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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.

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.

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.