An environmentally benign approach for the synthesis of 3,3′-pyrrolidonyl spirooxindole derivatives via a cascade Knoevenagel-Michael-cyclization multicomponent reaction

A series of 3,3 '-pyrrolidonyl spirooxindole derivatives have been synthesized in good yields from the cascade Knoevenagel-Michael-cyclization multicomponent reaction of isatin, malononitrile and a-isothiocyanato imide in the presence of a catalytic amount of triethylamine "on water" assisted with ultrasonic irradiation. The advantages of this method include high efficiency, mild reaction conditions and environmentally benign reagents. The current process provides a simple and green method for creating diversity-oriented syntheses of this intriguing class of compounds with potential biological activities.