Ultrasound-Promoted Expedient and Green Synthesis of Diversely Functionalized 6-Amino-5-((4-hydroxy-2-oxo-2H-chromen-3-yl)(aryl)methyl)pyrimidine-2,4(1H,3H)-diones via One-Pot Multicomponent Reaction under Sulfamic Acid Catalysis at Ambient Conditions

Development of an ultrasound-promoted green protocol to access pharmaceutically relevant functionalized coumarin-uracil molecular hybrids, 6-amino-5-((4-hydroxy-2-oxo2H-chromen-3-yl)(aryl)methyl)pyrimidine-2,4(1H,3H)-diones (4/4'), has been accomplished based on a three-component tandem reaction between 4-hydroxycoumarin (1), substituted aromatic aldehydes (2), and 6-aminouracils (3)/6-amino-2-thiouracil (3') under sulfamic acid-catalysis in aqueous ethanol. Metal-free onepot synthesis, rapid reaction-rate with good to excellent yields, use of cost-effective and eco-friendly catalyst and solvent, energy efficiency, easy isolation of products without the need of column chromatographic purification, reusability of reaction media, large-scale synthetic applicability, and excellent green credential parameters of the process are the salient features of this newly developed method.