Dienamine-Catalyzed Nitrone Formation via Redox Reaction

The first catalytic method to directly introduce nitrone functionality onto aldehyde substrates is described. This reaction proceeds by an unprecedented organocatalytic redox mechanism in which an enal is oxidized to the gamma-nitrone via dienamine catalysis, thereby reducing an equivalent of nitrosobenzene. This reaction is a unique example of divergent reactivity of an enal, which represents a novel strategy for rapidly accessing small libraries of N,O-heterocycles. Alternatively, divergent reactivity can be suppressed simply by changing solvents.