Design Of Small Molecule Catalytic Systems Based On Proline And Tert–leucine And Study Of Catalyst Recovery Performance

In the catalytic field of chiral organic small molecule,proline has attracted the attention of the public because of its simple structure,widespread presence in nature,easy availability and chirality,and tert-leucine has a significant role in the asymmetric catalytic reaction due to the large steric hindrance of the t-butyl group.Both proline and tert-leucine have the functions of Br?nsted acid?Lewis acid?and Lewis base?Br?nsted base?,so that they exhibit excellent chiral catalytic performance for many different types of asymmetric catalytic reactions.Continuous research on chiral catalysis and based on the development strategy of green chemistry,designing new catalytic system that can be reused multiple times are receiving more and more attention.But so far,there are still few recyclable chiral catalysts that are truly superior in performance,so that it is important to build a more efficient catalyst recovery system.In this paper,based on the design of novel chiral small molecule catalysts with proline and tert-leucine as skeletons,and investigation of their catalytic performance,the catalysts'recovery process was studied in several aspects and a number of valuable results had been achieved.And they provided a new way that solved the problem of catalyst recovery in small molecule catalysis.?1?We prepared four small molecule organocatalysts based on o-phenylenediamine.And they were applied to the asymmetric Aldol reaction of aromatic aldehydes and ketones.Catalyst 2-3d with adamantyl group being employed in the asymmetrical reactions provided good yield and high stereoselectivity in brine,substrates scope were observed with 98%yield,>99:1 dr value and 99%ee value.?-CD-modified Poly?AN-MA-?-CD?was synthesized,and then naofibrous film was prepared by electrospinning.In the asymmetric Aldol reaction of m-nitrobenzaldehyde and cyclohexanone catalyzed by catalyst 2-3d in a homogeneous system.After the completion of the reaction,the catalyst 2-3d was assembled on the surface of the Poly?AN-MA-?-CD?nanofiber via the supramolecular host-guest recognition of?-CD and adamantane.And the catalyst was filtered and recovered before being separated from the carrier by the disassembly and recycled.The homogeneous catalysis and heterogeneous recovery of small molecule catalysts were realized.The catalyst could be reused for up to five times with providing good yields and high stereoselectivities.?2?A series of new 4-adamantane?phenyl?amido-L-prolinamide catalysts were designed and synthesized from trans-4-hydroxy-L-proline,and were investigated in the asymmetric Aldol reaction of aromatic aldehydes and ketones.Catalyst 3-7e with strong electron withdrawing group on the N-aryl group exhibited a good catalytic effect.When C₄ of 4-OH-L-prolinamide was replaced by adamantane with big steric hindrance,the higher stereoselectivity was provided with yield of up to 98%,dr value of>99:1,and ee value of up to 99%.The?-cyclodextrin with a moderately sized cavity can be assembled with the reaction product and separated from the reaction system,and cannot form an assembly with the catalyst.Through the supramolecular host-guest recognition,the Aldol products were successfully separated from the reaction system while the catalyst being remainined in the reaction was reused.The catalyst could be reused for up to five times without exhiting signicant change in stereoselectivity.?3?4-adamantanylamino-L-prolinamide catalysts were studied in the asymmetric Aldol reaction of isatin derivatives and acetone.Catalyst 4-1d exhibited excellent catalytic performance,and when acetone was used as a solvent,a yield of up to 98%and an ee value of up to 97%were obtained.Prolinamide-modified Poly-C1 was synthesized by covalent bond linking,and then the naofibrous film was prepared by electrospinning.The fiber membrane exhibited a certain catalytic effect in the asymmetric Aldol reaction of lsatin and acetone,and the catalyst was recovered by simple filtration and can be recycled four times.?4?Four bifunctional thiourea catalysts were synthesized by L-tert-leucine,and their applications in the asymmetric Mannich reaction of the lsatin derivative ketimines with?-diketone were investigated.Broad substrates scope was observed and the catalyst 5-6b offered a good catalytic result with a yield of up to 98%and an ee value of 99%.In addition,the naofibrous film of Poly-C2 were prepared by L-tert-leucine derivative and applied to the asymmetric Mannich reaction of the lsatin derivative ketimines with?-diketone,but racemic Mannich product was obtained.