PEG–SO3H Catalyzed, Environmentally Friendly Synthesis of Hantzsch 1,4-Dihydropyridines under Solvent-Free Conditions

A highly efficient, simple, convenient, and eco-friendly methodology for the synthesis of 1,4-dihydropyridines has been demonstrated. A biodegradable, polymer-supported catalyst, PEG–SO3H, was applied for the synthesis of 1,4-dihydropyridines via the Hantzsch-type condensation reaction under solvent-free conditions. The PEG-SO3H acts as an acidic mediator to facilitate the Hantzsch-type condensation and at the same time as the reaction solvent. The significant advantages of this methodology are high yields of products, short reaction time, the economic viability of the catalyst, handling of the catalyst, ease of preparation of the catalyst, and ease of product isolation. Furthermore, the solvent-free preparation of 1,4-DHPs is an environmentally benign method. The products were characterized by FT-IR and 1H NMR spectroscopy, and by comparison with authentic samples.