Aim and Objective:
The multi-component condensation of benzil, primary amines,
ammonium acetate and various aldehydes was efficiently catalyzed using cobalt oxide nanoparticles
under ultrasonic irradiation. This approach describes an effective and facile method for the synthesis
of some novel 1,2,4,5-tetrasubstituted imidazole derivatives with several advantages such as high
yields and short reaction times and reusability of the catalyst. Moreover, the prepared heterocyclic
compounds showed high antibacterial activity against some pathogenic strains.
Materials and Method:
The facile and efficient approaches for the preparation of Co3O4
nanoparticles were carried out by one step method. The synthesized heterogeneous nanocatalyst was
characterized by spectroscopic analysis including EDX, FE-SEM, VSM, XRD and FT-IR analysis.
The as-synthesized cobalt oxide nanoparticles showed paramagnetic behaviour in magnetic field. In
addition, the catalytic influence of the nanocatalyst was examined in the one-pot reaction of primary
amines, benzil, ammonium acetate and diverse aromatic aldehydes under ultrasonic irradiation. All
of the 1,2,4,5-tetrasubstituted imidazoles were investigated and checked with m.p., 1H NMR, 13C
NMR and FT-IR spectroscopy techniques. The antibacterial properties of the heterocycles were
evaluated in vitro by the disk diffusion against pathogenic strains such as Escherichia coli (EC),
Bacillus subtillis (BS), Staphylococcus aureus (SA), Salmonellatyphi (ST) and Shigella dysentrae
(SD) species.
Results:
In this research cobalt oxide nanostructure was used as a robust and green catalyst in the
some novel imidazoles. The average particle size measured from the FE-SEM image is found to be
20-30 nm which confirmed to the obtained results from XRD pattern. Various electron-donating and
electron-withdrawing aryl aldehydes were efficiently reacted in the presence of Co3O4 nanoparticles.
The role of the catalyst as a Lewis acid is promoting the reactions with the increase in the
electrophilicity of the carbonyl and double band groups. To investigate the reusability of the catalyst,
the model study was repeated using recovered cobalt oxide nanoparticles. The results showed that
the nanocatalyst could be reused for five times with a minimal loss of its activity.
Conclusion:
We have developed an efficient and environmentally friendly method for the synthesis
of some tetrasubstituted imidazoles via three-component reaction of benzil, primary amines,
ammonium acetate and various aldehydes using Co3O4 NPs. The present approach suggests different
benefits such as: excellent yields, short reaction times, simple workup procedure and recyclability of
the magnetic nanocatalyst. The prepared 1,2,4,5-tetrasubstituted imidazoles revealed high
antibacterial activities and can be useful in many biomedical applications.
One-Pot Synthesis of Tetrasubstituted Imidazoles Catalyzed by Preyssler-Type Heteropoly Acid
