Design,Preparation And Catalytic Performance Of ?-cyclodextrin Amino-thiourea Derivatives

As one of the hottest researches in the field of supramolecule chemistry,supramolecular catalysis as the closest from the natural enzyme catalysis has been one of the research focuses.Its catalytic effect is mainly achieved through the host-guest interaction.Since the discovery of?-cyclodextrin at the end of the 19th century,the development of?-cyclodextrin-based supramolecular catalysts has been a hot topic for scientists.?-cyclodextrin has the characteristics of economic origin,environmental protection,etc,and after a long period of accumulation,people have accumulated a wealth of experience in its application to the field of catalysis to overcome the defects of its single functional group,so far most are based on cyclodextrins.The supramolecular catalysts are characterized by mild reaction conditions and environmental protection.Therefore,the design and development of a novel supramolecular catalyst based on cyclodextrin have important research value.The thiourea catalysis catalyzed by small molecules is a very mature catalytic system.It has implications for the design and synthesis of supramolecular catalysts.By inspiration from the thiourea catalysis,we designed and synthesized three types of different thioureas(A,B,and C).Molecularly modified?-cyclodextrin host molecules,and its structure was confirmed by ~1H-NMR,HR-MS and other means;16 were new compounds.And we have conducted a preliminary study on the catalytic properties of the synthesized new compounds.Asymmetric Friedel-Crafts alkylation of indol with nitroalkenes and nitrosoaldol reaction of nitrosobenzene with acetophenone have been the hotspots of organic synthesis catalysis.Although they have been reported in small molecule thiourea catalysts.However,the development of green and efficient catalysts is still of great demands.We used the novel supramolecules to study the two reactions to the appeal.Although the catalytic asymmetric F-C alkylation reaction achieved a high yield(80%),its stereoselectivity was low(9.5%);The nitroaldol reaction fails to obtain the target product,and the catalyst structure needs to be optimized later.In addition,three-component reactions of aromatic aldehydes and their analogues with nitroacetonitrile,5,5-dimethyl-1,3-cyclohexanedione catalyzed by?-cyclodextrins(a0-4)modified with different lengths of amino side chains were reported in this paper.Under the catalysis of catalyst a3,10 novel compounds were synthesized in high yield.We confirmed the structure of the new compo unds by means of NMR,HR-MS,IR and using ~1H-NMR to briefly explain its catalytic mechanism.In the synthesis of nitroacetonitrile as a raw material for the reaction,we used a more secure methyl tert-butyl ether as a solvent to optimize the synthesis method of the raw material nitroacetonitrile,and achieved a good yield while improving the safety of the reaction(40%).In summary,a series of cyclodextrin-based thiourea catalysts were designed and synthesized in this work,and their catalytic performances were explored.Three-component reactions catalyzed by aminocyclodextrins with different side chain lengths were investigated and its catalytic mechanism has been studied.The above work provides a reference for the design and synthesis of supramolecular catalysts.