BmimOAc/DBU Catalyzed The Reaction Of Ethylene Trithiocarbonate And Active Methylene Compounds To Synthesize Sulfur-containing Heterocyclic Compounds

For their special physical and chemical properties ionic liquids attracted more attentions during recent decades. Ionic liquids can efficiently catalyze various reactions, such as alkylation reaction, acylation reaction and Knoevenagel reaction. 1,3-Dithiolane derivatives as a sulfur-containing heterocyclic compounds have many applications in the field of medicine, agrochemicals as well as organic synthesis. Besides their application to diminish inflammation, they also have been used in the herbicides. Therefore, the synthesis of sulfur-containing heterocyclic compounds is very significant and has attracted widespread attentions during the past few decades. Conventionally,1,3-dithiolane derivatives are mostly synthesized using carbon disulfide and dibromoethane as raw materials and inorganic strong bases or heavy metal salts as the catalysts to promote the reaction, these methods were considered to be very toxic and non-environmentally benign. According to our previous work about ionic liquids and sulfur-containing heterocyclic compounds, we found that ionic liquids can effectively catalyze synthesis of such compounds. Herein, we try to use ionic liquids as catalysts and ethylene trithiocarbonate as raw material to synthesis 1, 3-dithiolane derivatives.In the first part of this dissertation a series of organic bases were used to catalyze the reactions of ethylene trithiocarbonate and active methylene compounds to synthesize 1,3-dithiolane derivatives. The reaction of ethylene trithiocarbonate and ethyl cyanoacetate was chosen as the model reaction. Reaction conditions such as type of catalysts, reaction time, reaction temperature, amount of catalyst and the mole ratio of reactants were investigated. The results suggested that DBU was the best catalyst among the different organic bases and the best amount of DBU was 7.5% of the ethylene trithiocarbonate. The best molar ratio of ethylene trithiocarbonate and ethyl cyanoacetate was 1:4. The highest conversion and yield were obtained after lh under 110℃. The gas generated in the reaction was confirmed as hydrogen sulfide. The reaction mechanism was proposed:firstly, DBU activated the ethyl cyanoacetate, then the ethyl cyanoacetate nucleophilic attacked the ethylene trithiocarbonate and formed the intermediate, finally the intermediate released hydrogen sulfide effected by DBU and produced the product meanwhile. In order to investigate the generality, reactions between different active methylene compounds and ethylene trithiocarbonate were investigated. The results showed that the reaction had good generality.In the second part of this dissertation ionic liquids were used as the catalysts to promote the reactions of ethylene trithiocarbonate and active methylene compounds. Ethylene trithiocarbonate and ethyl cyanoacetate were used as the raw materials. Some reaction conditions such as type of catalysts, reaction time, reaction temperature, catalyst amount and mole ratio of reactants were optimized. The best conversion and yield were obtained when the molar ratio of ethylene trithiocarbonate and ethyl cyanoacetate was 1:4 and the amount of catalyst 10% of BmimOAc in 1 h under 110℃. The conversion of ethylene trithiocarbonate was 93% and the yield of product reached 84%. After the reaction, the gas produced in the reaction was detected, the results showed that the gas was hydrogen sulfide. Then the 1H NMR titration data confirmed the formation of hydrogen bond between the BmimOAc and ethyl cyanoacetate. What’s more, the 1H NMR titration data also proved the hydrogen bond between ethylene trithiocarbonate and cation of the BmimOAc. On the basis of these evidences, the reaction mechanism was hypothesized. The first step was the activation of ethylene trithiocarbonate and ethyl cyanoacetate by the BmimOAc, forming the intermediate. Then the hydrogen sulfide was released under effect of the BmimOAc and the product was produced meanwhile. To investigate the activity of BmimOAc, the reactions of different active methylene compounds and ethylene trithiocarbonate were investigated. It showed that BmimOAc had good activity for different substrates.In the third part of this dissertation ionic liquids and organic base were used as catalysts for the reactions of ethylene trithiocarbonate with other nucleophilic reagents. O-phenylenediamine, pyrocatechol, ortho-aminophenol, phenyl amine and phenol were chosen as reactants to react with ethylene trithiocarbonate respectively. The results showed that pyrocatechol and phenol cannot react with ethylene trithiocarbonate when organic bases or ionic liquids were used as catalyst. Using o-phenylenediamine and ortho-aminophenol as reactants, the reactions can get sulfur carbonyl heterocyclic compounds. If using organic bases as catalysts to catalyze the reaction of phenylamine and ethylene trithiocarbonate,1,3-dithiolane derivatives can be obtained.