Asymmetric Hydrogenation Of α-Ketoesters Catalyzed By Platinum And Iridium Nanoparticles In The Thermoregulated PEG Biphasic System

PEG4000 stabilized platinum and iridium nanoparticle catalysts were prepared by hydrogen reduction and used as catalysts for the asymmetric hydrogenation of α-Ketoesters(ethyl pyruvate and methyl benzoylformate)in the thermoregulated PEG biphasic system.The Pt,Ir nanoparticle catalysts and chiral modifier(cinchonidine)could be separated and recycled.The Pt nanoparticles were used as catalysts for the asymmetric hydrogenation of ethyl pyruvate.The effects of various conditions on the reaction were investigated.Under the optimized reaction conditions,the reaction could achieve 99% conversion and 64% ee value.The catalyst could be recycled 10 times without evident loss in catalytic activity and ee value.The Pt nanoparticles were used as catalysts for the asymmetric hydrogenation of methyl benzoylformate.The effects of various conditions on the reaction were investigated.Under the optimized reaction conditions,the reaction could achieve 99% conversion and 75% ee value.The catalyst could be recycled 4 times without evident loss in catalytic activity and ee value.The Ir nanoparticles were used as catalysts for the asymmetric hydrogenation of ethyl pyruvate,The effects of various conditions on the reaction were investigated.Under the optimized reaction conditions,the reaction could achieve >99% conversion and 37% ee value.The catalyst could be recycled 3 times without evident loss in catalytic activity and ee value.Asymmetric hydrogenation of ethyl pyruvate catalyzed by the Ir metal,the ee value reached the maximum value reported in literatures.