Electron-transfer photofragmentation reactions: analogies and divergences of the reactivity of ditertiary amines as compared with aminoalcohols

The electron-transfer quenching of excited acceptors by amines and subsequent chemical reactions have been topics of extensive study. Among the various reactions of the photogenerated radical ion pairs, fragmentation via C-C bond cleavage has been shown to be prominent and often a chemically clean path for aminoalcohols, aminoketones, and other systems, recent experiments have shown that the dehydrofragmentation of aminoalcohols is strongly acceptor-dependent and consistent with a mechanism in which the acceptor anion radical acts as a base to promote cleavage of the donor cation radical in a reaction closely analogous to the two-electron Grob fragmentation. The authors report here studies of the photooxidative fragmentation of 1,2-ditertiary amines, a reaction which is probably also quite general and which shows both similarities and yet remarkable contrasts to the aminoalcohol cleavage.