Binshen Wang

Are Ionic Liquids Chemically Stable

Ionic liquids have attracted a great deal of interest in recent years, illustrated by their applications in a variety of areas involved with chemistry, physics, biology, and engineering. Usually, the stabilities of ionic liquids are highlighted as one of their outstanding advantages. However, are ionic liquids really stable in all cases? This review covers the chemical stabilities of ionic liquids. It focuses on the reactivity of the most popular imidazolium ionic liquids at structural positions, including C2 position, N1 and N3 positions, and C4 and C5 positions, and decomposition on the imidazolium ring. Additionally, we discuss decomposition of quaternary ammonium and phosphonium ionic liquids and hydrolysis and nucleophilic reactions of anions of ionic liquids. The review aims to arouse caution on potential decomposition of ionic liquids and provides a guide for better utilization of ionic liquids.

One-Pot Conversion of Carbon Dioxide, Ethylene Oxide, and Amines to 3-Aryl-2-oxazolidinones Catalyzed with Binary Ionic Liquids

An effective one‐pot method for the conversion of carbon dioxide, ethylene oxide, and amines to 3‐aryl‐2‐oxazolidinones has been developed. This one‐pot method consists of two parallel reactions and a subsequent cascade reaction between the two products of the corresponding parallel reactions. Notably, the binary ionic liquids of 1‐butyl‐3‐methyl‐imidazolium bromide and 1‐butyl‐3‐methyl‐imidazolium acetate demonstrate a synergistic catalytic effect on this new strategy. 1‐Butyl‐3‐methyl‐imidazolium bromide is essential in two parallel reactions owing to the good nucleophilicity and leaving ability of bromide, and 1‐butyl‐3‐methyl‐imidazolium acetate plays a dominant role in the subsequent cascade reaction owing to the strong basicity of acetate. In addition, the binary ionic liquids can be used thrice without significant loss of catalytic activity.

DBU and DBU-Derived Ionic Liquid Synergistic Catalysts for the Conversion of Carbon Dioxide/Carbon Disulfide to 3-Aryl-2-oxazolidinones/[1,3]Dithiolan-2-ylidenephenyl- amine†

An intermolecular synergistic catalytic combination of 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) and a DBU‐derived bromide ionic liquid has been developed for the conversion of CO2, epoxides, and amines under metal‐ and solvent‐free conditions. Various 3‐aryl‐2‐oxazolidinones are produced in moderate to excellent yields within a short reaction time. NMR spectroscopy and DFT calculations demonstrate that DBU as a hydrogen bond acceptor and the ionic liquid as a hydrogen bond donor activate the substrates cooperatively by inducing hydrogen bonds to promote the reaction effectively. Based on these results, a possible reaction mechanism on the synergistic catalysis of DBU and the ionic liquid is proposed. In addition, the reaction of CS2, ethylene oxide, and aniline catalyzed by the combination of DBU and the DBU‐derived ionic liquid also proceeds smoothly, which opens a hitherto unreported route to [1,3]dithiolan‐2‐ylidenephenylamine in a straightforward way.

Pyrene-appended, benzimidazoliums-urea-based ratiometric fluorescent chemosensor for highly selective detecting of H2PO4−

A novel flexible pyrene-based chemosensor 1 bearing two benzimidazolium moieties and a urea group was designed and synthesized. The binding properties of chemosensor 1 toward various anions were examined via UV-vis, fluorescence, and 1H NMR spectroscopic methods. The results demonstrated that chemosensor 1 could distinguish H2PO4− from other tested anions such as F−, Cl−, Br−, I−, AcO− and HSO4− by ratiometric fluorescence as chemosensor 1 formed a complex with H2PO4− in 2 : 2 ratio via intermolecular excimer transduction in CH3CN. The fluorescence response of chemosensor 1 to H2PO4− was hardly interfered by other anions. The detection limit of chemosensor 1 (5 × 10−6 M) toward H2PO4− is 5.02 × 10−7 M.

Hydroxyalkylation of indole with cyclic carbonates catalyzed by ionic liquids

A simple and eco-friendly procedure has been developed for the synthesis of hydroxyalkyl indoles from indole and cyclic carbonates in the presence of a catalytic amount of imidazolium based ionic liquids under solvent-free conditions. The effects of reaction time, the catalyst amount, temperature, and the ratio of the reactants were investigated to develop the optimum conditions for the transformation. Under the optimized reaction conditions, indole reacted with ethylene carbonate or propylene carbonate to give 1-(2-hydroxyethyl)indole or 1-(2-hydroxypropyl)indole, as well as the corresponding sequential derivatives, in high yields. The catalytic activity of the ionic liquids was affected by the anions of the ionic liquids in the order of BF4− < Br− < Cl− < OAc−, which was consistent with the hydrogen bond basicity of the anions of the ionic liquids.

Application of Organic Carbonates in Organic Transformation Catalyzed by Ionic Liquids

Organic carbonates are renowned for their low toxicity and high biodegradability, which is considered as green reagents and an appropriate alternative to conventional toxic compounds. Additionally, organic carbonates can be produced from CO2; therefore, the transformation of organic carbonates to other valuable chemicals is an indirect way for CO2 utilization. The transformation reactions of organic carbonates mainly include alkylation reactions, carbonylation reactions, and transesterification reactions. Ionic liquids, as attractive media, have already exhibited excellent performance on promoting various transformations of organic carbonates. This chapter covers recent applications of organic carbonates in organic transformation reactions catalyzed by ionic liquids.