Synthesis Of γ-butyrolactones Catalyzed By Thermoregulated Azoles Chiral Ionic Liquids

According to the designability of ionic liquids in the structures, a series ofimidazolium and triazolium chiral ionic liquids were synthesized and used forcatalyzing the reaction of synthesis of γ-butyrolactones.The prepared imidazolium chiral ionic liquids catalysts were used for catalyzingthe reaction of4-methoxy cinnamic aldehyde and p-formylbenzoate. The optimumconditions were as follows: acetonitrile as solvent, the mole ratio of two reactants1:2,DBU as the alkaline reagent, the quantity of catalyst20mol%, t=12h, T=30℃. Underthe optimum reaction condition, the yield was66.4%. The ratio of cis: trans productwas3.7:1, and the ee values of cis-product and trans-product were66%and54%,respectively. After three times recycles of the catalyst, the yield still could reach up to61%.For the reaction of4-methoxy cinnamic aldehyde and p-formylbenzoate catalyzedby the catalyst of the imidazolium chiral ionic liquids with two chiral centres, theoptimum reaction conditions were as follows: the mole ratio of two reactants1:1.5,toluene as solvent, the quantity of catalyst10mol%, t=16h and T=30℃. Under theoptimum reaction condition, the conversion of4-methoxy cinnamic aldehyde was93%,and the yield was90%. The ee values of cis-product and trans-product were5%and10%, respectively. After three times recycles of the catalyst, the yield was63%.For the reaction of4-methoxy cinnamic aldehyde and p-formylbenzoate catalyzedby the catalyst of the thermoregulated triazolium chiral ionic liquids, the optimumreaction conditions were as follows: the mole ratio of two reactants1:2, THF assolvent, t=12h, T=30℃, anion Cl-, the quantity of catalyst15mol%. Under theoptimum reaction condition, the conversion of4-methoxy cinnamic aldehyde was91%,and the yield was86%. The ratio of cis: trans product was4.3:1. The ee values of cis-product and trans-product were61%and67%, respectively. After three timesrecycles of the catalyst in the mixture of n-hexane and dichloromethane, the yield was65%.For the reaction of4-methoxy cinnamic aldehyde and,,,-trifluoro-acetophenone catalyzed by the catalyst of the thermoregulated triazoliumchiral ionic liquids, the optimum reaction conditions were as follows: the mole ratio oftwo reactants1:2, acetonitrile as solvent, t=8h, T=30℃, anion Cl-and the quantity ofcatalyst15mol%. Under the optimum reaction condition, the conversion of4-methoxycinnamic aldehyde was94%, and the yield was85%. The ratio of cis: trans productwas2.4:1. The ee values of cis-product and trans-product were18.8%and9.4%,respectively. After four times recycles of the catalyst in the mixture of n-hexane anddichloromethane, the yield was78%.For the reaction of4-methoxy cinnamic aldehyde4-chloro-,,,-trifluoro-acetophenone catalyzed by the catalyst of the thermoregulated triazoliumchiral ionic liquids, the optimum reaction conditions were as follows: the mole ratio oftwo reactants1:2, THF as solvent, t=8h, T=30℃, anion Cl-and the quantity of catalyst15mol%. Under the optimum reaction condition, the conversion of4-methoxycinnamic aldehyde was94%, and the yield was89%. The ratio of cis: trans productwas3.2:1, the ee values of cis-product and trans-product were36%and20%,respectively. After three times recycles of the catalyst in the mixture of n-hexane anddichloromethane, the yield was61%.For the reaction of4-chloro cinnamic aldehyde and,,,-trifluoro-acetophenonecatalyzed by the catalyst of the thermoregulated triazolium chiral ionic liquids, theoptimum reaction conditions were as follows: the mole ratio of two reactants1:3, THFas solvent, t=12h, T=30℃, anion Cl-and the quantity of catalyst15mol%. Under theoptimum reaction condition, the conversion of4-chloro cinnamic aldehyde was89%,and the yield was76%. The ratio of cis: trans product was2.2:1. The ee values ofcis-product and trans-product were12%and11%, respectively. After four timesrecycles of the catalyst in the mixture of n-hexane and dichloromethane, the yield was52%.For the reaction of4-fluoride cinnamic aldehyde and,,,-trifluoro-acetophenone catalyzed by the catalyst of the thermoregulated triazolium chiral ionic liquids, the optimum reaction conditions were as follows: the mole ratio oftwo reactants1:2, THF as solvent, t=12h, T=30℃, anion Cl-and the quantity ofcatalyst15mol%. Under the optimum reaction condition, the conversion of4-fluoridecinnamic aldehyde was90%, and the yield was82%. The ratio of cis: trans productwas2.5:1. The ee values of cis-product and trans-product were2.3%and3%,respectively. After four times recycles of the catalyst in the mixture of n-hexane anddichloromethane, the yield was55%.For the reaction of trans-cinnamic aldehyde cinnamic and,,,-trifluoro-acetophenone catalyzed by the catalyst of the thermoregulated triazoliumchiral ionic liquids, the optimum reaction conditions were as follows: the mole ratio oftwo reactants1:2, acetonitrile as solvent, t=12h, T=30℃, anion Cl-and the quantity ofcatalyst15mol%. Under the optimum reaction condition, the yield was86%. The ratioof cis: trans product was1.9:1. The ee values of cis-product and trans-product were10%and25%, respectively. After three times recycles of the catalyst in the mixture ofn-hexane and dichloromethane, the yield was50%.In summary, it is proved that the newly prepared azoles chiral thermoregulatedionic liquids can catalyze the annulations of,β-unsaturated aldehyde with differentaromatic aldehydes to stereoselectively synthesize γ-butyrolactones. The new systemhas the feature of―homogeneoug at higher temperature, heterogeneous at lowertemperature‖, and the recycling of the ionic liquid catalyst can be easily achieved. Itprovides a new idea in synthesis of γ-butyrolactones.