Facile and Chemically Sustainable Catalyst-Free Synthesis of Diverse 2-Aryl-4-Alkyl/Aryl-Pyrano[3,2-c]chromen-5 (4H)-Ones by One-Pot Multicomponent Reactions at Room Temperature

A simple, catalyst-free, straightforward and highly efficient onepot synthesis of pharmaceutically-interesting diverse kind of functionalized 2-aryl-4-alkyl/aryl-pyrano[3,2-c] chromen-5(4H)-ones (4a-4z '') and 3-/4-(5-oxo-2-aryl-4,5-dihydropyrano[3,2-c] chromen-4-yl) benzaldehydes (4 ' a-4 ' j) has been developed based on a multicomponent reaction between alkyl/aryl aldehydes (1/1 '), acetophenones (2) and 4-hydroxycoumarin (3) in aqueous ethanol at room temperature (25-30 degrees C). The salient features of this protocol are mild reaction conditions, use of no catalyst, good to excellent yields, high atom-economy, eco-friendliness, easy isolation of products, and reusability of reaction media.