Magnetically retrievable nano crystalline CuFe2O4 catalyzed multi-component reaction: a facile and efficient synthesis of functionalized dihydropyrano[2,3-c]pyrazole, pyrano[3,2-c]coumarin and 4H-chromene derivatives in aqueous media†
CuFe2O4 magnetic nanoparticles were synthesized and recognized as an efficient catalyst for the one-pot synthesis of dihydropyrano[2,3-c]pyrazole, pyrano[3,2-c]coumarin and 4H-chromene derivatives at mild conditions and in excellent yields. The four component reaction (4CRs) of a wide variety of substituted hydrazine derivatives, ethyl acetoacetate, dialkyl acetylenedicarboxylates and alkyl nitrile derivatives (malononitrile and ethyl cyanoacetate) gave the targeted dihydropyrano[2,3-c]pyrazoles. When two equivalents of dialkyl acetylenedicarboxylates were introduced replacing ethyl acetoacetate, a new four-component reaction took place providing another type of dihydropyrano[2,3-c]pyrazole derivatives. An efficient and practical route to pyrano[3,2-c]coumarin and 4H-chromene framework has also been developed by one-pot, three-component reaction (3CRs) of 4-hydroxycoumarin/dimedone/cyclohexane-1,3-dione, dialkyl acetylenedicarboxylates and alkyl nitriles. CuFe2O4 magnetic nanoparticles were prepared by a simple and effective citric acid complex method and characterized by using XRD, FT-IR, EDX and TEM image. The catalyst was recycled for six cycles with almost unaltered catalytic activity. All reactions were easily performed and proceeded with high efficiency under very simple and mild conditions and gave excellent yields avoiding time-consuming, costly syntheses, and tedious workup and purification of products.