Ultrasound-assisted and trisodium citrate dihydrate-catalyzed green protocol for efficient and one-pot synthesis of substituted chromeno [3′,4′:5,6]pyrano[2,3-d]pyrimidines at ambient conditions

A simple, straightforward, and highly efficient multicomponent one-pot synthesis of a series of pharmaceutically interesting functionalized chromeno[3',4':5,6]pyrano[2,3-d]pyrimidines has been developed based on a low-cost and environmentally benign trisodium citrate dihydrate catalyst via ultrasound-assisted tandem reactions of 4-hydroxycoumarin, aromatic aldehydes, and barbituric acid/thiobarbituric acid in aqueous ethanol at ambient conditions. Metal-free synthesis, high atom-economy, good to excellent yields, short reaction time, operational simplicity, eco-friendliness, and mild reaction conditions are some of the important features of his protocol. (C) 2019 Elsevier Ltd. All rights reserved.