Novel biocompatible core/shell Fe3O4@NFC@Co(ii) as a new catalyst in a multicomponent reaction: an efficient and sustainable methodology and novel reusable material for one-pot synthesis of 4 H-pyran and pyranopyrazole in aqueous media

Abstract

Today, due to the developing need for inexpensive catalysts, recyclable magnetic nanocatalysts immobilized on polysaccharides possess many advantages over classical heterogeneous catalysts. However, cellulose has been an appealing material in catalysis science and technology. In this work, by controlling the interaction between the inorganic complexes and the support material, we designed a high activity nanostructured combination of a magnetic nanoparticle Fe₃O₄@NFC@Co(ii) terminated complex as a multi-nuclear catalyst. This protocol involves an environment friendly approach using cobalt acetate. The magnetic nanostructure Fe₃O₄@NFC@Co(ii) can be used as a novel, green, and a powerful catalyst that demonstrates a short reaction time, high yield and easy procedure for the cascade Knoevenagel-Michael-cyclocondensation reaction for the one-pot synthesis of 4H-pyrans and pyranopyrazoles. The superparamagnetic nanocomposite could be conveniently separated by using an external magnet. Moreover, the catalyst could be reused at least five times in new reaction runs without a noticeable loss of activity. The prepared catalyst was characterized by FT-IR, XRD, VSM, FESEM, EDAX, TEM, ICP, and TGA techniques. The experiments were achieved with good yields and implied that the catalytic method was effective and convenient for heterocyclic synthesis.

Scheme 1. The synthetic route for Fe₃O₄@NFC@Co(ii).

Scheme 2. Synthesis of 4H-pyrans promoted by Fe₃O₄@NFC@Co(ii) nanocatalyst.

Scheme 3. Synthesis of pyranopyrazoles promoted by Fe₃O₄@NFC@Co(ii) nanocatalyst.

Fig. 1. FT-IR spectra of (a) Fe₃O₄, (b) Fe₃O₄@NFC and (c) Fe₃O₄@NFC@Co(ii).

Fig. 2. XRD spectra of (a) Fe₃O₄, (b) CoO and (c) Fe₃O₄@NFC@Co(ii).

Fig. 3. TG/DTG thermogram for Fe₃O₄@NFC@Co(ii) catalyst.

Fig. 4. FESEM image (a) Fe₃O₄ and (b) Fe₃O₄@NFC@Co(ii).

Fig. 5. EDX image of Fe₃O₄@NFC@Co(ii).

Fig. 6. VSM pattern (a) Fe₃O₄ and (b) Fe₃O₄@NFC@Co(ii).

Fig. 7. TEM image (a and b) and particle size distribution histogram (c) of Fe₃O₄@NFC@Co(ii).

Scheme 4. Possible reaction mechanism for one-pot synthesis of polyfunctionalized 4H-pyrans over Fe₃O₄@NFC@Co(ii).

Scheme 5. Possible reaction mechanism for one-pot synthesis of polyfunctionalized pyranopyrazole over Fe₃O₄@NFC@Co(ii).

Fig. 8. Recycling activity of the Fe₃O₄@NFC@Co(ii) NPs.

Fig. 9. FESEM image and FTIR spectra of Fe₃O₄@NFC@Co(ii): (a) fresh (IR), (b) after 4H-pyran and (c) after pyranopyrazole.