Synthesis and characterization of 2,5-diphenyl-3,4-di(2-pyridyl)cyclopentadienone by thermal dehydration of 2,5-diphenyl-3,4-di(2-pyridyl)cyclopentandiolone in the presence of silica gel

The compound, 2,5-diphenyl-3,4-di(2-pyridyl)cyclopentadienone (2), has been synthesized by thermal dehydration of 2,5-diphenyl-3,4-di(2-pyridyl)cyclopentandiolone (1) over silica gel under N2 atmosphere at 200°C. The product (2), has been characterized by elemental analysis, IR, UV–VIS, and 1H NMR spectroscopy. Thermal dehydration of (1) over silica gel has also been studied by TGA, DTG, and DSC. The effective kinetic and thermodynamic parameters of dehydration have been estimated, and a mechanism of dehydration from Brönsted sites on silica gel has been proposed. Comparative dehydration experiments using γ-Al2O3, ZnO, and NiSO4 proved silica gel to be superior in converting compound (1) to (2).