Quinine Thiourea Immobilized on SBA‐15 as an Efficient Recyclable Catalyst for Asymmetric Strecker Reaction of Isatin N‐protected Ketimines

Abstract

AbstractQuinine thiourea organo‐catalyst immobilized on the SBA‐15 mesoporous material was synthesized by the post‐grafting method. First, the organothiol group was grafted over the SBA‐15 surface and which was anchored with quinine thiourea via. radical polymerization method. The synthesized catalyst was characterized by various physicochemical methods. The 13CP MAS solid‐state NMR confirms the successful grafting of quinine thiourea over the surface of SBA‐15. Thermogravimetric weight loss analysis confirms the successful anchoring of organo‐catalyst. The synthesized organo‐catalyst was used as heterogeneous catalyst for asymmetric Strecker reaction of N‐Boc isatin derived ketimines. The heterogeneous catalyst worked efficiently to give α‐amino nitriles in good yields and high enantiomeric excess up to 93% with 90% conversion in 85 h at –10 °C temperature. Furthermore, the catalyst was successfully reused up to five times without loss in yield and enantioselectivity of the product.