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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.

Acylation of benzene and toluene with 5-phenyl- and 5-(p-tolyl)isoxazole-3-carbonyl chlorides gave 5-phenyl(or p-tolyl)isoxazol-3-yl phenyl(or p-tolyl)ketones which were reduced to the corresponding alcohols with sodium tetrahydridoborate in propan-2-ol. Selective reduction of the carboxy group in 4,5-dichloroisothiazole-3-carboxylic acid was achieved by the action of BH3, and the aldehyde group in 4-formyl-2-methoxyphenyl 5-arylisoxazole-3-carboxylates and 4,5-dichloroisothiazole-3-carboxylates was reduced to hydroxymethyl group with sodium triacetoxyhydridoborate in benzene. Acylation of the resulting hydroxymethyl derivatives with 5-arylisoxazole- and 4,5-dichloroisothiazole-3-carbonyl chlorides afforded the corresponding esters containing two azole fragments in their molecules.

Reactions of 4,5-dichloroisothiazol-3-ylcarbonitrile with methylmagnesium iodide and ethylmagnesium bromide afforded the corresponding alkyl (4,5-dichloroisothiazol-3-yl) ketones. The reaction of (4,5-dichloroisothiazol-3-yl) methyl ketone with morpholine and piperidine provided 5-morpholino-(piperidino)-substituted derivatives, by the action of sodium borohydride in 2-propanol the keto group was reduced to alcoholic hydroxy group. The bromination of (4,5-dichloroisothiazol-3-yl) methyl ketone with elemental bromine gave bromomethyl (4,5-dichloroisothiazol-3-yl) ketone, whose reaction with thiourea resulted in 2-amino-4-(4,5-dichloroisothiazol-3-yl)thiazole.

It has been shown that the NO3− and Cl− ions in methylpyperidine, cetylmorpholine, quinuclidine, and triethyl quaternary ammonium salts (QAS) are characterized by approximately equal exchange constants KCl−NO3− despite a significant difference in the structure of QAS. For methylpyperidine, cetylmorpholine, and triethyl salts, KCl−NO3− are almost equal, which can be attributed to the special features of ethyl radicals fixed into the cycles, which occupy a smaller volume and thus reduce the effect of the length of the third substituent, so that the parameters of the closest approach become nearer.

Fluoride-mediated nucleophilic substitution reactions of tert-butyl 4,5-dichloroisothiazole-3-carboxylate with various amines occur under mild conditions yielding 5-(alkylamino)isothiazoles in moderate to high yields.

4,5-Dichloro-1,2-thiazol-3-amine was synthesized starting from accessible 4,5-dichloro-1,2-thiazole-3-carbonyl azide and -3-carboxamide via Curtius and Hofmann rearrangements, respectively. The procedure involving Curtius rearrangement was found to be more advantageous from the preparative viewpoint.

It was found that the size of quaternary ammonium salt cations strongly influenced the log\( K_{Cl^ - }^{NO_3^ - } \) value, which was explained by the special features of ionic association in the organic phase. The use of 3,4,5-tridodecyloxybenzyltridodecylammonium nitrate as an electrode active substance could increase the selectivity of the NO3−-selective electrode with respect to Cl− ions.

4,5-Dichloro-3-trichloromethylisothiazole reacted with piperidine, morpholine, pyrrolidine, and piperazine in DMF to give 81–96% of the corresponding 5-amino-4-chloro-3-trichloromethylisothiazoles as a result of selective nucleophilic replacement of the 5-chlorine atom. Acylation of 4-chloro-5-(piperazin-1-yl)-3-trichloromethylisothiazole with acetyl chloride gave 4-chloro-5-(4-acetylpiperazin-1-yl)-3-trichloromethyl-isothiazole.

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.

By acylation of benzene, toluene, and p-xylene with 4,5-dichloroisothiazole-3-carbonyl chloride the corresponding aryl 4,5-dichloroisothiazol-3-yl ketones were obtained. By reaction of 4,5-dichloroisothiasol-3-yl 4-methylphenyl ketone with piperidine, alkyl(aryl) thiolates, sodium alcoholates, and 2,4-dinitrophenylhydrazine were synthesized 4-methylphenyl 5-piperidyl-4-chloroisothiazol-3-yl ketone, 5-alkyl(aryl)sulfanyl-4-chloroisothiazol-3-yl 4-methylphenyl ketones, 5-alkoxy-4-chloroisothiazol-3-yl 4-methylphenyl ketones, and 2,4-dinitrophenylhydrazone of the initial ketone respectively.

Oximes of β-isatin, isoxazole- and ferrocene-containing ketones, o- and m-carborane alcohols react with isoxazol- and isothiazolecarboxylic acid chlorides in the presence of triethylamine to afford the corresponding esters.

Condensation of substituted benzaldehydes of the vanillin series with propane-1,2-diol and 3-chloropropane-1,2-diol in boiling benzene in the presence of FIBAN K-1 sulfonated cation exchanger as catalyst gave the corresponding substituted 1,3-dioxolanes.

