A novel pyrrolidinium ionic liquid with 1,1,2,2-tetrafluoro-2-(1,1,2,2-tetrafluoroethoxy)ethanesulfonate anion as a recyclable reaction medium and efficient catalyst for Friedel–Crafts alkylations of indoles with nitroalkenes

A series of pyrrolidinium-based salts with new fluorine-containing anions were synthesized. Different melting points could be obtained by changing the length of the fluoroalkyl chain of the anions. The pyrrolidinium 1,1,2,2-tetrafluoro-2-(1,1,2,2-tetrafluoroethoxy)ethanesulfonate ([C4H8NH2][H(CF2)4O(CF2)2SO3]) is highly fluid even below room temperature. It can be used both as a recyclable solvent and as an efficient catalyst for Friedel–Crafts alkylations of indoles with nitroalkenes.

Graphical abstractA novel pyrrolidinium ionic liquid was used as both the recyclable solvent and catalyst for Friedel–Crafts alkylations of indoles with nitroalkenes.Figure optionsDownload full-size imageDownload as PowerPoint slide