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Diastereoselective Rhodium-Catalyzed Hydrogenation of 2‑Oxindoles and 3,4-Dihydroquinolones

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journal contribution
posted on 17.11.2020, 13:05 authored by Christian H. Schiwek, Christian Jandl, Thorsten Bach
The benzene ring of indolin-2-ones (2-oxindoles) and 3,4-dihydroquinol-2-ones was converted to a saturated cyclohexane ring by hydrogenation in the presence of the rhodium complex Cy(CAAC)­Rh­(cod)­Cl. The stereoselectivity of the process was found to be high with respect to both external substituent R1 within the saturated part of the heterocyclic ring and substituent X on the benzene ring. Twenty-one hexahydroindolin-2­(3H)-ones (70–99% yield, dr = 83/17 to >99/1) and twelve octahydro-2­(1H)-quinolinones (87–96% yield, dr = 64/36 to >99/1) were obtained with the major diastereoisomer exhibiting the hydrogen atoms in an all-cis arrangement. The high tolerance toward functional groups and the compatibility with existing stereogenic centers are key features of the hydrogenation protocol presented here.