Synthesis Of Thermoregulated Chiral N-Heterocyclic Ionic Liquid Catalyst And Application For Asymmetric Synthesis Ofγ-Butyrolactones

According to the designability of ionic liquids in the structures, a series of thiazolum thermoregulated chiral ionic liquids and a series of imidazolium chiral ionic liquids with different N-alkyl (R=CH3、CH(CH3)2、CH2CH2CH2C3、PhCH2) and different anion (X=C1-、BF4-、PF6-、COOCF3-、SO3CF3-) were designed and synthesized. The structures of new compounds were characterized by1H NMR and13C NMR. TG analysis was used for the determination of thermostability of the ionic liquid.The thermoregulated thiazolum chiral ionic liquid catalysts were used for catalyzing the reaction of methyl4-formylbenzoate and cinnamaldehyde. The effects of the N-substituted group、anion、solvent、temperature、time and other factors on the reaction were studied, and the optimum conditions were obtained. Under the optimum conditions, the recycling of the ionic liquid catalyst was studied.The imidazolium chiral ionic liquid catalysts were used for catalyzing the reaction of different substrates for the synthesis of y-butyrolactones. The effects of the N-substituted group、anion、solvent、temperature、time and other factors on the reaction were studied, and the optimum conditions were obtained. Under the optimum conditions, the recycling of the ionic liquid catalyst was studied.For the reaction of methyl4-formylbenzoate and cinnamaldehyde catalyzed by the thiazolium thermoregulated chiral ionic liquids (n=14.6), the optimum reaction conditions were as follows:anion COOCF3-, solvent THF/n-hexane=2/2.5, t=16h, T=30℃, the quantity of catalyst10mol%, and the mole ratio of two reactants1:1.5. Under the optimum reaction conditions, the yield still could reach up to85.3%after6recycles of the catalyst. The ee values of cis-product and trans-product were16.6%and18.9%respectively.For the reaction of trans-cinnamaldehyde with2,2,2-trifluoro-l-phenylethanone catalyzed by the n-butyl imidazolium chiral ionic liquid catalysts, the optimum reaction conditions were as follows:solvent THF, anion Cl-, t=14h, T=35℃, the quantity of catalyst15mol%, and the mole ratio of two reactants1:1. Under the optimum reaction conditions, the yield was92.9%, trans:cis is2:5.1, and ee of cis-product was16.6%. After6recycles of the catalyst, the yield still could reach up to61.5%.For the reaction of trans-cinnamaldehyde with methyl phenylglyoxylate catalyzed by the n-butyl imidazolium chiral ionic liquid catalysts, the optimum reaction conditions were as follows:solvent THF, anion Cl-, t=16h, T=25℃, the quantity of catalyst15mol%, and the mole ratio of two reactants1:1.2. Under the optimum reaction conditions, the yield were56.3%, trans:cis is41/50.For the reaction of2,2,2-trifluroro-l-phenylethanone with methoxycinnamaldeyde catalyzed by the n-butyl imidazolium chiral ionic liquid catalysts, the optimum reaction conditions were as follows:solvent toluene, anion SO3CF3-, t=18h, T=30℃, the quantity of catalyst20mol%, and the mole ratio of two reactants1:1. Under the optimum reaction conditions, the yield was92.4%, and trans:cis is2.3:1. The ee values of cis-product and trans-product were24.5%and25.6%respectively. After5recycles of the catalyst, the yield still could reach up to94.3%.For the reaction of1-(3-chlorophenyl)-2,2,2-trifluoroethan-l-one with trans-cinnamaldehyde catalyzed by the n-butyl imidazolium chiral ionic liquid catalysts, the optimum reaction conditions were as follows:solvent THF, anion Cl-, t=20h, T=25℃, the quantity of catalyst10mol%, and the mole ratio of two reactants1:1. Under the optimum reaction conditions, and trans:cis is1:1. The ee values of cis-product and trans-product were20.9%and25.1%respectively. After5recycles of the catalyst, the yield still could reach up to95.3%.In summary, it is proved that the newly prepared imidazolium chiral ionic liquids and thiazolium thermoregulated chiral ionic liquids can catalyze the annulations of α,β-unsaturated aldehyde with different aromatic aldehydes to stereoselectively synthesize y-butyrolactones. The catalytic reaction has regioselectivity, and the catalyst can also be recycled. It not only provides a new idea in synthesis of y-butyrolactones but also makes a very effective way for chiral ionic liquids catalysis in other stereoselective reactions.