Sulfuric acid-modified poly(ethylene glycol): an efficient, biodegradable, and reusable polymeric catalyst for synthesis of spiro oxindole derivatives in aqueous medium

Abstract

A versatile, novel, and environmentally benign strategy has been successfully developed for synthesis of oxindoles, an important class of potentially bioactive compounds. Sulfonated poly(ethylene glycol) was used as inexpensive and recyclable acidic catalyst. The products were obtained in water, an excellent solvent in terms of environmental impact, in high yield, by one-pot reaction of malononitrile, 1,3-dicarbonylcoumarin or 4-hydroxycoumarin derivatives, and isatins. This new method totally avoids the use of organic acids and toxic or expensive solvents.