Chiral salen - Ni (II) based spherical porous silica as platform for asymmetric transfer hydrogenation reaction and synthesis of potent drug intermediate montekulast

Abstract

Heterogeneous catalyst has an edge over homogeneous systems in terms of recyclability, activity, stability and recovery. Silica has evolved as a good support material in heterogeneous systems due to its stability and ability to get modified as per the end application. Herein, we report a novel chiral Ni-Schiff base derived catalyst and its immobilization into mesoporous silica which was synthesized by post-grafting process. The chiral catalyst demonstrated remarkably high catalytic activity, enantioselectivity (up to 99 % enantiomers excess) for heterogeneous asymmetric transfer hydrogenation of various ketones. The developed catalyst was characterized by Ultraviolet-visible spectroscopy (UV–vis), Fourier-Transform Infrared spectroscopy (FT-IR), X-ray Powder Diffraction (XRD), Brunauer-Emmett-Teller (BET isotherm), Scanning Electron Microscopy – Energy Dispersive X-ray Spectroscopy (SEM-EDX), High Resolution – Transmission Electron Microscopy (HR-TEM), Vibrating Sample Magnetometer (VSM), X-ray Photoelectron Spectroscopy (XPS) and elemental analysis. The catalyst could be recovered and reused for multiple consecutive runs without losing the enantioselectivity. The chiral catalyst was used in asymmetric transfer hydrogenation reaction for synthesizing enantiomerically pure drug intermediate Montekulast.