Sulfonated polyethylene glycol as a reusable and efficient catalytic system for the synthesis of diindolyl oxindole derivatives under ambient conditions

Sulfonated Polyethylene Glycol (PEG-OSO3H) as an efficient and reusable acidic catalyst was used for the preparation of 3,3-diheteroaromatic oxindole derivatives as an important class of potentially bioactive compounds from condensation reaction of indole and isatin derivatives under ambient conditions in good to excellent yields (65- 98%).