A simple and efficient protocol for one-pot three-component synthesis of structurally diverse dialkyl 2-amino-3-cyano-4H-chromen-4-ylphosphonates from the condensation of salicylaldehydes, malononitrile, and trialkyl phosphite using silver nanoparticles as catalyst in ethanol at reflux has been developed. Selected new compounds were evaluated for their antioxidant activity by free radical screening using 2,2-diphenyl-1-picrylhydrazyl (DPPH) method. Among the compounds employed, 5a, 5 b, and 5 h showed promising DPPH radical scavenging activities compared to the experimental standards at low concentration (100 µg/mL) after 24 h incubation.

An efficient and simple protocol has been developed for the synthesis of 3,4-dihydropyrimidin-2-(1H)-ones by a one-pot three-component cyclocondensation reaction of an aromatic aldehyde, β-ketoester, and urea or thiourea under solvent-free conditions using triethylamine (Et3N) as catalyst for the Biginelli reaction.