Abstract Irradiation of 2, 3-dimethylbut-2-enyl 1-cyano-2-naphthylmethyl ether in the presence of Eu (hfc) 3 in benzene site-selectively afforded the (2π+ 2π) intramolecular photocycloadduct at the 1, 2-position on the naphthalene ring. On the other hand, allyl 1- cyano-2-naphthylmethyl ether in the presence of Mg (ClO 4) 2 in acetonitrile gave the photocycloadduct at the 3, 4-position as a sole product.
