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Iridium-Catalyzed Enantioselective Hydrogenation of Oxocarbenium Ions: A Case of Ionic Hydrogenation |
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| Authors: | Tilong Yang Yongjie Sun Heng Wang Prof. Dr. Zhenyang Lin Dr. Jialin Wen Prof. Dr. Xumu Zhang |
| Affiliation: | 1. Shenzhen Grubbs Institute and Department of chemistry, Southern University of Science and Technology, 1088 Xueyuan Road, Shenzhen, 518055 China Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China These authors contributed equally to this work.;2. Shenzhen Grubbs Institute and Department of chemistry, Southern University of Science and Technology, 1088 Xueyuan Road, Shenzhen, 518055 China These authors contributed equally to this work.;3. Shenzhen Grubbs Institute and Department of chemistry, Southern University of Science and Technology, 1088 Xueyuan Road, Shenzhen, 518055 China;4. Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China |
| Abstract: | Ionic hydrogenation has not been extensively explored, but is advantageous for challenging substrates such as unsaturated intermediates. Reported here is an iridium-catalyzed hydrogenation of oxocarbenium ions to afford chiral isochromans with high enantioselectivities. A variety of functionalities are compatible with this catalytic system. In the presence of a catalytic amount of the Brønsted acid HCl, an α-chloroether is generated in situ and subsequentially reduced. Kinetic studies suggest first-order kinetics in the substrate and half-order kinetics in the catalyst. A positive nonlinear effect, together with the half kinetic order, revealed a dimerization of the catalyst. Possible reaction pathways based on the monomeric iridium catalyst were proposed and DFT computational studies revealed an ionic hydrogenation pathway. Chloride abstraction and the cleavage of dihydrogen occur in the same step. |
| Keywords: | Asymmetrische Katalyse Hydrierung Iridium Ligandendesign Reaktionsmechanismen |