Rare Earth Hydride Supported Ruthenium Catalyst for the Hydrogenation of N-heterocycles: Boosting the Activity via a New Hydrogen Transfer Path and Controlling the Stereoselectivity
Hydrogenation of N-heterocycles is of great significance for their wide range of applications such as building blocks in drugs and agrochemicals synthesis and liquid organic hydrogen carriers (LOHCs). Persuing better hydrogenation performance and stereoselectivity, we successfully developed rare earth hydride supported ruthenium catalyst Ru/YH3 for the hydrogenation of N-heterocycles, especially N-ethylcarbazole (NEC), the most promising LOHCs. Full hydrogenation of NEC on Ru/YH3 can be achieved under 363 K and 1 MPa hydrogen pressure, which is currently the lowest compared to previous reported catalysts. Furthermore, Ru/YH3 shows the biggest turnover number, namely the highest catalytic activity among the existing catalysts for hydrogenation of NEC. Most importantly, Ru/YH3 shows remarkable stereoselectivity for the all-cis products, which is much favorable for the subsequent dehydrogenation. The excellent performance of Ru/YH3 originates from the new hydrogen transfer path from H2 to NEC via YH3. Ru/LaH3 also reveals good activity for hydrogenation of NEC and Ru/YH3 also possesses good activity for hydrogenation of 2-methylindole, indicating that rare earth hydride supported catalyst is a highly effective strategy for developing better hydrogenation catalyst for N-heterocycles.