Chiral Cr(III)-salen complex embedded over sulfonic acid functionalized mesoporous SBA-15 material as an efficient catalyst for the asymmetric Henry reaction

Abstract

Designing novel catalytic system for efficient synthesis of enantiomerically pure β-hydroxy nitroalkanes is a challenging area of research. Herein, we have designed a chiral heterogeneous catalyst through the successful loading of chiral Cr(III)-salen complex over sulfonic acid functionalized SBA-15 material. The catalyst has been thoroughly characterized by powder XRD, N2 adsorption/desorption, XPS, HR-TEM, CHN, AAS analyses and FT-IR spectroscopy. The reactivity of the catalyst has been examined in the enantioselective Henry reaction, where different substituted aromatic, heteroaromatic as well as aliphatic aldehydes produced corresponding β-hydroxy nitroalkanes with excellent product yields (up to 90%) and enantioselectivities (up to 91%). Moreover, this protocol has also been employed as the key-step to prepare enantiomerically pure drug (R)-(-)-isoproterenol from 3,4-dimethoxybenzaldehyde.