Department of Sustainable Chemistry and Technology, SynBioC Research Group, Ghent University, Coupure Links 653, 9000 Ghent, Belgium.
Chemphyschem. 2012 Sep 17;13(13):3146-57. doi: 10.1002/cphc.201200343. Epub 2012 Jun 22.
A versatile and efficient method to synthesize tetrasubstituted imidazoles via a one-pot modified Debus-Radziszewski reaction and their subsequent transformation into the corresponding imidazolium ionic liquids is reported. The tetrasubstituted imidazoles were also synthesized by means of a continuous flow process. This straightforward synthetic procedure allows for a fast and selective synthesis of tetrasubstituted imidazoles on a large scale. The completely substituted imidazolium dicyanamide and bis(trifluoromethylsulfonyl)imide salts were obtained via a metathesis reaction of the imidazolium iodide salts. The melting points and viscosities are of the same order of magnitude as for their non-substituted analogues. In addition to the superior chemical stability of these novel ionic liquids, which allows them to be applied in strong alkaline media, the improved thermal and electrochemical stabilities of these compounds compared with conventional imidazolium ionic liquids is also demonstrated by thermogravimetrical analysis (TGA) and cyclic voltammetry (CV). Although increased substitution of the ionic liquids does not further increase thermal stability, a definite increase in cathodic stability is observable.
本文报道了一种通过一锅法改进的 Debus-Radziszewski 反应高效合成四取代咪唑的方法，以及随后将其转化为相应的咪唑鎓离子液体的方法。通过连续流工艺也可以合成四取代咪唑。这种直接的合成方法允许在大规模上快速和选择性地合成四取代咪唑。通过碘代咪唑盐的复分解反应可以得到完全取代的咪唑二氰胺和双（三氟甲烷磺酰基）亚胺盐。其熔点和粘度与非取代类似物处于同一数量级。除了这些新型离子液体具有优越的化学稳定性，可在强碱性介质中使用之外，通过热重分析（TGA）和循环伏安法（CV）还证明了这些化合物与传统的咪唑鎓离子液体相比具有更好的热稳定性和电化学稳定性。尽管离子液体的取代度增加不会进一步提高热稳定性，但可以观察到阴极稳定性的明显提高。
