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

Polyvinylpolypyrrolidone supported chlorosulfonic acid ([PVPPSO3H]+Cl) was synthesized and evaluated as a recoverable catalyst for the onepot synthesis of hexahydroquinolines by reaction of arylaldehydes, dimedone (5,5dimethylcyclohexane1,3dione) or 1,3cyclohexanedione, ethylacetoacetate and ammonium acetate in high to excellent yield in ethanol at 70 °C. The [PVPPSO3H]+Cl catalyst was characterized via Fourier transform infrared spectroscopy (FTIR) 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 workup procedure, high yield and simple preparation of the catalyst are some advantages of this work.