One-Pot and Solvent-Free Synthesis of 1,4-Dihydropyridines and 3,4-Dihydropyrimidine-2-ones Using New Synthetic Recyclable Catalyst via Biginelli and Hantzsch Reactions

Abstract

Pyridine dicarboxylic acid guanidine–cobalt complex (PDAG-Co) (3) catalyzes one-pot, three-component coupling of aldehydes, β-dicarbonyl compounds, and ammonium acetate to afford the corresponding 1,4-dihydropyridines (1,4-DHPs) via Hantzsch reaction. 3,4-Dihydropyrimidine-2-ones (3,4-DHPMs) and their sulfur analogs are also synthesized under the same conditions via Biginelli condensation protocol. The catalyst is reusable at least five times, highly efficient, easily prepared, and used under mild reaction conditions.

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GRAPHICAL ABSTRACT

Keywords:

• Biginelli
• cobalt-catalyst
• 3,4-dihydropyrimidine-2-ones
• 1,4-dihydropyridines
• Hantzsch

ACKNOWLEDGMENTS

We gratefully acknowledge Robabeh Alizadeh (University of Damghan, Faculty of Chemistry) for her comments and providing the ORTEP of crystals of catayst PDAG-Co (3). We also acknowledge Ali Akbar Agah, who prepared the catalysts whenever we needed to run the reactions. He is passed away and unfortunately no longer with us due to a sad accident.