Utilization Of Bio-based Glycolaldehyde Aqueous Solution In The Synthesis Of 2,3-dihydrofurans Promoted By Deep Eutectic Solvent

Glycolaldehyde is a biomass-derived chemical compound available from cellulose or glucose.Until now,little attention has been devoted to its use towards value-added chemicals.To explore value-added transformations of glycolaldehyde,in this work,a three-component reaction of glycolaldehyde,indole and 1,3-dicarbonyl compound was developed to synthesize a class of 3-（indol-3-yl）-2,3-dihydrofurans.Using glycolaldehyde diethyl acetal as glycolaldehyde source,the reaction can be performed in organic solvents,and two catalytic systems were proved to be effective:（a）Sc（OTf）₃/nitromethane;and（b）Ni（ClO₄）₂.6H₂O/acetonitrile.However,these conditions applied to the direct use of the bio-based glycolaldehyde aqueous solution did not provide the dihydrofurans efficiently.To enable the use of the aqueous solution of glycolaldehyde,a hitherto unreported deep eutectic solvent（DES）was developed by using FeCl₃.6H₂O and meglumine（N-methylglucamine）as precursors.The FeCl₃.6H₂O/meglumine DES was characterized by FTIR,TGA and DSC,and the obtained results demonstrated unambiguously the formation of a DES.The FeCl₃.6H₂O/meglumine DES was found to be an efficient and a water-compatible promoting medium for the above mentioned three-component reaction.A variety of 3-（indol-3-yl）-2,3-dihydrofuranfurans were synthesized with the help of three catalytic systems in good yields.And the FeCl₃.6H₂O/meglumine DES system can also be recycled without significant loss of activity.