Intramolecular [2+2] and [2+3] photocycloadditions of 2-(2-alkenyloxymethyl)naphthalene-1-carbonitriles and their photocycloreversion using glass-made microreactors were investigated in comparison with photoreactions under conventional batch conditions. Both the efficiency and regioselectivity were improved by use of glass-made microreactors. These results can be explained by thorough absorption of light and outflow of primary product from the reaction system.
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.