Electrochemical aromatic C–H hydroxylation in continuous flow

The direct hydroxylation of arene C–H bonds is a highly sought-after transformation but remains an unsolved challenge due to the difficulty in efficient and regioselective C–H oxygenation and high reactivity of the phenolic products leading to overoxidation. Herein we report electrochemical C–H hydroxylation of arenes in continuous flow for the synthesis of phenols. The method is characterized by broad scope (compatible with arenes of diverse electronic properties), mild conditions without any catalysts or chemical oxidants, and excellent scalability as demonstrated by the continuous production of 1 mol (204 grams) of one of the phenol products.