Dimethyl 4,5-di-chloro-phthalate.

While endeavoring to synthesize new chlorinated ligands for ruthenium-based metathesis catalysts, the title compound dimethyl 4,5-di-chloro-phthalate, C 10 H 8 Cl 2 O 4 , was prepared from commercially available 4,5-di-chloro-phthalic acid in ∼77% yield. The title mol-ecule, which also finds utility as a precursor mol-ecule for the synthesis of drugs used in the treatment of Alzheimer's disease, shows one carbonyl-containing methyl ester moiety lying nearly co-planar with the chlorine-derivatized aromatic ring while the second methyl ester shows a significant deviation of 101.05 (12)° from the least-squares plane of the aromatic ring. Within the crystal, structural integrity is maintained by the concerted effects of electrostatic inter-actions involving the electron-deficient carbonyl carbon atom and the electron-rich aromatic ring along the a -axis direction and C-H ⋯ O hydrogen bonds between neighboring mol-ecules parallel to b .