Swift and Green Protocol for One-pot Synthesis of Pyrano[2,3- c]pyrazole-3-carboxylates With RuCaHAp as Catalyst

An efficient, atom-economical, four-component one-pot reaction method was developed for pyrano[2,3-c]pyrazole-3-carboxylates using dimethylacetylenedicarboxylate, hydrazine hydrate, malononitrile and aromatic aldehydes, using a RuCaHAp catalyst. Ten new substituted pyrano[2,3-c]pyrazole-3-carboxylate derivatives (5a-k) were synthesized in good to excellent yields (88 to 97%), at room temperature with short reaction times (≈ 30 min) using the green solvent aqueous ethanol. RuCaHAp was prepared and characterized by various techniques including SEM, TEM, P-XRD and BET spectroscopy. The proposed heterogeneous catalyst that can be easily synthesized, is inexpensive and stable with good reusability (at least 6 times) showing marginal loss of activity. The suggested environmentally benign protocol offers high yields, clean reaction profiles, operational simplicity and no need for chromatographic separations.