Електрофільна циклізація 6-металілтіо-5-феніл-1,5-дигідро-4Н-піразоло[3,4-d]піримидін-4-ОНУ n-метоксифенілтелуртрихлоридом

Abstract

Condensed derivatives of pyrazolo[3,4-d]pyrimidine attract attention as promising antibacterial drugs, kinase inhibitors, xanthine oxidase, and also have fungicidal and cytotoxic properties. The structural fragment of pyrazolopyrimidine is widely used to develop new effective medicines. A promising direction in this regard is the construction of condensed derivatives of pyrazolopyrimidine by the method of electrophilic intramolecular cyclization. In this paper, the direction of the electrophilic intramolecular cyclization of 6-methylthio-5- phenyl-1,5-dihydro-4H-pyrazolo[3,4-d]pyrimidine-4-one with p-methoxyphenyltellurium trichloride with the involvement of the nucleophilic center (the endocyclic nitrogen atom) is investigated. The interaction of p-methoxyphenyltellurium trichloride with 6-methanylthio-5-phenyl-1,5-dihydro-4Hpyrazolo[ 3,4-d]pyrimidin-4-one was carried out in acetic aqueous acid at room temperature for 8 hours. It has been established that irrespective of the ratio of reagents, the annulation of the thiazoline ring to the pyrimidine occurs with the formation of tricyclic condensed system of the angular structure. It should be noted that the molecular complex of p-methoxyphenyltellurium trichloride with thiazolinopyrazolopyrimidine with the participation of Sulfur atom is formed. The formation of the complex is evidenced by the presence in the spectrum of H-NMR of different signals of protons of two p-phenylene cycles. The use of a double excess of p-methoxyphenyltellurium trichloride increases the yield of the desired cyclization product 8-methyl-4-oxo-5-phenyl-8-{[dichloro(4-methoxyphenyl)- telluro]methyl}-4,5,7,8-tetrahydro-1H-pyrazolo[4,3-e][1,3]-thiazolo[3,2-a]pyrimidine-9-yium chloride. Consequently, the electrophilic intramolecular cyclization of 6-methylthio-5-phenyl-1,5- dihydro-4H-pyrazolo[3,4-d]pyrimidin-4-one with methoxyphenyltellurium trichloride passes selectively with the angular annulation of the thiazoline cycle. The optimal conditions for the preparative synthesis of the thiazolinopyrazolopyrimidine chloride molecular complex with p methoxyphenyltellurium trichloride are found. Keywords: еlectrophilic cyclization; p-methoxyphenyltellurium trichloride; 6-methylthio-5- phenyl-1,5-dihydro-4H-pyrazolo[3,4-d]pyrimidin-4-one; molecular complex; thiazolinopyrazolopyrimidine.