Samarium(II)-mediated spirocyclization by intramolecular aryl radical addition onto an aromatic ring.

Samarium(II)-mediated spirocyclization by intramolecular addition of aryl radicals onto an aromatic ring was achieved by the reaction of N-(2-iodophenyl)-N-alkylbenzamides with SmI2 in the presence of HMPA, yielding spirocyclic indolin-2-one derivatives. The ether congeners afford spirocyclic benzofuran derivatives in moderate yields by aryl radical addition onto a benzene ring without having an electron-withdrawing group. The reaction with other aryl groups such as naphthalene and indole rings is also described.