A Cp-tt-Based Trioxo-Rhenium Catalyst for the Deoxydehydration of Diols and Polyols

摘要

Trioxo-rhenium complexes are well known catalysts for the deoxydehydration (DODH) of vicinal diols (glycols). In this work, we report on the DODH of diols and biomass-derived polyols using (CpReO3)-Re-tt as a new catalyst (Cp-tt=1,3-di-tert-butylcyclopentadienyl). The DODH reaction was optimized using 2mol% of (CpReO3)-Re-tt and 3-octanol as both reductant and solvent. The (CpReO3)-Re-tt catalyst exhibits an excellent activity for biomass-derived polyols. Specifically, glycerol is almost quantitatively converted to allyl alcohol and mucic acid gives 75% of muconates at 91% conversion. In addition, the loading of (CpReO3)-Re-tt can be reduced to 0.1mol% to achieve a turn-over number as high as 900 per Re when using glycerol as substrate. Examination of DODH reaction profiles by NMR spectroscopy indicates that catalysis is related to Cp-ligand release, which raises questions on the nature of the actual catalyst.