Abstract The title substances and their [1] benzothieno analogues were synthesized by reaction of 3-allyl-2-mercapto-([1] benzo) thieno-[2.3—d] pyrimidine-4 (3 H)-ones with Br 2 to 2-bromomethyl-2.3-dihydro-thiazolo [3.2—a]([1] benzo-) thieno [2.3—d] pyrimidine-5-ones ...