Efficient Synthesis of Pyrimido[1,2-a]Benzimidazoles and Ethyl Pyrimido[1,2-a]Benzimidazole-3-Carboxylates Using Brönsted Acidic Ionic Liquid Supported on Nanoporous Na⁺-Montmorillonite

ABSTRACT

In this work, nanoporous sodium montmorillonite clay (Na⁺–MMT) was successfully modified with 1-methyl-3-(trimethoxysilylpropyl)-imidazolium hydrogen sulfate (Na⁺–MMT–[pmim]HSO₄). This immobilized acidic ionic liquid showed excellent catalytic activity for the synthesis of pyrimido[1,2-a]benzimidazoles and ethyl pyrimido[1,2-a]benzimidazole-3-carboxylates via three-component reactions between aldehydes, 2-aminobenzimidazole and malononitrile or β-dicarbonyl compounds. The procedure gave the products in high yields in very short reaction times at 100°C under solvent-free conditions. Also, this catalyst can be reused for five times without loss of its catalytic activity.

KEYWORDS:

• 2-Aminobenzimidazole
• immobilization of ionic liquid
• Na⁺-MMT-[pmim]HSO₄
• sodium montmorillonite
• pyrimido[1,2-a]benzimidazoles

Acknowledgments

The authors are grateful to the Guilan University Research Council for the partial support of this work.