Accessing Sterically Congested Benzannulated Cyclic Aryl Ethers via Photoredox Decarboxylative Giese-Type C2–C3 Bond Formation

The visible-light-driven photocatalytic decarboxylation of α-aryloxy carboxylic acids produces α-oxy carbon-centered radicals that undergo intramolecular Giese addition to form 2,3-dihydrobenzofurans, chromans, 2,3,4,5-tetrahydrobenzo[b]oxepines, and 3,4,5,6-tetrahydro-2H-benzo[b]oxocines. In contrast to the existing methods, this unconventional strategy for the construction of five-, six-, seven-, and eight-membered oxygen heterocycles via the formation of the C2–C3 bond enables the synthesis of sterically demanding O-heterocycles bearing multiple substituents at the C2 and C3 positions. The mild reaction conditions render these transformations highly chemoselective and compatible with various functional groups.