Anion–Cation Cooperative Catalysis by Ionic Liquids

Abstract

The cooperative effects of cation–anion are elucidated in ionic liquid‐catalyzed reactions of aniline with ethylene carbonate and the reaction of phenylacetonitrile with dimethyl carbonate. Cations of ionic liquids activate electrophiles by the proton in the 2‐position of the imidazolium ring through the hydrogen‐bond interaction with the carbonyl group. The catalytic activity follows the order of 1‐butyl‐3‐methyl‐imidazolium ([Bmim])>1,2‐dimethyl‐3‐butyl imidazolium ([Bmmim])>1‐butyl‐pyridinium ([Bpy]), which is consistent with the order of the hydrogen bond donor ability. Simultaneously, anions of ionic liquids activate nucleophiles by accepting the hydrogen bond. The catalytic activity of imidazolium‐based ionic liquids follows the order Cl>Br>BF4>PF6>C(CN)2COOEt≈NTf2>BPh4, which is consistent with the order of the hydrogen bond acceptor ability. The dual activation of nucleophiles and electrophiles by the cations and anions of ionic liquids is crucial to promote the reaction in high yields.

Sustainable conversion of carbon dioxide: the advent of organocatalysis

“…Gao's group recently reported 122,123 an alternative strategy for the selective preparation of 3-substituted cyclic carbamates from the reaction between a cyclic carbonate (made using CO 2 ) and aromatic amines using 1-butyl-3-methylimidazolium acetate (BmimOAc) as catalyst (Scheme 14). DFT calculations revealed that both the cationic and the anionic moieties of the catalyst activate in a cooperative fashion the substrates (i.e., cyclic carbonates and aromatic amines) by means of hydrogen-bonding.…”

Divergent Multistep Continuous Synthetic Transformations of Allylic Alcohol Enabled by Catalysts Immobilized in Ionic Liquid Phases.

“…Task‐specific supported IL‐like phases modified with sulfonic groups ( 9 a , Figure ) can be used to complex lanthanide triflates, in particular scandium triflate [Sc(OTf) 3 ] . In this regard, the presence of the imidazolium fragments in 9 a can contribute to the improvement of the catalytic activity provided by the Lewis‐acid units . Such contribution is absent in the analogous Sc‐supported catalyst 9 b , prepared from a commercially available sulfonic polystyrene‐divinylbenzene polymer (Amberlyst 15) …”

A heteropolyacid-based ionic liquid immobilized onto Fe3O4/SiO2/Salen/Mn as an environmentally friendly catalyst for synthesis of cyclic carbonate

“…The conversion of CO 2 to cyclic carbonates via epoxide substrates is a 100 % atom economic reaction, and the products are of wide applicability as electrolytes of Li ion batteries, aprotic solvents, degreasing agents, monomers for polymer synthesis, etc. [26][27][28][29].…”