Four-component one-pot synthesis of unsymmetrical polyhydroquinoline derivatives using 3-methyl-1-sulfonic acid imidazolium hydrogen sulfate as a catalyst

3-Methyl-1-sulfonic acid imidazolium hydrogen sulfate has been used as an efficient, halogen-free, and reusable Brönsted acidic ionic liquid catalyst for the synthesis of ethyl-4-aryl/heteryl-hexahydro-trimehtyl-5-oxoquinoline-3-carboxylates via the one-pot condensation of dimedone with aryl/heteryl aldehydes, ethyl acetoacetate, and ammonium acetate under solvent-free conditions. This method has the advantage of being clean and simple, as well as providing the desired product in high yield over a short reaction time. Furthermore, the catalyst could be recycled and reused four times without any discernible reduction in activity.

Graphical AbstractOne-pot condensation of dimedone with aryl/heteryl aldehydes, ethyl acetoacetate and ammonium acetate in the presence of 3-methyl-1-sulfonic acid imidazolium hydrogen sulfate under solvent-free conditions. The catalyst could be recycled and reused at least four times without any significant loss in its activity. The structures of the new products were established from their spectral properties (IR, 1H NMR, and MS), as well as their melting point and elemental analysis data. The known products were characterized by their physical data (m.p., IR, 1H NMR) and through a comparison with the authentic samples.Figure optionsDownload full-size imageDownload as PowerPoint slide