Preparation Of Supported Cbs Catalysts And Their Asymmetric Catalytic Performance

The CBS catalyst can reduce prochiral ketones to chiral secondary alcohols,and has the advantages of high enantioselectivity,high yield,good stability,and high reaction rate.After completion of the reaction,the catalyst can be recovered as a precursor hydrochloride,but the process is cumbersome and the recovery is low.Although related load methods have been reported,there are still difficulties in catalyst recovery and low selectivity in industrial production.In this study,Trans-N-Boc-4-hydroxy-L-prolin-methylester was used as raw material to synthesize styrene-type functional monomers.The polymer microspheres and polyether Pluronic F-127 were used as the carrier materials,respectively.Grafted onto two kinds of carriers respectively,and then the hair microspheroidal CBS catalyst and the novel CBS gel catalyst were prepared by the methyl borate condensation reaction.The two carriersupported CBS catalysts can use heterogeneous catalysis to achieve the rapid separation of the catalysts and apply them to asymmetric reduction of acetophenones to further investigate the catalytic activity and stereoselectivity of the catalysts.The reaction conditions of the supported catalyst were optimized,and the recycling of the supported catalyst was investigated.The hairy particle-supported CBS catalyst catalyzes the asymmetric reduction of acetophenone,when the molar fraction of functional monomer is 60%,the amount of catalyst is 16%,the amount of borane reagent is 1.1%,and the reaction temperature is 30°C,the conversion of acetophenone is 98.5% and the ee value of phenylethanol is 94.3%.At the end of the reaction,the hairy particle-supported CBS catalyst can achieve rapid separation from the product by centrifugation.The selectivity of the multiplexed catalyst can still be more than 93%.The novel CBS gel catalyst catalyzes the asymmetric reduction of acetophenone.When THF is used as the reaction solvent,the molar fraction of functional monomer is 50%,the amount of catalyst is 10%,and the amount of borane reagent is 0.8%.The conversion rate of acetophenone is 98.8% and the ee value of phenylethanol is 95.3%.It basically reaches the level of homogeneous catalytic reaction.Catalyst recycling 5 times,the selectivity can still reach 90%.