Versatile Synthesis of Triptycene Di- and Tetracarboxylic Acids

A simple two-step synthesis of triptycene di- and tetracarboxylic acids is reported. Diels-Alder reaction between dimethylanthracenes and appropriate arynes, generated in situ from anthranilic or dimethylanthranilic acid, afforded di- or tetramethyltriptycenes in 41-69% yields. Subsequent oxidation of the methyl groups with potassium permanganate provided the corresponding triptycene carboxylic acids in 86-96% yields.