INTRAMOLECULAR PHOTOINDUCED REARRANGEMENTS VIA ELECTRON-TRANSFER-INDUCED, CONCERTED BOND-CLEAVAGE AND CATION RADICAL RADICAL COUPLING

Intramolecular photoinduced electron-transfer concerted bond cleavage has been observed in both a phenylanthracene and a phenylnaphthacene sulfonium salt derivative to produce a singlet phenylaryl cation radical/radical pair. Subsequent, cation radical/radical coupling produces photorearrangement, which appears to be a kinetic process due to the correlation of the product distribution with spin densities in the phenylaryl cation radical. In the phenylanthracene derivative, amide and sulfide products are also formed, presumably from electron transfer from the radical to the cation radical within the solvent cage. The efficacy of the photoinduced electron transfer/bond cleavage and radical coupling is attributed to the concerted nature of the bond cleavage, close proximity of the aryl pi-system to the sulfonium moiety, as well as to the favorable thermodynamics for electron transfer.