Synthesis, Antioxidant, and Electrochemical Behavior Studies of 2-Amino-4H-Chromene Derivatives Catalyzed by WEOFPA: Green Protocol.

In this work, we have described an efficient one-pot three-component preparation of 2-amino-4H-chromene by the reaction of aromatic aldehyde (1), malononitrile, or ethylcyanoacetate (2), and α or ꞵ-naphthol or resorcinol (3) in the presence of catalyst Water Extract of Orange Fruit Peel Ash agro-waste extracted solvent medium (4 mL) with few drops of ethanol as co-solvent accelerated by microwave irradiation. The reaction is optimized by various methods such as magnetic stirring, mechanochemical, ultrasound, and microwave irradiation, but the microwave irradiation in 180 W power gave excelled yield and faster rate product isolation (4–5 min). The method developed found eco-friendly, metal-free, chemical-less, and solvent-less, inexpensive, and facile approach for the synthesis of 2-amino-4H-chromene derivatives. The final product isolated recrystallized in ethanol, and characterized by FT-IR, ¹H-, and ¹³C-NMR and LC-MS spectrometry techniques. Some of the selected chromene derivatives are subjected to antioxidant activity with concentration range 200–1,000 µg/µL by 2,2-diphenyl-1-picrylhydrazyl method. The derivatives 4a, 4 g, 4h, 6a, 6b, 6c, 8a, and 8f showed antioxidant activities and were comparable to standard ascorbic acid used. Further, studies on electrochemical behavior of selected chromene derivatives (4e, 4f, 4 g, 4i, 6c, 6f, 8d, and 8f) by cyclic voltammetry technique with 50 mVs⁻¹, and revealed that, some of these molecules are good oxidation and reduction potential. [ABSTRACT FROM AUTHOR]