PHOTOCHEMICAL-REACTION OF PHTHALIMIDES AND DICYANOPHTHALIMIDES WITH BENZYLIC DONORS

Irradiation of phthalimides in the presence of benzylic donors PhCRHX (R=H, Ph, X=H, SiMe3, CHPh2, CHOCH2CH2O) proceeds via electron transfer and radical cation cleavage, resulting in benzylation at the carboximide moiety to yield 3-benzyl-3-hydroxyisoindol-1-ones. With 4,5-dicyanophthalimides substitution of benzyl for a cyano group is a competitive, and in some cases predominating, pathway. A rationalization is proposed on the basis of the in cage vs out of cage radical cation cleavage. In the first mechanism, the radical anion of the dicyanophthalimide, where spin and charge are differently located, probably assists the radical cation fragmentation.