Direct conversion of readily available sucrose to 2,5-diformylfuran by low-cost sulfur and green p-toluenesulfonic acid.

Direct conversion of sucrose to value-added 2,5-diformylfuran (DFF) has received a lot of interest lately. In this report, various acids and oxidizing agents were examined for DFF production from carbohydrates. The findings showed that p-toluenesulfonic acid (pTSA) and low-cost sulfur exhibited the highest activities as a catalyst and oxidant, respectively, for the one-pot, one-step synthesis of DFF from sucrose. The first and second steps involve utilizing pTSA to convert sucrose to fructose and fructose to 5-hydroxymethylfurfural (HMF), which is then selectively oxidized to DFF using sulfur. The process was optimized by systematically screening the types of carbohydrate substrates, solvents, acid catalysts, and oxidants to identify the most suitable candidate in each category for the one-pot sucrose-to-DFF conversion. Then, various factors were screened to achieve the highest DFF yield of 72.5% at 160 °C for 10 h in the presence of pTSA and sulfur in dimethyl sulfoxide (DMSO) solvent. Experimental validation of the process at a 5-fold substrate loading also confirmed its notable capacity for scalability. DFF was also isolated and structurally characterized. A mechanism was proposed for the direct DFF synthesis via a sequence of dehydration and selective oxidation steps catalyzed by a composite system of pTSA/S/DMSO. Overall, this study highlights the use of an abundant biomass, available and low-cost catalyst and oxidant, and a short reaction time to obtain high DFF yield.