Preparation, characterization and application of novel ionic liquid as an efficient and reusable catalyst for the solvent-free synthesis of hexahydroquinolines

Abstract

A novel Brønsted acidic ionic liquid 1-butyl-3-sulfonic acid imidazolium chloride, [Bsim]Cl, was synthesized. Its structure was investigated using FT-IR, 1H NMR, 13C NMR, mass, UV, TGA and DTA spectra. This ionic liquid, with one acidic functional group, is utilized as a highly efficient and homogeneous catalyst for the promotion of hexahydroquinolines via one-pot multi-component condensation of aromatic aldehydes, dimedone, ethyl acetoacetate, and ammonium acetate under solvent-free conditions. This new method consistently has the advantages of excellent yields and short reaction times. Further, the catalyst could be reused and recovered at least four times without appreciable loss of activity.