Expanding the Scope of Biomass-Derived Chemicals through Tandem Reactions Based on Oxorhenium-Catalyzed Deoxydehydration

摘要

With the growing demand for sustainability, cellulosic bio-mass has attracted much attention as a renewable, carbon-neutral and inexpensive feedstock for chemicals and fuels. However, the conversion of biomass faces the fundamental challenge that saccharides and their polyol derivatives, the most basic platform chemicals accessible from cellulose, are too oxygen-rich to be compatible with the current petroleum-based infrastructure. The search for efficient deoxygenation methods has resulted in rapidly growing interest in the catalytic deoxydehydration (DODH) reaction to remove two adjacent hydroxyl groups from vicinal diols to afford alkenes. Although preliminary studies on ruthenium, vanadium, molybdenum, and rhenium carbonyl catalysts (Re2(CO)_(10) or BrRe(CO)5) have been reported, most precedents of DODH employ high-valent oxorhenium catalysts in conjunction with various reductants, such as phos-phines, H2, and NaSO3. In 2012, we reported the methyltrioxorhenium (MTO)-catalyzed DODH reaction using a sacrificial alcohol (3-pentanol, 3-octanol, 1-butanol) as reductant/solvent. This system smoothly converted sugar alcohols and sugars into linear alkene products and aromatics with remarkable selectivity. Oxorhenium-catalyzed DODH of diols using glycerol or benzyl alcohol'"' as reductants were also independently reported by the Abu-Omar and Nicholas groups.