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• Three novel highly active phthalimide based ionic liquids are synthesized. • 98.7 % yield is achieved under the atmospheric CO 2 pressure and 30 °C. • Contributions of each active components are analyzed by DFT calculations. • Inert cation and moderate basicity of ionic liquid are crucial items. The carboxylative coupling of carbon dioxide (CO 2) with propargyl alcohols is an important pathway to accomplish the reusability of CO 2. Moreover, the α-methylene cyclic carbonates are the critical intermediate to generate the fine chemicals and pharmaceuticals. However, the robust catalyst is still limited to perform this reaction under the mild conditions, especially to obtain the equilibrium among several reaction conditions including reaction time, reaction temperature, and catalyst amount. The novel ionic liquid, [Pth][BTMA], is synthesized in this work to be catalyst for the title reaction along with AgOAc as the co-catalyst. To explore the influence of cation, anion, and Ag salt, other four ionic liquids are utilized to catalyze the reaction along with five different Ag salts. Under the atmospheric pressure and 30 °C, the 98.7 % product yield is achieved by [Pth][BTMA]/AgOAc within 9 h, which are better than most of catalysts in literature. More important, the role of cation and anion in the catalysis is elucidated by the 1H NMR, 13C NMR, and density functional theory (DFT) calculations. Both the moderate basicity and inert cation of [Pth][BTMA] contribute the excellent catalytic activity. [Display omitted] [ABSTRACT FROM AUTHOR]

• The mechanism of title reaction catalyzed by AgNO 3 /[C 2 C 1 mim][OAc] is elucidated. • The contributions of anions and cations are discussed in detail. • The differences between different catalysts are discussed in depth. The chemical fixation of CO 2 has attracted elevated attentions since it is a promising pathway to solve the serious environmental pollution and fuel shortage. The three-component reaction of CO 2 , propargyl alcohols, and 2-aminoethanols is one of the most attractive candidates due to the wide applications and extreme importance of products. However, the reaction mechanism is desired to explore due to the complicated catalytic components and substrates. In addition, contribution of each catalytic component and actual catalytic component are still not clear. The mechanism of title reaction catalyzed by AgNO 3 /[C 2 C 1 mim][OAc] is elucidated by the density functional theory (DFT). In addition, the catalytic routes of AgNO 3 /[C 4 C 1 mim][OAc], AgNO 3 /[DBUH][OAc], AgNO 3 /[C 2 C 1 mim][NO 3 ], and AgNO 3 /[C 2 C 1 mim][ClO 4 ] are also considered to unfold the contribution of cation and anion. The atoms in molecule (AIM) and noncovalent interactions (NCI) are calculated for some important configurations to deeply understand the difference among various catalysts. To elucidate these issues is favorable to explore the more robust catalysts for this reaction. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • The catalyzed mechanism of propargylic alcohol and H 2 O is investigated. • CO 2 could be absorbed by the [Bu 4 P+] cation to form [Bu 4 P -H -CO 2 ] complex. • A novel mechanism is proposed with the [Bu 4 P -H -CO 2 ][Im +H ] complex employed as the actual catalytic species. Hydration of propargylic alcohols is one of the most important pathways to synthesize α-hydroxy ketones. However, its mechanism is still obscure in the presence of multiple catalytic species. The mechanism of catalysis for the hydration of propargylic alcohols in the presence of [Bu 4 P+][Im-] is investigated along with the carbon dioxide (CO 2) as the co-catalyst by the density functional theory (DFT) with the aim to elucidate the role of [Bu 4 P+] cation and [Im-] anion. The CO 2 could be absorbed by the [Bu 4 P+] cation to form [Bu 4 P -H -CO 2 ] complex after the hydrogen atom in [Bu 4 P+] cation transfers to the [Im-] anion. Then, both [Bu 4 P -H -CO 2 ] and [Im +H ] are employed as the actual catalytic species to construct a new pathway. It is the more favorable as compared with the previously reported pathways. In previous reported pathway, the [Im-] anion is regarded as the real catalytic species, while [Bu 4 P+] cation plays the auxiliary role to stabilize the substrate by the hydrogen bond. The mechanism of the same reaction catalyzed by other four different ionic liquids is also investigated to further testify the contribution of [Bu 4 P+] cation and [Im-] anion in the catalysis. This work not only provides a new insight into the cation-regulated pathway for the hydration of propargylic alcohols but also points out a new strategy to design the ionic liquids achieving the improved catalytic efficiency. [ABSTRACT FROM AUTHOR]