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<p>In this study, an eco-friendly synthesis of 2,4-disubstituted benzo [4,5]imidazo[1,2-a]pyrimidine analogs was developed using a microwave approach, utilizing <i>Carissa edulis</i> fruit extract stabilized NiTiO<sub>3</sub> nanoparticles decorated with a bentonite clay (NiTiO<sub>3</sub>/bentonite) composite as an effective heterogeneous catalyst. A facile ultrasonication method was employed to prepare different loading of NiTiO<sub>3</sub>/bentonite composites (5%, 10%, 15%, 20%, and 25%). Owing to its high surface area and active sites the NiTiO<sub>3</sub>/bentonite composite was demonstrated to be an effective heterogeneous catalyst that provides high yields of 2,4-disubstituted benzo [4,5]imidazo[1,2-a]pyrimidine. The moderate surface area and active sites, chemical states, high thermal stability, and purity of the NiTiO<sub>3</sub>/bentonite composites were confirmed using BET, XPS, TGA, XRD, and FT-IR. FE-SEM and elemental mapping were performed. HR-TEM analysis revealed that the NiTiO<sub>3</sub> nanoparticles had an aggregated spherical shape with an average particle size of 22&#xa0;nm and a d-spacing of 0.21&#xa0;nm. Various optimization parameters, including solvent, catalyst type, catalyst loading, temperature, microwave power was explored for synthesis of 2,4-disubstituted benzo [4,5]imidazo[1,2-a]pyrimidine. Mechanistic investigation reveals that initially, the aldehyde and ketone produce α, β-unsaturated ketone through Claisen-Schmidt condensation. Resulting intermediate reacts with 2-aminobenzimidazole followed by intramolecular cyclization and dehydrogenation process yielding the final product. The optimal NiTiO<sub>3</sub>/bentonite catalyst achieved up to 94% yield with high turnover number and turnover frequency. Remarkably, the prepared heterogenous catalyst shows high catalytic activity, offering excellent yields even after six recycling cycles.</p> Graphical Abstract <p></p>

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Bentonite Supported NiTiO3 Composite as Heterogeneous Catalyst for Synthesis 2,4-Disubstituted Benzo[4,5]imidazo[1,2-a]pyrimidine

  • 期刊论文

  • 发表日期：

    2025年4月17日

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  • Periasamy Vinoth Kumar,
  • Selvaraj Mohana Roopan,
  • Gunabalan Madhumitha

摘要

In this study, an eco-friendly synthesis of 2,4-disubstituted benzo [4,5]imidazo[1,2-a]pyrimidine analogs was developed using a microwave approach, utilizing Carissa edulis fruit extract stabilized NiTiO3 nanoparticles decorated with a bentonite clay (NiTiO3/bentonite) composite as an effective heterogeneous catalyst. A facile ultrasonication method was employed to prepare different loading of NiTiO3/bentonite composites (5%, 10%, 15%, 20%, and 25%). Owing to its high surface area and active sites the NiTiO3/bentonite composite was demonstrated to be an effective heterogeneous catalyst that provides high yields of 2,4-disubstituted benzo [4,5]imidazo[1,2-a]pyrimidine. The moderate surface area and active sites, chemical states, high thermal stability, and purity of the NiTiO3/bentonite composites were confirmed using BET, XPS, TGA, XRD, and FT-IR. FE-SEM and elemental mapping were performed. HR-TEM analysis revealed that the NiTiO3 nanoparticles had an aggregated spherical shape with an average particle size of 22 nm and a d-spacing of 0.21 nm. Various optimization parameters, including solvent, catalyst type, catalyst loading, temperature, microwave power was explored for synthesis of 2,4-disubstituted benzo [4,5]imidazo[1,2-a]pyrimidine. Mechanistic investigation reveals that initially, the aldehyde and ketone produce α, β-unsaturated ketone through Claisen-Schmidt condensation. Resulting intermediate reacts with 2-aminobenzimidazole followed by intramolecular cyclization and dehydrogenation process yielding the final product. The optimal NiTiO3/bentonite catalyst achieved up to 94% yield with high turnover number and turnover frequency. Remarkably, the prepared heterogenous catalyst shows high catalytic activity, offering excellent yields even after six recycling cycles.

Graphical Abstract