Abstract: Upon irradiation, 5-dicyanomethylenebicyclo [2.2. 2] octene(2) gives a highly strained compound, 2, 2-dicyanotricyclo [4.2. 1.01'3] nonene(6) in good yield. Of additional interest isthe observation that the starting material 3 can be quantitatively regenerated from the photoproduct 6 with release of 28.8 kcal/mol.-