The Synthesis Of Cyclic Carbonates/Oxazolidinones From Epoxides And CO₂ Catalyzed By Ionic Liquids

CO₂ is a main greenhouse gas that damages environment and ecosystem,but also an abundant,nontoxic,nonflammable,easily available and renewable carbon source.Due to the shortage of the global resources and energy,the conversion of CO₂ to high value-added chemical products becomes very important in the field of green chemistry.Epoxide is an important basic chemical raw material and widely used in the fields of fine chemical industry,petrochemical industry and organic synthesis.This dissertation focuses on the synthesis of cyclic carbonates and 2-oxazolidinones from epoxides and CO₂ catalyzed by ionic liquids.The major contents and results of this work are summarized:?1?The synthesis of cyclic carbonates from epoxides and CO₂ catalyzed by phenolic hydroxyl-functionalized imidazolium ionic liquidsTen kinds of novel phenolic hydroxyl-functionalized imidazolium ionic liquids were designed,synthesized and then applied to catalyze the reactions of epoxides and CO₂.A detailed investigation was carried out on the relationship between catalytic activities and ionic liquid structures including phenolic hydroxyl,the C-2 proton of imidazolium ring?C2-H?and the anion.The results showed the phenolic hydroxyl-functionalized imidazolium ionic liquids containing both phenolic hydroxyl and C2-H were highly efficient catalysts.The effects of temperature,time,CO₂ pressure and amount of catalyst on the reaction of epichlorohydrin and CO₂ catalyzed by 3-?3-hydroxy-benzyl?-1-butyl-imidazolium bromide were investigated in detail.Under the optimal reaction conditions,various epoxides were tranformed to the corresponding cyclic carbonates in 75-97%of isolated yields.NMR titration and DFT calculations showed a synergetic effect,which C2-H and phenolic hydroxyl cooperatively activated epoxides by hydrogen bonds,improved the catalytic performance of hydroxyl-functionalized ionic liquids in the reaction of epoxides and CO₂.?2?Synthesis of functional cyclic carbonates by one-pot reactions of epibromohydrin,CO₂ and phenols/thiophenols/carboxylic acids catalyzed by ionic liquidsA novel procedure for synthesis of functional cyclic carbonates by one-pot reactions of epibromohydrin,CO₂ and phenols/thiophenols/carboxylic acids in the presence of catalytic amount of ionic liquids was developed.The effects of time,temperature,CO₂ pressure and amount of catalyst on the reaction of epibromohydrin,CO₂ and phenol catalyzed by 3-?3-hydroxy-benzyl?-1-butyl-imidazolium bromide were investigated.Under the optimal reaction conditions,3-?3-hydroxy-benzyl?-1-butyl-imidazolium bromide exhibited efficient catalytic activity comparing with other ionic liquids.Meanwhile,various ether functionalized cyclic carbonates were obtained in yields of 41-85%.The studies of model reaction showed that the reaction contained a range of process,such as the formation of oxy-anion species by ring-opening of epibromohydrin,the generation of 1-bromo-3-phenoxy-2-propanol by the reaction of epibromohydrin with phenol,and the proton exchange between oxy-anion species and halohydrin.In addition,thioether and ester functionalized cyclic carbonates were also successfully synthesiezed by the reactions of epibromohydrin,CO₂ and thiophenols/carboxylic acids catalyzed by phenolic hydroxyl-functionalized ionic liquids,the yields of products reached to 50-75%and 89-94%respectively.?3?The synthesis of 2-oxazolidinones from propylene carbonate/epoxides and urea catalyzed by ionic liquids.New procedure for the synthesis of 5-methyl-2-oxazolidinone from propylene carbonate and urea catalyzed by imidazolium ionic liquids was developed.The effect of different ionic liquids?BmimOAc,BmimCl,BmimBr and BmimBF4?on the reaction of propylene carbonate and urea was studied.The results showed BmimCl exhibited higher catalytic activity than other ionic liquids.The influence of reaction parameters including time,temperature,amount of catalyst and molar ratio of urea and propylene carbonate on the reaction of propylene carbonate and urea was investigated using the most active BmimCl.Under the optimal reaction conditions,the yield of 5-methyl-2-oxazolidinone reached to 98%.Because the carbonyl in propylene carbonate which was usually syntheszied by the reaction of epoxide with CO₂ was converted into CO₂ and released,a new approach for the synthesis of 2-oxazolidinones by the reactions of epoxides and urea was developed.The reaction of 2-phenoxymethyl-oxirane with urea was chosen as a model reaction.The results showed this reaction could be achieved under catalyst-free condition.Under the condition of the catalyst-free,the influence of reaction time,temperature,molar ratio of 2-phenoxymethyl-oxirane with urea on the model reaction was investigated.Under the optimal reaction conditions,the isolated yields of 2-oxazolidinones reached to 80-95%.1-Amino-3-phenoxy-2-propanol and?2-hydroxy-3-phenoxy-propyl?-urea,which were isolated from the reaction mixture,were assumed as important intermediates in the formation of 2-oxazolidinones.As CO₂ was the raw material for the synthesis of propylene carbonate and urea,the above synthetic routes could be considered indirect fixation of CO₂.