Eco-friendly, One-Pot Multicomponent Synthesis of Pyran Annulated Heterocyclic Scaffolds at Room Temperature Using Ammonium or Sodium Formate as Non-toxic Catalyst

A simple, facile, and convenient practical method for one-pot synthesis of pharmaceutically interesting diverse kind of pyran annulated heterocycles such as 4H-pyrano[3,2-c]coumarins, 4H-pyrano[3,2-c]--pyrones, 5,6,7,8-tetrahydro-5-oxo-4H-chromenes and benzo[h]-4H-chromenes in the presence of ammonium or sodium formate as catalyst via three-component condensation reaction of aromatic aldehydes, malononitrile, and C-H activated acidic compounds in aqueous ethanol has been developed mostly at room temperature. The salient features of the present method are mild reaction conditions, good to excellent yields, high atom economy, environmentally benign, easy isolation of products, no column chromatographic separation and reusability of reaction media.