Mechanism of the Triplet-Sensitized Photolysis of N-(1-Naphthylsulfonyl)-N-phenyl-O-(p-toluoyl)hydroxylamine

Article abstract of DOI:10.1246/bcsj.65.2789

The title hydroxylamine (SO2NT) undergoes triplet-sensitized photolysis in the presence of benzophenone (BP) or its derivative to give rearrangement and fragmentation products.Observations of the toluoyloxyl-migrated products, which are not obtained by the triplet-sensitized photolysis of N-(1-naphthoyl)-N-phenyl-O-(p-toluoyl)hydroxylamine (NT), indicate the occurrence of an efficient intersystem crossing of a triplet radical pair initially formed into a singlet radical pair.Internal heavy-atom-like effects of the partially charged sulfonyl sulfur and oxygen atoms are suggested to be responsible for this effective spin inversion.The finding that benzil, both the excited singlet and triplet states of which lie below those of SO2NT, causes a sensitized photolysis of this hydroxylamine to afford the same rearrangement and fragmentation products establishes the fact that a reaction sensitized by BP or its derivative proceeds through a triplet-exciplex intermediate.The effects of the solvent polarity and substituents of BP on the quantum yields for the reaction are discussed.