Aqueous asymmetric aldol reaction catalyzed by nanomagnetic solid acid SO42−/Zr(OH)4–Fe3O4

Magnetic solid acid catalysts SO42−/Zr(OH)4–Fe3O4 were prepared using magnetic Fe3O4 nanoparticles, ZrOCl2·8H2O, and sulfuric acid as starting materials in the calcination temperature range 110–650 °C. The properties of the magnetic solid acid, such as loaded SO42− content, acid distribution, surface morphology, and porous structure, were characterized. In the aqueous asymmetric aldol reaction of various benzaldehydes with strong electron-withdrawing groups (R = NO2 and CN), good to excellent catalytic performance (83%–100% yield, 86.0%–95.6% ee anti, and anti/syn = 88–96/12–4) was achieved. These nanomagnetic solid acids can be quantitatively recycled from the reaction mixture using an external magnet and reused five times without significant loss of catalytic activity.

Graphical AbstractSulfated zirconium hydroxide loaded on nano-Fe3O4 was prepared and applied to the aqueous asymmetric aldol reaction with good to excellent catalytic performance (83%–100% yield, 86.0%–95.6% ee anti, and anti/syn = 88–96/12–4).Figure optionsDownload full-size imageDownload as PowerPoint slide