Well-confined polyoxometalate-ionic liquid in silicic framework for environmentally friendly asymmetric di-hydroxylation of olefins

Abstract

Chiral 1,2-diols with a high yield could be directly prepared from asymmetric di-hydroxylation of olefins via an eco-friendly and enduring catalyst, in which abundant "chiral pools" of polyoxometalate-ionic liquid were target-designed into the silicic framework (POM-ILS) and well stabilized in aqueous media. Fig. 1 FTIR, TG, SEM of POM-ILS(3/1) (a, b and c) and SEM of POM (d).This journal is

Polyoxometalate‐based Inorganic‐Organic Hybrids as Heterogeneous Catalysts for Asymmetric and Tandem Reactions

“…For catalysts containing the encapsulated POMs in ionic liquids and silicic frameworks, diol selectivity was enhanced and the enantiomeric excess of R/S isomers was obtained at 82-95 %. [68] Chirality transfer from chiral polyoxometalates to covalently attached achiral imidazolidinone was reported by Xuan et al Chiral Sn-substituted Dawson POM with formula (TBA) 6 [α 1 -P 2 W 17 O 61 {SnCH 2 CH 2 C(= O)}] (TBA = tetra-n-butylammonium) was synthesized and further functionalized by achiral amino ethyl imidazolidinone to generate POM-imidazolidinone hybrids (Fig-ure 9). The chiral hybrid was utilized for Diels-Alder reaction between crotonaldehyde and cyclopentadiene in CH 2 Cl 2 in the presence of 2,4-dinitrobenzoic acid.…”

“…Although the reaction conversion for styrene dihydroxylation was high in the presence of silica‐free POM‐IL, the catalyst was not selective towards the formation of diols and benzaldehyde was also formed as the main by‐product. For catalysts containing the encapsulated POMs in ionic liquids and silicic frameworks, diol selectivity was enhanced and the enantiomeric excess of R/S isomers was obtained at 82–95 % [68] …”

Polyoxometalates‐Based Ionic Liquids (POMs‐ILs) for Electrochemical Applications

“…combining [PW 12 O 40 ] 3− anion with a poly(ethylene glycol) (PEG)‐ containing quaternary ammonium cation that exhibited unusually high conductivity . Their potential has been explored in catalysis (namely in desulfurization, esterification, production of ketones, asymmetric di‐hydroxylation of olefins, in CO 2 conversion, in anti‐corrosion, antibacterial and antimicrobial coatings, and as photoluminescence materials . Concerning their electrochemical properties, POMs‐ILs have been prepared and studied as electrochromic materials for modification of carbon composite electrodes, for selective determination of ascorbic acid based on modified glassy carbon electrodes and towards the oxidation of the NADH coenzyme, for catalytic reduction of nitrite, bromate and hydrogen peroxide using a modified carbon paste electrodes, for electroluminescence as good electron‐ transport, as reversible phase transformation ionic‐liquid‐type gels, as new hybrid gel electrolytes, for the modification of polycrystalline gold electrode, as well as for high performance Li−S battery cathode …”