SUPPORTED REDOX PHOTOSENSITIZERS FOR THE ACTIVATION OF ALKYLAROMATICS TOWARDS OXYGEN

Several 2,4,6-trinitrobenzene derivatives and 2,4,7-trinitrofluorenone were grafted on silica and used as supported electron-acceptor photosensitizers. The grafting was effected by two methods: reaction of a halogenated derivative with aminopropyl silica or condensation on silica of the electron acceptor previously transformed into monochlorosilane. The oxidation of 4-methyl anisole by redox photosensitization was used as a test reaction to compare the efficiencies of these heterogeneous photosensitizers. Silica grafted 2,4,6-trinitrobenzene was then used to oxidize 4-substituted methyl aromatic compounds into the corresponding aromatic aldehydes with 76%-90% yields and 100% selectivity.