The photo-Fries reaction of a series of phenyl, naphthyl and 1-naphthylmethyl esters allowed significant product selectivities when carried out within zeolites. Unlike isotropic media, which allow a range of products, zeolites generally afford a single product, as a result of the rearrangement of the acyl fragment to the 2-position on the aromatic ring. Even with decarbonylations of naphthyl esters, which usually yield a variety of products, the ortho isomer predominates within zeolites. This selectivity is due to an interaction between the initially formed radicals and the intrazeolite cations, limiting the mobility of the radicals and prompting recombination at the nearest available position. When the cations in the zeolites are heavy atoms, such as cesium and tellurium, facile intersystem crossing into the excited triplet state is found leading to increased phosphorescence. These indicate that good control is possible on photoproduct formations within zeolites.
ASJC Scopus subject areas
- Chemical Engineering(all)