Enantioselective Epoxidation of Electron-Deficient Alkenes Catalyzed by Manganese Complexes with Chiral N4 Ligands Derived from Rigid Chiral Diamines

Article abstract of DOI:10.1002/adsc.201700541

A series of tetradentate sp²N/sp³N hybrid chiral N₄ ligands derived from rigid chiral diamines were synthesized, which enabled the first manganese-catalyzed enantioselective epoxidation of electron-deficient alkenes with hydrogen peroxide (H₂O₂) as an oxidant. The reaction furnishes enantiomerically pure epoxy amides, epoxy ketones as well as epoxy esters in good yields and excellent enantioselectivities (up to 99.9% ee) with lower catalyst loading. Preliminary studies on structure–activity relationship demonstrated that maintaining comparatively lower electron-donating ability of the sp³N and relatively higher electron-donating ability of sp²N of the N₄ ligands is beneficial to getting higher activity and selectivity, thus providing us a new view to understand epoxidation with H₂O₂. (Figure presented.).