Microwave accelerated preparation of [bmim][HSO4] ionic liquid: an acid catalyst for improved synthesis of coumarins

A efficient and easy method for preparation of (1-butyl-3-methyl-imidazolium hydrogen sulphate) ionic liquid using sodium bisulphate in place of concentrated sulphuric acid by microwave irradiation had been developed by us with manifold reduction in time. Further, this acidic room temperature ionic liquid has been exploited for the synthesis of coumarins under microwave irradiation and solventless conditions in short duration of time with quantitative yields, for the first time.