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

Magnetic solid acid catalysts SO 4 2− /Zr(OH) 4 –Fe 3 O 4 were prepared using magnetic Fe 3 O 4 nanoparticles , ZrOCl 2 ·8H 2 O, and sulfuric acid as starting materials in the calcination temperature range 110–650 °C. The properties of the magnetic solid acid, such as loaded SO 4 2− 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 = NO 2 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.