Ultrasonication-assisted Synthesis of α, β-Unsaturated Compounds Catalyzed by Amino-functionalized FDU-12 Catalyst

Amino-group functionalized FDU-12 material (FDU-12-NH2) was utilized as an efficient and recyclable catalyst for the Knoevenagel condensation to afford alpha, beta-unsaturated compounds. The catalysts were characterized by nitrogen adsorption, X-ray diffraction, Fourier transform infrared spectrophotometer, scanning electron microscopy, transmission electron microscopy and thermogravimetric analysis, which showed that FDU-12-NH2 was successfully prepared using the post-synthesis-grafting method. Compared with the magnetic stirring method, the ultrasound-assisted method could improve the Knoevenagel reaction significantly in this work. In addition, the catalyst exhibited the highest catalytic activity in the mixed solvent of ethanol and water with volume ratio of 3 : 1 due to the solvent effect. Various substrates could convert to their desired products with high yields in short time; what's more, it could be used for four times without significant decrease of the activity. This work reveals that FDU-12-NH2 is a promising heterogeneous catalyst for the synthesis of alpha, beta-unsaturated compounds.