Super Base Derived Ionic Liquids: A Useful Tool in Organic Synthesis

Abstract: Over the last few decades, ionic liquids have been raised as a great appliance to pursue many organic transformations. In the present research, the synthetic application of ILs has emerged largely as solvents, additives, or catalysts. With the developing commercial methods, task-specific ionic liquids have been constructed by appointing guanidine, amidine and other superbasic cations. By the nature of the cation or the anion, the properties of the ionic liquids can be adjusted. In this regard, superbasic ionic liquids have been derived from both acyclic and cyclic guanidine or amidine derivatives. In particular, some common super bases such as 1,1,3,3-tetramethylguanidine (TMG), 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,5-diazabicyclo[4.3.0]non-5-ene (DBN), are used to design these special type of ionic liquids. These superbasic ionic liquids have shown a potential activity to accelerate many organic transformations including alcoholysis, esterification, multi-component reaction, Knoevenagel reaction, Michael addition, cyclization, etc. Additionally, because of their novel properties including high liquid range, nonvolatility, high thermal and chemical stability, these classic ionic liquids have a potential environmental impact and they are often found to play a promising role in the field of catalysis, electrochemistry, spectroscopy, and materials science. Not only that, the application of superionic liquids has been widely spread in the industrial and research area, especially, for the chemical transformation of CO2. This review aims to portray an outlook on the organic syntheses that have been promoted by superionic liquids in the last five years.