Dye-sensitized photooxygenation of 2-phenylindole (1a) in methanol gave 2-phenyl-2-(2'-phenyl-3'-indolyl) indoxyl (2a) and 2-methoxy-2-phenylindoxyl (4a). The N-methyl products (2b,4b) were obtained from 1-methyl-2-phenylindole (1b) similarly. The product distribution of the reaction varied with the concentration of indoles (1) and the acidity of the reaction medium. A mechanism for the reaction was proposed. In the case of 1a, the proposed reaction intermediate, 2-phenyl- 3H-indol-3-one (3a) has been isolated in the same reaction carried out in acetonitrile.

Key words: SENSITIZATION, DYES