into the corresponding amide oxime by treatment with hydroxylamine. O-Acyl derivatives of N′-hydroxy-5-(2,5-dimethylphenyl)-1,2-oxazole-3-carboximidamide underwent heterocyclization into 5-substituted 3-[5-(2,5-dimethylphenyl)-1,2-oxazol-3-yl]-1,2,4-oxadiazoles on heating in acetic acid.

Friedel-Crafts acylation of ferrocene and cymantrene with 3,4,4-trichlorobut-3-enoyl chloride gave the corresponding trichloroallyl ferrocenyl and cymantrenyl ketones. The reaction with ferrocene involved either one or both cyclopentadienyl fragments, depending on the reactant ratio. The acylation of acetylferrocene with 3,4,4-trichlorobut-3-enoyl chloride afforded 1-acetyl-1′-(3,4,4-trichlorobut-3-enoyl)ferrocene.

By treating with phosphorus pentoxide the 4,5-dichloroisothiazole-3-carboxamide 4,5-dichloro-3-cyanoisothiazole was synthesized whose reactions with piperidine, phenyl-and benzylthiols occurred with replacement of the chlorine atom in the position 5 by the residue of the corresponding nucleophile. Reactions with sodium thiobytylate and also with sodium methylate in methanol led to the formation both of the products of chlorine substitution by BuS or MeO groups respectively and of addition products of methanol to the cyano group. The reaction of butanethiol with cyanoisothiazole in 2-propanol in the presence of sodium 2-propylate was more selective and resulted in the replacement of the chlorine atom in the position 5 by the residue of the butanethiol.

Procedures were developed for preparing veratraldehyde, oximes of veratraldehyde and citral, and esters of these oximes, which are readily accessible fragrance compounds that can be synthesized from commercially available raw materials.

New regioisomeric indazolones containing fluorine atoms in the aromatic ring have been synthesized in high yield by the interaction of 2-acylcyclohexane-1,3-diones, and of their enol methyl ethers, obtained by methylating the initial β,β′-triketones with dimethyl sulfate in the presence of calcined potassium carbonate, with 4-fluorophenylhydrazine hydrochloride and with pentafluorophenylhydrazine. The structures of the synthesized compounds were confirmed by data of IR and 1H, 13C, and 19F NMR spectra.

Bromination of 3,4,4-trichlorobut-3-enoic acid in boiling carbon tetrachloride led to the formation of 2-bromo-3,4,4-trichlorobut-3-enoic acid as a result of replacement of hydrogen in the CH2 group. The reaction at 40°C involved the double C=C bond to give 3,4-dibromo-3,4,4-trichlorobutanoic acid. The brominated acids were converted into the corresponding chlorides which were used to acylate benzene, toluene, and bromobenzene according to Friedel-Crafts. The acylation was not selective, and only the reaction of 3,4-dibromo-3,4,4-trichlorobutanoyl chloride with benzene gave 3,4-dibromo-3,4,4-trichloro-1-phenylbutan-1-one as the only product. 1-Aryl-2-bromo-3,4,4-trichlorobut-3-en-1-ones were synthesized by bromination of the corresponding 1-aryl-3,4,4-trichlorobut-3-en-1-ones which were prepared previously by Friedel-Crafts acylation of substituted benzenes with 3,4,4-trichlorobut-3-enoyl chloride.

Reactions of 2-bromo-1-phenyl- and 2-bromo-1-(4-methylphenyl)-3,4,4-trichlorobut-3-en-1-ones with morpholine and diethylamine are accompanied by prototropic allylic rearrangement, leading to 3-amino-1-aryl-2-bromo-4,4-dichlorobut-2-en-1-ones as mixtures of E and Z isomers. The title compounds react with hydrazine, hydroxylamine, and thiourea to give the corresponding 5-aroyl-4-methoxypyrazoles, 3-aryl-5-hydroxyiminomethyl-4-methoxyisoxazoles, and 2-amino-4-aryl-5-trichlorovinylthiazoles.

Polychlorinated biphenyls (PCBs) in soils of Belarus were studied. The PCB concentrations in reference soils were determined. High accumulation levels of PCBs were found at the working and storage sites of PCB-containing electrical equipment. Soil contamination under PCB leakage from damaged capacitors and transformers was analyzed. Contamination of the Lakokraska plant site and adjacent areas (Grodno oblast) because of the long-term use of the Sovol was revealed. The structure of the PCB isomers in the soils was described depending on the contamination source.

The prevalence of hospital strains of P. aeruginosa, A. baumannii and K. pneumoniae characterizing by multiple drug resistance to overwhelming majority of antibiotics anew evoked an increased interest to colistin. However, until now there is not enough information concerning pharmacokinetics of colistin to optimize dosage of this pharmaceutical. The study was carried out to analyze pharmacokinetics of both colistin and sodium colistimitate in children with chemically induced neutropenia. To quantitatively detect colistin in blood serum the technique of highly effective fluid chromatography with mass spectrometry was applied. The concentration of colistin was detected in 21 children with chemically induced neutropenia (13 patients with septicemia, 8 children of control group) after intravenous injection of sodium colistimitate. The significant variability of pharmacokinetic parameters of colistin was established both in patients with septicemia and in control group. The technique of highly effective fluid chromatography with mass spectrometry can be applied for therapeutic medicinal monitoring and optimization regimen of dosage.

