3-(2-Methylprop-2-en-1-yl)-2-sulfanylidene-7-(trifluoromethyl)-2,3-dihydroquinazolin-4(1H)-one reacted with halogens (bromine and iodine), chalcogen tetrahalides, andp-methoxyphenyltellurium trichloride in a regioselective manner to give linearly fused 2-halomethyl-2-methyl-5-oxo-8-(trifluoromethyl)-2,3-dihydro-5H-[1,3]thiazolo[2,3-b]quinazolinium trihalides, 2-methyl-5-oxo-2-[(trihalo-lambda(4)-chalcogenyl)methyl]-8-(trifluoromethyl)-2,3-dihydro-5H-[1,3]thiazolo[2,3-b]quinazolinium halides, and 2-{[dichloro(4-methoxyphenyl)-lambda(4)-tellanyl]methyl}-8-(trifluoromethyl)-2,3-dihydro-5H-[1,3]thiazolo[2,3-b]quinazolin-5-one, respectively.