Irradiation of an acetonitrile-water solution containing 2-alkoxynaphthalene, an amine, and m-dicyanobenzene gave selectively 2-alkoxy-1-alkylamino-1,4-dihydronaphthalenes in relatively good yields. The aminodihydronaphthalenes were acetylated with Ac2O and then treated with BF3·OEt2 to give N-acetyl-1-alkylamino-2-tetralones in good yields.