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 N-alkyl isatin, isatin derivatives, alkylmalonates and C–H activated carbonyl compounds in the presence of K2CO3 at room temperature. Using this procedure, all the products were obtained in good to excellent yields.