Polyvinylpolypyrrolidone supported chlorosulfonic acid: An efficient catalyst for the one-pot synthesis of hexahydroquinolines

ABSTRACT Polyvinylpolypyrrolidone supported chlorosulfonic acid ([PVPP-SO3H]+Cl-) was synthesized and evaluated as a recoverable catalyst for the one-pot synthesis of hexahydroquinolines by reaction of arylaldehydes, dimedone (5,5-dimethylcyclohexane-1,3-dione) or 1,3-cyclohexanedione, ethylacetoacetate and ammonium acetate in high to excellent yield in ethanol at 70 °C. The [PVPP-SO3H]+Cl- catalyst was characterized via Fourier transform infrared spectroscopy (FT-IR) and thermal gravimetric analysis (TGA). The capacity of the reagent was determined by titration and found to be 12 mmol/g, which shows a high loading of H+ per gram of the catalyst. Moreover, the catalyst could be recycled several times without significant loss of its catalytic activity. Clean methodologies, easy work-up procedure, high yield and simple preparation of the catalyst are some advantages of this work.