A cost-effective and green aqueous synthesis of 3-substituted coumarins catalyzed by potassium phthalimide

Abstract

An efficient procedure for the synthesis of various 2-imino-2H-chromene-3-carbonitriles, 2-oxo- 2H-chromene-3-carbonitriles as well as 2-oxo-2H-chromene-3-carboxylic acids is reported. It has been found that potassium phthalimide (PPI) catalyse the Knoevenagel condensation reaction of salicylaldehydes and activated β- dicarbonyl compounds efficiently under aqueous conditions at room temperature. This approach provides many merits such as high yields of products, clean, simple work-up, waste free, mild reaction conditions, commercially available organocatalyst, and the use of water as environmentally benign solvent.