Simple and efficient protocol for the synthesis of novel dihydro-1H-pyrano[2,3-c]pyrazol-6-ones via a one-pot four-component reaction

Ba(OH)2 catalyzed simple and efficient one-pot four-component reaction of Meldrums acid, ethyl acetoacetate, hydrazine hydrate, and aromatic aldehydes to give 3-methyl-4-aryl-4,5-dihydro-1H-pyrano[2,3-c]pyrazol-6-ones in refluxing water is reported. The yields are high and the reactions go to completion in 1–2 h.