In this work, we report the use of bulk Wells-Dawson acid (H6P2W18O62.24H2O) as a reusable, heterogeneous catalyst to obtain substituted 1,4-dihydropyridines for the Hantzsch multicomponent reaction, using various aldehydes, alkyl acetylacetates and ammonium acetate or aniline as source of ammonia. The reaction experiments were performed in the absence of solvent, at 80°C. Under these conditions fourteen examples were obtained with very good yields (90-98%) and high selectivity. The catalyst was easily recycled and reused without appreciable loss of their catalytic activity. The synthetic method presented is a simple, clean and environmentally friendly alternative for obtaining substituted dihydropyridines.
Keywords: Wells-Dawson, dihydropyridines, multicomponent reactions, acid catalysis, Hantzsch multicomponent reaction, Alzheimer's disease, Nifedipine, Felodipine, Amlodipine, heteropolyacid catalyst, phenols, imidoalcohols, dihydropyrimidinones, Biginelli, nuclear magnetic resonance, Drechsel method, TLC