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 (2Ï + 2Ï) 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(ClO4)2 in acetonitrile gave the photocycloadduct at the 3,4-position as a sole product.
Irradiation of 1-cyano-2-(2-oxa-4-alkenyl)naphthalenes in the presence of Eu(hfc)3 regioselectively afforded (2π+2π) intramolecular photocycloadducts at 1,2-position on the naphthalene ring in good yields. The salt and solvent effects in this photoreaction are described.