1‐Oxo‐1,3‐dithiolane (4) and its cis‐ and trans‐2‐methyl (5,6), ‐4‐methyl (7,8) and ‐5‐methyl (9,10) derivatives were prepared by oxidizing the corresponding 1,3‐dithiolanes (1–3) with NaIO4 in water. The oxides were purified and their isomers separated using thin layer chromatography. The structural characterization was carried out with 1H and 13C NMR spectroscopy and molecular modelling. The sulfoxides