Potassium phthalimide: an efficient and simple organocatalyst for the one-pot synthesis of dihydropyrano[3,2-c]chromenes in aqueous media

A series of dihydropyrano[3,2-c]chromene derivatives were obtained via treating cyano methylene compounds (malononitrile or ethyl cyanoacetate), aromatic aldehydes, and 4-hydroxycoumarin in the presence of potassium phthalimide, as a green, mild, efficient, and commercially available organocatalyst in aqueous media. This procedure was easily performed, which provides a straightforward route for the synthesis of diverse dihydropyrano[3,2-c]chromene compounds. Safety, short reaction times, environmentally friendly, no use of hazardous organic solvents, and high yields are remarkable advantages of this process.