Eco-friendly polyethylene glycol (PEG-400): a green reaction medium for one-pot, four-component synthesis of novel asymmetrical bis-spirooxindole derivatives at room temperature.

PEG-400 has been used as a green and biodegradable polymeric solvent for the one-pot, two-step, multi-component synthesis of novel asymmetrical bis-spirooxindole derivatives by the reaction of -alkyl isatin, isatin derivatives, alkylmalonates and C-H activated carbonyl compounds in the presence of KCO at room temperature. Using this procedure, all the products were obtained in good to excellent yields.