Indium Trichloride Catalysed Domino Reactions of Isatin: A Facile Access to the Synthesis of Spiro(indoline-3,4′-pyrano[2,3-c]pyrazol)-2-one Derivatives

A versatile high-yielding indium trichloride mediated one-pot regioselective synthesis of spiroxindoles via domino one-pot, three-component reaction of isatins, pyrazoles, and ( E -)- N -methyl-1-(methylthio)-2-nitroethenamine is described. This reaction presumably occurs via domino Knoevenagel condensation–­Michael addition–intramolecular O-cyclization sequence. The salient features of the methodology are its clean reaction conditions, the eco-friendly medium, low cost, easy isolation, and excellent yields without column chromatographic purification.