New ternary immobilization of chiral sulfonato-(salen)manganese(III) complex for aqueous asymmetric oxidation reactions

Abstract This article reports our study on asymmetric epoxidation of unfunctionalized alkenes and asymmetric oxidation of sulfides catalyzed by a new triply immobilized (salen)Mn(III) system, when commercial sodium hypochlorite and hydrogen peroxide were loaded as terminal oxidant, respectively. A chiral sulfonato-(salen)Mn(III) complex was grafted onto a novel polysiloxane, then axially coordinated by 3-aminopropyl functionalized silica gel (40–63 μm, 1 mmol g −1 NH 2 loading) as a secondary anchoring mode, and eventually dispersed into ionic liquid BMImX (BMIm +  = 1- n -butyl-3-methylimidazolium; X −  = PF 6 − , BF 4 − , NO 3 − ) for purpose of catalyst recycling. Catalysts were fully characterized by 1 H NMR, FT-IR, molar conductivity, elemental analysis, nitrogen adsorption, aqueous particle size and zeta potential analysis, along with XRD. Interestingly, lateral immobilization led to a novel catalyst structure featuring parallel stacking of one-dimensional planers, whereas the lateral together with axial immobilization made supported complex nano-sized crystallite particles (diameter 24.2 nm). After stepwise screening, doubly-immobilized catalyst and BMImBF 4 , in combination, showed best enantiomeric excess (e.e.) values and most stable recycling behavior in two kinds of catalysis, but generally sulfoxidation had better turnover frequencies than epoxidation reaction.