Synthesis of tetrazoles, triazoles, and imidazolines catalyzed by magnetic silica spheres grafted acid

The magnetically separable catalysts are used in the synthesis of N-containing heterocycles, including tetrazoles, triazoles, and imidazolines. The magnetic silica sphere grafted sulfonic acid (MSS-SO₃H) is suitable for the synthesis of 1,2,3-triazole via the cycloaddition of nitroalkene with NaN₃, whereas the zinc-modified silica sphere catalyst (MSS-SO₃Zn) is more suitable for the synthesis of tetrazoles. The MSS-SO₃Zn catalyst also works well for the synthesis of 2-substituted imidazoline via the condensation of nitriles with ethylenediamine. Both of the MSS-SO₃H and MSS-SO₃Zn catalysts can be recovered easily by a magnet, and they can be reused without further tedious activation.