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Novel MgO–SnO2 Solid Superbase as a High-Efficiency Catalyst for One-Pot Solvent-Free Synthesis of Polyfunctionalized 4H-pyran Derivatives

Zhang Shu-Guo,Yin Shuang-Feng,Wei Yu-Dan,Luo Sheng-Lian,Au Chak-Tong

Abstract We report for the first time the hydrothermal synthesis of MgO–SnO 2 solid superbase using P123 as template. The basicity of the materials was determined by two approaches of Hammett indicators method and temperature-programmed desorption using CO 2 as adsorbate (CO 2 -TPD). It was found that Mg/Sn molar ratio has an effect on MgO–SnO 2 basicity, and superbasicity was observed only at Mg/Sn molar ratio of 1. With variation of Mg/Sn molar ratio, superbase strength ( H - ) was in the 26.5–33.0 range, showing superbasic value up to 0.939 mmol/g. The structure and texture of the as-prepared materials were studied by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and N 2 physio-adsorption methods. We detected particles of spherical morphology having diameter of ca . 150 nm. N 2 adsorption–desorption results suggested that the materials are of mesoporous structure, having specific surface area of 115.2 m 2 /g and average pore diameter of 6 nm. The superbase was found to exhibit excellent catalytic activity towards the one - pot synthesis of polyfunctionalized 4 H -pyrans through the condensation of aldehydes, malononitrile, and an active methylene compound. Its excellent catalytic efficiency is related to its superbasicity of the MgO–SnO 2 . The results provide a new route for the design and preparation of composite oxide superbases. Furthermore, the solid superbases will facilitate a strategy for high-efficiency synthesis of polyfunctionalized 4 H -pyrans. Graphical Abstract Novel MgO–SnO 2 solid superbase was prepared using P123 as template. Its superbase strength was in the 26.5–33.0 range, showing superbasic sites up to 0.939 mmol/g. The material is of mesoporous structure,(having specific surface area of 115.2 m 2 /g and average pore diameter of 6 nm. It was found to exhibit excellent catalytic activity towards the one-pot solvent-free synthesis of polyfunctionalized 4 H -pyrans through the condensation of aldehydes, malononitrile, and an active methylene compound. The results provide a new route for the design and preparation of composite oxide superbases.