Friedel–Crafts acylation of indoles in acidic imidazolium chloroaluminate ionic liquid at room temperature

A practical and convenient protocol has been developed for the acidic 1-ethyl-3-methylimidazolium chloroaluminate ionic liquid (generated from 1-ethyl-3-methylimidazolium chloride (EmimCl) and aluminium chloride (X(AlCl3), mole fraction X=0.67–0.75) promoted Friedel–Crafts acylation of indoles at room temperature. The simple experimental procedure provides 3-substituted indoles in good to high yields with less electron rich indole ring systems.