Hydrated Ferric Sulfate Catalyzed Synthesis of 5,6-Unsubstituted 1,4-Dihydropyridines Using Three-Component Reaction.

A wide variety of 5,6-unsubstituted 1,4-dihydropyridines derivatives (4a–q) were synthesized through a one-pot three-component reaction from a,b-unsaturated aldehydes, amines, and 1,3-diketones at room temperature using hydrated ferric sulfate as a Lewis acid catalyst. The key features of the present protocol are mild and simple reaction procedure, good to excellent yields, and use of inexpensive, recyclable, and environmentally benign catalyst.