Eco-Friendly One-Pot Synthesis of Tetrahydrobenzo[b]Pyran and Dihydropyrano[3,2-c]Chromene Derivatives Using Functionalized Fe3O4@SiO2@SO3H Under MWI

Abstract

The present work describes a greener method of preparation of Fe₃O₄ nanoparticles, which are then functionalized to Fe₃O₄@SiO₂@SO₃H, and employed in the one-pot three-component synthesis of tetrahydrobenzo[b]pyran and dihydropyrano[3,2-c]chromene derivatives. These synthesized derivatives are an important class of heterocyclic scaffolds and exhibit significant potential as anti-coagulant, diuretic, spasmolytic, anticancer, and anti-anaphylactic agents. The prepared MNP-based catalysts were characterized using XRD, FE-SEM, VSM, TG-DTA, and Raman spectroscopy. The synthesis of derivatives involved the condensation reaction of enolizable compounds with aldehyde, dimedone, and ethyl cyanoacetate for tetrahydrobenzo[b]pyran, and the reaction of aromatic aldehyde, 4-hydroxycoumarin, and malononitrile for dihydropyrano[3,2-c]chromene synthesis. The reaction was optimized using different techniques such as stirring, ultrasonication, and microwave irradiation, with microwave irradiation method demonstrating faster product separation and high yield. The homogeneity of the isolated product was analyzed by FT-IR,¹H-¹³C-NMR, and mass spectrometry. The advantages of this method include its simplicity, eco-friendliness, cost-effectiveness, and it also evades the use of toxic metals and solvents. The product is easily isolated through a simple workup process and recrystallization using ethanol yields pure product isolation.