Efficient and convenient epoxidation of alkenes to epoxides with H2O2 catalyzed by Co(OAc)2 in ionic liquid [C12py][PF6]

The influence of hydrogen bonding on the structure of organic-inorganic hybrid catalysts and its application in the solvent-free epoxidation of α-olefins

In this study, two types of catalysts were prepared by the combination of gemini quaternary ammonium salt with two distinct species of phosphotungstic acid. Catalysts prepared by the Wells-Dawson type of phosphotungstic acid and Keggin-type phosphotungstic acid both exhibited dual-phase catalytic behavior, demonstrating both heterogeneous and homogeneous catalytic activities. In comparison to the catalyst prepared by the Keggin-type phosphotungstic acid, due to the higher size of Wells-Dawson type of phosphotungstic acid, hydrogen bonding could not effectively affect the catalyst prepared by H6P2W18O62. Subsequently, the influential factors on the catalytic reaction were investigated. Through the utilization of techniques such as XPS, FT-IR, Raman spectra and other characterization methods, two distinct structure and reaction mechanisms for these catalysts were elucidated under the influence of hydrogen bonding.

Applications of Liquid/Liquid Biphasic Oxidations by Hydrogen Peroxide with Ionic Liquids or Deep Eutectic Solvents

This Minireview focuses on recent applications of ionic liquids (ILs) and deep eutectic solvents (DESs) in biphasic oxidations in which the oxidizing agent corresponds to hydrogen peroxide. Biphasic reactions are accomplished when the substrate presents low or moderate solubility in aqueous (polar) systems and/or when separation of products and byproduct is an issue. The properties of the IL and DES allows the reaction activity to be intensified. On the other hand, the high chemical stability of the ionic solvents allows the use of hydrogen peroxide to minimize solvent degradation and unwanted byproducts. The experimental evidence presented herein shows that ILs and DESs can be used as cocatalysts, catalysts, and solvents to achieve enhanced yields and conversions. The process advantages, in terms of a reduction of volatile solvents, improve the safety and use of the oxidizing agent, which implies the possibility of developing new process improvements in the future.