A summary of ultrasound-assisted pyrano[2,3-c]pyrazole and spiropyrano[2,3-c] pyrazole synthesis.

Product	Reactants	Catalyst	Solvent	Method employed	Reaction time	Yield	Ref.
Dihydropyrano[2,3-c]pyrazoles	Four-component system: 4-hydrazinobenzoic acid, β-keto esters, aromatic aldehydes, and malononitrile	Ceric ammonium nitrate (CAN)	Water	Ultrasound	45–60 min	70–90%	Ablajan et al.44
Spiro[indoline-3,4′-pyrano[2,3-c]]pyrazoles	Three-component system: isatin, ethyl-cyanoacetate, and 3-methyl-1-phenyl-2-pyrazolin-5-one	ZnS nanoparticles	Water	Ultrasound	12–15 min	93–97%	Dandia et al.45
Pyrano[2,3-c]pyrazoles	Four-component system: aromatic aldehydes, hydrazine monohydrate, ethyl acetoacetate, and malononitrile	Catalyst free	Water	Ultrasound	30–90 s	90–97%	Shabalala et al.46
Pyrano[2,3-c]pyrazole-3-carboxylate and pyrano[2,3-c]pyrazole-5-carbonitriles	Four-component system: dimethylacetylenedicarboxylate/ethyl acetoacetate, hydrazine hydrate, malononitrile, and aromatic aldehyde	Mn/ZrO2	Aq. ethanol	Ultrasound	10 min	88–99%	Maddila et al.47