Treatment of 3,4-dihydroisoquinolines with triacetylmethane in refluxing alcohol for 2-3 h gave 3-acetyl-4-methylpyrido[2,1-a]isoquinolin-2-ones. Their basic physicochemical properties have been studied.

A new procedure has been developed for the synthesis of fused nitrogen-containing heterocycles having a bridgehead nitrogen atom via condensation of cyclic Schiff bases with β-keto esters.

Substituted amides and esters of 3,4,4-trichloro-3-butenoic acid were prepared by reactions of its chloride with appropriate amines and alcohols. Treatment of 3,4,4-trichloro-3-butenomorpholide and tert-butyl 3,4,4-trichloro-3-butenoate results in nucleophilic substitution of the internal chlorine atom with the morpholine residue, accompanied by prototropic allyl rearrangement.

Ionic hydrogenation of 8-aza-16-thiagona-1,3,5(10),13-tetraene-12,17-diones has been carried out by regioselective reduction of the carbonyl part of the aminovinylketothiolactone group to give 8-aza-16-thiagona-1,3,5(10),13-tetraen-17-ones.

Benzo[a]quinolizines (pyrido[2,1-a]isoquinolines) were synthesized via heterocyclization of 1-alkyldihydroisoquinoline Schiff bases with β-ketoesters.

From 3,4,4-trichloro-3-butenoic acid 3,3,4,4,4-pentachlorobutanoic, 3,4,4,4-tetrachloro-2-butenoic, and 2,3,4,4-tetrachloro-3-butenoic acids were synthesized. By Friedel &-Krafts reaction from 3,4,4-trichloro-3-butenoyl and 3,3,4,4,4-pentachlorobutanoyl chlorides with aromatic hydrocarbons the corresponding aryl chloroalkyl ketones were prepared. It was established that dehydrochlorination of 2,2,3,3,3-pentachloropropyl phenyl ketone with aqueous alkali under conditions of the phase-transfer catalysis at the molar ratio of reagents ketone:KOH:triethylbenzylammonium chloride equal to 1:4:0.05 involved the cleavage of two HCl molecules and resulted in 3,3,3-trichloro-1-propynyl phenyl ketone.

A new approach (AB + D → ABCD) to the construction of tetracyclic 8-azagonane (cyclopenta[5,6]pyrido[2,1-a]isoquinoline or benzo[a]cyclopenta[f]quinolizine) structures was developed and exemplified by cyclocondensation of 1-alkyl-3,4-dihydroisoquinolines with ethyl 2-oxocyclopentanecarboxylate.

Thienyl trichloroallyl ketone (I), a synthetic equivalent of β-chlorovinyl ketones, reacts with hydroxylamine to an intermediate dichloromethyl-substituted isoxazole which upon reaction with a second hydroxylamine molecule affords the hydoxyiminomethyl-substituted isoxazole (II).

5-(2,5-Dimethylphenyl)-1,2-oxazole-3-carbaldehyde oxime reacted with acetic anhydride in pyridine to give 5-(2,5-dimethylphenyl)-1,2-oxazole-3-carbonitrile which was converted into the corresponding amide oxime by treatment with hydroxylamine. O-Acyl derivatives of N′-hydroxy-5-(2,5-dimethylphenyl)-1,2-oxazole-3-carboximidamide underwent heterocyclization into 5-substituted 3-[5-(2,5-dimethylphenyl)-1,2-oxazol-3-yl]-1,2,4-oxadiazoles on heating in acetic acid.

By treating with phosphorus pentoxide the 4,5-dichloroisothiazole-3-carboxamide 4,5-dichloro-3-cyanoisothiazole was synthesized whose reactions with piperidine, phenyl-and benzylthiols occurred with replacement of the chlorine atom in the position 5 by the residue of the corresponding nucleophile. Reactions with sodium thiobytylate and also with sodium methylate in methanol led to the formation both of the products of chlorine substitution by BuS or MeO groups respectively and of addition products of methanol to the cyano group. The reaction of butanethiol with cyanoisothiazole in 2-propanol in the presence of sodium 2-propylate was more selective and resulted in the replacement of the chlorine atom in the position 5 by the residue of the butanethiol.

Reactions of 2-bromo-1-phenyl- and 2-bromo-1-(4-methylphenyl)-3,4,4-trichlorobut-3-en-1-ones with morpholine and diethylamine are accompanied by prototropic allylic rearrangement, leading to 3-amino-1-aryl-2-bromo-4,4-dichlorobut-2-en-1-ones as mixtures of E and Z isomers. The title compounds react with hydrazine, hydroxylamine, and thiourea to give the corresponding 5-aroyl-4-methoxypyrazoles, 3-aryl-5-hydroxyiminomethyl-4-methoxyisoxazoles, and 2-amino-4-aryl-5-trichlorovinylthiazoles.

Reaction of 1,1,4,4-tetrachloro-3-buten-2-one with 3,5-dimethylpyrazole gave 1,1-dichloro- 4,4-bis-(3,5-dimethyl-1-pyrazolyl)-3-buten-2-one. Treatment of the latter with amines resulted in replacement of one pyrazole ring by the amine residue with formation of the corresponding 4-amino-1,1-dichloro-4-(3,5- dimethyl-1-pyrazolyl)-3-buten-2-ones.