Palygorskite-Mn(II): An efficient and recyclable heterogeneous catalyst for the synthesis of quinolines

A green and high efficient heterogeneous catalysts, palygorskite supported NNN-pincer manganese complexes, were prepared. The prepared catalyst were characterized by scanning transmission electron microscopy (SEM), Fourier infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA) and Brunauer-Emmet-Teller (BET). The results showed that the catalyst were successfully prepared and the structure of palygorskite was still retained. The catalyst displayed outstanding activity for the reaction of 2-aminobenzyl alcohol and secondary alcohols without additional additives, and the corresponding quinolines were obtained in good to excellent yields with a wide scope of substrate tolerance. More importantly, the novel and stable catalysts could be recycled five consecutive times with a little decrease of the catalytic activity. It provides a new strategy for the design heterogeneous catalysts based on the natural clay mineral.