chapter  2
116 Pages

Photocycloaddition and Photoaddition Reactions of Aromatic Compounds

Photocycloaddition and photoaddition can be utilized for new carbon-carbon and carbon-heteroatom bond formation under mild conditions from synthetic view­ points. In last three decades, a large number of these photoreactions between elec­ tron-donating and electron-accepting molecules have been appeared and dis­ cussed in the literature, reviews, and books [1-10]. In these photoreactions, a variety of reactive intermediates such as excimers, exciplexes, triplexes, radical ion pairs, and free-radical ions have been postulated and some of them have been detected as transient species to understand the reaction mechanism. Most of reac­ tive species in solution have been already characterized by laser flash photolysis techniques, but still the prediction for the photochemical process is hard to visu­ alize. In preparative organic photochemistry, the dilemma that the transient species including emission are hardly observed in the reaction system giving high chemical yields remains in most cases [1 1 ,1 2 ].