Photochemical strategies in divalent samarium catalysis

Divalent samarium reagents, particularly samarium diiodide (SmI₂), have long been recognized as the most powerful and versatile single-electron reductants in organic synthesis. Several catalytic strategies have been developed for Sm(II) chemistry over the past three decades, including approaches based on metal co-reductants, electrochemical reduction, and radical relay mechanisms. Photochemical strategies have recently emerged as new platforms for catalytic Sm(II) chemistry, leading to the development of a broad range of reductive transformations. This review highlights the recent progress in the photochemical generation of Sm(II) species and their applications in organic synthesis.