Diethyl 2,3-dihydrothieno[3,4-b]-1,4-dioxine-5,7-dicarboxylate

The title compound, C12H14O6S, is a dicarboxylic acid diethyl ester of 3,4-ethylenedioxythiophene, which is a component of electrically conductive poly(3,4-ethylenedioxythiophene) (PEDOT). The ethylene group is disordered over two sites with occupancy factors 0.64 and 0.36. Both the carbonyl groups are coplanar with the thiophene ring. The molecules form centrosymmetric dimers with an R22(12) coupling by intermolecular C—H...O hydrogen bonds [3.333 (5) ] at the ethoxycarbonyl groups. The dimer units are arranged to form a ribbon-like molecular sheet.