Triphenylphosphine Catalyzed, One-Pot, Multicomponent Synthesis of Spirooxindoles

Multicomponent reaction involving isatin (1), malononitrile (2), and dimedone (3), in the presence of triphenylphosphine as an efficient catalyst in the eco-friendly solvent ethanol, results in the formation of spirooxindole derivatives 4 i.e 2-Amino-5-oxo-7,7-dimethyl spiro[(4H)-5,6,7,8-tetrahydrochromene-4,3-(3H)-indol]-(10H)-2-onecarbonitrile. The reaction proceeds smoothly under mild conditions and the products are obtained in good to excellent yields. This method is applicable to a variety of isatin derivatives.