Azolidine-4-thiones,their derivatives and analogs

The reaction of rhodanine with P₂S₅ in various solvents was investigated with a view to converting the CO group to CS. Using dry dioxane, a 90% yield of the hitherto unknown thiazolidine-2, 4-dithione (thiorhodanine I) was obtained, distinguished by having a quite active methylene group, which readily coupled with diazonium salts in neutral solutions, as well as condensing with aldehydes in methanol. It was very readily oxidized. Its 4-thione group condensed with amines. A qualitative test for I was reaction with p-dimethylaminobenzaldehyde to give an intense red color. 5-Arylidene-5-arylazo and 4-arylimino derivatives of I have been isolated.