Irradiation of an acetonitrile solution of para-dicyanobenzene (1), 3, 3- diphenyltetrahydrofuran (2), and magnesium perchlorate leads to the formation of 4, 4- diphenyl-1, 3-dioxane (7). Similarly, irradiation of an acetonitrile solution of 1, methyl 2, 2- diphenylcyclopentyl ether (5), and magnesium perchlorate leads to the formation of 6, 6- diphenyl-2-methoxytetrahydropyran (8). The mechanism proposed for these reactions ...