Catalyst- and oxidant-free electrochemicalpara-selective hydroxylation ofN-arylamides in batch and continuous-flow

Hydroxyl compounds serve as key building blocks in the preparation of biologically active natural products and drugs. Traditionally, hydroxylation of the aromatic ring is achieved using stoichiometric amounts of oxidants, which leads to low atom-economy, undesired by-products, potential explosion risk and environmental pollution. Recently, electrosynthesis has attracted increasing attention as it employs clean electrical energy to promote redox reactions avoiding the use of oxidants. However, due to the poor mass and heat transfers of batch cells, low productivity and selectivity limit its further application. Herein, we develop a catalyst-, oxidant-, acidic solvent- and quaternary ammonium salt-free electrochemicalpara-selective hydroxylation ofN-arylamides at room temperature in batch and continuous-flow. This proposal features excellent position control and water, air and functional group tolerance. Also, it is easy to scale up with higher productivity and selectivity using a flow electrolysis cell.