2-(2-Methylprop-2-en-1-ylsulfanyl)quinoline and 2-(3-methylbut-2-en-1-ylsulfanyl)quinolines reacted with iodine to give dihydrothiazolo[3,2- a]quinolinium polyiodides, whereas iodination of 2-(but-3-en- 1-ylsulfanyl)quinoline afforded dihydro[1,3]thiazino[3,2- a]quinolinium polyiodide.