An efficient, simple and environmentally benign methodology has been developed for the
synthesis of 5,6-unsubstituted 1,4-dihydropyridine derivatives by a three-component condensation of
β-keto esters, amines and α,β-unsaturated aldehydes under solvent-free conditions catalyzed by an
aprotic imidazole-based zwitterionic salt. The key advantages of this protocol are metal-free reaction
conditions, short reaction time, high yields, reusability of the catalyst, and easy work-up. A variety of
dihydropyridine derivatives have been synthesized with high yields at room temperature and only water
is formed as a green by-product.
Keywords: Dihydropyridines, imidazolium zwitterion, multicomponent, organocatalysis, reusability, solvent-free.
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