ZrO2 nanoparticles as a reusable solid dual acid–base catalyst for facile one-pot synthesis of multi-functionalized spirooxindole derivatives under solvent free condition

A two-step one-pot protocol for the facile synthesis of biologically important spirooxindole derivatives such as spiro[4H-pyran-3,3′-oxindoles] and spiro[indoline-3,4′(1H′)-pyrano-[2,3-c]pyrazol-2-ones has been developed.