Conversion Of 2,5-dimethylfuran Into P-Xylene With Ionic Liquids At Mild Conditions

Aromatics have played essential and unique roles in the areas ranging from synthetic chemistry to manufacturing industry,and they are mainly derived from fossil resources currently.The production of aromatics from biomass is of great fundamental interest and practical importance to ease the burden of fossil resources.However,the development of effective routes with simple steps,high selectivity and under mild conditions is still challenging.In this work,we report an original route for the one-step synthesis of aromatics from biomass derivatives catalyzed by meal triflates and acidic ionic liquids at mild conditions.When using metal triflates as the catalysts,Sc(OTf)3 and[Emim]NTf2 formed the best catalytic system for the synthesis of p-xylene from 2,5-dimethylfuran and acrylic acid under mild conditions.An overall 63%selectivity towards p-xylene and 78%selectivity towards aromatics were obtained at 90%conversion of 2,5-dimethylfuran by enhancing the dehydration and introducing an extra one-pot decarboxylation step.Furthermore,the method was also proved to be effective for using maleic anhydride as the dienophile.Since the yield of aromatics obtained in metal triflates catalyzed system was moderate,we began to use acidic ionic liquids as both solvent and catalyst for the one-step synthesis of renewable aromatics from various bio-based furanics at mild conditions.[Bmim]HSO4 can directly convert 2,5-dimethyl furan and acrylic acid into p-xylene and 2,5-dimethylbenzoic acid,up to 89%aromatic selectivity was achieved at 87%conversion of 2,5-dimethylfuran at room temperature and atmospheric pressure,and totally 84%selectivity of p-xylene can be obtained with a subsequent decarboxylation reaction.The reaction mechanism study supplemented with isotopic tracing and DFT calculations revealed the lowest-energy pathway for the two main products.Various starting materials were studied for further extensions of the method and it turned out that electron-donating methyl groups on the furan ring played crucial roles on the activation of dehydration and decarboxylation processes.These two methods have the potential to be generic approaches for the conversion of bio-based furanics into renewable aromatics and provided convenient access to industrial commodity aromatics from fully biomass derived feedstocks and thus can be regarded more economically and environmentally feasible.