Chiral lanthanum–lithium–binaphthol complex covalently bonded to silica and MCM-41 for enantioselective nitroaldol (Henry) reaction

Abstract

A chiral BINOL ligand covalently anchored on silica and mesoporous MCM-41 was synthesized and characterized by powder XRD, FT-IR, N2 adsorption–desorption measurements, TGA and elemental analysis. These anchored ligands were then used to prepare La–Li–BINOL–silica 1a and La–Li–BINOL–MCM-41 1b complexes. The immobilized catalysts having lanthanum content around 0.12–0.18 mmol/g were tested as enantioselective catalyst for Henry reaction and ee 55–84% were found which were comparable to its homogeneous counterpart. The solid catalysts can be reused by simple filtration and recycled several times without much loss in performance.