Generation of Singlet Oxygen from Fragmentation of Monoactivated 1,1-Dihydroperoxides

The first singlet excited state of molecular oxygen (O-1(2)) is an important oxidant in chemistry, biology, and medicine. O-1(2) is most often generated through photosensitized excitation of ground-state oxygen. O-1(2) can also be generated chemically through the decomposition of hydrogen peroxide and other peroxides. However, most of these dark oxygenations require water-rich media associated with short O-1(2) lifetimes, and there is a need for oxygenations able to be conducted in organic solvents. We now report that monoactivated derivatives of 1,1-dihydroperoxides undergo a previously unobserved fragmentation to generate high yields of singlet molecular oxygen (O-1(2)). The fragmentations, which can be conducted in a variety of organic solvents, require a geminal relationship between a peroxyanion and a peroxide activated toward heterolytic cleavage. The reaction is general for a range of skeletal frameworks and activating groups and, via in situ activation, can be applied directly to 1,1-dihydroperoxides. Our investigation suggests the fragmentation involves rate-limiting formation of a peroxyanion that decomposes via a Grob-like process.