Chiral metal-containing ionic liquid: Synthesis and applications in the enantioselective cycloaddition of carbon dioxide to epoxides

Abstract

A series of novel chiral metal-containing ionic liquids (CMILs) consisting of the cation of crown ether-chelated potassium/ sodium and the anion of chiral amino acids were designed and synthesized. These new CMILs were used to catalyze the enantioselective cycloaddition of epoxides and carbon dioxide incorporating with the salenCo(OOCCCl 3 ) to generate corresponding chiral cyclic carbonates under mild conditions. These new catalysts can be recycled at least five times without significant loss of activity and enantioselectivity. chiral metal-containing ionic liquids, epoxides, carbon dioxide, enantioselective cycloaddition, chiral cyclic carbonates

Insight into the activity of efficient acid–base bifunctional catalysts for the coupling reaction of CO2

“…So lots of attentions have been paid on this reaction due to its high atom utilisation, cheap, and low generation of by-product [7,8]. Numerous catalysts have been proposed for incorporating CO 2 into cyclic carbonates including alkali metal salts [9,10], metal oxides [11,12], ionic liquids (ILs) [13][14][15][16], and others [17][18][19][20][21]. Although significant advances have been made, the harsh reaction condition, water sensitivity, and the requirement of organic solvent are still the disadvantages those are necessary to be surmounted.…”

Chiral Catalysts for the Enantioselective Carbon Dioxide-Based Cyclic Carbonates and Polycarbonates

“…In this sense, a metal complex containing a chiral ligand, i.e., N,N′-bis(salicyclidene) cyclohexene diaminatecobalt, and an ionic liquid-like imidazolium salt (in a 0.1 %mol with respect to the epoxide substrate) was used, which was the catalyst 5 (see Figure 4) with acetate anion-the more active one (50% yield, TON = TOF = 74 h −1 )-while the catalyst 5 with tosylate anion was the most enantioselective one (40% e.e. to the R,R-cyclic [49]. The CO 2 cycloaddition to propylene oxide can be performed during 5 cycles using the same catalyst without significant activity or enantioselectivity decrease after the recycle of the catalyst via re-oxidization under an oxygen atmosphere and the addition of CH 2 Cl 2 + CCl 3 COOH upon the distillation of the product (see entry 3 in Table 1).…”

“…Thedesigned and synthesized salenCo(OOCCCl 3 )/[18-C-6K][L-Val]•0.5H 2 O gave the highest e.e. value of (S)-propylene carbonate (53.8%), with a 44% yield of carbonate using 0.1 %mol of salenCo(OOCCCl 3 ) catalyst (R,R)-2 and [18-C-6K][L-Val]•0.5H 2 O co-catalyst at 25 • C and under 6 bar of CO 2[49]. The CO 2 cycloaddition to propylene oxide can be performed during 5 cycles using the same catalyst without significant activity or enantioselectivity decrease after the recycle of the catalyst via re-oxidization under an oxygen atmosphere and the addition of CH 2 Cl 2 + CCl 3 COOH upon the distillation of the product (see entry 3 in Table1).Another example of metal-salen catalysts employing chiral ionic liquid-modified amino acids is the salen-Co(OAc) catalyst (R,R)-2.…”

Synthesis of Chiral Cyclic Carbonates via Kinetic Resolution of Racemic Epoxides and Carbon Dioxide

“…The utility of the catalyst system containing cobalt(III) complex 7 was demonstrated for the conversion of other epoxides such as butylene oxide into its corresponding chiral cyclic carbonate with a s value of 31.5 and 88.5% ee. Since the initial report, a number of modifications to the cobalt(III) salen catalyst system have been reported, all of which demonstrated some degrees of success [13][14][15][16][17][18][19][20][21][22]. Jing and co-workers reported a chiral polymer based on BINOL cobalt(III) salen complex 6 for the asymmetric addition of carbon dioxide to racemic propylene oxide 2a [23].…”