Electrocarboxylation of 2-methylhalogen-9,10-anthraquinones

Herein we propose a new synthetic route for the production of 9,10-anthraquinone-2-ethanoic acid (AQEA) by electrocarboxylation of 9,10-anthraquinone-2-bromo-methyl (BrMAQ) or 9,10-anthraquinone-2-chloro-methyl (ClMAQ). Electrocarboxylation of anthraquinones appears as an alternative for synthesizing their respective carboxylic acids. Electrosyntheses were carried out using N,N-dimethylformamide (DMF) as solvent, NaClO₄ as electrolyte and metallic magnesium as sacrificial anode. One of electrolysis products was AQEA, which was isolated, purified and then analysed by IR, RMN and high performance liquid chromatography (HPLC). Electrocarboxylation selectivity to AQEA ranged on average from 32 to 40% using ClMAQ and BrMAQ, respectively.