Chiral ionic liquids improved the asymmetric cycloaddition of CO2 to epoxides

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

“…When the catalyst system was switched from (R,R)-1 to (S,S)-1, the enantioselectvity was decreased (entries 1, 2, 5, 6). The significant synergistic effects between chiral catalysts and cocatalysts were revealed: the cocatalyst with R,R chirality increased the ee values of (S)-PC catalyzed by (R,R)-1 and it decreased the ee values of (R)-PC catalyzed by (S,S)-1, which are consistent with our previous report [22]. Higher yields could be obtained when the reaction times were increased (entries 1,8,10,14,15,18).…”

“…Higher yields could be obtained when the reaction times were increased (entries 1,8,10,14,15,18). It is worth noting that when chiral MIL of [18-C-6K][L-Val]·0.5H 2 O was used alone as catalyst, the reaction could also induce the chiral PC with 5.4% ee (entry 4) which is higher than that of 1% ee obtained by chiral IL [22].…”

“…Even though some ionic liquids have been used as catalysts in the coupling of CO 2 and epoxides [17][18][19][20][21], chiral ionic liquids (CIL) used in enantioselective cycloaddition reactions was only reported once by our group [22]. Due to the fact that few literatures reported enantiomerically pure cyclic carbonates [22][23][24][25][26][27][28][29][30][31], new methodologies for the enantioselective cycloaddition of CO 2 to epoxides are still desired in terms of the atom economy and environmentally benign characteristics of this reaction.…”

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].…”

Recent developments of task-specific ionic liquids in organic synthesis

“…The synergistic effect between catalyst and IL was studied. The system was found to exhibit good activity for the asymmetric cycloaddition of carbon dioxide to epoxide under very mild conditions (Scheme 25) (59).…”