Novel bipyridinyl oxadiazole-based metal coordination complexes: High efficient and green synthesis of 3,4-dihydropyrimidin-2(1H)-ones through the Biginelli reactions

Three new metal coordination complexes, namely, [Co(BPO)(2)(H2O)(4)](BS)(2)(H2O)(2) (1), [Co(BPO)(2) (H2O)(4)](ABS)(2)(H2O)(2) (2), [Co(BPO)(2)(H2O)(4)](MBS)(2)(H2O)(2) (3) [BPO=2,5-di(pyridin-4-yl)-1,3,4-oxadiazole, BS = benzenesulphonate, ABS=4-aminobenzenesulphonate, MBS=4-methylbenzenesulphonate] were obtained under hydrothermal conditions. Complexes 1-3 were structurally characterized by single-crystal X-ray diffraction, powder X-ray diffraction, IR and thermogravimetric analyses (TGA). All of them display a zero-dimensional motif, in which strong intermolecular hydrogen bonding interactions (O-H center dot center dot center dot O/N) and packing interactions (C-H center dot center dot center dot pi and pi center dot center dot center dot pi) make them achieve a three-dimensional supramolecular architecture. The primary catalytic results of these three complexes show that high efficiency for the green synthesis of a variety of 3,4-dihydropyrimidin-2(1H)-ones was observed under solvent free conditions through Biginelli reactions. The present catalytic protocols exhibit advantages such as excellent yield, easy isolation, eco-friendly conditions, and short reaction time. (C) 2016 Published by Elsevier Inc.