Mechanistic investigations of photochemical generation of quinone methides

Quinone methides are important intermediates in many chemical reactions that find application in synthetic chemistry and chemical biology. They are usually formed from substituted phenol derivatives. Synthetic organic chemists have developed a variety of ways to generate quinone methides, including photochemical generation, which is usually seen as a promising way of generating desired chemical products under mild conditions and with spatial and temporal control. Meanwhile, physical organic chemists and physical chemists have made much effort to investigate the mechanisms of photochemical generation of quinone methides in the solution phase over the past few decades. This review covers both old mechanistic studies, which used traditional physical organic methods, and recent mechanistic studies, which used ultrafast techniques, in this research topic. The use of ultrafast techniques has unraveled more photophysical and photochemical details of quinone methide photogeneration processes than that of conventional techniques.