An Efficient and Sustainable Protocol for the Synthesis of Poly-Functionalized-Pyran Derivatives under Ultrasound Irradiation

A highly efficient and catalyst-free green synthetic protocol is developed for the synthesis of two series of poly-functionalized pyran derivativesviathe one-pot reaction of aromatic aldehydes, malononitrile, and either dimedone or 1,3-dimethyl barbituric acid with EtOH: H2O (1:1 v/v) as solvent under ultrasound irradiation. Excellent yields (90-99%) of desired pyran derivatives were obtained for rapid reaction time 5 min. The structural features of the synthesized compounds were fully characterized by spectroscopic techniques (IR, (HRMSH)-H-1, and(13)C NMR). A simple workup, clean reaction profile, short reaction times, excellent yields, 95% atom economy, and 100% carbon efficiency are the benefits of the proposed protocol. In addition, the circumvention of the chromatographic separations is the further advantage of the procedure.