Halogenoheterocyclization of terminal and internal 2-allylthio-3-methyl(phenyl)-7-trifluoromethylquinazolin-4-ones

The regioselectivity of halogenation of terminal and internal thioethers of 7-(trifluoromethyl)quinazolin-4(3H)-ones was investigated. It is proven that the direction of halocyclization of allyl thioethers depends on the presence of a substituent at the terminal carbon atom of the allyl moiety. The cyclization of allyl, methallyl and prenyl thioethers leads to the annulation of thiazole cycle with the formation of thiazolo[3,2-a]quinazolinium trihalides while cyclization of cinnamyl thioether forms thiazino[3,2-a]quinazolinium trihalides with the additional thiazine cycle.