Deoxygenation of biomass-derived feedstocks: oxorhenium-catalyzed deoxydehydration of sugars and sugar alcohols.

The conversion of renewable cellulosic biomass into fuels and chemicals has attracted increased attention with the growing demand for sustainability. However, one fundamental challenge is that saccharides, the major component of cellulosic biomass, are highly oxygen-rich when compared with the majority of current commodity chemicals and fuels. The polyol structure also generally presents poor solubility in organic solvents, thermal instability, and limited scope for functionalization, making its chemical manipulation difficult. Therefore, efficient deoxygenation reactions of sugars and sugar derivatives need to be developed. Current methods are dominated by the high-temperature pyrolysis, acid-catalyzed dehydration, and hydrogenolysis reactions. A much less developed deoxygenation pathway is the deoxydehydration (DODH) reaction, which removes two adjacent hydroxy groups from vicinal diols to afford alkenes (Scheme 1).