Magnetic carbon nanotube-catalyzed multicomponent synthesis of 5-substituted-1 H-tetrazoles

Abstract

This study presents a pioneering approach with the introduction of a novel magnetic carbon nanotube composite, AlFe₂O₄-MWCNT-TEA-Ni(ii), designed as an efficient catalyst for the multicomponent synthesis of 5-substituted-1H-tetrazoles (18 examples, yields 89-98%). The primary objectives were to develop and evaluate this catalyst's ability to promote the formation of tetrazoles under eco-friendly conditions. The methods involved synthesizing the catalyst by combining AlFe₂O₄, MWCNTs, TEA, and Ni(ii), then testing its catalytic activity using various aromatic aldehydes, hydroxylamine, and sodium azide in DMF at 50 °C. The reaction parameters, including temperature, catalyst amount, and reaction time, were optimized for maximum yield and selectivity. Results showed that the catalyst achieved high yields of tetrazoles and demonstrated significant selectivity in a remarkably short reaction time, showcasing its exceptional efficiency. The magnetism of AlFe₂O₄ facilitated easy recovery and recyclability (seven runs), underscoring the catalyst's sustainability. This system's advantages include its high activity, reusability, and environmentally friendly nature, making it a promising approach for green nitrogen-rich heterocycle synthesis. Prospects involve exploring the catalyst's potential in large-scale applications, expanding its use to other heterocyclic syntheses, and investigating its performance with different substrates. This work underscores the significant role of integrating magnetic nanomaterials into catalytic systems to promote sustainable and efficient organic synthesis methods, offering a promising future for the field.

Fig. 1. Some bioactive compounds contain structures containing substituted 5-phenyl-1H-tetrazole derivatives.

Scheme 1. Synthesis of 5-phenyl-1H-tetrazoles.

Scheme 2. Procedure for the preparation of AlFe₂O₄–MWCNT–TEA–Ni(ii).

Fig. 2. FT-IR spectrums of AlFe₂O₄@MWCNT, AlFe₂O₄@MWCNT–TEA, and AlFe₂O₄@MWCNT–TEA–Ni(ii) nanocatalyst.

Fig. 3. EDX analysis of AlFe₂O₄@MWCNT–TEA–Ni(ii) catalyst.

Fig. 4. BET analysis of AlFe₂O₄@MWCNT–TEA–Ni(ii) nanocatalyst.

Fig. 5. SEM and TEM images of AlFe₂O₄@MWCNT–TEA–Ni(ii) catalyst at different magnifications.

Fig. 6. TGA of AlFe₂O₄@MWCNT–TEA–Ni(ii) catalyst at different magnifications.

Fig. 7. XRD patterns of AlFe₂O₄@MWCNT–TEA–Ni(ii) catalyst.

Fig. 8. VSM spectrums of AlFe₂O₄ NPs and AlFe₂O₄–MWCNT–TEA–Ni(ii) catalyst.

Fig. 9. Elemental mapping AlFe₂O₄–MWCNT–TEA–Ni(ii) nanocatalyst.

Fig. 10. Reusability of AlFe₂O₄–MWCNT–TEA–Ni(ii) as a catalyst for synthesizing 5-phenyl-1H-tetrazole (3a).

Fig. 11. After seven runs, the FT-IR spectra between the fresh and reused catalysts were compared.

Fig. 12. VSM images of AlFe₂O₄–MWCNT–TEA–Ni(ii) catalyst reused catalyst after seven runs.

Fig. 13. BET images of AlFe₂O₄–MWCNT–TEA–Ni(ii) catalyst reused catalyst after seven runs.

Scheme 3. A plausible mechanism for the click synthesis of 5-aryl-1H-tetrazoles over the catalysis of AlFe₂O₄–MWCNT–TEA–Ni(ii).

Fig. 14. Leaching experiment of AlFe₂O₄–MWCNT–TEA–Ni(ii).