Visible-light–enabled excited-state dearomatization reactions

Dearomatization reactions stand as a cornerstone strategy for constructing pharmacologically pivotal saturated rings. Photoexcitation reshapes the electron distribution within the frontier molecular orbitals of aromatics, thereby unlocking dearomatization pathways inaccessible in the ground state and furnishing structurally distinct molecular motifs. Contemporary synthetic methodologies leverage three discrete mechanistic paradigms to achieve this electronic activation: direct excitation, energy-transfer photocatalysis, and exciplex formation. These precisely tuned energy-delivery modes enable the dearomatization of a diverse array of (hetero)arenes, including highly robust substrates such as naphthalenes and benzenes, under mild reaction conditions. This review spotlights recent representative advances in these excited-state transformations. We envision that this synopsis will fuel ongoing innovation in the burgeoning field of photochemical dearomatization.