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

The title compound, C(12)H(14)O(6)S, 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 R (2) (2)(12) coupling by inter­molecular C—H⋯O hydrogen bonds [3.333 (5) Å] at the ethoxy­carbonyl groups. The dimer units are arranged to form a ribbon-like mol­ecular sheet.