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 ([C 4 H 8 NH 2 ][H(CF 2 ) 4 O(CF 2 ) 2 SO 3 ]) 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.