Annelated furans. XVIII. The photocyclization of 2-methoxyphenyl phenyl ethers

Abstract

Irradiation of the polyfunctional 2-methoxyphenyl phenyl ethers obtained by degradation of lichen depsidones results in the formation of dibenzofurans by ring closure involving elimination of the elements of methanol. In contrast, simply substituted methoxyphenyl phenyl ethers underwent rearrangement on irradiation and produced hydroxybiphenyls. A mechanistic rationalization of these results has been proposed which invokes the initial formation of a diradical species upon irradiation. The formation of a stable product from this diradical intermediate can then be achieved by a variety of reaction pathways.