A Clean and One-Pot Synthesis of Spiroindoline-Pyranopyrazoles

Piperidine catalyzes efficiently the one-pot, four-component reaction of beta-ketoesters, hydrazine hydrate, malononitrile, and isatines in aqueous media. The reaction was done at room temperature and the spiro[indoline-3,4'-pyrano[2,3-c]pyrazole]-5'-carbonitriles were obtained with high yields and purity via an easy work-up procedure. These compounds were also investigated in vitro for antibacterial activities.