Photochemically Induced Metathesis Reactions of Tetradehydrodianthracene: Synthesis and Structure of Bianthraquinodimethanes

Relief of strain is the driving force for the 2 + 2 cycloaddition and subsequent 2 + 2 cycloreversion of 1 with both open-chain and cyclic alkenes. The metathesis can even be performed with benzene as the olefin component Eq. (a). The product can be roughly described as a ribbon- or beltlike conjugated system.