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Photoinduced rearrangements of 3,3'-bis(arylbenzofurans).

Complex tetracyclic ring systems were assembled by a photoinduced rearrangement of 3,3'-bis(arylbenzofurans). Irradiation of 1 under N(2) atmosphere yielded the benzonaphthofurans 2 in 75-90% yield. When the reaction was conducted under an O(2) atmosphere in the presence of tetracyanoethylene (TCNE) a different reaction pathway was observed leading to the isolation of 3 as the major product. Also, the photochemical properties of these novel structures were investigated.