Reversible photorearrangement of N-substituted phthalimides: a flash photolysis study

Phosphorescence and fluorescence studies of a series of N-substituted phthalimides suggest that the photochemical cyclization reaction of dialkylaminoalkyl substituted compounds probably occurs through the (n,π*) singlet excited state. Flash photolysis of these and other, simpler phthalimides reveals an unrelated reaction involving two types of transient intermediate. One is a triplet state and the other a much longer-lived species which is postulated to be an isomer of the imide produced by a 1,3-shift. The isomer reverts to the imide, and the effect of substituent and of solvent on the decay is discussed.