Agro-waste Catalyzed Synthesis of Dihydropyrano[3,2-c]chromene,Antioxidant and Electrochemical Behavior Studies

Introduction: Dihydropyrano[3,2-c]chromene derivatives are of considerable interest due to their wide range of pharmacological properties. Their synthesis via the reaction of aromatic aldehydes with malononitrile or ethyl cyanoacetate and 4-hydroxycoumarin, catalysed by various agents, has been well described in the literature. The present work develops an inexpensive, greener synthetic method that affords excellent yields and enables the isolation of pure products. Methods: The present study demonstrates an inexpensive and environmentally friendly method for synthesising dihydropyrano[3,2-c]chromene derivatives. WEBPA was employed as a greener, homogeneous agro-waste–based catalytic medium, with microwave irradiation (MWI) used to accelerate the reaction. Selected derivatives were further evaluated for their antioxidant activity and electrochemical behaviour. Results: Microwave-assisted synthesis of dihydropyrano[3,2-c]chromene derivatives provided a rapid and eco-friendly route to the target compounds. The agro-waste-based catalytic medium used in this work eliminated the need for hazardous organic solvents and additional additives. Selected derivatives were screened for their antioxidant activity and electrochemical properties. Discussion: The developed greener and inexpensive method for synthesising dihydropyrano[3,2- c]chromene derivatives under MWI offers an efficient and environmentally friendly approach. The method does not require hazardous solvents or catalysts, and the products were obtained in a pure state after simple recrystallisation, without the need for chromatographic purification. Biological evaluation of selected derivatives for their antioxidant and electrochemical properties demonstrated comparable and meaningful activities. Conclusion: The present work describes an efficient protocol for the synthesis of dihydropyrano[3,2-c]chromene derivatives via a three-component reaction catalysed by the greener solvent medium WEBPA. The method is facile, rapid, inexpensive, and involves a straightforward workup, affording the final compounds in pure form. Products were isolated by simple filtration and recrystallisation, yielding chromatographically pure materials with excellent yields. The homogeneity of the isolated compounds was confirmed using various spectroscopic techniques. Several selected derivatives (4h, 4k, 4l, 6b, 6e, 6f, and 6g) exhibited significant antioxidant activity. Furthermore, their electrochemical behaviour was studied for the first time using cyclic voltammetry, and the examined derivatives displayed comparable redox potentials.