Photocycloaddition of Cyanonaphthalenes to 1,3-Cyclohexadiene

Article abstract of DOI:10.1021/jo971748b

To prevent secondary processes due to facile thermal reaction, low-temperature irradiations of cyanonaphthalenes and 1,3-cyclohexadiene through a Pyrex filter were conducted. Along with the identification of the products, the results of the triplet-sensitized photoreaction of the irradiated mixture, low-temperature ¹H NMR study of the irradiated mixture, and the Cope rearrangement reaction of some products suggested that the primary major products are the corresponding exo-[4 + 4] adducts fused at 1,4 position of the naphthalene skeleton and the syn-[2 + 2] adducts fused at 1,2 position. The formations of the primary products in these singlet-state photocycloaddition reactions were interpreted by primary and secondary orbital interactions. A rationalization for the previous results on the photoreactions at room temperature was also provided.