Solvent-free synthesis of 4H-pyranonaphthoquinones using highly active and stable polymer-grafted layered double hydroxides (LDHs-g-POEGMA) as an efficient and reusable heterogeneous catalyst

Abstract

Benzo[g]chromene-5,10-diones (chromene-diones) have been synthesized by an efficient, simple and green one-pot domino protocol by multi-component condensation of 2-hydroxy-1,4-naphthoquinone with aldehydes and (E)-N-methyl-1-(methylthio)-2-nitroethenamine in the presence of poly(oligoethylene glycol methacrylate)-g-supported layered double hydroxides (LDHs-g-POEGMA), under solvent-free condition. The significant features of this green reaction include short reaction time, high product yields in pure form, eco-friendly method, avoidance of toxic solvents and no need for purification of the product by column chromatography. Furthermore, the catalyst (LDHs-g-POEGMA) is reused for several consecutive runs without losing its catalytic activity. The importent features of this methodology are green reaction, simple procedure, reusability and high efficiency of the catalyst and easy workability.