N-unsubstituted dihydropyridines and pyridones via multicomponent synthesis under a bio-derived heterogeneous catalyst

Abstract

In our exploration of metal-free and cost-effective heterogeneous catalysts for MCRs, we identified a novel system: piperazine immobilized within an agar matrix, functioning as a recyclable and reusable catalyst. This system efficiently facilitates the synthesis of dihydropyridines (DHPs) via one-pot condensation of dimedone, aldehydes, ammonium acetate, and various active methylene compounds—specifically malononitrile, acetophenone, or Meldrum's acid. A broad range of products was obtained, underscoring the versatility of the methodology. Notably, our prior investigations demonstrated this catalyst's efficacy in synthesizing N-aryl-substituted DHPs, affirming its general applicability. Additionally, fluorescence and UV absorption studies, along with in-depth characterization using 2D NMR spectroscopy, were conducted to confirm the structure and peak assignments of the synthesized products.