SELECTIVITY IN INTERMOLECULAR AND INTRAMOLECULAR PHOTOCYCLOADDITION OF ETHENES TO BENZENOID COMPOUNDS

The formation of isomers from the inter- and intra-molecular meta phot ocycloaddition of ethenes to the benzene ring has been specifically di rected using the addend substituents in order to cause an asymmetric d istortion of the C-6 ring during the reaction, and to induce non-synch roneity into the addition process. The latter influence in the intramo lecular reaction is achieved by the presence of a heteroatom in the li nking tether which also provides a convenient access to linear and ang ular heterotriquinanes. The meta photoaddition can be induced by sunli ght exposure of appropriately substituted arene-ethene bichromophores.