PHOTOCYCLIZATION REACTIONS IN PRIMARY AMINES - CONVENIENT SYNTHESIS OF 1,4-DIHYDROPHENANTHRENE

Photocyclization reactions have been widely investigated, and the synthetic and mechanistic aspects of this type of photoreaction have been amply reported. For example, the photooxidative cyclization of stilbenes to phenanthrenes is a reaction of remarkable generality and synthetic utility for the preparation of various condensed aromatic hydrocarbons. Although the chemical and physical aspects of the interactions of aromatic hydrocarbons with primary, secondary, and tertiary amines have been extensively studied and discussed, the first study into the interactions between an amine (e.g., pyrrole, N-methylpyrrole) and an excited singlet stilbene molecule (which undergoes photocyclization) was reported by Kubota and Sakurai as recently as 1972. More recently-still, Lewis and Ho investigated the interactions between singlet trans-stilbene and several secondary and tertiary alkylamines in polar and nonpolar solvents.In all cases it was shown that the photolytic reactions resulted in addition of the amine to the olefenic bond rather than cyclization. © 1979, American Chemical Society. All rights reserved.