过渡金属催化的醇类脱氧脱水反应

Transition Metal Catalyzed Deoxydehydration of Alcohols

开发和利用环境保护型的可再生新能源是缓和与解决能源环境问题的重要举措.生物质可作为燃料和可再生平台化学品的来源.高含氧量与过度官能化的生物质原料不能直接使用,因此降低生物质原料的含氧量并将其转化为燃料与增值化学品的方法是实现生物质能广泛应用的关键.还原脱氧的方法主要有热解、水解、氢解、脱羧/脱羰反应、加氢脱氧与脱氧脱水反应等.本综述详细介绍了铼、钼、钒、钌等四种过渡金属催化的由二元醇及多元醇制备相应烯烃的脱氧脱水反应,主要从均相催化、还原剂使用、机理研究和非均相催化等方面做了多角度的总结.铼催化的脱氧脱水反应具有选择性好和烯烃产率高等优点,钼、钒、钌等金属是可能替代昂贵的铼金属的催化剂.

In view of the depletion of fossil fuels, the development and utilization of environment-friendly and sustainable resources widely play an indispensable role in alleviating and resolving problems about resources and environment. Biomass could be utilized as biofuels and renewable platform chemicals. However, biomass-derived molecules are fairly oxygen-rich and hyperfunctionalized. Therefore, new synthetic routes for the regenerative production of chemicals, fuels, and energy from renewable biomass sources are currently investigated especially the routes of transforming high-oxygen-content biomassderived vicinal diols and poly vicinal alcohols into fuels and value-added chemicals. A range of reductive deoxygenation methods consisting of direct deoxygenation, pyrolysis, hydrogenolysis, decarbonylation, decarboxylation, hydrodeoxygenation, and deoxydehydration（DODH） are under investigation. In this review, we detail the recent-evolutionary and efficient strategies of transition metal-catalyzed DODH of vicinal diols into corresponding alkenes, including rhenium, molybdenum, vanadium, and ruthenium catalysts. Rhenium-catalyzed DODH reactions are very selective and active to provide high yields of olefin products, which keep important functionality in place as well as can be readily functionalized. Recent efforts in rhenium-mediated systems include the development of new rhenium catalysts, the application of cheaper and more available reductants, and growing mechanistic understandings owing to both theoretical and experimental studies. A new emerging trend within DODH is the development of heterogeneous rhenium-based catalysts which demonstrates their ability to rival and in some cases surpass their homogeneous counterparts. Furthermore, catalysts based on the transition metals molybdenum, vanadium and ruthenium show great potential as inexpensive alternatives to rhenium catalysts.