1,2-Dithiole-3-thiones and 1,2,4-dithiazole-3-thiones react with dibenzoylacetylene to provide thioacylmethylene or thioacylimino-1,3-dithiole adducts respectively. Some of these, on sulfurization, provide thieno[3,4d]-1,3-dithiole derivatives, but in others a retro-1,3-dipolar reaction predominates. Further reaction of the initial adducts with more dibenzoylacetylene provides spiran compounds.
3-Alkylthio-1,2,4-dithiazolium salts are most conveniently made by alkylation of the corresponding 1,2,4-dithiazole-3-thiones by dimethyl sulfate. These salts readily undergo nucleophilic attack by amines in position 3, with loss of a methylthio group. Hydrogen peroxide oxidation, or chlorination, of the thiones gives the corresponding dithiazole-3-ones.