Rhenium-Catalyzed Dehydration of Nonbenzylic and Terpene Alcohols to Olefins

With the increasing importance of research into biomass as a feedstock for the chemical industry, new methods to reduce the oxygen content of biomass are required. Here, we present our progress in the field of the dehydration reaction, using various rhenium-based catalysts, with rhenium(VII) oxide as the most active catalyst. A wide range of allylic, aliphatic, and homoallylic alcohols have been used as substrates under relatively mild conditions (100–150 °C, 0.5 mol % catalyst loading, technical toluene, ambient atmosphere) as well as various biobased terpene alcohols. Furthermore, we have applied our protocol to tea tree oil as a proof of concept for the catalytic upgrading of essential oils. The reactivity and selectivity of rhenium(VII) oxide is compared with a classical acid catalyst; sulfuric acid; and solid acid catalysts, such as acid resins, zeolites, and mesoporous materials. It was found that rhenium(VII) oxide surpasses all these catalysts in both activity and selectivity and also shows enduring activity after seven recycling runs.