A Simple and Efficient One-Pot Synthesis of ۱,۴-Dihydropyridine and Polyhydroquinoline Derivatives Using Phosphosulfonic Acid as a Heterogeneous Catalyst under Solvent-Free Conditions

Phosphosulfonic acid (PSA) was found to be an efficient catalyst for the one-pot three-component Hantzsch condensation reaction of arylaldehydes, ethylacetoacetate and ammonium acetate to afford the corresponding ۱,۴-dihydropyridine and polyhydroquinoline derivatives in high yields. PSA was also applied for the one-pot preparation of polyhydroquinolines via four-component reaction of arylaldehydes, ethylacetoacetates, dimedone and ammonium acetate. The main advantages of the present approach are short reaction times, clean reaction profiles, catalyst recyclability, and facile experimental and workup procedures.