Ru-Catalyzed Enantioselective Hydrogenation of 2-Pyridyl-Substituted Alkenes and Substrate-Mediated H/D Exchange
Wei Hao1, Candice L Joe2, Sloan Ayers2
1Department of Chemistry, Scripps Research, La Jolla, CA 92037 USA.
Abstract:
A highly efficient and enantioselective asymmetric hydrogenation catalyzed by Ru-DTBM-segphos is reported for a broad range of pyridine-pyrroline tri-substituted alkenes. Kinetic, spectroscopic, and computational studies suggest that addition of H2 is rate-determining and that alkene insertion is the enantio-determining step. These studies also reveal an intriguing Ru-catalyzed H/D exchange process that is facilitated by the substrate at room temperature and low pressure where hydrogenation activity is suppressed. These studies lead to a mechanistic proposal that further defines the roles of hydrogen gas, Ru-H species, and protic solvents in this catalytic system.
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