Photoinduced Lanthanum Catalysis: C-H Activation and Spirocyclization

Lanthanum-catalyzed tandem C(sp³)-H oxidation/spirocyclization under ambient conditions using molecular oxygen is reported. This method exhibits broad functional group tolerance and enables precise functionalization of complex scaffolds. The reaction proceeds via a light-absorbing lanthanum complex assembled through in situ multicomponent coordination, operating through synergistic intramolecular energy transfer and single-electron transfer pathways. This approach provides efficient access to diverse N,O- and O,O-spirocyclic compounds. Mechanistic studies establish that lanthanum bromide acts not only as the photosensitizer metal center, generating bromine radicals for C-H cleavage, but also as a Lewis acid catalyst promoting cyclization and spirocyclization.