Cobalt Nanoparticles Promoted Highly Efficient One Pot Four-Component Synthesis of 1,4-Dihydropyridines under Solvent-Free Conditions

A straightforward and general method has been developed for the synthesis of C5-unsubstitiuted 1,4-dihydropyridines by a reaction using dimedone, acetophenone, aromatic aldehydes, and ammonium acetate in the presence of a catalytic amount of Co nanoparticles as a heterogeneous and eco-friendly catalyst with high catalytic activity at room temperature under solvent-free conditions. This catalyst is easily separated by magnetic devices and can be reused without any apparent loss of activity for the reaction. In addition, it is very interesting that when using Co nanoparticles as a catalyst, spatially-hindered aldehydes such as 2-methoxy-, 2-fluoro-, and 2-chloro-aldehydes are suitable for this reaction.

Graphical abstractThis paper presents a simple and convenient route for the preparation of 1,4-dihydropyridines over cobalt nanoparticles by a four-component reaction under solvent-free conditions. The reaction under the influence of heterogeneous catalysts such as Co nanoparticles has enhanced efficiency from an economic as well as a green chemistry point of view.Figure optionsDownload full-size imageDownload as PowerPoint slide