Photochemical reactions of benzene derivatives with electron-donor ethylenes

Abstract

The photoreactions of ethyl vinyl ether with benzonitrile, toluene, and anisole are reported and compared with those involving benzene as the arene. As the difference in ionisation potential between the addends decreases, the ortho-cycloaddition reaction becomes less favoured and the meta-process predominates. Regio- and stereo-isomers are formed in both photo-cycloaddition reactions. The meta-cycloadditions to toluene and anisole are exclusively 2,6- as are those of 2-methyl- and 2,3-dimethyl-but-2-ene to anisole. The effect of solvent on the mesa-cycloaddition of anisole and ethyl vinyl ether has not been observed in any other system and suggests the involvement of a polar species in the reaction pathway.