Photochemistry of 9-[2-(N-Substituted Aminotnethyl)-1-naphthyl]phenanthrenes. Intramolecular Addition of Amines to Excited State of Phenanthrene in Conformationally Rigid System

Irradiation of benzene solutions of 9-[2-(N-substituted aminomethyl)-1-naphthyl]phenahthrenes (3a–d) gave pyrroline derivatives by the attack of the NH group on the C-9 carbon atom of the phenanthrene ring. The reactions were highly selective in regio- and stereochemical senses, and occurred through exciplexes formed by intramolecular interaction between the ammo group and the excited phenanthrene moiety in 3a–d. Mechanistic features of these photoreactions are discussed on the basis of chemical and photochemical properties of substrates and products.