Mechanism of the dehydration of D-fructose to 5-hydroxymethylfurfural in dimethyl sulfoxide at 150 degrees C: an NMR study.

The anomeric composition of d-fructose in dimethyl sulfoxide changes when the solution is heated from room temperature to 150 degrees C, with a small increase in the alpha-furanose form at the expense of the beta-pyranose tautomer. Additionally, a small amount of alpha-pyranose form was also observed at 150 degrees C. A mechanism is proposed for the dehydration of D-fructose to 5-hydroxymethylfurfural in DMSO at 150 degrees C, where the solvent acts as the catalyst. A key intermediate in the reaction was identified as (4R,5R)-4-hydroxy-5-hydroxymethyl-4,5-dihydrofuran-2-carbaldehyde by using (1)H and (13)C NMR spectra of the sample during the reaction.