Electron-Transfer Photosensitized Oxygenation of Stilbene and Naphthalene Derivatives in the Presence of Acetate Ion. Controlling the Reaction of the Cation Radicals by Weak-Nucleophilic Salts

Abstract

Abstract The 9,10-Dicyanoanthracene (DCA)- or 9-cyanoanthracene-sensitized photooxygenation of trans-stilbene derivatives gave benzaldehyde derivatives efficiently in the presence of weak-nucleophilic salts, such as Et4NOAc and KOAc/18-crown-6 ether. The product distribution of this photooxygenation was apparently different from that of each photooxygenation in the presence of Mg(ClO4)2 and Et4NBF4 or in the absence of the salt. The DCA-sensitized photooxygenation of 2-methylnaphthalene gave phthalic acid and 4-methylphthalic acid in the presence of Et4NOAc. These products were different from the products generated from each photooxygenation in the presence of Et4NBF4 and KClO4 or in the absence of the salt. Also, such ring-oxygenation occurred in the DCA-sensitized photooxygenation of 2,3-dimethylnaphthalene and naphthalene in the presence of Et4NOAc. These photooxygenations in the presence of Et4NOAc proceeded by the addition of an acetate ion to the cation radical of the substrate generated by a photochemical electron transfer from the substrate to the sensitizer and the subsequent reaction with O2 and the related oxygen species.