A mild route for one pot synthesis of 5,6-unsubstituted 1,4-dihydropyridines catalyzed by sulphated mixed metal oxides
Synthesis of 1,4-dihydropyridines via a four component one pot reaction starting from α,β-unsaturated aldehyde, β-keto ester, amine and alcohol, catalysed by SO42−/CexZr1−xO2 is explored. The method has several advantages such as reusability of catalyst, avoidance of a multistep procedure and readily available starting materials. The protocol gives high to moderate yields for structurally diverse amines, β-keto esters and α,β-unsaturated aldehydes. SO42−/CexZr1−xO2 (x = 0.02–0.15 mol%) catalysts were prepared and characterized by various analytical techniques such as XRD, FT-IR, TGA-DSC, SEM-EDAX and the total acidity.