Functionalization of the benzobicyclo[3.2.1]octadiene skeleton via photocatalytic oxygenation of thiophene and furan derivatives: The impact of the type and position of the heteroatom

Photocatalytic oxygenations of a furan and two thiophene derivatives of benzobicyclo[3.2.1]octadiene have been realized by using anionic and cationic manganese(III) porphyrins as catalysts. The replace of oxygen with sulfur in the heteroaromatic ring considerably decreased the reactivity of these heterocyclic compounds, probably due to the increased aromaticity. The end-products of the oxygenation of the thiophene derivatives significantly deviated from most of those formed from the corresponding furan compounds; the lower reactivity of the thiophene ring enhanced the role of the out-of-ring carbon atom in the reaction pathways. Besides, deviating from the behavior of the furan compounds, the types of the end-products formed from the corresponding thiophene derivatives did not depend on the charge of the photocatalyst, neither on the oxygen concentration. However, also in this case, the position of the heteroatom in the aromatic ring strongly affects the formation of the end-products.