Functionalization of the benzobicyclo[3.2.1]octadiene skeleton via photocatalytic oxygenation of furan and benzofuran derivatives

Photocatalytic oxygenations of a furan and a benzofuran derivative have been realized by using anionic and cationic free-base porphyrins as well as their manganese(III) complexes under various reaction conditions. In the case of the furan derivative, application of these catalysts resulted in deviating reaction pathways generating different products. Annulation of a benzene to the outer side of the furan ring, however, led to the formation of only one type of product, independently of the photocatalyst used. Different oxygenation mechanisms leading to the same end-product, the 10-membered keto-lactone derivative, have been suggested for the metalloporphyrins and the corresponding free bases.