PHOTOCHEMISTRY AND PHOTOPHYSICS OF AROMATIC SULFOXIDES .3. ALPHA-CLEAVAGE AND THE ROLE OF THE SULFENIC ESTER

The photochemistry of aryl benzyl sulfoxides is described. The initial event is homolytic cleavage to form a singlet sulfinyl/benzyl radical pair. This radical pair partitions between reversion to starting mate rial with at least partial racemization and closure to form a sulfenic ester. With acetone sensitization, the primary radical pair also unde rgoes quite significant escape, leading to formation of diphenylethane and aryl arenethiosulfonates. Secondary photolysis of the sulfenic es ter leads exclusively to S-O homolysis, yielding the radical pair from which isolated products are derived. Quantum yields and other mechani stic observations are discussed.