Methylene and arylidene bisnaphthols can be converted into 4,5,2’,3’‐dibenzo‐3‐grisa‐2’,4’‐dien‐6’‐ones under catalytic conditions in the presence of copper(II)‐tetramethylethylenediamine [CuCl(OH)(TMEDA)]2. The reaction simply proceeds under air at room temperature and the control of stereoselectivity is total, affording the only (RR+SS) diastereoisomer.

The catalytic oxidation under green conditions of pyrogallol into purpurogallin was performed by air with laccase model copper complexes or by plant extracts containing peroxidases in the presence of hydrogen peroxide. A study was conducted for turnip, depending on the amount of extract, the method of introduction and the pH. Optimization of these conditions made it possible to easily obtain pure purpurogallin with a yield of 78%.