An efficient and recyclable acid–base bifunctional core–shell nano-catalyst for the one-pot deacetalization–Knoevenagel tandem reaction†
A novel magnetic nanoparticle supported acid–base bifunctional catalyst was synthesized by anchoring [3-(2-aminoethyl)aminopropyl]triethoxysilane and sulfonic acid successively onto the surface of silica-coated Fe3O4 nanoparticles. The as-prepared nanoparticle catalyst was used as a “quasi-homogeneous” and recyclable catalyst for the one-pot deacetalization–Knoevenagel tandem reaction of benzaldehyde dimethylacetals and malononitrile. It showed high catalytic activity because the reaction proceeded smoothly and afforded benzylidenemalononitriles in excellent yields. Besides, it showed synergistic effect and facilitated the mass transfer process during the tandem reaction because the two catalytic moieties were connected together on the same MNP. Moreover, the catalyst can be readily recovered under an external magnetic field and reused without any significant loss of the catalytic activity after six runs.