4-Dimethylaminopyridine-catalyzed multi-component one-pot reactions for the convenient synthesis of spiro[indoline-3,4′-pyrano[2,3-c]pyrazole] derivatives

An efficient and clean reaction process was developed for the convenient and cheap synthesis of spirooxindole derivatives. One-pot reactions of isatins, malononitrile (or ethyl cyanoacetate), hydrazine hydrate (or phenylhydrazine), and 1,3-dicarbonyl compounds were compared with one-pot reactions of isatins, malononitrile (or ethyl cyanoacetate), and 5-pyrazolone derivatives. Both sets of reaction were conducted in EtOH in the presence of 4-DMAP catalyst. A series of spiroindoline-3,4′-pyrano2,3-c]pyrazole] derivatives were quickly obtained in excellent yields by using the four-component one-pot reaction method.