Hantzch reaction for the synthesis of 4-(2-pyrrolyl)-dihydropyridines in the presence of Fe3O4@Chitosan–SO3H nanoparticles as catalyst

1,4-Dihydropyridines belong to an important class of organic compounds which include unique structural motifs in a wide range of natural products and biologically active molecules [1]. They are an important class of heterocyclic compounds that have a broad scope of pharmacological and biological activities such as antidiabetic, antitumor, vasodilator, bronchodilator, geroprotective and anti-atherosclerotic properties. Therefore, the use of dihydropyridine moiety in the skeletons of heterocyclic and biological molecules is of great interest [2-4]. One of the methods for the synthesis of this compounds is the Hantzch reaction. Among the several methodologies of this reaction, using of heterogeneous magnetic catalysts has been widely considered. In this study, the efficacy of magnetic sulfonated chitosan as catalyst for synthesis of dihydropyridines via one-pot three-component condensation reaction has been examined. Treatment of N-substituted-pyrrole-2-carbaldehyde (1 eq.), 1,3-dicarbonyls (2 eq.) and ammonium acetate (1 eq.) in the presence of Fe3O4@Chitosan–SO3H (10 mol%) as a heterogeneous catalyst at 70ºC gave the desired products in good yields. (Figure 1). The merits of this method include mild reaction conditions, high yield of products, short reaction times, and reusability of the catalyst.