Levulinate-intercalated LDH: A potential heterogeneous organocatalyst for the green epoxidation of α,β-unsaturated esters

Abstract

Green efficient organocatalytic heterogeneous epoxidation of trans-methylcinnamate was achieved on LDH-intercalated levulinate using H2O2/acetonitrile as oxidant. The layered double hydroxide (LDH) was prepared by co-precipitation starting from an aqueous solution of Mg(NO3)2∙6H2O and Al(NO3)3∙9H2O. The preparation of the LDH hybrid organocatalyst was carried out following four different routes: i) step-by-step ion exchange in air (LEV@LDH-air); ii) one charge ion-exchange in N2 atmosphere (LEV@LDH-N2); iii) direct synthesis by co-precipitation (LEV@LDH-pp); and the iv) reconstruction method (LEV@LDH-mem). The synthesized catalysts were characterized using different techniques such as adsorption-desorption isotherms of nitrogen at −196°C, powder X-ray diffraction (XRD), differential thermal analysis and thermogravimetric analysis (TG-DTA), and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy techniques. The levulinate was successfully intercalated by ion exchange and co-precipitation. In the investigated series the LEV@LDH-pp catalyst showed the highest performances at 40°C and 24h (Ccinnamate=21.4%, Sglycidate=100%).