３-フェニル-２-クロロプロピオフェノンのトリフルオロエタノール中の光反応 Photosolvolysis of 3-Phenyl-2-chloropropiophenone in Trifluoroethanol

The photoirradiation of phenacyl chrolides in polar solvent exhibit phenyl-migration known as Photo Favorskii rearrangement. The photosolvolysis of 3-phenyl-2-chloropropiophenone in 2,2,2 trifluoroethanol (TFE) afforded 3,2-diphenyl propionic acid trifluoroethyl ester derived from the Photo-Favorskii rearrangement (k_Fav), accompanied by the two other types of products. One of the other product was 3-phenyl-2-trifluoroethoxypropiophenone which is derived from the nucleophilic substitution (k_S) at the reaction center, and the other was 2-phenyl-3-trifluoroethoxypropiophenone obtained by the migration of the phenyl group at the 3- position (k_R). The introduction of electron donating p-MeO group on the benzoyl group less affected the product ratio between k_R / k_S, whereas the k_Fav / k_S ratio was decreased by the factor of 2. The former result indicates the k_R and k_S products were derived from phenonium ion intermediate, while kFav product was derived from phenacyl radical or geminate ion pair.