《Table 1 Effect of catalyst on the acylation of 2-acetylfuran》

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《From Furan to High Quality Bio-based Poly(ethylene furandicarboxylate)》

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a Molar ratio of catalyst to 2-acetylfuran=1:1；b Conversion=1-（remained2-acetylfuran/charged 2-acetylfuran）；c Maximum yield of 2，5-DAF of the reaction；d Selectivity=Yield/Conversion

For the synthesis of 2，5-DAF，2-acetylfuran obtained above was further acylated by acetic anhydride via Friedel-Crafts reaction.In order to restrain the ring opening reaction of2-acetylfuran，relativelyweakacids，suchas p-toluenesulfonic acid，phosphoric acid or methanesulfonic acid，were used as the catalyst.Figure 2 shows the yields of2，5-DAF as a function of reaction time catalyzed by different catalysts.Obviously，a maximum yield of 2，5-DAF along with reaction time was observed no matter which catalyst was used.The conversion of 2-acetylfuran，the maximum yield of2，5-DAF and selectivity of this reaction using different catalysts are listed in Table 1.Undoutedly，methanesulfonic acid was the optimal catalyst for the reaction.It is known that2，5-DAF is one of the most important furan derivatives and several methods have been tried for its preparation.However，the harsh reaction conditions，including ultra low temperature（-78°C）and dangerous catalysts（such as n-Bu Li）are necessary[35].Up to now，literature information is hardly available about the synthesis of 2，5-DAF under mild conditions.In this work，the Friedel-Crafts reaction catalyzedby methanesulfonic acid was conducted at 120°C and2，5-DAF was synthesized successfully，though the yield was only about 40.2%.