Facile protocol, metal-free, one-pot synthesis of 2-amino-4H-chromenes, benzimidazoles, and benzothiazoles via acidic ionic liquids based on pyridinium

Abstract

In a one-pot tandem condensation reaction, three functional ionic liquids (ILs) derived from pyridinium were employed as green, reusable, and efficient catalysts for the synthesis of important medicinal chemistry derivatives such as 2-amino-4H-chromenes. Additionally, benzimidazoles and benzothiazoles were synthesized using these catalysts. The ILs were favored for their easy set-up, high yields, and short synthesis times for the desired products. Moreover, the ILs could be easily recovered and reuse multiple times without significant loss of catalytic activity. Characterization of the synthesized compound was achieved through FT-IR, ¹H NMR, ¹³C NMR, TGA and melting point analysis. The compounds were prepared with good to excellent isolated yields under mild conditions, while the synthesis of benzimidazoles and benzothiazole derivatives was successful at both reflux and room temperature conditions. Finally, each class of compound was described along with its corresponding synthesis mechanism.