ARYLTELLUROCHLORINATION OF 5-ARYL(HETERYL)SUBSTITUTED N-ALLYL-1,2,4-TRIAZOLE-3-THIONE DERIVATIVES

Abstract

Condensed heterocycles based on 1,2,4-triazole have a wide range of biological activity. The introduction of a pharmacophore fragment of an aryl tertiary residue into their composition can significantly increase the bioactivity of the obtained compounds. Therefore, the synthesis of condensed derivatives of symmetrical 1,2,4-triazole with aryltellurium fragment is an urgent task. One of the most convenient and effective methods for introducing an aryltellurium fragment into such systems is the me­thod of electrophilic intramolecular cyclisation of alkenyl derivatives of azaheterocycles. The aim of this work was to determine the effect of the nature of the substituent at position five of the initial N-allyl derivatives of 1,2,4-triazol-3-thi­one on the regioselectivity of electrophilic heterocyclization with p-methoxyphenyltellurium trichloride. The reaction of tellurium-induced heterocyclisation of N-allyl-substituted 1,2,4-triazole-3-thione with was carried out in acetic acid medium at room temperature under stirring for 12 hours. It was found that the reactions of 5-aryl(heteryl)substituted N-allyl derivatives of 1,2,4-triazole-3-thione with p-methoxyphenyltellurium trichloride lead to the formation of chlorides 6-((dichloro(4-metho­xyphenyl)-λ4-tellanyl)methyl)-5,6-dihydrothiazolo[2,3-c][1,2,4]triazol-1-ium chlorides with an exocyclic p-methoxyphenyltellu­rium fragment. The yield of the obtained thia­zo­lotriazo­lium salts was 68-87%. It should be noted that the use of a double amount of elect­rophilic reagent did not lead to the formation of a thiazolotriazole complex with p-methoxyphenyltellurium trichloride, which was observed during the heterocyclisation of S-alkenyl derivatives of 1,2,4-triazole. Thus, the tellurium-induced cyclization of 5-substituted N-allyl derivatives of 1,2, 4-triazol-3-thione derivatives by p-methoxyphenyltellurium trichloride is regioselective with the formation of 6-((dichloro(4-methoxyphenyl)-λ4-tellanyl)methyl)-5,6-dihydrothiazolo[2,3-c][1,2,4]triazol-1-ium chlorides and annulation of the thiazoline cycle. The introduction of aryl and heteryl substituents of different nature does not affect the regioselectivity of the heteroannulation process.