Study On The Coupling Reaction Of CO₂ And Epoxides Catalyzed By Bifunctional Catalysts

The coupling reaction of carbon dioxide and epoxides was well reviewed.And the orientation of developing efficient,simple and recyclable catalyst systems was determined.Meanwhile,new chiral catalyst systems based on a bifunctional catalyst in one molecule were synthesized and developed for the catalytic kinetic resolution of racemic epoxides with carbon dioxide to generate chiral cyclic carbonates.The contents are as follows:1.We have synthesized several quaternary onium tribromides(3 new compounds) based on the traditional organic salts and firstly applied to catalyze the coupling reaction of carbon dioxide and epoxides.Phenyltrimethyl ammonium tribromide (PTAT)was the best catalyst,which combined with the metal compounds SalenCoX and developed to catalyze the coupling reaction of carbon dioxide and epoxides generating relevant cyclic carbonates including chiral propylene carbonate under mild conditions.The chiral propylene carbonate obtained 44.7%ee at 0℃.2.A simple catalyst system of ZnBr₂-quaternary onium tribromide salt has been developed for the coupling reaction of carbon dioxide and epoxides.The effects of metal salts and reaction conditions and the recyclability of the catalysts were investigated.The results demonstrated that the coupling reaction of CO₂ and epoxides to form cyclic carbonates with high yield proceeds very effectively at 413K under 1.0MPa by using ZnBr₂ in conjunction with the PTAT co-catalyst without solvent.The catalyst could be recycled several times,which is of great prospect in industrial applications.3.The coupling reaction of epoxides with carbon dioxide catalyzed by SalenRu(â…¡)(PPh₃)₂ or SalenRu(â…¢)X was studied.Reaction conditions were optimized. The new catalyst system of Salen-Ru(â…¡)(PPh₃)₂/PTAT promoted by ethyl diazoacetate(EDA)is able to catalyzed the coupling reaction,and the catalyst system of Salen-Ru(â…¢)(PPh₃)/PTAT is very efficient to catalyze synthesis of cyclic carbonate from various epoxides and carbon dioxide at 343K. 4.New chiral catalyst systems based on a bifunctional catalyst in one molecule were synthesized and developed for the catalytic kinetic resolution of racemic epoxides with carbon dioxide to generate chiral cyclic carbonates with high yield and moderate enantioselectivity.The effect of counterion,anion and cation of quaternary salt and metal center were investigated.These new catalysts have a great advantage being recycled easily at least 5 times without obviously lose of their activity and enantioselectivity.5.In the chiral catalyst system SalenCoX/tetrabutylammonium bromide(TBAB), we investigated the effect of counterion and different chiral co-catalysts to catalyst activity and resolution,which based on the amino acid derivatives.When addingβCD, the enantioselectivity was increased obviously.Under the optimized conditions,we investigated the catalyst system of SalenCoX/chiral co-catalyst/βCD to resolution propylene oxide with carbon dioxide.