Zn-VCO3 hydrotalcite: A highly efficient and reusable heterogeneous catalyst for the Hantzsch dihydropyridine reaction

Abstract

The Zn-VCO3 hydrotalcite was found to be an excellent solid catalyst for the one-pot synthesis of triphenylpyridine-3,5-dicarboxamide via Hantzsch reaction of acetoacetanilide, ammonium hydroxide and various aromatic aldehydes. The combinatorial syntheses were achieved for the first time using hydrotalcite as a heterogeneous catalyst. The catalyst was active for the Hantzsch reaction in water at 60°C. The products were isolated in good yields (85–93%) with short reaction times (2–3h). The resulting substituted dihydropyridines were characterized and confirmed by 1H and 13C NMR, FTIR, and HRMS spectral data and the solid catalyst was characterized by XRD, BET, SEM and TEM. The newly synthesized heterogeneous solid catalyst offers simple means for recovery and the isolated catalyst was reused for five rounds for the synthesis of compound 4a, without significant loss of catalytic activity. For all the other reactions carried out with the recycled catalyst, results were similar to with the fresh catalyst.