Bronsted acidic ionic liquid as a recyclable catalyst for the one pot four-component synthesis of substituted pyrano[2,3-c]pyrazoles

An efficient, mild and environmentally friendly method was reported for the synthesis of pyranopyrazoles from aryl aldehydes, ethyl acetoacetate, malononitrile and hydrazine hydrate in the presence of catalytic amounts of methyl imidazolium hydrogen sulfate ([Hmim][HSO4]) as an efficient catalyst. These syntheses were performed via a one-pot four-component condensation in water/ethanol (50%) at 50 ?C. This method easily provides the coresponding products in good yield and relatively short reaction times. Also the reusability of the catalyst was investigated, the catalyst could be employed four times, although its activity gradually decreased.