Introduction of bis-imidazolium dihydrogen phosphate as a new green acidic ionic liquid catalyst in the synthesis of arylidene malononitrile, ethyl (E)-3-(aryl)-2-cyanoacrylate and tetrahydrobenzo[b]pyran derivatives

Abstract

In this work, [H2-Bisim][H2PO4]2 as a novel bis-imidazole-based acidic ionic liquid has been synthesized and characterized with a variety of techniques including FT-IR, 1H, 13C, 31P NMR and mass spectroscopy techniques. After characterization, this compound was used as an affordable and recyclable catalyst in the synthesis of arylidene malononitrile, ethyl (E)-3-(aryl)-2-cyanoacrylate and tetrahydrobenzo[b]pyran derivatives. The procedure had several advantages such as excellent yields, short reaction times, simple workup and use of a non-expensive and non-toxic compound as the catalyst. Moreover, the prepared ionic liquid could be recycled and reused without significant loss in its catalytic activity in the studied reactions.