Catalysis Letters, Vol.142, No.5, 608-614, 2012
Novel MgO-SnO2 Solid Superbase as a High-Efficiency Catalyst for One-Pot Solvent-Free Synthesis of Polyfunctionalized 4H-pyran Derivatives
We report for the first time the hydrothermal synthesis of MgO-SnO2 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 CO2 as adsorbate (CO2-TPD). It was found that Mg/Sn molar ratio has an effect on MgO-SnO2 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 4H-pyrans through the condensation of aldehydes, malononitrile, and an active methylene compound. Its excellent catalytic efficiency is related to its superbasicity of the MgO-SnO2. 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 4H-pyrans. Novel MgO-SnO2 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 4H-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.