Design, preparation and characterization of a new ionic liquid, 1,3-disulfonic acid benzimidazolium chloride, as an efficient and recyclable catalyst for the synthesis of tetrahydropyridine under solvent-free conditions†
In the present work, 1,3-disulfonic acid benzimidazolium chloride as a new ionic liquid, is synthesized, and characterized by studying its FT-IR, 1H NMR, 13C NMR as well as mass spectra. This ionic liquid is used as an efficient, homogeneous and recyclable catalyst for synthesis of highly functionalized tetrahydropyridine via one-pot multi-component condensation of aromatic aldehydes, ethyl acetoacetate, and anilines under solvent-free conditions. The present synthetic route is a green protocol offering several advantages, such as high yield of products, shorter reaction time, mild reaction conditions, minimizing chemical waste and easy work-up procedures. Further, the catalyst could be reused and recovered at least four times without appreciable loss of activity.