Cobalt complexes were covalently anchored onto the surface of silica by the complexation of organically modified silicas with Co(OAc)(2) and CoCl2 and investigated for the oxidative aromatization of Hantzsch 1,4-dihydropyridines using molecular oxygen. The catalyst obtained by the complexation of Co(OAc)(2) with organically modified 3-aminopropyl silica (Cat 1) was found to be most effective and stable under the reaction conditions. It can be easily recovered and recycled. The work-up procedure is simple and the corresponding pyridines were obtained in good to excellent yields. (C) 2008 Elsevier B.V. All rights reserved.