Catalytic activity of ZrO2–SO3H as highly efficient recyclable nano-catalyst for the synthesis of tetrahydrobenzo[b]pyrans

Application of Nano Zirconia Sulfuric Acid (n-ZrSA), as a catalyst for the synthesis of tetrahydrobenzo[b]pyran prepared by the reaction of dimedone, aromatic or aliphatic aldehydes, and malononitrile in solvent-free condition. The catalyst was prepared according to a previously published literature procedure using inexpensive and readily available starting materials. Furthermore, the catalyst could be recovered conveniently and reused efficiently such that a considerable catalytic activity still could be achieved after fourth run. Other beneficial features of this new synthetic approach include short reaction time, high yields, clean reaction profiles, and a simple work‐up procedure.