Tandem Knoevenagel–Michael-cyclocondensation reactions of malononitrile, various aldehydes and dimedone using acetic acid functionalized ionic liquid

Abstract

An efficient solvent-free protocol for the synthesis of tetrahydrobenzo[b]pyrans by the condensation of malononitrile, dimedone and various aldehydes in the presence of acetic acid functionalized imidazolium salts (1-carboxymethyl-3-methylimidazolium bromide {[cmmim]Br} and 1-carboxymethy1-3-methylimidazolium tetrafluoroborate {[cmmim][BF₄]}) as reusable catalysts has been reported. The turn over frequency (TOF) values of the catalysts are higher than some of the previously reported catalysts. Also, thermal gravimetric analysis (TGA), differential thermal gravimetry (DTG), X-ray diffraction analysis (XRD) and calculations of the size and inter-planer distance of the catalysts have been reported in this work.