Microwave-promoted conversion of concentrated fructose into 5-hydroxymethylfurfural in ionic liquids in the absence of catalysts

Under microwave irradiation, concentrated fructose (33–92 wt%) in ionic liquids afforded 5-hydroxymethylfurfural in ca. 97–57% yields without addition of catalysts, within 3 min. In-situ13C NMR and 1H NMR spectra suggest that the transformation of fructose in ionic liquid is a highly selective reaction that proceeds predominantly via the cyclic fructofuransyl intermediate. This method is expected to be valuable in facilitating cost-effective conversion of carbohydrates into biofuels and platform chemicals.

► 5-Hydroxymethylfurfural is produced from fructose in excellent yields in ionic liquids under microwave irradiation within 3 min. ► The transformation is done without addition of catalysts. ► Fructose can be employed in high concentration up to 92 wt%. ► In-situ13C and 1H NMR spectra give mechanistic insights into the reaction.