Synthesis and crystal structure of tetramethyl (E)-4,4⁰-(ethene-1,2-diyl)bis(5-nitrobenzene-1,2-dicarboxylate)

The title compound, C₂₂H₁₈N₂O₁₂, was obtained as a by-product during the planned synthesis of 1,2-bis(2-nitro-4,5-dimethyl phthalate)ethane by oxidative dimerization starting from dimethyl-4-methyl-5-nitro phthalate. To identify this compound unambiguously, a single-crystal structure analysis was performed. The asymmetric unit consists of half a molecule that is located at a centre of inversion. As a result of symmetry restrictions, the molecule shows an E configuration around the double bond. Both phenyl rings are coplanar, whereas the nitro and the two methyl ester groups are rotated out of the ring plane by 32.6 (1), 56.5 (2) and 49.5 (2), respectively. In the crystal, molecules are connected into chains extending parallel to the a axis by pairs of C—H O hydrogen bonds that are connected into a tri-periodic network by additional C—H O hydrogen-bonding interactions.