Visible-Light-Enabled Lanthanum-Mediated Intramolecular Epoxy-Ring Opening/Dehydrogenative Lactonization

Catalytic C(sp(3))-H functionalization has afforded great opportunities to prepare organic substances, facilitating the derivatization of complex drugs and natural molecules. This letter describes an efficient and practical protocol for lanthanum-catalyzed continuous epoxy-ring opening and oxidative dehydrogenative lactonization under visible-light irradiation. Notably, the lanthanum catalyst also acts as a photocatalyst while acting as a Lewis acid in this reaction; therefore, no additional photocatalyst is required. We can conveniently prepare a series of diverse isochromanones with oxygen-containing spirocyclic structural units under a balloon-oxygen atmosphere at room temperature. Mechanistic studies and control experiments reveal that the in situ-generated lanthanum bromide should be crucial in the reaction.

Automated summary

This study presents an efficient and practical lanthanum-catalyzed reaction method for continuous epoxy-ring opening and oxidative dehydrogenative lactonization under visible-light irradiation. The lanthanum catalyst acts as both a Lewis acid and a photocatalyst in this reaction, eliminating the need for additional photocatalysts. The method allows for convenient preparation of isochromanones with oxygen-containing spirocyclic structural units.