The Application Of Br?nsted Acidic/Basic Ionic Liquids In The Condensatian Reaction

With the rapid development of ionic liquids,traditional ionic liquids have been difficult to meet the practical needs.In recent years,a number of researchers at home and abroad have great interest in development and application of functionalized ionic liquids.Functionalized ionic liquids are designed and prepared for the special purpose,in which functional groups are covalently attached to anion or cation.Br?nsted acidic/basic ionic liquids as two important kinds of functional ionic liquids,which have the high catalytic activity,easily separate from the products and recycling.Several kinds of Br?nsted acidic/basic ionic liquids were synthesized and then their structures were characterized.Br?nsted acidic ionic liquids were used as catalysts for the preparation of biscoumarin and tetrahydrobenzo[b]-pyran derivatives,and Br?nsted basic ionic liquids were used to catalyze the synthesis of benzopyranone derivatives.At first,the catalytic performances of several kinds of Br?nsted acidic/basic ionic liquids were investigated during the catalytic reactions.Secondly,the reaction conditions were optimized by single factor analysis.At last,under the optimum reactions,the feasibility of the recycling of the ionic liquids catalysts without any treatment was verified,and the effect of the mono substituted aromatic aldehydes on the reaction was also discussed.The experimental results show that in the synthesis of biscoumarin derivatives catalyzed by Br?nsted acidic ionic liquids,the reaction between 4-hydroxycoumarin and benzaldehyde was used as model reaction,in which the best catalytic activity of N,N',N'',N'''-tetrapropylidene sulfonic acid hexmethylene tetramine tetrahydrosulfate was used as a catalyst and H₂O was chosen as a green solvent.At 80?,the mass ratio of catalyst to benzaldehyde is 57%,the mole ratio of 4-hydroxycoumarin to benzaldehyde is 2:1,the yield of product can reach 92%.At the same time,the untreated acidic ionic liquids still have high catalytic performance after 6 cycles.The reactivity of 4-substituted aromatic aldehydes with the electro-withdrawing is better.During the synthesis of tetrahydrobenzo[b]-pyran derivatives catalyzed by Br?nsted acidic ionic liquids,the reaction of 5,5-dimethy-1,3-cyclohexanedione,benzaldehyde and malononitrile was a probe reaction.N,N',N'',N'''-tetrapropylidene sulfonic acid hexmethylene tetramine tetrahydrosulfate was used as the best catalyst through the comparison of catalytic properties.Then the optimum reaction conditions was obtained by single factor analysis.It is that reaction temperature is reflux temperature of the solvent,the reaction and recrystallization solvent is 1:1 ethanol aqueous solution,the mass ratio of the catalyst to benzaldehyde is 36%and ratio of 5,5-dimethy-1,3-cyclohexanedione,benzaldehyde and malononitrile is 1:1:1.The acidic ionic liquid catalyst without any treatment can be reused for 6 times,and its catalytic activity has not been significantly reduced.In addition,the reaction activity of 5,5-dimethy-1,3-cyclohexanedione is higher than that of 1,3-cyclohexanedione,and the reaction yield of mono substituted aromatic aldehydes with substituent group is para-position and electron absorbing group is higher than that of other types of mono substituted aromatic aldehydes.In the synthesis of benzopyranone derivatives with 4-hydroxycoumarin,mono substituted aromatic aldehydes and malonitrile catalyzed by Br?nsted acidic ionic liquids,the reaction of 4-hydroxycoumarin,benzaldehyde and malonitrile in which the best catalytic activity,choline hydroxide and ethanol was acted as a catalyst and solvent respectively.The highest yield of product was obtained in the optimum reaction condition where reaction temperature was 70?,the mass ratio of the catalyst to benzaldehyde was 24%and the mole ratio of 4-hydroxycoumarin,benzaldehyde and malonitrile was 1:1:1.In addition,the catalyst,choline hydroxide recirculated with solvent showed high catalytic activity after 7 cycles.Para-monosubstituted aromatic aldehydes containing electron-absorbing groups were more beneficial to the catalytic reaction.