5,6-Di-hydro-1,4-dithiine-2,3-di-carb-oxy-lic anhydride

In the title com-pound (systematic name: 2,3-di-hydro-1,4-dithiino[2,3-c]furan-5,7-dione), C₆H₄O₃S₂, the observed geometry agrees well with those of its phthalamide, thieno and hy-droxy analogs, and with a calculated geometry obtained by density functional theory (DFT) calculations. Specific structural features are an S-C-C-S torsion angle of -70.39 (17)° and S-C bonds to sp ²-hybridized C atoms approximately 0.1 Å shorter than those to sp ³-hybridized C atoms. Unlike the extended structures of the analogs, there are no directed inter-molecular inter-actions and the head-to-tail rows of mol-ecules that are a prominent structural motif of the packing can be rationalized in terms of optimized dipole-dipole inter-actions.