Nano-sized NiLa2O4 spinel–NaBH4-mediated reduction of imines to secondary amines

Nano-sized NiLa2O4 spinel was produced by thermal decomposition of Ni–La compounds via a sol-gel method. The well-crystallized spinel structure was formed after calcination at 750 °C. The physicochemical properties of the spinel were investigated using differential thermal analysis, X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and particle size distribution analysis. The results show that the nanoparticles have regular shapes with well-defined crystal faces and consist of uniform quasi-spherical crystallites of average size 40 nm. The refined unit cell parameters are a = 3.861205 Å and c = 12.6793 Å. This new nano-sized NiLa2O4 spinel is an efficient heterogeneous catalyst for the selective conversion of imines to the corresponding secondary amines in the presence of NaBH4 as a reducing agent, in good to excellent yields. All the reactions were completely chemoselective at room temperature and had relatively short reaction times. Secondary amines with different aryl groups, including those bearing electron-withdrawing or electron-donating groups, were obtained under the optimum reaction conditions. The catalyst was readily recovered and was recycled four times with no significant loss of catalytic activity.

Graphical AbstractThe well-crystallized nano-sized NiLa2O4 spinel structure is formed and applies as an efficient heterogeneous catalyst for selective conversion of imines to the corresponding secondary amines in the presence of NaBH4 as reducing agent.Figure optionsDownload as PowerPoint slide