Cycloaddition Elimination Reactions of Phenylisocyanate with Oxo and Thiono Derivatives of Aliphatic Substituted 5‐Imino‐1,2,4‐dithiazolidines and 3‐Thiono‐1,2,4‐thiadiazolidines (Mustard Oil Oxides and Sulfides)
5‐Imino‐1,2,4‐dithiazolidin‐3‐ones 1 and‐3‐thiones 3 react with phenylisocyanate to afford 5‐imino‐1,2,4‐thiadiazolidin‐3‐ones 6. In comparison isomeric 3‐thiono‐1,2,4‐thiadiazolidin‐5‐ones 2, 5, and ‐5‐thiones 4 yield 3‐imino‐1,2,4‐thiadiazolidin‐5‐ones 8, 10, and ‐5‐thiones 7. Thermolyses of thiadiazolidines 5 and 10 afford further 1,2,4‐thiadiazolidines 9, 11. Compounds 8–11 are available also by reaction of substituted guanidines with chlorocarbonyl sulfenylchloride.