Activity of immobilized metallic phthalocyanines in the multicomponent synthesis of dihydropyridine derivatives and their subsequent aromatization

Abstract

Several supported metallo-sulphonated phthalocyanines (FePcS-NH2-SiO2, CoPcS-NH2-SiO2, and CuPcS-NH2-SiO2) and iron hexadecachlorinated phthalocyanines (FePcCl16-NH2-SiO2 and FePcCl16-NH2-SBA-15) were synthesized and evaluated as alternative catalysts for a green multicomponent Hantzsch reaction between an aromatic aldehyde, methyl or ethylacetoacetate and ammonium acetate to obtain the corresponding dihydropyridines or phenylpyridines depending on the reaction conditions. High selectivities (over 80%) to the 2-phenylpyridines, under oxidant and solvent free conditions at room temperature were obtained. While the formation of 1,4-dihydripyridine derivatives were favored at temperatures above 45 °C (selectivities around of 50%). In addition, the 1,4-dihydripyridine derivatives were aromatized to the corresponding pyridines using t-BuOOH as oxidant, acetonitrile as solvent and at a reaction temperature of 50 °C.