Polyhydroquinolines have been synthesized efficiently using a novel Co(II) complex based on5-nitro-N1-((pyridin- 2-yl)methylene)benzene-1,2-diamine(CoL2). This green catalyst has been utilized in a one-pot four-component Hantzsch condensation of dimedone, aldehydes, ethyl acetoacetate and ammonium acetate under solvent and free-solvent conditions. This method offers several advantages such as easy isolation of product, environmentally benign and excellent yields.