Synthesis of phosphoric acid supported on magnetic core–shell nanoparticles: a novel recyclable heterogeneous catalyst for Kabachnik–Fields reaction in water

Abstract

In this paper, supported phosphoric acid on silica coated magnetic nanoparticles (γ-Fe₂O₃@SiO₂-PA) was synthesized as a new solid acid via the reaction of chloro-functionalized γ-Fe₂O₃@SiO₂ with triethyl phosphite followed by hydrolysis. The synthesized γ-Fe₂O₃@SiO₂-PA was characterized by SEM, HRTEM, BET, FT-IR, TGA, ICP and VSM. It was used as a magnetically recyclable heterogeneous catalyst for the efficient one-pot synthesis of α-aminophosphonates through Kabachnik–Fields reaction in water. Good to high yields of α-aminophosphonates showed that γ-Fe₂O₃@SiO₂-PA had strong and sufficient acidic sites, which were responsible for its catalytic performance. More importantly, the catalyst was easily isolated from the reaction mixture by a magnetic bar and reused at least five times without significant degradation in the activity.