Green and Sustainable Catalysis for Efficient Synthesis of Spirooxindoles Using Deep Eutectic Solvent

Deep eutectic solvents play a significant role in minimizing the ecological effect of chemical processes associated with the use of any environmentally unsafe expensive catalysts, solvents and bases. An eco‐efficient and economical one‐pot synthesis of Spirooxindole derivatives from isatin derivatives, activated methylene compounds and β‐ketoesters/acyclic 1,3‐diketones is described using a formulated deep eutectic solvent (DES) comprising urea and choline chloride in a 2:1 molar ratio as catalyst. As a catalyst deep eutectic solvents shows good compatibility with various substrates, easy removal, easy handling, operational simplicity and work in mild reaction conditions. This protocol appealing features includes chromatography‐free purification process and high atom economy. The DES as catalyst made from urea and choline chloride, is safe, non‐volatile, non‐toxic, biodegradable, and cost‐effective. The DES was recycled for four consecutive cycles without any significant loss in activity.