Ionic Liquid in Cyclization Reaction
Cyclic frameworks, especially heterocycle skeleton, widely existing in organic compounds, natural products, and drugs, are of great importance in both academy and industry. Ionic liquids (ILs) have shown excellent characteristics compared with traditional organic solvents, in the construction of cyclic frameworks by cyclization reactions, e.g., Diels-Alder (DA) reaction, cyclopropanation, the synthesis of aziridines, Prins cyclization, and so on. IL species employed in the cyclization reaction mainly belong to ammonium cation-based ones, in which tetraalkylammonium, imidazolium, and pyridinium ions act as cations, while halide (X−), bis((trifluoromethyl)sulfonyl)imide (NTf2−), tetrafluoroborate (BF4−), hexafluorophosphate (PF6−), and bisulfate (HSO4−) usually serve as anions.
Basic Definitions About the Application of ILs in Cyclization Reaction
ILs, as an environmental-friendly alternative to traditional organic solvents, have attracted wide...
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