Photosubstitution reactions on aromatic and heteroaromatic rings evidence for addition and substitution mechanism

Article abstract of DOI:10.1016/S0040-4020(01)80966-2

Irradiation of a cyclohexane solution of hexafluorobenzene in the presence of benzophenone resulted in both, substitution and addition products. Similar photoreaction has been observed by irradiation of hexafluorobenzene in some alcohols in the presence of benzophenone. The reaction of pentafluorobenzene with methanol or cyclohexane resulted in the substitution of a 2-or 4-fluoro atom, while the reaction of pentafluoroanisole resulted in the formation of o-, m- and p-isomers. Irradiation of a cyclohexane solution or of an alcohol solution of octafluoronaphthalene yielded 1- and 2-substituted products. On the other hand, the photosubstitution of fluorine atom in pentafluoropyridine took place exclusively at the position four, thus forming 4-cyclohexyl or 4-(1-hydroxyalkyl) substituted products.