Energy transfer (EnT) photocycloadditions: beyond the [2 + 2] approach.

Energy-transfer (EnT) photocatalysis has rapidly emerged as a powerful platform in synthetic organic chemistry, enabling diverse molecular transformations with high selectivity. Consequently, it has unlocked reaction pathways that are inaccessible or challenging under conventional thermal conditions. These advantages have stimulated considerable interest in the development of sustainable methods based on EnT photocatalysis. The present review highlights recent (2022-2025) advances in photocycloadditions beyond the EnT-enabled [2 + 2] manifold. The discussion is organized according to reaction type, encompassing EnT-based [4 + 2] cycloadditions, [3 + 2] cycloadditions, 6π-photocyclizations, Norrish-Yang-type cyclizations, and miscellaneous cyclization reactions. Plausible mechanistic rationales are presented to provide insight into the underlying reaction pathways.