Acylation of benzene and toluene with 5-phenyl- and 5-(p-tolyl)isoxazole-3-carbonyl chlorides gave 5-phenyl(or p-tolyl)isoxazol-3-yl phenyl(or p-tolyl)ketones which were reduced to the corresponding alcohols with sodium tetrahydridoborate in propan-2-ol. Selective reduction of the carboxy group in 4,5-dichloroisothiazole-3-carboxylic acid was achieved by the action of BH3, and the aldehyde group in 4-formyl-2-methoxyphenyl 5-arylisoxazole-3-carboxylates and 4,5-dichloroisothiazole-3-carboxylates was reduced to hydroxymethyl group with sodium triacetoxyhydridoborate in benzene. Acylation of the resulting hydroxymethyl derivatives with 5-arylisoxazole- and 4,5-dichloroisothiazole-3-carbonyl chlorides afforded the corresponding esters containing two azole fragments in their molecules.

Reactions of 4,5-dichloroisothiazol-3-ylcarbonitrile with methylmagnesium iodide and ethylmagnesium bromide afforded the corresponding alkyl (4,5-dichloroisothiazol-3-yl) ketones. The reaction of (4,5-dichloroisothiazol-3-yl) methyl ketone with morpholine and piperidine provided 5-morpholino-(piperidino)-substituted derivatives, by the action of sodium borohydride in 2-propanol the keto group was reduced to alcoholic hydroxy group. The bromination of (4,5-dichloroisothiazol-3-yl) methyl ketone with elemental bromine gave bromomethyl (4,5-dichloroisothiazol-3-yl) ketone, whose reaction with thiourea resulted in 2-amino-4-(4,5-dichloroisothiazol-3-yl)thiazole.

Neuroepithelial tumor cells were cultured in vitro. The biopsy material was taken from 93 children at removal of the brain tumors during neurosurgical operations. The individual features of the cells sensitivity of primary cultures in respect to protocol-approved chemotherapy drugs and changes in the Interleukin-6 (Il-6) level in the culture medium after the application of chemotherapy were established. The initial level of Il-6 exceeded 600.0 pg/ml in the cultural medium with histologically verified pilomyxoid astrocytoma cells, and ranged from 100.0 to 200.0 pg/ml in the medium at cultivation of ganglioneuroblastoma and pilocytic astrocytoma. A decrease in the Il-6 level in the medium culture of primary tumors cells was observed after the application of chemotherapeutic agents on the cells of pilomyxoid astrocytoma, astrocytomas, and pilocytic desmoplastic/nodular medulloblastoma. The production of Il-6 increased after application of cytostatic drugs on the cells of oligoastrocytomas. A decrease in Il-6 level after application of Cisplatin and Methotrexate and a 5-10 fold increase in the level of Il-6 after application of Etoposide, Carboplatin, Cytarabine, and Gemcitabine were registered in the medium with ganglioneuroblastoma. To improve the cytotoxic action of chemotherapeutic agents, the combined application of cytostatics with heterocyclic compounds was carried out. A computer modeling of ligand-protein complexes of carbamide using the Dock 6.4 and USF Chimera program packages was performed with molecular mechanics method. Special attention was drawn to the ability of several isoxazole heterocycles and isothiazolyl to inhibit the tyrosine kinase. It was proved in vitro that the joint application of chemotherapeutic agents and heterocyclic compounds could reduce the concentration of the cytostatic factor by 10 or more times, having maintained the maximum cytotoxic effect. It was assumed that the target amplification of cytotoxic action of chemotherapeutic agents had prospects for reducing toxic side effects of chemotherapy in vivo, which would be carried out only after the preclinical studies.

4,5-Dichloro-1,2-thiazol-3-amine was synthesized starting from accessible 4,5-dichloro-1,2-thiazole-3-carbonyl azide and -3-carboxamide via Curtius and Hofmann rearrangements, respectively. The procedure involving Curtius rearrangement was found to be more advantageous from the preparative viewpoint.

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.

By acylation of benzene, toluene, and p-xylene with 4,5-dichloroisothiazole-3-carbonyl chloride the corresponding aryl 4,5-dichloroisothiazol-3-yl ketones were obtained. By reaction of 4,5-dichloroisothiasol-3-yl 4-methylphenyl ketone with piperidine, alkyl(aryl) thiolates, sodium alcoholates, and 2,4-dinitrophenylhydrazine were synthesized 4-methylphenyl 5-piperidyl-4-chloroisothiazol-3-yl ketone, 5-alkyl(aryl)sulfanyl-4-chloroisothiazol-3-yl 4-methylphenyl ketones, 5-alkoxy-4-chloroisothiazol-3-yl 4-methylphenyl ketones, and 2,4-dinitrophenylhydrazone of the initial ketone respectively.