Convenient singlet oxygenation in multiphase microemulsion systems

Generation of singlet oxygen from fragmentation of monoactivated 1,1-dihydroperoxides

The first singlet excited state of molecular oxygen ((1)O(2)) is an important oxidant in chemistry, biology, and medicine. (1)O(2) is most often generated through photosensitized excitation of ground-state oxygen. (1)O(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 (1)O(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 ((1)O(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.

A new peroxide fragmentation: efficient chemical generation of (1O2) in organic media

Monoactivated derivatives of 1,1-dihydroperoxides undergo an unprecedented base-promoted fragmentation to efficiently generate singlet oxygen (1O2) in anhydrous organic solvents.

Copper- and ligand-free Sonogashira reaction catalyzed by palladium in microemulsion: Effects of surfactant and alcohol

A rapid copper- and ligand-free Sonogashira reaction was performed in an oil-in-water microemulsion. Palladium nanoparticles can be in situ formed in the microemulsion without other reductants. The microemulsion containing in situ-formed nano-Pd is an efficient system for the Sonogashira reaction. The reactions were faster in the microemulsion than in micelles. The effects of surfactant, alcohol, and temperature are discussed. Excellent yield of the Sonogashira reaction catalyzed by 0.5 mol% palladium could be achieved at 80 degrees C within 2 min.

Copper- and ligand-free Sonogashira reaction catalyzed by palladium in microemulsion

An oil-in-water microemulsion containing PdCl2 and NaOH can be used as an effective catalyst system for rapid copper- and ligand-free Sonogashira reaction of aryl halides and phenylacetylene. Excellent yield of the Sonogashira reaction catalyzed by 0.5 mol% palladium could be achieved within 5 min. The types of base have an intense influence on the reaction. The reaction rate was increased with increased aqueous content in the microemulsions, and dispersed palladium nanoparticles can be in situ formed without other reductants.