Photoinduced Radical-Polar Crossover Cyclization for the Synthesis of α-Exo-Alkenyl γ-Lactones

α-Exoalkenyl γ-lactone skeletons are of great significance due to their synthetic challenges and the diverse biological properties exhibited by numerous natural and synthetic molecules. In this work, we developed an alternative method for the synthesis of α-exoalkenyl γ-lactones via visible light-induced radical-polar crossover cyclization (RPCC) reaction. These reactions proceed under mild photochemical conditions in the presence of fluorescein sodium as photocatalyst, yielding structurally diverse γ-lactones conveniently, while demonstrating good functional group tolerance and a broad substrate scope. Furthermore, a plausible RPCC mechanistic pathway is proposed based on control experiments.