Abstract: Phenols, produced at an annual volume exceeding ten million tons, are widely used in various key organic transformations due to their low cost. In introductory chemistry courses, the reactions of phenols typically involve substitutions at the electron-rich aromatic ring or the hydroxyl oxygen, leaving the inert C―O bond intact in the final products. To expand the utility of phenols, researchers have developed metal-catalyzed strategies that cleave the C―O bond by introducing activating groups at the oxygen atom, enabling efficient deoxygenative coupling reactions. However, these methods often require harsh conditions and may result in metal contamination, limiting their use in pharmaceutical and other sensitive applications. To address these limitations, recent studies have demonstrated that simple phenol derivatives can selectively cleave the inert C―O bond under mild conditions, using light or electricity to generate aryl radicals. The high reactivity and selectivity of these radicals enable novel and efficient chemical transformations, offering new strategies for the application of phenols in organic synthesis. This paper reviews recent advancements in using trifluoromethanesulfonates, phosphates, and carbonates of phenols as aryl radical precursors, discussing the challenges and breakthroughs in constructing complex molecules with high precision. This review aims to broaden the knowledge of advanced students in the field.

Key words: Phenols, Inert C-O bond, Selective cleavage, Aryl radicals, Photosynthesis, Electrosynthesis