Nickel nanoparticles-catalyzed synthesis of 1,4-dihydropyridines under mild and solvent-free conditions catalytic behaviors of nickel nanoparticles

A novel one-pot, four-component synthesis of C5-unsubstitiuted 1,4-dihydropyridines via unsymmetrical Hantzsch reaction using nanosized Nickel as a heterogeneous catalyst under mild reaction conditions, is described. The nickel nanoparticles, spherical in shape, have been successfully synthesized by the chemical reduction of nickel chloride with hydrazine at room temperature without any protective agent and inert gas protection. The effect of [Ni2+]/ [N2H4] in size and morphology of catalyst was investigated. Well characterized nickel nanoparticles showed remarkable activity for synthesis of C5-unsubstitiuted 1,4-dihydropyridines and could be recycled for three consecutive runs. The performance of this reaction under solvent free conditions with heterogeneous catalysts like Ni nanoparticles could enhance its efficiency from an economic as well as a green chemistry.