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

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 R-1 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.