Electrophilic cyclization of propargyl thioethers of 3-methyl(phenyl)-2-(prop-2-yn-1-ylthio)-7-(trifluoromethyl)quinazolin-4(3H)-ones by tellurium tetrahalides

Abstract

The paper presents the results of the study of the process of electrophilic intramolecular cyclization of 3-methyl(phenyl)-2-(prop-2-yn-1-ylthio)-7-(trifluoromethyl)quinazolin-4(3H)-ones by tellurium tetrahalides. 3-Methyl(phenyl)-2-(prop-2-yn-1-ylthio)-7-(trifluoromethyl)quinazolin-4(3H)-ones were prepared by the alkylation of the corresponding thions with propargyl bromide in an alkaline alcohol medium. It is found that the interaction of propargyl thioethers of 3-substituted 2-thioxo-7-(trifluoromethyl)-2,3-dihydroquinazolin-4(1H)-ones with tellurium tetrahalides, which were obtained in situ from tellurium dioxide and six equivalents of corresponding concentrated hydrohalic acid, leads to the formation of halides of angular 4-methyl(phenyl)-5-oxo-1-((trihalotellanyl)methylidene)-8-(trifluoromethyl)-1,2,4,5-tetrahydrothiazolo[3,2-a]quinazolin-10-iums. The most optimal conditions for the tellurium-induced electrophilic heterocyclization of propargyl thioethers with tellurium terahalides are the use of glacial acetic acid as a solvent and stirring of the reaction mixture at room temperature for 24 hours. It is found that the electrophilic cyclization of 3-methyl(phenyl)-2-(prop-2-yn-1-ylthio)-7-(trifluoromethyl)quinazolin-4(3H)-ones by tellurium tetrahalides occurs stereoselectively with the formation of one configurational isomer. The influence of the nature of halogen in the electrophilic reagent and the substituent in position 3 of quinazoline is examined and it is found that these factors do not affect the regioselectivity of the electrophilic intramolecular cyclization process. As a result of the conducted study, potentially biologically active salts of tellurofunctionalized thiazolinoquinazolines of angular structure were received.