Synthesis Of Proline/Threonine Functionalized Polymers Catalysts And Their Catalytic Properties For Asymmetric Reaction

In recent years,organic small molecule catalysis has been paid much attention in the field of asymmetric synthesis.The small molecules such as amino acids represented by L-proline,urea and thiourea and cinchona alkaloids have been developed rapidly.Compared with the traditional transition metal catalysis and enzyme catalysis,organic small molecule catalysis has many advantages such as high activity,high stereoselectivity and non-toxic environmental protection,and has been widely used in a series of asymmetric synthesis.But the organic small molecule catalyst is still exposed to the amount of large,easy recovery and other shortcomings.In order to overcome these shortcomings,researchers pay attention to the polymer loading of organic small molecule.Supported catalysts exhibit superior advantages over organic small molecules,such as easy recovery of catalysts,relatively simple experimental operations,and green environmental protection.However,due to the previous load-type catalyst is usually through a macromolecule carrier directly grafted chiral organic small molecule reaction to complete the catalyst load.This kind of macromolecule functional direct load method has the advantages of simple operation and mild reaction condition.However,it is not easy to control the grafting rate of the catalyst due to the winding and curling structure of the polymer carrier itself.Therefore,it is a very important research topic to explore the new loading method of organic small molecule catalyst and to increase the loading of effective groups in the catalyst.In this paper,it is proposed to modify the chiral organic small molecule to make it polymerizable.Then,several functionalized proline/threonine polymer catalysts were synthesized by polymerization reaction and used to catalyze the asymmetric Aldol reaction and Mannich reaction.1.L-proline and 4-aminostyrene to synthesize the functionalized L-prolinamide-styrene monomer,which is obtained by simple polymerization to obtain functional L-proline homopolymers and A crosslinked copolymer of 1,4-divinylbenzene?DVB?was added.These polymers were used as a heterogeneous catalyst to catalyze the asymmetric Aldol reaction to yield an Aldol reaction product having a yield of 96%,a dr value of 8:92 and an ee value of up to 96%.The reusability of the catalyst was investigated in a petroleum ether/H₂O mixed solvent?volume ratio=92.5:7.5?.The results show that both catalysts have a certain repeatability.2.Four functionalized L-threonine polymers were synthesized and used to catalyze the asymmetric Aldol reaction and Mannich reaction.The catalytic reaction conditions and the reusability of the catalyst were discussed.The results showed that the yield of 81%,the dr value of 28:72 and the ee value of 86%of Aldol were obtained as the reaction solvent,15 mol%of the catalyst and 10 equivalents of cyclohexanone in the presence of trace water?500?L?reaction product.When the strong polarity of NMP as the reaction solvent,can be obtained 70%yield,dr value of 32:68 and ee value of up to 74%of the Mannich reaction products.The catalyst can be recovered by centrifugal precipitation and can be used four times and three times,respectively.3.A simple functionalized O-tert-butyl-L-threonine homopolymer was prepared by simple polymerization.In order to improve the catalytic performance and reusability of the catalyst,the crosslinking agent DVB was added to the monomer,and three crosslinked copolymers were prepared.Followed by catalytic studies for asymmetric Aldol reactions and Mannich reactions.The yield of the relevant Aldol reaction product was 90%,the dr value was 21:79 and the ee value was 94%,the yield of the relevant Mannich reaction product was 71%,the dr value was 21:79 and the ee value was 69%.And the catalyst has a certain recovery performance in both asymmetric reactions.